Descartes, René

A dominant figure of mid-seventeenth century philosophy and science, René Descartes (1596-1650) developed a sweepingly anti-Aristotelian, mechanist theory of nature, while also advocating a conception of the "rational soul" as a distinct, immaterial entity, endowed by God with certain innate intellectual concepts. Generations of anglophone philosophers have tended (with some notable exceptions) to construe Descartes's importance as deriving mainly from his radical development of problems of scepticism, and his sharp dualistic distinction between mind and body, in his central philosophical work, the Meditations on First Philosophy (1641). Today, however, this conception is often criticized as historically naive. On one hand, the Meditations themselves were intended by Descartes to provide a "foundation" for his comprehensive mechanistic account of natural phenomena; the doctrines and arguments of the work need to be interpreted in this light. On the other hand, Descartes's vision of a comprehensive, unified theory of nature, grounded in a small number of "distinctly conceivable," quantitatively expressible concepts (especially size, figure and motion) was in itself of incalculable significance in the history of Western thought (cf. UNITY OF SCIENCE).

Prominent among Descartes's aims as a systematic scientist was the incorporation of biological phenomena (such as nutrition and growth), and many psychological phenomena as well (such as reflex behaviors and some kinds of learning), in the universal mechanistic physics that he envisaged. Works in which he develops mechanist approaches to physiology and psychology include the early Treatise on Man (published only after his death); the Dioptrics (published, together with the Geometry and Meteors, with the wide-ranging, partly autobiographical work, Discourse on the Method of Rightly Conducting One's Reason and Seeking Truth in the Sciences, 1637); parts of the compendious Principles of Philosophy (1644); and the late Passions of the Soul (1649).

Basic to Descartes's approach to the understanding of animal (including human) behavior is the notion that one should push mechanistic-materialist explanations as far as one can. From early in his career he proclaimed that all the behavior of nonhuman animals ("brutes") can be explained in mechanistic terms. In the Discourse on the Method (Part V) he defended this position by arguing that the behavior of brutes uniformly fails two tests that he considers to be crucial to establishing the presence of some principle other than the strictly mechanistic. The first is the ability to respond adaptively to a variety of challenging circumstances in appropriate ways. A bird, for instance, might seem to show more "skills" in building a nest that we can summon; but so does a clock show more "skill" than we command in measuring time. Yet neither the bird nor the clock is able to respond to novel circumstances in the inventive way characteristic of humans. Descartes's other, more famous, test for the presence of a nonmechanistic principle is the ability to use language: to "express our thoughts to others," no matter what may be said in our presence. He acknowledges that brutes can utter cries and grunts that have some kind of communicative effect, but he stresses that these fall short, drastically, of the range and versatility of human language. In the case of human beings, however, behavioral adaptability and "true language" demonstrate the presence of a nonmechanistic principle, a conscious rational soul.

Descartes's Discourse conception of nonhuman animals as "automata, or self-moving machines" is today sometimes characterized as "mechanomorphism." Widely rejected and even ridiculed in his lifetime, it remains a target, or stalking horse, for contemporary advocates of animal intelligence, consciousness, and (in some species) perhaps language (cf. COGNITIVE ETHOLOGY, PRIMATE LANGUAGE).

In the Meditations (as anticipated by Part IV of the Discourse) Descartes approaches issues of reason and consciousness from a first-person rather than a behavioral perspective. He argues, first, that all his apparent perceptions of a physical world are initially subject to doubt (in that they could in principle occur even if no physical world existed). In fact, he is able to find reason to doubt even the simplest and most evident propositions. But second, even in the face of such skepticism his own existence as a "thinking thing" at least is indubitable. Later he argues that he is the creature of a perfect God; hence his clearest and most distinct "perceptions" (mainly the deliverances of pure intellect) are beyond doubt. Finally he concludes that as a thinking thing, he is a substance distinct from any body, though (as he goes on to say) one at present closely joined with a body, with which he, as a mind, interacts (cf. SELF and MIND-BODY PROBLEM). He further maintains that, given the goodness of God, his normal conviction that his seeming perceptions of bodies are in fact caused by external physical things must be correct.

Along the way, however, Descartes repeatedly underscores the point that bodies are not in fact as they appear in ordinary sense experience. For instance, their appearances as colored are misleading, in that we tend to suppose that (say) green as we sensibly experience it is a real quality of some bodies; whereas in fact it is just a sensation in our minds, resulting from the effect of external things (constituted of bits of matter in motion) on our nervous systems, and of the latter on us as immaterial mental substances.

In the Meditations Descartes characterizes both sensations and our intellectual apprehensions (such as our representation of God) as ideas. The Cartesian theory of ideas had great impact on subsequent philosophy. It involves complex notions about representation and misrepresentation that continue to attract the interest of philosophers and scholars today (cf. MENTAL REPRESENTATION).

There is substantial -- probably conclusive -- evidence in Descartes's post-Meditations writings that he intended to limit strictly mental phenomena to those states that are accessible to an individual's conscious awareness. But this austere aspect of his mind-body dualism sits uneasily with some features of his impressive accounts of human visual perception in the first half of the Dioptrics; and of human emotions in the Passions of the Soul. In both works he not only blends sensational with intellectual states in his explanations of mental phenomena, but also invokes considerations that are hard to apportion between the "conscious-mental" and "purely mechanistic-material" divide. This is particularly true of his account of distance perception in the Dioptrics, in which Descartes certainly seems to invoke a kind of COMPUTATION that cannot plausibly be regarded as accessible to consciousness (cf. COMPUTATIONAL VISION).

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-- Margaret D. Wilson

Descartes, René

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