Abstract: Central passages: Cicero On Fate 20–21, 26–28, 37, On Divination I 125–6. The first argument: Chrysippus assumes as true a weak, non-modal form of logical determinism (if p obtains at t, then for all t’ earlier than t it is true at t’ that p will obtain at t). From this assumption he argues for the truth of his theory of causal determinism, by showing that the latter is a necessary condition of the former. This argument differs considerably from the argument for the truth of future propositions to their necessity (related to the Mower Argument), which Epicurus is said to have attacked. Cicero confuses the two. The second argument: Chrysippus, as most Stoics, believed in divination as a science. He construes an argument from the existence of this science to his type of causal determinism by showing that causal determinism is a necessary condition for the existence of the science of divination.

Keywords: causal determinism, Chrysippus, Cicero, divination, Epicurus, logical determinism, Mower Argument,