Descartes--A Hasty Balance Sheet

Contact: Dr. Jan Garrett

Minor modification February 18, 2008

Although this reflects more than three decades of studying and teaching philosophy, it was hastily composed to be shared with students in a history of philosophy course in a single lecture. I have not yet had to time to reread it carefully and refine it. I would be especially happy to be corrected by someone better educated in the science material raised in what follows.


Descartes' philosophy seems to have been just the right philosophy at the time to bring the alliance between mathematics and the new science into intellectual respectability against the resistance of the then dominant alliance consisting of Scholastic and Aristotelian philosophy and Ptolemaic astronomy with the intellectual authorities in the Catholic Church.

The machine model of "body" (what will sometimes be called "nature") that Descartes helped to popularize was very useful in astronomy and mechanics at the time; it is still much in use today (when medical science thinks of doing hip replacements and transplants), but less central in physics and cosmology than it used to be. It is also of limited value in medical science.

More Negative Than Not

  • Prejudice against prejudice. (Note: Prejudice in this sense is a judgment in advance of full comprehension and evidence. A prejudice need not be false.)

    Following Francis Bacon, Descartes implicitly challenged an influential view that popular or culturally transmitted beliefs were the source of philosophical insight. One version, prominent in theology, was fides quaerens intellectum, "faith seeking understanding." But faith or prejudgment, as Bacon and Descartes knew, is not operative only on religious matters but in other areas of cognitive life.

    Descartes thought it possible and desirable to exclude it from philosophy and scientific research. (See his Discourse on Method.)

    But there is no research without some notion of what one is likely to find and what might count as a correct discovery. The machine model of body itself is a kind of faith or prejudice for Descartes and his physicist allies. True, some prejudgments may turn out to be false and unhelpful. True also, sometimes we have to abandon some of our prejudgments, but when we do we always rely upon other prejudgment (perhaps adopting new ones or emphasizing older ones that we held but had been in the background).

    One prejudice Descartes does not abandon is the Great Chain of Being (although he modifies it). The earlier version had been something like:

    Human Reason
    Faculty of Sensation
    Faculty of Nutrition
    Compound elements
    Basic Elements

    In this view, humans, animals, and plants correspond to the third through the fifth item in the list, in the sense that reason is the highest of the several factors found in humans, sensation is the highest of the several factors found in "beasts," etc.

    In his own version Descartes puts reason and sensitive experience into the (human) mind or soul. Reason in the older model roughly corresponds, in Descartes, to intellect, the faculty for grasping clear and distinct ideas, and sensitive experience roughly corresponds to obscure ideas. He regards the human body, "beasts," and plants as natural machines.

  • Mind body split

    Human bodies are machines, animals are machines. This leads to

    1) Misconceptions about animals and attributes we share with animals

    2) A denial of animal consciousness, animal emotions, that animals have purposes

    3) The alienation of humans from their own body, nonhuman life, and from the earth

    4) Even materialists, who officially deny the mind-body split, are often misled by post-Cartesian temptations to conceive of humans and animals as machines.

    Physics, however, has abandoned the Cartesian machine model; it doesn't fit well with the concept of fields (the field of a charged particle, etc.) and the other metaphorical concepts central to contemporary physics.

  • Mistaken, or at least misleading epistemology
    1) Knowing is solitary. Actually it's largely social. Descartes probably did not intend to slight the importance of the scientific community for scientific research. Still, his Meditations provide a striking and influential model of the solitary thinker/knower that is almost completely at odds with the social dimension of knowledge in his and later times.

    2) Knowing is disembodied; it takes place in the mind apart from body. Such is the impression we take away from a study of Descartes' Meditations. Actually, knowing or having warranted belief nontrivially depends upon laboratories, machines of all sorts, the bodies (and minds) of peer and subordinate researchers, and communication between them.

    3) If we have knowledge of beings outside our minds, we do so through ideas that re-present what they are about. D had a representative theory of ideas and knowledge. On this approach, our ideas are to be evaluated in terms of their ability to re-present the things of which they are ideas. Thus, the idea of a white cube appears as a representative of a white cube in the external world, but only the clear and distinct cube-idea adequately re-presents the cube in the external world; the idea of white does not because I cannot know that it re-presents what is in the external world. This becomes a problem for later epistemology. Some of the same skeptical methods Descartes uses to discredit ideas like that of color can be used to call into doubt ideas of geometrical properties.

    4) Imagination is not essential to our nature as thinking beings. Descartes fails to appreciate that imagination is not an accidental feature of our nature, but is essential to us as thinking beings. Use of metaphor and analogy (so-called imaginative devices) is not an ornament but essential to most of our thinking with concepts.


    Gadamer, Hans-Georg. Truth and Method. Continuum. Look up what Gadamer says about prejudice.

    Lakoff, George, and Mark Johnson. Metaphors We Live By, 1980. On the role of metaphor in thinking.

    Lakoff, George, and Mark Johnson. Philosophy in the Flesh, 1999. More on the role of metaphor and sensorimotor experience in thinking and on their role of metaphor in philosophical thinking.

    Longino, Helen. The Fate of Knowledge.

    Midgley, Mary. Myths We Live By.

    Schumacher, E. F. A Guide for the Perplexed.

    Note on Machine Model.

    Originally, I had the word "mechanism" here, which one reader thought was a reference to determinism. What I had chiefly in mind was something a bit different, a view of nature shaped by the conception of bodies as composed of solid three-dimensional geometrical parts. Descartes defines bodies as extended substances, by which he seems to mean entities able to occupy space such that other similarly defined entities are excluded from it. Most adherents of the early modern machine model also regarded nature as a deterministic system, but the two aspects seem conceptually distinct. It is the view that bodies are extended substances as Descartes understands them that directly excludes the possibility of physical "fields." For instance, the charge fields of two electrons and the gravitational fields of two planets may overlap.