 We know very little about Philolaus’ life. Only one brief and not very reliable ancient life of Philolaus survives, that of Diogenes Laertius (VIII 84–5). Diogenes includes Philolaus among the Pythagoreans; indeed he is, in fact, one of the three most important figures in the ancient Pythagorean tradition, along with Pythagoras himself and Archytas. The central evidence for Philolaus’ date is Plato’s reference to him in the Phaedo (61d–e). Socrates’ interlocutors, Simmias and Cebes, indicate that they had heard Philolaus in Thebes at some time before the dramatic date of the dialogue (399 BC). The passage suggests that Philolaus was no longer in Thebes in 399, but there is no indication that he has died. In order for Philolaus to have been a prominent teacher by the later fifth century he must have been born no later than 440. There are other indications that he was born even earlier. Both Philolaus and Eurytus are identified by Aristoxenus as teachers of the last generation of Pythagoreans (D. L. VIII 46), who were in their twenties in 400 and active in the first half of the fourth century. Philolaus is also said to be the teacher of Eurytus (Iamblichus, VP 139), however, so that the tradition makes most sense if Eurytus is born ca. 440, and Philolaus belongs to the preceding generation and is thus born ca. 470. Such a dating would also fit with the tradition that Philolaus was the teacher of and thus somewhat older than Democritus (D. L. IX 38), who was born ca. 460. It is even less clear when he died, but one report suggests that he may still have been alive in the early 380s, when Plato first visited southern Italy (D.L. III 6). If he lived from ca. 470 to ca. 385, Philolaus is an approximate contemporary of Socrates. Plutarch’s story that as a young man Philolaus was one of two to escape the burning of the Pythagorean meeting place in Metapontum in 454 (On the Sign of Socrates 583a) would be consistent with this dating, but earlier versions of the story do not mention Philolaus (Aristoxenus in Iamblichus, VP 249–50) so that it is far from certain that he was involved in the incident.