Theists always ask of atheists: “But what happens to you after you die?” Of course, this begs the question at issue—assuming that any “you” persists after death to act as subject for some “happen[ing].” For atheists, death is precisely that condition where the “you” ceases to be, permanently and in every sense.
But the question is also a challenge: It carries the implication that atheists should be horrified to think that nothing happens, that is, that they might not exist in the future. This forms the basis of a kind of reductio ad absurdum argument that any view with such horrifying conclusions can only be false (and believed only in bad faith or insincerely).
Putting aside the point that there are plenty of horrifying facts, and everyone believes in some, three lines of response are in order:
(1) It appears theists are concerned that their lifespans should be anything less than infinite. But postulating a theist heaven doesn’t solve this problem. For an infinite number of years will not be realized in a heavenly tenure; the actual number of years endured will always be concrete, and numerable. So the concern could only be that one’s soul face an infinite number of years. But why should “infinity” be privileged in only one direction of time’s arrow? The time after my earthly life is just one part of the story. The years stretching before my earthly life are either infinite in number, or, if finite, could have, logically speaking, been infinite (as under different conditions my hazel eyes could have been blue). That is, there are either an infinity of actual, realized years, or an unrealized potential infinity of years, in which I will never [have] exist[ed]. Either way, “in back of” me, no less than “in front of” me, there spans an unrealized infinity of moments in which I can never exist. This condition is every bit as horrifying as the “unrealized infinity of moments in which I can never exist” presented by the lack of an afterlife.
Aside from this exercise, the bottom line: That I won’t exist 5,000 years from now should be no more horrifying than that I didn’t exist for the 5,000 (or gazillion) years preceding my birth.
(2) The ‘self’ which is extinguished in death is, metaphysically speaking, no more than a collection of experiences. In this sense, a new ‘self’ is created every moment as the flux of experience marches on. But this means an old self is lost every moment. Of course, the loss may not be permanent—these past selves can be conjured up, or “re-experienced,” in memory. But these memories aren’t precisely identical to the originals, and as time passes, the great majority of the experiences that have ever “made me” are forgotten, never to be recalled. “Death,” then, is at best a more “absolute”1 condition of this same process of self-loss (or, awkwardly, selves-loss) which has been unfolding since the dawn of my consciousness. Anyone’s life is made up of many such “deaths”; the last one is not somehow more horrifying than the thousands before it.
(3) Finally, the reductio can be flipped on the theists. In the words of process theologian Charles Hartshorne (an ironic resource for atheists in that his work offers a crackerjack critique of the most common forms of theism):
If what really matters is achieving, or being granted, heaven, and escaping hell, even nuclear warfare may seem not our major concern. Dying soon or late is after all a very minor matter, compared to life everlasting, either in very happy or more or less unhappy circumstances.
Moreover, unlike the theist’s reductio, this one “sticks”: For while few theists are horrified at the absence of an afterlife, every theist behaves as though the human course of life—how it is spent, whether it is enjoyed—is very important, while his theism, per the quote, implies the very opposite. This marks a contradiction which can only be remedied by acting as though one’s life is unimportant—which is probably impossible—or effectively giving up theism.
1 “Absolute” is not an ideal wording. Death means that no more ‘selves’ will be produced in the same “train” of selves. But insofar as any single one of these selves “dies” in death—that is, the final one in the train—this kind of thing, again, has been going on since our first conscious moment, that is, since we began to have ‘selves’ at all.