 In a series of articles during the 1920s and 30s the Polish logician Jan Łukasiewicz (1878–1956) advocated a particular interpretation of Aristotle’s discussion of the status of sentences about the contingent future, as developed in his sea-battle example. Łukasiewicz’s interpretation crucially rests on a rejection of the principle of bivalence. In fact, this kind of interpretation was not new, but had been formulated already by the Epicureans. However, Łukasiewicz presented this position more clearly than had ever been done before, and developed it with the aid of modern symbolic logic. He used his interpretation of Aristotle and the status of sentences about the contingent future as an argument against logical determinism and in favor of logical indeterminism, for which he declared his wholehearted support. In order to avoid determinism, he found it necessary to restrict the validity of bivalence by introducing a third truth-value. This truth-value, “undetermined”, is applied to contingent propositions regarding the future (McCall 1967, p. 64). For instance, a proposition stating that there will be a sea-battle tomorrow can be assigned the truth-value undetermined today. This is because today it is not given or definitely determined whether the sea-battle is actually going to take place tomorrow or not.