Aristotle admits the existence of truly contingent events and corresponding truly contingent propositions. According to many scholars, his answer to deterministic arguments is that future contingent propositions are neither true nor false before the time of the events expressed by them. Ammonius (active in the late fifth and early sixth centuries AD) rejects this reading of Aristotle. Instead, he proposes a distinction between definitely and indefinitely true or false propositions. This chapter explores the philosophical merits of Ammonius’s solution to the problem of future contingent propositions.