Life's Ratchet: How Molecular Machines Extract Order from Chaos Read Online Free PDF Page B

that reason and emotion, supposedly part of the soul, could be thoroughly altered by injury. Didn’t this clearly show that Descartes’s last refuge of soul—the mind—could ultimately be explained by pure mechanism? No wonder La Mettrie’s more religious contemporaries were displeased.
    Because of his provocative writings, La Mettrie is sometimes seen as the bad boy of the Enlightenment. The rumor that he died while overeatingexpensive pheasant pâté did not help his reputation (although it seems likely he died of food poisoning). However, under the combative veneer of his writing, there was a thoughtful philosopher and one of the most uncompromising representatives of the mechanical philosophy.
    La Mettrie was a better provocateur and philosopher than scientist. But we can hardly fault him for that: While his explanations of procreation or “irritability” (see next paragraph) seem to us naive or laughable, he based them on what little was known about human physiology at a time when alchemical and ancient Greek ideas were still common. But his philosophy did not depend on such details.
    At the heart of his most famous work, L’homme machine , were two observations: First, the functions of body and mind could be greatly altered by physical influences and therefore could not be independent of them. Second, living tissue, such as muscle, could move on its own, even when removed from the body. Experiments performed during La Mettrie’s time demonstrated that isolated tissues could move when “irritated.” This so-called irritability indicated to La Mettrie that life possessed “inherent powers of purposive motion.” He put irritability at the center of his arguments, providing a list of ten examples, some quite gruesome, such as the frantic fluttering of headless chickens. In light of these observations, La Mettrie concluded that we cannot divorce the functions of the body or the mind from their physical nature. Instead, the functions must be the result of the physical and mechanical makeup.
    La Mettrie’s denial of the soul led to his being charged as an atheist (the standard charge for all philosophers who spoke out against Church doctrine). But he was more of a sincere agnostic: “I [do not] question the existence of a supreme being; on the contrary, it seems to me that the greatest degree of probability is in its favor. But that doesn’t prove that one religion must be right, against all the others; it is a theoretical truth that serves very little practical purpose.” For him, metaphysical and theological speculations about the soul served little purpose when a meal could make the “soul” happy and content and when we could see “to what excesses cruel hunger can push us.” La Mettrie, tongue-in-cheek, observed that “one could say at times that the soul is found in our stomach.” Observing that hunger, injury, drugs, and sleep affected people’s minds, he felt certain that the soul was just part of the body, even if he could notexplain in detail how it worked: “It is folly to waste one’s time trying to discover its mechanism. . . . There is no way of discovering how matter comes to move.”
    La Mettrie was wrong to state that “there is no way” to discover how organized matter moves, but we can agree with him that a supernatural soul is probably not needed to render us alive, as Aristotle believed, because the soul is so dependent on the physical state of the body. La Mettrie concluded that the “soul’s abilities” clearly depend on the “specific organization of the brain and the whole body.” Therefore, the soul was nothing other than the organization of the body and, as a separate concept, empty. It had taken two thousand years before somebody could freely acknowledge that a soul was not necessary to explain the motions of the body.
    La Mettrie’s agnosticism gave him a modern outlook on the methodology of science (although modern scientists are more diplomatic) and a somewhat