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René Descartes was a brilliant mathematician. He was also a dedicated metaphysician and is considered the father of modern philosophy. Though a fraction of the length, his Meditations on First Philosophy rival Immanuel Kant’s Critique of Pure Reason as a precedent-setting work in Western philosophy. My talk today will focus on Descartes divisive legacy: the downside of his metaphysics or more specifically, his distinction between mind and body, a distinction that has had huge negative consequences regarding how people think of their essential nature.

There have been a number of intellectually pivotal figures in the history of philosophy, beginning with Socrates (469-399 BCE) and going on to Plato (429?-347), Aristotle (384-322 BCE), Thomas Aquinas (1225-1274), Rene Descartes (1596-1650), and Immanuel Kant (1724-1804). In our own Anglo-American epistemology or theory-of knowledge oriented philosophical tradition, names that come readily to mind are Bertrand Russell (1872-1970), Ludwig Wittgenstein (1889-1951), and W. V. O. Quine (1908-2000). In the metaphysically oriented Continental tradition, one thinks of Friedrich Nietzsche (1844-1900), G. W. F. Hegel (1770-1831), and Martin Heidegger (1889-1976). But however influential these thinkers were, their ideas influenced relatively limited numbers of people, largely academics. The ideas of a few of these philosophers, for instance those of Aquinas and Nietzsche, were woven into religious and political ideologies and affected many people beyond the academy, but not without distortion and embellishment. Descartes was an exception. His most basic philosophical contribution, the drawing of a fundamental metaphysical difference, gave philosophically authoritative formulation and apparent legitimacy to an idea shared by literally billions of people who, for mainly religious reasons, think of themselves as minds or souls temporarily ensconced in often depreciated physical bodies.

The distinction between the mental and the physical is much older than Descartes, but with the exception of Plato, no Western philosopher prior to Descartes drew the distinction as categorically as he did. For instance, Aristotle distinguished between our physical bodies and what he described as our ‘active’ and ‘passive’ intellects. But while distinct and separate from the body, the active intellect was a communal and essentially impersonal life-force that animated individual bodies. It was the passive intellect that made each of us who we are by holding our awareness and memories, and for Aristotle the passive intellect was inherent to the body and did not survive the body’s death. Aquinas distinguished between the body and the immortal soul, but he subscribed to the doctrine of resurrection, of the eventual revitalization of individuals’ physical bodies, and he deemed resurrection of the body necessary to make whole surviving but essentially incomplete souls.

Contrary to Aristotle and Aquinas’ view of us as physical beings enhanced with mentality or consciousness, Descartes saw us as intrinsically mental, as wholly mental or spiritual entities ensconced in physical or what he deemed ‘extended’ bodies—i.e., bodies having dimensions in space. He saw the mental as exhaustive of our nature, not as precious augmentation of some physical bodies.

Just how did Descartes totally divide the mind and the body? To begin with, in his Meditations on First Philosophy (available to some in 1640 but published in 1641, in Latin and later in French) his primary philosophical objective was to establish what can be known as true with absolute certainty and so to offer a method for acquiring indubitable knowledge. Descartes’ mathematical savvy and successes clearly moved him to find what, if anything, outside mathematics could be known with the same degree of certainty as is available within mathematics. The approach he used to achieve this goal was to engage in what commentators call ‘methodological doubt,’ the doubting of everything, of every thought and sensation he had, every belief he held. To support his doubting Descartes even invented a ‘malevolent deceiver,’ a god-like demon intent on deceiving him about everything in his consciousness. The objective of methodological doubt was to discover and isolate intuitively clear thoughts or ideas that once comprehended cannot be doubted because of their evident and unquestionable truth.

Having applied methodological doubt in the first Meditation, Descartes hit upon the most fundamental and undoubtable truth in the second Meditation: the realization that if he thinks, he must exist. This realization, a preliminary form of which Descartes used in his earlier Discourse on Method but later abandoned, is invariably quoted in that earlier form as the famous cogito: “Cogito, ergo sum” or “I think, therefore I am,” and just as invariably is associated with the Meditations. This is the mistake referred to in the blurb advertising this talk. In his 1637 Discourse on Method, Descartes stated the cogito, in French, as “Je pense donc je suis,” or “Cogito, ergo sum” in Latin. The cogito, including the ‘therefore’ and hence as an argument, would have to run something like: “All things that think, exist; I think; therefore I exist,” thus requiring the suppressed premise: ‘All things that think, exist.’ By 1640 and 1641, the time of the Meditations, Descartes understood that the cogito could not be an argument because the suppressed premise could be challenged or doubted. The cogito was and had to be a direct intuition, so he dropped the ‘therefore.’1

However, as indicated, despite Descartes coming to understand that ‘ergo’ made the cogito an argument requiring a suppressed premise, his acknowledging that the cogito is not an argument but a direct intuition, and the ‘ergo’ formulation not occurring in the Meditations, people insist on including the ‘ergo’ or ‘therefore’ quoting or referring to the cogito. Contrary to this, the cogito is properly stated in the second Meditation as “Ego sum, ego existo” or “‘I am, I exist,’ is necessarily true whenever…it is conceived in my mind.”2

In any case, in the second Meditation Descartes finds the indubitable truth he sought and needed to proceed. If his Meditations project had succeeded as intended,Descartes would have provided us with proof of God's existence and a procedure for acquiring unquestionable knowledge. As it worked out, what Descartes accomplished was to restate a traditional argument for the existence of God, more or less invent another, and establish a false understanding of our nature.

The argument for God’s existence that Descartes restated, in the fifth Meditation, is Anselm’s Ontological argument. Both versions are purely conceptual and appeal to reason alone, basically being the contention that to understand the concept of God as perfect is thereby to understand that God must exist. The argument for God’s existence that Descartes more or less invented is presented in the third Meditation and is a causal argument, mainly being that the idea of a perfect God, as an effect, must have a cause adequate to the idea, and that could only be a perfect God. But these arguments are not our present concern. What concerns us is the articulation of the exceptional single truth that neither methodological doubt nor the malevolent deceiver could impugn, which is that it follows necessarily from the fact that Descartes is thinking that he exists.

Recognizing that if he is thinking, if he is doubting what he believes, he must exist while doing so, in the second Meditation Descartes asks himself what he is, what it is that exists as he thinks and doubts. The answer he gives, in the original Latin, is that he is a res cogitans: a thing that thinks. John Cottingham, in his authoritative translation of the Meditations, translates Descartes’ question and answer as: “But what then am I? A thing that thinks.”3

But the term ‘res’ or ‘thing’ is a wholly neutral reference to an existent. By ‘a thing that thinks’ Descartes does not mean a physical thing, a body that thinks; it is a pure mind or soul that thinks. Descartes used ‘mind’ and ‘soul’ indiscriminately, telling us: “I do not distinguish between them.” But whether referred to 4 as a mind or a soul, the res cogitans, the thing that thinks, is “in the strict sense…a mind, or intelligence, or intellect.”5 The thing that thinks “is not extended in length, breadth or height and has no other bodily characteristics.” Descartes insists that “absolutely 6 nothing else belongs to my nature or essence except that I am a thinking thing.”7

Not even the most intense feeling or sensation prompts Descartes to add anything sensory to his essence or nature. Appreciating this is crucial to understanding the source of Descartes’ divisive legacy: his alienation of our bodies from our supposed essential natures. The core of the problem is that the most vivid image, the most resounding noise, the sharpest pain is simply another thought, another idea. As such, sensory content does not require anything beyond thought or thinking, hence no complication of the purely mental nature of the thing that thinks. Nothing sensory affects the nature of the mind or soul because nothing sensory is or can be a direct object of awareness. Sensations or feelings are just so many more ideas or thoughts supposedly having external causes, causes that may or may not exist as presented. This is why Descartes tells us in the Dioptrics that “[i]t is the soul which senses, and not the body.”8

Now, Descartes understood as much about our brains and nervous systems as any of his contemporaries, but for him, our nervous systems and brains had nothing to do with consciousness. What they did was convey data to some point where it became accessible to the mind or soul, and it is the mind or soul that is conscious, not the body. The point of connection was supposedly the pineal gland, no doubt selected as where sensory data becomes available to the mind because at the time no one had a clue as to what the gland does.

To indicate the extent of Descartes’ alienation of the body, I will mention one bizarre consequence of the favorable reception of the Meditations by European intellectuals– a reception that was favorable despite Descartes’ dubious status in the eyes of the Church in France and to a point in Holland, where he spent much of his adult life. The bizarre consequence was that it became fashionable among some of the intelligentsia to torture animals in order to display their understanding of Descartes conception of the mind and awareness. Since it is the mind or soul that senses, and animals lack souls or minds, therefore they cannot feel pain—or anything else. Animals are pure automata. Their behavior is wholly reflexive, not prompted by any measure of conscious awareness because, as Descartes insisted, animals “have absolutely no cognition.” In fact, he lamented that “[t]he greatest 9 of all the prejudices which we have retained from our childhood is that of believing that the beasts think.”10

What the foregoing underscores is that, for Descartes, our bodies are on a par with animals: they are physical or extended entities, automata incapable of consciousness or awareness. Descartes’ conception of the mind or soul as a res cogitans, as a thing that thinks, renders our bodies extraneous to our nature. He declared in the Discourse on Method that the mind or soul “is of a nature which is entirely independent of the body.” In a letter to Reneri in 1638, Descartes stressed that “[f]rom 11 the fact alone that one conceives clearly and distinctly the two natures of the soul and the body as diverse, one knows that truly they are diverse.”12 We are, then, minds or souls riding around in flesh-and-blood conveyances that in no way are part of what we are.

This complete division of mind and body—and no doubt the implausibility of the pineal gland connection—led some post-Cartesians to postulate a view that seems absurd outside of the relevant philosophical context. The view was ‘Occasionalism,’ and amounted to the astonishing notion that there are two totally independent series of events, one mental, one physical, and that God, Who created both, coordinated them to correspond as if there were interaction between them.13 In any case, the body is only known at one remove, and since it cannot be known directly, as the mind knows itself in the act of thinking, the body is in fact essentially postulated as existing as the source of the sensory ideas the mind receives. It is difficult to imagine a more exhaustive and absolute separation of our minds and our bodies, and this is the core of Descartes’ divisive legacy.

To conclude, Descartes’ legacy is divisive in two ways. First, his categorical distinction between mind and body made us minds in bodies when we are in fact bodies that think. By drawing his metaphysical distinction as he did, Descartes made our mentality the whole of us, not an attribute of bodies with neurologically complex nervous systems, and thereby divided us in kind from the physical world. Second, by splitting apart minds and bodies in an unqualified way, Descartes not only misrepresented our nature, he invited a socio-religious split between people who understand us to be physical beings endowed with mentality, and people who believe we are mental entities temporarily animating extrinsic and eventually discardable physical bodies.

I believe that the most worrying result of Descartes’ misconceived alienation of the body is that he provides philosophical grounds, and thereby apparent intellectual legitimacy, for those who wrongly think of themselves as mental or spiritual beings only incidentally and temporarily possessed of physical bodies. This supposedly well grounded and legitimate way of thinking is socio-politically dangerous because it invites and prompts potentially hazardous aggrandizement of the mental or spiritual and devaluation of our physical being. History is replete with examples of the worst instance of this is wrongful willingness to take or surrender life in the mistaken belief that death is only termination of temporary and dispensable embodiment.

Matson, Wallace, A New History of Philosophy, 2nd edition, 2000, New York: Harcourt Brace, Vol. 2, p. 321.
Descartes, Rene, 2013, (1641), Meditations of First Philosophy, John Cottingham, trans., Latin-English edition, Cambridge: Cambridge University Press, p. 34; 1986 (1641), English edition, p. 17.
Descartes 1986 (1641), p. 19.
Descartes 1986 (1641), p. 10, Note 3, added in French version.
Descartes 1986 (1641), pp. 17, 18. “Only” occurs in both the original Latin and the French versions, but Descartes told Gassendi he meant ‘in the strict sense.’ See Note 1, ibid.
Descartes 1986 (1641), p. 37.
Descartes 1986 (1641), p. 54.
Dioptrics, IV, VI, 109.
Rules, XII. X, 415.
Letter to More, Feb. 5, 1649. V, 276.
Discourse on Method, V. VI, 109.
Letter to Reneri, Apr.-May, 1638. II, 38.
Matson 2000, p. 331.
(C) C.G. Prado. Reprinted with permission.