Greek works On Ways of Life have been seen to consist in either collections of biographies or proper philosophical treatises. Recently, a unitary reading of this literary phenomenon has been advanced, but some fundamental evidence has escaped attention. This evidence, along with what remains of Epicurus and Chrysippus’ Peri biōn, suggests that in antiquity this label actually encompassed two essentially different genres: a mostly biographical one, which was cultivated by fourth/third-century BC Peripatetic philosophers and imperial writers, and a moral-philosophical one, which was first developed by Epicurus and Chrysippus and then cultivated by Academic and Peripatetic thinkers in the Hellenistic period and in later centuries.