Disimplicature

Speranza

At least since Aristotle’s famous ‘sea-battle’ passages in On Interpretation 9, Kantotelians like Grice has been attracted to the doctrine of the open future—the doctrine that future contingent statements are never true. 

Such views, however, seem inconsistent with what John MacFarlane has called the determinacy intuition—the intuition, roughly, that if something has happened, then (looking backwards) it was the case that it would happen. This tension forms, in large part, what might be called the problem of future contingents. A dominant trend in semantic theorizing about future contingents—paradigmatically, Thomason (1970) and MacFarlane himself (2003, 2014)—has maintained that the apparent tension between the “open future” and the “determinacy intuition” is in fact merely apparent. In short, such theorists seek to maintain both of the following two theses: (i) the open future: Future contingents are not true, and (ii) retro-closure: From the fact that something is true, it follows that it was the case that it would be true. It is well-known that reflection on the problem of future contingents has in many ways been inspired by importantly parallel issues regarding divine omniscience, indeterminism, and time. In this paper, we take up this perspective, and ask what accepting both the open future and retro-closure predicts about omniscience. When we theorize about a perfect knower, we are theorizing about what an agent ought, and ought not, to believe. Our contention is that there isn’t an acceptable view of ideally rational belief given the assumptions of the open future and retro-closure, and thus this casts doubt on the conjunction of those assumptions.