 Aristotle apparently believed that, where future contingents are concerned, “p or not-p” is true but the two halves of the disjunction have indeterminate truth values. This idea seems logically counter-intuitive. If p and not-p are indeterminate, shouldn’t “p or not-p” also be indeterminate? For a brief period, Hartshorne defended the Aristotelian idea (Hartshorne 1939), but he discovered a more parsimonious solution (Hartshorne 2011c, 123). Instead of locating the indeterminacy of the future in truth values, he focused on predicates that reflect the extent to which the future is open for any given event. Either all causal conditions are such that the sea battle will occur, or no causal conditions are such that it will occur, or it is permitted by some but not all causal conditions (cf. Hartshorne 1970, 145). It “will” occur means that all the possibilities for tomorrow which are still left open involve the occurrence in question; while it “may” occur means that some of the open possibilities involve the occurrence; and it “will not” occur means that none of the possibilities involve it (Hartshorne 1941, 100).