 In the case of most ancient authors, the assumption is that a text handed down in their name is genuine, unless strong reasons can be given for regarding it as a forgery. This standard assumption does not apply to the Pythagorean tradition. Many more demonstrably spurious texts have survived (collected in Thesleff 1965) than texts that can with confidence be regarded as genuine. Some forgeries may have been produced for monetary reasons; a text of a “rare” work by a Pythagorean author could fetch a large sum from book collectors. There were characteristics unique to the Pythagorean tradition, however, that led to a proliferation of forgeries. Pythagoras himself wrote nothing. Starting as early as the later fourth century BC (Burkert 1972a, 53–83; Huffman 1993, 22–6), however, he came to be regarded, in some circles, as the philosopher par excellence, to whom all truth had been revealed. All later philosophy, insofar as it was true, was a restatement of this original revelation (see, e.g., O’Meara 1989). In order to support this view of Pythagoras, texts were forged in the name of Pythagoras and other early Pythagoreans, showing that they had, in fact, anticipated the most important ideas of Plato and Aristotle. These pseudo-Pythagorean texts are thus characterized by the use of central Platonic and Aristotelian ideas, expressed in technical Platonic and Aristotelian terminology. The date and place of origin of these pseudo-Pythagorean treatises is difficult to determine, but most seem to have been composed between 150 BC and 100 AD (Burkert 1972b; Centrone 1990 and 2014; Moraux 1984); Rome (Burkert 1972b) and Alexandria (Centrone 1990 and 2014) are the most likely places of origin. As a result of these unique features of the Pythagorean tradition, any fragment assigned to a Pythagorean philosopher such as Philolaus must be examined carefully before it can be accepted as genuine.