"Logical positivism" is the name given in 1931 by A. E. Blumberg and Herbert Feigl to a set of philosophical ideas put forward by the Vienna circle. Synonymous expressions include "consistent empiricism," "logical empiricism," "scientific empiricism," and "logical neopositivism." The name logical positivism is often, but misleadingly, used more broadly to include the "analytical" or "ordinary language" philosophies developed at Cambridge and Oxford.
The logical positivists thought of themselves as continuing a nineteenth-century Viennese empirical tradition, closely linked with British empiricism and culminating in the antimetaphysical, scientifically oriented teachings of Ernst Mach. In 1907 the mathematician Hans Hahn, the economist Otto Neurath, and the physicist Philipp Frank, all of whom were later to be prominent members of the Vienna circle, came together as an informal group to discuss the philosophy of science. They hoped to give an account of science that would do justice—as, they thought, Mach did not—to the central importance of mathematics, logic, and theoretical physics, without abandoning Mach's general doctrine that science is, fundamentally, the description of experience. As a solution to their problems, they looked to the "new positivism" of Jules Henri Poincaré; in attempting to reconcile Mach and Poincaré they anticipated the main themes of logical positivism.
In 1922, at the instigation of members of the "Vienna group," Moritz Schlick was invited to Vienna as professor, like Mach before him (1895–1901), in the philosophy of the inductive sciences. Schlick had been trained as a scientist under Max Planck and had won a name for himself as an interpreter of Albert Einstein's theory of relativity. But he was deeply interested in the classical problems of philosophy, as Mach had not been.
Around Schlick, whose personal and intellectual gifts particularly fitted him to be the leader of a cooperative discussion group, the "Vienna circle" quickly established itself. Its membership included Neurath, Friedrich Waismann, Edgar Zilsel, Béla von Juhos, Felix Kaufmann, Feigl, Victor Kraft, Philipp Frank—although he was by now teaching in Prague—Karl Menger, Kurt Gödel, and Hahn. In 1926 Rudolf Carnap was invited to Vienna as instructor in philosophy, and he quickly became a central figure in the circle's discussions; he wrote more freely than the other members of the circle and came to be regarded as the leading exponent of their ideas. Carnap had been trained as a physicist and mathematician at Jena, where he had come under Gottlob Frege's influence. Like other members of the circle, however, he derived his principal philosophical ideas from Mach and Bertrand Russell.
Ludwig Wittgenstein and Karl Popper were not members of the circle but had regular discussions with its members. In particular, Wittgenstein was in close contact with Schlick and Waismann. Wittgenstein's Tractatus Logico-Philosophicus had a profound influence on the deliberations of the circle, where it was interpreted as a development of British empiricism.
The circle ascribed to Wittgenstein the "verifiability principle"—that the meaning of a proposition is identical with the method of verifying it—that is, that a proposition means the set of experiences that are together equivalent to the proposition's being true. Wittgenstein, they also thought, had shown how an empiricist could give a satisfactory account of mathematics and logic. He had recognized that the propositions of logic and mathematics are tautologies. (The logical positivists paid no attention to Wittgenstein's distinction between tautologies and identities.) They are "independent of experience" only because they are empty of content, not because, as classical rationalists had argued, they are truths of a higher order than truths based on experience.
In the German-speaking countries, the Vienna circle was a small minority group. For the most part, German-speaking philosophers were still committed to some variety of "German idealism." Neurath, with his strong sociopolitical interests, was particularly insistent that the circle should act in the manner of a political party, setting out to destroy traditional metaphysics, which he saw as an instrument of social and political reaction.
In 1928 the significantly named Verein Ernst Mach (Ernst Mach Society) was set up by members of the circle with the avowed object of "propagating and furthering a scientific outlook" and "creating the intellectual instruments of modern empiricism." To welcome Schlick back to Vienna in 1929 from a visiting professorship at Stanford, California, Carnap, Hahn, and Neurath prepared a manifesto under the general title Wissenschaftliche Weltauffassung, Der Wiener Kreis (The Scientific World View: The Vienna Circle). This manifesto traced the teachings of the Vienna circle back to such positivists as David Hume and Mach, such scientific methodologists as Hermann Ludwig von Helmholtz, Poincaré, Pierre Maurice Marie Duhem, and Einstein, to logicians from Gottfried Wilhelm Leibniz to Russell, utilitarian moralists from Epicurus to John Stuart Mill, and to such sociologists as Ludwig Feuerbach, Karl Marx, Herbert Spencer, and Menger. Significantly absent were any representatives of the "German tradition"—even, although somewhat unfairly, Immanuel Kant.
In order to make its conclusions familiar to a wider world, the circle organized a series of congresses. The first of these was held in Prague in 1929 as a section of a mathematical and physical, not a philosophical, congress. It was jointly sponsored by the Ernst Mach Society and the Society for Empirical Philosophy, a Berlin group led by Hans Reichenbach and with such members as Walter Dubislav, Kurt Grelling and Carl Hempel, which stood close in its general approach to the Vienna circle.
Meanwhile, the international affiliations of the circle were increasing in importance. American philosophers like C. W. Morris emphasized the link between logical positivism and American pragmatism; Ernest Nagel and W. V. Quine visited Vienna and Prague. In Great Britain, logical positivism attracted the interest of such Cambridge-trained philosophers as L. Susan Stebbing and John Wisdom and the Oxford philosophers Gilbert Ryle and A. J. Ayer, the latter participating for a time in the deliberations of the circle. In France such philosophers of science as Louis Rougier were attracted by logical positivism, as were a group of neo-Thomists led by General Vouillemin, who welcomed the positivist critique of idealism. In Scandinavia, where the way had been prepared by the antimetaphysical philosophy of Axel Hägerström, a number of philosophers sympathized with the aims of the logical positivists; Eino Kaila, Arne Naess, Åke Petzäll, and Jørgen Jørgensen were prominent representatives of the international movement centering on logical positivism. The Polish logicians, especially Alfred Tarski, exerted a considerable influence on members of the circle, particularly on Carnap. German philosophers, except for Heinrich Scholz of Münster and the Berlin group, remained aloof. Undoubtedly, the organizational energies of the circle did much to bring into being in the 1930s an international community of empiricists; this was largely a consequence of the circle's isolation within the German countries themselves.
Meanwhile the circle was publishing. In 1930 it took over the journal Annalen der Philosophie and renamed it Erkenntnis. In the period from 1930 to 1940 it served as a "house organ" for members of the Vienna circle and their associates. In addition, the circle prepared a series of monographs under the general title Veröffentlichungen des Vereines Ernst Mach (from 1928 to 1934) and Einheitswissenschaft (edited by Neurath from 1934 until 1938).
During the 1930s, however, the Vienna circle disintegrated as a group. In 1931 Carnap left Vienna for Prague; in that year Feigl went to Iowa and later to Minnesota; Hahn died in 1934; in 1936 Carnap went to Chicago and Schlick was shot by a mentally deranged student. The meetings of the circle were discontinued. The Ernst Mach Society was formally dissolved in 1938; the publications of the circle could no longer be sold in German-speaking countries. Waismann and Neurath left for England; Zilsel and Kaufmann followed Feigl, Carnap, Menger, and Gödel to the United States. Erkenntnis moved in 1938 to The Hague, where it took the name Journal of Unified Science ; it was discontinued in 1940. Logical positivism, too, disintegrated as a movement, absorbed into international logical empiricism.
Critique of Traditional Philosophy
Mach denied that he was a philosopher. He was trying, he said, to unify science and, in the process, to rid it of all metaphysical elements; he was not constructing a philosophy. The general attitude of the Vienna circle was very similar. Schlick was the exception. With logical positivism, he argued, philosophy had taken a new turn, but logical positivism was nonetheless a philosophy. Carnap, in contrast, wrote that "we give no answer to philosophical questions and instead reject all philosophical questions, whether of Metaphysics, Ethics or Epistemology" (The Unity of Science, p. 21). Philosophy, on his view, had to be destroyed, not renovated.
Undoubtedly, this intransigent attitude to philosophy can in part be explained by the peculiar character of German idealism and its hostility to science. The logical positivists thought of themselves as extending the range of science over the whole area of systematic truth and as needing for that purpose to destroy the claim of idealist philosophers to have a special kind of suprascientific access to truth.
Of the traditional branches of philosophy, the positivists rejected transcendental metaphysics on the ground that its assertions were meaningless, since there was no possible way of verifying them in experience. Nothing that we could possibly experience, they argued, would serve to verify such assertions as "The Absolute is beyond time." Therefore, the positivists held, it tells us nothing. The rejection of transcendental metaphysics was not a novelty; Hume had described transcendental metaphysics as "sophistry and illusion" and had alleged that it makes use of insignificant expressions; Kant and the neo-Kantians had rejected its claim to be a form of theoretical knowledge; Mach had sought to remove all metaphysical elements from science. But whereas earlier critics of metaphysics had generally been content to describe it as empty or useless or unscientific, the logical positivists took over from Wittgenstein's Tractatus the rejection of metaphysics as meaningless. The propositions of metaphysics, they argued, are neither true nor false; they are wholly devoid of significance. It is as nonsensical to deny as to assert that the Absolute is beyond time.
Neo-Kantians had sometimes suggested that philosophy could be reduced to epistemology or "theory of knowledge," which discussed such topics as "the reality of the external world." But assertions about the external world, the positivists argued, are quite as meaningless as assertions about the Absolute or about things-in-themselves. For there is no possible way of verifying the assertion that there is, or the assertion that there is not, an external world independent of our experience. Realism and idealism, considered as epistemological theses, are equally meaningless. So far as epistemology has any content, it reduces to psychology, to assertions about the workings of the human mind, and these have nothing to do with philosophy.
The logical positivists disagreed about ethics. Of course they all rejected any variety of transcendental ethics, any attempt to set up a "realm of values" over and above the world of experience. Assertions about values, thus conceived, fall within the general province of transcendental metaphysics and had therefore to be rejected as nonsensical. But whereas Schlick sought to free ethics from its metaphysical elements by converting it into a naturalistic theory along quasi-utilitarian lines, Carnap and Ayer argued that what are ordinarily taken to be ethical assertions are not assertions at all. To say that "stealing is wrong," for example, is neither, they suggested, to make an empirical statement about stealing nor to relate stealing to some transcendental realm. "Stealing is wrong" either expresses our feelings about stealing, our feelings of disapproval, or, alternatively (positivists' opinions differ about this), it is an attempt to dissuade others from stealing. In either case, "stealing is wrong" conveys no information.
In general, the positivists explained, when they said of philosophical assertions that they were meaningless, they meant only that they lacked "cognitive meaning." Ethical and metaphysical assertions have emotional associations; this distinguishes them from mere jumbles of words. Such statements as "God exists" or "Stealing is wrong" are, on the face of it, very different from a collocation of nonsense syllables. But the fact remains, the positivists argued, that such "assertions" do not convey, as they purport to do, information about the existence or character of a particular kind of entity. Only science can give us that sort of information.
Not all philosophers, however, have devoted their attention to describing pseudo entities such as "the Absolute" or "values" or "the external world." Many of them have been mainly concerned with empirical-looking concepts such as "fact," "thing," "property," and "relation." Russell's lectures on logical atomism and Wittgenstein's Tractatus are cases in point.
Wittgenstein suggested, however, that the sections in the Tractatus in which he talked about facts, or attempted to show how propositions can picture facts, must all in the end be rejected as senseless—as attempts to say what can only be shown. For it is impossible in principle to pass beyond our language in order to discuss what our language talks about. Philosophy is the activity of clarifying; it is not a theory.
Schlick carried to its extreme Wittgenstein's Tractatus doctrine that philosophy is an activity. Philosophy, he suggested, consists in the deed of showing in what the meaning of a statement consists; that is, philosophy is a silent act of pointing. The ultimate meaning of a proposition cannot consist in other propositions. To clarify, therefore, we are forced in the end to pass beyond propositions to the experience in which their meaning consists.
This view won few adherents. It was generally agreed that philosophers could not avoid making the sort of ontological assertions Wittgenstein made in the Tractatus and that it is altogether too paradoxical to suggest that all propositions about, for example, the relation between facts and language are nonsensical, even if "important" nonsense. Neurath, in particular, insisted that nonsense cannot be "important," cannot act as a ladder by which we arrive at understanding, as Wittgenstein had said.
statements about language
Carnap suggested that Wittgenstein was mistaken in supposing that his ontological assertions were without any sense. They were, however, meaningful assertions about language, not about a world beyond language. No doubt, Carnap admits, ontological statements have the appearance of being about the world or, at least, about the relation between language and the world. But this is so only because they have been wrongly formulated in what Carnap calls "the material mode."
Carnap distinguishes three classes of sentences: object sentences, pseudo object sentences, and syntactical sentences. Any ordinary sentence of mathematics or science is an object sentence. Thus, for example, "Five is a prime number" and "Lions are fierce" are both object sentences. Syntactical sentences are sentences about words and the rules governing the use of words. For example, "Five is not a thing-word but a number-word" and "Lion is a thing-word" are syntactical sentences. Pseudo object sentences are peculiar to philosophy; they look like object sentences but if rightly understood turn out to be syntactical sentences. To understand them rightly we have to convert them from the "material mode" into the "formal mode," that is, from sentences that look as if they are about objects into sentences that are obviously about words. Examples are "Five is not a thing but a number" and "Lions are things." Once these sentences are converted out of the "material mode" into the corresponding "formal" (or syntactical) mode, they can be discussed; in the material mode they are quite undiscussable.
But how are syntactical disputes to be settled? Suppose one philosopher asserts and another denies that "numerical expressions are class-expressions of the second level"—Carnap's "translation" of "numbers are classes of classes"—how is it to be determined which is correct? All such statements, Carnap argues, are relative to a language; they are either statements about the characteristics of some existing language or proposals for the formation of a new language. Fully expressed, that is, they have the form "In language L, such-and-such an expression is of such-and-such a type." It can be immediately determined whether such a syntactical statement is true by examining the language in question.
Problems of Positivism
The course taken by the subsequent history of logical positivism was determined by its attempts to solve a set of problems set for it, for the most part, by its reliance on the verifiability principle. The status of that principle was by no means clear, for "The meaning of a proposition is the method of its verification" is not a scientific proposition. Should it therefore be rejected as meaningless? Faced with this difficulty, the logical positivists argued that it ought to be read not as a statement but as a proposal, a recommendation that propositions should not be accepted as meaningful unless they are verifiable. But this was an uneasy conclusion. For the positivists had set out to destroy metaphysics; now it appeared that the metaphysician could escape their criticisms simply by refusing to accept their recommendations.
Recognition of this difficulty led Carnap to suggest that the verifiability principle is an "explication," a contribution to the "rational reconstruction" of such concepts as metaphysics, science, and meaning, to be justified on the quasi-pragmatic grounds that if we ascribe meaning only to the verifiable we shall be able to distinguish forms of activity that are otherwise likely to be confused with one another. It is not, however, by any means clear in what way the verifiability principle can be invoked against a metaphysician who takes as his point of departure that his propositions clearly have a meaning. The most that can be said is that the onus is then on the metaphysician to distinguish his propositions from others that he would certainly have to admit to be meaningless.
A second set of problems hinged on the nature of the entities to which the verifiability principle applies. Since "proposition" had ordinarily been defined as "that which can be either true or false," it seemed odd to suggest that a proposition might be meaningless. Yet it was no less odd to suggest that a sentence—a set of words—could be verified, even if there was no doubt that it could be meaningless. Ayer suggested as an alternative the word statement, and he wrote as if the problem were a purely terminological one. But it is a serious question whether "true," "false," and "meaningless" are alternative descriptions of the same kind of occurrence or whether to describe a sentence as "meaningless" is not tantamount to denying that any statement has been made, any proposition put forward. This would have the consequence that we can consider whether a statement is verifiable only after we have settled the question of the meaning of the sentence used to make the statement.
The logical positivists themselves were much more concerned about the fact that the verifiability principle threatened to destroy not only metaphysics but also science. Whereas Mach had been happy to purge the sciences, the logical positivists ordinarily took for granted the substantial truth of contemporary science. Thus, it was a matter of vital concern to them when it became apparent that the verifiability principle would rule out as meaningless all scientific laws.
For such laws are, by the nature of the case, not conclusively verifiable; there is no set of experiences such that having these experiences is equivalent to the truth of a scientific law. Following Frank Plumpton Ramsey, Schlick suggested that laws should be regarded not as statements but as rules permitting us to pass from one singular statement to another singular statement. In Ryle's phrase, they are "inference-licenses." Neurath and Carnap objected to this on the ground that scientific laws are used in science as statements, not as rules. For example, attempts are made to falsify them, and it is absurd to speak of "falsifying a rule." Furthermore, Carnap pointed out, ordinary singular statements are in exactly the same position as laws of nature; there is no set of experiences such that if I have these experiences there must be, for example, a table in the room.
For these and comparable reasons "verifiability" was gradually replaced by "confirmability" or by the rather stronger notion of "testability." Whereas at first the meaning of a proposition had been identified with the experiences that we would have to have in order to know that the proposition is true, now this was reduced to the much weaker thesis that a proposition has a meaning only if it is possible to confirm it, that is, to derive true propositions from it. Carnap, in accordance with his "principle of tolerance," was prepared to admit that a language might be constructed in which only verifiable propositions would count as meaningful. He was content to point out that such a language would be less useful for science than a language that admits general laws. But most positivists, interested as they were in the actual structure of science, simply replaced the verifiability principle by a confirmability principle.
If, however, the original principle proved to be too strong, the new principle threatened to be too weak. For, on the face of it, the new principle admitted as meaningful such metaphysical propositions as "Either it is raining or the Absolute is not perfect." Whether the confirmability principle can so be restated as to act as a method of distinguishing between metaphysical statements as meaningless and scientific statements as meaningful remains a question of controversy.
unification of science
A further set of problems hinges on the question of what sort of things act as "verifiers" or "confirmers." One of Mach's main concerns, which the logical positivists shared, had been to unify science, especially by rejecting the view that psychology is about an "inner world" that is different from the "outer world" that physical science investigates. The doctrine that both physics and psychology describe "experiences" made such a unification possible. In his earlier writings Carnap tried to show in detail how "the world" could be constructed out of experience, linked together by relations of similarity. But then a new difficulty arose; one about how it is possible to show that one person's experiences are identical with another's. On the face of it, an experience-based science is fundamentally subjective; science is verified only at the cost of losing its objectivity.
To overcome this difficulty, Schlick drew a distinction between "content" and "structure." We can never be sure, he argued, that the content of our experience is identical with the content of any other person's experience, for example, that what he sees when he says that he sees something red is identical with what we see when we say we see something red. For scientific purposes, however, this does not matter in the slightest. Science is interested only in the structure of our experience, so that provided, for example, we all agree about the position of red on a color chart, it is of no importance whether our experience of red differs.
Yet Schlick still thought that such "experiences" are what gives content, meaning, to science, converting it from a conceptual frame into real knowledge. Thus, it appears that the ultimate content of science lies beyond all public observation. There is no way of verifying that another person is even experiencing a content, let alone a content that is like or unlike the content of my experience.
Profoundly dissatisfied with the conclusion that the ultimate content of scientific truths is private, Neurath was led to reject the view—which logical positivists had so far taken for granted—that it is "experiences" which verify propositions. Only a proposition, he argued, can verify a proposition. Carnap accepted this conclusion and developed the conception of a "protocol statement," the ultimate resting point of verifications, a statement of such a nature that to understand its meaning and to see that it is true are the same thing. Carnap still suggested, however, that a protocol statement records a private experience, even though every such statement—indeed every statement—can be translated into the public language of physics. Statements of the form "Here now an experience of red" can, he argued, be translated into statements about the physical state of the body of the person who has the experience of red. (Subsequently this "physicalist" thesis was expressed in the weaker form, that every statement is linked by means of correspondence rules with the statements of physics.)
Neurath was still dissatisfied. Protocol statements, he argued, must form part of science as distinct from merely being translatable into its language. Otherwise, science still rests on essentially private experience. In fact, protocol statements must take some such form as "Otto Neurath reports that at 3:15 p.m. there was a table in the room perceived by Otto." The effect of this suggestion, as Schlick remarked with horror, is to leave open the possibility that the basic protocol statements may not be true. They, rather than some natural law with which they are incompatible, can be rejected as false. Schlick persisted in arguing that the ultimate confirmations of scientific propositions must be experiences of the form "here, now, blue"—which he described as "the only synthetic statements which are not hypotheses." Carnap came to agree with Neurath, however, that all synthetic statements are hypotheses.
At first, indeed, Carnap replied to Neurath by invoking his principle of tolerance. One has a free choice, he argued, between a language that incorporates protocol statements and a language into which they can be translated. Subsequently he has moved more and more in Neurath's direction. Statements of the form "the body Carnap is in a state of green-seeing," he now suggests, are sufficient to act as confirmations, and it is not necessary at any point to use the "phenomenal language" that Mach had thought to be the basic language of science. But Carnap still writes as if the issue between physicalist and nonphysicalist hinges on the choice of a language. Logical positivism, we might say, split into three groups, one asserting physicalism, the second rejecting it, and the third expressing a preference for the physicalist language.
In his Logical Syntax of Language Carnap had argued that all statements about the "meaning" or "significance" of statements are of the "pseudo object" type and should be translated into a syntactical form. Thus, for example, "This letter is about the son of Mr. Miller" has to be read as asserting that in this letter a sentence occurs which has the expression "the son of Mr. Miller" as its subject. This was a highly implausible doctrine, since, clearly, a letter can be about the son of Mr. Miller without using the phrase "the son of Mr. Miller." Under Tarski's influence Carnap decided that his original thesis had been unduly restrictive; philosophy had to refer to the semantical as well as the syntactical characteristics of language in order to give a satisfactory explication of, for example, the conception of "truth." Now Carnap found himself in opposition to Neurath. To try to pass beyond language to what language signifies, Neurath argued, is at once to reintroduce the transcendental entities of metaphysics. The subsequent development of semantics at Carnap's hands would have done nothing to relieve Neurath's qualms. Languages can be constructed, Carnap argues, in a variety of ways, and the question whether, for example, one accepts a language that includes names for abstract entities is a matter of practical convenience, not admitting of argument at any other level. The influence of Mach on Carnap's thinking has now been almost entirely dissipated; he writes, rather, in the spirit of a Poincaré or a Duhem.
The Influence of Positivism
Logical positivism, considered as the doctrine of a sect, has disintegrated. In various ways it has been absorbed into the international movement of contemporary empiricism, within which the disputes that divided it are still being fought out. Originally, it set up a series of sharp contrasts: between metaphysics and science, logical and factual truths, the verifiable and the nonverifiable, the corrigible and the incorrigible, what can be shown and what can be said, facts and theories. In recent philosophy, all these contrasts have come under attack, not from metaphysicians but from philosophers who would in a general sense be happy enough to describe themselves as "logical empiricists." Even among those philosophers who would still wish to make the contrasts on which the logical positivists insisted, few would believe that they can be made with the sharpness or the ease that the logical positivists at first suggested.
Logical positivism, then, is dead, or as dead as a philosophical movement ever becomes. But it has left a legacy behind. In the German-speaking countries, indeed, it wholly failed; German philosophy, as exhibited in the works of Martin Heidegger and his disciples, represents everything to which the positivists were most bitterly opposed. In the United States, Great Britain, Australia, the Scandinavian countries, and in other countries where empiricism is widespread, it is often hard to distinguish the direct influence of the positivists from the influence of such allied philosophers as Russell, the Polish logicians, and the British "analysts." But insofar as it is widely agreed that transcendental metaphysics, if not meaningless, is at least otiose, that philosophers ought to set an example of precision and clarity, that philosophy should make use of technical devices, deriving from logic, in order to solve problems relating to the philosophy of science, that philosophy is not about "the world" but about the language through which men speak about the world, we can detect in contemporary philosophy, at least, the persistence of the spirit that inspired the Vienna circle.
See also Absolute, The; Analysis, Philosophical; Ayer, Alfred Jules; Basic Statements; Carnap, Rudolf; Duhem, Pierre Maurice Marie; Einstein, Albert; Emotive Theory of Ethics; Empiricism; Epicurus; Epistemology, History of; Frege, Gottlob; Gödel, Kurt; Heidegger, Martin; Helmholtz, Hermann Ludwig von; Hempel, Carl Gustav; Hume, David; Kant, Immanuel; Language; Leibniz, Gottfried Wilhelm; Mach, Ernst; Metaphysics; Mill, John Stuart; Neo-Kantianism; Neurath, Otto; Planck, Max; Poincaré, Jules Henri; Popper, Karl Raimund; Positivism; Ramsey, Frank Plumpton; Reichenbach, Hans; Russell, Bertrand Arthur William; Ryle, Gilbert; Schlick, Moritz; Tarski, Alfred; Utilitarianism; Verifiability Principle; Wittgenstein, Ludwig Josef Johann.
The essays by leading logical positivists included along with an introduction by Ayer and an extensive bibliography in Alfred J. Ayer, ed., Logical Positivism (Glencoe, IL: Free Press, 1959), are the best introduction to the movement as a whole. Other representative writings by members of the Vienna circle and its associates include the following: Alfred J. Ayer, Language, Truth and Logic (London: Gollancz, 1936; 2nd ed., 1946). Rudolf Carnap, Der Logische Aufbau der Welt (Berlin: Weltkreis, 1928), translated by R. George as The Logical Structure of the World (London: Routledge and Kegan Paul, 1967); "Die physikalische Sprache als Universalsprache der Wissenschaft," in Erkenntnis 2 (5–6) (1932): 423–465, translated by Max Black as The Unity of Science (London: Kegan Paul, 1934); Logische Syntax der Sprache (Vienna: Springer, 1934), translated by Amethe Smeaton as The Logical Syntax of Language (London and New York: Kegan Paul, 1937); Philosophy and Logical Syntax (London: Kegan Paul, 1935); "Testability and Meaning," in Philosophy and Science 3 (4) (1936): 419–471, and 4 (1) (1937): 1–40; Meaning and Necessity (Chicago: University of Chicago Press, 1947); "Empiricism, Semantics and Ontology," in Revue internationale de philosophie 4 (11) (1950), reprinted in Semantics and the Philosophy of Language, edited by Leonard Linsky (Urbana: University of Illinois Press, 1952), pp. 208–228; and "Intellectual Autobiography" and "Reply to My Critics," in The Philosophy of Rudolf Carnap, edited by P. A. Schilpp (La Salle, IL: Open Court, 1963).
See Herbert Feigl and May Brodbeck, eds., Readings in the Philosophy of Science (New York: Appleton-Century-Crofts, 1953), and Herbert Feigl and Wilfrid Sellars, eds., Readings in Philosophical Analysis (New York: Appleton-Century-Crofts, 1949), for articles by Carnap, Feigl, Reichenbach, Hempel, Frank, and Zilsel. See also Philipp Frank, Modern Science and Its Philosophy (Cambridge, MA: Harvard University Press, 1949); Victor Kraft, Der Wiener Kreis, Der Ursprung des Neopositivismus (Vienna: Springer-Verlag, 1950), translated by Arthur Pap as The Vienna Circle (New York: Philosophical Library, 1953); Jørgen Jørgensen, The Development of Logical Empiricism (Chicago: University of Chicago Press, 1951); Charles W. Morris, Logical Positivism, Pragmatism and Scientific Empiricism (Paris: Hermann, 1937); Otto Neurath, Einheitswissenschaft und Psychologie (Vienna: Gerold, 1933) and Le développement du Cercle de Vienne et l'avenir de l'empiricisme logique (Paris: Hermann, 1935); Hans Reichenbach, The Rise of Scientific Philosophy (Berkeley: University of California Press, 1951); Karl Raimund Popper, Logik der Forschung (Vienna: Springer, 1935), translated with new appendices by the author, with the assistance of Julius Freed and Lan Freed, as Logic of Scientific Discovery (London: Hutchinson, 1959); Moritz Schlick, Allgemeine Erkenntnislehre (Berlin: Springer, 1918), Fragen der Ethik (Vienna: Springer, 1930), translated by D. Rynin as Problems of Ethics (New York: Prentice Hall, 1939), and Gesammelte Aufsätze (Vienna: Gerold, 1938), partially republished as Gesetz Kausalität und Wahrscheinlichkeit (Vienna: Gerold, 1948); and Ludwig Wittgenstein, Tractatus Logico-Philosophicus, German version as Logisch-Philosophische Abhandlung in Annalen der Naturphilosophie 14 (1921): 185–262, English translation by C. K. Ogden (London: Routledge, 1922; rev. ed., New York: Humanities Press, 1961); Philosophical Investigations (Oxford: Blackwell, 1953).
See also Richard von Mises, Kleines Lehrbuch der Positivismus (The Hague: W. P. van Stockum, 1939), translated as Positivism: A Study in Human Understanding (Cambridge, MA: Harvard University Press, 1951); G. Bergmann, The Metaphysics of Logical Positivism (London: Longmans Green, 1954); Frederick C. Copleston, Contemporary Philosophy (London: Burns and Oates, 1956); Ernest Nagel, Logic without Metaphysics (Glencoe, IL: Free Press, 1956); John Arthur Passmore, "Logical Positivism," in Australasian Journal of Psychology and Philosophy 21 (1943): 65–92, 33 (1944): 129–153, and 26 (1948): 1–19, and A Hundred Years of Philosophy (London: Duckworth, 1957); James O. Urmson, Philosophical Analysis (Oxford: Clarendon Press, 1956); and Julius R. Weinberg, An Examination of Logical Positivism (London: Kegan Paul, 1936).
John Passmore (1967)
LOGICAL POSITIVISM . Narrowly defined, logical positivism was an organized, science-oriented movement centered in Vienna during the 1920s and 1930s, a movement severely critical of metaphysics, theology, and traditional philosophy. Also known as logical empiricism, logical positivism may be more broadly defined as a doctrine born of classical empiricism and nineteenth-century positivism and sharpened by an empirical interpretation of the early logical writings of Ludwig Wittgenstein (1889–1951).
In either case, the distant origins of logical positivism lie in the long history of philosophical empiricism, the tradition holding that all knowledge must be derived from human experience alone. More particularly, the empiricism of John Locke (1632–1704), George Berkeley (1685–1753), and David Hume (1711–1776), with their cumulatively ever more radical elimination of nonempirical sources of knowledge, served as inspiration for the scientific views of the influential Vienna physicist and theorist of science, Ernst Mach (1836–1916). In addition, the positivist movement of the nineteenth century, founded by Auguste Comte (1798–1857), with its intense admiration for natural science, its anticlerical and antimetaphysical commitments, and its self-conscious programs for social and religious reform, lay behind not only Mach but also the small group of mathematical, natural, and social scientists who gathered in Vienna as early as 1907 to discuss Mach's views. In 1922 this group was successful in bringing Moritz Schlick (1882–1936), who was scientifically trained under the great German physicist Max Planck (1858–1947) but also keenly interested in philosophical issues, to the chair once held by Mach at the University of Vienna. Schlick quickly drew around him a circle of like-minded thinkers, mainly from the sciences, some of whom formed in 1928 the Verein Ernst Mach (the Ernst Mach Society). What soon became known as logical positivism was formulated by this group. The Vienna Circle, as they came to be known, issued a "manifesto" in 1929, organized international meetings, and in 1930 took over a journal, renamed Erkenntnis, for the advancement of its increasingly sharp position.
The distinctively "logical" character of the radically empiricist Vienna Circle was derived from the careful study (a line-by-line examination from 1924 to 1926) of Wittgenstein's Tractatus Logico-Philosophicus, which had been completed by 1918 and first published in 1921 (in German under the title Logisch-philosophische Abhandlung ), just prior to the formation of the Vienna Circle. Wittgenstein was never a member of the Circle and was not sympathetic either to its party spirit or to the "grandiloquence" of its pronouncements, but from 1927 to 1929 he engaged in conversations with Schlick and other members of the Circle. Wittgenstein's logical doctrine formed the Circle's sharpest weapon against metaphysics and theology: the characterization of them not merely as false or outmoded, as Comte and the classical positivists had claimed, but as strictly "nonsense."
It was from Wittgenstein that the Vienna Circle drew its insistence that all meaningful statements are either analytic (and logically certain merely because they are tautologies) or synthetic (and "truth-functionally" analyzable into basic propositions corresponding to ultimately simple facts). The Circle gave its own characteristic interpretation of what qualified as these "atomic facts": sense-experiences. With this interpretation came support for two of the Circle's three primary positions: (1) the doctrine of the unity of science, Mach's key project, on the ground that all the sciences can be reduced equally to variously complex ("molecular") reports on experience; and (2) the doctrine of the valuelessness of metaphysics, on the ground that metaphysical utterances, by attempting to go "beyond" experience, fail to point to simple sense-experiences and thus are devoid of cognitive content.
Both doctrines were incorporated in and defensible by the third, the single most characteristic doctrine enunciated by the logical positivists: the verification principle of meaning, fashioned in light of Wittgenstein's analysis of the logic of language. The principle itself, "the meaning of a proposition is the method of its verification," though not appearing in the Tractatus Logico-Philosophicus, was attributed to a remark by Wittgenstein and was first published in the initial volume of Erkenntnis (1930–1931). In all its many later versions, the verification principle was taken to mean that for any nonanalytic (i.e., any would-be informative) statement, the factual meaning of the statement is equivalent to the set of observations (or sense-experiences, or "observation-statements") that would be sufficient to confirm the assertion's truth. Thus a thoroughgoing empiricist interpretation was given to Wittgenstein's more general dictum, and the authority of a powerful theory of meaning was placed behind the old disavowal of metaphysical or theological claims.
Those purported claims, it was said, must (if nontautological) be equivalent to the sensory experiences that might be obtained by an observer ideally positioned to verify the claim. Such confirming experiences, in the end, are alone what the utterances can mean. But if there are (and could be) no such specifiable experiences, as in the case of utterances allegedly "about" nonsensory entities like "God" or the "Absolute," then literally nothing is conveyed by the language, no real claims are made, and no "entity" can be conceived, much less believed in. So ran the fresh, essentially polemical argument of the logical positivists.
This polemic was generally ignored in the German-speaking philosophical world, doubtless because the Vienna Circle was not perceived (and to a large extent did not perceive itself) as engaging in philosophy so much as in a critique, enunciated mainly by professional scientists on behalf of a scientific method and worldview, of philosophy itself. Some English-speaking philosophers, however, long nurtured in the empiricist tradition that had inspired Mach and the Vienna Circle, were quick to notice the logical positivists. Alfred Jules Ayer (1910–1989) and Gilbert Ryle (1900–1976), of Oxford, and John Wisdom (1904–1993) and Susan Stebbing (1885–1943), of Cambridge, were early interpreters of the movement. Ayer, visiting Vienna in 1933, attended the meetings of the Circle, and in 1936 his book Language, Truth and Logic, containing a logical positivist critique of theology and ethics, exploded onto the English-speaking scene.
This radical challenge to the logical intelligibility of central theological utterances—those ostensibly about God, the soul, life after death, and the like—provoked a reaction that, though muted by the outbreak of World War II, intensified again in the early 1950s after a renewed challenge was issued by Antony Flew (b. 1923). Flew drew upon a variation of the verification principle for his question: what empirical observations would be incompatible with (would "falsify") theological assertions? If the answer is none, then are not the assertions in fact empty of definite, thinkable content? Theologians in the Catholic tradition (Roman or Anglican) tended to answer in terms of traditional doctrines of analogy. Members of the reformed tradition replied in fideistic terms. Neither group offered direct responses to the logical positivist attack. On the other hand, a third group, mainly liberal Protestants (including some Anglicans), attempted to vindicate the cognitive meaningfulness of theological discourse by satisfying the conditions set by the verification principle, specifying experiences that would be relevant to the verification or falsification of the claims in question. John Hick (b. 1922) proposed that claims about God could be verified, but only by postmortem experiences. Basil Mitchell (b. 1917) suggested that ordinary historical events or personal experiences are relevant to the verification of these claims, though not conclusively (as in many complex or ambiguous situations in life). He further suggested that faith-commitments are shown to be cognitively significant precisely because of the anguish sometimes felt in maintaining them against the evidence. R. M. Hare (1919–2002) and John Wisdom agreed that ordinary cognitive content is missing from theological claims but that these utterances might still have importance otherwise, offering comprehensive interpretations of particular experiences.
This variety of replies, to which many others could be added, underscores the distance that the postwar discussion had come from the rigorous either/or position of the Vienna Circle. But the sharp sword of the verification principle had already been blunted on issues at the very center of logical positivist concern: issues involving the adequate analysis of scientific assertions themselves. Try as they might, the members and allies of the Vienna Circle were not able to make good their program to include with the same criteria all scientifically essential statements but to exclude all metaphysical and theological ones. It soon became clear that the laws of science, being entirely universal in form, are not conclusively verifiable, since finite numbers of observations cannot in principle verify a universal assertion. ("Some" examples, however many they may be, cannot verify claims about "all.") Furthermore, the proffered suggestion that scientific laws are not, after all, assertions, as they seem to be, but disguised "rules" or other logical entities was too paradoxical for most science supporters. Again, the apparently definite meaning of even straightforward, particular factual assertions of science and daily life was found to melt away under verificational analysis into an infinite series of possible observations. Reversing the problem to the criterion of "falsification" did not help, since although a universal proposition can be falsified (in principle) by a single negative observation, no particular assertion can be so falsified; furthermore, universal laws of science are not, either in logic or in historical fact, at once falsified by negative observations. At most a whole network of theories is shown to need revision by a negative observational result (since it is not immediately clear which of the premises ought to be discarded and which retained). Moreover, as argued by such historians of science as Thomas S. Kuhn (1922–1996), science does not actually develop in any such logically neat way.
Other applications, not directly fashioned by the Vienna Circle, of verificationism to science—for instance, the attempt of the Harvard physicist P. W. Bridgman (1882–1961) to reduce all concepts in science to descriptions of specific procedures ("operationalism")—resulted in the unsatisfactory conclusion that entirely different concepts (for example, of "length" or "time") would be fashioned by the various sciences, depending on their subject matter and characteristic methods. Far from supporting the unity of science, which was a central motive in the founding of the logical positivist movement, operationalism tended to make it logically impossible for astronomy, which measures distance by various sorts of procedures, to share a common concept of distance with geology, biology, or microphysics, which rely upon others. Indeed, even within the same science—or within the same laboratory on different occasions—scientifically essential conceptual generality was seen to be forfeited by the particularistic reductionism of operationalism.
Equally alarming to many more realistically minded scientists and friends of science was the problem of retaining a (non-"metaphysical") concept of the common world studied by science if the meanings of all factual propositions are to be literally equated with those experiences that could verify them. Since experiences are personal and private, the traditional problem of "other minds" (i.e., of how I can escape solipsism if other centers of consciousness are not directly observable by me) was added to the problem of escaping from absolute idealism (i.e., the alarmingly traditional metaphysical view that nothing exists except mentality), even if the egocentric predicament somehow could be avoided.
Finally, the logical status of the verification principle itself could not withstand verificationist analysis. The principle is not just another empirical hypothesis: that is, it certainly does not offer a foothold for confirmation (or falsification) by sense-experiences. Is it then an empty tautology? Most logical positivists took the latter position, holding that the principle was an "important" tautology that had many good reasons for being "recommended" to the intellectual community. This tack, however, allowed others, like Hare and Wisdom, to speak of equally "important" nonverifiable utterances and to make more complex counterrecommendations about the meaning of "meaning."
The disintegration of the organized Vienna Circle can be dated from the murder by a deranged student of Schlick in 1936. Viewed with hostility by the Nazis, the Vienna Circle was formally disbanded in 1938, and in the same year Erkenntnis was moved out of Hitler's direct sphere of control, to Holland, where it lasted only another two years. The end of the broader movement is harder to trace, and in some fashion it remains influential as an overtone in the more radically empirical voices of our time. Still, the gradual abandonment by Wittgenstein of his own either/or position on meaning in the Tractatus Logico-Philosophicus, in favor of a much more pluralistic approach to the functions of human language, pulled the logical rug out from under logical positivism. Its significance for religion and theology continues to lie in the fact that theologians now have been forced to acknowledge the extent to which their claims cannot be treated as simple empirical hypotheses, open to "crucial experiments," as in the contest between Elijah and the priests of Baal (1 Kgs. 18:17–40). Indeed, it may be thought that theology has emerged the better for its cold bath in verificationism, if only because theologians are now required to be aware of the subtlety of their speech and of the many functions it may have both in their technical discourses and in the living religious speech of the faithful.
No single book is more important for the understanding of logical positivism than Ludwig Wittgenstein's difficult but fascinating Tractatus Logico-Philosophicus (London, 1922). As a general guide to Wittgenstein's thought and to the Tractatus in particular, one might turn to part 1 of George Pitcher's helpful The Philosophy of Wittgenstein (Englewood Cliffs, N.J., 1964). The thought of the founder of the Vienna Circle is reflected in Moritz Schlick's posthumously published Gesammelte Aufsätze 1926–36 (1938; reprint, Hildesheim, 1962). Other representative writings of the Vienna Circle can be found in Rudolf Carnap's The Logical Structure of the World (London, 1967) and in Foundations of the Unity of Science, vol. 2 of International Encyclopedia of Unified Science, edited by Otto Neurath, Rudolf Carnap, and Charles Morris (1938–1962; reprint, Chicago, 1955–1970). The explosive introduction of logical positivism to the English-speaking world was through Alfred Jules Ayer's Language, Truth and Logic (London, 1936). After World War II, the key book in focusing the theological aspect of the controversy was New Essays in Philosophical Theology, edited by Antony Flew and Alasdair MacIntyre (London, 1955). One of the important sustained efforts to meet the challenge by offering theological verification of a sort, though not in this life, was John Hick's Faith and Knowledge, 2d ed. (Ithaca, N.Y., 1966). A detailed analysis of the arguments leading to the verificationist challenge to religious belief, of various attempted replies, and of the transformation of the issues resulting from this debate can be found in the first chapters of my Language, Logic, and God (New York, 1961). The best recent survey of the whole phenomenon of logical positivism, readable and authoritative, is Oswald Hanfling's Logical Positivism (New York, 1981).
Coffa, Alberto. The Semantic Tradition from Kant to Carnap: To the Vienna Station. 1991; reprint New York, 2003.
Fitch, G. W. "On Theoretical Identifications." Philosophical Perspectives 11 (October 2001): 379–393.
Friedman, Michael. Reconsidering Logical Positivism. New York, 1999.
Jones, Todd. "The Virtues of Nonreduction, Even When Reduction Is a Virtue." Philosophical Forum 34 (Summer 2003): 121–141.
Sarkar, Sahotra. Decline and Obsolescence of Logical Empiricism: Carnap vs. Quine and the Critics. Science and Philosophy in the Twentieth Century: Basic Works of Logical Empiricism. New York, 1996.
Schaffer, Jonathan. "Is There a Fundamental Level?" Nous 37 (September 2003): 498–518.
Frederick FerrÉ (1987)
The term logical positivism is particularly associated with the so-called Vienna Circle, a group of leading philosophers, mathematicians, and scientists that met in Vienna, Austria, in the late 1920s and early 1930s, with German philosopher Moritz Schlick (1882–1936) as chairman. They put forward what they regarded as a "scientific world-conception," which was both anticlerical and opposed to metaphysics. It was, they believed, characterized by two main features. The first was a general empiricism, and the second a devotion to a certain rigorous way of thinking that they called logical analysis. This relied particularly on the techniques of modern formal logic.
Empiricism, in the tradition of such philosophers as David Hume (1711–1776), holds that knowledge can only be obtained from direct experience. Although explicitly a science-based philosophy, it always causes problems for science because science always wishes to generalize from present experience through induction. A strict empiricism will, however, wish to deduce all claims to knowledge from the direct experience of which we are infallibly aware. Knowledge is the product of our pooled, intersubjective experience. What is beyond the reach of human perception and observation cannot be judged to be real. In its effects, the view becomes centered on human judgment and dependent on human capabilities. It is anthropocentric in that it will only deal with what exists in so far as it is accessible to human experience. The latter is defined in terms of what is "immediately given." In other words, what is in principle beyond the reach of the human senses cannot be meaningfully discussed. Science defines what it is possible to know, and a strict empiricism sets the limits, as the manifesto for the Vienna Circle puts it, "for the content of legitimate knowledge" (p. 309).
The Circle held that "the meaning of every statement of science must be statable by reduction to a statement about the given" (p. 309). This puts the whole of science (and hence, they believed, of knowledge) on a firm empirical footing. It is, however, worth noting that, even at the time, it was questionable whether this gave an adequate account of physics. Modern quantum mechanics has been plagued by disputes about the status of subatomic particles. These disputes often themselves stem from positivist views about the dependence of knowledge on sense experience. The difficulty is how far we can posit entities that by definition we cannot observe. Can they be thought really to exist even though they cannot be directly observed? That these kinds of questions were major stumbling blocks can be illustrated by considering that for logical positivists even the issue of the other side of the moon was a problem before humans had actually observed it. They could only say that it could be observed "in principle," and indeed it was eventually observed by humans. There are, however, many items to which modern physics wishes to refer that cannot be observed even in principle, unless those words are stretched beyond any recognizable use. What of the other side of the universe, or the interior of a black hole, not to mention quarks and other subatomic particles?
The influence of the Vienna Circle
The fame and influence of the Vienna Circle began to be felt in the 1930's. Such eminent figures as philosophers Rudolf Carnap (1891–1970), Herbert Feigl (1902–1988), and Friedrich Waismann (1896–1959), mathematician Kurt Gödel (1906–1978), and sociologist and economist Otto Neurath (1882–1945) were members, and their own individual influence was spread as they were all scattered across the globe as a result of the political upheavals of the 1930's in Central Europe, leading up to the Second World War. Other well-known figures were associated in some ways with the Circle. They tended to see Ludwig Wittgenstein (1889–1951) as one of their own, although, particularly in his later philosophy, he reacted very much against the idea that only science could set the standard for knowledge. Philosopher Karl Popper (1902–1993) also betrays some of the influence of the Circle, not least by arguing that the test for science was its ability to test empirically its theories by seeing if they could be falsified. This was a variation on the Circle's insistence of being able to test scientific theories through empirical verification. His argument was that conclusive verification was impossible to achieve. One can never know that all members of a class have been seen. For example, it is better policy to try to refute the theory that all swans are white than to seek to confirm it. A single black swan will be enough to falsify the theory. Popper's philosophy of science is therefore geared to making conjectures and attempting to refute them, rather than trying to confirm them. The result inevitably implies a certain agnosticism about scientific truth. Theories always have to be tested for possible falsehood. Yet we cannot know that they are true but only that they have so far survived scrutiny.
W. V. O. Quine. Two other philosophers attended the meetings of the Circle and were influenced by its outlook. W. V. O. Quine (1908–2000) was one of the leading American philosophers of the twentieth century and put forward a science-based philosophy. He was, however, also influenced by American pragmatism and criticised some of the Vienna Circle's basic tenets. In particular, it was held that all statements were either synthetic (subject to empirical checking and verification) or analytic (true by definition or by virtue of the meanings of the words used). An example of a synthetic statement would be, "All swans are white." One can discover there are black swans. Analytic statements would include, "All bachelors are unmarried" and "Two and two are four." One could not discover either statement to be false by looking at the world. Quine, however, challenged the whole analytic-synthetic distinction, and in so doing, undermined much of its empiricism. He also made space for theoretical entities, such as electrons, which might not be cashed out wholly in empirical terms. He did, however, continue in the belief, strongly held by the Circle, that philosophy was to be subordinated to science, and that there was no room for metaphysics, which could justify the practice of science in the first place.
A. J. Ayer. The other major philosopher who attended meetings of the Circle was A. J. Ayer (1910–1989). He became the voice of logical positivism in the English-speaking world through the publication of his influential Language, Truth and Logic. First published in 1936 as the first book of a young man, it argued that meaningful statements were to be divided into the two categories of the analytic and synthetic. Any other category of statement had to be dismissed as meaningless. He thus dismissed all metaphysics, and that explicitly included religious statements about God. Genuine statements of fact had to be empirically verifiable. Nothing could be factually significant to people unless they knew how to verify the proposition it purports to express. This was the criterion of verifiablity or the verification principle.
Since the existence of God is not a mere tautology (true by definition), according to Ayer, it could only be a factual statement with empirical consequences. His argument can be illustrated by the way he deals with the suggestion that the occurrence of regularities in nature could be evidence for the existence of God. Yet, according to Ayer, if the claim that there is a god amounts empirically to no more than the claim that certain types of phenomena occur in certain sequences, then talking of God is equivalent to talking of those regularities. Ayer could not allow reference to anything beyond our experience. Speaking of the transcendent, like the metaphysical, was just so much hot air, not a genuine assertion of anything. A parallel might be the claim that there is a heffalump in the garden. If a person said there was a heffalump, but did not know what a heffalump looked like, or indeed how to ever recognise a heffalump, it becomes difficult to know what one is saying. Talking of something that is in principle unverifiable becomes perilously like not saying anything at all.
What went for religion also applied to other wide categories of apparent statements, such as those of ethics and aesthetics. They are not scientifically verifiable and therefore cannot be regarded as saying anything that could be true or false. It has already been remarked that even contemporary physics may want to refer to what lies beyond possible human observation, so the verification principle is a blunt instrument even in science. It was commonly seen, though, to get into most trouble when people questioned the status of the verification principle itself. If one states that the only meaningful statements are those that can be empirically verified, or that all metaphysical claims are literally nonsense, how can one empirically verify those assertions? Is not the basic claim itself meaningless because it is beyond the scope of empirical observation? Ayer's later claim was that the verifiability criterion was "an axiom," but particular axioms do not have to be chosen. If someone sees that the adoption of such a rule, or starting point, involved the jettisoning of much that is deemed important in human life, that might seem a good reason for not having the axiom in the first place.
Positivism and the status of science
Despite its shortcomings, Ayer's verification principle, and the veneration for science expressed by the repudiation of metaphysics, had a profound affect on theology and the philosophy of religion for many years in the middle of the twentieth century. In many ways, logical positivism still casts its shadow. The idea that religion is not entitled to talk of realities beyond human experience is a seductive one. Yet it strikes at the root of any belief that the physical world is not all that there is, but that there is another nonmaterial realm. Even within theology, there is a constant temptation to reduce talk of a nonmaterial, transcendent realm, such as the Kingdom of Heaven, to matters of everyday experience. It is still often thought that what cannot ultimately be cashed out in empirical terms cannot refer to anything real. This involves changing our concentration from, say, the reality of God, to issues concerning human reactions, attitudes, and practices. Yet in the end, this is an old-fashioned materialism in a sophisticated guise. It is no different from Thomas Hobbes (1588–1679), the seventeenth-century philosopher, saying that there is no difference between God speaking to someone in a dream and dreaming that God spoke.
In the debate about the relations between science and religion, the legacy of logical positivism is to accord science a philosophical status that is denied metaphysics in general and theology in particular. The tendency will be to assume that the assertions of science have an epistemological priority that theology must always respect. In any dispute science must always be given priority. Yet, logical positivism was an anthropocentric view. It related everything to actual and possible sense experience, which had to be human sense experience. We could not understand claims of radically different kinds of experience. By definition, therefore, it was related to human understanding, and the possibilities of human knowledge. This, though, is different from issues concerning the nature of reality. Science is always human science, but it purports to be about a reality that goes beyond, or transcends, our limited and provisional understanding. Philosophy, and metaphysics in particular, has to recognise these limitations. We have to accept that what exists and how we can know it, are radically different kinds of question. This is the difference between ontology and epistemology. The mistake of the Vienna Circle and those it has influenced is to reduce references to what exists to talk of how we can find it out, when who "we" are is not always clearly defined. Any exaggerated respect for science never makes it clear whether it is upholding present science, or science as it one day could be. Yet the latter idea itself begins to seem highly metaphysical in the sense that it outstrips any possible method of verification at present available to us.
Logical positivism represents the extreme version of the respect for science that permeates contemporary thinking. Yet the status of science is itself an issue of major philosophical concern that cannot be taken for granted. Not least is the fact that science has to assume the existence of an ordered and regular world. This is a resupposition of science. We may as a matter of fact experience nature as uniform, but why is this? Why do humans have the ability, through reason, to understand the innermost workings of the physical world? Why is mathematics somehow applicable to the workings of nature? For logical positivism, questions like these were insoluble, and therefore meaningless in the first place. Yet the worst way of dealing with awkward questions is to pretend that they do not exist on the grounds that they are meaningless.
See also Critical Realism; Empiricism; Philosophy of Science
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A contemporary philosophical movement that aims to establish an all-embracing, thoroughly consistent empiricism based solely on the logical analysis of language. Because of its anti-metaphysical bias, militantly propagated by its founders and some prominent adherents, the movement constitutes a serious challenge to traditional philosophy and religion. In what follows, consideration is given to its historical development, its principal proponents and some of their antecedents, its philosophical tenets and how these evolved, and a critical evaluation.
Origins with the Vienna Circle. The logical positivist movement began with a small group of philosophers and scientists later known as the Vienna Circle (Wiener Kreis). The group had formed itself around Moritz Schlick, a former physicist who was appointed to the chair of philosophy of the inductive sciences at the University of Vienna in 1922. Meetings to discuss logical and epistemological problems were held regularly. Among those who joined Schlick were Rudolf Carnap, Hans Hahn, Otto Neurath, Herbert Feigl, Philipp Frank, Freidrich Waismann, and Edgar Zilsel. Most of these men had developed an interest in philosophy as an outgrowth of their work in physics, mathematics, or mathematical logic.
In the fall of 1929 the Vienna Circle published a document written by Carnap, Hahn, and Neurath, and dedicated to Moritz Schlick, titled Wissenschaftliche Weltauffassung: Der Wiener Kreis. In this statement of "scientific outlook" they set forth the two aims of the group: (1) to establish a firm foundation for the sciences, and (2) to demonstrate the meaninglessness of all metaphysics. The method proposed for accomplishing these aims was the logical analysis of statements.
A decisive influence in the early years of the Vienna Circle was that of Ludwig wittgenstein, whose Logisch-Philosophische Abhandlung had been published in 1921. Although he did not attend the meetings, Wittgenstein was in personal contact with Schlick and Waismann, and his views provided the basis for many discussions.
Convinced that their cooperative efforts were producing results, the members of the Vienna Circle reached out to form alliances with other rising positivist groups in Germany, Scandinavia, Poland, and England. Hans Reichenbach of the Berlin school of scientific philosophy was among those who became closely associated with the growing movement. A series of international congresses was inaugurated in 1929. An existing journal, Annalen der Philosophie, was taken over in 1930, renamed Erkenntnis, and edited by Carnap and Reichenbach as the organ of the new positivism. Other cooperative publishing ventures were also undertaken.
In the next decade, however, the Vienna Circle disintegrated. Schlick had died in 1936; Hahn, before him. The departure of many original members—among them Carnap, Frank, Waismann, Neurath, and Feigl—for universities in England and the U.S. led to a new development. Its influence all but over in central Europe, logical positivism was to become, along with its variant forms, such as analytical philosophy, the dominant philosophical movement in Scandinavia and the English-speaking world.
Basic Teachings. Logical positivism is not unique in the history of philosophy for its rejection of metaphysics. Early British empiricism had developed in this direction, culminating in the doctrine of hume with its decisive influence on kant. On the European continent, Auguste comte had proclaimed the end of the "metaphysical stage" in human intellectual history (see positivism). American pragmatism, in doctrine and spirit, and the whole scientific temper of the 20th century favored a strict empiricism.
What distinctly characterizes the logical positivists is their explicit resolve to eradicate metaphysics and to make empiricism a matter of logical necessity. Not content merely to abandon metaphysics as beyond human grasp, nor to cast it aside as having outlived its usefulness, they set out to show that every attempt to make a metaphysical statement, or even to ask a metaphysical question, results inevitably in nonsense. They questioned not the limits of human knowledge but the limits of meaningful linguistic expression.
Logical Foundations. This approach to philosophy was made possible by the development of modern mathematical logic from Peano and Frege to Bertrand russell and Ludwig Wittgenstein. Of particular importance to logical positivism is the doctrine of propositions worked out by Russell and Wittgenstein, but based upon earlier suggestions in the writings of leibniz, Hume, and Kant (see logic, symbolic; logic, history of).
Logical positivists, following Wittgenstein, hold that there are two distinct types of propositions: (1) tautologies, which are evidently and necessarily true, but say nothing about the world; and (2) factual propositions, which refer to the world of experience, but are at best probable. These latter are either elementary statements, corresponding to absolutely simple "atomicfacts," or complex statements constructed from, and resolvable into, the first. No logically necessary proposition says anything about reality. The propositions of logic and mathematics, though certain and necessary, are devoid of factual content; they are all tatuologies, that is, so many varied ways of saying "A is A."
The function of factual propositions is to enable us to "anticipate the course of our sensations." Unavoidably hypothetical, they must repeatedly be put to the test of experience, and they are verified whenever the observations they lead one to expect are forthcoming. This predictive character is essential to factual propositions.
Verification and Metaphysics. By classifying all genuine propositions into tautologies and those empirically verifiable, logical positivists so define meaningful discourse that metaphysics becomes logically impossible. They proceed, nonetheless, to "demonstrate" the meaninglessness of metaphysical statements by invoking their criterion of meaning, the "verification principle" (see verification).
The formulation of this key principle has been a continuing point of contention in the logical positivist movement. It was soon recognized that to demand conclusive verifiability for meaningfulness was to exclude empirical hypotheses. So this requirement was quickly abandoned. Another formulation of the principle required that a statement at least be supportable by some elementary statements.
Schlick himself had held that the meaningfulness of a proposition depends upon the "logical possibility" of verification, not upon its actual confirmation. By this he meant that the existence of circumstances in which a statement might be verified must not be contradictory. To state the meaning of a sentence, he held, is to describe the circumstances in which it is to be used, for "the meaning of a proposition is the method of its verification" (see semantics). This assertion is quite fundamental to logical positivism. From it the meaninglessness of any discourse about objects transcending the empirical order follows directly. Thus the term "metaphysical," used by logical positivists to cover all non-empirical attempts to speak about reality, becomes equivalent to "nonsensical." In their understanding, the whole of reality is the exclusive domain of empirical science.
Ethics and Religion. At first logical positivists disagreed on the status of ethics. Schlick held that ethical statements are factual propositions about what people approve or disapprove, their actual standards of behavior, and their actual motives. This would make ethics an empirical science, in no essential way distinct from the physical sciences. Such a position never won general acceptance in the movement.
The view of ethics that gradually prevailed is based upon the notion of "emotive meaning." According to this theory, the normative statements of ethics are cognitively meaningless but have "emotive" significance. This means, in A. J. Ayer's terms, that they are "pure expressions of feeling," "moral sentiments" that "do not say anything." C. L. Stevenson, who later developed the emotive theory at greater length, describes ethical statements as expressions of approval or disapproval that are intended to exert persuasive force upon others.
The majority of logical positivists considered that they had sufficiently disposed of religious and theological questions by their treatment of metaphysics. Ayer, however, applies the positivist criterion of meaning to the question of God's existence in an effort to disassociate the logical positivist position from athesim and agnosticism. Rather than asserting the nonexistence of God, as does the atheist, or proclaiming himself, like the agnostic, ignorant as to whether or not God exists, the positivist rejects the very question of God's existence as meaningless, and declares the atheist's answer, no less than the theist's, nonsensical. The theist is thus offered the "comfort" of knowing that he can never be accused of saying anything false. Furthermore, there can be no conflict between religion and science, since there are no genuine theological propositions to oppose the propositions of science.
Such complete frankness makes superfluous any further exposition of the incompatibility of logical positivist doctrines with any religious doctrine that is proposed as true.
From the first, logical positivists were aware that their doctrines were being attacked as destructive of religion, morality, and even of philosophy. The charge of opposition to religion they readily admitted, Ayer observing only that this puts them in excellent philosophical company. With morality itself they had no quarrel. Their interest in denying the cognitive significance of ethical propositions concerns simply a point of logic—the distinctness of the emotive from the scientific order.
Role of Philosophy. The question of what function remains for philosophy now that it has lost its former domains never ceased to disturb logical positivists. One answer with support from the start was that philosophy is simply a branch of logic. This was the position of Rudolf Carnap, who declared without hesitation that the only proper task of philosophy is the logical analysis of scientific concepts and propositions.
For Schlick, a "great turning point" came when philosophy ceased to be regarded as a science in its own right with propositions of its own. With nothing to say itself, philosophy becomes the "activity" of making scientific propositions clear, leaving to the sciences the task of stating the truth about things.
This conception of philosophy grew, at least in part, out of Wittgenstein's early teaching that philosophy's total function is negative: it exposes lapses into metaphysical utterance thereby rescuing man's intelligence from its "bewitchment" by language. Philosophical problems are not solved; they just "dissolve." Yet Wittgenstein's final advice to discard even the propositions of his book as nonsense (after having made use of them) disturbed some of his disciples. Carnap charges him with inconsistency, and Ayer suggests that there are philosophical propositions after all, viz, those that constitute books such as Ayer's own. Holding these to be tautologies, Ayer rejoins Carnap in making philosophy a branch of logic.
Critique and Evaluation. This did not end the logical positivists' struggle, in the grip of their own basic principles, to create a role for themselves as philosophers. Friedrich Waismann, prominent in the original discussions of the Vienna Circle, was moved, by 1956, to observe that it is "nonsense" to say that metaphysics is nonsense. Later, considering again the frequently voiced objection that the verification principle is itself unverifiable, Ayer continued to shun the suggestion that it might be nonsense, but could offer little in its defense, He conceded that, if a metaphysical statement is neither a tautology nor a scientific hypothesis, it does not follow that it is meaningless, unless one "makes it follow"—a procedure that, he observes, has proved useful for banishing metaphysicians from the domain of science.
This is a telling observation. It points to the practical concern behind the logical positivist movement and dispels the image of a doctrine growing out of inexorable laws of logic. It calls attention to the circumstance that the early founders of logical positivism were predominantly men of a scientific outlook, chiefly concerned with what they regarded as metaphysical encroachments within science.
Apart from this, however, there are valuable truths to be drawn from the movement. By insisting upon clarity of thought and precision in the use of language, and by calling into question rationalist and idealist modes of philosophizing, logical positivists have served both philosophy and science. Many of them have shown themselves to be exceptionally competent philosophers. Their analyses have, at times, placed them firmly on the side of common sense. But what is more important, by their radical challenge to the survival of traditional philosophy they have compelled those who would resist them to take seriously their obligation to be true philosophers.
None of these factors, however, removes the basic philosophic weaknesses of logical positivism; nor do they mitigate its basic incompatibility with a religion that promises anything to the mind of man.
See Also: metaphysics, validity of.
Bibliography: a. j. ayer, Logical Positivism (Glencoe, IL 1959); Language, Truth and Logic (2d ed. New York 1957). j. r. weinberg, An Examination of Logical Positivism (New York 1936). c. l. stevenson, Ethics and Language (New Haven 1944). v. kraft, The Vienna Circle: The Origin of Neo-Positivism, tr. a. pap (New York 1953). o. neurath et al., Wissenschaftliche Weltauffassung: Der Wiener Kreis (Vienna 1929).
[m. f. griesbach]