Topics Logic

Question Following along from http://www.askphilosophers.org/question/2039: "Does the law of bivalence demand that a proposition IS either true or false today? What if the truth or falsity of this proposition is a correspondence to a future event that has yet to occur?" What's problematical about saying "yes, it's either true or false, but I don't happen to know which"? Is that substantively different from saying the same thing about an open problem in science or mathematics, to which the answer is presumably knowable but happens not yet to be known? The questioner seems to be demanding both that there be an answer, which may be a reasonable thing to want, and to be able to know what the answer is, which isn't necessarily reasonable. Is it reasonable always to expect somebody (other than deity) to know the answer to a question?

Accepted:
July 9, 2008

Comments

The issue about so-called "future contingent" propositions isn't just about whether we're in a position to know whether they're true, but whether there are any facts for them to pick out. And that issue arises from a tempting but controversial metaphysical picture: reality as it were "unfolds" in time. Reality consists at least of what's so now, and perhaps as well of what's already taken place, but on this picture there simply are no definite facts about future events.

This may seem odd at first, but a couple of examples might make it seem less so. Suppose you think that people make choices that are free in the sense of being not just uncoerced but undetermined. Mary is a juror in the penalty phase of a trial. Tomorrow she will decide whether to vote that the defendant should be executed. If you think that there is nothing that fixes her decision before it's made, you might wonder what it would mean for there to be a correct answer to the question "What will she decide?" before she actually decides. Or another example: a quantum particle is about to enter an apparatus that will measure its "spin" in some direction. The usual view of quantum theory is that the outcome of the measurement ("spin-up" or "spin-down") is a genuine chance event, undetermined by the state of the particle and the apparatus. It's true that after the particle passes through the apparatus, there will be an answer to the question "Did the particle register spin-up? Or spin-down?" But again, one might think that there's nothing in reality that fixes the answer before the event actually happens. On this way of looking at things, it's not just that we don't know in advance; it's that there's no determinate fact to be known. If we accept this view, then it's a metaphysical mistake to say "it's either true or false, but I don't know which." It isn't true and it also isn't false; it's indeterminate. Reality itself is gappy, so to speak.

I hasten to add: not only is this picture controversial, but there are well-developed alternatives according to which all events are equally "real." It's simply that some are later than others, and it may be that the patterns in the fabric of events don't yield laws which tie later events tightly to earlier ones. But even if that's the best view, it's worth seeing that the controversy isn't just over what we can know but about the structure of reality.