Philolaus 470 BC – 385 BC

Philolaus of Croton was a Greek Pythagorean philosopher and the first member of the Pythagorean school whose writings survived into the classical period. His fragments, preserved by later authors, articulate a cosmology in which the world is built up from limiters and unlimiteds joined by harmony, and a celebrated astronomical model in which a central fire, rather than the earth, stands at the center of the universe. He was the principal source for Plato's own engagement with Pythagorean thought, and Aristotle drew on his work in his accounts of early Greek philosophy.

Philolaus of Croton was born around 470 BC in the Pythagorean community of southern Italy, possibly at Croton itself or at Tarentum. After the political reaction of the late fifth century scattered the Pythagorean settlements he made his way north and lived for an extended period at Thebes, where Plato's Phaedo represents the young Cebes and Simmias as having heard him. According to Diogenes Laertius and an anecdote in the Life of Plato, Plato is supposed to have purchased three Pythagorean books, almost certainly Philolaus's, from his heirs.

Philolaus is reported by ancient tradition to have been the first Pythagorean to publish a written exposition of the school's doctrines. The work is lost, but more than twenty fragments are preserved in Stobaeus and indirectly in Aristotle, and modern scholarship — after a long period of suspicion — now generally accepts a substantial core as authentic.

He taught that all knowable things have number, that everything is composed of limiters and unlimiteds bound together by harmonia, and that the cosmos is structured around a central fire — Hestia — about which the earth, a counter-earth, the sun, the moon, and the five visible planets revolve, making ten heavenly bodies in the perfect Pythagorean number. His displacement of the earth from the centre prepared a long path that would lead through Aristarchus to Copernicus. He is presumed to have died around 385 BC.