- (Premise) If presentism is correct, it is impossible that something has a timeless existence.
- (Premise) Possibly, there is no time.
- (Premise) Necessarily, something exists.
- (Premise) Necessarily, if there is no time, everything has a timeless existence.
- There is a world w where there is no time and yet something exists. (2 and 3)
- In w, something has a timeless existence. (4 and 5)
- Presentism is not correct.
Here is an intuition in favor of 1. A timeless mode of being is an intrinsic characteristic of a being. Now it should be possible to combine beings with all sorts of possible intrinsic characteristics. Thus, if a timeless mode of being is possible, then it should be possible to have a world much like ours but where there is also a timeless being. But that would be a world where presentism is false, since then existence of timeless beings is incompatible with presentism, as presentness would no longer be coextensive with existence. Now, we make this move: as soon as it is admitted that such a world is possible, what reason do we have to think it's not actual? We are in no position to know there aren't any such timeless beings, given that they could coexist with beings like us. And now, while presentism could be true, we have little reason to think it is. So presentists should accept 1.
Maybe, though, presentists should make this move: Timelessness is just presentness in the absence of anything past or future. In that case, 1 may be false. Timelessness is no longer an intrinsic characteristic of a being, and there could be worlds where all there is is a present. However, it seems to me that it is essential to a present to be evanescent. But timelessness is opposed to evanescence. On this analysis of timelessness, some instantaneous event would be timeless if nothing came before it and after it. But surely that would make it no less evanescent.
So, perhaps, presentists should deny 2. But, the following seems quite possible: there is a time than which there is no earlier. It is also imaginable that there is a time than which there is no later. And there is no reason why you shouldn't be able to combine the two, and have a time than which there is no earlier or later. In such a world, there would still be a time—a single present—but there would be no past or future, no flow of time. Everything in such a world would be maximally evanescent, if there were no timeless beings. But, plausibly, neither God nor Platonic abstracta could be maximally evanescent.
Talking of God brings us to another argument, or, actually, a pair of arguments (it's up to you which version you find more plausible):
- (Premise) Possibly, time has a beginning (respectively, an ending).
- (Premise) God can have no beginning (an ending).
- (Premise) God exists necessarily.
- (Premise) If presentism is true in a world, everything in that world is a temporal being.
- (Premise) If there is a world where time has a beginning (ending) and if presentism is actually true, there is a world where time has a beginning (ending) and presentism is true.
- (Premise) In a world where time has a beginning (an ending), every temporal being has a beginning (an ending).
- If presentism is true, possibly God has a beginning (an ending). (8, 10, 11, 12)
- Presentism is not true. (9, 14)