A good deal of work in the philosophy of time has been produced by people worried about Fatalism, which can be understood as the thesis that whatever will happen in the future is already unavoidable (where to say that an event is unavoidable is to say that no human is able to prevent it from occurring). Here is a typical argument for Fatalism.
(1) There exist now propositions about everything that might happen in the future. (2) Every proposition is either true or else false. (3) If (1) and (2), then there exists now a set of true propositions that, taken together, correctly predict everything that will happen in the future. (4) If there exists now a set of true propositions that, taken together, correctly predict everything that will happen in the future, then whatever will happen in the future is already unavoidable. (5) Whatever will happen in the future is already unavoidable.
The main objections to arguments like this have been to premises (2) and (4). The rationale for premise (2) is that it appears to be a fundamental principle of semantics, sometimes referred to as The Principle of Bivalence. The rationale for premise (4) is the claim that no one is able to make a true prediction turn out false.
A proper discussion of Fatalism would include a lengthy consideration of premise (4), and that would take us beyond the scope of this article. For our purposes it is important to note that many writers have been motivated by this kind of argument to deny Bivalence. According to this line, there are many propositions — namely, propositions about matters that are both future and contingent — that are neither true nor false right now. Take, for example, the proposition that you will have lunch tomorrow. On this view, that proposition either has no truth value right now, or else has the value indeterminate. When the relevant time comes, and you either have lunch or don’t, then, on the view in question, the proposition that you have lunch on the relevant day will come to be either true or false (as the case may be), and from then on that proposition will forever retain its truth value.
The view that Bivalence is false, and that, in particular, there are sometimes propositions about the future that are neither true nor false, is sometimes referred to as the “Open Future” response to arguments for Fatalism. One important presupposition of the Open Future response is that it makes sense to talk about a proposition’s having a truth value at a time, and that, moreover, it is possible for a proposition to have different truth values at different times. Thus, the Open Future response to arguments for Fatalism entails the following semantical thesis.
The Tensed View of Semantics:
- Propositions have truth values at times rather than just having truth values simpliciter.
- The fundamental semantical locution is ‘p is v at t’ (where the expression in place of ‘p’ refers to a proposition, the expression in place of ‘v’ refers to a truth value, and the expression in place of ‘t’ refers to a time).
- It is possible for a proposition to have different truth values at different times.
The Tensed View of Semantics can be contrasted with the following semantical view.
The Tenseless View of Semantics:
- Propositions have truth values simpliciter rather than having truth values at times.
- The fundamental semantical locution is ‘p is v’ (where the expression in place of ‘p’ refers to a proposition and the expression in place of ‘v’ refers to a truth value).
- It is not possible for a proposition to have different truth values at different times.
Other views that have (at least sometimes) been associated with the Open Future response to Fatalism include Taking Tense Seriously and The Growing Universe Theory, which will be discussed below.
Suggestions for Further Reading: Aristotle, De Interpretatione, Ch. 9; Besson and Hattiangadi forthcoming; Lewis 1986a; Markosian 1995; McCall 1994; Miller 2005; Sullivan forthcoming; Taylor 1992, Ch. 6; Torre 2011; van Inwagen 1983, Ch. 2.