  If we step back for a minute and compare the sources for Pythagoras with those available for other early Greek philosophers, the extent of the difficulties inherent in the Pythagorean Question becomes clear. When trying to reconstruct the philosophy of Heraclitus, for example, modern scholars rely above all on the actual quotations from Heraclitus’ book preserved in later authors. Since Pythagoras wrote no books, this most fundamental of all sources is denied us. In dealing with Heraclitus, the modern scholar turns with reluctance next to the doxographical tradition, the tradition represented by Aetius in the first century CE, which preserves in handbook form a systematic account of the beliefs of the Greek philosophers on a series of topics having to do with the physical world and its first principles. Aetius’ work has been reconstructed by Hermann Diels on the basis of two later works, which were derived from it, the Selections of Stobaeus (5th century CE) and the Opinions of Philosophers by pseudo-Plutarch (2nd century CE). Scholars’ faith in this evidence is largely based on the assumption that most of it goes back to Aristotle’s school and in particular to Theophrastus’ Tenets of the Natural Philosophers. Here again the case of Pythagoras is exceptional.  Pythagoras is represented in this tradition but, as we have seen, Theophrastus in this case either adopted the view that, against all historical plausibility, assigns Plato’s later metaphysics to Pythagoras or Theophrastus’ doxography on the Pythagoreans was rewritten in the first century BCE. Thus, the second standard source for evidence for early Greek philosophy is, in the case of Pythagoras, corrupted. Whatever views Pythagoras might have had are replaced by late Platonic metaphysics in the doxographical tradition.