  Apart from the various logical puzzles and sophisms, there are only two topics on which we can be sure of a positive contribution to logic by members of the Dialectical school. These are the positions of Diodorus and Philo on the theory of conditionals and on modal logic. Both topics involve notorious difficulties and were extensively and intensely discussed by Hellenistic logicians; so much so that the disputes became part of the general knowledge of the intelligentsia of the time (SE, Against the Grammarians 309-10). Moreover, the theory of modalities was believed to have far-reaching results for other areas of philosophy.