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The Humpty-Dumpty Problem

Even when we understand their parts, living things are hard to put back together

Robert L. Dorit

Click to Enlarge ImageThe publication in 1637 of René Descartes’ Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth in the Sciences changed the practice of science forever. In it, he poured the foundations of modern science by putting forth two powerful and interrelated theses. The first embraced reductionism as a way of knowing: Descartes committed himself to “divide each of the difficulties under examination into as many parts as possible, and as might be necessary for its adequate solution,” and to “conduct my thoughts in such order that, beginning with those objects that are simplest and most readily understood, I might ascend little by little, and, as it were, step by step, to the knowledge of the more complex.” Later in the same work, he deployed one of the most durable metaphors of Western intellectual thought: He argued that the body was best thought of as a machine.

By coupling those two ideas—that complex machines could be understood by taking them apart, and that living beings are essentially machines—Descartes set the stage for the age of science. He argued persuasively that living systems emerge as the physical consequences of material forces. For example, also in his Discourse, he explained the workings of the heart:

I wish it to be considered that the motion which I have now explained follows as necessarily from the very arrangement of the parts, which may be observed in the heart by the eye alone, and from the heat which may be felt with the fingers, and from the nature of the blood as learned from experience, as does the motion of a clock from the power, the situation, and shape of its counterweights and wheels.

The living world was thus the legitimate province of the sciences and its inner workings could be probed and understood through logic, observation and experiment.

The task of this new science would henceforth consist in disassembling the seemingly complicated machinery of life into its simplest components, which could then be cataloged, prodded, manipulated and described. According to Descartes’ model, any real understanding of the body could only come from taking it apart, just as one takes apart a machine to discover its inner workings. If we wish to understand how a clock tells time, according to this model, our job is to disassemble it. Understanding a clock means understanding its springs and gears. And the same is true of living “machines.”

This notion of the body as a machine would clear away centuries of intellectual detritus: By arguing that the body was the sum of its interacting parts, and, more importantly, by suggesting that the study of those parts would reveal the workings of the body, Descartes shifted centuries of scientific and philosophical discussion about imponderable life forces and inexplicable animist vapors. (Lest we go overboard in praising Descartes, he clearly panicked at the last moment. He exempted human beings from the ground rules he set for other living organisms. In so doing, he sowed 400 years of confusion and discord with his notion that the mind and the body were separate phenomena, governed by separate rules.)

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