Anaxagoras
Greek Presocratic philosopher (c. 500–428 BCE), born in Clazomenae in Asia Minor and later settled in Athens, where he became the first philosopher documented to have established continuous residence, exerting decisive influence on Pericles, whose teacher and close friend he was, and probably also on Socrates and Euripides. His central cosmological contribution was the doctrine of the 'seeds' (spermata), or infinitely divisible particles: unlike Empedocles, who reduced all reality to four elements, Anaxagoras held that matter contains an infinite number of distinct basic qualities, each present in everything in varying proportions —'in everything there is a portion of everything'— so that what we call 'gold' is simply matter in which the quality of gold predominates, while all other qualities are present in it in minute but real proportions. To explain the origin of motion and cosmic order, he introduced the concept of Nous (Mind or Intellect), an ordering principle separate from matter, infinite, self-governing and pure, which sets in motion an original rotation from which the entire cosmos becomes organised —an innovation Aristotle praised for introducing, for the first time, a rational and teleological cause into Greek natural philosophy, though he criticised him, echoing Socrates's complaint in Plato's Phaedo, for failing to apply it with sufficient mechanistic consistency. Anaxagoras also championed naturalistic, non-mythological explanations of astronomical phenomena, holding that the sun was a mass of incandescent stone larger than the Peloponnese and that the moon reflected its light and received the Earth's shadow during eclipses —theses that led to his being charged with impiety (asebeia) at Athens in a trial with political undertones aimed at Pericles; condemned or threatened with death, he was forced to flee to Lampsacus, where he founded a school and died honoured by the local community.