Symposion, 5, 1 (2018): 9-10 The Hidden Future Alex Blum Abstract: We argue that the part of the future which is up to us is in principle unknowable. Keywords: cannot be, omnipotence, omniscience, true, truth-value. It is reasonable to assume that we may not know what we are going to do on a particular Tuesday, even if it is all up to us. But it doesn't appear reasonable to assume that it is impossible for us to know what we are going to do on a particular Tuesday, if it is all up to us. But there is a straight forward argument which shows that we cannot know what we are going to do on a particular Tuesday or on any other day. For if we know what we are going to do on a particular day, say, go to the lecture, then it is true that we are going to go to the lecture on that day, and thus it cannot be (not could not have been) true that we are not going to attend the lecture on that day. But if we can change our mind and not attend the lecture on that day then we can make the true proposition that we will attend the lecture on that day false. But that is impossible. For what is true cannot be (not could not have been) false.1 Nor can a proposition change its truth value.2 If the above argument is sound, then an omnipotent being who can change his mind cannot possibly know the future. Omniscience would then be limited to the past and the present. But this does not stop us or an omniscient being from forming plans for the future and on the appropriate occasion to act on them. The future may then be open, as Aristotle contended,3 and remain open till it becomes the present.4 1 It is "a truth of the logic of modalities" that "if a proposition is true it is self-necessary." (Von Wright 1957, 122). He explains: "... relative to the hypothesis (supposition) that it is true, a proposition cannot be but true (is necessarily true). Thus not: if a proposition is true, then it is (absolutely) necessary. But: if a proposition is true, it is selfnecessary." (Von Wright 1957, 122) For additional discussion, see Blum (2011). 2 For it would mean that one and the same state of affairs will both occur and not occur. For further discussion, see Blum (2013). 3 See Aristotle, De Interpretatione ch 9,19a 30-40, in McKeon (1941, 48). 4 I am deeply grateful to Menachem Domb, Yehuda Gellman, Peter Genco, Asa Kasher and Danny Statman for their helpful comments. Alex Blum 10 References Aristotle. 1941. "De Interpretatione (On Interpretation)." Translated by E.M. Edghill. In The Basic Works of Aristotle, edited by Richard McKeon, 38-61. New York: Random House. Blum, Alex. 2011. "The Force of Truth." Philosophical Investigations 34 (4): 393395. ---. 2013. "On Changing the Past." Organon F 20 (3): 377-378. McKeon, Richard, ed. 1941. The Basic Works of Aristotle. New York: Random House. Von Wright, Georg Henrik. 1957. "A New System of Modal Logic." In Logical Studies, 89-126. London: Routledge & Kegan Paul.