- On a sunny day, I can see that the sun exists.
- If presentism is true, even on a sunny day I can't see that the sun exists.
- So presentism is false.
The eternalist isn't completely off the hook, either. For surely it is not just a part of the content of my experience that the sun exists simpliciter, but also that the sun exists now. But by the above argument, I don't see that the sun exists now. The eternalist is, however, in slightly better shape than the presentist, as the eternalist can say that some of the content of my perception is correct: I veridically see the sun's existing, but misperceive that existing as being present as well.
The formulation above in terms of existence is a bit awkward verbally. I think I can probably run the same argument with the sun's shining. On a sunny day, I can see the sun's shining. Not so if presentism is true. For the event of the sun's shining that I see, assuming I do see it, would be an event that occurred eight minutes ago, and hence a nonexistent event according to presentism. No one sees the nonexistent (they only apparently see it). So if presentism is true, I can't see the sun's shining.
Again, the eternalist isn't entirely off the hook. For intuitively I not only see the sun's shining, but I also see the sun's present shining. So I have to say that there is some illusion here: I do see the sun's shining, but my experience mistakenly attributes presentness to that event.