Suppose I am going to live forever. I promise you that I will one day sing Yankee Doodle to you. But I never do. It seems like in the world where this happens, I do something wrong, namely broken my promise to you (if it is acceptable to break promises with good reason, then in all of my examples add the proviso that there is no good reason). But when do I break the promise or do this wrong? At any given time t, I am in compliance with the promise (i.e., my actions are compatible with the fulfillment of the promise).
I can run the same puzzle on a finite interval. Suppose I have the superpower of singing Yankee Doodle at any exact given time I wish, and I promise you that before noon I will start to sing Yankee Doodle. But I don't. I've done something wrong. But when? At any time before noon, I am still in compliance with the promise, so I haven't done anything wrong yet. At noon, it's too late to comply, so I have an excuse for not starting to sing at noon—it wouldn't be the fulfillment of the promise. So when have I done wrong?
There are a couple of moves one could make in response:
- We can say that the above paradoxes tell us something about the nature of time or action, such as that it is impossible for one to have an infinite number of choices.
- We can deny the principle that if you do wrong, you do wrong at some time. Denying this principle may push one towards four-dimensionalism, though perhaps the denial is less radical in the case of omissions than of commissions.
- We could conclude that certain kinds of open-ended promises are invalid. We could try to say that it is a necessary condition on the validity of a promise that the promise could (in a contextually relevant sense of "could") give one a reason to act on pain of violating it. Thus, I cannot validly promise you that the weather will be nice tomorrow, because the weather is not up to me, so I cannot (in the ordinary sense) get a reason to act on pain of violating the promise. In the Yankee Doodle cases, while I have a reason to sing Yankee Doodle at many different times, at no time do I have, or can have, a reason to sing Yankee Doodle on pain of violating the promise (because there is always more time). So the promise is not valid. This is an ad hoc restriction on promising: it is of the very nature of promises to give rise to reasons to do something on pain of violation of the promise.