Pythagoras c.580-c5.00BC
Greek philosopher, mystic and mathematician

Pythagoras was probably born in Samos, although the traditions regarding his life are confused. About 530 he left Samos, perhaps because of enmity to the ruler Polycrates, and settled in Croton, a Greek colony in southern Italy, where he attracted followers and established a community with its own rule of life. Its members, and members of other Pythagorean societies that grew up during his lifetime and later, were active in politics and were eventually suppressed. He may later have been exiled to Metapontum, where he died. Pythagoras left no writings, and his whole life is shrouded in myth and legend.

Pythagoreanism was first a way of life rather than a philosophy. Its principal belief was in the immortality and transmigration (ie reincarnation) of the soul, which is imprisoned in the body; and it emphasized moral asceticism and purification and various ritual rules of abstinence (most famously, from beans, although the reason for this is unclear). By leading a pure life, the soul can eventually achieve its release from the body, as in Orphism.

Pythagoras is also associated with mathematical discoveries involving the chief musical intervals, the relations of numbers, the theorem on right-angled triangles which bears his name, and with more fundamental beliefs about the understanding and representation of the world of nature through numbers. The equilateral triangle of 10 dots, the tetracys ('foursome') of the decad, itself became an object of religious veneration, referred to in the Pythagoran oath 'Nay, by him that gave us the tetracys which contains the fount and root of ever-flowing nature'.

It is impossible to disentangle Pythagoras's own views from the later accretions of mysticism and neoplatonism, but he had a profound influence on Plato and on later philosophers, astronomers and mathematicians.

Bibliography: J S Kirk et al, The Presocratic Philosophers (2nd edn, 1983); G E R Lloyd, Early Greek Science: Thales to Aristotle (1970).