The Lagoon: How Aristotle Invented Science

by Armand Marie Leroi

idea that nature does not make jumps is closely allied to another: that nature is organized into a linear scale that runs from rocks to God via plants, animals and humans. The scala naturae – the Ladder of Nature – as it came to be known, appears in the cosmic structure of The Timaeus which is nothing if not hierarchical. It is also one of Aristotle’s themes. Every natural thing may be, for him, a form and matter – eidos and hylē – compound, but the relative importance of the components varies. In rocks hylē predominates; in living things eidos does. Among living things there’s a ladder of increasing complexity too, plants to humans, running successively on uni-, bi- and tripartite souls. In The Generation of Animals Aristotle elaborates this ladder of life within the animals and underwrites it with embryology and physiology. He begins by linking his scale of progeny ‘perfection’ (how advanced they are at birth) to their parents: ‘Nature’s rule is that perfect offspring will tend to be produced by a more perfect sort of parent.’ Parental perfection depends on intrinsic heat, hot being better than cold. Heat is reflected in the composition of their uniform parts, hot animals being more fluid and less earthy than cold ones. Heat also reflects anatomy since hot animals have lungs and more elaborate thermoregulatory devices than cold ones. Hot animals also tend to be larger, live longer and be more intelligent than cold animals. The result is a ladder of perfection that reache...