Begin thus from the first act, and proceed; and, in conclusion, at the ill which thou hast done, be troubled, and rejoice for the good.

With the exception of a few remarks by Xenophanes Heraclitus Herodotus Plato Aristotle and Isocrates we are mainly dependent on Diogenes Laërtius Porphyry and Iamblichus for the biographical details. Writings
No texts by Pythagoras are known to have survived although forgeries under his name — a few of which remain extant — did circulate in antiquity. However because legend and obfuscation cloud his work even more than that of the other pre-Socratic philosophers one can give only a tentative account of his teachings and some have questioned whether he contributed much to mathematics and natural philosophy.

It was said that he was the first man to call himself a philosopher or lover of wisdom and Pythagorean ideas exercised a marked influence on Plato and through him all of Western philosophy. His followers pursued the religious rites and practices developed by Pythagoras and studied his philosophical theories. The Pythagorean meeting-places were burned and Pythagoras was forced to flee the city.