SOURCE: W. K. C. Guthrie, "Pythagoras and the Pythagoreans," in A History of Greek Philosophy, Vol. I, Cambridge at the University Press, 1962, pp. 146-340.

In the following excerpt, Guthrie highlights evidence of Pythagoras's teachings and life in the works of his contemporaries and other important figures in the history of ancient Greece.

The history of Pythagoreanism is perhaps the most controversial subject in all Greek philosophy, and much about it must remain obscure. For this there are several good reasons, which are themselves not without interest. The subject is not only obscure but highly complex, and its complexity demands above all a clear statement at the outset of what is to be attempted and the outline of a plan of campaign.

First, is it justifiable to put a general account of the Pythagoreans at this early point in the exposition? Pythagoras was a contemporary of Anaximenes, but his...