Abstract: Central passages: Cicero On Fate 11–17; Alexander of Aphrodisias On Fate 208.15–21.Critics of the Stoics tried to show up an inconsistency between Chrysippus’ acceptance of divination, on the one hand, and his conception of contingency (and thus indirectly free action), on the other. The argument claims that, since theorems of divination connect, in a conditional, a proposition about the past with one about the future, and since the necessity of the former is transferred to the latter, future occurrences—as far as covered by divination—are all necessary. In the first part of this chapter, the argument is analysed in detail, and several logical difficulties contained in it are unravelled. The second part is concerned with Chrysippus’ counter-argument. By determining that divinatory theorems are correctly expressed as negated conjunctions rather than conditionals, Chrysippus successfully blocks his opponents’ argument: what is genuinely predicted by diviners is not necessitated through the prediction, because the relation between sign and predicted future event does not ‘transmit’ necessity. Universal regularity between sign (-type) and predicted event (-type) does not suffice to make a future event necessary. There is no ‘causal chain’ connecting them. Theorems of other sciences, for example, medical theorems that express an empirical (as opposed to logical) connection between things/events, make true Chrysippean conditionals. However, human freedom as conceived by the Stoics is not thereby threatened.

Keywords: causal chain, causation, Chrysippus, conditionals, divination, prediction,