  We do not know what motivated Diodorus to introduce his modal  notions.[1]  But we know that Hellenistic philosophers generally regarded Diodorus' modal notions as jeopardizing freedom — a since they rule out the possibility that something that never happens, or is never true, is nonetheless possible. Thus, if ‘Dio goes to Corinth’ is and will be false, then ‘Dio goes to Corinth’ is impossible, and then, or so the thought went, it is impossible for Dio to go to Corinth. In this context it becomes plain why our sources stress the fact that something can be Philonian possible without ever being true or obtaining.This is the relevant difference from Diodorus with respect to logical determinism, the point being that Philo's modalities, unlike Diodorus’, do not unduly limit the scope of contingency.