RATIONALISM.

In the final section of the Critique of Pure Reason, Immanuel Kant distinguishes empiricism and rationalism:

In respect of the origin of the modes of "knowledge through pure reason," the question is as to whether they are derived from experience, or whether in independence of experience they have their origin in reason. Aristotle may be regarded as the chief of the empiricists, and Plato as the chief of the noologists [rationalists]. Locke, who in modern times followed Aristotle, and Leibniz, who followed Plato … have not been able to bring this conflict to any definitive conclusion. [Kemp Smith, trans.]

Kant's vision of a conflict between empiricism and rationalism remains to this day the organizing principle for discussions of early modern metaphysics and epistemology. Kant may have overstated the extent to which there was a conflict between empiricists and rationalists: it has recently been suggested that both may be seen as pursuing the common project of defining the scope and limits of human knowledge. It has also been charged that the very distinction between empiricism and rationalism should be rejected. I believe that the distinction usefully captures certain defining features of early modern philosophy and that the terms rationalism and empiricism should be retained.

Rationalism Defined

Kant's characterization of rationalism is generally accurate. One addition must be made. Like most early modern philosophers, the rationalists conceived of the human cognitive faculties as distinguished into the pure intellect, the senses, and the imagination. The pure intellect was the faculty that enabled human beings to gain knowledge. Rationalism may be defined as the view that substantive truths about the nature of reality may be derived from the pure intellect alone, operating independently of the imagination and the senses.

The Roots of Rationalism

It was by no means idiosyncratic for Kant to take Plato and Aristotle as prefiguring the opposition between rationalism and empiricism; this opposition is, for example, the organizing principle of Raphael's Vatican fresco The School of Athens. Plato points up, to the realm of Forms, the unchanging objects of the pure intellect; Aristotle points to the earth, thereby indicating the experiential origin of knowledge. Plato's commitment to the existence of unchanging truths, sharply contrasted with the variable images of the senses, marks him as the grandfather of early modern rationalism.

Approximately five hundred years later, Saint Augustine synthesized Plato's philosophy with the Christian religion in order to provide the latter a philosophical underpinning. Augustine found in Plato a remedy for the vagaries of sense experience that threatened the truth of Christianity; his work remained seminal for the early modern rationalists: Descartes, Leibniz, and Malebranche, believers all, explicitly hearkened back to Augustine. Aristotle's work, however, held its importance for medieval philosophers. He became known as "the Philosopher," and his thought, especially as interpreted by Aquinas, became the official philosophy of Christianity.

René Descartes

Descartes formulated his conception of philosophy in explicit opposition to the Scholastic Aristotelians' emphasis on sense-based experience. The Meditations are best understood as a series of cognitive exercises that train the meditator to discover truths about the world by the use of pure intellect, independent of the senses. Beginning by purging the self of intellectual preconceptions, by doubting all knowledge hitherto received through the senses, the meditator rebuilds knowledge, achieving clear and distinct ideas of the nature of the soul, God, and body.

The Meditations was not a complete system of philosophy; it only laid the foundation for Descartes's broader philosophical project. Descartes explains in a letter to his friend Marin Mersenne that "my little book on metaphysics contains all the foundations of my physics." The point of the Meditations was to reconceptualize the physical world as a realm of extension, governed by laws of motion, and therefore amenable to mathematical investigation. Descartes envisioned his physics very broadly, extending his view from celestial bodies to terrestrial bodies, the operations of animals, and the nature of the human being. He meant for his scientific project to culminate in the Principles of Philosophy, which remained unfinished, although the broad lines of Cartesian science may be derived from other works.

Although Descartes turned to philosophy (metaphysics) in order to ground science and thought that the only genuine knowledge that human beings could achieve derived from the intellect operating independently of the senses, he nevertheless retained an important place in science for the senses. General truths about body only specify the possible range of explanations of physical phenomena; in order to determine the particular explanations, one must appeal to sense experience. Cartesian rationalism remains limited to the most general truths about the universe.

Benedict Spinoza

Spinoza is the only Jewish thinker among the rationalists. He was excommunicated from the Jewish community of Amsterdam, possibly on account of the heretical views that he held about the nature of God and the immortality of the soul, views later elaborated in his great systematic work, the Ethics. Spinoza's philosophical system is the purest example of rationalism.

Other rationalists remained committed to the truths of revealed religion; Spinoza maintains that the Bible does not contain the word of God, but is a work of men that serves the sociopolitical ends of establishing and securing the commonwealth. In his Theological-Political Treatise, Spinoza therefore argues that human beings should be free to hold whatever religious views they like, provided they do not upset the established civil order.

This work is a prolegomenon to the Ethics, where, on the basis of reason alone, Spinoza radically reconfigures traditional notions of God, nature, and morality. Rejecting all sensory inputs as mere "random experience" that do not reveal the nature of the world, he says there is only one substance, which he strikingly calls "God or nature." All existing things must be understood to be merely modifications of that single substance, not substances in their own right. One of the most provocative aspects of Spinoza's vision of the universe, which drew sustained criticism from his contemporaries, is his claim that all events are determined by God to occur. Indeed, he maintains, even God does not freely choose to create the world—this in sharp contrast to traditional views of God as creator—but is determined by his own nature to produce what exists in the world. This determinism renders the structure of nature intelligible to the human intellect.

By understanding the necessary and eternal order of the world, humans may come to understand both their place in the world and what they ought to do in the world. By achieving this understanding, they may achieve a kind of nontheological immortality. Their reason, which grasps the unchanging and eternal order of nature, enables them to achieve a kind of immortality as well.

Nicolás Malebranche

Malebranche's philosophical system is a synthesis of Cartesian philosophy and Augustinian theology. In The Search after Truth, Malebranche seeks to remedy human ignorance by presenting the nature of the human mind and showing that it is only by heeding the perceptions of the pure intellect that human beings may achieve knowledge. In the course of elaborating this view, Malebranche develops his two most distinctive doctrines: the vision in God and occasionalism.

The vision in God is Malebranche's account of human knowledge of truths about the world. He claims that human beings may cognize general truths because they have access to those truths in God's mind; they must have access to truths in God's mind because general truths are eternal and infinite and therefore could not be contained in the finite human mind. Occasionalism is a general account of causation, according to which no finite being (whether a mind or a body) is the real cause of any change in the world. Malebranche maintains that a real causal connection must be one that is necessary; however, there is a necessary connection only between God's will and some effect. Consequently, apparent causes are merely occasions for the exercise of God's causal power in accordance with the natural laws constitutive of nature.

In the Treatise on Nature and on Grace, Malebranche deploys these doctrines in order to explain God's action in the created world. He seeks to show that the seeming imperfection of the natural world manifest in natural disasters and the birth of monsters, and the apparent inequality in God's distribution of grace, are merely apparent defects. Because God acts in accordance with general laws, and does not intervene directly to produce particular events, his action in the realms of nature and grace is essentially limited. Malebranche believes that God must act in accordance with general laws because if he were to intervene at every moment in the world, he would not act in accordance with his own nature. Moreover, the world would thereby cease to be intelligible to human beings. Occasionalism, consequently, guarantees the intelligible order of the universe.

Gottfried Wilhelm von Leibniz

Leibniz's philosophical system reflects an overarching commitment to the idea that there is a rational order to the universe that can be grasped by human minds. This commitment is manifest both in his more general epistemological and metaphysical views on display in works like the Monadology and in the philosophical theology contained in the Theodicy.

The foundation of Leibniz's philosophy is simple, soul-like substances, monads, which Leibniz believes are the only genuine substances in the universe. His argument rests on the claim that genuine substances must be simple, something he takes to be immediately evident to the human intellect. All other things—bodies, human beings, and animals—may be broken into their component parts; only minds are indivisible, and therefore only minds are substances.

Substantive metaphysical conclusions follow. Leibniz maintains that there may be no genuine causal interaction between substances, because genuine causal interaction would require that substances could be changed from without, thereby contravening their simplicity. Apparent changes are actually internal changes of substances. Because all changes are correlated with the states of all other monads, this "pre-established harmony" guarantees that apparent causal interactions will be grounded in actual changes in monads.

The idea of harmony lies at the heart of Leibniz's metaphysics. There is a preestablished harmony among the changes of substances; there is also a harmony between the order of nature and the order of grace, which ensures that the moral order will be realized. This point emerges clearly in Leibniz's claim that this is the best of all possible worlds. Here Leibniz seeks to defend God's goodness against the apparent visible evidence of all the evil in the world. According to Leibniz, this evil merely seems to tell against God's goodness. We know that God is a perfect being, and we know that a perfect being may act only in the best way. Consequently, the fact that God created this world reveals that it is the best of all possible worlds. The appearances that seem to tell against this are merely appearances, and we may therefore have confidence in the goodness and intelligibility of this world.

The Destiny of Rationalism

Kant's Critique of Pure Reason definitively limited the rationalists' pretensions to achieve knowledge of substantive truths by means of the intellect alone. Kant argues that knowledge is limited to the appearances presented to us by the senses; no extension of knowledge is possible to the "supersensible" or intelligible realm to which the rationalists, like Plato, purported to have access. Consequently, the rationalist belief in the capacity of the pure intellect to achieve knowledge of truths about the universe is revealed to be unfounded. Indeed, Kant's critique revealed that the rationalist commitment to pure intellect that can operate independently of the senses was untenable. Moreover, recent developments in science further reveal that the rationalist conception of the world as an intelligible order was overstated. Nevertheless, the rationalist commitment to the power of reason remained alive for Kant, particularly in his practical philosophy. Rationalism encouraged women to use their own reason in philosophy: Princess Elizabeth of Bohemia and Damaris Masham directly engaged Descartes and Leibniz, respectively, in correspondence; Margaret Cavendish and Anne Conway worked out a rationalist paradigm. Finally, from a historical standpoint most significantly, rationalism inspired Enlightenment thinkers to trust in human abilities without reliance on divine illumination.

See also Empiricism ; Epistemology ; Metaphysics .

bibliography

PRIMARY SOURCES

Descartes, René. The Philosophical Writings of Descartes. 3 vols. Edited and translated by John Cottingham, Dugald Murdoch, Robert Stoothoff, and Anthony Kenny. Cambridge, U.K., and New York: Cambridge University Press, 1984–1991. Most complete English edition of Descartes's writings.

Kant, Immanuel. Critique of Pure Reason. Translated by Norman Kemp Smith. New York: St. Martin's, 1965. Classic, beautiful translation.

Leibniz, G. W. Philosophical Essays. Edited and translated by Roger Ariew and Daniel Garber. Indianapolis: Hackett, 1989. Good selection of Leibniz's writings, spanning his entire philosophical career.

——. Theodicy: Essays on the Goodness of God, the Freedom of Man, and the Origin of Evil. Edited by Austin Farrer. Translated by E. M. Huggard. La Salle, Ill.: Open Court, 1985. The most readily available English translation.

Malebranche, Nicolás. The Search after Truth. Edited and translated by Thomas Lennon and Robert Olscamp. Cambridge, U.K., and New York: Cambridge University Press, 1997. The most recent English translation.

——. Treatise on Nature and on Grace. Edited and translated by Patrick Riley. Oxford and New York: Oxford University Press, 1992. Fine edition; omits two of the Elucidations added by Malebranche.

Spinoza, Benedict de. The Collected Works of Spinoza, Vol. I. Edited and translated by Edwin Curley. Princeton, N.J.: Princeton University Press, 1985. Magisterial edition of Spinoza's early writings. Volume II is in preparation.

——. Theological-Political Treatise. 2nd ed. Translated by Samuel Shirley. Indianapolis: Hackett, 2001. Best available English edition.

SECONDARY SOURCES

Garrett, Don. The Cambridge Companion to Spinoza. Cambridge, U.K.: Cambridge University Press, 1989. Essays cover most aspects of Spinoza's work.

Hatfield, Gary. "The Cognitive Faculties." In The Cambridge History of Seventeenth-Century Philosophy, edited by Daniel Garber and Michael Ayers. Cambridge, U.K.: Cambridge University Press, 1998. Seminal article; treats both rationalists and empiricists from the standpoint of the cognitive faculties.

——. Routledge Philosophy Guidebook to Descartes and the Meditations. London: Routledge, 2002. Sustained interpretation of the Meditations as cognitive exercises; also considers alternative interpretations.

Nadler, Steven. The Cambridge Companion to Malebranche. Cambridge, U.K., and New York: Cambridge University Press, 2000. Essays cover most aspects of Malebranche's philosophical writings.

Rutherford, Donald. Leibniz and the Rational Order of Nature. Cambridge, U.K., and New York: Cambridge University Press, 1995. General interpretation of Leibniz's philosophy as motivated by the attempt to reveal the intelligible order of the universe.

Sean Greenberg