René Descartes may just be the Thinking Man’s thinking man. More than any other modern philosopher, he is identified with the view that the soul is separate from the body and superior to it—in fact, we refer to this position as Cartesian dualism. The synonymy is so overwhelming, one can imagine him subjected to some hackneyed literary or television treatment wherein he is brought forcibly into the present, only to find success as an advertising executive with his slogan for the Winterman sneaker account that promises “mind over matter.” (For the women’s line: I pink therefore I am.)

Any dualistic theory encounters what is known in philosophy as the mind-body problem: how is it possible for two entirely discrete substances to act in concert and produce what we conceive of as unitary being? Curiously enough, Descartes’ lifelong passion for experimental physiology—which, for him, was just rationalistic epistemology by other means—influenced his answers. He was an avid practitioner of dissection on both human and animal bodies. (Because he believed animals were mindless machines and could not feel pain, he often dissected them while they remained alive.) In his search to discover the differences that distinguish humans and animals from one another as res intelligens and res extensa—that is, intelligent beings and “machines,” respectively—he hit upon the pineal gland, which he found present only in the human brain.

The pineal gland, located near the center of the brain, had been the subject of philosophical and scientific speculation since the days of Galen in Greek Antiquity. In most theories, it plays the part of a regulator, coordinating the flow of “spirits” (vaguely analogous to contemporary “nerves”) between different parts of the brain. Descartes came to the conclusion that pineal gland was the threshold over which pure mind and outward matter were connected. His observations as an anatomist were largely responsible for such a view. In response to questions arising from his 1639 Treatise of Man, he wrote:

“Since it is the only solid part in the whole brain which is single [microscopic research has proved this unity false], it must necessarily be the seat of the common sense, i.e., of thought, and consequently of the soul; for one cannot be separated from the other. The only alternative is to say that the soul is not joined immediately to any solid part of the body, but only to the animal spirits which are in its concavities, and which enter it and leave it continually like the water of river. That would certainly be thought too absurd” (24 December 1640, AT III:264, CSMK 162).

A decade later, in The Passions of the Soul, Descartes further elaborated on how the pineal gland worked:

“the activity of the soul consists entirely in the fact that simply by willing something it brings it about that the little gland to which it is closely joined moves in the manner required to produce the [bodily] effect corresponding to this volition” (AT XI:359, CSM I:343).

A unique hypothesis to be sure, but Descartes never satisfactorily explained, even in his own mind, just how the will caused the pineal gland to move in its particular fashion. His speculations about it were abandoned by his followers and detractors alike. In the 20th C, after several centuries of relative neglect, Yale scholar Aaron Lerner and his colleagues discovered that the pineal gland is the body’s major producer of melatonin, a hormone that is involved in sexual development, sleep rhythms, metabolic functions, and seasonal breeding in animals.

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“Remember how…beholding beauty with the eye of the mind, he will be enabled to bring forth, not images of beauty, but realities (for he has hold not of an image but of a reality)…”
-Plato, Symposium, 210

Thus Socrates—that is to say, Plato’s incarnation of Socrates—would have us believe that a stranger from Mantineia first clued him into the notion that beauty is in the eye of the beholder (many prefer Shakespeare’s rendering of the phrase). Although the preceding quotation appears in a passage concerning the good of friendship, one wonders what, if any, kind of aesthetic standards the philosopher attached to physical beauty.

Socrates was famously ugly—all that imperious, barbate statuary can be misleading—the extant sources are very clear in making a point of his brutish demeanor. He had bulging eyes, a snub nose, and fleshy lips “like an ass.” Nor was the philosopher in the business of improving upon the stamp of rude nature: He went about barefoot and unwashed, moving with a strange gait (so odd, it was said to intimidate enemy soldiers), and carrying a cudgel. He evidently never changed his clothes, using the same garments for his day-wear and pyjamas. Ever the gadfly, Socrates also let his hair grow long after the Spartan fashion, a look that couldn’t have amused the Athenian patriots of the day, still smarting from their defeat in The Peloponnesian War.

However, something must have endeared this smelly, unsightly, forbidding man of intellect to his fellows, or, at least, those of his fellows who did not force him to drink hemlock for “corrupting the youth of Athens.” Perhaps it was his inimitable way of bringing new perspective to old problems, often peppered with characteristic humor and irony. In Xenophon’s Symposium (V 1-10), Socrates compares his physical abnormality with Critobulus’ more pleasant aspect; by using use-value as his criterion for beauty, Socrates is able to prove himself the handsomer of the pair.

The stranger from Mantineia was in the right: In beauty, as in life, the nimble mind can outshine the fairest matter.

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Most eigteenth-century residents of Konigsburg, the hometown of Immanuel Kant, were unlikely to have read the great philosopher’s work. He wrote extremely dense treatises, particularly the three great “critiques”: The Critique of Pure Reason, The Critique of Practical Reason, and The Critique of Judgment. But while Kant’s work may have been impenetrable to most of his neighbors, they were very aware of the eccentric professor in their midst. It was said that Kant’s daily walk was so regular in its timing and route that residents of the town could adjust their timepieces when he walked past their windows.

There was one amusing instance, however, of Kant’s philosophy colliding with his habits. In his Groundwork of the Metaphysics of Morals, Kant, after a typically complex train of thought, concludes that every man has a duty to give charity so long as he can provide for himself. Konigburg’s panhandlers never read Kant’s metaphysical speculations, but they knew where the professor would be every afternoon, and they always waited there for the generous donations that Kant would make. Eventually, the old philosopher began feeling somewhat less charitable, and he changed his route.

Feeling brave? Read Kant’s Groundwork for the Metaphysics of Morals here.

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Social contract theory is most often associated with the great political philosophers of the Enlightenment: Thomas Hobbes, John Locke and, especially, Jean-Jacques Rousseau, whose major work was titled The Social Contract. But while the 17th and 18th-centuries were the hey-day of the theory, original work on “the social contract” is still being written in the 21st.

Perhaps the most prominent modern social contract theorist was the late Harvard professor John Rawls.* His most famous work is the 1971 book A Theory of Justice. In it, Rawls devised the famous thought experiment involving the “veil of ignorance.” Ask yourself, Rawls proposed, what you think the best political system would look like. Should there be “big government” or a decentralized state? Large welfare programs or pure market capitalism? Then, ask the same question again. But this time imagine that you have no idea what your social standing, income or talent level are going to be in the new state. What do you think should be done now?

This was certainly original, but what sets it apart most clearly from earlier theories is how abstract it is. When Hobbes wrote that the state of nature would be “solitary, poor, nasty, brutish and short,” he was experiencing something very similar: the English Civil War, which was raging while he wrote the Leviathan. For Hobbes, then, nature was very much “red in tooth and claw,” as the English poet Alfred Lord Tennyson wrote in the 1850 poem “In Memoriam.” This is why his social contract theory is founded on the inevitability of violence and struggle. For Rawls, looking out on the greenery of Harvard Square, the social contract is founded on open discussion and honest self-reflection. Even in the purest works of philosophy, it seems, circumstances matter.

Read A Theory of Justice here.

* For more on John Rawls’ theories, and responses to them, see the entry for Week 48, Day 6.

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