Very little is known about the life of Philo of Megara, or Philo Dialecticus. Since he was a pupil of Diodorus Cronus at the same time as Zeno of Citium, the founder of the Stoa (cf. Diogenes Laertius, DL 7.16), he was very probably active in Athens in the last decade of the 4th century BCE. He was not, as is assumed in the older literature, a member of the Megarian school of philosophy, but belonged to a separate sect, the Dialecticians. Hence there is no reason to make Megara his birthplace. From the titles of two lost treatises by the Stoic Chrysippus that were directed against Philo, we learn that Philo wrote On Signs (DL 7.191) and On Moods (of Argument) (DL 7.194). He also wrote a dialogue called the Menexenus, in which the five daughters of the Dialectician Diodorus...