- Whether an arrow is moving now depends on where it will be in the future.
- If the future is open, there is no fact about where the arrow will be in the future.
- If if whether p depends on how A is, and there is no fact about how A is, then it is not a fact that p.
- So, if the future is open, no arrow is moving now.
Premise 1 is the most controversial one. Suppose that an arrow has been flying for half a second. There are two metaphysically possible worlds. In the first, it continues moving as usual. In the second, its motion instantly reverses after this moment, so that this moment is the furthest point in its flight. In the second world there is no more reason to say that the present moment is the last moment of forward motion than to say that it is the first moment of backward motion. So we shouldn't say the arrow is moving forward in the second world.
Hence there are worlds that differ on whether the arrow moves now and yet that differ only in the future positions of the arrow. That gives us reason to accept 1.
Premise 2 is particularly clear given theism: God can miraculously relocate the arrow if he so chooses. But I think premise 2 is going to be plausible on other views, too.
12 comments:
Premise 1 is worded with regard to mere movement; the defense of Premise 1 is worded with regard to forward vs. backward movement. Whether the arrow is moving forward or backward doesn't change the fact that it is moving.
In any case, even if I granted that there are instants, I don't think we should grant that objects are EVER moving at an instant. If you think of it like frames of a film, doesn't it seem obvious that nothing is ever moving on any given frame? It's a sequence of stills. It seems to me that nothing ever moves on THAT view. On presentism, when one says "the arrow is moving now", they mean during the course of them saying that sentence. And indeed, the arrow could stop during that couple of seconds, in which case the person usually says "oh, I guess it's not anymore".
I assumed that if an arrow is moving, it is moving in some direction.
I guess it could in principle also be rotating, but that isn't happening in the case at hand.
You could just rephrase it as "an arrow is never moving forward at any instant", and the argument would go through just fine. I don't think there are any instants, but, even if there were the real issue is what I mentioned about single frames vs. what the presentist actually means when they say "the arrow is moving". They mean that it is in motion during the course of their uttering the sentence. They don't mean that it will definitely continue in motion (perhaps it will; perhaps it won't).
With regard to Premise 2: How about a negative fact:If an arrow is moving, there might not be an identifiable fact about where it IS, but could there be a fact of where it ISN'T?
Richard H: Do you mean "where it ISN'T" at some future point in time? If so, then I doubt a presentist can accept that. There just aren't any facts at all about the future, on presentism, and we normally point to the present tense phrasing of "is" or "isn't" in questions like yours to further emphasize the cognitive dissonance of talking about future facts.
Michael:
Take the tensed proposition p expressed by "The arrow is moving". If my argument is right, then on open future views p is never true. What may be true, however, is that the arrow was moving: that the open futurist presentist can say with a clear conscience.
The open future presentist says "the arrow is moving", and she means during the course of her speaking the sentence. It is indeed moving during that time; she does not speak falsely in saying it. Moreover, I think the B-theorist has a harder time of this, since the arrow actually never moves, but exists statically and unchangingly as a 4-dimensional smear.
While she's yet speaking, the truth value of the sentence isn't fixed (assuming an open future). Only just after she has spoken is it fixed. But by then the statement is about the past.
Why isn't it true during the course of the sentence that the arrow is moving? If a person reports about a current, ongoing event, they speak truthfully unless they are still calling it current and ongoing after it has stopped.
But at any particular time during the speaking, the arrow might have stopped (that depends on the future). It's only in hindsight that we can say it was moving.
If it stopped, then the statement would cease being true, and the person would normally change course and say it isn't moving anymore. In the course of their saying that, it might start moving again, in which case they'd change course again and say "there it goes again". They have yet to speak falsely....
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