Abstract

My dissertation deals with the Master Argument of Diodorus Cronus, a contemporary of Aristotle's. The argument was one of the most famous pieces of temporal and modal reasoning in ancient philosophy. It purports to prove that a proposition is possible if and only if it is true or will be true. The argument runs as follows: Everything that is past and true is necessary; The impossible does not follow the possible; Therefore, nothing is possible which neither is nor will be true. Unfortunately, all accounts of the Master that have survived are so sketchy that we cannot determine whether the argument is valid or not. ;Several reconstructions of Diodorus' argument have been proposed. The purpose of the reconstructions is to show, using the resources of modal and tense logics, that the argument is valid. I analyze and critique most of these proposals, arguing in the final chapter for a new reconstruction which I believe to be more defensible than existing ones. ;The Master Argument is important for several reasons. It elicited much discussion among ancient philosophers and logicians both because of its reduction of modal logic to tense logic and its bearing on the free will/determinism debate. But, its influence also extends to contemporary philosophy and logic. In the 1950s and 60s, the Master inspired formal work on Diodorean systems. Much of the work on the calculus of tenses, e.g., by Prior, was undertaken in view of investigating Diodorus' argument. Finally, the literature that the argument has spawned has enriched and deepened our understanding of the connections between matters modal and temporal