Immanuel Kant

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Immanuel Kant, the propounder of the critical philosophy, was born at Königsberg in East Prussia; he was the son of a saddler and, according to his own account, the grandson of an emigrant from Scotland. He was educated at the local high school, the Collegium Fridericianum, and then at the University of Königsberg, where he had the good fortune to encounter a first-class teacher in the philosopher Martin Knutzen. After leaving the university, about 1746, Kant was employed for a few years as a tutor in a number of families in different parts of East Prussia. He kept up his studies during this period and in 1755 was able to take his master's degree at Königsberg and to begin teaching in the university as a Privatdozent. He taught a wide variety of subjects, including physics, mathematics, and physical geography as well as philosophy, but nevertheless remained poor for many years. It was not until 1770, when he was appointed to the chair of logic and metaphysics at Königsberg, that his financial stringencies were eased.

Kant's first book, Gedanken von der wahren Schätzung der lebendigen Kräfte (Thoughts on the True Estimation of Living Forces), was published as early as 1747 (Königsberg), and between 1754 and 1770 he produced an impressive stream of essays and treatises. His earlier works are primarily contributions to natural science or natural philosophy, the most notable being his General History of Nature and Theory of the Heavens of 1755; it was not until after 1760 that philosophical interests in the modern sense became dominant in his mind. Kant's publications had already won him a considerable reputation in German learned circles by the time he obtained his professorship. The ten years following his appointment form a period of literary silence during which Kant was engaged in preparing his magnum opus, the Critique of Pure Reason. The appearance of the Critique was eagerly awaited by Kant's friends and philosophical colleagues, but when it at last came out in 1781 the general reaction was more bewilderment than admiration. Kant tried to remove misunderstandings by restating the main argument in the Prolegomena to Every Future Metaphysics of 1783 and by rewriting some of the central sections of the Critique for a second edition in 1787. At the same time he continued, with most remarkable energy for a man of his years, the elaboration of the rest of his system. By 1790 the Critique of Practical Reason and the Critique of Judgment were in print, and of the major treatises only Religion within the Bounds of Mere Reason (1793) and Metaphysic of Morals (1797) had still to appear. Kant then enjoyed a tremendous reputation throughout Germany and was beginning to be known, though scarcely to be understood, in other European countries. In his declining years, however, he suffered the mortification of seeing some of the ablest young philosophers in his own country, among them Johann Gottlieb Fichte, Friedrich von Schelling, and J. S. Beck, proclaim that he had not really understood his own philosophy and propose to remedy the deficiency by producing "transcendental" systems of their own. There is reason to believe that the work on which Kant was engaged in the last years of his life was intended as a counterblast to such critics. But Kant was not able to complete it before his death, and all that remains of it are the fragments gathered together under the title Opus Postumum.

Kant's outer life was almost entirely uneventful. He never married. The one occasion on which he might have become politically prominent was in 1794 when, after the appearance of his book on religion, the Prussian king asked him not to publish further on a topic on which his views were causing alarm to the orthodox. But Kant duly promised, and no scandal ensued. For the rest, he fulfilled the duties of his professorship and took his turn as rector of the university; dined regularly with his friends; admired Jean-Jacques Rousseau and the French Revolution from afar; conversed eagerly with travelers who brought him news of a wider world he never saw himself. Never very robust in body, he carefully conserved his physical resources and was in good health until a relatively short time before his death. He was nearly eighty when he died.

Character of Kant's Philosophical Work

Kant was the first of the major philosophers of modern times to spend his life as a professional teacher of the subject. He was required by university regulation to base his philosophy lectures on particular texts, and he used for this purpose not the works of such major thinkers as René Descartes and John Locke, but the handbooks of his professorial predecessors, notably Christian Wolff, Alexander Gottlieb Baumgarten, and G. F. Meier. Wolff and Baumgarten had dressed out the philosophy of Gottfried Wilhelm Leibniz in what they took to be decent academic garb, presenting Leibniz' thoughts in the form of a system and with an air of finality foreign to the original; Meier did the same for the doctrines of formal logic. Their example had a near-fatal effect on Kant, for he too thought that philosophy must be thorough if it is to be academically respectablemeaning, among other things, technical and schematic.

In the Critique of Pure Reason Kant set out his theories in what he later called progressive order, starting from what was logically first and working forward to familiar facts; in that work he also employed an elaborate terminology of his own and an apparatus of "parts," "divisions," and "books" whose titles are alarming and whose appropriateness to the subject matter is not immediately obvious. It is not surprising that his first readers were unable to discover what the work as a whole was about. The Critique of Practical Reason and the Critique of Judgment were still more pedantic in form, since in them Kant persisted with much of the formal framework already used in the Critique of Pure Reason, in each case proceeding from a part labeled "Analytic" to another labeled "Dialectic," uncovering one or more "antinomies" in dealing with the dialectic, and ending with an untidy appendix irrelevantly titled "Doctrine of Method." The fact that Kant was already an old man when he composed these works doubtless explains his attachment to what some commentators have called his architectonic; it is a major obstacle to the proper grasp and unprejudiced evaluation of his ideas. Yet, as passages in his ethical writings in particular show, Kant was capable of expounding his thoughts with clarity, even with eloquence. He was not by nature a bad writer, but he accepted uncritically the scholastic manner cultivated by his fellow professors.

The first task in reading Kant is thus to cut through the formal academic dress in which he clothes his opinions. When this is done, what emerges is not a provincial pedant like Wolff or Baumgarten, but a person of remarkable intellectual and moral stature. Kant's knowledge of the major European philosophers was often no more than superficial, and his estimate of the work of some of his own contemporaries was certainly overgenerous. But he had, for all that, a sure sense of what was intellectually important at the time; he alone among the eighteenth-century philosophers at once appreciated the greatness of Isaac Newton and was fully aware of the challenge for ethics Newton's work presented once its seemingly deterministic implications were understood. To sum up Kant's mature philosophy in a single formula: He wished to insist on the authority of science and yet preserve the autonomy of morals. To achieve this result was a gigantic task, involving consideration of the whole question of the possibility of metaphysics as well as the construction of a theory of scientific knowledge and the elaboration of an ethical system.

Nor was Kant one to be content with mere generalities; he sought to work out his position in detail, with many specific arguments, as well as to state a general case. But the obscurities of his language combine with the extent of his intellectual ambitions to prevent the average reader from grasping precisely what Kant was after; individual points are picked up, but the shape of the whole is not discerned. Yet to be fair to Kant the reader must see the individual views in the wide setting in which Kant saw them himself. To estimate their philosophical value without taking account of their position in the Kantian system, as many critics have tried to do, is quite indefensible.

Precritical Writings

Kant's philosophical career is commonly divided into two periods, that before 1770, usually referred to as "precritical," and that after 1770, usually referred to as "critical." The word critical comes from Kant's own description of his mature philosophy as a form of "critical idealism," an idealism, that is to say, built on the basis of a critique of the powers of reason. The precritical period of Kant's thought is interesting primarily, though not exclusively, for its anticipations of his later ideas. Kant was educated by Knutzen in the Wolff-Baumgarten version of Leibniz, and he was, like his master, an independent Leibnizian from the first, although it was many years before he made a decisive break with the Leibnizian way of thinking. The main influence operating against Leibniz in Kant's early thought was Newton, to whose work he had also been introduced by Knutzen. In the more narrowly philosophical field another independent Leibnizian, Christian August Crusius, proved an important subsidiary influence. Just when David Hume awakened Kant from his "dogmatic slumber" is uncertain, but it seems likely that Kant had moved some way in the direction of empiricism before that event took place.


How little the early Kant had learned from Hume can be seen from some of his first metaphysical essays. In the Principium Primorum Cognitionis Metaphysicae Nova Dilucidatio (Königsberg, 1755) he discoursed in effect on the subject of causality, discussing at length the relationship of the Leibnizian principle of sufficient reason to the logical principles of identity and contradiction. Kant knew at this stage, as Crusius did, that Wolff's attempt to subordinate the real to the logical was a mistake, but he had only a hazy idea of what he was later to call the synthetic nature of propositions asserting real connections. He moved a step nearer his mature view in the 1763 essay on negative quantities (Versuch, den Begriff der negativen Grössen in die Weltweisheit einzuführen, Königsberg) when he pointed out that opposition in nature is quite different from opposition in logic: Two forces acting against one another are quite unlike a proposition in which the same predicate is simultaneously affirmed and denied. But in none of his writings of the time did Kant explicitly raise the question of the sphere of application of the causal principle, as Hume did.


Kant's failure to press home his questions on causation is paralleled in his otherwise striking treatment of existence in another work published in 1763, "The Only Possible Ground of Proof of God's Existence." He began this work by declaring that even if the proposition that existence is no predicate or determination of anything seems "strange and contradictory," it is nevertheless indubitable and certain. "It is not a fully correct expression to say: 'A sea unicorn is an existent animal'; we should put it the other way round and say: 'To a certain existing sea animal there belong the predicates that I think of as collectively constituting a sea unicorn.'" On these grounds Kant rejected the Cartesian version of the Ontological Argument. But he held, even so, that an alternative conceptual proof of God's existence could be found: Nothing could be conceived as possible unless (as the point had already been put in the Nova Dilucidatio ) "whatever of reality there is in every possible notion do exist, and indeed, absolutely necessarily. Further, this complete reality must be united in a single being." There must, in other words, be a perfect being if there are to be any possibilities. Kant was to recall this proof in his derivation of the idea of the ens realissimum in the Critique of Pure Reason, but he then no longer believed that it had constitutive force. His treatment of attempts to produce causal proofs of God's existence in the Critique was also altogether more trenchant than in the precritical works, for though he saw there that the ordinary First Cause Argument was unsatisfactory, he regarded the Argument from Design as generally acceptable, even if not logically compulsive.

metaphysical propositions

Kant was more successful in another treatise written at the same period, "Untersuchungen über die Deutlichkeit der Grundsätze der natürlichen Theologie und der Moral" (On the Distinctness of the Principles of Natural Theology and Morals; 1764). The Berlin Academy had proposed the question, Are metaphysical truths generally, and the fundamental principles of natural theology and morals in particular, capable of proofs as distinct as those of geometry? If not, what is the true nature of their certainty? Kant answered by drawing a series of radical distinctions between argument in philosophy and argument in mathematics. The mathematician starts from definitions that are in effect arbitrary combinations of concepts; the philosopher must work toward definitions, not argue from them, since his business is to "analyze concepts which are given as confused." Mathematics contains few unanalyzable concepts and indemonstrable propositions; philosophy is full of them. Then too, the relationship between mathematical ideas can always be observed in concreto, whereas the philosopher, having nothing to correspond to mathematical diagrams or symbolism, necessarily works on a more abstract level. The lesson of all this might seem to be that philosophical truths are incapable of strict demonstration, but Kant did not draw this conclusion in the case of natural theology, where he held to his attempted conceptual proof, though he inclined toward it in respect to "the primary grounds of morals." In general, Kant's tendency was to say that metaphysics must be an analytic activity that should follow a method that is fundamentally Newtonian: "It is far from the time for proceeding synthetically in metaphysics; only when analysis will have helped us to distinct concepts understood in their details will synthesis be able to subsume compounded cognitions under the simplest cognitions, as in mathematics" (Critique of Practical Reason and Other Writings, Beck translation, 1949, p. 275).

Kant viewed the prospects of attaining genuine metaphysical knowledge with increasing skepticism as the 1760s went on. In the enigmatic Dreams of a Spirit-Seer of 1766 he compared the thought constructions of metaphysics to the fantasies of Swedenborg, in a manner that is scarcely flattering to either. Metaphysical contentions are groundless, since metaphysical concepts such as spirit cannot be characterized in positive terms. To survive, metaphysics must change its nature and become a science of the limits of human knowledge. Kant's skepticism about metaphysics was increased by his discovery of the antinomies, which is often dated 1769 although something like the third antinomy is to be found in the Nova Dilucidatio. Astonishingly, however, in his inaugural dissertation in 1770 he reverted in some degree to the old dogmatic conception of the subject and argued for the possibility of genuine knowledge of an intelligible world. But the main interest of the dissertation lies in its account of sensory knowledge, which prepared the way for the fundamental criticisms of metaphysical pretensions in the Critique of Pure Reason.

The Inaugural Dissertation

Kant's Latin dissertation, "On the Form and Principles of the Sensible and Intelligible Worlds," publicly defended on August 21, 1770, was his inaugural lecture as professor of logic and metaphysics at Königsberg. At least one of the themes of the dissertation, the status of the concept of space, represented a long-standing interest. As early as 1747 Kant had argued that the proposition that space has three dimensions is contingent; given a different law of the effects of different substances on one another, "an extension with other properties and dimensions would have arisen. A science of all these possible kinds of space would undoubtedly be the highest enterprise which a finite understanding could undertake in the field of geometry" ("Living Forces," Handyside translation, in Kant's Inaugural Dissertation and Early Writings on Space, p. 12). Later, however, he regarded three-dimensionality as a necessary property of space, and used its necessity as a ground for rejecting Leibniz' account of the concept. In a short essay on space published in 1768 Kant had seemed to suggest that Newton's view of space as an absolute reality was the only alternative to Leibniz, but in the dissertation he rejected both theories and widened his treatment of the question so that it covered time as well as space. Despite this extension the dissertation is best viewed as directed mainly against Leibniz.

space and time

In general, Leibniz had followed the other great rationalists in interpreting perception as a confused form of thinking. Like Descartes, he had treated the deliverances of the senses as sometimes clear but never distinct. In the dissertation Kant developed two main arguments against this position. He maintained in the first place that it could not do justice to the special character of space and time, which are not, as Leibniz supposed, systems of relations abstracted from particular situations and confusedly apprehended, but rather unique individuals of which clear knowledge is presupposed in all perceptual description. The ideas of space and time are intuitive rather than conceptual in character; moreover, they are "pure" intuitions insofar as the essential nature of their referents is known in advance of experience and not as a result of it.

space and geometry

To reinforce this point Kant brought forward his second argument, that Leibniz' theory could not account for the apodictic character of geometry. There was, Kant supposed, an essential relation between geometry and space, for geometry "contemplates the relations of space" and "does not demonstrate its universal propositions by apprehending the object through a universal concept, as is done in matters of reason, but by submitting it to the eyes as a singular intuition, as is done in matters of sense" ("Dissertation," in Kant's Inaugural Discussion and Early Writings on Space, Sec. 15 C). But if space is what Leibniz said it was and if, as Kant added, "all properties of space are borrowed only from external relations through experience," then:

geometrical axioms do not possess universality, but only that comparative universality which is acquired through induction and holds only so widely as it is observed; nor do they possess necessity, except such as depends on fixed laws of nature; nor have they any precision save such as is matter of arbitrary convention; and we might hope, as in empirical matters, some day to discover a space endowed with other primary affections, and perhaps even a rectilinear figure enclosed by two straight lines. (Sec. 15 D)

Kant's own account of space at this stage was that it "is not something objective and real, neither substance, nor accident, nor relation, but [something] subjective and ideal ; it is, as it were, a schema, issuing by a constant law from the nature of the mind, for the co-ordinating of all outer sensa whatever" (Sec. 15D). One major advantage of this subjectivist view, in Kant's eyes, was that it explains the possibility of applying geometry to the physical world. Space being a universal form of sensibility, "nothing whatsoever can be given to the senses save in conformity with the primary axioms of space and the other consequences of its nature, as expounded by geometry" (Sec. 15 E).

appearance and reality

Kant's view had another, more startling implication, namely that we cannot know things as they really are through sense perception. If space and time are contributed by the knowing mind, spatial and temporal objects will be altered in the very act of being apprehended. It follows that the world known through the sensesthe world investigated by the physical sciences and familiar in everyday experiencecan be no more than a phenomenal world. Kant was prepared to accept this conclusion in the dissertation, but he balanced it by saying that over and above this phenomenal world is another world of real objects, knowable not by the senses but by reason. Reason lacks intuitive powerswe cannot be acquainted with things as they are. But (and in this the contrast with the Dreams is at its strongest) reason possesses certain concepts of its own, among them "possibility, existence, necessity, substance, cause," by means of which it can arrive at a "symbolic cognition" of such things; that is, know some true propositions about them. The intellect, in its real as opposed to its logical use, can form the concept of a perfect being and use this both to measure the reality of other things and for moral purposes.


The doctrine of pure intellectual concepts in the dissertation is at best impressionistic and had to be completely rethought in the ten years that followed. But against this may be set Kant's positive achievements in the dissertation, seen from the point of view of his future work. First, Kant had convinced himself that there is an absolute difference between sensing and thinking, and that sense experience need not be in any way confused. Second, he had worked out the main lines, though by no means all the details, of what was to be his mature theory of space and time. Third, he had revived the old antithesis of things real and things apparent, objects of the intellect and objects of the senses, to cope with the consequences of his views about space and time; in this way he was able to show (or so he thought) that physics gives us genuine knowledge, though only of appearances, and that the task of telling us about things as they really are is reserved for metaphysics. Fourth and last, he had recognized the existence of a special class of concepts, "given through the very nature of the intellect," and had seen that these have an important bearing on the question of the possibility of metaphysics.

What Kant had not done was to pose the problem of metaphysics with all its wider implications. As in the Dreams, he treated the question whether we have any knowledge of a world of pure spirit as one that is asked primarily for its theoretical interest. It was intellectual curiosity, that is to say, which at this stage prompted Kant to inquire whether physics and metaphysics could coexist, and, if they could, what should be said of their respective objects. He retained this curiosity when he wrote the Critique of Pure Reason, but it was not by then his only motive. For he had seen by 1781 that the question of the possibility of metaphysics was important not only to the academic philosopher, but because of its bearing on the universally interesting topics of God, freedom, and immortality, to the plain man as well; that it was a matter not just of intellectual, but also of moral, concern.

Critique of Pure Reason : Theme and Preliminaries

Kant's principal task in the Critique of Pure Reason was to determine the cognitive powers of reason, to find out what it could and could not achieve in the way of knowledge. The term reason in the title was intended in its generic sense, to cover the intellect as a whole; Kant was not exclusively interested in the reason that he himself distinguished from and opposed to understanding. He was, however, particularly concerned with the capacities of "pure" reason, that is, with what reason could know when operating by itself and not in association with another faculty. Kant believed it important to answer this question for two reasons. He saw that there are spheres (mathematics, for instance) in which it is plausible to claim that pure reason is a source of important truths. He also saw that in another field, that of metaphysics, remarkable claims were advanced on reason's behalf: It was alleged that, by simply thinking, we could arrive at ultimate truth about the world, establishing thus a series of propositions whose certainty was unassailable and whose subject matter was of supreme importance. Kant, who had himself made this sort of claim in the dissertation, never doubted that what the metaphysician wants to say matters, but he did question his competence to say it. The fact that reason "precipitates itself into darkness and contradictions" once it enters this field struck him as deeply significant; the "intestine wars," the interminable disputes, of metaphysicians could only mean that their claims were pitched too high.

Nor was the scandal of metaphysicsthe fact that nothing in metaphysics could be regarded as settledof concern only to metaphysicians. By failing to make good his proofs, the metaphysician brought doubt on the acceptability of his conclusions, including such fundamental articles of belief as that God exists and that the will is free. In proposing a radical reexamination of the capacities of pure reason, Kant's ultimate motive was to safeguard such convictions by making clear that although they cannot be matters of knowledge, they can all the same be held to as matters of what he called pure rational faith.

types of judgment

In the preface to the Critique, Kant formulates his main question as "how much can understanding and reason know apart from all experience?" (A xvii). (The first edition is customarily referred to as A, the second edition as B.) In the introduction, he takes his first step toward an answer by substituting the formula "How are synthetic a priori judgments possible?" Two closely connected sets of distinctions lie behind these celebrated words. First, Kant distinguishes propositions that are a priori from all others; an a priori judgment "in being thought is thought as necessary " and is also thought "with strict universality, that is, in such a manner that no exception is allowed as possible" (B 34). A priori judgments have the twin characteristics of necessity and universality, neither of which can be found in conclusions from experience.

In holding that experience can present us with no more than contingent truths Kant echoes the views of many of his predecessors. But in his other distinction, between synthetic and analytic judgments, he shows greater originality. A judgment is analytic, he explains, if what is thought in the predicate-concept has already been thought in the subject-concept; a judgment is synthetic if this condition does not obtain. Thus, "All bodies are extended" is analytic because our idea of a body is of something that is extended or occupies space; "All bodies have weight" is synthetic because the notion of weight is not comprised in the notion of body (we learn by experience that bodies have weight). In analytic judgments, again, the connection of subject and predicate is "thought through identity"; or, as Kant puts it elsewhere in the Critique, the highest principle of all analytic judgments is the principle of contradiction. It follows from this that every analytic judgment is a priori in that it is true or false without regard to experience; every analytic judgment is either necessarily true or necessarily false, and we establish its truth or falsity by reference only to definitions of the terms it contains and to the principle of contradiction. Synthetic judgments, by contrast, require for their authentication a different sort of reference, since in their case the connection of subject and predicate terms is "thought without identity." In the case of everyday judgments of fact, for example, we need to consult experience to see whether the connection asserted actually holds.

So far Kant's distinction is simply a more elaborate version of Hume's division of propositions into those that assert relations of ideas and those that express matters of fact and existence, a version inferior to Hume's in that it is formally tied to statements of the subject-predicate form. But at this point Kant gives the distinction a fresh twist by asserting that there are judgments that are both synthetic and a priori, thus cutting across the usual classifications. Nearly all the propositions of mathematics answer this description, according to Kant; he also thinks it obvious that "natural science (physics) contains a priori synthetic judgments as principles." He gives two examples: "in all changes of the material world the quantity of matter remains unchanged; and in all communication of motion action and reaction must always be equal" (B 17). The very existence of these judgments shows that reason has special cognitive powers of its own, and so lends plausibility to the claims of metaphysicians. But before accepting the claims of metaphysicians, Kant suggests, we need to ask ourselves how (under what conditions) it is possible to assert judgments of this type in the two fields concerned. Only when this question is answered can we decide whether metaphysicians can draw support from the example of mathematics and "pure" physics. This inquiry is what Kant is concerned with in the first half of the Critique.

analytic and synthetic

The terms in which Kant states his problem seem at first sight clear, but the clarity diminishes on closer inspection. There is the criticism that he offers a dual account of the analytic-synthetic distinction, once in psychological and once in logical terms, and the criticism that reference to the principle of contradiction alone is inadequate for the logical formulation of the distinction (he should have referred to logical laws generally). Apart from these two matters, Kant's treatment is marred by a failure to offer any discussion of his key idea, "what is thought in a concept." This omission is the more remarkable because Kant in fact had views on the subject of definition, views that are hard to reconcile with his apparent assumption that every judgment is unequivocally analytic or synthetic. Elsewhere in the Critique he states that, according to the real meaning of "definition," an empirical concept "cannot be defined at all, but only made explicit" (B 755). He means that we cannot give the "real essence" (in Locke's terminology) of such a concept, but only its "nominal essence," or conventional signification, which is liable to change as knowledge increases or interests shift. If this is correct, it seems to be only by convention, or provisionally, that the judgment "All bodies are extended" is analytic and the judgment "All bodies have weight" synthetic.

Nor is Kant's other distinction, between a priori and a posteriori, as simple as he pretends. He tries to clarify it by explaining that the first class of judgments have the characteristics of necessity and universality, which serve as criteria that are "inseparable from one another." He fails to notice, however, that the necessity that belongs to synthetic a priori judgments must on his own account differ from that which characterizes analytic judgments. Analytic judgments are, or rather claim to be, logically necessaryto deny a true analytic judgment would be, if Kant is correct, to dispute the validity of the law of contradiction. But though no synthetic judgment can contravene the laws of logic, none can be true in virtue of these laws and of meanings alone. Accordingly, if any synthetic judgment is to be described as necessary, it must be necessary in some further sense.

Kant recognizes in practice that the synthetic a priori judgments he takes to be valid have their own special kind of necessity. In his own terminology, they are "transcendentally" necessary; necessary, that is to say, if we are to have the knowledge and experience we actually have. But he would have done better to acknowledge the ambiguity in his term a priori from the outset. It would also have been helpful had he given some elucidation of his statement that, when a judgment is thought with strict universality, "no exception is allowed as possible." He cannot mean that no exception is logically possible, or every a priori judgment would be analytic. But he does not, at least at this early stage, make clear what other sort of possibility he has in mind.

Transcendental Aesthetic

Kant's next step in the solution of the problem of how synthetic a priori judgments are possible is to examine the two types of case in which, in his view, we undoubtedly can make synthetic a priori judgments, and then to exhibit the bearing of his results on the possibility of metaphysical knowledge. In his short but important Prolegomena to Every Future Metaphysics he approaches these tasks directly. In the Critique itself his method is more roundabout, since he proposes there to delineate the entire cognitive powers of the mind and so to clarify the background against which synthetic a priori judgments are made. This leads him to undertake an inquiry first into the a priori elements involved in sensory knowledge (the "Transcendental Aesthetic") and then into the corresponding elements involved in thought (the "Transcendental Logic"). The sharp distinction between the senses and the intellect argued for in the dissertation is the obvious basis of this division.

a priori intuitions

It seems at first sight contradictory to say that there might be a priori elements involved in sensory knowledge. According to an old philosophical and psychological tradition, sensation is an essentially passive affair; the senses present us with data and we have no choice but to accept. Kant was quite ready to agree to this as a general account of sensation. But he was persuaded that there are some features of sensory experience that cannot be accepted as empirically given.

Kant identifies these features by a process similar to that in the dissertation: an examination of our ideas of space and time. These ideas, he argues, represent the form of experience rather than its matter; through them we structure the sensory given in the very act of sensing it. To establish this position Kant appeals to a variety of considerations.

First, he insists on the fundamental and ubiquitous character of space and time, as opposed to features like color and sound. Spatial predicates apply to whatever we know through the five senses, temporal predicates both to these and to the immediately experienced flow of our inner lives. Second, he argues that we cannot acquire the ideas of space and time by reflecting on what is empirically given. Some philosophers had said that we come by the idea of space by noticing such things as that one object is adjacent to another, and that we come by the idea of time by observing the way in which events succeed, are simultaneous with, or precede one another. Kant points out that the very description of such situations presupposes familiarity with space and time as such. For to know what is meant by saying that one thing is "next to" or "on top of" another we need to appreciate how the things in question are situated in a wider spatial framework, which in turn falls within a yet wider spatial system, until we come to the thought of space as a whole. Particular spaces are not instances of space, but limitations of it, and space is accordingly a special sort of particular. The same argument applies to time. Adding to these two points the fact that we know certain things to be necessarily true of space and time (space has only three dimensions, different times are not simultaneous but successive), Kant infers that the ideas of space and time are not only "intuitions," but "a priori intuitions."


Kant finds confirmation for his view of space and time exactly as he had in the dissertation: in the thought that this view alone can explain the possibility of pure and applied mathematics. Pure geometry is possible because we are able to "construct," or show the real possibility of, its concepts in pure intuition. An experiment conducted in imagination shows at once that a triangle is a real spatial possibility, whereas a figure bounded by two straight lines is not. Applied geometry is possible because whatever is apprehended by the senses must necessarily accord with the forms of sensibility. Kant attempts at various points in his writings to extend his doctrine of the importance of pure intuition for mathematical thinking from geometry to the other parts of mathematics, but it cannot be said that he is ever convincing on this point. His reasons for saying that "seven and five are twelve" is a synthetic proposition were sharply and properly criticized by Gottlob Frege. His account of algebra (B 745, 762) is so sketchy as to be virtually unintelligible. Kant tries to say that in algebra there is a "symbolic construction" corresponding to the "ostensive construction" of the concepts of geometry, but it is not in the least clear what this has to do with the pure intuition of either space or time.

Some critics speak as if Kant's failure to produce a satisfactory philosophy of mathematics invalidated the whole "Aesthetic," and it is true that the central point of this part of his work is destroyed if his main contentions about mathematics are rejected. Kant's explanations fall to the ground if it turns out that there is no intrinsic connection between mathematics and space and time, or if it is held that mathematical propositions are analytic, not synthetic a priori. But it does not immediately follow that the whole Kantian doctrine of space and time must be rejected, for many of his arguments on this matter are independent of his philosophy of mathematics. Nor is it decisive against him that the treatment of space and time in modern physics is very different from his; he claims to be dealing with the space and time of immediate perception.


Apart from the questions about truth, however, it is vital to appreciate the importance of the conclusions of the "Aesthetic" in the economy of the Critique of Pure Reason as a whole. The "transcendental ideality" of space and time carries with it, for Kant, the proposition that whatever we know through the senses (including "inner sense") is phenomenal; Kant's celebrated distinction between appearances and things-in-themselves has its origin, if not its justification, at this point. And the view that space and time are a priori forms of intuition is not only the model on which Kant constructed his theory of categories as concepts embodying the pure thought of an object in general; the view is carried over intact into the "Transcendental Analytic," and plays a crucial part there. To treat the theories of the "Aesthetic" as if they merely embodied a series of views that Kant had outgrown by the time he completed the Critique, as some commentators have proposed to do, is not in accord with Kant's own intentions. It is also to ignore a series of arguments that are of independent philosophical interest, and that demand careful notice from anyone writing on the philosophy of perception.

Pure Concepts of the Understanding

The main contentions of the aesthetic are to be found in the dissertation. Of the doctrine of pure intellectual concepts put forward in that inaugural lecture, on the other hand, almost nothing survives in the Critique of Pure Reason.

objective reference

In the dissertation Kant argues along two lines: First, that pure intellectual concepts are not derived from sense experience (they could not be described as "pure" if they were); and second, that they serve to give us information about things as they really are. Soon after writing this work, however, Kant realized that there was a fundamental difficulty in this position, a difficulty he stated at length in a letter to his friend Marcus Herz dated February 21, 1772. It was that of knowing how "pure" concepts could be said to determine an object of any kind. To elucidate the difficulty, Kant isolated two contrasting types of intelligence, intellectus ectypus, "which derives the data of its logical procedure from the sensuous intuition of things," and intellectus archetypus, "on whose intuition the things themselves are grounded." The concepts of the first type of intelligence, deriving as they do from objects, have a guaranteed relationship to objects. The concepts of the second type determine objects, because, in this sort of case, thinking itself brings objects into existence in the same way in which "the ideas in the Divine Mind are the archetypes of things." But the human intelligence, as described in the dissertation, answers to neither description, for some of its concepts are not empirically derived and yet none of its thinking is creative in the sense specified. The problem then arises, How can these concepts be said to have objective reference; how can we know that in using them we are thinking about anything actual? It is this problem that Kant professes to have solved in the Critique of Pure Reason. Roughly speaking, his solution is that pure concepts can be shown to determine an object if the object is phenomenal. By contrast, when an attempt is made to use them to specify characteristics of "things in general," there is no guarantee that anything significant is being said.

analytic and dialectic

The details of Kant's explanation of how pure concepts can be said to have objective reference is to be found in the lengthy section of the Critique labeled "Transcendental Logic" and divided into two main parts, "Transcendental Analytic" and "Transcendental Dialectic."

The first part contains an inventory of what at this point Kant calls pure concepts of the understanding, or categories, with an account of the function they perform in human knowledge and a series of arguments purporting to show that, in the absence of such pure concepts, objective knowledge would be impossible for human beings. In addition, the "Analytic" lists the principles that rest on these pure concepts and offers independent proofs of these principles. Transcendental analytic is said by Kant to be a "logic of truth," insofar as "no knowledge can contradict it without at once losing all content, that is, all relation to an object, and therefore all truth" (B 87). It deals, in short, with the proper use of a priori concepts, which is the use they have when they provide a framework for empirical inquiries.

Transcendental dialectic is introduced as if it were merely the negative counterpart of analyticas if its sole purpose were to expose the illusions generated when dogmatic philosophers, unaware of the sensuous conditions under which alone we can make successful use of a priori concepts, attempt to apply them outside the sphere of possible experience. In fact a large part of the section titled "Dialectic" is devoted to the exposure of metaphysical sophistries. But insofar as Kant recognizes in this part of his work the existence of a further set of intellectual operations involved in scientific inquiry, he seeks to show that the faculty of theoretical reason as well as that of the understanding has its appropriate pure employment.

judgment or belief

A good way to approach the central doctrines of the analytic is to see them as an intended answer to Hume. Kant's knowledge of Hume was limitedhe had no firsthand acquaintance with the Treatise of Human Nature but he grasped the importance of many of Hume's most challenging points. For instance, Hume had argued that "belief is more properly an act of the sensitive, than of the cogitative part of our natures " (Treatise, edited by L. A. Selby-Bigge, 1888, Book I, Part IV, Sec. 1, p. 183); in the last resort it is a matter of subjective conviction. It is one of Kant's main objects in the analytic to demonstrate that such a view cannot do justice to an all-important feature of what Hume calls belief and he calls judgment, namely, its claim to be true. When I judge that something is the case I do not merely commit myself to a certain assertion; there is a sense in which I commit all rational persons too, for I purport to state what holds objectively, that is to say for everyone. To make judgment primarily a matter of feeling, something private to an individual person, is to leave out what is most characteristic of it. Similarly, to explain thinking about matters of fact and existence in terms of the association of ideas, as Hume did, is to confuse the objective with the subjective, to put science on the level of idle reverie. Empirical thinking, to deserve its name, must proceed according to rules, and there is all the difference in the world between a rule, which cannot of its nature be private, and association, which is the connecting of ideas on a purely personal plane.

the unity of experience

There are many philosophers who would accept this criticism of Hume but would deny that empirical thinking involves not only rules, but rules that are a priori or necessary rules. To understand why Kant asserts that thinking must proceed according to necessary rules, we must explain his attitude to another of Hume's doctrines, the famous contention that "all our experimental conclusions proceed upon the supposition that the future will be conformable to the past" (Enquiry concerning Human Understanding, Sec. IV, Part II). Kant agrees with Hume that empirical knowledge involves connecting one part or element of experience with another; he agrees too that connection of this sort ("synthesis") proceeds on a principle that is neither analytically true nor empirically probable. But he refuses to follow Hume in deriving the principle from "Custom or Habit," for he sees more clearly than Hume the consequences of adopting this "sceptical solution." If it were really the case that events were as "loose and separate" as Hume supposed, not only should we be deprived of any insight into the connections of things, but we should have no unitary consciousness of any sort. For it is a necessary condition of having a unitary consciousness that we be able to relate what is happening here and now to things and events that lie outside our immediate purview; if the ability to relate is not a real possibility, then neither is unitary consciousness. What Kant calls in one place (A 113) "the thoroughgoing affinity of appearances" (the fact that appearances are capable of being connected in a single experience) thus relates closely to the ability of the observer to recognize himself as a single person with diverse experiences. In fact the relation is one of mutual implication.

It may be useful to cite Kant's explanation as he gave it in the first edition of the Critique, in a passage in which all the most characteristic ideas of the "Analytic" appear and which also illustrates Kant's persistent but nonetheless questionable tendency to move from saying that unity of consciousness means that appearances must be capable of connection to the conclusion that they must be capable of connection according to universal and necessary laws.

There can be in us no items of knowledge, no connection or unity of one item of knowledge with another, without that unity of consciousness which precedes all data of intuitions, and by relation to which representation of objects is alone possible. This pure original unchangeable consciousness I shall name transcendental apperception. This transcendental unity of apperception forms out of all possible appearances, which can stand alongside one another in one experience, a connection of all these representations according to laws. For this unity of consciousness would be impossible if the mind in knowledge of the manifold could not become conscious of the identity of function whereby it synthetically combines it in one knowledge. The original and necessary consciousness of the identity of the self is thus at the same time a consciousness of an equally necessary unity of the synthesis of all appearances according to concepts, that is, according to rules, which not only make them necessarily reproducible but also in so doing determine an object for their intuition, that is, the concept of something wherein they are necessarily interconnected. (A 107108)

role of categories

If the synthesis of appearances is to proceed in accordance with necessary laws, we must clearly operate not just with empirical but also with a priori concepts. But this must not be taken to mean that some items or features of fact can be known apart from all experience. For the role of an a priori concept is fundamentally different from that of its empirical counterpart. Categories are concepts of a higher order than empirical concepts; like the ideas of space and time, they have to do with the form of experience rather than its matter. Our possession of categories accordingly supplies no knowledge of particular things; categories are fertile only when brought to bear on empirical data. Thus, because we hold to the a priori concept of cause, we interrogate nature in a certain way; thanks to it, we refuse to believe that there could be an uncaused event. But the answers we get to our interrogation depend primarily not on the form of our questions, but on what turns up in experience. Those who accuse Kant of having believed in the material a priori have failed to understand his theory.

To summarize this part of Kant's argument: If we are to have knowledge (and it is Kant's assumption that we do), various conditions must be fulfilled. The different items that fall within our experience must be capable of being connected in a single consciousness; there can be no happenings that are genuinely loose and separate. But the connections thus demanded must be objective connectionsthey must hold not just for my consciousness, but for "consciousness in general," for everyone's. An objective connection for Kant is a connection determined by a rule, and a rule is of its nature something that claims intersubjective validity. Finally, if we are to establish the operation of empirical rules we must proceed in accordance with nonempirical rules of a higher order, rules that ensure that our different experiences are capable of connection within a single experience.


In view of the close relation Kant sees between the making of judgments and the use of a priori concepts, it is perhaps not surprising that he tries to arrive at a full list of such concepts by scrutinizing the formal properties of judgments. In this connection he invokes the doctrines of general or formal logic, a science he believed had been brought to completion at a single stroke by Aristotle. Few scholars have been convinced by this section of his argument, for it seems clear that Kant adapted the list of judgment forms to suit his list of categories, rather than deriving the categories from the judgment forms. In any case, it is not obvious how formal logic, which is a logic of consistency, can supply a clue to the content of what professes to be a logic of truth.

imagination and understanding

In the first part of the "Analytic" Kant has much to say not only about concepts, judgments, and the understanding but also about the imagination. For example, he remarks in a cryptic passage:

Synthesis in general is the mere result of the power of imagination, a blind but indispensable function in the soul, without which we should have no knowledge whatsoever, but of which we are scarcely ever conscious. To bring this synthesis to concepts is a function which belongs to understanding, and it is through this function of the understanding that we first obtain knowledge properly so called. (B 103)

The contrasting and, in places, overlapping roles of understanding and imagination are among the most puzzling features of Kant's exposition. The reason why they are both introduced is related to the fact that, in the second edition of the Critique of Pure Reason in particular, Kant was concerned with two quite distinct questions. He first asked himself what conditions have to be fulfilled if any sort of discursive consciousness is to have objective knowledge; he then went on to put the question as it relates to the human discursive consciousness, which not only intuits data passively, but does so under the particular forms of space and time. When the first question is uppermost Kant tends to speak of the understanding; when the second is to the fore, he brings in the imagination as well. The passage quoted above, typical of many, suggests that it is the business of the imagination to connect, whereas that of the understanding is to make explicit the principles on which the connecting proceeds. But in one chapter, "Schematism of the Pure Concepts of Understanding," a more satisfying account of the relationship is offered.


The problem of the chapter on what Kant called "schematism" is the central problem of the analytic: How can concepts that do not originate in experience find application in experience? At first Kant speaks as if there were no comparable difficulty in the case of concepts originating in experience, although he later makes clear that there are schemata corresponding both to empirical and to mathematical concepts. To possess the concept triangle is to know its formal definition, to be able to frame intelligible sentences containing the word triangle, and so on; to possess the schema corresponding to the concept triangle is to be able to envisage the variety of things to which the word triangle applies. Thus for Kant a schema is not an image, but a capacity to form images or (perhaps) to construct models. Pure concepts of the understanding are such that they "can never be brought into any image whatsoever" (B 181); the thought they embody, springing from the pure intellect, cannot be pictured or imagined. Yet there must be some connection between the abstract idea and the experienced world to which that idea is expected to apply; it must be possible to specify the empirical circumstances in which pure concepts of the understanding can find application. Kant thinks that for the categories this requirement is met by the fact that we can find for each of them a "transcendental schema," which is, he explains, a "transcendental determination of time." Without such a schema the categories would be devoid of "sense and significance," except in a logical (verbal) way. With it, use of the categories is clearly restricted to the range of things that fall within timemeaning, for Kant, restricted to phenomena.

The meaning of this baffling doctrine can perhaps best be grasped through Kant's examples of schemata:

The schema of substance is permanence of the real in time, that is, the representation of the real as a substrate of empirical determination of time in general. The schema of cause is the real upon which, whenever posited, something else always follows. It consists, therefore, in the succession of the manifold, in so far as that succession is subject to a rule. The schema of necessity is existence of an object at all times. (B 183184)

It emerges from these cryptic sentences that the transcendental schema is something like an empirical counterpart of the pure category. It is what the latter means when translated into phenomenal terms. In Kant's own words, the schema is "properly, only the phenomenon, or sensible concept, of an object in agreement with the category" (B 186). A category without its corresponding "sensible concept" would be a bare abstraction, virtually without significance. Insofar as he argues that schematization is the work of the imagination, Kant has found a genuine function for the imagination to perform.

analytic of principles: pure physics

In the first half of the "Analytic" Kant undertook to produce a "transcendental deduction," that is, a general proof of validity, of the categories. In the second half of the "Analytic" he gives a series of demonstrations of the synthetic a priori principles that rest on individual categories.

The categories are divided, for this and other purposes, into four groups: quantity, quality, relation, and modality. The four sets of corresponding principles are labeled axioms of intuition, anticipations of perception, analogies of experience, and postulates of empirical thought in general. Only one principle falls under each of the first two classes; the third contains a general principle and three more specific principles; the fourth contains three separate though closely connected principles. The first two classes are grouped together as "mathematical" principles; the third and fourth are described as "dynamical." Mathematical principles are said to be "immediately evident" and again to be "constitutive of their objects"; they apply directly to appearances. Dynamical principles are concerned with "the existence of such appearances and their relation to one another in respect of their existence." They are no less necessary than mathematical principles, but must be distinguished from them "in the nature of their evidence" and in that they are not "constitutive" but "regulative."

Behind this formidable façade some interesting ideas are hidden. In the first place, Kant makes stimulating though not altogether convincing remarks on the subject of proving principles of the understanding. The statement that every event has a cause carries strict necessity with it and therefore cannot be grounded on an inductive survey of empirical evidence. But equally it is not analytic, and so not open to straightforward conceptual proof. To be assured of its authenticity we consequently require a different type of argument altogether, which Kant calls a "transcendental" argument "from the possibility of experience." His idea is that only if the principles of the understanding are taken to be operative and in order can we have the type of experience we in fact have. Kant perhaps supposes that this type of proof is logically compulsive, but if so he overlooks the difficulty of setting up the original premise, of being sure that only if such-and-such were true should we have the experiences we have. But even with this defect his procedure has an immediate appeal, and is not without modern imitators.

axioms of intuition

The details of the particular arguments for the principles corresponding to the categories also deserve careful attention. The principle of axioms of intuition, that "all intuitions are extended magnitudes," is perhaps the most difficult to take seriously, since what it purports to prove has apparently already been dealt with in the "Aesthetic." Kant is once more asking questions about the application of mathematics to the world; in this section of the Critique the problem that apparently troubles him is how we know that inquiries about sizes or areas are always appropriate when we are dealing with things that occupy space. His solution is that they must be appropriate, since every such thing can be regarded as an aggregate of parts produced by the observer as he synthesizes his experiences. "I cannot represent to myself a line, however short, without drawing it in thought, that is, generating from a point all its parts one after another" (B 203).

anticipations of perception

Under the term "anticipations of perception" Kant is concerned with the question of the applicability of mathematics to sensations. What guarantee have we, he asks, that every sensation will turn out to have a determinate degree, in principle quantifiable? Might we not find, for instance, that an object is colored but with no precise depth of saturation, or a smell present in a room but with no specific magnitude? Kant attempts to rule out such possibilities by attention to the formal properties of sensations. We cannot anticipate the matter of sensation, but we can say in advance of experience that every sensation will have intensive magnitude, that is, a determinate degree, because it is possible to think of any given sensation as fading away until it is imperceptible, and conversely as being built up by continuous transitions on a scale from zero to the magnitude it has. Whatever may be the merits of this solution, there can be no doubt of the importance, and for that matter the novelty, of the question Kant asks here.

analogies of experience

The section on the analogies of experience contains ideas as significant as any in Kant's writings.

The Permanence of Substance

The principle of the first analogy is that of the permanence of substance: "in all change of appearances substance is permanent; its quantum in nature is neither increased nor diminished." To believe in the permanence of substance is to believe that, whatever happens, nothing goes completely out of existence and nothing totally new is created: All change is transformation. Kant justifies the acceptance of this presupposition (which in his view, it should be remembered, applies only to things phenomenal) by arguing that without it we could not have a unitary temporal system. Coexistence and succession make sense only against a background that abides, and since time itself cannot be perceived, that background has got to be one of permanent things. This does not mean that we can determine a priori what form the permanent will take; empirical scientists are to pronounce on that question, and their answers may obviously change from time to time. All that Kant seeks to rule out is the possibility that there might be no permanent at all. His argument is defective at a vital point here, but presumably he is saying that if things could go completely out of existence, so that it would make no sense to ask what became of them, the establishment of connections between one part of experience and another would be impossible. Experience would be (or at least might be) full of unbridgeable gaps, with the result that no one set of happenings could be integrated with another, and the unity of time would be totally destroyed.


Kant carries his argument further in his discussion of the second and third analogies, in which he argues for the necessary operation of the concepts of cause and reciprocity (causal interaction). But just as the notion of substance he justifies is very different from that held by metaphysicians, so is the Kantian concept of cause different from that of, say, Leibniz; it seems at first sight much closer to Hume's idea of a cause as an invariable antecedent. Causality for Kant as for Hume is a relation between successive events; a cause is an event that regularly precedes its effect. But whereas Hume is content to treat the occurrence of regular sequences as an ultimate and entirely contingent fact, Kant believes that without the presumption of sequences that are regular (determined by a rule) there could be no knowledge of objective succession. His reason is that we have to distinguish successions that happen only in ourselves, successions merely in our apprehension, from those that occur in the objective world and are independent of us. We can do this only if an objective sequence is defined as a sequence happening according to a rule. The objective world is a world of events the occurrence of each of which determines the precise place in time of some other event. But though events are necessarily connected in this way, we must not conclude that causal connections can be established a priori; for Kant as for Hume causal propositions are one and all synthetic and empirical. All we can know a priori is that there are such connections to be found, provided we have the skill or good fortune to discover them.

postulates of empirical thought

One way of expressing Kant's attitude to substance and causality is to say that he thinks the principle of substance licenses us to ask the question, What became of that? Whenever something happens, and that the principle of causality licenses the parallel question, What brought that about? If someone tried to say that things might go out of existence altogether, or happen for no reason at all, Kant would say that these were logical but not real possibilities. The contrast between real and logical possibility is explored by Kant in the section "The Postulates of Empirical Thought." This section contains an explanation of the notions of possibility, actuality, and necessity from the critical point of view. By "really possible" Kant means "that which agrees with the formal conditions of experience, that is, with the conditions of intuition and of concepts" (B 265). A two-sided figure enclosing a space is not really possible, though its concept is not self-contradictory, because such a figure does not accord with the formal conditions of intuition. Telepathy and precognition are not real possibilities; they "cannot be based on experience and its known laws" (B 270), presumably because their actuality would violate some principle of the understanding, although Kant fails to make the point clear. The notion of real possibility is for Kant intermediate between logical and empirical possibility. We need it and can use it only because the world we have to deal with is a world that is not independently existent, but has its being in essential relation to consciousness.

phenomena and things-in-themselves

The distinction between phenomena and things-in-themselves, insisted on in the "Aesthetic" to explain our having a priori knowledge of the properties of space and time, is invoked again in the "Analytic" to account for "pure physics." If the world we confronted were one of things-in-themselves, a priori knowledge of it, even of the very restricted sort for which Kant argues, would be quite impossible. The fact that we have such knowledgethat we possess the principles discussed aboveis taken by Kant as proof that the objects of our knowledge are phenomena or appearances. He does not mean by this, however, that they are private objects, at least insofar as they are spatial. The world we know in everyday and scientific experience is common to many observers; if not independent of consciousness as such, it is independent of particular consciousnesses. Parts of it are known only to particular experiencersmy inner life, for example, is accessible only to mebut that does not affect the general point.

Kant's acceptance of the distinction between phenomena and things-in-themselves has met with much criticism. Without the idea of the thing-in-itself, said his contemporary F. H. Jacobi, we cannot enter the world of the Critique of Pure Reason ; with it we cannot remain inside. At the end of the "Analytic" Kant tries to defend himself against criticism of this sort by arguing that though he says that the objects of experience are phenomena and is prepared to admit that the obverse of a phenomenon is a noumenon or intelligible object, he is committed to noumena only in a negative sense. Having said that the categories, one of which is existence, apply only to phenomena, he cannot with consistency hold any other view. Nor is his position at this stage as devoid of logic as some have tried to make out. After all, to describe things as phenomena he does not need to assert that there actually are things of a different kind; he needs only the idea of such things. To talk about things as they might be in themselves is no more objectionable than to speak of an intellectus archetypus, as Kant did in the letter to Herz, or of an intuitive understanding, as he constantly does in both the Critique of Pure Reason and the Critique of Judgment.

The Elimination of Dogmatic Metaphysics

At the end of the section of the Critique of Pure Reason devoted to the transcendental analytic, there is a passage that can be taken as summarizing the second stage in Kant's emancipation from Leibnizian rationalism:

The Transcendental Analytic leads to this important conclusion, that the most the understanding can achieve a priori is to anticipate the form of a possible experience in general. And since that which is not appearance cannot be an object of experience, the understanding can never transcend those limits of sensibility within which alone objects can be given to us. Its principles are merely rules for the exposition of appearances; and the proud name of an Ontology that presumptuously claims to supply, in systematic doctrinal form, synthetic a priori knowledge of things in general must, therefore, give place to the modest title of a mere Analytic of pure understanding. (B 303)

Kant thus repudiates the possibility of knowledge through pure concepts of things as they really are; in 1770 he had still clung to it. Having disposed of ontology, Kant needed to consider, to complete the negative side of his work, the tenability of the remaining parts of metaphysics (rational psychology, rational cosmology, and natural theology in Baumgarten's classification), and this he did in the section titled "Transcendental Dialectic." To complete his own alternative to rationalism he needed to clarify the status of the propositions involved in "pure practical faith." His attempt to meet this requirement is made at the very end of the Critique, especially in the chapter "The Canon of Pure Reason" (B 823ff.).


Most of the conclusions of the "Dialectic" follow directly from those of the "Analytic," though there are new points of interest. As in the "Analytic," Kant's views are expressed inside a framework that is heavily scholastic. Kant claimed that human beings have an intellectual faculty in addition to the understanding. This additional faculty is reason, and it is equipped with a set of a priori concepts of its own, technically known as ideas of reason. An idea of reason can have no object corresponding to it in sense experience, for the ambition of reason is to arrive at absolute totality in the series of conditions for the empirically given, and in this way to grasp the unconditioned that falls outside experience altogether. However, this ambition can never be realized, and the only proper function for reason in its theoretical capacity is to regulate the operations of the understanding by encouraging it to pursue the search for conditions to the maximum extent that is empirically possible.

the knowing subject

Kant's handling of the "psychological idea" at the beginning of the main part of the "Dialectic" is exceptionally brilliant. He maintains in the "Analytic" that what he there calls the "I think," or the unity of apperception, is the ultimate condition of experience, in the sense of being the logical subject of experience or the point to which all experience relates. All experience is experience for a subject; whatever thoughts or feelings I have I must be capable of recognizing as my thoughts or feelings. But the subject here referred to is not something substantial; it is merely a logical requirement, in that nothing follows about the nature of my soul or self from the fact that I say "I think." So far from being "an abiding and continuing intuition" (the sort of thing Hume vainly sought in the flow of his inner consciousness), for Kant the "representation 'I' [is] simple, and in itself completely empty we cannot even say that this is a concept, but only that it is a bare consciousness which accompanies all concepts. Through this I or he or it (the thing) which thinks, nothing further is represented than a transcendental subject of thoughts = X " (B 404). The same view is expressed in an earlier passage in the Critique, where Kant says that "in the synthetic original unity of apperception, I am conscious of, myself, not as I appear to myself, nor as I am in myself, but [I am conscious] only that I am. This representation is a thought, not an intuition " (B 157).

refutation of rational psychology

These subtleties are unknown to the exponents of rational psychology, who develop the whole of their teaching around a "single text," which is "I think." From the fact that I am the subject of all my thoughts they infer that I am a thinking substance; from the fact that the "I" of apperception is logically simple they conclude that I am, in substance, simple and not composite. The proposition that "in all the manifold of which I am conscious I am identical with myself" is taken by them as implying that I am possessed of continuing personal identity. Finally, my distinguishing my own existence as a thinking being from that of other things, including my own body, is put forward as proof that I am really distinct from such things and so could in principle exist in complete independence of them. None of these inferences is justified, for in each case a move is attempted from an analytically true premise to a synthetic conclusion. As Kant remarks, "it would, indeed, be surprising if what in other cases requires so much labour to determinenamely, what, of all that is presented in intuition, is substance, and further, whether this substance can be simple should be thus given me directly, as if by revelation, in the poorest of all representations" (B 408).

mind and body

Kant presents the doctrines of rational psychology in his own idiosyncratic way, but anyone who reflects on the theories of Descartes will see that Kant was by no means attacking men of straw. Kant's treatment of the fourth paralogism, "of Ideality," is of special interest in this connection. Descartes inferred from his cogito argument that mind and body were separate in substance, which meant that the first could exist apart from the second. Bound up with this was the view that I am immediately aware of myself as a mind, but need to infer the existence of material things, which is in principle open to doubt. A great many philosophers have subscribed to this opinion, but Kant thought he could show it to be definitively false. In order to say that my inner experiences come one before another I need to observe them against a permanent background, and this can only be a background of external objects, for there is nothing permanent in the flow of inner experience. As Kant put it in the second edition, in which he transposed the argument to the discussion of existence in connection with the postulates of empirical thought), "The mere, but empirically determined, consciousness of my own existence proves the existence of objects in space outside me " (B 275). Kant is in no sense a behaviorist; he thinks that empirical self-knowledge is to be achieved through inner sense and declares in one passage that, for empirical purposes, dualism of soul and body must be taken as correct. Yet his commitment to "empirical realism" is quite unambiguous.

the antinomies

Of the remaining parts of the "Dialectic," only the sections on the antinomies and on the existence of God can be discussed here. In the "Antinomy of Pure Reason," Kant first sets out a series of pairs of metaphysical doctrines (which he says have to do with cosmology but which are in fact of wider interest). The two doctrines in each pair seem to contradict one another directly. He then produces for each pair what he regards as watertight proofs of both sides of the case, maintaining that if we adopt the dogmatic standpoint assumed without question by the parties to the dispute, we can prove, for example, both that the world has a beginning in time and that it has no beginning in time, both that "causality in accordance with laws of nature is not the only causality" and that "everything in the world takes place solely in accordance with laws of nature." Thus Kant exhibits in systematic form the famous contradictions into which, as he notes, reason precipitates itself when it asks metaphysical questions. Kant is enormously impressed by the discovery of these contradictions, and it is regrettable only that he does not sufficiently discuss their formal character or illustrate them with genuine examples.

The only way to avoid these antinomies, in Kant's opinion, is to adopt his own (critical) point of view and recognize that the world that is the object of our knowledge is a world of appearances, existing only insofar as it is constructed; this solution enables us to dismiss both parties to the dispute in the case of the first two antinomies, and to accept the contentions of both parties in the case of the other two. If the world exists only insofar as it is constructed, it is neither finite nor infinite but indefinitely extensible and so neither has nor lacks a limit in space and time. Equally, if the world is phenomenal we have at least the idea of a world that is not phenomenal; and natural causality can apply without restriction to the first without precluding the application of a different type of causality to the second. This is admittedly only an empty hypothesis so far as theoretical reason is concerned, but Kant argues that it can be converted into something more satisfactory if we take account of the activities of practical (moral) reason.

the existence of god

The fourth antinomy is concerned with God's existence. Kant's full treatment of the subject is not in the section on the antinomies but in that headed "The Ideal of Pure Reason," the locus classicus for Kant's criticisms of speculative theology. These criticisms have proved as devastating as those he brought against rational psychology.

Speculative Proofs

There are, Kant argues, only three ways of proving God's existence on the speculative plane. First, we can proceed entirely a priori and maintain that the very idea of God is such that God could not not exist; this is the method of the Ontological Argument. Second, we can move from the bare fact that the world exists to the position that God is its ultimate cause, as in the First Cause, or Cosmological, Argument. Finally, we can base our contention on the particular constitution of the world, as in the "physicotheological proof" (the Argument from Design).

Kant argues that all three types of proof are fallacious. The Ontological Argument fails because it treats existence as if it were a "real predicate," whereas "it is not a concept of something which could be added to the concept of a thing. It is merely the positing of a thing, or of certain determinations, as existing in themselves" (B 626). The First Cause Argument fails on several counts: because it uses the category of cause without realizing that only in the schematized form is the category significant; because it assumes that the only way to avoid an actually infinite causal series in the world is to posit a first cause; finally and most important, because it presupposes the validity of the Ontological Proof, in the step which identifies the "necessary being" or First Cause with God. The Argument from Design makes all these mistakes and some of its own, for even on its own terms it proves only the existence of an architect of the universe, not of a creator, and such an architect would possess remarkable but not infinite powers.

The moral proof

In spite of Kant's criticisms of the classical arguments for God's existence, he is neither an atheist nor even a believer in the principle of credo quia impossibile. He both believes in God and holds that the belief can be rationally justified. For although speculative theology is, broadly, a tissue of errors, moral theology is perfectly possible. But the moral proof of God's existence differs from the attempted speculative proofs in at least two significant respects. First, it begins neither from a concept nor from a fact about the world, but from an immediately experienced moral situation. The moral agent feels called upon to achieve certain results, in particular to bring about a state of affairs in which happiness is proportioned to virtue, and knows that he cannot do it by his own unaided efforts; insofar as he commits himself to action he shows his belief in a moral author of the universe. Affirmation of God's existence is intimately linked with practice; it is most definitely not the result of mere speculation. Again, a proof like the First Cause Argument claims universal validity; standing as it does on purely intellectual grounds it ought, if cogent, to persuade saint and sinner alike. But the moral proof as Kant states it would not even have meaning to a man who is unconscious of moral obligations; the very word God, removed from the moral context that gives it life, is almost or quite without significance. Accordingly Kant states that the result of this proof is not objective knowledge but a species of personal conviction, embodying not logical but moral certainty. He adds that "I must not even say 'It is morally certain that there is a God ,' but 'I am morally certain'" (B 857). In other words, the belief or faith Kant proposes as a replacement for discredited metaphysical knowledge can be neither strictly communicated nor learned from another. It is something that has to be achieved by every man for himself.


Kant perhaps intended originally to make the Critique of Pure Reason the vehicle of his entire philosophy, but it was clear before he completed it that some of his views, especially those on ethics, could be only touched on there. In the years immediately following its publication he displayed exceptional energy in defending and restating the theories he had already put forth and in extending his philosophy to cover topics he had hitherto not treated, or not treated in detail. By 1788 he had not only published the second, substantially revised edition of the Critique of Pure Reason, but had laid the foundations for his ethics in his short but influential Groundwork of the Metaphysic of Morals (1785) and had undertaken a more elaborate survey of moral concepts and assumptions in the Critique of Practical Reason (1788). He had also, in passing, written his essay Metaphysical Foundations of Natural Science (1786), intended as a first step toward a projected but never completed metaphysics of nature. Two years after the Critique of Practical Reason he produced yet another substantial work, the Critique of Judgment, in which he expressed his views on, among other topics, aesthetics and teleology.

moral actions

If he had published nothing else but the Groundwork of the Metaphysic of Morals Kant would be assured a place in the history of philosophy. Difficult as it is to interpret in some of its details, this work is written with an eloquence, depth of insight, and strength of feeling that make an immediate impact on the reader and put it among the classics of the subject. Kant says that his "sole aim" in the book is "to seek out and establish the supreme principle of morality." He wishes to delineate the basic features of the situation in which moral decisions are made, and so to clarify the special character of such decisions.

The situation as he sees it is roughly as follows. Man is a creature who is half sensual, half rational. Sensuous impulses are the determining factor in many of his actions, and the role of reason in these cases is that assigned to it by Hume; it is the slave or servant of the passions. But there is an identifiable class of actions in which reason plays a different part, leading rather than following. This is the class of moral actions. Such actions have the distinguishing feature that they are undertaken not for some ulterior end, but simply because of the principle they embody.

intentions and moral judgments

The moral worth of an action, as Kant puts it (Grundlegung, 2nd ed., p. 13), lies "not in the purpose to be attained by it, but in the maxim in accordance with which it is decided upon." Whether or not I attain my ends does not depend on me alone, and my actions cannot be pronounced good or bad according to the effects they actually bring about. But I can be praised or blamed for my intentions, and I can, if I choose, make sure that the maxim or subjective principle of my action accords with the requirements of morality. To do this I have only to ask myself the simple question whether I could will that the maxim should become a universal law, governing not merely this particular action of mine, but the actions of all agents similarly circumstanced. For it is a formal property of moral as of scientific judgments, recognized in practice even by the unsophisticated, that they hold without distinction of persons; the result is that an action can be permissible for me only if it is permissible for anyone in my situation.

practical reason

There are difficulties in this position of which Kant seems to have been unaware. In particular, he never asks how I am to decide what is the correct description, and hence the maxim, of my act or proposed act. Nor is it obvious how the theory shows the falsity of Hume's view that "reason alone can never be a motive to any action of the will"how it can be shown, in Kant's language, that pure reason really is practical. The practical effectiveness of reason is manifested not in the capacity to reflect, which both Kant and Hume allow, but in the power to originate or inhibit action. Kant obviously thinks that the facts of temptation and resistance to temptation, which he sees as ubiquitous in the moral life, have a clear bearing on the question whether reason really has such a power. Recognition that I ought to follow a certain course of action, whether I want to or not, and that anything that is morally obligatory must also be practically possible, is enough in his view to show that I am not necessarily at the mercy of my desires. In favorable cases, at any rate (Kant pays too little attention to the factors that diminish and sometimes demolish responsibility), I am free to resist my sensuous impulses and to determine my actions by rational considerations alone.

consequences of the moral law

Some commentators have seen Kant as an ethical intuitionist, but this view is clearly mistaken. His "practical reason" is not the faculty of insight into the content of the moral law; it is rather the capacity to act. In determining what the moral law commands, I have initially no other resources at my disposal than the reflection that it must be applied impartially. But in practice this criterion carries others with it. If the moral law applies without distinction of persons, Kant believes it follows that I must treat all human beings as equally entitled to rights under it, and that therefore I must regard them as ends in themselves and never as merely means to my own ends. Further, once I recognize that other people are morally in the same position as I am myself, and that we belong to the same moral community, I recognize both that I can legitimately pursue those of my purposes that do not conflict with the moral law and that I also have a duty to facilitate the like pursuit on the part of my fellows. So though Kant is a formalist in his view of moral reason (as in his view of the theoretical intellect), he sees his ethics as having practical consequences of the first importance. He sets these consequences out in his lectures on ethics and develops them in detail later in his 1797 Metaphysic of Morals. To judge him by the Groundwork alone, or even by the Groundwork and the Critique of Practical Reason taken together, is to do less than justice to the scope of his ethical reflection.

moral imperatives

Previous moral philosophies, Kant writes, whether they put their stress on moral sense or on moral reason, have all been vitiated by a failure to recognize the principle of the autonomy of the will. Utilitarianism, for instance, is a heteronomous ethical theory because, according to its supporters, the point of a moral action is to promote an end or purpose beyond the action, the greatest happiness of the greatest number. Kant is not unaware of the importance of ends and purposes in actions: In the Critique of Practical Reason he corrects the one-sidedness of the Groundwork by discoursing at length on the concept of "good" as well as on that of "duty." But he holds, even so, that consideration of ends cannot be of primary importance for the moral agent, since a moral action is one that is commanded for its own sake, not with a view to some purpose it is expected to bring about. The imperatives of morality command categorically, unlike those of skill or prudence, which have only hypothetical force. A rule of skill or a counsel of prudence bids us take certain steps if we wish to attain a certain endgood health or overall happiness, for example. There is no "if" about a command of morality; it bids me act in a certain way whether I want to or not, and without regard to any result the action may bring about. It represents a course of conduct as unconditionally necessary, not just necessary because it conduces to a certain end.

freedom and necessity

The concepts of duty, the categorical imperative, the moral law, and the realm of ends (in which we are all at once subjects and lawgivers) are intended by Kant to illuminate the moral situation. But even when we know what that situation is, there are many features of it that remain mysterious. Morality as Kant expounds it involves autonomy of the will, and such autonomy clearly makes no sense except on the supposition of freedom. But how we can think of the will as free and at the same time regard ourselves as subject to the moral law, that is, as under obligation, has still to be explained. To throw light on this question, Kant invokes the concept of the two worlds, the sensible and the intelligible, to which he made appeal in the Critique of Pure Reason. Insofar as I exercise the faculty of reason I have to regard myself as belonging to the intelligible world; insofar as I exercise my "lower" faculties I am part of the world of nature, which is known through the senses. Were I a purely rational being, possessed of what Kant sometimes calls a "holy will," all my actions would be in perfect conformity with the principle of autonomy, and the notions of obligation and the moral law would have no meaning for me. They would similarly have no meaning if I were a purely sensuous being, for then everything I did would occur according to natural necessity, and there would be no sense in thinking that things ought to be otherwise. The peculiarities of the human moral situation arise from the fact that men are, or rather must think of themselves as being, at once intelligible and sensible. Because I regard myself as belonging to the intelligible order, I see myself as "under laws which, being independent of nature, are not empirical but have their ground in reason alone" (Critique of Practical Reason, p. 109). But I am also a natural being, and those laws therefore present themselves to me in the form of commands that I acknowledge as absolute because I recognize that the intelligible world is the ground of the sensible. We can thus see "how a categorical imperative is possible."

What we cannot see, if Kant is to be believed, is how freedom is possible. "All men think of themselves as having a free will. Moreover, for purposes of action the footpath of freedom is the only one on which we can make use of reason in our conduct. Hence to argue freedom away is as impossible for the most abstruse philosophy as it is for the most ordinary human reason" (Critique of Practical Reason, p. 113115). Yet freedom remains what it is in the Critique of Pure Reason, "only an idea whose objective reality is in itself questionable," and there is a prima facie clash between the claim to freedom and the knowledge that everything in nature is determined by natural necessity. Kant seeks to dissolve the antinomy of freedom and necessity by means of two expedients. First, he insists that the idea of freedom required for morals is not a theoretical but a practical idea. Freedom does not need to be established as a metaphysical fact; it is enough that we find it necessary to act on the assumption that freedom is real, since "every being who cannot act except under the idea of freedom is by this alonefrom the practical point of viewreally free" (p. 100). The status of the proposition that the will is free is identical with that of the proposition that there is a God. Both are postulates of practical reasonbeliefs that we "inevitably" accept; but they are emphatically not items of knowledge in the strict sense of that term. Second, Kant sees no difficulty in our accepting the postulate of freedom, because there is no contradiction in thinking of the will as free. As an object of theoretical scrutiny I must regard myself as a phenomenon; as a moral agent possessed of a will I transfer myself to the intelligible world of noumena. I can be at once under necessity qua phenomenon and free qua noumenon. But the question of how I can be free leads to the extreme limits of practical philosophy. Freedom cannot be explained, for we lack all insight into the intelligible world; the most we can do is make clear why it cannot be explained. The critical philosophy purports to have performed this task.

epistemology and ethics

Kant advocates a form of nonnaturalist theory in ethics. But neither his ethics nor his theory of knowledge can be fully understood in isolation one from the other. The two together constitute an overall theory that is not so much a metaphysics as a substitute for a metaphysics: A theory that argues that human insight is strictly limited, but urges that, so far from being regrettable, this testifies to "the wise adaptation of man's cognitive faculties to his practical vocation" (Critique of Practical Reason and Other Writings, Beck translation, 1949, p. 247). If we knew more, we might indeed do as we ought, for "God and eternity in their awful majesty would stand unceasingly before our eyes," but we should not then do things as a matter of duty, but rather out of fear or hope. And thus the world would be poorer, for we should lose the opportunity to manifest "good will," the only thing in the world, "or even out of it, which can be taken as good without qualification."

The Critique of Judgment

None of Kant's other writings is as forceful or original as the first two Critiques and the Groundwork. The Critique of Judgment contains some fresh ideas of remarkable power, but it constitutes a series of appendixes or addenda to Kant's earlier work rather than something wholly new. It should really be seen as three or four separate essays whose connecting link is the concept of purpose.

system of science

The first essay, the introduction, begins with a pedantic discussion of the status of the power of judgment. It then takes up a problem aired in the appendix to the "Dialectic" in the Critique of Pure Reason the problem of the special assumptions involved in the belief that we can construct a system of scientific laws. If we are to have such a system, Kant argues, we must proceed on the principle that nature is "formally purposive" in respect of empirical laws; that nature is such that we can make sense of it not merely in general, but also in detail. Kant's object is to show that this principle is not a constitutive principle of things, but simply a subjective maxim of judgment.

In the Critique of Pure Reason (B 670ff.) Kant argues for what he calls the regulative employment of the ideas of reason: the use of ideas to order empirical inquiries in such a way that we try at once to find greater and greater diversity of form in the material before us and to group different species and subspecies together under ever higher genera. In actual practice we assume that nature will display the unity-in-diversity required for this program to be carried out, but we cannot prove that it will do so as we can prove that whatever falls within experience will conform to the categories. Hence we are concerned not with objective rules, but only with maxims, defined in this connection as "subjective principles which are derived, not from the constitution of an object but from the interest of reason in respect of a certain possible perfection of the knowledge of the object" (B 694).

In the Critique of Pure Reason Kant ascribes these maxims to reason. In the Critique of Judgment, he assigns them to judgment, in effect the identical doctrine. The difference is accounted for by two facts. First, by the time Kant wrote the Critique of Judgment, the term reason suggested to him nothing but practical reason. Second, he had come to think that if the power of judgment is genuinely separate from understanding on the one hand and reason on the other it must have a priori principles of its own. A division within the power of judgment itself, into determinant and reflective activities, had helped to make this last point plausible, at least in the eyes of its author.


The "Critique of Aesthetic Judgment," the first major division of the Critique of Judgment, uses the term aesthetic in what has become its modern sense. The discussion is Kant's contribution to the controversies initiated by Lord Shaftesbury and Francis Hutcheson when they made both moral and aesthetic judgments matters of feeling; Kant rejects this view and also explains why he yet cannot approve of Baumgarten's attempt to "bring the critical treatment of the beautiful under rational principles, and so to raise its rules to the rank of a science" (B 35, note a ). Kant needs to show, for the purposes of his general philosophy, that aesthetic judgments are essentially different from moral judgments on the one hand and scientific judgments on the other. This need apart, he had a long-standing independent interest in the subject; in 1764, thirty years before the Critique of Judgment, he published an essay on the beautiful and the sublime (Beobachtung über das Gefühl des Schönen und Erhabenen, Königsberg). Such an interest may seem surprising in view of the obvious limitations of Kant's own aesthetic experience; he had some feeling for literature, especially for satire, but little or no real knowledge of either painting or music. But what he has in mind in discussing the beautiful is the beauty of nature as much as anything, and his main interest is not in making aesthetic judgments, but in deciding on their logical status.

Judgments of taste, as Kant calls them, are peculiar in that they not only rest on feeling but also claim universal validity. That they rest on feeling seems to him obvious: When I ascribe beauty to an object or scene I do so not because I have observed some special character in it, but because contemplation of its form gives me immediate delight. But it is an entirely disinterested form of delight, quite different from that we feel concerning things that are agreeable, or even things that are good. When we take pleasure in something beautiful we are not desiring to possess it, or indeed taking up any attitude toward its existence. The fact that aesthetic delight is disinterested allows us to think of it as universally shared:

Since the delight is not based on any inclination of the subject (or any other deliberate interest), but the Subject feels himself completely free in respect to the liking which he accords to the object, he can find as reason for his delight no personal conditions to which his own subjective self might alone be party. Hence he must regard it as resting on what he may also presuppose in every other person; and therefore he must believe that he has reason for demanding a similar delight from every one. (Critique of Judgment, Meredith translation, Sec. 6)

Because they claim universal validity, judgments of taste appear to rest on concepts, but to think that they do is a mistake. The universality attaching to judgments of taste is not objective but subjective; to explain it we must refer to "nothing else than the mental state present in the free play of imagination and understanding (so far as these are in mutual accord, as is requisite for cognition in general )" (Sec. 9). As in the Critique of Pure Reason, Kant argues that both imagination and understanding are involved in the apprehension of any spatiotemporal object but that when we simply contemplate any such object aesthetically, no definite concept is adduced; and so the two faculties are in free play. It is the harmony between the faculties in any act of aesthetic contemplation that Kant takes to be universally communicable, and believes to be the basis for the pleasure we feel.

In addition to analyzing judgments about the beautiful, Kant devoted considerable attention in the Critique of Judgment to another concept which figured prominently in the aesthetics of his day, that of the sublime. Burke and others had given what was in effect a psychological description of the conditions in which we judge, say, the sight of a mountain range or a storm at sea to be sublime. Kant was all the more anxious to specify more exactly the meaning of such judgments and to establish their transcendental conditions because he was convinced that we here also have to do with a feeling that is held to be universally communicable. The feeling for the sublime, as he explained it, is connected not with the understanding, as is that for the beautiful, but with reason. To put his view somewhat crudely, we are at first abashed by the formlessness of some parts of nature, only to be elevated when we reflect on the utter inadequacy of these objects to measure up to our own ideas, and in particular to our moral ideas. Thus the sublime is not, as might at first sight be supposed, a quality which inheres in natural objects, but a feeling which the contemplation of natural objects provokes in us. It could have no existence for a being totally lacking in culture (a savage might feel fear on observing "thunderclouds piled up the vault of heaven," to use one of Kant's own examples, but could not recognize their sublimity), yet it is not a mere product of culture or social convention. "Rather is it in human nature that its foundations are laid, and, in fact, in that which, at once with common understanding, we may expect everyone to possess and may require of him, namely, a native capacity for the feeling for (practical) ideas, that is, for moral feeling" (Sec. 29).


One of Kant's motives for wanting to avoid making beauty an objective characteristic was that he thought such a view would lend force to the Argument from Design, and so encourage the revival of speculative theology. If things could be said to possess beauty in the same sort of way in which they possess weight, it would be a short step to talking about the Great Artificer who made them to delight us. Arguments of the same general kind were still more vividly present to his mind when he came to write the second main section of the Critique of Judgment, the "Critique of Teleological Judgment." Indeed, he ended the book with a lengthy section that underlines yet again the shortcomings of "physicotheology" and points up the merits of "ethicotheology."

Before confronting theology directly, Kant embarked on a detailed and penetrating discussion of the nature and use of teleological concepts. The existence of organic bodies, he argues, is something for which we cannot account satisfactorily by the mechanical principles sanctioned by the physical sciences; to deal with organic bodies we must employ a distinct principle, the principle of teleology, which can do justice to the fact that "an organized natural product is one in which every part is reciprocally both means and end " (Sec. 66). Such a principle cannot be used for cognitive purposes in the strict sense; it can be employed only by reflective judgment to guide "our investigation of [organic bodies] by a remote analogy with our own causality according to ends generally, and as a basis for reflection upon their supreme source" (Sec. 65). Teleology is a concept that occupies an uneasy intermediate position between natural science and theology. We cannot help using it to describe the world about us, yet we cannot assign to it full scientific status. Kant mitigates the austerities of this position by suggesting in his section "The Antinomy of Judgment" that in the end the mechanical and teleological principles stand on the same level, both belonging to reflective judgment. But it is hard to see how this can be made consistent with the doctrines of the Critique of Pure Reason, which ascribes constitutive force to the concepts of "pure physics," or even with the distinction in the Critique of Judgment itself between explaining something and merely "making an estimate" of it. We use the categories to explain, but can employ teleological concepts only for the purpose of making an estimate. Kant's underlying attitude to the whole question is revealed most clearly in the passage at the end of Sec. 68 of the Critique of Judgment, where he asks why teleology "does not form a special part of theoretical natural science, but is relegated to theology by way of a propaedeutic or transition." He answers:

This is done in order to keep the study of the mechanical aspect of nature in close adherence to what we are able so to subject to our observation or experiment that we could ourselves produce it like nature, or at least produce it according to similar laws. For we have complete insight only into what we can make and accomplish according to our conceptions. But to effect by means of art a presentation similar to organization, as an intrinsic end of nature, infinitely surpasses all our powers. (Meredith translation)

It would be interesting to know if Kant would say the same were he alive today.

Other Philosophical Writings

After publishing the three Critiques Kant was sixty-six when the Critique of Judgment appearedhe continued to publish essays and treatises on a wide variety of philosophical subjects. Most of these are in fact contributions to applied philosophy, for he took the view that scientific inquiries and practical activities alike stand in need of philosophical foundations. In many cases he attempts to supply these foundations by means of the principles established in his main workshence the general shape of his philosophies of science and religion, and of his political philosophy. It would, however, be wrong to see these as no more than mechanical applications of general Kantian conclusions. For although Kant was deeply and indeed unduly devoted to system, he also had a wide and in some cases penetrating knowledge of many different branches of learning and human activity, and there are few philosophical topics that he touches without illuminating; in fact, Kant gave the names still in use to most of the branches of applied philosophy he took up.

philosophy of nature

In the preface to his Metaphysical Foundations of Natural Science, Kant argues that the very concept of scientific knowledge is such that we can use the term properly only when dealing with truths that are both apodictically certain and systematically connected. A discipline that is thoroughly and entirely empirical cannot comply with these requirements; hence Kant pronounces chemistry to be no better than "systematic art or experimental doctrine." But the situation is different in physics. Although Kant was as firmly persuaded as any empiricist that detailed knowledge of the physical world could be arrived at only by observation and experiment, he was also sure that physics has an unshakable a priori basis that makes it worthy of the name of science. It owes this, in Kant's judgment, to the fact that its fundamental concepts are capable of mathematical expression, as those of chemistry are not, and to the close connection of these concepts with the categories, the basic concepts of rational thought.

The main object of the Metaphysical Foundations is to demonstrate the second of these points by means of an examination of the idea of matter. Starting from what professes to be an empirically derived definition of matter, "that which is capable of movement in space," Kant proceeds to a deduction of its main properties in the light of the table of categories. The result is, in effect, a rereading or reinterpretation of then-current physical theory in which all the main doctrines of Newton find their place, but which is distinctive in that the atomism professed by many physicists of the day is rejected in favor of a dynamical theory of matter resembling that of Leibniz. Kant argues in the Critique of Pure Reason that only mistaken metaphysics leads scientists to think they must accept the notions of absolutely homogeneous matter and absolutely empty space. In the Metaphysical Foundations he works out an alternative conception of matter in terms of moving forces, omnipresent but varying in degree, and puts it forward as both theoretically satisfactory and consistent with the empirical findings.

It is difficult not to see in these views the beginnings of Naturphilosophie as it was to be practiced by Schelling and G. W. F. Hegel, the more so if we read the Metaphysical Foundations in the light of Kant's further treatment of the subject in the notes published as Opus Postumum. But in 1786 at any rate Kant was still far from committing the extravagances of the speculative philosophers of nature. For one thing, he was both more knowledgeable about and more respectful of the actual achievements of physical scientists than were his romantic successors, doubtless because, unlike them, he was something of a physical scientist himself. For another, the lesson he drew from his 1786 inquiries was not how much physical knowledge we can arrive at by the use of pure reason, but how little. To establish the metaphysical foundations of natural science was a useful task, but it was in no sense a substitute for empirical investigation. Despite these differences from Naturphilosophie, it must be allowed that Metaphysical Foundations testifies, in name as well as in content, to the extent of Kant's commitment to rationalism (his theory of science could scarcely be further from Hume's) and to the way in which he was at least tempted by the constructivism favored by some of his younger contemporaries.

philosophy of history

Although Kant was quite unaware of the problems about historical knowledge and explanation with which philosophers since Wilhelm Dilthey have dealt, he made an important and characteristic contribution to speculative philosophy of history in his essay "Idee zu einer allgemeinen Geschichte in Weltbürgerlicher Absicht" (Idea of a Universal History from a Cosmopolitan Point of View; Berliner Monatsschrift, November 1784, 386410). Observing that the actions of men, when looked at individually, add up to nothing significant, he suggests that nature or providence may be pursuing through these actions a long-term plan of which the agents are unaware. To see what the plan may be we have to reflect on two points: First, that nature would scarcely have implanted capacities in human beings if she had not meant them to be developed, and second, that many human intellectual capacities (for example, the talent for invention) are such that they cannot be satisfactorily developed in the lifetime of a single individual.

The development of such capacities belongs to the history of the species as a whole. Kant suggests that the hidden plan of nature in history may well be to provide conditions in which such capacities are more and more developed, so that men move from barbarism to culture and thus convert "a social union originating in pathological needs into a moral whole." The mechanism of the process lies in what Kant calls the "unsocial sociability" of human beingsthe fact that they need each other's society and help and are nevertheless by nature individualists and egotistswhich ensures that men develop their talents to the maximum extent, if only to get the better of their fellows, and at the same time necessitates man's eventually arriving at a form of civil society that allows for peaceful rivalry under a strict rule of law. But such a "republican" constitution would be of no value unless it had its counterpart in the international sphere, for the struggles of individuals against one another are paralleled by the struggles of states. We must accordingly conclude that the final purpose of nature in history is to produce an international society consisting of a league of nations, in which war is outlawed and the way is finally clear for peaceful competition between individuals and nations.

The difficulty with this as with other lines of Kant's thought is to understand its relation to empirical inquiries. From what Kant says it seems clear that he intended "philosophical" history to be an alternative to history of the everyday kind, not a substitute for it. Nor did he pretend to be writing philosophical history himself; his essay merely puts forward the idea of or offers a "clue" to, such a history, leaving it to nature to produce someone really capable of making sense of the historical facts as Johannes Kepler and Newton made sense of physical facts. It is difficult to see, even so, how Kant could have possessed the idea of history as meaningful without knowing the facts, or alternatively how he could know that the idea throws light on the facts when it was discovered without any reference to them.

philosophy of law and politics

Kant's views about law and politics, like his philosophy of history, are obviously tied up with his ethics. Kant holds that legal obligations are a subspecies of moral obligation; thus the rational will, and neither force nor the commands of God, is the basis of the law. His standpoint in philosophy of law is thus broadly liberal, though his attitude on many particular legal issues is far from liberal as the term is now understood. He holds, for instance, that if one of the partners to a marriage runs away or takes another partner, "the other is entitled, at any time, and incontestably, to bring such a one back to the former relation, as if that person were a thing" (Metaphysic of Morals, Sec. 25). He is notorious as a strong supporter of the retributive theory of punishment and an uncompromising advocate of the death penalty for murder. The explanation of his harshness in these matters is to be found in his legalistic approach to ethics, which leaves little room for sympathy or forgiveness.

In politics also Kant combines a fundamentally liberal attitude with specific views that are conservative, if not reactionary. Following Rousseau, he attempts to explain political authority partly in terms of the general will and partly in terms of the original contract. Insofar as he insists on the contract, which he interprets not as a historical fact but as a regulative idea, he is advocating a version of political liberalism which lays particular emphasis on the rule of law; insofar as he grounds supreme political authority in the will of the people as a whole, he is obviously flirting with more radical doctrinesfrom whose consequences he is quick to draw back. An admirer of the French Revolution, he nevertheless denies that the subjects of the most ill-governed states have any right of rebellion against their rulers. And though the mixed constitution he favors is one in which citizens can make their voices heard through their representatives, he is for confining the franchise to persons who possess "independence or self-sufficiency," thus excluding from "active" citizenship (according to Sec. 46 of the Metaphysic of Morals ) apprentices, servants, woodcutters, plowmen, and, surprisingly, resident tutors, as well as "all women." The truth is, however, that Kant's political theorizing was done in a vacuum; in his day there was no real chance for a Prussian professor of philosophy to influence political events.

philosophy of religion

In the sphere of religion the views of a professor of philosophy could be influential, and Kant's views on this subject were certainly provocative. He treats religion as essentially, if not quite exclusively, a matter of purity of heartthus dispensing with speculative theology altogether and assigning a meager importance to the institutional side of religion. To adopt the religious attitude, as Kant sees it, is to look on duties as if they were divine commands. But this, he explains, is only to insist on the unconditioned character, the ineluctability, of moral obligation; it is a way of representing morality, not a way of going beyond it. Knowledge of the supersensible, as Kant thought he had shown in the Critique of Pure Reason, is impossible; and although moral practice carries with it belief in God and a future life, the whole meaning and force of that belief is to be found in a persistence in moral endeavor and a determination to repair moral shortcomings. The pure religion of morality needs no dogma apart from these two fundamental articles of belief, which are accessible immediately to the simplest intelligence. Still less has it any need of the external trappings of religionpriests, ceremonies, and the likealthough the body of believers must think of themselves as belonging to a church, universal but invisible, and the practices of visible churches sometimes serve to stimulate or strengthen moral effort, in a way which is useful but not indispensable.

The religion of morality is on this account a religion of all good men. Despite this, Kant took a particular interest in Christianity, which he saw as at least approximating true religion though corrupted by the presence of extraneous elements derived from Judaism. His book Religion within the Bounds of Mere Reason (1793) is in effect a commentary on and a reinterpretation of Christian doctrine and practice, written with the object of making this conclusion clear. In this reinterpretation the doctrine of original sin is transformed into a doctrine of the radical evil in human nature, which is the positive source of moral failing; and that of the Incarnation is replaced by an account of the triumph of the good principle over the bad, the part of the historical Jesus being taken by an idea of reason, that of man in his moral perfection. Kant sets aside the historical elements in Christianity as having no importance in themselves: Whatever is true in the religion must be derivable from moral reason. To think of the uttering of religious formulas or the performance of formal services to God as having a value of their own is to fall into the grossest superstition. It is perhaps scarcely surprising that these sentiments, whose attraction for youth can be seen in Hegel's Jugendschriften, should have struck the Prussian authorities as subversive and led the orthodox King Frederick William II to demand that Kant refrain from further pronouncements on religion. Though Kant, in his letter acceding to this demand, protested that he had no thought of criticizing Christianity in writing his book, it is hard to take his protest quite seriously, for he had certainly meant to suggest that many of the beliefs and actions of practicing Christians were without value, if not positively immoral. Indeed, the originality and continuing interest of his work on religion connect directly with that fact.

the opus postumum

In the last years of his lifefrom about 1795 onKant was engaged in the composition of what would have been a substantial philosophical work; the preparatory notes for it have been published as Opus Postumum. Its original title was "Transition from Metaphysical Foundations of Natural Science to Physics," and in its original form its object was to carry further the process, begun in 1786 in the Metaphysical Foundations of Natural Science, of finding an a priori basis for physics. No longer content with the formal structure for which he had argued earlier, Kant thought he had to show that some of the particular laws of nature could be known in advance of experience. The broadest types of physical possibility were determined by the constitution of the human mind; it was this, for example, which explained the presence in nature of just so many fundamental forces, and even of an omnipresent ether.

These speculations about the foundations of physics led Kant to epistemological considerations of a wider kind. The whole subject of the relation of the form of experience to its matter, with the question how far the form shapes the matter, arose in his mind anew, doubtless because of the criticisms directed against the formalist position of the Critique of Pure Reason by self-professed disciples such as Fichte. In 1799 Kant dissociated himself publicly from the views expressed in Fichte's Wissenschaftslehre, according to which the subject of knowledge "posits" the objective world and so, in a way, creates nature. Yet the evidence of the Opus Postumum is that at this time, or shortly thereafter, Kant was toying with similar ideas and was even using some of the same vocabulary. It is perhaps fortunate for Kant's reputation that he was not able to get his final philosophical thoughts into publishable form.

See also Aesthetic Judgment; Appearance and Reality; Aristotle; Baumgarten, Alexander Gottlieb; Beck, Jakob Sigismund; Burke, Edmund; Causation; Cosmological Argument for the Existence of God; Crusius, Christian August; Descartes, René; Determinism and Freedom; Dilthey, Wilhelm; Ethics, History of; Fichte, Johann Gottlieb; Geometry; Hegel, Georg Wilhelm Friedrich; History and Historiography of Philosophy; Hume, David; Intuition; Jacobi, Friedrich Heinrich; Kepler, Johannes; Knutzen, Martin; Leibniz, Gottfried Wilhelm; Locke, John; Logic, History of; Meier, Georg Friedrich; Newton, Isaac; Ontological Argument for the Existence of God; Perception; Propositions; Reason; Rousseau, Jean-Jacques; Schelling, Friedrich Wilhelm Joseph von; Space; Teleology; Time; Wolff, Christian.


works by kant

Collected Works

Gesammelte Schriften. 23 vols., edited under the supervision of the Berlin Academy of Sciences. Berlin: Reimer, 19021955. The standard collected edition of Kant's writings; contains his correspondence and hitherto unpublished notes (including those for the Opus Postumum ) as well as everything he published. Further volumes covering Kant's lectures are in preparation.

Kants Werke. 10 vols, edited by Ernst Cassirer. Berlin: Cassirer, 19121922. Contains the published works, with full indications of the contents of the original editions.

Philosophische Bibliothek series. Leipzig and Hamburg, 1904. Separately bound editions of all the treatises listed below under the head "Main Treatises," with useful introductions; also includes Kleinere Schriften zur Geschichtsphilosophie, Ethik, und Politik.

Main Treatises

Allgemeine Naturgeschichte und Theorie des Himmels. Königsberg and Leipzig, 1755. English translation by W. Hastie in Kant's Cosmogony (Glasgow, 1900).

Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes. Königsberg, 1763. No serviceable translation.

Träume eines Geistersehers, erläutert durch Träume der Metaphysik. Königsberg, 1766. Translated by E. F. Goerwitz into English as Dreams of Spirit-Seer (New York, 1900).

De Mundi Sensibilis atque Intelligibilis Forma et Principiis Dissertatio. Königsberg, 1770. Translated into English in Handyside's Kant's Inaugural Dissertation and Early Writings on Space (Chicago: Open Court, 1929).

Kritik der reinen Vernunft. Riga, 1781; 2nd ed., Riga, 1787. The first edition is customarily referred to as A, the second edition as B. The most useful modern edition is by Raymond Schmidt (Leipzig, 1926). There are English translations by Francis Heywood (London, 1838); J. M. D. Meiklejohn (London, 1854), F. Max Müller (2 vols., London, 1881), and N. Kemp Smith (London Macmillan, 1929). Kemp Smith's version is the fullest and most reliable.

Prolegomena zu einer jeden künftigen Metaphysik die als Wissenschaft auftreten können. Riga, 1783. English translations are available by John Richardson (Prolegomena to Future Metaphysics, in Metaphysical Works of the Celebrated Immanual Kant, London, 1836), J. P. Mahaffy and J. H. Bernard (The Prolegomena, London, 1872), E. B. Bax (Kant's Prolegomena and Metaphysical Foundations of Natural Science, London, 1883), Paul Carus (Prolegomena to Any Future Metaphysics, Chicago, 1902), L. W. Beck (same title as Carus's, New York: Liberal Arts Press, 1951), and P. G. Lucas (same title as Carus's, Manchester, U.K., 1953). The Beck and Lucas translations are much the best.

Grundlegung zur Metaphysik der Sitten. Riga, 1785; 2nd ed., Riga, 1786. Translated into English by T. K. Abbott as Fundamental Principles of the Metaphysic of Morals (in Kant's Critique of Practical Reason and Other Works on the Theory of Ethics, London, 1873), by L. W. Beck as Foundations of the Metaphysics of Morals (in Critique of Practical Reason and Other Writings in Moral Philosophy, Chicago: University of Chicago Press, 1949), by H. J. Paton (from the 2nd edition) as The Moral Law, or Kant's Groundwork of the Metaphysic of Morals (London: Hutchinson, 1948). All three versions are good; Paton's is the most elegant. Quotations in the text of this article are from Paton's translation; the citations to page numbers in the 2nd edition are taken from Paton's marginal notation.

Metaphysische Anfangsgründe der Naturwissenschaft. Riga, 1786. Translated into English by E. B. Bax (in Kant's Prolegomena and Metaphysical Foundations of Natural Science, London, 1883).

Kritik der praktischen Vernunft. Riga, 1788. Translated into English by T. K. Abbott, and also by L. W. Beck, as Critique of Practical Reason in the books cited for the Grundlegung zur Metaphysik der Sitten. The Beck translation is accurate but somewhat clumsy; it has been published separately (New York, 1956).

Kritik der Urteilskraft. Berlin and Liebau, 1790. Translated into English by J. H. Bernard as Kritik of Judgement (London, 1892; later reprinted as Critique of Judgement ). Also translated by J. C. Meredith in two parts, Critique of Aesthetic Judgement (Oxford, 1911) and Critique of Teleological Judgement (Oxford, 1928), which were reissued together as The Critique of Judgement (Oxford: Clarendon Press, 1952). Both the Bernard and the Meredith versions are of poor quality; Meredith's is slightly the better. Kant wrote an introduction to the Kritik that he discarded; it is available as Erste Einleitung in die Kritik der Urteilskraft, Vol. V, Kants Werke (Berlin, 1922), and in English translation by H. Kabir as Immanuel Kant on Philosophy in General (Calcutta: Calcutta University Press, 1935).

Die Religion innerhalb der Grenzen der blossen Vernunft. First part published separately, Berlin, 1792; published complete at Königsberg, 1793. Translated into English by John Richardson as Religion within the Sphere of Naked Reason (in Essays and Treatises, London, 1798), by J. W. Semple as Religion within the Boundary of Pure Reason (Edinburgh, 1838), T. M. Greene and H. H. Hudson as Religion within the Limits of Reason Alone (Chicago: Open Court, 1934; 2nd ed., with new matter by J. R. Silber, New York: Harper, 1960). The 1960 edition (Greene-Hudson-Silber) is the best.

Zum ewigen Frieden: ein philosophischer Entwurf. Königsberg, 1795. The two best English translations are L. W. Beck's Perpetual Peace (in Critique of Practical Reason and Other Writings in Moral Philosophy, Chicago, 1949; separately bound, New York, 1957) and C. J. Friedrich's Inevitable Peace (New Haven, CT, 1948).

Metaphysik der Sitten, Part I, Metaphysische Anfangsgründe der Rechtslehre ; Part II, Metaphysische Anfangsgründe der Tugendlehre. Separately bound, Königsberg, 1797. Part I translated into English by W. Hastie as Kant's Philosophy of Law (Edinburgh, 1887). Part II translated into English by James Ellington as Metaphysical Principles of Virtue (Indianapolis, 1964) and by Mary Gregor as The Doctrine of Virtue (New York: Harper and Row, 1964).

Anthropologie in pragmatischer Hinsicht. Königsberg, 1798. No English translation.

Eine Vorlesung über Ethik, edited from student's notes by P. Menzer. Berlin, 1924. Translated into English by Louis Infield as Lectures on Ethics (London: Methuen, 1930).

Kant on History. Indianapolis, 1963. Translations by L. W. Beck, R. E. Anchor, and E L. Fackenheim; contains Kant's minor essays on philosophy of history.

works on kant


The main sources for Kant's life, apart from his letters, are three memoirs published in Königsberg in 1804: L. E. Borowski's Darstellung des Lebens und Characters Immanuel Kants ; R. B. Jachmann's Immanuel Kant, geschildert in Briefen an einen Freund ; and E. A. C. Wasianski's Immanuel Kant in seinen letzten Lebensjahren. Wasianski's memoir is extensively used in Thomas De Quincey's "The Last Days of Kant" (Works, Vol. XII). See also Ernst Cassirer's Kants Leben und Lehre (Berlin, 1921), and for a useful short life Karl Vorländer's Immanuel Kants Leben (Leipzig, 1911).


Rudolf Eisler's Kantlexicon (Berlin, 1930) and Heinrich Ratke's Systematisches Handlexicon zu Kants Kritik der reinen Vernunft (Leipzig, 1929) are valuable aids to the Kantian student. The periodical Kantstudien has published many important contributions to Kantian scholarship and discussion.

For commentaries on the Critique of Pure Reason, see Hans Vaihinger, Kommentar zur Kritik der reinen Vernunft, 2 vols. (Stuttgart: Spemann, 18811892), which covers the opening sections only; N. Kemp Smith, A Commentary to Kant's Critique of Pure Reason (London: Macmillan, 1918; rev. ed., 1923), which is strongly influenced by Vaihinger's "patchwork" theory; H. J. Paton, Kant's Metaphysic of Experience, 2 vols. (London: Allen and Unwin, 1936), which covers the first half only and is sharply critical of Kemp Smith; A. C. Ewing, A Short Commentary on Kant's Critique of Pure Reason (London: Methuen, 1938). T. D. Weldon, Kant's Critique of Pure Reason (Oxford, 1945; 2nd ed., Oxford: Clarendon Press, 1958).

On the theory of knowledge see also H. A. Prichard, Kant's Theory of Knowledge (Oxford: Clarendon Press, 1909); A. C. Ewing, Kant's Treatment of Causality (London: K. Paul, Trench, Trubner, 1924); W. H. Walsh, Reason and Experience (Oxford: Clarendon Press, 1947); Graham Bird, Kant's Theory of Knowledge (London: Routledge and Paul, 1962); R. P Wolff, Kant's Theory of Mental Activity (Cambridge, MA: Harvard University Press, 1963).

For commentaries on the Critique of Practical Reason and other works on ethics, see L. W. Beck, A Commentary on Kant's Critique of Practical Reason (Chicago, 1960), a good source; H. J. Paton, The Categorical Imperative (London: Hutchinson, 1947), a detailed commentary on the Grundlegung ; W. D. Ross, Kant's Ethical Theory (Oxford, 1954); A. R. C. Duncan, Practical Reason and Morality (Edinburgh, 1957); M. J. Gregor, Laws of Freedom (Oxford: Blackwell, 1963), which expounds the Metaphysic of Morals ; P A. Schilpp, Kant's Pre-Critical Ethics (Evanston, IL: Northwestern University, 1938), A. E. Teale, Kantian Ethics (London: Oxford University Press, 1951).

For commentaries on the Critique of Judgment, see Konrad Marc-Wogau, Vier Studien zu Kants Kritik der Urteilskraft (Uppsala, Sweden, 1938); H. W. Cassirer, A Commentary on Kant's Critique of Judgment (London: Methuen, 1938).

Commentaries on other aspects of Kant's thought are also available. On the precritical writings, see Giorgio Tonelli, Elementi metafisici e metodologici in Kant precritico (Turin, 1959). On Kant's philosophy of religion, see C. C. J. Webb, Kant's Philosophy of Religion (Oxford: Clarendon Press, 1926) and F. E. England, Kant's Conception of God (London: Allen and Unwin, 1929). On Kant's philosophy of history, see Klaus Weyand, Kants Geschichtsphilosophie (Cologne: Cologne University Press, 1964). On Kant as a scientist, see Erich Adickes, Kant als Naturforscher, 2 vols. (Berlin, 19241925). On the Opus Postumum, see Erich Adickes, Kants Opus Postumum dargestelt und beurteilt (Berlin, 1920).

General Studies

S. Körner, Kant (Harmondsworth, U.K., 1955) is the best general introduction; see also G. J. Warnock's chapter in A Critical History of Western Philosophy, edited by D. J. O'Connor (New York: Free Press of Glencoe, 1964).

Edward Caird, The Critical Philosophy of Kant, 2 vols. (Glasgow, 1889), criticizes Kant from the Hegelian position. Martin Heidegger, Kant und das Problem der Metaphysik (Bonn: Cohen, 1929) examines Kant as an "ontologist." H. J. de Vleeschauwer, La déduction transcendentale dans l'oeuvre de Kant, 3 vols. (Antwerp, 19341937), presents an exhaustive survey of Kant's writings on the problem; de Vleeschauwer offers a one-volume summary in L'évolution de la pensée kantienne (Paris, 1939), which has been translated into English by A. R. C. Duncan as The Development of Kantian Thought (London: Nelson, 1962). Gottfried Martin, Immanuel Kant, Ontologie und Wissenschaftstheorie (Cologne, 1951), translated into English by P. G. Lucas as Kant's Metaphysics and Theory of Science (Manchester, U.K.: Manchester University Press, 1955), is influenced but not dominated by Heidegger. Richard Kroner, Kants Weltanschauung (Tübingen, 1914), translated into English by J. E. Smith as Kant's Weltanschauung (Chicago: University of Chicago Press, 1956), stresses Kant's emphasis on the practical. R. Daval, La métaphysique de Kant (Paris: Presses Universitaires de France, 1951), presents "schematism" as the key idea in Kant's thought.

recent translations

The Cambridge Edition of the Works of Immanuel Kant: Lectures on Metaphysics. Edited and translated by Karl Ameriks and Steve Naragon. Cambridge, U.K.: Cambridge University Press, 1997.

Critique of Pure Reason. Edited and translated by Paul Guyer and Allen W. Wood. Cambridge, U.K.: Cambridge University Press, 1998.

Ethical Philosophy. Translated by James W. Ellington. Indianapolis: Hackett, 1983.

Immanuel Kant: Critique of Judgment. Translated by Werner S. Pluhar. Indianpolis: Hackett, 1987.

Immanuel Kant: Critique of Pure Reason: Unified Edition (with all variants from the 1781 and 1787 editions). Edited and translated by Werner S. Pluhar. Indianapolis: Hackett, 1996.

The Metaphysics of Morals. Edited and translated by Mary Gregor. Cambridge, U.K.: Cambridge University Press, 1996.

Opus Postumum/Immanuel Kant. Edited by Eckart Forster. Translated by Eckhart Forster and Michael Rosen. Cambridge, U.K.: Cambridge University Press, 1993.

Perpetual Peace and Other Essays on Politics, History, and Morals. Translated by Ted Humphrey. Indianapolis: Hackett, 1983.

Prolegomena to Any Future Metaphysics: That Will Be Able to Come Forward as Science with Selections from the Critique of Pure Reason. Rev. ed. Edited and translated by Gary Hatfield. Cambridge, U.K.: Cambridge University Press, 2004.

recent secondary literature

Allison, Henry E. Kant's Theory of Freedom. New York: Cambridge University Press, 1990.

Ameriks, Karl. Kant and the Fate of Autonomy: Problems in the Appropriation of the Critical Philosophy. New York: Cambridge University Press, 2000.

Ameriks, Karl. Kant's Theory of Mind: An Analysis of the Paralogisms of Pure Reason. 2nd ed. New York: Oxford University Press, 2000.

Beck, Lewis White. Early German Philosophy; Kant and His Predecessors. Cambridge, MA: Belknap Press of Harvard University Press, 1969.

Cohen, Ted, and Paul Guyer, eds. Essays in Kant's Aesthetics. Chicago: University of Chicago Press, 1982.

Di Giovanni, George. Freedom and Religion in Kant and His Immediate Successors: The Vocation of Humankind, 17741800. New York: Cambridge University Press, 2005.

Findlay, John N. Kant and the Transcendental Object: A Hermeneutic Study. New York: Oxford University Press, 1981.

Forster, Eckhart, ed. Kant's Transcendental Deductions: The Three Critiques and the Opus Postumum. Stanford, CA: Stanford University Press, 1989.

Friedman, Michael. Kant and the Exact Sciences. Cambridge, MA: Harvard University Press, 1992.

Guyer, Paul, ed. The Cambridge Companion to Kant. New York: Cambridge University Press, 1992.

Guyer, Paul. Kant and the Claims of Knowledge. New York: Cambridge University Press, 1987.

Guyer, Paul. Kant and the Claims of Taste. 2nd ed. New York: Cambridge University Press, 1997.

Guyer, Paul, ed. Kant and the Experience of Freedom: Essays on Aesthetics and Morality. New York: Cambridge University Press, 1993.

Guyer, Paul. Kant on Freedom, Law, and Happiness. New York: Cambridge University Press, 2000.

Henrich, Dieter. Aesthetic Judgment and the Moral Image of the World: Studies in Kant. Stanford, CA: Stanford University Press, 1992.

Keller, Pierre. Kant and the Demands of Self-Consciousness. Cambridge, U.K.: Cambridge University Press, 1998.

Kitcher, Patricia. Kant's Critique of Pure Reason: Critical Essays. Lanham: Rowman & Littlefield, 1998.

Kuehn, Manfred. Kant: A Biography. New York: Cambridge University Press, 2001.

Longuenesse, Beatrice. Kant and the Capacity to Judge: Sensibility and Discursivity in the Transcendental Analytic of the Critique of Pure Reason. Translated by Charles T. Wolfe. Princeton, NJ: Princeton University Press, 1998.

Neiman, Susan. The Unity of Reason: Rereading Kant. New York: Oxford University Press, 1994.

Stratton-Lake, Philip. Kant, Duty, and Moral Worth. London; New York: Routledge, 2000.

Van Cleve, James. Problems from Kant. New York: Oxford University Press, 1999.

Walker, Ralph C. S. Kant. New York: Routledge, 1999.

Walker, Ralph C. S. Kant: The Arguments of the Philosophers. Boston: Routledge & Kegan Paul, 1978.

Watkins, Eric. Kant and the Metaphysics of Causality. New York: Cambridge University Press, 2005.

Wood, Allen W. Kant. Malden, MA: Blackwell, 2005.

Wood, Allen W. Self and Nature in Kant's Philosophy. Ithaca, NY: Cornell University Press, 1984.

Yovel, Yirmiahu. Kant and the Philosophy of History. Princeton, NJ: Princeton University Press, 1980.

W. H. Walsh (1967)

Bibliography updated by Tamra Frei (2005)

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Kant, Immanuel

(b. Königsberg, Germany [now Kaliningrad, R.S.F.S.R.], 22 April 1724; d. Königsberg, 12 February 1804)

philosophy of science.

Kant was the fourth child of Johann Georg Cant and Anna Regina (Reuter) Cant. His paternal grandfather was an immigrant from Scotland, where the name Cant is still not uncommon in the northern parts. Immanuel changed the spelling to Kant in order that the name might conform more comfortably with the usual pratices of German pronunciation. His father was a saddle maker of modest means. His mother was much given to Pietism, a Protestant sect (not unlike the Quakers and early Methodists) which flourished in northern Germany at the time.

When Kant was ten, he entered the Collegium Fridericianum, intending to study theology. But he actually spent more time with classics, and he became quite adept in Latin. In 1740 he entered the University of Königsberg and studied mainly mathematics and physics with Martin Knutzen and Johann Teske. These years doubtless influenced him much in his interest in the philosophy of science. In 1746 Kant’s father died, and he was forced to interrupt his studies to help care for his brother and three sisters by being a private tutor in three different families successively for a period of some nine years. Finally, in 1755 he was able to resume his studies at the university and received his doctorate in philosophy in the autumn of that year. For the next fifteen years he earned a meager living as a Privatdozent lecturing on physics and nearly all aspects of philosophy. In 1770 he was given the chair of logic and metaphysics at the University of Königsberg, a position which he held until he retired in 1797.

Although Kant was brought up in Pietistic surroundings and in his youth even considered becoming a minister, in his maturity he became the one who, above all others, liberated philosophy and science from theology. His single-minded devotion to both philosophy and science also accounts largely for the fact that he never married. He was slightly built and gave the appearance of having a delicate constitution, but his careful attention to the laws of health and the regularity of his habits enabled him to live to be almost eighty.

Kant was very modest in his style of living. In 1783 he purchased a house in the center of town and quite regularly thereafter entertained friends at dinner. The number of his table companions was never large because his dinner service could accommodate but six persons. These companions were for the most part men of great culture and learning, and his dinners were widely known for the liveliness and diversity of the conversation.

The German writer Johann Gottfried von Herder said that Kant in his prime had the happy sprightliness of a boy and that he continued to have much of it even as an old man. He had a broad forehead, Herder continued, that was built for thinking and that was the seat of an imperturbable cheerfulness and joy. Speech rich in thought issued from his lips. He also possessed playfulness, wit, and humor. He enlivened his lectures and conversations by drawing on the history of men and peoples and on natural history, science, mathematics, and his own observations. He was indifferent to nothing that was worth knowing, concluded Herder.

Even though Kant is widely considered to be one of the two or three greatest philosophers that Western civilization has produced, he was also much interested in science and especially in the philosophy of science. He was not an experimental scientist and did not contribute to the body of scientific knowledge, but he was much concerned with the foundations of science and made significant contributions to that field. He has sometimes been accused (as by Erich Adickes in his Kant als Naturforscher) of being an armchair scientist. He might more accurately be called an armchair philosopher speculating on the fundamental bases of science. He was not interested in gleaning facts and data; rather, he speculated concerning the grand scheme in which the facts gleaned by others are arrayed.

The two main influences on Kant in his philosophical reflections on science were Leibniz and Newton. During his first period of study at the University of Königsberg, from 1740 to 1746, Knutzen taught that version of Leibniz’s metaphysics which the German philosopher Christian von Wolff had made popular. He also taught the mathematical physics which Newton had developed. He revealed to the young Kant the various oppositions, puzzles, and contradictions of these two great natural philosophers.

The nature of space and time was what interested the young Kant most in these disputes between Leibniz and Newton. He studied the famous exchange of letters between Leibniz and Samuel Clarke, a defender of Newton’s philosophy. Leibniz claimed that the universe is made up of an infinitude of monads, which are simple, immaterial (spiritual) substances. Every monad is endowed with some degree of consciousness. He conceived of space as a set of relations which the monads have to one another; it is the order of coexistent things. He thought of time as the relations of the successive states of consciousness of a single monad. Physical bodies, on this theory, are groups of monads. Mathematically considered, every monad is a dimensionless point. Length, breadth, and position can be represented as relations of monads. Space, then, is a continuous, three-dimensional system of mathematical points corresponding to the order of a plenum of distinct monads. Time has but one dimension; succession and coexistence are the only temporal relations, corresponding, as they do, to the order of perceptions in the consciousness of a monad. For Leibniz, then, space and time were relations among things (monades) which would have no existence whatever if there were no monads.

By contrast, Newton held that space and time are infinite and independent of the physical bodies that exist in space and time. For him space and time were things, and they would exist even if there were no bodies. He held that are absolute positions in space and time that are independent of the material entities occupying them and, furthermore, that empty space (void) and empty time are possible. Leibniz denied both tenets. Neither Leibniz nor Clarke was able fully to undermine the position of the other, and the result was an impasse.

In his early years Kant pondered the nature of space and time first from the point of view of Leibniz and then of Newton, but eventually he found both positions unsatisfactory. In his Thoughts on the True Estimation of Living Forces (1747) he took Leibniz’s view and tried to explain the nature of space by means of the forces of unextended substances (monades) that cause such substances to interact. He attempted to account for the threefold dimensionality of space by appealing to the laws that govern such interactions; but he was not very successful, as he himself admitted.

In his On the First Ground of the Distinction of Regions in Space (1768) Kant took Newton’s view that space is absolute and argued against Leibniz’s relational theory of space. He used the example of a pair of human hands. They are perfect counterparts of one another, yet they are incongruent (like left-and right-hand spirals). The two hands are identical as far as their spatial relations are concerned, but they are, nevertheless, spatially different. Therefore space is not just the relationship of the parts of the world to one another.

When Kant was inaugurated as professor of logic and metaphysics in 1770, he submitted a dissertation, in accordance with the custom of the time. It was entitled On the Form and Principles of the Sensible and Intelligible World. Here his views on space and time had developed to a point that was very close to the views enunciated in the Critique of Pure Reason (1781). Space and time are the schemata and conditions of all human knowledge based on sensible intuition. Our concepts of space and time are acquired from the action of the mind in coordinating its sensa according to unchanging laws. The sensa are produced in the mind by the presence of some physical object or objects. Space and time are now based epistemologically on the nature of the mind rather than ontologically on the nature of things, either as a relation among monads (Leibniz) or as a thing (Newton’s absolute space). Kant had turned from modes of being to ways of knowing. This new epistemological view of space and time provided him with a way of reconciling the opposed views of Leibiz and Newton. Space and time are indeed the relational orders of contemporaneous objects and successive states, inasmuch as space and time are the conditions of intuitive representations of objects, rather than being mere relations of independent substances (monads). Space and time are indeed absolute wholes in which physical objects are located, inasmuch as they are forms of sensible intuition lying ready in the mind, rather than being independently existing containers for physical objects.

Kant’s in the Critique differ from those of the Dissertation in that space and time are held in the former to be passive forms of intuition by means of which a manifold of sensa are presented to the understanding, which has the active function of synthesizing this manifold. Space is the form of all appearances of the external senses, just as time is the form of all appearances of the internal sense. As such, space and time are nothing but properties of the human mind. Everything in our knowledge that belongs to spatial intuition (extension), change according to which change of location is determined. The representations of the external senses are set in time, which contains nothing but relations of succession, coexistence, and duration.

Geometry is based on the pure intuition of space. To say that a straight line is the shortest distance between two points involves an appeal to spatial intuition. The concept of straight is merely qualitative. The concept of shortest is not already contained in the concept of straight but is an addition to straight through recourse to the pure intuition of space. Accordingly, the propositions of geometry are not analytic but a priori synthetic. So are the propositions of arithmetic. The concept of units in the pure intuition of time. Leibniz had claimed that the propositions of mathematics are analytic. For Kant even some of the propositions of mechanics cannot attain its concepts of motion without employing the representation of time.

As we have seen, Kant rejected Newton’s absolute space conceived as an independently existing whole containing all physical objects. In the Metaphysical Foundations of Natural Science (1786) he pointed out a meaning for “absolute space” which makes it a legitimate idea. At the beginning of “Phoronomy” in that treatise, he distinguishes relative space from absolute space. Relative (or material or empirical) space is the sum total of all objects of experience (bodies). Such space is movable because it is defined by material entities (bodies). If the motion of a movable space is to be perceived, that space must be contained in another, larger space in which it is to move. This larger space must be contained in another, still larger one, and so on to infinity. Absolute space is merely that largest space which includes all relative ones and in which the relative ones move. As such, absolute (empty) space cannot be perceived because it is not defined by material entities, as relative (empirical) spaces are, and so exists merely in idea, with no actual ontological status. Kant claimed that Newton mistakenly endowed such absolute space with ontological significance.

The terms “physical entities,” “material objects,” “bodies,” and similar ones have been used from time to time in the foregoing discussion without any exact definitions being given for them. They are all roughly analogous terms and involve what Kant usually calls “matter” or “body.” Toward the end of the “Dynamics” in the Metaphysical Foundations of Natural Science he does say that a body is matter between determinate boundaries and thus has definite shape. “Matter” is therefore a more general term than “body,” but he often uses the two interchangeably. What, indeed, is matter for Kant? In the development of his thought at the stage of the Dissertation, he distinguished a sensible world from an intelligible one. The former is the world which sense reveals, and the latter is what the intellect reveals. He called the former world phenomenal and the latter noumenal. The former is the world of things as they appear, while the latter consists in things as they are. Sensibility with its two pure forms, space and time, provides the foundation for the validity of physics and geometry; however, the scope of the application of these two sciences is restricted to phenomena. Intellect with its pure concepts of substance, cause, possibility, existence, and necessity provides the foundation for the validity of the metaphysics of monads; this science yields an intellectual knowledge of such substances (monads) as they are in themselves, but there is no sensible knowledge of monads. The concepts of matter and body are empirical, sensitive ones belonging to physics but not to metaphysics.

By the time Kant’s thought attained full maturity in the Critique of Pure Reason, the pure concepts of substance, cause, possibility, existence, and necessity had become coterminous with the two pure forms of intuition, space and time, in having a valid application to nothing but phenomena. The intelligible world of monads, conceived in the Dissertation as a known realm of things-in-themselves, becomes in the Critique unknowable realm of noumena underlying the knowable realm of Phenomena. One has a detailed and actual knowledge of matter and body but only a problematic knowledge of monads and noumena. The noumena did not wither away completly in the idealist like Berkeley or a phenomenalist like Hume. Rather, Kant was a type of realist not unlike Descartes or Locke in his claim that appearances are not all that there is but are all that one has an actual and detailed knowledge of. There is a reality behind the appearance, but one has only a problematic concept of this reality. He often characterized this position of the Critique as transcendental idealism in order to distinguish this brand of idealism from the extreme form typified by Berkeley.

And so matter can be defined, in most general terms, as an appearance given in space. When one turns to a more particular characterization of matter, one finds that Kant”s mature theory of matter developed as an opposition to the atomist view of matter held by Newton and the monadist view of matter held by Leibniz. For Newton matter is composed of physical espouse some form of simple realism and doubtless would have held that these atoms would move about in empty space even if there were no sentient beings anywhere to perceive them. The atoms are absolutely impenetrable, and this means that the matter contituting an atom coheres with a force that cannot be overcome by any existing force in nature. Atoms are absolutely homogeneous as to density. They differ from one another only in size and shape. Bodies are aggregates of such atoms and differ in density according to how much empty space, or void, is interspersed among the atoms.

In the “Dynamics” of the Metaphysical Foundations Kant objected to such absolute impenetrability as being an occult quality that no experiment or experience whatsoever could substantiate. We have seen earlier what Kant thought about absolute, empty space. Newton thus regarded matter as an interuptum. So also did Kant in his early work entitled Physical Monadology (1756). But in the Critical thought of the Metaphysical Foundations, he rejected all forms of atomism and monadology. He maintained that matter is a continuum, as we shall see.

Motive forces were for him the fundamental attributes of matter, a position which he held even in the days of the Physical Monadology. By contrast, Newton had taken a different view on the relation between forces and matter. For him atoms are inert but mobile. Since inertia is an entirely passive property of the atoms, they must be moved by an active principle external to them. God is the ultimate cause of gravitational motion by virtue of His acting through the immaterial medium of absolute space, as one can infer from various scholia in the Principlia and queries in the Opticks. Accordingly, Newton did not regard attraction (as Kant did) as a basic property of matter itself. For Kant only two kinds of moving forces are possible: repulsive and attractive. If two bodies (regarded as mathematical points) are being considered, then any motion which the one body can impress on the other must be imparted in the straight line joining the two points. They either recede from one another or approach one another; there are no other possibilities. Since forces are what cause bodies to move, the only kinds of forces are therefore repulsive and attractive.

When one body tries to enter the space occupied by another body, the latter resists the intrusion and the former is moved in the opposite direction. The repulsive (or expansive) force exerted here is also called elastic. For Kant all matter is originally elastic, infinitely compressible but impenetrable—one body cannot compress another to the extent that the first occupies all the space of the second. He called such elasticity. “relative impenetrability” and contrasted it with the absolute impenetrability posited by atomism. The relative kind has a degree that can be ascertained by experience—for instance, gold is more penetrable than iron—whereas the absolute kind is open to no experience whatsoever. On the atomic theory, bodies are compressed when the empty space among the atoms constituting bodies is eliminated and the atoms stand tightly packed. But once so packed, they admit of no further compression.

Unless there were another force acting in an opposite direction to repulsion, that is, acting for approach, matter would disperse itself to infinity. By means of universal attraction all matter acts directly on all other matter and so acts at all distances. This force is usually called gravitation, and the endeavor of a body to move in the direction of the greater gravitation is called its weight. If matter possessed only gravitational force, it would all coalesce in a point. The very possibility of matter as an entity filling space in a determinate degree depends on a balance between repulsion and attraction. Sensation makes us aware of repulsion when we feel or see some physical object and ascertain its size, shape, and location. Repulsion is directly attributed to matter. Attraction is attributed to matter by inference, since gravitation alone makes us aware of no object of determinate size and shape but reveals only the endeavor of our body to approach the center of the attracting body.

True attraction is action at a distance. The earth attracts the moon through space that may be regarded as wholly empty. And so gravity acts directly in a place where it is not. Descartes and others thought this to be a contradictory notion and tried to reduce all attraction to repulsive force in contact. Attraction is therefore nothing but apparent attraction at a distance. Descartes propounded the theory of a plenum with fourteen vortices to account for the celestial motions of the planets about the sun and the moons about the planets. Newton objected to such plenum and vortices because he thought that the friction between the celestial bodies and this hypothesized swirling fluid medium would slow down the celestial motions and eventually terminate them. He, like Kant, espoused a true attraction rather than an apparent one.

If Kant had ever critically examined Newton’s suggestions as to the ultimate cause of gravitation, he doubtless would have had emphatic objections. He showed in the Critique of Pure Reason that God’s existence cannot be established by theoretic reason. For him attraction is a property of matter itself. He argued against Descartes’s apparent attraction by pointing out that such attraction operates by means of the repulsive forces of pressure and impact so as to produce the endeavor to approach, just as in the case when one billiard ball approaches another after the first has been hit by a cue. But there would not even be any impact or pressure unless matter cohered in such a way as to make such impact and pressure possible. Matter would disperse itself to infinity if it possessed nothing but repulsive force. Hence there must be a true attraction acting contrary to repulsion in order for impact and pressure to bring about even apparent attraction.

Thus matter in general was reduced by Kant to the moving forces of repulsion and attraction. He appealed to these forces to account for the specific varieties of matter. Attraction depends on the mass of the matter in a given space and is constant. Repulsion depends on the degree to which the given space is filled; this degree can vary widely. For example, the attraction of a given quantity of air in a given volume depends on its mass and is constant, while its elasticity is directly proportional to its temperature and varies accordingly. This means that repulsion can, with regard to one and the same attractive force, be originally different in degree in different matters. Consequently, a spectrum of different kinds of matter each having the same mass (and therefore having the same attraction) can vary widely in repulsion—running, for instance, from the density of osmium to the rarity of the ether. And so every space can be thought of as full and yet as filled in varying measure.

Kant claimed that matter is continuous quantity involving a proportion between the two fundamental forces of attraction and repulsion. For an atomist like Newton matter is discrete quantity, and the force of attraction in his theory is superadded through the agency of God. The varying densities of elements and compounds of matter are for Newton a function of the amount of empty space interspersed among the atoms. Empty space, according to Kant, is a fiction that can be discerned by no sense experience whatever. The senses reveal to us only full spaces. Kant’s theory of matter committed him to accept the existence of an ether.

The ether was mentioned in many of his writings. In his doctoral dissertation, entitled A Brief Account of Some Reflections on Fire (1755), Kant said in proposition VIII that the matter of heat (or the caloric) is nothing but the ether (or the matter of light) which is compressed within the interstices of bodies by means of their strong attraction. In the Metaphysical Foundations of Natural Science he accepted the existence of the ether cautiously, as a hypothesis that he found more plausible than the atomists’ hypothesis of the reality of absolutely impenetrable atoms and absolutely empty space. Toward the end of chapter 2 the ether is characterized as a matter that entirely fills space, leaving no void. It is so rarefied that it fills its space with far less quantity of matter than any of the bodies known to us fill their spaces. In relation to its attractive force the repulsive force of the ether must be incomparably greater than in any other kind of matter known to us.

Between 1790 and 1803 Kant worked on what is now called the Opus postumum. At his death this unfinished work survived as a stack of handwritten pages, which were eventually gathered by editors into thirteen fascicles (Convoluten). Sections of it constitute coherent wholes, others provide illustrations, and still others are repetitions of earlier works. The Opus appears in Volumes XXI and XXII of the Royal Prussian Academy edition of Kant’s works. Part of the Opus contains the Transition From the Metaphysical Foundations of Natural Science to Physics. The theory of the ether figures in almost all parts of the Transition but especially in Convolute X, XI, and XII of the Opus. There the ether is characterized as a matter that occupies absolutely every part of space, that penetrates the entire material domain, that is identical in all its parts, and that is endowed with a spontaneous and perpetual motion.

Kant based his proof of the ether’s existence upon the unity of experience. Space, which is unitary, is the form of all experience; hence experience is unitary. Experience is a system made up of a manifold of sense perceptions synthesized in space by the intellect. These perceptions are caused by the actions of the material forces which fill space. Accordingly, the motive forces of matter must collectively be capable of constituting a system in order to conform to the unity of possible experience. Such a system is possible only if one admits, as the basis of these forces, the existence of an ether that has the properties listed above. Therefore, the existence of the ether is the a priori condition of the system of experience. Many critics have found this proof unconvincing, as well they might. The Transition, as it has come down to us, is merely a series of sketches for a work that was never finished. Accordingly, it suggests about as many unanswered questions as it provides solutions.

Kant in his mature period opposed not only atomism but also all forms of monadology. He was like Leibniz and unlike Newton in that he put the emphasis, both in his youth and in his maturity, on force rather than on atomic particles of impenetrable mass. In the Physical Monadology (1756) he even claimed (following Leibniz) that bodies are composed of monads, which are indivisible, simple substances. The space which bodies fill is infinitely divisible and is not composed of original, simple parts because space does not have any substantiality; it is only the appearance of the external relations bound up with the unity of the monad. So conceived, the infinite divisibility of space is not opposed to the simplicity of monads. Matter is not infinitely divisible, while space is. But by the time his thought had arrived at the critical phase represented by the Critique of Pure Reason and the Metaphysical Foundations, Kant had repudiated both the view (derived from Leibniz) that bodies are composed of monads and the view (espoused by Leibniz) that space is a relation among monads. Perceptible matter was now continuous quantity, and space was a form of sensible intuition. What did he think now about the infinite divisibility of matter and space? One must turn to the Second Antinomy in the “Dialectic” of the Critique and the “Dynamics” of the Metaphysical Foundations to learn the answer.

The outcome of these discussions is this: Matter as appearance is infinitely divisible and therefore consists of infinitely many parts, but matter as appearance does not consist of the simple (either atoms or monads); matter as thing-in-itself does not consist of infinitely many parts (either atoms or monads), but matter as thing-in-itself does consist of the simple. It was pointed out earlier that according to Kant’s position of transcendental idealism, we have actual cognition of things as appearances and a problematic concept of the reality behind the appearance. Accordingly, matter can be regarded as appearance or as the reality (thing-in-itself) behind the appearances.

Intuitive space is divisible to infinity. Any matter filling such space is also divisible to infinity. But this means that matter as appearance is infinity. But this means that matter as appearance is infinitely divisible; it does not mean that matter as thing-in-itself consists of infinitely many parts (as an atomist or a monadist might claim). Only the division of the appearance can be infinitely continued, not the division of the thing-in-itself. Any whole as thing-in-itself must already contain all the parts into which it can be divided. But the division process can never be finished. And so the thought that matter as thing-in-itself contains infinitely many parts is self-contradictory.

Furthermore, it cannot be maintained that matter as appearance is made up of the simple. The composite of things-in-themselves must consist of the simple, since the parts must be given before all composition. But the composite in the appearance does not consist of the simple, because an appearance can never be given in any way other than as composite (extended in space); its parts can be given only through the process of division, and therefore not before the composite but only in it (and thus the atomist and monadist are foiled again).

Even though matter as appearance is mathematically divisible into infinitely many parts, no real distance of parts is to be assumed. Physicists usually represent the repulsive forces of the parts of elastic matters (for instance, a gas) when these matters are in a state of greater or lesser compression as increasing or decreasing in a certain proportion to the distance of their parts from one another. This is necessary for the mathematical construction of the concept corresponding to such a state of elastic matters; in this construction all contact of parts is represented as an infinitely small distance. The Posited spatial distance of the parts should be understood, however, as nothing but a mathematical convenience, necessary convenience though it is. In reality, matter is continuous quantity, and there is no spatial distance between its parts; they are always in contact.

Time, space, matter, force—Kant’s views on these fundamental concepts of natural science have now been examined; but motion has not yet been considered in any detail. In contrast with Newton, Kant claimed in the “Phenomenology” of the Metaphysical Foundations, as well as in the earlier New Conception of Motion and Rest (1758), that all motion is relative. The motion of a body is the change of its external relations to a given space. If a ball rolls on a table top, it changes its position relative to various points on the top. But we have the same change of positions if the ball remains at rest and the table moves under it in the opposite direction with the same velocity. Hence the rectilinear motion of a body with regard to an empirical space can be viewed as either the body moving by reference to the space at rest or as thebody at rest and the space moving relative to it. It is impossible to think of a body in rectilinear motion relative to no material space outside of it. Matter can be thought of as moved or at rest only in relation to matter and never by reference to mere space without matter. Furthermore, there is no fixed empirical point by reference to which absolute motion and absolute rest can be determined. The center of the sun might be fixed as the center of our solar system, but our solar system moves relative to other solar systems in the Milky Way, and the Milky Way moves relative to other galaxies, and so on.

Accordingly, there is no empirical space defined by matter that can provide a reference system for all possible rectilinear motions of bodies in the universe. Therefore, all motion or rest is merely relative, and neither is absolute. But the empirical space (for instance, the table top) in relation to which a body (for instance, the ball) moves or remains at rest must itself be referred to another (absolute) space at rest within which this given empirical space is movable. If one did not invoke such immovable, absolute space, one would be claiming that the given empirical space isimmovable and hence absolute; but by experience all material spaces are movable. This ultimate absolute space by reference to which all empirical spaces are movable (and hence relative) exists merely in thought and not in fact, since only empirical (material) spaces actually exist. But such absolute (immovable, immaterial) space is nevertheless a necessary idea that serves as a rule for considering all motion therein as relative. Everything empirical is movable in such ideal absolute space; and all such motions in it are valid as merely relative to one another, while none is valid as absolute. And so the rectilinear motion of a body in relative space is reduced to absolute space when one thinks of the body as in itself at rest but thinks of the relative space as moved in the opposite direction in absolute space.

The circular motion of a body might seem, at first glance, to be an absolute motion. In contrast with the foregoing case of rectilinear motion, it is not all the same whether the earth is regarded as rotating on its axis while the heavens remain still (Copernicus) or the earth is regarded as staying still while the heavens rotate about it (Ptolemy). Both give the same appearance of motion. But the former case is the true one, while the second one is false. To prove that the earth rotates, Kant says that if one puts a stone at some distance from the surface of the earth and drops it, then the stone will not remain over the same point of the earth’s surface in its fall but will wander from west to east. Accordingly, the rotation of the earth on its axis (or the rotation of any other body) is not to be represented as externally relative. But does this mean that the motion is absolute? Even though circular motion exhibits no real change of place with regard to the space outside of the rotating body, such motion does exhibit a continuous dynamic change of the relation of matter within its space. If the earth were to stop spinning, it would contract in size. The present size of the earth involves a balance between centrifugal forces and attracting ones. Hence the actuality of the earth’s rotation rests upon the tendency of the parts of the earth on opposite sides of the axis of rotation to recede from one another. The rotation is actual in absolute space, since this rotation is referred to the space within, and not to that outside of, the rotating body. And so rotation is not absolute motion but is a continuous change of the relations of matters (or parts of the rotating body) to one another; this change is represented in absolute space (the space within the rotating body), and for this reason such change is actually only relative motion.

The case of the translation of body relative to a material reference system and the case of a rotating body have now been considered. What about the third and last case, in which one body hits another? Is this motion absolute? In this case both the matter and the (relative) space must necessarily be represented as moved at the same time: in every motion of a body whereby it is moving with regard to another body, an opposite and equal motion of the other body is necessary. One body cannot by its motion impart motion to another body that is absolutely at rest; this second body must be moved (together with its relative space) in the opposite direction with just that quantity of motion which is equal to that quantity of motion which it is to receive through the agency of the first body and in the direction of this first one. Both bodies, subsequently, put themselves relative to one another—that is, in the absolute space lying between their two centers—in a state of rest. But with reference to the relative space outside of the impacting bodies, the bodies move after impact with equal velocity in the direction in which the first body is moving. This same law holds if the impact involves a second body that is not at rest but moving. There is no absolute motion in this third case, even though a body in absolute space is thought of as moved with regard to another body. The motion in this case is relative not to the space surrounding the bodies but only to the space between them. When this latter space is regarded as absolute, it alone determines their external relation to one another. And so this motion is merely relative.

In the case of rectilinear motion, the change of place may be attributed either to the matter (that is, space at rest and matter moving with respect to it) or to the space (that is, matter at rest and space moving with respect to it). In the case of rotatory motion, the change of place must be attributed to the matter. In the case of colliding bodies, both the matter and the (relative) space must necessarily be represented as moved at the same time. Motion is relative in all three cases by reference to absolute space: in the first case by reference to absolute space outside of the body, in the second to absolute space inside of the body, and in the third to absolute space between two bodies.

In a pre-Critical work entitled Universal Natural History and Theory of the Heavens (1755) Kant was much more favorably disposed toward Newton than he was in his mature period. In fact, the full title of the work has this addition: An Essay on the Constitution and Mechanical Origin of the Whole Universe Treated According to Newtonian Principles. In this book Kant went far beyond anything that is to be found in Newton’s own writings. Newton aimed at nothing more than describing and explaining the regularities that exist in the world in its present state of evolution. He paid special attention to the regularities of the planets and their motions around the sun, but nowhere did he try to explain, on the basis of his own mechanical principles, how the solar system originated and reached its present state of uniformity. In his Theory of the Heavens, Kant, by a series of bold strokes, anticipated astronomical facts that were later confirmed by very powerful observational techniques and with the help of relativistic cosmological theory. He conjectured that our solar system is a part of a vast system of stars making up a single galaxy, that the so-called nebulous stars are galactic systems external to but similar to our own galaxy (a fact that was not confirmed until the twentieth century), and that there are many such galaxies making up the universe as a whole. Much of this thought was stimulated by the work of an Englishman, Thomas Wright of Durham, entitled Original Theory or New Hypothesis of the Universe (1750).Kant read an abstract of this book in a Hamburg newspaper of January 1751. Wright gave the first essentially correct interpretation of the Milky Way and suggested that the nebulae are systems of stars much like our own galaxy. Newton provided Kant with the fundamental physical principles to help him in the development of his cosmogony, while Wright gave suggestions for working out the particulars of the spatial organization of the main components of the universe as a whole.

At this pre-Critical stage Kant claimed that the world had a beginning in time and is infinite in spatial extent. The universe came into existence through an act of creation on the part of a transcendent deity. In the Critique of Pure Reason these claims were presented as unresolvable antinomies. In the First Antinomy the thesis claims that the world has a beginning in time and is also limited spatially, while the antithesis claims that the world has no beginning and is not limited spatially. In the Fourth Antinomy the thesis claims that an absolutely necessary being belongs to the world as its part or as its cause, while the antithesis claims that no absolutely necessary being exists anywhere in the world, nor does such a being exist outside the world as its cause. However, in his Universal Natural History and Theory of theHeavens, Kant adopted the theistic view (espoused also by Newton and Leibniz) that the cosmos as a whole owes its genesis to a Mosaic deity.

But once God had created time, space, and matter and had endowed them with the very laws that Newton eventually discovered, how did the universe evolve? The term “natural history” in the title of the work indicates that Kant was interested in an evolutionary account of the universe. On this subject he made suggestions that resemble those later set forth by Laplace. Kant claimed that the planets of our solar system arose ffom the condensation of primordial diffused matter. This position contrasts with one claiming that some celestial body passed near our sun and set up cataclysmic actions that caused the planets to be born of our sun through the agency of tidal forces. For Kant the sun, the planets, and their moons all originated by a process of condensation of a diffused mass of widely distributed, thin matter (or, in other words, a nebulous mass of matter). He appealed to the Newtonian attraction and repulsion of the various material particles of the original nebulous mass as being the causes of the solar system’s flattening out into a disk. Other astronomical systems in the universe developed in a similar way.

On Kant’s view the universe is not a static mechanism; it undergoes a fundamental change. Various regions of the universe undergo cyclical changes, being born as just described and dying when the train of planets associated with each star tends to run down and eventually falls back into its respective sun. The sun then heats up with this new matter and eventually explodes into a nebular cloud of matter. Our own developed world is midway between the ruins of the nature that has been destroyed and the chaos of the nature that is still unformed. He claimed that this Phoenix of Nature burns itself only in order to revive from its ashes in restored youth through all the infinity of times and places.

Cosmological theory has made great advances since Kant’s day, but his theory has nonetheless inspired proponents of recent theories. C. F. von Weizsäcker, in his History of Nature (1949) and again in his Gifford lectures for 1959–1960 (entitled The Relevance of Science), has espoused the view that the planets of our solar system were formed from a nebula that surrounded the sun. G. Kuiper of Yerkes Observatory thinks that some denser parts of the nebula condensed further under the influence of their own gravity—the very view that Kant advanced. Kant has also been the object of much criticism. The claim has been made by many that he put forth bold conjectures before the experimental evidence was in and that he even twisted some evidence that was in so that it would conform with his theories. Perhaps he did make too many bold conjectures; but if such conjectures were never made, would science ever make much progress? In his Theory of the Heavens, Kant borrowed the principles of Newton’s system of the world and by a sort of thought experiment used them to extend and deepen man’s picture of the universe. It is a wonder that his though experiment turned out to be so close to much of subsequent cosmological theory.

In the middle of the preface to the Theory of the Heavens, Kant said that it would be possible to grasp the origin of the whole present constitution of the universe by means of mechanical (efficient) causes before it would be possible to grasp the production of even a single herb or a caterpillar by means of mechanical causes alone. He did not categorically deny the possibility that organisms might some day be completely explained mechanically. But in the Critique of Teleological Judgment (1790), Kant did deny the possibility of such an explanation. All the phenomena of inanimate nature can be explained in terms of the motion of matter in space and enduring through time, while for living things such efficient causes are not enough—they must be explained in terms of an end and thus require final causes in addition to efficient ones. In more modern terms, biology, for Kant, cannot in the final analysis be explained solely in terms of physics and chemistry.

Kant was opposed to the Cartesian conception of animal machines; no one can or ever will be able to produce a caterpillar from a given bit of matter. An organism exists as a physical end and is both cause and effect of itself. The parts of an organism, both in their existence and in their from, are possible only by their relation to the whole; furthermore, the parts combine spontaneously to constitute the unity of a whole by being reciprocally cause and effect of their form. A machine has only motive power, while an organized being possesses inherent formative power, which it imparts to raw materials devoid of form.

An oak tree, for example, prepares the matter that it assimilates; and it bestows upon this matter a specifically distinctive quality which mere mechanical nature cannot supply. The tree develops itself by means of a material which the tree itself produces through an original capacity to select and construct the raw material that it derives from nature outside of it. It is as though the tree were itself a supremely ingenious artisan in the building of itself, and the subjunctive mood must be emphasized here. One cannot claim that there really is an end in the thing that is operating in its production; to do so would be to foist an unprovable anthropomorphism on organisms. A person coughs when some water goes down his windpipe while he is taking a drink. Substances heavier than air trigger the coughing mechanism. Such a mechanism is said to have adaptive significance for the organism, in that it enables the organism to live. But it cannot be said that the cough mechanism is intended to keep the organism alive, except on an analogy with artistic production. Final causes are merely regulative concepts which human beings use to comprehend biological organisms, which differ essentially from inorganic entities. One deals with them by means of an analogy with artifacts; it is as though a tree organized itself in a way not unlike the way an artisan forms his product.

Finality is read into the facts, and teleological principles are nothing but heuristic maxims whose justification resides in their fruitfulness in providing systematic comprehension of living organisms. When finality is so viewed, the question of whether, in the unknown inner basis of nature itself, efficient causes and final ones may cohere in a single principle is left open. Accordingly, teleology and mechanism in no way contradict one another, as Kant explains with the greatest epistemological subtlety in §77 of the Critique of Teleological Judgment. Efficient causes are concepts that determine (and do not merely regulate) our knowledge of phenomena. Therefore, the investigations of biology must be pushed as far as possible in the direction of efficient causes; the simple mechanism of nature must be the basis of research in all investigation of biological phenomena. But this does not mean that such phenomena are possible as entities solely on the basis of efficient causation. The principle of teleology directs one to continue research as far as possible on the basis of efficient causation. The processes of digestion are not understood by any appeal to the principle that such processes enable the organism to live and thrive. Such processes are understood by accounting for the passage of chemical substances through membranes, but why such membranes permit the passage only of certain chemical substances and no others may not be able to be accounted for on the basis of mechanical causes alone.

Efficient causes are progressive, while final causes are reciprocal. In the former the connection constitutes a series (the so-called causal chain) which is always such that the things which, as effects, presuppose other things as their causes cannot themselves also be causes of these other things. Final causes are that the series involves regressive as well as progressive dependency (a house is the cause of one’s receiving rent money, but the house was built in the first place so that one might receive such rent). Kant calls efficient causes a nexus of real ones and final causes a nexus of ideal ones. The former are also said to determine our knowledge of phenomena. He treats of efficient causation in the Second Analogy of Experience in the “Transcendental Analytic” of the Critique of Pure Reason, where he distinguishes between a subjective connection of cognitions and an objective connection of them. One walks into a warm room and sees a glowing stove. As far as the subjective order of cognitions is concerned, one first feels warm and only later spies the stove concealed behind a screen in the corner. But yet one says that it is the stove which causes the room to be warm and not that it is the warm room which causes the stove to glow. In order to have knowledge through perceptions, one must connect them in their objective time relations. There is no necessity in the subjective order of congnitions, but there certainly is in one’s synthetic reorganization of that order. If event A (glowing stove) precedes event B (warm room) objectively, then one must think of A as preceding B or else be wrong. It makes no difference whether one perceives A first and then B, or B first and then A in his subjective consciousness.

Kant worked out his theory of efficient causation largely in opposition to Hume’s position on the subject. Hume claimed that there are three conditions which two events must fulfill in order for one event to be considered the cause of another: the cause precedes the effect in time, cause and effect are contiguous in space, and cause and effect are found constantly conjoined in experience. Kant leveled his attack mainly against the third condition, but other people have found objections to the first two conditions as well. In the realm of colliding billiard balls, the cause does temporally precede the effect; but in the case of boiling water, the boiling occurs just when the water reaches 100° c.; and so cause and effect are simultaneous. As for spatial contiguity, the moon through empty space attracts the waters of the earth’s seas and oceans to produce tides. In the case of such action at a distance, there is no contiguity in space. As for constant conjunction, some have pointed out that night and day are always conjoined, but night is not the cause of day. Kant objected to the third condition by claiming that on Hume’s view there is no way to distinguish the subjective order of cognitions from the objective order of them.

Hume held that the idea of necessary connection between cause and effect arises when we develop a habit of association from a repeated subjective succession of perceptions (fire always burns). He thus based causation entirely on sensible experience. In contrast, Kant claimed that the objective reordering of the subjective succession of cognitions (which is based on sense perception and imagination) is actually a synthetic reorganization of the a posteriori order of perception. This synthetic reorganization is an a priori act of the human understanding. In other words, the causal ordering of cognitions is an act of the intellect that is brought to experience (or, even better, that makes experience) and is not an ordering derived from experience (as Hume claimed). For Kant in his Critical period the pure concepts of substance, cause, possibility, existence, and necessity were a priori concept that are coterminous with the pure forms of intuition, time and space. Experience is the result of the synthetic activity of the intellect by means of such pure concepts in organizing empirically given sense perceptions that are arrayed in time and space. The history of theories of efficient causation did not end with Kant. The controversy between the a posteriori and a priori views broke out again in the middle of the nineteenth century with the debates between John Stuart Mill and William Whewell. Mill disagreed with Kant, while Whewell agreed. In the twentieth century Bertrand Russell and A. C. Ewing have continued teh debate.

Time, space, matter, force, motion, cause—the major portions of Kant’s philosophy of science have now been examined in terms of these key concepts. This philosophy is rationalistic in comparison with the views of such a later thinkers as Mill and Russell but seems almost empiricistic in comparison with such of Kant’s immediate German idealist successors as Fichte, Schelling, and Hegel. According to Kant, the human mind supplies the form of experience (time, space, and the categories of the understanding); but the content of experience is empirically given in sensation from a source outside the human self (the real material world). The German idealists claimed that the self is the source not only of the form of experience but also of its content. On this view nature becomes a sort of external symbol or image of the self. Nature is the self taken as object. Accordingly, Schelling thought that the whole of physics could be spun out of the mind itself. If so, what need is there for experiment?

The accusation of armchair scientist which Erich Adickes leveled at Kant might more appropriately be directed against these Romantic idealists. Apart from the most general, formal aspects of nature (matter is a continuum and not an interruptum, there is no absolute motion, the changes in nature are causally connected, and so on), all the rest of nature in its particular aspects (temperature of Venus, strength of the gravitational pull of the moon, the cause of diabetes, and so on) must for Kant be learned by experiment. To be sure, he was more interested in the formal aspects than in the particular, but he never claimed that the particular aspects could be dealt with in any way other than by observation and experiment.

The Kantian emphasis on causality in conformity with law and on mathematical rigor in conformity with experience, contributed important elements to the philosophical depth and seriousness that animated the German scientific movement from the middle of the nineteenth century on and that distinguished it from the scientific traditions of other cultures. Two quotations from classic texts will lllustrate the way in which creative German scientists formed their expectations of what a scientific explanation does from their knowledge of Kant. The first, concerning physics, is from Helmholtz’s Ueber die Erhaltung der Kraft (1847), the famous memoir on the conservation of energy which in its philosophical aspect Helmholtz attributed expressly to Kant’s inspiration:

The final goal of the theoretical natural sciences is to discover the ultimate invariable causes of natural phenomena. Whether all processes may actually be traced back to such causes, in which case nature is completely comprehensible, or whether on the contrary there are changes which lie outside the law of necessary causality and thus fall within the region of spontaneity or freedom, will not be considered here. In any case it is clear that science, the goal of which is the comprehension of nature, must begin with the presupposition of its comprehensibility and proceed in accordance with this assumption until, perhaps, it is forced by irrefutable facts to recognize limits beyond which it may not go [from Selected Writings of H. L. F. von Helmholtz, Russell Kahl, ed.(Middletown, Conn., 1971), p. 4].

The second quotation, concerning biology, is from Schwann’s Mikroskopische Untersuchungen über die Uebereinstimmung in der Struktur und dem Wachstume der Tiere und Pflanzen (1839), the equally famous treatise concerning the cellular structure of the living organism. It concludes with a regulatory discussion of methodology deriving from the Kantian distinction between mechanistic and teleological explanation in the Critique of Teleological Judgment;

Teleological views cannot be discarded for the time being since not all phenomena are to be clearly explained by the physical view. Discarding them is not necessary, however, for a teleological explanation is admissible if and only if a physical explanation can be shown to be unattainable. Certainl y it brings science closer to the goal to try at least to formulate a physical explanation. I should like to repeat that when I speak of a physical explanation of organic phenomena, I do not necessarily mean that an explanation in terms of known physical forces like that universal resort, electricity, is to be understood, but rather an explanation in terms of forces which operate like physical forces in service to strict laws of blind necessity, whether or not such forces be found in inorganic nature [Ostwalds Klassiker der Exacten Wissenschaften (Leipzig, 1910), p. 187].

In general, it was in service to the rigorous idealism of Kant that leaders of the first great geneation of German science–including Müller. Schleiden, Mayer, du Bois-Reymond, and Virchow—repudiated the literary and speculative Naturphilosphie of the Romantic idealists, which they dismissed as an episode of cultural wild oats in the adolescence of the German spirit.

In the twentieth century Kant’s thought has not had the direct influence on experimental scientists that it had earlier on Helmholtz and Schwann. But in the philosophy of science Ernst Cassirer gave a Kantian interpretation of the metaphysical and epistemological foundations of relativity in his Einstein’s Theory of Relativity Considered From the Epistemological Standpoint and of quantum theory in his Determinsism and Indeterminism in Modern Physics. C. F. von Weizsäcker gave a Kantian interpretation of quantum theory in his The World View of Physics.


I. Original Works. The best ed. of Kant’s works is Kants gesammelte Schriften, published by the Royal Prussian Academy of Sciences (Berlin, 1902– ). This ed. already runs to some 27 vols. and, when complete, will contain not only all the published works, letters, and fragments but also all the extant transcripts of lectures.

English translations of some of Kant’s works mentioned in this essay follow, in the order of the publication of the orginal German works: Universal Natural History and Theory of the Heavens, trans. by W. Hastie (Ann Arbor, Mich., 1969), a repr. of Hastie’s Kant’s Cosmogony (Edinburgh, 1900); Kant’s Inaugural Dissertation and Early Writings on Space, trans. by J. Handyside (Chicago, 1929); Critique of Pure Reason, trans. by Norman Kemp Smith, 2nd ed., rev. (London, 1933); Metaphysical Foundations of Natural Sience, trans. by James W. Ellington (Indiana-polis, 1970); Critique of Teleological judgement, trans. nby J. C. Meredith (Oxford, 1928).

II. Secondary Literature. The best biography of Kant is Karl Vorländer, Immamuel Kant, der Mann und das Werk, 2 vols. (Leipzig, 1924). The best in English is J. W. H. Stuckenberg, The life of Immamuel Kant (London, 1882).

The literature about Kant is enormous. Erich Adickes, “Bibliography of Kant,” in The Philosophical Review (1893), lists 2,832 titles and goes only to 1802. The Literaturzeichnisse preceding Kant’s various writings on science and the philosophy of science that are in vol. VII of Karl Vorländer’s ed. of King’s works in the Philosophische Bibliothek series, entitled Kants sämtliche Werke, 10 vols. (Leipzig, 1913–1922), are recommended for books specifcally on King’s works on sciene and the philosophy of science.

A brief list of the works especially relevant to this essay is Erich Adickes, Kants Opus postumum, which is KantStudien, supp. vol. no.50 (Berlin, 1920); and Kant als Naturforscher, 2 vols. (Berlin, 1924–1925); Ernst Cassirer, Substance and Function and Einstein’s Theory of Relativity (Chicago, 1923), pp. 347–456; and Determinism and Indeterminism in Modern Physics (New Haven, 1956); James W. Ellington, introduction and supplementary essay entitled “The Unity of Kant’s Thought in His Philosophy of Corporeal Nature,” in the trans. of the Metaphysical Foundations of Natural Science (see above); Irving Polonoff, Force. Cosmos, Monads, and Other Themes of Kant’s Early Thought, which is Kant-Studien, supp. vol. no. 106 (Bonn, 1972); Lothar Schäfer, Kants Metaphysik der Natur (Berlin, 1966); and C. F. von Weizsäcker, The World View of Physics (Chicago, 1952); and The Relevance of Science (London, 1964).

James W. Ellington

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KANT, IMMANUEL (17241804), German philosopher. Kant was born in Königsberg, a provincial town in East Prussia. He grew up in a religious family of relatively low social status. His father was a saddler, and both his parents were dedicated members of the Pietist movement, which stressed the interior devotion of the heart in opposition to the prevailing Lutheran practice of external observances. The spirit of Pietism pervaded not only Kant's family but also the Collegium Fridericianum, a local school, where he received his early education from 1732 to 1740.

In 1740 Kant entered the University of Königsberg, where he studied science and philosophy for six years. After graduation, he earned his living as a private tutor for a number of East Prussian families. During this period he kept up his studies and earned his master's degree at the university in 1755, which allowed him to teach as a privatdocent, a private lecturer accepted as a member of the faculty without compensation from the university. He occupied this financially precarious and academically undistinguished position for fifteen years. In 1770 he was appointed professor of logic and metaphysics.

While holding this position, Kant produced a stream of masterpieces. His best-known works are his three critiques: the Critique of Pure Reason (1781), the Critique of Practical Reason (1788), and the Critique of Judgment (1790). These three volumes expound Kant's critical idealism, or critical philosophy, which has also been known as Kantianism. Kantianism was the first phase of German Idealism, which gained fuller development in the writings of Johann Fichte (17621814), Friedrich Schelling (17751854), and G. W. F. Hegel (17701831). Kant's religious ideas not only constitute essential features of his critical philosophy but also play a pivotal role in the transition from his critical idealism to the absolute idealism of his intellectual successors.

Kantianism as a Worldview

Kantianism was an attempt to reconcile British empiricism and continental rationalism. British empiricism had been developed by a succession of British and Scottish philosophers, namely, Thomas Hobbes (15881679), John Locke (16321704), George Berkeley (16851753), and David Hume (17111776). Continental rationalism had been advocated by René Descartes (15961650), Gottfried Leibniz (16461716), and Christian Wolff (16791754). During his formative years, Kant learned his philosophy from Leibnizians and Wolffians, but he later came to appreciate the importance of empiricism, especially Hume's theory of ideas.

The central point of the dispute between rationalists and empiricists was the theory of ideas. Since all our ideas are derived from sensation, the empiricists maintained, the objects of sensation are the only proper objects of knowledge. In opposition to this view, the rationalists argued that some of our ideas are not derived from sensation but are innate to reason. They further claimed that these innate ideas give us a knowledge of supersensible reality such as God. The idea of a supersensible reality, although espoused by some early empiricists, became unpopular with the later empiricists, because they considered it incompatible with empiricism. This later tendency of empiricism amounted to recognizing sensible reality, or the physical world, as the only reality. Thus the dispute that had begun with the epistemological issue concerning the origin of ideas came to have the ontological implication of admitting or not admitting any reality beyond the domain of sensation.

Kant's Critique of Pure Reason is a critical assessment of these two contending views. He holds that there are two kinds of ideas: those derived from sense and those innate to reason. The latter are the a priori elements of cognition; the former are its a posteriori elements. These two are equally indispensable for human knowledge. Kant is emphatic on the mutual dependence of sensibility and understanding: "Percepts without concepts are blind; concepts without percepts are empty." Although the domain of knowledge is limited to the domain of sensation, as the empiricists claimed, Kant argues, knowledge of sense objects requires the use of a priori concepts such as the concept of cause and effect. He derives twelve a priori concepts from twelve forms of judgment and calls them the categories of understanding. He uses the categories to construct a priori principles of understanding, which function as the framework for organizing the objects of sensation.

This epistemological compromise between rationalism and empiricism has the following ontological consequence: Kant maintains that the objects of sensation are not reality itself (things-in-themselves) but its appearance. He bases this claim largely on his argument that space and time are not objective entities but subjective forms of intuition, that is, the manner in which human beings are given objects of sensation. Since all objects of sensation are given through space and time, Kant holds, they cannot be objective realities. They are only appearances to us. Kant calls these appearances "phenomena" and the things-in-themselves "noumena."

Unlike phenomena, noumena are not located in space and time; nor are they given as objects of sensation. They are the supersensible realities. That the domain of knowledge is limited to the world of phenomena means that we can never know the true reality but only its appearances. That we can have no knowledge of noumena, however, does not mean that we have no ideas about them. Kant maintains that we have a priori ideas about the supersensible reality. But to have these ideas is not to know the world of noumena, because there is no way of proving their truth or falsity.

In Kant's view, knowledge is inseparable from the power of demonstrating the truth or falsity of an idea, and that power is inexorably limited to the domain of sensibility. For this reason, knowledge is limited to the world of phenomena. The rationalists have assumed that the truths of a priori ideas can be demonstrated by rational arguments alone, that is, without appealing to sensibility. But rationalist arguments divorced from the constraint of sensibility can produce only sophistical illusions and confusions, according to Kant. He gives the name "transcendental dialectic" to the pseudoscience constituted by those sophistical arguments, because they are dialectical arguments transcending the domain of sensibility.

Kant recognizes three branches of transcendental dialectic: transcendental psychology, transcendental cosmology, and transcendental theology. These three are supposed to prove the immortality of the soul, the freedom of the will, and the existence of God. In the Critique of Pure Reason, Kant provides a systematic examination of their arguments and exposes their common error, namely, the error of employing a priori concepts beyond the domain of sensibility.

The immortality of the soul, the freedom of will, and the existence of God are three of the central dogmas in many religions. That none of them can be proved, however, should not be mistaken to mean that they can be disproved. Kant is emphatic on this point. A transcendental assertion can neither be proved nor be disproved, because sensibility is essential not only for proofs but also for disproofs. Hence the three religious dogmas can still be regarded as possible truths of the supersensible reality. As such, they can be accepted in faith.

Kant demarcates matters of faith from matters of fact. The latter are the objects of knowledge; the former are the objects of belief. The objects of knowledge are situated in the world of phenomena; the objects of faith belong to the world of noumena. The objects of faith transcend the domain of sensibility, while the objects of knowledge are immanent in it. Although theoretical reason cannot settle the question of accepting or rejecting the objects of faith, Kant says, practical reason has a way of ruling over their admissibility.

Kantianism as a Moral View

Practical reason is the rational faculty concerned with human conduct, and a critical examination of this faculty is given in his second critique, the Critique of Practical Reason. Kant recognizes two mainsprings for human conduct: the will and the inclination. The inclination is the working of our desires and feelings, which are subject to the causal laws of the phenomenal world. The will is the rational faculty for moral actions. Unless the freedom of this faculty is presupposed, Kant says, it makes no sense to talk of the moral worth of human conduct. Since freedom is impossible in the phenomenal world of causal necessity, it can be accepted only as an entity belonging to the noumenal world. Kant calls the noumenal world the domain of freedom and the phenomenal world the domain of necessity. Thus he installs the noumenal world as the practical ground for morality and the freedom of the will as the first postulate (presupposition) of practical reason.

Besides the postulate of freedom, Kant says, two other postulates are demanded by morality: the existence of God and the immortality of the soul. The immortality of the soul is required for moral perfection. Our inclination has the natural propensity to go against the moral dictates of pure reason, and our moral perfection can be achieved by transforming this natural propensity into the willing obedience to the moral law. Since this moral transformation of the soul is infinitely time-consuming, it can be accomplished only if the soul continues to live after the death of its body. For this reason, Kant says, the postulate of the immortality of the soul is dictated by the practical ideal of moral perfection.

In Kant's ethics, the ideal of moral perfection is inseparably connected with another practical ideal, the notion of the complete good (summum bonum ). Kant defines it as the harmony of moral perfection and happiness (natural good). He regards moral perfection as the absolutely necessary condition for rendering human beings worthy of happiness. In this world, however, happiness can be denied to a person morally worthy of it, while it can be given to a person morally unworthy of it. The dispensation of happiness in proportion to each person's moral worth is their harmony, that is, the ideal of the complete good. This ideal can, Kant maintains, be fulfilled only by God in the other world. This is the third and the final postulate of practical reason.

Kant's third postulate has sometimes been known as the moral proof for the existence of God, and as such it has been the object of many disputes and misunderstandings. But to call it a proof is highly misleading; a "proof" for the existence of God generally means the demonstration or assurance of his existence. In Kantianism, as we have already seen, demonstration or assurance can be given only for the objects of the phenomenal world. Therefore the reasons Kant gives for the existence of God cannot constitute a proof. It is only a postulate. Whereas a proof can give certainty or assurance, a postulate can give only possibility, a supersensible ground for hope.

Kant's notion of rational postulates is inseparable from his ideal of practical rationality. To regard the harmony of moral and natural goods as an ideal of practical reason means that the world in which this ideal is fulfilled is a rational one and, conversely, that the world in which it is not fulfilled is an irrational one. It is impossible to find out whether our world is ultimately rational or irrational in this regard. As rational beings, however, we can, for practical purposes, opt and hope for the possibility that our world is ultimately rational. If this possibility is to be true, Kant argues, there must be a God who assures the harmony of moral and natural goods for every moral being. This is all that is meant by this and other postulates of practical reason.

Kant's Conception of God and the Religious

In Kant's philosophy, God does not stand as a power that has its own laws and commands different from the moral law and its dictates. What God demands from ethical subjects is none other than what is dictated by moral reason. To do the will of God is to perform the duties of the moral imperative. There is no way to please God other than to be morally perfect. To be religious is to be moral; to be moral is to be religious. As far as human behavior is concerned, morality and religion are functionally identical, and their functional identity is expressed in Kant's statement that religion and God are internal to morality.

Kant's internalism, as he admits, goes against the traditional view that assumes an external relation between morality and religion. In general, the traditional religions portray God as a powerful being, whose will is independent of our will, whose commands can override even our moral dictates, and whose favor can be sought by special rituals and devotions. In short, the traditional religions stand on the existence of powers and values external to the powers and values of morality. Kant rejects such externalism because it is incompatible with the autonomy of practical reason.

In Kant's view, externalism is the anthropomorphic misconception of God and his relation to us, that is, the error of understanding God as someone like a powerful human being who demands our service and devotion. This misconception lies behind the religions of what Kant calls "cultus externus." These religions impose on their devotees a set of obligations or observances that consists of prayers, rituals, services, and various prohibitions. Furthermore, the gods of these religions are assumed to be pleased or displeased by the performance or nonperformance of these religious duties. Most of these religions have specially ordained experts called priests, ministers, or shamans, who have the power of officiating and facilitating the performance of religious duties.

Cultus externus, Kant insists, makes no sense to anyone who correctly understands the nature of God as the most perfect being, that is, omniscient, omnipotent, and, above all, morally perfect. It makes no sense to render any service to such a being, because he is in need of nothing and can derive no benefit from our services. Even the praise of his perfection cannot add anything to his perfection any more than flattery can to his honor. God does not need our prayers to find out what we need. Nor can he be moved by our supplication, because his mind is governed only by moral dictates. The cultus externus can fulfill none of the religious functions that it has been assumed to fulfill.

Kant uses the label "natural religion" to designate his view of religion, because it can be fully comprehended by the natural power of human reason, that is, without the aid of supernatural revelation. Kant's idea of natural religion may appear to reduce religion to morality. But he insists that natural religion retains all the essential features of traditional religions. In his view, those features are the moral attributes and functions of the supreme being, as the holy lawgiver, the benevolent ruler, and the just judge. Any other attributes of God such as omniscience, omnipotence, and omnipresence are only supplementary to his moral attributes; they are the requisite conditions for discharging his moral functions.

Kant argues that Christianity is the only moral religion, while the others are servile religions. The central function of servile religions is to curry favor from the supernatural powers; they place human beings in a servile relation to those powers. This servile relation has, Kant holds, been transformed into a moral one by Jesus of Nazareth. Jesus transformed the "old" law of Moses, the rules for external observance, into the "new" law, the rules for internal disposition. Kant finds Jesus' moral interpretation of religious life most conspicuously in his Sermon on the Mount, and he reads its concluding remark"Therefore be perfect, as your heavenly father is!"as an exhortation for moral perfection.

In Religion within the Limits of Reason Alone (1793), Kant offers his moral interpretation of Christian dogmas. The dogma of original sin concerns our innate propensity to do evil, which is to flout the maxims of duty and to succumb to the maxims of inclination. Kant regards it as a superstition to believe that this propensity was generated by Adam's fall from grace and then passed on to his posterity. On the contrary, Kant holds that the innate propensity to go against the moral law is in the very nature of man. No doubt, original human nature is said to be good. This original goodness, however, is not incompatible with the innate propensity to do evil. The original goodness of man means the freedom to obey the moral law by disciplining and mastering inclinations. Hence, original goodness and the innate propensity to evil are two essential features of every human being.

Kant interprets the incarnation of God in Christ not as a miracle of the supernatural order but as the manifestation of a moral ideal. As moral agents, he says, all of us have the ideal of a morally perfect human being. Such an ideal, if ever realized in this world, can be called an incarnate God, because the ideal in question belongs to pure practical reason, whose dictates are one with the dictates of God. Kant calls the ideal of moral perfection the archetype of moral life. But this archetype, he insists, cannot be identified with Jesus Christ himself. For he is only an instance or example, while the archetype belongs to all of us as agents of practical reason.

The relation of archetype and example, Kant says, is misrepresented in the traditional dogma of the incarnation, which exalts Jesus as a member of the Holy Trinity. He regards the dogma of the Trinity as theoretically incomprehensible and practically unserviceable. If the Son of God is so exalted as to stand above all human temptations and struggles, he is too remote from our existence to serve as a useful model. The value of the Son of God as our practical model lies in his essential identity with all human beings, and every human being who strives to achieve moral perfection can be called a son of God, a man well-pleasing to God.

Kant interprets the kingdom of God as an ethical commonwealth, a community of moral agents each of whom treats the other as an end-in-itself by obeying the moral law. He distinguishes the ethical commonwealth from the political commonwealth by virtue of the former's freedom from coercion. Whereas the power of coercion is indispensable for the maintenance of a political commonwealth, the freedom of the will is sufficient for the administration of an ethical commonwealth. The constitution of such a harmonious community, Kant says, becomes possible only through the moral rebirth of its members, which involves the radical transformation of their hearts from the propensity to follow inclination into the willing obedience to the moral law, that is, through conversion. The same moral transformation is required for the admission to the ethical commonwealth.

Kant shows special caution in handling the claims of supernatural revelation. He rejects the claim that revelation has the authority of discovering and authenticating the supernatural truths inaccessible to human intelligence. He also rejects the view that revelation is totally gratuitous with respect to the discovery of religious truths. Although the truths of natural religion can be discovered by natural reason, revelation makes easier their discovery and propagation. Since he recognizes only the practical value of expedition, he rejects the traditional distinction between natural and revealed religion. As in Christianity, he says, a natural religion can be a revealed one.

Since natural religion belongs to the pure practical reason, Kant asserts the unity of all religions. There is only one true religion, he says, although there can be many different faiths. He distinguishes the particular ecclesiastical faiths from pure religious faith. Whereas pure faith consists of the ideals of practical reason, the particular faiths are the manifestations of those ideals through the historically instituted churches. Since the formation and development of those institutions have been influenced by historical contingencies, Kant holds, the ecclesiastical faiths are bound to show their differences. Nevertheless, he is confident that they can still display the unity of pure religious faith insofar as they are faithful to their original ideals.

Kant's Critics and His Influence

Kant's idea of natural religion provoked the charge among his contemporaries that he was a Deist. Deism was the view, prevalent among the scientific-minded intellectuals of the eighteenth century, that God does not intervene in the running of the universe because it has been placed under the working of immutable laws since its creation. Kant categorically denied the charge of being a Deist and attributed it to the misrepresentation of his position.

The misrepresentation in question was largely due to Kant's skeptical attitude toward miracles, God's interventions par excellence in the running of the world. Because miracles contravene the laws of nature, they cannot be reconciled with the use of reason. Both in theoretical and practical functions, human reason appears crippled in the presence of miracles. Furthermore, he says, miracles are not essential for the functions of true religion, because these functions can stand securely on moral beliefs alone. In fact, any demand for miracles as the authentication of religious beliefs betrays the lack of firm faith in the authority of moral commands, which are engraved upon the heart of man through reason. Because of this, Kant says, Christ rebuked the miracle-seekers: "Unless you see signs and wonders, you will not believe" (Jn. 4:48). In spite of these reservations about miracles, Kant categorically refused to impugn their possibility or reality.

Another charge against Kant was that he compromised his doctrine of moral autonomy by retaining the traditional doctrine of grace. Grace, for Kant, means God's help; it presupposes man's weakness, dependence, and heteronomy. The Pietists under whose influence Kant had grown up stressed the indispensability of grace and tended to take a passive attitude toward life. Kant rejects this passive attitude and praises the positive value of active efforts in moral life. Nevertheless, he admits the possibility that even our best efforts may fail to secure moral perfection. In that event, he says, we can hope that God will, in his wisdom and goodness, make up for our shortcomings.

His critics have pointed out that man is not a truly autonomous moral agent if even his best moral efforts are not enough to secure his moral perfection. They have further argued that Kant's notion of moral autonomy is also incompatible with his notion of the complete good. In their view, the intimate connection between worthiness and happiness makes morality too dependent on the idea of happiness, which is admittedly outside the control of a moral agent. Kant had guarded himself against this charge by stressing that the connection in question was a matter of belief rather than knowledge. Even if it is only a belief, his critics have maintained, it compromises the notion of moral autonomy as long as it is acted upon in the practical world.

Perhaps the most serious charge against Kant was addressed to his demarcation between phenomena and noumena. At the time he was concluding his second critique, the Critique of Practical Reason, he was not terribly disturbed by this criticism. So he confidently singled out the starry heavens above and the moral law within as two objects of awe and admiration, respectively representing the world of phenomena and the world of noumena. This observation was intended to mark the end not only of the second critique but of his entire critical enterprise. For he believed that his two critiques had fulfilled his ambition of critically assessing the two worlds of phenomena and noumena.

Shortly thereafter, however, Kant became preoccupied with the question of transition and mediation between the two worlds. Although moral precepts belong to the noumenal world, they can be realized in the phenomenal world. Kant found it difficult to explain the transition from the world of precepts to the world of practice, because one was supposed to be governed by necessity and the other by freedom.

In order to resolve this problem of transition, Kant wrote his third critique, the Critique of Judgment, and introduced reflective judgment as the faculty of mediation between the two worlds. But his theory of mediation was far from convincing, and most of his intellectual heirs resolved his problem by collapsing his two worlds into one. This post-Kantian development in German idealism made it impossible to retain Kant's postulates of immortality and the other world, because there was only one world left.

The fusion of Kant's two worlds into one was the climax of the progressive secularization that had begun in the Renaissance. Kant played a pivotal role in this development. His demarcation between phenomena and noumena was a modification and retention of the medieval demarcation between the natural and the supernatural orders. Unlike the medieval demarcation, however, Kant's did not completely coincide with the demarcation between this world and the other world. Kant made the transcendent noumenal world functionally immanent for moral life, thereby initiating the descent of the transcendent reality to the immanent level. The post-Kantians completed this process of descent and converted Kant's theism into pantheism. Kant's transcendent God became their immanent force in history.

The resulting pantheism also resolved the tension in Kant's notion of human autonomy. Although he claimed autonomy and independence for moral life, he acknowledged heteronomy and dependence for happiness. He stressed this admixture of dependence and independence in his notion of the complete good and the postulate for the existence of God. But this admixture was unacceptable to his successors, because they insisted on the total autonomy of human reason. The totally autonomous human reason became indistinguishable from the immanent God, and the two-in-one came to be called the "Absolute Spirit" by Hegel. With Kant, religion and morality became functionally identical; with Hegel, God and man were given their ontological identity.

See Also

Deism; Empiricism; Free Will and Predestination; Pietism; Proofs for the Existence of God.


Kant's Works in English Translation

Critique of Judgement. Translated by J. C. Meredith. 1928; reprint, London, 1973.

Critique of Practical Reason. Translated by Lewis White Beck. Chicago, 1949. Kant's preliminary view of this subject is given in his Foundations of the Metaphysics of Morals, translated by Lewis White Beck (Chicago, 1949).

Critique of Pure Reason. Translated by Norman Kemp Smith. New York, 1929. An abridged version is available in Kant's Prolegomena to Any Future Metaphysics, edited by Lewis White Beck (Indianapolis, 1950).

Lectures on Ethics. Translated by Louis Infield. London, 1979. These lectures are not from Kant's own writings but from his students' notes.

Religion within the Boundaries of Mere Reason. Translated and edited by Allen Wood and George Di Gionvanni (Cambridge, 1998).

Works on Kant's View of Morality and Religion

Beck, Lewis White. A Commentary on Kant's Critique of Practical Reason. Chicago, 1960.

Cassirer, Ernst. Kant's Life and Thought. Translated by James Haden. New Haven, 1981. This is perhaps the most comprehensive introduction available in English to Kant's life and philosophy. A shorter general introduction to his philosophy can be found in Stephan Körner's Kant (1955; reprint, New Haven, 1982) and in Ralph C. S. Walker's Kant (Boston, 1978).

Collins, James D. The Emergence of Philosophy of Religion. New Haven, 1967. This volume provides a good account not only of Kant's conception of religion but also of what comes before and after Kant's conception, especially Hume's and Hegel's ideas on the issue.

England, F. E. Kant's Conception of God. New York, 1929.

Green, Ronald Michael. Religious Reason: The Rational and Moral Basis of Religion. New York, 1978.

Paton, Herbert J. The Categorical Imperative: A Study in Kant's Moral Philosophy. Chicago, 1948.

Silber, John R. "Kant's Conception of the Highest Good as Immanent and Transcendent." Philosophical Review 68 (1959): 469492.

Silber, John R. "The Moral Good and the Natural Good in Kant's Ethics." Review of Metaphysics 36 (December 1982): 397437.

Webb, Clement C. Kant's Philosophy of Religion. Oxford, 1926. Wood, Allen W. Kant's Moral Religion. Ithaca, N. Y., 1970.

T. K. Seung (1987 and 2005)

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German philosopher of outstanding ability and influence; b. Königsberg, East Prussia, April 22, 1724; d. there, Feb. 12, 1804. Kant's father was a harness maker of ability. The spiritual climate of his family was that of orthodox Lutheranism intermingled with pietistic elements. Kant himself never traveled farther than the province of Königsberg; he left the city but seldom, and then only for short stays in the country. He began his graduate studies in 1740 at the University of Königsberg and earned his doctorate in philosophy there in 1755. His Habilitationsschrift at the university was a work on the first principles of metaphysics. He remained an instructor until 1770, when he was appointed ordinary professor of logic and metaphysics. Kant was popular and much esteemed as a professor at the university; after 1781, in fact, he came to be recognized as one of the most famous men of his time. His way of life was always simple and rigorously ordered; he spent his days working seriously and with a sense of duty that may be characterized as stoic. Although he had no family of his own, he had the inclination and the time for sociability, and in spite of a weak physical constitution he lived to old age.

Development and Works. The line development of Kant's philosophical activity may be seen in his works. There is a clear contrast between two periods: from the years 1769/1770 and on his precritical thought gradually gave way to his critical philosophy. During the precritical period Kant mainly followed the thought patterns of the rationalist Enlightenment, proceeding along the paths traced by G. W. leibniz and C. wolff. At the same time he somehow transcended this movement by taking into account the irrationalistic philosophy of emotions that he had learned from the work of J. J. rousseau. Again, he manifested strong interest in mathematics and the natural sciences; here he had high regard for Sir Isaac Newton, whom he considered his master. Chief among the works of this period are his Natural History and Theory of the Heavens (Königsberg 1755; tr. W. Hastie in Kant's Cosmogony, Glasgow 1900) and Der einzig mögliche Beweisgrund zu einer Demonstration des Daseins Gottes (Königsberg 1763). In the latter work he attempts to develop a proof of God's existence that is completely a priori. This proof gives a new foundation for causal thinking and thus develops the true sense of the cosmological and teleological proof of God's existence. However, the rational surface current lost some of its force because of the irrational undercurrent. The following words are indicative of this trend: "It is absolutely necessary to convince oneself of the existence of God; but it is not equally necessary to demonstrate it." This formulation already contains a foreboding of the critical period.

In the second phase of Kant's philosophical development, the irrational element gains the upper hand and rational metaphysics disappears. As Kant himself expresses it, he was roused from his "dogmatic slumber" through Hume's remarks on the law of causality. D. hume maintained that the necessity that, according to traditional metaphysics, links the effect to its cause and ultimately leads to the first cause cannot be inferred either from the connection of concepts (a priori) or from experience (a posteriori). This position was taken up by Kant, who extended the argument to all necessary connections between concepts and, in so doing, raised the general question as to the possibility of experience and science and, above all, of metaphysics. Kant endeavored to solve this problem in his main work, the Critique of Pure Reason (Riga 1781, 2d ed. 1787; tr. N. K. Smith, 2d ed., London 1933). The Prolegomena to Any Future Metaphysics (Riga 1783; tr. P. Carus, rev. L. W. Beck, New York 1950) gives a short introduction and a synthetical presentation of this work. To the investigation of the theoretical realm (the field of knowing) Kant added the study of the practical realm (the field of moral action). Thus his main ethical work was titled the Critique of Practical Reason (Riga 1788; tr. L. W. Beck, Chicago 1949); three years previously, as a precursor to this, Kant had published his Groundwork of the Metaphysics of Morals (Riga 1785; tr. H. J. Paton, London 1950). His Critique of Judgment (Berlin 1790; tr. J. H. Bernard, 2d ed. London 1931) is intimately connected with the two great critiques just mentioned. It deals with the faculty that plays an intermediary role between knowing and willing and that he identifies as judgment and feeling in one; its contents show that it deals with aesthetics and critical teleology. To the critique of religion Kant devoted his Religion within the Limits of Reason Alone (Königsberg 1793; tr. T. M. Greene and H. H. Hudson, Glasgow 1934). His Metaphysics of Ethics (Königsberg 1797; tr. J. W. Semple, 3d ed. Edinburgh 1886) deals with problems of ethics and the philosophy of law. Finally, the Opus postumum (Tübingen 1920, 1938) gives a valuable glimpse into Kant's ultimate development and into the transition from his thought to German idealism.

Philosophy of Criticism. Criticism is Kant's original achievement; it identifies him as one of the greatest thinkers of mankind and as one of the most influential authors in contemporary philosophy. But it is important to understand what Kant means by criticism, or critique. In a general sense, the term refers to the cultivation of reason by way of "the secure path of a science" (B xxx). More particularly, its use is not negative but positive, a fact that finds expression in the famous sentence: "I have therefore found it necessary to deny knowledge in order to make room for faith" (B xxx). Correspondingly, its negative use consists in not allowing oneself to "venture with speculative reason beyond the limits of experience" (B xxiv). Thus criticism removes the decisive hindrance that threatens to supplant or even to destroy the "absolutely necessary practical employment of pure reason in which it [pure reason] inevitably goes beyond the limits of sensibility" (B xxv). Accordingly, the critique guarantees a secure path for science by confining speculative reason to its own limits and by giving practical reason the complete use of its rightsrights that thus far had not been recognized.

Place in the History of Ideas. Kant, being confronted with the two extremes of rationalism and empiricism, set for himself the task of creating a synthesis between them. As he saw it, rationalism operates in the sphere of innate ideas, with their analytical and therefore aprioristic necessity; this necessity, however, is not based on experience and consequently does not apply to reality itself. On the other hand, empiricism starts completely from experience and thus (it seems) from reality, but it arrives only at a posteriori and therefore synthetic statements that lack necessity. Kant sought to unite the concept and experience; he sought a necessity that extends to the order of objective reality and an order of objective reality that in itself contains necessity. This interpenetration finds its expression in judgments that are a priori and yet synthetic, on the one hand, and synthetic and yet a priori, on the other. Kant thought that he could attain this goal only by way of a "changed point of view" (B xvi) referred to as a "Copernican revolution." On the supposition, thus far considered to be valid, that "all our knowledge must conform to objects" (ibid. ), a priori judgments that enlarge man's knowledge synthetically are impossible. Here one needs the opposite assumption, according to which "we suppose that objects must conform to our knowledge" (ibid. ); only in this way are we able "to have knowledge of objects a priori, determining something in regard to them prior to their being given" (ibid. ). Consequently, "we can know a priori of things only what we ourselves put into them" (B xviii); this means that the process of knowing a priori "has to do only with appearances, and must leave the thing-in-itself as indeed real per se, but as not known by us" (B xx). Since, however, all of metaphysics aims at the thing-in-itself, speculative reason, by which, as has been said, we "never transcend the limits of possible experience" (B xix), is unable to rise to the metaphysical level.

Critique of Knowledge. Kant perfects his criticism of knowledge in the Critique of Pure Reason, which moves from transcendental aesthetics to transcendental logic; and, within the latter, from transcendental analytics to transcendental dialectics. see transcendental (kantian). Throughout, the investigation revolves around the synthetic a priori judgments that have already been mentioned; these are synthetic insofar as they extend knowledge through a predicate that is not contained in the concept of the subject; they are a priori insofar as they have a necessary and universal validity, and this previous to any actual experience of individual cases. All of this, however, leads to the question: "How are a priori synthetic judgments possible?" (B 19). To put it more accurately, these judgments are questioned as to the conditions for their possibility; such conditions, on the terms of the Copernican revolution, can be found only in the subject. Kant here develops his transcendental method, a method by which he transcends a priori knowledge and arrives at the level of the conditions for its possibility, which are already marked out in the subject.

Mathematics and natural science, for him, have already followed the certain path of science. Thus, as he points out in detail, they contain a number of synthetic a priori judgments that are valid without further discussion. Consequently, one has to prove not that they are valid, but how their accepted validity is possible. To explain this, Kant goes back to the distinction between matter and form in human knowledge. The matter coincides with sensation; this is "the effect of an object upon the faculty of representation, so far as we are affected by it" (A 19); only in this way "can the object be given to us" (ibid. ). Matter, taken a posteriori as unordered multiplicity, has as its opposite complement form, "in which alone the sensations can be posited" and connected "in certain relationships" (A 20); this form must "lie ready for the sensations a priori in the mind" (ibid. ). At this point one must explain the three domains of a priori forms.

First is the region of sense knowledge. This is the field of "receptivity" by which "we are affected by the objects" (A 19); "objects are given to us by means of sensibility, and it alone yields us intuitions" (ibid. ). Now, that intuition is called empirical "which is in relation to the object through sensation" (A 20) and which therefore is based on received impressions. By way of contrast, a pure intuition is that in which "there is nothing that belongs to sensation" (ibid. ); it is "the pure form of sensibility" (ibid. ) and is actuated in the mind a priori, even without a given object. Correspondingly, transcendental aesthetics is "the science of all principles of a priori sensibility" (A 21); but these are two, "namely, space and time" (A 22), and they are the conditions for the possibility of the a priori synthetic judgments of mathematics. Space is more particularly the form of the external sense faculties, i.e., "the subjective condition of sensibility, under which alone outer intuition is possible for us" (A26). Time, on the other hand, is "the form of inner sense, that is, of the intuition of ourselves and of our inner state" (A 33). Again, time is "the formal a priori condition of all appearances whatsoever," because the external representations also "belong, in themselves, as determinations of the mind, to our inner state" (A 34). To space and time is ascribed an "empirical reality" (A 35), that is, an objective validity, as the conditions that alone enable man to perceive objects; in the same way they have a "transcendental ideality" (A 36) insofar as they are "merely conditions of our sensibility" and cannot, in any way, be ascribed to "things as they are in themselves" (ibid. ). Thus, it is true, they "make a priori synthetic propositions possible," but these "apply to objects only in so far as objects are viewed as appearances, and do not present things as they are in themselves" (A 39).

Second is the area of reason. As "spontaneity [in the production] of concepts," reason cooperates with the sense faculties, which are "receptivity for impressions"; through these impressions the object is "given," whereas through reason it is "thought" (A 50). Knowledge can arise "only through their union," for "thoughts without content are empty, and intuitions without concepts are blind" (A 51). Everything depends on the pure concepts; in these "there is no mingling of sensation," and they concern only "the form of the thought of an object in general" (A 5051). Thus transcendental analytics consists in the "dissection of the faculty of understanding itself" insofar as, in this faculty, the pure concepts as in "their birthplace," have been located and prepared in an a priori way (A 6566). It is thus that the synthetic a priori judgments of natural science are explained with regard to their possibility. Here the question is how to seek pure concepts on the basis of a single principle and how to "determine in an a priori manner their systematic completeness" (A 67). Because reason reaches only to "the mediate knowledge of an object" (A 68) or judgments, it constitutes "a faculty of judgment" (A 69). The elementary forms of judgment are outlined in it; from the point of view of "the mere form of understanding" they can be classified "under four heads, each of which contains three moments" (A 70). Coordinated to these are the 12 "pure concepts of understanding" (e.g., substance, causality, etc.) "which apply a priori to objects of intuition in general" (A 79); as "the true, primary concepts of the pure understanding" they are called "the categories" (A 81). To the process of educing them is linked transcendental deduction, which shows that the categories are "conditions of the possibility of experience and are therefore valid a priori for all objects of experience" (B 161). However, objects must be understood not as things in themselves, but as "appearances in space and time" that are determined by the categories (B 168169). "Consequently, there can be no a priori knowledge, except of objects of possible experience" (B 166). Subject to the same limitations are the principles that teach reason (being the potency for judging) how "to apply to appearances the concepts of understanding" (A 132). To these principles belong the "principle of succession in time in accordance with the law of causality: All alterations take place in conformity with the law of the connection of cause and effect" (A 189, B 232).

Third is the study of the intellect, which is the concern of transcendental dialectics. Here the synthetic a priori judgments of metaphysics are examined as to their possibility. The question is not how they are possible, but simply whether they are possible. Kant's answer is that they are not. Here his concern is to show the "transcendental illusion" (A 297); it is a "natural and inevitable illusion" (A 298), and thus it has been able to lead metaphysics astray until now. The critique must be applied to "transcendental principles" that, in contrast to "immanent" principles, lead man to go beyond "the limits of possible experience" (A 295). At the basis of these principles one finds "transcendental ideas," designed by reason in an a priori and necessary fashion; "no object adequate to the transcendental idea can ever be found within experience"; "for they view all knowledge gained in experience as being determined by an absolute totality of conditions," by "an absolute whole" (A 327), or even by "an unconditioned [reality]" (A 323), whereas "no experience is unconditioned" (A 326). From the different ways of drawing conclusions, Kant gathers that there are three and only three ideas, namely, the soul as "the absolute (unconditioned) unity of the thinking subject," the world as "the absolute unity of the series of conditions of appearance," and God as "the absolute unity of the condition of all objects of thought in general" (A 334). These ideas "never allow of any constitutive employment as supplying concepts of certain objects" (A644). In other words, the objects that are outlined in these ideas are never recognized through them; for ideas that go as far as the thing-in-itself remain empty, because the intellectual intuition that complements them and reaches out into the realm of the thing-in-itself has not been given to man. Or, one should say, man's "nature is so constituted that our intuition can never be other than sensible" (A51). On the other hand, these same ideas have an "indispensably necessary, regulative employment" insofar as they put before the intellect the "form of a whole of knowledge" and in this way "determine a priori for every part its position and relation to the other parts" (A 644645). This delimitation of their use is opposed by the "sophistications" that rise "from the very nature of reason" (A 339) and claim to form a bridge from ideas to their corresponding objects. The four paralogisms intend to proceed "from the transcendental concept of the subject" to a science "concerning the nature of our thinking being" (A 340, 345). Just as "rational psychology" (A342) is impossible, so also is "rational cosmology" (A408). When the latter is attempted as "the absolute totality of conditions for any given appearance" (A 340), reason is entangled in the four antinomies (e.g., the limitation vs. the boundlessness of the universe in space and time). In like fashion, there can be no rational theology (A 63l); for all three kinds of proof for the existence of God are inconclusive (A 590). "The physico-theological proof rests upon the cosmological proof, and the cosmological upon the ontological [proof]" (A 630), which itself suffers from an illegitimate transition from the realm of concepts to the realm of reality. What is left of God is only the "transcendental ideal" as the "concept of all reality" and "the complete determination of things," "without requiring that all this reality be objectively given and be itself a thing" (A 580).

Critique of Morality. Whereas the theoretical reason, or strict knowledge, can use ideas only in a regulative manner and concepts only within the realm of the phenomena (in contrast to the noumena), practical reason, or morality, goes on to the objective use of ideas and to extending the application of concepts to the noumena. Here Kant finds a basic fact, a given reality beyond any doubt: the categorical imperative as the "fundamental law of pure practical reason." It is: "So act that the maxim of your will could always hold at the same time as the principle of a universal legislation" (Critique of Practical Reason; ed. Cassirer, 5:35). This "synthetic proposition a priori" is not based on "any pure or empirical intuition"; but it presents itself as something that "forces itself upon us" (36). In it the "pure will" is conceived as "determined by the mere form of the law"(35); on the other hand, "the material of volition," being the "object of a desire," takes away morality (38). As opposed to this "heteronomy," one finds "autonomy" to be "the sole principle of all moral laws" (38), and in this principle pure reason is "originally legislative" (36). Moral acting is not only conditionally, viz, "to make a desired effect possible," but it is "unconditionally commanded" (36). Therefore, it is "not limited to human beings" but extends to all rational beings, even "the Infinite Being" (37); however, it presents itself only to man as an "obligation" whose fulfillment brings him closer to the holiness of the Divine Being.

By reason of the unconditional or absolute quality of the moral law, pure reason is authorized to make "an extension in its practical use which is not possible to it in its speculative use" (57). In this way Kant arrives at the postulates, which are not "theoretical dogmas but presuppositions of necessarily practical import." They do not expand "speculative knowledge, but they give objective reality to the ideas of speculative reason" (143); here the pure will shows itself as "belonging to a pure intelligible world" (57). "These postulates are those of immortality, of freedom affirmatively regarded (as the causality of a being so far as he belongs to the intelligible world), and of the existence of God" (143). They evoke assent not through insight, but through "pure practical faith." One says: I will those things that correspond to the postulates to be reality, "I stand by this and will not give up this belief" (155). At this point "my interest inevitably determines my judgment because I will not yield anything of this interest" (ibid. ). Thus the practical metaphysics of faith, for which room had been made by abolishing the theoretical metaphysics of pure knowledge, is shown by Kant to be the center of gravity in human thought.

Critique of Aesthetic Experience. This critique deals with the transition that constitutes the ultimate unity of reason. Here the faculty of judgment forms "a middle between understanding and reason" (Critique of Judgment; ed. Cassirer, 5:245). In like manner "the feeling of pleasure or displeasure" stands "between the faculties of knowledge and desire" (ibid. ). The reflective (as opposed to the determining) power of judgment rises from "the particular" to "the universal" (248). In this it is guided by the a priori principle of "finality," which, however, reflects only on the "nexus of phenomena in nature," and should not be ascribed to nature itself (249). Finality is also found in the fact that nature is in keeping with the "need of understanding" to discover repeatedly the comprehensive principles in the apparently "heterogeneous laws" and phenomena of nature (255256). The fulfillment of this need gives "a very appreciable pleasure"; even "the feeling of pleasure is determined by a ground which is a priori and valid for all men: and that, too, merely by virtue of the reference of the object to our faculty of cognition" without considering the practical finality attached to the faculty of desire (256).

More particularly, one must distinguish the aesthetic judgment from the teleological judgment (262). The first consists in "the faculty of estimating formal finality (otherwise called subjective) by the feeling of pleasure or displeasure"; the latter refers to "the faculty of estimating the real finality (objective) of nature by understanding and reason" (262). More precisely, "the aesthetic representation of finality" is present when the representation of an object is "immediately coupled with the feeling of pleasure" (258). But this pleasure is caused through the fact that "the conformity of the object to the cognitive faculties" is "brought into play in the reflective judgment" and establishes a harmonious interplay, particularly between the imagination and the intellect (258259). The object with whose representation "pleasure is also judged to be combined necessarily" is called beautiful; "the faculty of judging by means of such a pleasure (and so also with universal validity)" is taste (259). Accordingly, "the beautiful is that which, apart from a concept, pleases universally" (289) or "is cognized as object of a necessary delight" (311), and this "apart from any interest" (279) or "apart from the representation of an end" (306), which would appeal not to feeling but to desire.

Critique of Religion. According to Kant, religion consists in the "recognition of all duties as divine commands" (Critique of Practical Reason, 140); this, however, does not mean that they are "arbitrary and contingent ordinances of a foreign will" (ibid. ). He who fulfills the obligation out of consideration of God, out of "fear or hope," falls into a heteronomy that "would destroy the entire moral worth of the actions" (ibid. ). However, the moral law orders man to strive after "the highest possible good," and one must follow this law without self-interest and purely as an obligation (ibid. ). This highest good includes "the greatest degree of moral perfection" and the "greatest happiness" corresponding to it (141). But because only "a holy and beneficent Author of the world" is able to guarantee such a correspondence, it is possible for one to hope for the highest good only when his will is in accord with God's will (ibid. ). It is only in this sense that obligations, though they are "essential laws of any free will, must [still] be regarded as commands of the Supreme Being" (140). Religion is ultimately "the disposition, accompanying all our actions, to perform these as though they were being executed in the service of God" (Religion within the Limits of Pure Reason; ed. Cassirer, 6:346). All religious activity (e.g., prayer) reduces to this; everything that goes beyond it is characterized by Kant as "a superstitious illusion"(345). Only such a religion based on reason and restricted to the field of morals is permitted; only this constitutes the true core of the Christian religion of revelation, which degenerates into "practical superstition" and "clericalism" (325327) when it pretends to be more than it is.

Critical Appraisal. With the ability of a genius, Kant aspired to create a grand synthesis between sense knowledge and intellectual knowledge and between man's theoretical and practical activity. He developed his transcendental method in order to achieve this synthesis. In this undertaking he was able to attain noteworthy results: the unity of human cognition, its necessity and universality, the significance of the a priori, the absoluteness of the moral imperative, the foundation of existence in the metaphysical order, and the transcendental problematics. Yet Kant's synthesis, taken as a whole, failed. It did so because he remained too much subject to the limitations of his own historical situation and, therefore, was not able to go deep enough and penetrate to ultimate depths.

From the point of view of M. Heidegger, one may summarize Kant's failure in his being unaware of being. How much Kant succumbs to this is clearly shown by his distinction between reason and intellect. The reason is rightly considered the faculty that, by way of fundamental concepts or categories, permeates sensible phenomena; this is equivalent to the ratio of St. thomas aquinas and its corresponding quiddity, or quidditas rei materialis. Kant's intellect, on the other hand, reaches out into the metaphysical realm with its three ideas, but is never able really to penetrate it. The basis for this restriction lies in intellect's having lost, for Kant, its proper orientation toward being as all-inclusivean orientation that enables man to enter the metaphysical realm in the first place. For St. Thomas, on the contrary, intellectus is intrinsically ordered to ens, which is grounded in esse. In this connection, Kant considers intellect as completely excluded from any form of intellectual intuition, whereas for St. Thomas intellectus participates in such intuition through its grasp of being, but without having it as such. Consequently, in St. Thomas's view man enters into the realm of the absolute on the theoretical level; here he is in communication with all other intelligent beings, including the divine mind. Kant relegates all this to the practical realm alone.

The transcendental method can be carried through in a way that goes beyond Kant himself to arrive at being as the primary condition for the possibility of human knowledge, and even of all human action. This basic idea has far-reaching consequences. The proof for God's existence is somehow precontained in the orientation of intellect toward being; thus does theoretical metaphysics become possible. Being, too, enables a priori knowledge to reveal rather than conceal, as it must do for Kant. Again, the formal objects of the soul's faculties for St. Thomas correspond to Kant's forms; thus knowledge through categories is not restricted to that which is "for man," but opens up to that which is "in itself." Finally, the absoluteness of the moral imperative also receives its foundation in being, and thus theory and practice are brought into harmony and unity.

See Also: kantianism; neo-kantianism; criticism, philosophical; agnosticism; understanding (intellectus).

Bibliography: Works. Gesammelte Schriften, 22 v. (Berlin 190242), critical ed. sponsored by the Prussian Academy of Sciences. Immanuel Kants Werke, ed. e. cassirer, 11 v. (Berlin 191218). General studies. f. c. copleston, History of Philosophy (Westminster, Md. 19461963) v.6. j. d. collins, A History of Modern European Philosophy (Milwaukee 1954). s. vanni rovighi, Introduzione allo studio di K. (2d ed. Milan 1951). m. campo, La genesi del criticismo kantiano (Varese 1953). v. mathieu, La filosofia trascendentale e l'"Opus postumum" di K. (Turin 1958). h. j. de vleeschauwer, La Déduction transcendantale dans l'oeuvre de K, 3 v. (Antwerp 193437); L'Évolution de la pensée kantienne (Paris 1939). k. vorlÄnder, I. Kant: Der Mann und das Werk, 2 v. (Leipzig 1924). m. wundt, Kant als Metaphysiker (Stuttgart 1924). j. marÉchal, Le Point de départ de la métaphysique, v.3 (3d ed. Paris 1944) v.5 (2d ed. 1949). Catholic and fundamental. m. aebi, K.s Begründung der "Deutschen Philos" (Basel 1947). g. martin, I. Kant: Ontologie und Wissenschaftstheorie (Cologne 1951). Tulane University, A Symposion on K. (New Orleans 1954). j. b. lotz, ed., Kant und die Scholastik heute (Pullach 1955). h. heimsoeth, Studien zur Philosophie I. Kants (Cologne 1956). f. deleka, I. Kant: Hist.-krit. Interpretation der Hauptschriften (Heidelberg 1963). Theoretical philosophy. m. heidegger, K. und das Problem der Metaphysik (Bonn 1929); Die Frage nach dem Ding (Tübingen 1962). c. nink, Kommentar zu K.s Kritik der reinen Vernunft (Frankfurt 1930). h. j. paton, K.s Metaphysics of Experience (New York 1936). f. grayeff, Deutung und Darstellung der theoretischen Philosophie K.s (Hamburg 1951). h.w. cassirer, Kant's First Critique (New York 1954). r. p. wolff, Kant's Theory of Mental Activity (Cambridge, Mass. 1963). Practical philosophy. g. krÜger, Philosophie und Moral in der kantischen Kritik (Tübingen 1931). r. daval, La Métaphysique de Kant (Paris 1951). a. r. duncan, Practical Reason and Morality (London 1957). h. j. paton, The Categorical Imperative (3d ed. London 1959). j. schmucker, Die Ursprünge der Ethik Kants in seinen vorkritischen Schriften und Reflektionen (Meisenheim 1961) Catholic and fundamental. Aesthetics. w. biemel, Die Bedeutung von Kants Begründung der Ästhetik für die Philosophie der Kunst (Cologne 1959). Philosophy of religion. j. hasenfuss, Die Grundlagen der Religion bei Kant (Würzburg 1927), Catholic. b. jansen, Die Religionsphilosophie Kants (Berlin 1929), Catholic.

[j. b. lotz]

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KANT, IMMANUEL (17241804)

KANT, IMMANUEL (17241804), German philosopher. Immanuel Kant was born 24 April 1724 in Königsberg (now Kaliningrad) in East Prussia. He attended a Pietist school and the University of Königsberg and in 1755, after six years as a private tutor, obtained a position at his university. Promoted to professor there in 1770, he taught and served in administrative posts until 1798 and died 12 February 1804.


Kant's predecessors had treated knowledge as beginning from data about the world that the mind passively receives from the senses or through immediate insight into eternal truths or ideas. Kant, by contrast, made the activity of the mind central both to the world as we live in it and to our knowledge of it.

Kant built his systematic theoretical philosophy around the idea that the world as we experience it does not exist independently of us. Our own minds, he argued, are responsible for its form and structure. This idea constituted his "Copernican revolution." Before Copernicus, astronomical data were explained by assuming that the sun revolves around the earth. Reversing this, Copernicus explained the data by taking the earth to revolve around the sun. Kant explained experience by denying that our knowledge conforms to objects, instead holding that objects in experience conform to our knowledgeto the way our mind necessarily works.

In moral philosophy Kant proposed an equally revolutionary idea. In morality, he held, we are not required to obey laws imposed by God or eternal moral principles or Platonic forms; instead we must understand morality as resting on a law that springs from our own practical rationality. We are "autonomous" because we legislate the moral law we are to obey. The form of the moral world results from the mind's activity.

These views were designed to protect scientific knowledge from skeptical attacks such as that of David Hume (17111776) and also to show how morality and responsibility could be preserved in a Newtonian deterministic universe. Kant's theoretical philosophy laid the foundations for the whole enterprise.


In the Kritik der reinen Vernunft (1781; Critique of pure reason) Kant criticized his predecessors for not seeing that there is a deep difference between perceptual experiences and abstract concepts. The mind accepts the "percepts" that things outside it cause in it, but the mind itself imposes a framework of both time and space even on such given data. Concepts are rules by which the mind organizes percepts, and they show the mind's activity. The mind of any rational agent is equipped with several basic "categories," which are fundamental ways of organizing the data accepted through the senses. Nothing can be part of our experience, therefore, unless it is temporal and spatial and is organized by categories like those of continuing physical object and cause and effect. Percepts and concepts together yield the world as we live in it. The mind's structure explains how we can attain necessary truth in our knowledge of this world.

Kant allows that we can think of a thing as it is in itself (Ding an sich) outside experiencea noumenonbut insists that we can know only things as they are for usas phenomena. Because percepts as well as concepts are necessary for knowledge, we cannot know anything at all about what goes beyond possible experience. Hence we cannot have answers, either positive or negative, to what were then the main questions of religion and metaphysics: Does God exist? Are we immortal? Are we free?


In the Grundlegung zur Metaphysik der Sitten (1785; Groundwork of the metaphysics of morals) and the Kritik der praktischen Vernunft (1788; Critique of practical reason) Kant claimed that, in the practical realm, our desires are the counterpart to given sensory data in theoretical knowledge. But we are not causally determined to accept desires as giving us reasons to act. We are free because our will enables us to affirm or reject the claim of any desire to be a reason. Only what the will accepts is a reason to act. And the will, which Kant defines as practical reason, imposes its own forms prior to allowing a desire to count as a reason.

The forms the will imposes on desires include the master form, which is the moral law. As it applies to us, the moral law is an imperative or directive that cannot reasonably be flouted: it is the "categorical imperative." It tells us to act only on plans we could rationally allow everyone to act on. Hence morality, under the categorical imperative, would create a harmonious moral world out of desires that would naturally all too often lead us into conflict.


Because he denied that we could know anything that goes beyond experience, Kant seemed to his contemporaries to have eliminated all hope for a rational religion. But he said that he had destroyed knowledge to make room for faith. He tried to justify a religion safe from scientific criticism by arguing that the categorical imperative gives us practical or moral reason to believe in the essential religious tenets: God, freedom, and immortality. If few philosophers have been convinced by his moral arguments for God and immortality, many think that his account of freedom still has great appeal.


Kant aimed to limit naturalismthe view that a single system of causation explains all human activity as well as all other events. To do so, he made philosophy the master discipline that sets boundaries to the cognitive claims of all other thinking. Science is the judge of beliefs about experience, but it can say nothing about claims concerning morality or religion, or (as Kant also argued) about aesthetic taste. His remarkable theory that the mind helps construct the world in which we live opened the way for the radical idealisms of Friedrich Wilhelm Joseph von Schelling (17751854), Johann Gottlieb Fichte (17621814), and Georg Wilhelm Friedrich Hegel (17701831). Kant's assertion of "the primacy of practical reason"that practical reason can answer questions that theoretical reason cannotwas suggestive for the development of pragmatism. His moral philosophy has been and still is both widely used and hotly contested. Kant's work has had an influence on Western thought unsurpassed by that of any other modern philosopher.

See also Hume, David ; Moral Philosophy and Ethics ; Natural Law.


Primary Sources

The Cambridge Edition of the Works of Immanuel Kant, edited by Paul Guyer and Allen W. Wood, Cambridge, U.K., 1992. Contains the best translations of Kant's works, from the early "pre-critical" writings through the Opus Postumum, and including extensive selections from student lecture notes.

Kant, Immanuel. Gesammelte Schriften. Vols. 127. Berlin, 1969.

Secondary Sources

Guyer, Paul, ed. Cambridge Companion to Kant. Cambridge, U.K., 1992. Contains articles covering most aspects of Kant's philosophy and a good bibliography.

Kuehn, Manfred. Kant: A Biography. Cambridge, U.K., 2001. Excellent scholarly bibliography.

J. B. Schneewind

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Kant, Immanuel 1724-1804




Immanuel Kant was born in 1724 in Konigsberg, Prussia (now Kalingrad, Russia). He contributed to metaphysics, epistemology, ethics, and political philosophy. He lived most of his life in Konigsberg, where he died in 1804. He lived long enough to see the early stages of the French Revolution, which he initially welcomed because of its emphasis on both liberty and equality.

Kants philosophy emphasized the reconciliation of disparate themes and theories. In human nature he tried to reconcile the demands of heteronomy and autonomy. The latter has two distinct meanings: one ethical, the second metaphysical. In epistemology he tried to reconcile the competing claims of the rationalistswho emphasized a priori knowledge, primarily mathematicswith those of the empiricists, who claimed that all knowledge is based on experience. David Humes skeptical development of empiricist philosophy, Kant said, interrupted my dogmatic slumber (Kant [1783] 1953, p. 9). Humean skepticism threatened both traditional theism and the recently triumphant Newtonian science.


Kant wanted to defend religion from skeptical arguments and Newtonian science from a similar type of skepticism. He also defended a libertarian theory of human nature from the new determinism that many saw as implicit in Newtonian physics. This is the problem of heteronomy and autonomy. The former is the view that even human behavior is controlled by the same laws as the rest of the universe, implying that free will is an illusion. The latter is the view that not all human actions are dependent on (or deducible from) the laws of nature.

Kants theory of knowledge was based on a complex theory of categories of the mind that we have a priori (prior to, and independently of, experience) and that we apply to experience. Without it we could not have any coherent experience. It constitutes a third way of knowledge between a priori mathematical and logical concepts and those based on experience. It is synthetic a priori knowledge. Just as Copernicus reversed the roles of the sun and earth, so Kant reversed the role of thought and experience: We impose our mental categories on the world, not vice versa.

Kant argued that these concepts applied only to the world of experience and could not apply to metaphysical problems such as God, freedom, and immortality. He produced a complex critique of the three traditional theistic proofs (ontological, teleological, and cosmological) but also argued that reason could not disprove Gods existence, and then offered pragmatic proofs for such a belief. Kants Religion within the Limits of Reason Alone ([1787] 1960) was an attempt to replace religion based on revelation or fideism.


Kants moral philosophy was based on an ethical interpretation of autonomy culminating in his categorical imperative(s) and his proto-liberal political philosophy of freedom. The categorical imperative has two versions: I ought never to act except in such a way that I can also will that my maxim should become a universal law ([1797] 1964, p. 70) and the somewhat clearer, act in such a way that you always treat the person of any other, never simply as a means but always as an end ([1797] 1964, p. 96). The best interpretation of this is: Dont use people as if they were tools or machines; they are persons with independent wills and desires of their own. Because Kant assumed that people have conflicting wills and desires, he asserted that legislators must pass laws that protect everyone equally. Kantian equality is purely formal, meaning that laws must protect everyone equally, but he permitted massive material inequality, based on differences in everyones talent, industry, and good fortune (Two Essays on Right [1797] in Phelps 1973). Kant denied that there could be a principle of welfare or happiness, inferring from this that neither morality nor legislation could be based on experience

Kant distinguished between perfect and imperfect duties. The former are based on the putative rights of others; the latter are not. Therefore, although animals do not have rights, we should not be cruel to them. Charity to the poor is another imperfect duty.

Despite the cosmopolitan character of his categorical imperative and political philosophy, Kant seemed to absorb from Hume an uncritical racism, especially concerning Africans. There are two ways in which one might defend either Kant or Hume. One would be the historicist argument, that we cannot judge people from different times and places by our contemporary standards. The other is to downplay the significance of these views in either philosopher in their overall philosophy. The latter is the more promising route because the eighteenth century was allegedly the age of Reason and Enlightenment. It also was the age in which slavery was first attacked on a widespread basis, leading to its eventual abolition in most of the world. Jeremy Bentham (17481832) argued for decent treatment for blacks, for animals, and (albeit secretly) for homosexuals, on the grounds that the key issue was not Can they reason? but Can they suffer? In addition, racism seems to conflict logically with Kants cosmopolitanism.

Kants greatest influence on the twentieth century may have involved his proposals for perpetual peace via a League of Nations. He also had great faith in republican governments to promote such peace better than monarchies would. In 1784 he wrote What Is Enlightenment? The basic idea was a willingness to dare to think for ourselves. His idea of autonomy, however, should not be confused with a do your own thing mentality: Instead, it meant that the laws we impose on ourselves are based on logically impeccable arguments.

SEE ALSO Autonomy; Bentham, Jeremy; Enlightenment; Epistemology; Ethics; Hermeneutics; Hume, David; League of Nations; Philosophy; Racism; Religion; Slavery


Kant, Immanuel. [1781] 1902. Critique of Pure Reason. New York: Collier.

Kant, Immanuel. [1783] 1953. Prolegomena to Any Future Metaphysics. Manchester, U.K.: Manchester University Press.

Kant, Immanuel. [1785; 1784] 1959. Groundwork of the Metaphysics of Morals, and an Answer to the Question: What Is Enlightenment? Indianapolis, IN: Bobbs-Merrill

Kant, Immanuel. [1787] 1960. Religion within the Limits of Reason Alone. Trans. with intro. and notes Theodore M. Greene and Hoyt H. Hudson. New York: Harper and Row.

Kant, Immanuel. [1788] 1956. Critique of Practical Reason. Indianapolis, IN: Bobbs-Merrill.

Kant, Immanuel. [1790] 1964. Critique of Judgement. New York: Hafner.

Kant, Immanuel. [1797] 1964. Groundwork of the Metaphysics of Morals. New York: Harper and Row.

Kant, Immanuel. 1963. On History, ed. with intro Lewis White Beck; trans. Lewis White Beck, Robert E. Anchor, and Emil L. Fackenheim. Indianapolis, IN: Bobbs-Merrill.

Phelps, Edmund, ed. 1973. Economic Justice: Selected Readings. Middlesex, U.K.: Penguin.

Calvin Hayes

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Immanuel Kant (1724–1804) was born in Köningsberg, East Prussia (now Kaliningrad, Russia), on April 22 and died there on February 12, having lived such an uneventful life that one early commentator questioned whether he had one. Yet his critical philosophy constituted a watershed in Western intellectual history. For science, technology, and ethics the significance of the Kantian watershed lies in the analysis of human experience as constructive and the argument that reason has insight only into that which it produces according to its own plan. With this argument Kant developed a new critical interpretation of scientific knowledge and of ethical reason that presents both as exhibiting constructive, not to say technological, dimensions.

Prior to Kant, modern philosophy was characterized by a contest between rationalism and empiricism. Rationalists such as René Descartes (1596–1650) and Gottfried Wilhelm Leibniz (1646–1716) considered reason to be the origin of all true knowledge, sensation merely a degraded form of thought or source of illusion. By contrast, empiricists such as Francis Bacon (1561–1626) and John Locke (1632–1704) argued that all knowledge derived from the senses, with thought being no more than an extension of sense perception. Kant's precritical writings included works in natural philosophy, aesthetics, and ethics reflective of the rationalist tradition. But reading the British empiricist David Hume (1711–1776) awakened Kant from what he described as his "dogmatic slumbers." This awakening led, in turn, to a synthesis of these two approaches in his major work, The Critique of Pure Reason, which argued that the form of human experience is constructed a priori by reason while its material content arises a posteriori from sensation. This is the core of Kant's transcendental or critical idealism, which he subsequently extended into ethics and aesthetics in order to respond to what he considered the three main questions of philosophy: What can I know? What ought I to do? What can I hope for? He later added a fourth question that synthesized the first three: What is the human being?

The Critique of Pure Reason (1781)

Kant's major work undertakes what he terms a "Copernican revolution" in philosophy. Whereas traditionally philosophy had begun with particular objects of experience, Kant's transcendental method begins with experience in general and tries to uncover the "transcendental preconditions" that make such experience possible. For Kant, objects are seen as fitting into human representational structures rather than representational structures simply arising from objects. As Hume had shown, the necessity that these representational structures possess, the fact that all objects must appear in space and time, simply cannot be derived from sensory experience. According to Kant, then, space and time are the a priori forms of sensibility, the ideal or transcendental forms that make it possible for human beings to experience any object.

Only as a manifold of content within space and time is sense intuition or experience possible. But objects that first appear to the senses within the necessary structures of space and time are further known using concepts such as substance and causality. For Kant, the expectation that events necessarily have causes is not so much derived from experience as brought to experience, although of course the particular causes are determined by experience. Experience would not be what it is, would not be intelligible or knowable, without these a prior pure concepts of the understanding. The justification of these categories rests with their constitutive role in human experience and the fact that they work to make experience possible.

What is it that is known when sensation and understanding cooperate in this way to make experience scientifically intelligible? The answer is phenomena. Perhaps the single most important distinction in Kant's thought is that between phenomena and noumena, things as they appear to people and things in themselves, respectively. The former are open to positive knowledge, whereas the latter can be thought but never known in a positive or scientific sense.

The human mind nevertheless has a tendency to try to extend itself beyond phenomena to things-in-themselves. This includes claiming to have positive knowledge of supersensible realities such as God, the soul, and freedom, the topics of traditional metaphysics. These ideals of pure reason can never be scientifically verified. Thus Kant argued that traditional metaphysics, which focuses on objects that transcend experience rather than the transcendental preconditions of experience, is not an authentic form of knowledge. Yet, although the ideals of pure reason cannot be experienced they can be thought, and in their thinking serve what Kant calls a regulative function.

Critique of Practical Reason (1788)

The second critique turns from science to ethics and deals with practical or moral reasoning. This book was preceded by an introductory Foundations of the Metaphysics of Morals (1785), which developed a deontological theory of ethics, that is, one based on the primacy of duty. For Kant, the only unconditional good is a good will, one that wills to do what is a duty merely because it is a duty, or to choose duty for its own sake. The philosophical challenge for ethics is to explicate what this means, and to identify the transcendental preconditions of its possibility.

Kant thus approaches ethics not in terms of the consequences of actions or whether decisions make a person happy, but in terms of moral obligation. The idea of duty leads Kant to the idea of freedom as its basis. Although with regard to many actions the will may be influenced by factors outside itself, that is, be heteronomous, at least in some instances the will is able to decide for itself, that is, act autonomously. In exercising its own decision-making capacity, the will may also reason according to hypothetical imperatives (If one wants X then do Y) or categorical imperatives (Do Y, no matter what). Practical reason at the highest level displays a spontaneity that makes its own law for itself, simply because this is the right way to act, independent of any particular consequences.

Hypothetical reasoning may be described as the basis of technological thinking. Indeed, Kant calls one form of a hypothetical imperative a technical imperative, which focuses on discovering the means to achieve some end. Categorical reasoning, by contrast, focuses on the identification of worthy ends. According to Kant the most worthy end, and thus categorical imperative, is to act according to a maxim that is universal, that is, applies to all, or to treat all persons as ends in themselves. Human beings have an inherent worth or dignity, unlike objects that have exchange value. To recognize this and act accordingly is to begin to construct something more than a traditional society or state, which presumes people acting out of self-interest and treats others as means to their own ends, and to begin to construct instead a new kind of social order that Kant calls a "kingdom of ends." This moral ideal has been applied widely to a range of ethical issues related to science and technology, from the treatment of human subjects in medical research, to privacy in the use of computers and debates about the permissibility of human reproductive cloning.

The second critique postulates freedom, the existence of God, and immortality of the soul as necessary presuppositions of moral experience. Freedom is necessary to make sense of the human experience of moral responsibility, God to guarantee the ultimate triumph of moral order, and immortality to allow for the final realization of the good will. In this regard, practical reason provides access to a supersensible reality closed to science, though in a manner that can only be an issue of rational faith.

The Third Critique and Kant's Influence

Kant's Critique of Judgment (1790) attempted to show how theoretical and practical reason—science and ethics—are unified in the sense of beauty. For Kant, the judgments of beauty and purpose provide a sensible symbol of the supersensible realm. They suggest that the natural and ethical realms make up a unified whole. The purposeful structures humans observe especially in organic bodies and their beauty provide clues to the further understanding of nature. The idea that nature is purposeful lies behind the human belief that a system of laws of nature is possible. It can also lead to the extension of humanity's empirical investigations of nature. Judgments of beauty are based on a subjective feeling of delight in an object, but this feeling has a universal validity deriving from the harmony of the faculties of imagination and understanding. The feeling of the sublime depends upon the moral feeling Kant supposed common to all of humanity.

Taken together, Kant's three critiques thus answer what he takes to be the basic questions of philosophy. The fourth question was to find its answer in a study of anthropology. What can be known are intelligent constructions of science that constitute the basic form of knowledge. What ought to be done is to treat human beings as ends in themselves in order to establish a kingdom of ends. For the individual human being there is hope for personal immortality in order to be able to make infinite moral progress. For the human race there is the hope that human progress will be instantiated in the moralization of the human race, so that the advance of human capacities, including humankind's scientific understanding of the world, may contribute to the construction of a harmonious moral social order.

Kant's influence is inestimable. Although in the next generation Georg Wilhelm Friedrich Hegel (1770–1831) challenged Kant's distinction between phenomena and noumena, Hegel's alternative system never became as influential as Kant's. Future efforts to explicate the unique power and limitations of science and the independent validity of ethics have repeatedly returned to formulations of what have become known as various forms of neo-Kantianism. Ernst Cassirer (1874–1945), for instance, widened Kant's appreciation of human construction in science to include the entire range of cultural symbolic production, including the realms of language, myth, and religion. Bernard Gert's Morality: Its Nature and Justification (2004) develops a Kantian-like set of moral rules, often explicitly considering issues related especially to biomedical technologies.

More generally, Friedrich Dessauer (1881–1963) developed a broadly Kantian interpretation of technology, going so far as to propose a fourth Kantian critique of the transcendental preconditions of technological invention (Mitcham 1994). More recently, Ernesto Mayz Vallenilla (1989) has provided an analysis of the transformations of technical rationality brought about by new instrumentations that reflects a Kantian and phenomenological heritage. Finally, detached from its transcendental moorings, Kant's approach may also be seen as supporting contemporary social constructivist interpretations of science and technology (Bijker, Hughes, and Pinch 1987).

In his first critique, Kant sought to limit positive scientific knowledge to phenomenal reality so that noumena may be posited without interference by rational faith and that ethics may be able to rest on its own foundations. In this way, ethics could be freed from the dogmatic assumptions and skepticism associated with traditional metaphysics.

[E]ven the assumption—as made on behalf of the necessary practical employment of my reason—of God, freedom, and immortality is not permissible unless at the same time speculative reason be deprived of its pretensions to transcendent insight … thus rendering all practical extension of pure reason impossible. I have therefore found it necessary to deny knowledge, in order to make room for faith. The dogmatism of metaphysics, that is, the preconception that it is possible to make headway in metaphysics without a previous criticism of pure reason, is the source of all that unbelief, always very dogmatic, which wars against morality. (Kant 1965 [1781], pp. Bxxix–Bxxx)

Kant's philosophy sought the harmonious development of human faculties but ended in separating scientific intellection and ethical reflection. Both exhibit the free and spontaneous constructive activity of the human mind. Yet Kant did not foresee how scientific (and technical) development could outpace the application of ethical reflection. As a result, ethical thought often appears to lag behind technoscientific achievements. To what extent should ethical concerns establish limits on scientific inquiry? This question manifests itself repeatedly in contemporary discussions of advancing science, new technologies, and ethics.


SEE ALSO Axiology; Deontology; Discourse Ethics; Freedom; Leibniz, G. W.; Risk and Emotion; Scientific Ethics.


Bijker, Wiebe E.; Thomas P. Hughes; and Trevor J. Pinch, eds. (1987). The Social Construction of Technological Systems: New Directions in the Sociology and History of Technology. Cambridge, MA: MIT Press. A collection of essays exploring the social construction of technology.

Cassirer, Ernst. (1953, 1955, 1957, and 1996). Philosophy of Symbolic Forms, trans. Ralph Manheim and John Michael Krois. 4 vols. New Haven, CT: Yale University Press.

Gert, Bernard. (2004). Morality: Its Nature and Justification, rev. edition. Oxford and New York: Oxford University Press. The second extensive revision of Gert's The Moral Rules: A New Rational Foundation for Morality (1970).

Kant, Immanuel. (1902–1997). Gesammelte Schriften [Collected works], ed. the Royal Prussian Academy of Sciences (and its successors). 29 vols. Berlin: Georg Reimer (subsequently Walter de Gruyter). The standard German edition of Kant's works.

Kant, Immanuel. (1965 [1781/1787]). Critique of Pure Reason, trans. Norman Kemp Smith, unabridged edition. New York: St. Martin's Press.

Kant, Immanuel. (1990 [1785]). Foundations of the Metaphysics of Morals, trans. Lewis White Beck, 2nd edition. New York: Macmillan.

Kant, Immanuel. (1993 [1788]). Critique of Practical Reason, trans. Lewis White Beck, 3rd edition. New York: Macmillan.

Kant, Immanuel. (2000 [1790]). Critique of the Power of Judgment, edited by Paul Guyer, translated by Paul Guyer and Eric Matthews. Cambridge, UK: Cambridge University Press.

Körner, Stephan. (1955). Kant. Harmondsworth, UK: Penguin. A basic introduction to Kant's philosophy.

Mayz Vallenilla, Ernesto. (1989). Fundamentos de la meta-técnica Caracas, Venezuela: Monte Avila Editores. English translation: The Foundations of Meta-Technics, tr. Carl Mitcham. Laham, MD: University Press of America, 2004. A phenomenological analysis of the transition from the technical to the meta-technical forms of space and time.

Mitcham, Carl. (1994). Thinking through Technology: The Path between Engineering and Philosophy. Chicago: University of Chicago Press. A critical introduction to the philosophy of technology.

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Immanuel Kant

The major works of the German philosopher Immanuel Kant (1724-1804) offer an analysis of speculative and moral reason and the faculty of human judgment. He exerted an immense influence on the intellectual movements of the 19th and 20th centuries.

The fourth of nine children of Johann Georg and Anna Regina Kant, Immanuel Kant was born in the town of Königsberg on April 22, 1724. Johann Kant was a harness maker, and the large family lived in modest circumstances. The family belonged to a Protestant sect of Pietists, and a concern for religion touched every aspect of their lives. Although Kant became critical of formal religion, he continued to admire the "praiseworthy conduct" of Pietists. Kant's elementary education was taken at Saint George's Hospital School and then at the Collegium Fredericianum, a Pietist school, where he remained from 1732 until 1740.

In 1740 Kant entered the University of Königsberg. Under the influence of a young instructor, Martin Knutzen, Kant became interested in philosophy, mathematics, and the natural sciences. Through the use of Knutzen's private library, Kant grew familiar with the philosophy of Christian Wolff, who had systematized the rationalism of Leibniz. Kant accepted the rationalism of Leibniz and Wolff and the natural philosophy of Newton until a chance reading of David Hume aroused him from his "dogmatic slumbers."

The death of Kant's father in 1746 left him without income. He became a private tutor for 7 years in order to acquire the means and leisure to begin an academic career. During this period Kant published several papers dealing with scientific questions. The most important was the "General Natural History and Theory of the Heavens" in 1755. In this work Kant postulated the origin of the solar system as a result of the gravitational interaction of atoms. This theory anticipated Laplace's hypothesis (1796) by more than 40 years. In the same year Kant presented a Latin treatise, "On Fire", to qualify for the doctoral degree.

Kant spent the next 15 years (1755-1770) as a nonsalaried lecturer whose fees were derived entirely from the students who attended his lectures. In order to live he lectured between 26 and 28 hours a week on metaphysics, logic, mathematics, physics, and physical geography. Despite this enormous teaching burden, Kant continued to publish papers on various topics. He finally achieved a professorship at Königsberg in 1770.

Critique of Pure Reason

For the next decade Kant published almost nothing. But at the age of 57 he published the first edition of the Critique of Pure Reason (1781; 2d ed. 1787). This enormous work, one of the most important and difficult books in Western thought, attempts to resolve the contradictions inherent in perception and conception as explained by the rationalists and empiricists.

On the level of experience, Kant saw the inherent difficulties in the "representative theory of perception." Our percepts, or intuitions of things, are not themselves objects but rather images or re-presentations. Since these perceptual images are the only evidence for an external, physical world, it can be asked how faithfully mental images represent physical objects. On the level of conception, mathematical, scientific, and metaphysical judgments make predictions about the connections and consequences of events. As these judgments tell us about the past, present, and future, they cannot be derived from our immediate experience. Some events, however, can be experienced as conforming to these universal and necessary laws; hence, these judgments are more than mere definitions. The aim of the critique is to explain how experience and reason interact in perception and understanding.

Philosophers had long recognized two kinds of judgment. The first is analytic, which is the product of the analysis or definition of concepts. All analytic propositions are reducible to statements of identity, that is, they define what a thing is. For example, a triangle is a three-sided figure universally (always) and necessarily (could not be otherwise) by definition. As such, all analytic judgments are true a priori, or independent of experience. The content and form of the second type of judgment is exactly the reverse. Synthetic propositions expand or amplify our knowledge, but these judgments are a posteriori, or derived from experience.

Kant's position is that of the first thinker to posit the problem of pure reason correctly by isolating a third order of judgment. Consider the following propositions: 10 times 2 is 20; every event has a cause; the universe is created. As universal and necessary, all three judgments are a priori but also, according to Kant, synthetic, in that they extend our knowledge of reality. Thus the fundamental propositions of mathematics, science, and metaphysics are synthetic a priori, and the question that the Critique of Pure Reason poses is not an analysis of whether there is such knowledge but a methodology of how "understanding and reason can know apart from experience."

The solution to this problem is Kant's "Copernican Revolution." Until Copernicus hypothesized that the sun was the center of the universe and the earth in its rotation, science had assumed the earth was the center of the universe. Just so, argues Kant, philosophers have attempted and failed to prove that our perceptions and judgments are true because they correspond to objects. "We must therefore make trial whether we may not have more success…ifwe suppose that objects must conform to our knowledge." This radical proposal means that the mind constitutes the way the world appears and the way in which the world is thought about.

But, unlike later idealists, Kant does not say that the mind creates objects but only the conditions under which objects are perceived and understood. According to Kant, "we can know a priori of things only what we ourselves put into them." The attempt to preserve a realist orientation leads Kant to distinguish between the appearances of things (phenomena), as conditioned by the subjective forms of intuition, and the categories of the understanding and things-in-themselves (noumena). In brief, mathematics and science are true because they are derived from the ways in which the mind conditions its percepts and concepts, and metaphysics is an illusion because it claims to tell us about things as they really are. But since the mind constitutes the appearances and their intelligibility, we can never know noumenal reality (as it exists apart from mind) with any certainty. Although Kant considers the denial of metaphysics inconsequential because it has consisted only of "mock combats" in which no victory was ever gained, he is at some pains to establish that the restriction of pure reason to the limits of sensibility does not preclude a practical knowledge of morality and religion. In fact, the limitation of pure reason makes such faith more positive.

The first critique attempts to reconcile the conflict between rationalism and empiricism over the role of experience. Kant's ingenuity is to suggest that both parties are correct but one-sided, that is, "though all knowledge begins with experience it does not follow that it arises out of experience." Kant attempts to isolate the a priori element in the various parts of knowledge: intuition, which Kant calls esthetic, understanding, or analytic and speculative reason, or dialectic. He calls his method "transcendental" as opposed to formal or material logic, and by this he means only the manner, or mode, in which we perceive, understand, or think.

The problem of the transcendental esthetic can be seen in the term "a priori intuition." That is, what does the mind tell us about experience prior to having experience. Kant argues that if one eliminates the content of any possible intuition, space and time remain as the a priori forms, or ways, in which the mind can perceive. As a priori forms of any possible experience, space and time are subjective conditions or limitations of human sensibility. But as the universal and necessary conditions without which there will be no experience, these forms are empirical conditions of appearances, or phenomena. Thus, for Kant, space and time are "transcendentally ideal" and "empirically real" as subjective conditions and objective, constitutive principles of intuition. In brief, this is Kant's resolution of the scientific debate between the adherents of Newton's concept of absolute space and time and Leibniz's relational view. Kant is saying that space and time are absolute conditions for human experience even though there may be nonspatial and nontemporal entities that are unknown.

This argument provides an answer to how synthetic a priori judgments in mathematics are possible. These judgments are universal and necessary, and yet they apply to and yield new knowledge about experience. The principle of Kant's explanation may be expressed as follows: whatever is true of a condition is a priori true of the conditioned. Space and time are the conditions for all possible perceptions. And Euclidean geometry and arithmetic are true of space and time. Therefore, arithmetic and geometry are a priori valid for all possible appearances.

A weak analogy with eyeglasses will explain the drift of Kant's thinking. If I cannot see anything without the glasses, they are my subjective limitation since there may be things which are not perceivable. But the glasses are also objective conditions for the possibility of anything appearing to me. And whatevers true of this condition—such as their being tinted—will be true a priori of whatever can be seen but not necessarily of whatever can be. The point of Kant's radical proposal is that human experience may be just that— exclusively human—but that it is valid of appearances since space and time are the a priori and empirical conditions of every possible perception.

A similar explanation of the working of human understanding presented a great difficulty occasioned by the seeming impossibility of specifying the forms of thinking in other than an arbitrary and chance manner. Eventually Kant discovered a "transcendental clue" in the traditional forms of logical judgment enumerated by Aristotle. The question raised is why are there only 12 forms of judgment? Kant argued that each form of possible judgment was related to a thought form that he called an a priori category of the understanding. Thus, again, there is a form and content division such that, if one thinks, there are only certain ways in which one can make judgments about the quantity, quality, relation, and modality of objects. In human understanding, as the name implies, experience is made to stand underneath and be organized by the categories. Experience is given as conditioned by space and time, a category is superimposed by the mind, and the resulting synthesis produces human knowing. This complicated process of synthesis is unified by the ego and aided by the imagination, which associates particular percepts with appropriate universal concepts. As in the case of perception, Kant's efforts are directed toward reconciling the claims of both rationalism and empiricism. Concepts of themselves are empty logical forms, and percepts, alone, are blind; it is only in their synthesis that understanding, or knowing, takes place.

This development commits Kant to the position that science is knowing and metaphysics is false, speculative thinking. Knowing is confirmed by experience as above, but the categories can be extended beyond space and time, and they, then, function as ideas of pure reason. Since metaphysics claims to speak about things as they are rather than as they appear, such pure thinking must justify itself without appeal to experience. But that is just the difficulty when one asks questions about the unconditioned reality of the self, world, or God!

It is not that reason is incapable of producing arguments, but rather that there are equally valid arguments that contradict one another, and experience is unable to resolve these "antinomies," or seeming contradictions. For example, we know that the universe is either created or eternal, and we can think both of these alternatives through; but the spatiotemporal world of experience would be the same in either instance; and so while the mind can think about these problems, it can never know the answers to the questions that it raises. The only exception to this rule occurs in what Kant calls the "dynamical antinomies" concerning the dilemmas of necessity or freedom and atheism or theism. Here Kant suggests that in the realms of morality and religion one can entertain the possibility that while necessity and determinism are true of phenomena, freedom and God are true of noumena. Thus, one could live in a universe that is physically determined and still believe in human freedom.

Later Works

In 1783 Kant restated the main outlines of his first critique in a brief, analytic form in the Prolegomena to Any Future Metaphysics. In 1785 he presented an early view of the practical aspects of reason in Fundamental Principles of the Metaphysic of Morals. In 1788 he published the Critique of Practical Reason.

While theoretical reason is concerned with cognition, practical reason is concerned with will, or self-determination. There is only one human reason, but after it decides what it can know, it must determine how it shall act. In the analytic of practical reason Kant attempts to isolate the a priori element in morality. The notion that happiness is the end of life is purely subjective, and every empirical morality is arbitrary.

Thus the freedom of the will, which is only a speculative possibility for pure reason, becomes the practical necessity of determining how one shall lead his life. And the fundamental, rational principle of a free morality is some universal and necessary law to which a man commits himself. This principle is called by Kant the "Categorical Imperative," which states that a man should obligate himself to act so that any one of his actions could be made into a universal law binding all mankind. The dignity of man consists in the freedom to overcome inclination and private interest in order to obligate oneself to the duty of performing the good for its own sake. In examining the consequences of man's freedom, Kant insists that practical reason postulates the immortality of the soul and the existence of God as the conditions for true freedom.

In 1790 Kant completed his third critique, which attempts to draw these conflicting tensions together. In pure reason the mind produces constitutive principles of phenomena, and in practical reason the mind produces regulative principles of noumenal reality. The Critique of Judgment attempts to connect the concepts of nature with the concepts of freedom. The reflective or teleological judgment of finality, which is derived from our esthetic feelings about the fittingness of things, mediates between our cognition and our will. This judgment neither constitutes nature like the understanding nor legislates action like practical reason, but it does enable us to think of the "purposiveness" of nature as a realm of ends that are in harmony with universal laws.

Although Kant continued writing until shortly before his death, the "critical works" are the source of his influence. Only a life of extraordinary self-discipline enabled him to accomplish his task. He was barely 5 feet tall and extremely thin, and his health was never robust. He attributed his longevity to an invariable routine. Rising at five, he drank tea and smoked his daily pipe and meditated for an hour. From six to seven he prepared his lectures and taught from seven to nine in his own home. He worked in his study until one. He invited friends for long dinners, which lasted often until four. After his one daily meal he walked between four and five so punctually that people were said to set their watches on his passing. He continued to write or read until he retired at ten. Toward the end of his life he became increasingly antisocial and bitter over the growing loss of his memory and capacity for work. Kant became totally blind and finally died on Feb. 12, 1804.

Further Reading

There is no standard edition in English, but virtually all of Kant's major works are available in various paperback editions. The field of general and critical studies is rich. Basic accounts of Kant's critique are Herbert James Paton, Kant's Metaphysic of Experience (2 vols., 1936); Heinrick Cassirer, A Commentary on Kant's Critique of Judgment (1938); A. C. Ewing, A Commentary on Kant's Critique of Pure Reason (1938); Lewis White Beck, A Commentary on Kant's Critique of Practical Reason (1960); Norman Kemp Smith, A Commentary to Kant's Critique of Pure Reason (2d ed. 1962); and S. Körner, Kant (1964), which is one of the best general works available. Specialized studies include Paul Arthur Schlipp, Kant's Pre-critical Ethics (2d ed. 1960); Martin Heidegger, Kant and the Problem of Metaphysics, translated by James S. Churchill (1962); Robert Paul Wolff, Kant's Theory of Mental Activity (1963); and P. F. Strawson, The Bounds of Sense (1966). □

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Kant, Immanuel

Immanuel Kant, it is said, never traveled more than fifty miles from his native city of Königsberg in East Prussia. Nevertheless, there are few thinkers who have had as wide an influence as Kant in the history of Western thought. His importance for discussions about science and religion stems from his reasoned defense of the position that religion and science should be kept clearly separated from one another.

Life and writings

Born in 1724, Kant was the son of humble pietistic parents who wished for him to have an education. At sixteen he entered the University of Königsberg, where he studied Christian Wolff's interpretation of Gottfried Wilhelm von Leibniz's (16461716) philosophy. Kant's encounter with Isaac Newton's (16421727) work during his student years encouraged in him an independent attitude toward Leibniz's thought, with the additional result that he developed a profound interest in the natural sciences. When his father died during his university training, Kant left the university and served as a tutor in private families near Königsberg between 1748 and 1754. After returning to the university he completed a thesis in June of 1755 and, on finishing a second thesis in September, was granted permission to lecture. Prior to the age of thirty-six, Kant's writings dealt primarily, although not exclusively, with the natural sciences. His most famous work from this period, the Universal Natural History and Theory of the Heavens, was published in 1755 and contained Kant's ideas on the how a cosmos subject to Newton's laws of motion might have formed.

After Kant received a professorship in logic and metaphysics at Königsberg in 1770 it took some time before his writings reflected the turn his appointment marked from a precritical stance to what he himself labeled critical philosophy. Once Kant began publishing, the works came thick and fast. The first edition of his most famous book, the Critique of Pure Reason, did not appear until 1781. When it did so it was largely misunderstood, moving Kant to restate its main arguments two years later in his Prolegomena to Every Future Metaphysics. He also expanded the Critique in a second edition in 1787, and in the following year he published the first of two new critiques, the Critique of Practical Reason. This second critique picked up on a concern with moral philosophy Kant had initially addressed in another work from the 1780s. The Critique of Judgment, which appeared in 1790, dealt with reasoning about the realms of the aesthetic and the purposeful. Earlier in 1786 Kant returned to his reflections on science and its methods in a work entitled The Metaphysical Foundations of Natural Science. Finally, his Religion Within the Boundaries of Pure Reason, which appeared in 1793, provoked King Frederick William II to forbid him from publishing anything more on religion, a mandate he honored until the king's death in 1797. Kant died February 12, 1804.

Impact on science and religion discussion

Kant's impact on the subject of natural science and religion is best understood in his relation to the Scottish thinker David Hume (17111776), whom Kant claimed awakened him from his dogmatic slumber. Exactly when this was to have occurred is unclear; however, among other things Hume represented for Kant the possibility that the use of reason in fact undermined the essential truths of religion, morality, and common sense. Kant faced squarely Hume's skepticism about causality and other conclusions of common sense that haunted the thinkers of the late eighteenth century. The fear was that if Hume's reasoning was correct about these matters, then how was one to retain one's belief in God? As Kant's contemporary Friedrich Jacobi (17431819) put it, "Nothing frightens man so much, nothing darkens his mind to such a degree as when God disappears from nature when purpose, wisdom, and goodness no longer seem to reign in nature, but only a blind necessity of dumb chance."

In Dialogues Concerning Natural Religion (1779) Hume exposed the inadequacy where the relationship of God to nature was concerned of both classical metaphysical rationalism, in which one reasoned from principles accepted apart from or before experience (a priori), and empiricism, where reasoning was undertaken only after one experienced the world (a posteriori). In the Critique of Pure Reason, Kant attempted to forge a new path between both rationalism and empiricism by introducing what he called in the preface to the second edition a "Copernican" viewpoint in philosophy. The astronomer Nicolaus Copernicus (14831543) had shown that the way to think about the relationship of the earth and the sun was to reverse their traditional roles. Kant demanded that to understand the relationship of the world of experience and the mind one must also reverse the way in which roles were traditionally assigned. It is not that the mind is shaped by experience of the world (empiricism); rather, the world of experience is shaped by "categories" associated with the mind's operation. But in shaping our experience of the world the categories themselves prescribe only the structure for objects of possible experience (not the content of actual experience, as in metaphysical rationalism). Human minds dictate in advance, for example, that experience can only be apprehended in accordance with causal relationships between events, but they cannot determine prior to a person's experiencing the world which specific causal relationships actually obtain. Without content supplied by sense experience, the mind, even equipped as it is by its categories, would still be blind. But without the ordering impact of the categories, experience would be chaos. This is why Kant said at the beginning of the introduction to the Critique that "although all our knowledge begins with experience, it does not follow that it all arises out of experience."

This middle way contained important implications for the understanding of scientific knowledge. If the mind contributes in a formative way to the manner in which people experience the world, then they can no longer claim that the world they experience is necessarily the world that exists apart from the mind. Regularities in one's experience of the world, even those so repetitious as to earn the label of scientific laws, cannot be known as regularities in nature that one discovers; rather, they bear the touch of one's mind. People are, as Kant says in his Prolegomena to Every Future Metaphysics, "lawgivers of reason." Scientific knowledge, then, refers to the world of experience, the world of phenomena apprehended with the senses, not to a reality lying behind human experience. Gone is the possibility of conceiving truth as the correspondence of one's ideas to the way things are, a common conception of many scientists. One cannot be sure of the way things are, so there is no possibility of checking that against one's ideas.

If Kant's critique of reason introduced a radical limitation of what could be known, he was adamant that there was a realm that lay beyond cognition. "I have therefore found it necessary to deny knowledge in order to make room for faith, " he wrote in the preface to the second edition of the Critique. The object of faith, however, could not by definition be articulated or expressed in terms of knowledge. Religion for Kant did not and could not have to do with cognitive propositions about nature. In his 1793 book, Religion within the Boundaries of Reason Alone, he made clear that he accepted Hume's negative conclusions about the so-called argument from design, according to which one reasoned from evidence of design in the world to the existence of a designer. Religion did not commence with nor have to do with one's knowledge of the world. Religion had to do with the purity of one's heart. To be religious is to view one's duties as if they are divine commands. It should be noted that Kant's religious stance was purely intellectual. In spite of the fact that his philosophy made room for the possibility of eternal life, it was clear to those close to him that he scoffed at prayer and other religious practices and that he had no faith in a personal God.

Kant's position, then, radically separated science from religion, as if the two subjects contained no common ground. It took some time for this position to gain a hearing since in the Romantic period, which dominated in the first decades of the nineteenth century, there was great dissatisfaction with Kant's severe restriction of reason's scope to the realm of phenomena. Even one of the earliest neo-Kantian thinkers from this era, Jakob Fries (17731843), added Ahndung (aesthetic sense) to knowledge and faith as a third possible way in which people may relate to that which exists outside of them. Fries believed that through aesthetic sense people could intimate the infinite that was present in the finite.

It was not until the neo-Kantian revival of the late nineteenth century that Kant's radical separation of science from religion emerged in earnest. In the works of the Marburg theologian Wilhelm Herrmann (18461922), composed during the heyday of debates about biological evolution, one recognizes the attempt to cede to natural science the freedom to investigate natural phenomena without restriction while at the same time stressing religion's right to address questions of value and right. If religion must surrender nature to natural science, natural science, in turn, must along with religion renounce any claim to have arrived at metaphysical reality. Religion becomes morality while science becomes Naturbeherrschung, mastery of the world.

In the twentieth century the separation of natural science and religion continued to mark much of German theology, especially the works of well-known existential theologians who wrote in the decades following World War I. Most recently something of a Kantian position on the relationship between science and religion has been advocated by the noted American paleontologist Stephen Jay Gould (19412000) who, without ever naming Kant, introduced the notion of non-overlapping magisteria (NOMA) as a means of dealing with the realities of science, which is concerned with the factual construction of nature, and religion, which concerns itself with moral issues about the value and meaning of life. Gould acknowledge more than classical neo-Kantians, however, that while magisteria do not overlap, they are everywhere interlaced in a complex manner that often makes it extremely challenging to keep the two separate. Critics of the Kantian position maintain that in practice it is impossible to retain a rigid separation of science and religion.

See also Metaphysics; Morality; Natural Theology


beiser, frederick. the fate of reason: german philosophy from kant to fichte. cambridge, mass.: harvard university press 1987.

fries, jakob. knowledge, belief, and aesthetic sense (1805), trans. kent richter, ed. frederick gregory. cologne, germany: dinter verlag, 1989.

gould, stephen jay. rocks of ages: science and religion in the fullness of life. new york: ballantine, 1999.

gregory, frederick. nature lost? natural science and the german theological traditions of the nineteenth century. cambridge, mass.: harvard university press, 1992.

kant, immanuel. cambridge edition of the works of immanuel kant, eds. paul guyer et al. cambridge, uk: cambridge university press, 1992-2001.

kuehn, manfred. kant: a biography. cambridge, uk: cambridge university press, 2001.

frederick gregory

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Kant, Immanuel



Immanuel Kant (1724–1804) was born in Königsberg (then in East Prussia) and spent his entire life there. He studied at the University of Königsberg and taught there from 1755 until a few years before his death.

Kant’s philosophy lies between empiricism and rationalism. He took from Hume the idea that man is “nothing but a bundle or collection of perceptions which succeed each other with inconceivable rapidity” (Hume 1739–1779, p. 320 in 1826 edition), and from Spinoza the concept that ideas are independent of experience. Yet he could accept neither a pure rationalism nor a pure empiricism; his primary work, theCritique of Pure Reason, begins as follows: “There can be no doubt that all our knowledge begins with experience . . . but it does not follow that it all arises out of experience” ([1781] 1950, p. 41). In this and another major work, Prolegomena to Any Future Metaphysics (1783), he was concerned to find the “valid source” of human knowledge, the way of establishing truth.

Kant’s particular concern was to determine whether what he called synthetic a priori judgments are possible, that is to say, whether it is possible to establish necessary and universal connections among objects. Convinced that mathematics provides such synthetic a priori propositions, he sought to prove that it is possible in like manner to obtain knowledge of the laws of nature.

Newton’s construction of scientific and mathematical theories suggested to Kant the process by which such knowledge might be acquired: “Accidental observations, made in obedience to no previously thought-out plan, can never be made to yield a necessary law, which alone reason is concerned to discover. Reason . . . must approach nature in order to be taught by it. It must not, however, do so in the character of a pupil who listens to every-thing that the teacher chooses to say, but of an appointed judge who compels the witnesses to answer questions which he himself has formulated” ([1781] 1950, p. 20 in Preface to 1787 edition).

Man, according to Kant, approaches experience in terms of basicAnschauungen (kinds of intuition) that are themselves not derived from experience and are not subject to empirical proof; these intuitions are space, time, and causation. Together with four categories (quantity, quality, relation, and modality), these intuitions are the basis of all understanding. Knowledge is merely an application of these categories, or a priori concepts, to sense perceptions, which are intuitively structured in time and space. Human knowledge is limited to these spatial and temporal phenomena; it does not extend to what is behind phenomena, that is, to the noumena, or things-in-themselves.

Influence on psychology. Much controversy in psychology developed as a result of Kant’s distinction between the self as a thing-in-itself, or noumenon, and the self as a phenomenon. Since the first self is the transcendental unity of self-consciousness or apperception, it is inaccessible to inquiry except by introspection; its sole expression is moral judgment. According to Kant, only the phenomenal self can be the subject of empirical studies, and so it becomes part of anthropology (“Anthropologie in pragmatischer Hinsicht” 1798). This empirical or pragmatic psychology deals with what an observer can know about mental processes. Kant’s dichotomy between what an individual may know of his own mind (noumenon) and what others may know of him (phenomenon) gave rise to the controversy between the introspectionist and the behaviorist approaches to psychology.

For the introspectionists, awareness of oneself, Bewusstsein or consciousness, became the core concept and introspection the chief method. Their subject of study was inner experience, and introspection provided the only means of access to the data. The behaviorists rejected this method, relying exclusively on observation of the overt behavior of the phenomenal self.

While Kant’s “anthropology” (i.e., psychology) does not contain many new ideas, his critique of the concept of soul was a significant departure both from the Judaeo-Christian tradition and from Pla-tonic philosophy. “The concept,” he wrote, “is there-fore quite void as regards all hoped-for insight into the cause of appearances and cannot at all serve as a principle of explanation of that which inner or outer experience supplies” ([1783] 1951, p. 79).

Social theory Kant’s social theory was based on the concept of progress, the source of progress being the inner conflict between man’s sociability and his selfishness. Kant called this antagonism the “unsocial sociability.” Man, according to Kant, “has an inclination to socialize himself by associating with others” but he is also driven by anti-social forces. Kant’s conception of the positive dynamic consequences of man’s conflict are well expressed in this passage: “Man wishes concord; but Nature knows better what is good for his species, and she will have discord… The natural impulses that urge man in this direction, the sources of that unsociableness and general antagonism from which so many evils arise, do yet at the same time impel him to new exertion of his powers, and consequently, to further development of his natural capacities” ([1784–1795 1891, pp. 11–12).

The social order that Kant recommended, based as it was on this analysis of man’s nature, would permit a maximum of individual freedom and com-petition, yet would have enough power to restrain this freedom whenever it threatened to produce oppression or anarchy. He proposed a similar system for international affairs; each separate state should be free to run its own affairs, but a supra-national federation of sovereign states would have enough power to regulate international relations and prevent war.

Kant believed not only in political progress—the history of the human race could be viewed as a development toward a perfect political constitution —but also in moral progress. The stages in man’s moral development are anomy, heteronomy, and autonomy. In the natural, primitive, anomic state, impulses were naive, innocent, and uncontrolled. Civilization began when man broke with the natural state and accepted externally imposed moral law; this is the stage of heteronomy. Ultimately, there will be moral autonomy, a state of absolute freedom, in which the individual will obey only a self-imposed law, the “moral imperative.”

Benjamin B. Wolman

[For the historical context of Kant’s work, see the biographies ofHumeand Spinoza. For discussion of the subsequent development of Kant’s ideas, seeGestalt Theory; Phenomenology; Psychology, article onEXISTENTIAL PSYCHOLOGY; and the biographies OfDurkheim; Hegel; Hering; Koffka; KÖhler; kÜlpe; Lotze; MÜller. Georg Elias; Stumpf; Weber, Max; Wertheimer; Wundt.]


(1781) 1950 Immanuel Kant’s Critique of Pure Reason. Translated by N. Kemp Smith. New York: Humanities. → First published in German.

(1783) 1951 Prolegomena to Any Future Metaphysics. New York: Liberal Arts. → First published in German.

(1784–1795) 1891 Kant’sPrinciples of Politics, Including His Essay “On Perpetual Peace.” Edited and translated by W. Hastie. Edinburgh: Clark.→ First published in German.

(1798) 1907 Anthropologie in pragmatischer Hinsicht. Volume 7, pages 117–333 in Kant’s gesammelte Schriften. Berlin: Reimer.

Kant’s gesammelte Schriften. 22 vols. Berlin: Reimer, 1900–1942.


Brett, George S. (1912–1921) 1962 Brett’s History of Psychology. Edited and abridged by R. S. Peters. London: Allen & Unwin; New York: Macmillan.

Cassirer, Ernst 1918 Kants Leben und Lehre. Berlin: Cassirer.

Hume, David (1739–1779) 1964 The Philosophical Works. 4 vols. Edited by Thomas Hill Green and Thomas Hodge Grose. Aalen (Germany): Scientia.

Paton, Herbert J. (1936) 1951 Kant’s Metaphysic of Experience: A Commentary on the First Half of the Kritik der reinen Vernunft. 2 vols. London: Allen & Unwin.

Spinoza, Benedict (1677) 1950 Ethics. Translated by A. Boyle. London: Dent; New York: Dutton.

Weldon, Thomas Dewar (1945) 1958 Kant’s Critique of Pure Reason. 2d ed. Oxford: Clarendon. → First published asIntroduction to Kant’s Critique of Pure Reason.

Wolman, Benjamin B. (editor) Historical Roots of Contemporary Psychology. New York: Harper. → Contains an essay by Wolman on “Immanuel Kant and His Impact on Psychology.” Scheduled for publication in 1968.