Descartes' Natural Light

Descartes' Natural Light JOHN MORRIS RENI~ DESCARTESBEGINSHIS MnDrrATmNS with the attempt to doubt all his former opinions--the existence of external objects, the existence of his own body, and what he sometimes calls the "eternal truths" of arithmetic and geometry. He can even suppose that God is a fable, and that the world is in the hands of an evil genius, who spends all his time deceiving Descartes. But there is, Descartes triumphantly announces, something about which he cannot be deceived: his own existence. The proposition 1 am, 1 exist is necessarily true, each time that I pronounce it, or that I conceive it in my mind. Before long, though, something strange has happened. Certain propositions have eluded the process of universal doubt, and they are said to be "manifest by the natural light." These propositions, which Descartes elsewhere calls "'axioms," "first principles," or "common notions," are absolutely essential in the proofs of the existence of God, and without God the whole Cartesian system would collapse. The natural light, whatever it is, thus plays a critically important role in Descartes' theory of knowledge. Until quite recently, however, the natural light has received very little attention from writers on Descartes. Even Anthony Kenny, in his discussion of what he calls the "principles of natural light" (putting the phrase in quotation marks, although it never appears in any of Descartes' writings), does not attempt to track down the precise meaning of this curious expression. 1 Kenny has, however, rescued the natural light from the mushy bog in which Norman Kemp Smith left it, in which "natural light," "reason," "intuition," the "power of knowing," "understanding," "cognitive awareness" (Kemp Smith's expression) and goodness knows what else are all lumped together as a single faculty of the mind. 2 It is absolutely essential, if we are to understand Descartes at all, to reject Kemp Smith's attempt to identify all these terms with one another; instead, we must track down the meaning of each of them, see how their meanings differ, and avoid any effort to show that they are simply different names for the same mental entity. Although Gilson's Index Scolastico-Cartdsien lists some sixty page references to the lumen naturale in Descartes' writings, most of them appear in or after the x Anthony Kenny, Descartes: A Study o] His Philosophy (New York: Random House, 1968), p. 20. Norman Kemp Smith, New Studies in the Philosophy o] Descartes: Descartes as Pioneer (New York: St. Martin's Press, 1952),pp. 73-74. [169] 170 HISTORY OF PHILOSOPHY Third Meditation, and it is here that the term plays its crucial role, validating or justifying the axioms which are used in the proofs of the existence and veracity of God. 3 As Kemp Smith pointed out, the term "natural light" was in general use during the seventeenth century, but the reference which he gives--to a passage in Blaise Pascal--is not especially helpful, inasmuch as Pascal wrote it a dozen years after Descartes was dead, and the meaning that he gives the term has no clear relationship to that of Descartes. 4 A more likely source, as Gilson has shown, is the work of St. Thomas Aquinas, for whom the natural light plays a central role in his Aristotelian theory of knowledge. For Aquinas, "natural reason" depends upon two processes: "The knowledge which we have by natural reason requires two things: images derived from the sensible things, and a natural intelligible light enabling us to abstract intelligible conceptions from these. ''5 Accordingto this scheme, two processes take place in the formation of a concept or idea: first, the sensing of the object, by means of the physical senses; and second, the creation of the concept or idea of that object by means of a faculty which Aquinas elsewhere calls the "light of the agent intellect." 6 For the Scholastics, there is nothing in the intellect which has not previously been in the senses; physical sensation thus serves as the foundation for natural knowledge (in contrast with knowledge of the Divine, which has a radically different source). This Aristotelian empiricism was the antithesis of Descartes' rationalism, which ridiculed the claim that sensation was the basis...