Empedocles (c.495–c.435 BC)

6. Biological explanations

The power of Empedocles as a thinker and his gifts as a poet are most happily married in the surviving extracts of his biology, where he shows an extraordinary capacity to get the reader to see the kinship of all nature. Sometimes parts of animals with homologous functions are just listed: ‘The same things are hair and leaves and close-packed wings of birds and scales, coming into being on sturdy limbs’ (fr. 82). Sometimes metaphor makes the point: ‘Thus do tall trees lay eggs: first olives…’ (fr. 79). Other animals are armed with horns or teeth or stings, but ‘Sharp-speared hairs bristle on hedgehogs’ backs’ (fr. 83).

Perception was explained by an ingenious theory of pores and effluences. It occurs when pores in the sense organ are just the right size to admit effluences of shape, sound, etc. given off by things (A92). The theory was employed to account for other phenomena also, such as chemical mixture (frs 91–2, A87) and magnetism (A89). Only like things (or things made like by Love) could have symmetrical pores and effluences. Empedocles posits fire in the eye for perception of light colours, a resounding bell in the ear to account for hearing, and breath in the nose for smelling (A86). Little of this material survives in his own words, except for an extended simile:

Empedocles made thinking a function of blood around the heart (fr. 105). Of all physical substances blood comes closest to an equal blending of all the elements, even though its origin still owes something to chance (fr. 98). This is what equips it to grasp the nature of things: earth with earth, and so on – but also Love with Love and Strife with Strife (fr. 109).