If F0, then T0 If F0, then F1 The following conditional does not meet this requirement, and is therefore a false statement according to Philo: If T0, then F0'' Indeed, Sextus says "According to [Philo], there are three ways in which a conditional may be true, and one in which it may be false." Philo's criterion of truth is what would now be called a truth-functional definition of "if ... then"; it is the definition used in modern logic. In contrast, Diodorus allowed the validity of conditionals only when the antecedent clause could never lead to an untrue conclusion. A century later, the Stoic philosopher Chrysippus attacked the assumptions of both Philo and Diodorus. References External links Selected Bibliography on the "Master Argument" in Diodorus Cronus and Philo the Dialectician with a bibliography on the problem of future contingents Hellenistic-era philosophers 4th-century BC philosophers Megarian philosophers Ancient Greek logicians