 Like the Stoics, the Epicureans were also occupied with we may call logical determinism. According to the principle of bivalence, every proposition P is either true or false. If there is a future tense proposition predicting every future occurrence before it happens–it doesn’t matter whether it has ever been expressed–true at all times before the event, it would seem that the future is fixed or settled. Aristotle tackled this problem in De Interpretatione 9, though it is unclear whether the parties to the Hellenistic debate were familiar with his contribution. Though an argument for the pre-determination of the future from bivalence alone is possible (there may be hints at De fato 21, 29), in Cicero’s presentation of the issues, the role of the principle of bivalence is to lend support to causal determinism. The idea seems to be that the truth of a proposition at a given time depends on the state of the world at that time and that the facts about the world that bear on the truth of a future tense prediction must be about causes then operative sufficient to bring about the predicted event.