The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

WHEN ARISTOTLE WANTS, as he so often does, to convince us that living things have an end – a goal – and that they cannot therefore be purely explained by the workings of matter alone, he appeals not simply to the beauty of animal design, the devices by which they keep themselves alive in the face of the world’s vicissitudes, but rather to the fact that they develop in a regular way. In the Physics Aristotle tackles the claim that he attributes – rightly or wrongly it’s hard to say – to Empedocles that order can just ‘spontaneously’ emerge in the womb. Hence his argument that a child’s teeth require some goal-oriented process, underpinned by a formal nature, if they are to appear in the right place at the right time. In The Parts of Animals he returns to the attack. Now it’s the backbone that worries him. Empedocles apparently also claimed that vertebrae are distinct because the backbone just happens to twist and break during development. That, says Aristotle, can’t be right. The seed from which the embryo developed must already have had the potential to produce the vertebrae. That is why ‘a human being gives rise to a human being’ and not a horse. It’s one of his favourite sayings. It is a very deep truth. It is also not a compelling argument for it merely restates the obvious. How, exactly, does a human being give rise to a human being? It is one thing to say that Empedocles is wrong, quite another to show it. In the recesses of the womb, where no one can see, theories ar...