Diodorus Cronus c. 340 BC – c. 284 BC

Diodorus Cronus was a Greek philosopher of the Dialectical school descended from the Megarians and one of the most important logicians of the early Hellenistic age. Active at Alexandria under Ptolemy I and at Athens, he was famous in antiquity for the celebrated Master Argument, which sought to derive the proposition that only the actual is possible from premises about the necessity of the past and the impossibility of the impossible following from the possible. His innovations in modal logic, his arguments against the reality of motion, and his careful puzzle-cases shaped Stoic logic, especially through Chrysippus, and were debated by sceptics, Epicureans, and Aristotelians for centuries.