What Cartesian Ideas Are Not

WHAT CARTESIAN IDEAS ARE NOT MICHAEL J. COSTA IT IS CLEAR that Descartes uses the term "idea" in a number of different senses. One recent commentator, Anthony Kenny, claims that Descartes's failure to identify clearly these different senses is not only confusing to the reader, it is also a major source of confusion in Descartes's thought. Failure to keep track of" the ambiguity leads Descartes into inconsistencies and vitiates some of his arguments.' There is some justification for Kenny's position. One certainly wishes that Descartes had kept better track of his uses of the term "idea," and it may be that his failure to do so is an occasional course of equivocation. Still, I think that Kenny distorts the nature of the ambiguity in Descartes's use of "idea." Kenny virtually ignores a sense of "idea" that, as I shall show, is very important to a proper understanding of Descartes's thought; and Kenny reads a sense of "idea," in which it denotes an immaterial image or phenomenal object, that I claim is not present in Descartes's thought. The sense of "idea" that Kenny virtually ignores is that in which it is used to denote what Descartes often calls an "image in the corporeal imagination ." This "image" is corporeal not only in the sense that it is an image of an extended object, but also in the sense that the image is itself corporeal and extended. The image is made up of material particles in a certain arrangement . In modern parlance, what Descartes refers to as an "image in the corporeal imagination" is a brain state. "~ ' Anthony Kenny, "Descartes on Ideas," in Willis Doney (ed.), Descartes (New York: Anchor Books, 1967), pp. 927-49. Other commentators put more emphasis on Descartes's corporeal images. See, e.g., Jonathan R~e, Descartes (London: Allen Lane, 1974), ch. 5. Bernard Williams, in his Descartes: The Project of Pure Enquiry (Sussex, England: Harvester Press, 1978), giveslittle attention to Descartes 's corporeal images; but his viewof Descartes's other senses of "idea" seems to support my claim that Descartes does not have immaterial images. For example, Williams claims in several places (pp. 13o, 94o, 285) that Descartes's ideas do not represent the world by resembling it. [537] 538 JOURNAL OF THE HISTORY OF PHILOSOPHY 21:4 OCT 1983 This sense of "idea" is most clearly present in Descartes's physiological work, the Treatise of Man. 3 After describing how the rest of the body functions , Descartes attacks the question of how perceptions are registered by the brain. He introduces the subject in this way: But before I speak to you in greater detail concerning sleep and dreams, I would have yon first consider whatever is most noticeable about the brain during the time of waking: namely, how ideas of objects are formed in the place destined for imagination and for common sense, how these ideas are preserved by memory, and how they cause the movement of all the members. (TM, 83; AT XI, 174; original emphasis) The story that we get in the next few pages is entirely mechanical. External objects have certain physical effects on the sense organs. For example, in the case of sight, an image of the external object is formed on the retina of the eye. The effects on the sense organs bring about certain effects on the nerves. The nerves, which are viewed as filaments or narrow tubes, are tightened or loosened in a pattern that corresponds to (bears an isomorphism to) the pattern of effects in the sense organ. The tightening or loosening of the nerves in turn brings about a certain corresponding pattern of openings in the ends of the nerve filaments in the brain. The animal spirits, which are entirely composed of tiny material particles, flow from the pineal gland into the openings of the nerve filaments. The animal spirits take the path of least resistance, so the pattern of the animal spirits flowing from the gland corresponds to the pattern of openings in the nerve filaments. This traces the "figure" of the external object in the flow of the spirits on the surface of the pineal gland (TM, 83-7...