The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

But is the soul a cybernetic system? If the metaphor has any power, then it should illuminate Aristotle at his most concrete – that is, when he describes the heart–lung thermoregulatory cycle. Aristotle claims that he’s described how the heart beats and the lungs pump. Has he? The answer is not obvious from his verbal account. If, however, we grant his physics, chemistry and anatomy, and diagram his model using the block-and-arrow formalism of cybernetics, the structure of the mechanism becomes clear.* The diagram, which is isomorphic with his text, shows that his model works, but not as he thinks it does. He thinks he’s described an oscillator that will make the lungs expand and contract rhythmically; in fact he’s described a thermostat. He’s worked out how to keep the heart at a steady boil. But that is no mean accomplishment. For his system contains the essence of any homeostatic device, a negative feedback circuit. It truly is a cybernetic system. Credit for first inventing, or at least applying, negative feedback control usually goes to the Alexandrian scientist Ctesibius (fl. 250 BC), who incorporated it into the design of a water clock. Perhaps credit should also be given to Aristotle who, two centuries earlier, saw the need for such a device in living things and sketched, however fancifully, how it might work.