Anaxagoras of Clazomenae

(c. 500/499–428/427 BC)

The first philosopher to teach in Athens, although indicted probably c. 450, on charges of impiety, and for holding an astronomical theory that included the view that the sun is a red hot body, larger than the Peloponnese, from which the moon derives its light. He was exiled and died in honour at Lampsacus. Surviving fragments are few, and the interpretation of his philosophical system controversial. He assigned a fundamental cosmological role to mind both as the initiator of motion and as the animating principle of plants and animals. His most characteristic doctrine is that there is ‘a portion of everything in everything’, meaning that whatever a thing changes into is in some imperceptible way already present in it before the change; Anaxagoras also held that all qualities are present in all things although only those that are preponderant will emerge. Things are homoiomereiai (things with like parts) of each other. The principle of homoeomereity has been subject to multiple interpretations, but the idea that change is a matter of passing on something that is already present had a lasting influence in the metaphysics of causation, especially in biology.