DIODORUS CRONUS (4th century B.C.), Greek philosopher of the Megarian school. Practically nothing is known of his life. Diogenes Laërtius (ii. 111) tells a story that, while staying at the court of Ptolemy Soter, Diodorus was asked to solve a dialectical subtlety by Stilpo. Not being able to answer on the spur of the moment, he was nicknamed ὁ Κρόνος (the God, equivalent to “slowcoach”) by Ptolemy. The story goes that he died of shame at his failure. Strabo, however, says (xiv. 658; xvii. 838) that he took the name from Apollonius, his master. Like the rest of the Megarian school he revelled in verbal quibbles, proving that motion and existence are impossible. His was the famous sophism known as the Κυριεύων. The impossible cannot result from the possible; a past event cannot become other than it is; but if an event, at a given moment, had been possible, from this possible would result something impossible; therefore the original event was impossible. This problem was taken up by Chrysippus, who admitted that he could not solve it. Apart from these verbal gymnastics, Diodorus did not differ from the Megarian school. From his great dialectical skill he earned the title ὁ διαλεκτικός, or διαλεκτικώτατος, a title which was borne by his five daughters, who inherited his ability.
See Cicero, De Fato, 6, 7, 9; Aristotle, Metaphysica, θ 3; Sext. Empiric., adv. Math. x. 85; Ritter and Preller, Hist. philos. Gr. et Rom. chap. v. §§ 234-236 (ed. 1869); and bibliography appended to article Megarian School.