Pythagoras... was intellectually one of the most important men that ever lived, both when he was wise and when he was unwise. Mathematics, in the sense of demonstrative deductive argument, begins with him, and in him is intimately connected with a peculiar form of mysticism. The influence of mathematics on philosophy, partly owing to him, has, ever since his time, been both profound and unfortunate.
...He was a native of the island of Samos, and flourished about 532 B.C. Some say he was the son of a substantial citizen named Mnesarchos, others that he was the son of the god Apollo; I leave the reader to take his choice between these alternatives. In his time Samos was ruled by the tyrant Polycrates, an old ruffian who became immensely rich, and had a vast navy....
The Greek cities of southern Italy, like Samos and Miletus, were rich and prosperous; moreover they were not exposed to danger from the Persians. The two greatest were Sybaris and Croton. Sybaris has remained proverbial for luxury; its population, in its greatest days, is said by Diodorus to have amounted to 300,000, though this is no doubt an exaggeration. Croton was about equal in size to Sybaris. Both cities lived by importing Ionian wares into Italy, partly for consumption in that country, partly for re-export from the western coast to Gaul and Spain. The various Greek cities of Italy fought each other fiercely; when Pythagoras arrived in Croton, it had just been defeated by Locri. Soon after his arrival, however, Croton was completely victorious in a war against Sybaris, which was utterly destroyed ( 510 B.C.). Sybaris had been closely linked in commerce with Miletus. Croton was famous for medicine; a certain Democedes of Croton became physician to Polycrates and then to Darius.
At Croton Pythagoras founded a society of disciples, which for a time was influential in that city. But in the end the citizens turned against him, and he moved to Metapontion (also in southern Italy), where he died. He soon became a mythical figure, credited with miracles and magic powers, but he was also the founder of a school of mathematicians. Thus two opposing traditions disputed his memory, and the truth is hard to disentangle. Pythagoras is one of the most interesting and puzzling men in history. Not only are the traditions concerning him an almost inextricable mixture of truth and falsehood, but even in their barest and least disputable form they present us with a very curious psychology. He may be described, briefly, as a combination of Einstein and Mrs. [Mary Baker] Eddy. He founded a religion, of which the main tenets were the transmigration of souls and the sinfulness of eating beans. His religion was embodied in a religious order, which, here and there, acquired control of the State and established a rule of the saints. But the unregenerate hankered after beans, and sooner or later rebelled. Some of the rules of the Pythagorean order were:
1. To abstain from beans.
2. Not to pick up what has fallen.
3. Not to touch a white cock.
4. Not to break bread.
5. Not to step over a crossbar.
6. Not to stir the fire with iron.
7. Not to eat from a whole loaf.
8. Not to pluck a garland.
9. Not to sit on a quart measure.
10. Not to eat the heart.
11. Not to walk on highways.
12. Not to let swallows share one's roof.
13. When the pot is taken off the fire, not to leave the mark of it in the ashes, but to stir them together.
14. Do not look in a mirror beside a light.
15. When you rise from the bedclothes, roll them together and smooth out the impress of the body.
All these precepts belong to primitive tabu-conceptions. Cornford (From Religion to Philosophy) says that, in his opinion, "The School of Pythagoras represents the main current of that mystical tradition which we have set in contrast with the scientific tendency." He regards Parmenides, whom he calls "the discoverer of logic," as "an offshoot of Pythagoreanism, and Plato himself as finding in the Italian philosophy the chief source of his inspiration." Pythagoreanism, he says, was a movement of reform in Orphism, and Orphism was a movement of reform in the worship of Dionysus. The opposition of the rational and the mystical, which runs all through history, first appears, among the Greeks, as an opposition between the Olympic gods and those other less civilized gods who had more affinity with the primitive beliefs dealt with by anthropologists. In this division, Pythagoras was on the side of mysticism, though his mysticism was of a peculiarly intellectual sort. He attributed to himself a semi-divine character, and appears to have said: "There are men and gods, and beings like Pythagoras." All the systems that he inspired, Cornford says, "tend to be otherworldly, putting all value in the unseen unity of God, and condemning the visible world as false and illusive, a turbid medium in which the rays of heavenly light are broken and obscured in mist and darkness."
The History of Western Philosophy, Bertrand Russell, Chapter 3