Pythagoreanism

“Pythagoreanism” names several things. First, the teaching of Pythagoras himself, which laid down a strictly ordered way of life and taught that after death the soul moves into another body, whether human or animal. Second, the philosophy of the thinkers Aristotle called “the so-called Pythagoreans”, who worked in the fifth and early fourth centuries BCE, above all Philolaus, who took limiters and unlimiteds as first principles and held that number is the key to understanding the cosmos, and Archytas, the first great mathematician of the tradition.

In later antiquity Pythagoras came to be treated as the source of almost all true philosophy, and many of the greatest Greek philosophers, including Parmenides, Plato and Aristotle, were called Pythagoreans with no historical justification.