  Geach’s review sent Prior back to the ancient sources, and he found Aristotle saying that some propositions about the future, namely propositions concerning events that are not determined at the time of utterance, are neither true nor false when they are uttered, since there is, at that time, as yet no definite fact with which they accord or conflict. Prior quoted Aristotle’s argument (in ch. 9 of De Interpretatione) for believing in such events: if the future were determined, ‘there would be no need to deliberate or take trouble, on the supposition that if we should adopt a certain course, a certain result would follow, while, if we did not, the result would not follow’ (Prior 1953: 322–323).