Descartes May Not Be What We Have Been Told

Although it is often misunderstood today, Descartes’ greatest contribution to modern science was his realization that “the path to progress lies in what is mathematical and mechanical.” Aristotle and his disciples attributed the functions of living beings—such as nutrition, sensation, and movement—to the soul. Yet for Descartes, there was a qualitative difference between the functioning of living and non-living things, and therefore no soul was necessary for life. In his view, even human activities—including biological ones—operated just like a self-moving machine, like a clock or a mill. For this reason, the fire found in inanimate objects was the same as the fire in the body; there was no need to invoke an additional principle of life to explain it.

Descartes’ Defense of the Soul by Narrowing Its Scope

In his book In Search of the Soul, John Cottingham, in addition to these findings, also cites the list of human functions that Descartes proposed could be explained without requiring the soul, as presented in his Treatise on Man. The list reads: “the digestion of food, the beating of the heart and arteries, the nourishment and growth of the limbs, respiration, waking and sleeping, the reception of light, sounds, smells, tastes, heat, and other similar qualities by the external sense organs, the imprinting of ideas corresponding to these qualities onto the organ of ‘common sense’ and imagination, the retention or stamping of these ideas in memory, the internal movements of appetite and passions, and finally, the external movements of all the limbs that appropriately follow both the actions and objects presented to the senses and the passions and impressions held in memory.”

This list is, in fact, quite surprising to those who debate Descartes without knowing him well: not only the functions of the autonomic nervous system but also psychological functions such as sensory perception and memory require no soul; there is virtually no work left for it. A mechanical explanation suffices for all of these—until we come to those tasks that require the attention of the “conscious mind.” Conscious mental attention—that is, intentional focus—resists mechanical explanation, and for that, a “rational soul” becomes necessary.

It is precisely this “conscious mental attention” that distinguishes the human being not only from mechanical automatons but also from other living beings. Descartes argues that a mechanical automaton can never speak, whereas animals can be trained to mimic speech. Yet the sounds that animals produce are merely responses to external stimuli that cause changes in their nervous systems. In Discourse on the Method, he writes: “We can certainly imagine a machine constructed to utter words corresponding to changes in its organs… But it is unimaginable that such a machine could arrange words in such a way as to provide a meaningful response appropriate to everything said in its presence; yet even the most foolish human being can do this.”

Cottingham holds that Descartes saw the distinctive feature of human language as “the capacity to respond appropriately to an open-ended range of situations.” This, he suggests, is a capacity that generally appears to be fundamentally different from anything that a finite system—one that produces a series of outputs from a series of inputs—could generate. According to Descartes, no purely physical system can possess the resources to produce the kind of genuine creativity and innovation that human linguistic behavior demonstrates (pp. 70–74). In Discourse on the Method, Descartes writes: “While the bodily organs require a specific arrangement for each particular action, the mind is a tool that can be used in any situation. It is morally impossible—that is, impossible for all practical purposes—for a machine to do this, because it cannot possess enough distinct organs to allow it to act the way our mind moves us in all the contingencies of life” (quoted by Cottingham). In the end, he is compelled to assume that the hidden schematism responsible for thought must be an immaterial soul (pp. 74–75).

Following today’s immense advances in physics and neuroscience, how valid is Descartes’ conception of matter as intrinsically tied to geometric space? And does stating that thought—or the soul—is immaterial explain how the functions attributed to it actually occur? Certainly not. That is likely why, quite naturally, there exists today a very strong belief in the scientific community that thought—or cognition—arises from the electrical and chemical activity of the cerebral cortex. Undoubtedly, this is a belief—as the word implies—and it remains unproven. But it is also a fact that only the human brain is capable of producing language and thought. So even if Descartes was wrong in claiming that a non-material substance outside the body is needed, his insistence that “the activities he chose to attribute to the soul are irreducible properties of our human nature”—that is, that thought cannot be explained by or reduced to material facts and events alone—remains valid today. What Descartes manages to alert us to, in a striking way, is that a vital part of being human necessarily transcends the quantitative and mechanical categories of scientific explanation (pp. 77–78).

To put it briefly: if he could, Descartes would have explained all sensory experiences through the body; he never intended to ascribe them directly to an immaterial soul. And yet, no matter what we do, according to him, there is more to the human being than a bodily machine animated by a non-physical, immaterial soul. And this excess is by no means the same as the Pythagorean-Platonic form of “angelism”—that is, a position that reduces humans and their bodies to purely spiritual entities separate from the body, which they merely use as they please.

Undoubtedly, Descartes initially thinks within a dualist framework: he assigns separate functions to the body and the mind and treats matter and spirit as two irreducible substances. Yet in his correspondence with the Princess of Bohemia, he makes it abundantly clear that his account of human nature cannot be reduced to a simple dualism, but instead calls for a tripartite distinction: the concept of the soul (which includes reason and will), the concept of the body (defined in terms of form and motion), and the union of the two (on which sensation depends) (pp. 82–83). From this, Cottingham argues that Descartes—or rather, the Cartesian model—was not truly a dualist who believed in two substances, but a trialist, one who proposed a threefold structure that offers a much richer and more refined view of the human condition.

The Soul Makes Me Who I Am!

According to Descartes, the human being is not an incorporeal soul attached to a bodily machine, but a mental being intimately intertwined with the body. From his book Passions of the Soul, we understand that he did not view the human being as a wholly immaterial spirit, but rather as an embodied creature—flesh and bone—adorned with sensations and emotions, and thus inevitably burdened with moral responsibilities. We also come to realize that our body is not merely an instrument or a hanger for our soul, but something that, in a private and intimate sense, is “mine,” is “myself.” This view of the body illuminates what Descartes meant when he spoke of “this me (ce moi), that is, the soul that makes me me,” and how he approached this immaterial substance.

I—this me, that is, the soul that makes me me—am not an object or element that can be measured by the quantitative methods of science. I am a subject; I am, so to speak, the possessor of the thoughts, feelings, and experiences that constitute my conscious life (p. 92). Surely, one might say that some mammals have a sense of self to a greater or lesser extent—but we can also affirm that they can never possess “the soul that makes me me.”

“Descartes may have been mistaken about the limits of physical brains and matter in general. But what he did not mistake,” writes Cottingham, “was the irreducible reality of conscious thought and of the rich, conceptually mediated world of lived experience that each of us can access as subjects of conscious awareness” (p. 102).

In exploring the philosophical search for the soul, we have taken John Cottingham’s work as our guide, starting from his idea that the soul and the self are virtually identical. One of the main reasons for choosing Cottingham as our reference was his perspective: he not only understood and respected scientific inquiry but also believed that modern scientific knowledge does not exhaust what it means to be human. He was a theist (not a deist, but a theist who also believed in the necessity of religion), who valued not only science but also the forms of knowledge that emerge through art, poetry, and theology.

According to him, not only the self, but also consciousness and free will have nearly the same meaning—or rather the same scope—as the “soul.” With such a conception in mind, he could easily shift from one term to another, grounding his view in Descartes’ perspective—a view that paved the way for modern science while avoiding flighty and speculative notions of “spirit.” When the term “soul” is used, it draws attention to the following fact: human beings are the individual reflective subjects of conscious experience. Each of us is aware of ourselves “from within,” as the “me that makes me me.” And it is precisely because we are such self-aware subjects that we find ourselves at the center of a “lifeworld” and gain access to a rich field of meaning and value. For this reason, finding the soul is not merely a subjective exercise in introspection and self-examination; it is, in part, an outward-looking endeavor—an effort to understand our relationship with the objective reality that confronts us and awaits our response (pp. 127–128).

Cottingham aligns himself with Descartes not only in his deeply worldly view of the soul, but also in the path that leads from this view to a belief in God. Just like Descartes in Meditations, he believes that the true teachings of nature come from Nature itself. By “Nature,” he means “nothing other than God himself, or the order and mechanism established by God in created things… or, when it comes to my own nature, I mean the totality of what God has bestowed upon me” (pp. 171–172). For them, God’s presence reveals itself within the natural world. The human spirit is easily identified with the “divine spark” (p. 186).

“We may never escape the bonds of our physical nature—nor perhaps should we wish to—for our embodiment grants us our humanity; and though we are weak and mortal, it bestows upon us the immeasurable riches of conscious experience. But when we reach the transcendent, then the soul ‘rises enchanted.’ And to the extent that our finite and imperfect nature allows, ‘we rise with a silently soaring mind and touch God’s face’” (p. 192).

We shall return to Descartes and the insights that his perspective might offer for the present. But first, we want to address the current situation—and the critiques of Descartes—regarding the mind (soul) and body (brain) problem.