Born circa 570 B.C. on the island of Samos; died circa 500 B.C. Ancient Greek thinker, religious and political figure; founder of Pythagoreanism.

It is difficult to separate the meager facts about the life and teachings of Pythagoras from the legends that represent him as a demigod, perfect sage, heir to the knowledge of antiquity and the Near East, thaumaturgist, and magician. Pythagoras left his native Samos in protest against the tyranny of Polycrates. He may have visited Egypt and Babylonia during his travels—recent writers have suggested that Pythagoras was initiated into various secret doctrines of the Eastern priests. At a mature age (according to tradition, at 40), he settled in the southern Italian city of Croton, where he founded a strictly closed society of his followers, who already during his lifetime venerated him as a higher being. The doctrines and discoveries of Pythagoras that were preserved in the oral traditions of the Pythagorean society cannot be separated from the ideas of his followers, who often ascribed to him their own intellectual initiatives.

In mathematics, Pythagoras is credited with the systematic introduction of proofs into geometry, the construction of the plane geometry of rectilinear figures, the origination of the theory of similitude, the proof of the theorem that bears his name (the Pythagorean theorem), and the construction of certain regular polygons and polyhedrons. Also associated with Pythagoras are theories of odd and even numbers, prime and composite numbers, figúrate numbers, and perfect numbers and theories of arithmetic, geometric, and harmonic proportions and means.