But though eternal life is regarded as necessary to give it meaning, it isn't sufficient: an eternity in Hell, after all, isn't a worthwhile existence. Or, as another Christian philosopher, J. P. Moreland, puts it in Scaling the Secular City, “Bestowing eternity on an empty life does not make it meaningful. It may yield only an eternity of emptiness.” According to these theists, then, in addition to everlasting life, there must be a God in order for life to have value. As Craig says, “if man and the universe could exist forever, but if there were no God, their existence would still have no ultimate significance.”
There are quite a few problems with all of these claims. For instance, why is the universe “inevitably doomed to death” if there is no God? Maybe it is, maybe it isn't, but the nonexistence of God certainly doesn't guarantee such a thing. And humanity – or at least some intelligent life forms – may also, for all we know, persist indefinitely.
It is far more certain that individual lives come to an end, though again this doesn't follow from the mere fact of God's nonexistence. But does the fact that life ends – assuming it is a fact – make it pointless? Does it follow in that case that our existence here and now should be of no importance to us?
To answer this, suppose that you've just arrived in Heaven, and are told that you have all of eternity ahead of you to do as you like. Now, I'm not denying that that would be a good thing (though some atheists do deny that endless existence would be good). But if your heavenly existence is worthwhile, that can only be because the individual spans of time you spend there are themselves worthwhile. In other words, in order for your never-ending afterlife to be a good thing, the finite spans that it is made up of must be good, at least on the whole. Note that both Craig and Moreland admit as much. But now, if the finite spans are good – if they are something you value – then they are that in themselves, even if there isn't an unlimited number of them. In order for an experience to be valuable, it is not necessary for there to be an unlimited number of additional valuable experiences as well.
As to how God makes life meaningful, that isn't entirely clear. Moreland has more to say about this than Craig, yet the only thing he actually claims is that “the value and purpose of life... are grounded in God's nature” – whatever that means.
What theists seem to have in mind is that God had a reason for creating the world as he did, a plan for it and for us – and that this somehow gives meaning to our existence. But first, why is it the case that if God has some purpose in mind, that makes my life meaningful for me? After all, what if I don't care about his purpose? (For example, what if his purpose is to have his creatures end up in Heaven singing his praises for all eternity? Maybe I'd rather not do that – or rather, I definitely would rather not do that.) Second, and more important, even if God has some plan or purpose in mind, what makes that something of ultimate significance? Of course at this point the theist is just going to say that this is God we're talking about, after all, so his purposes are by definition ultimate. But why should anyone agree with such a definition? If my plans and purposes, according to theism, are of no significance in themselves, what makes God's any different? Is it just because he's really powerful? Why should that matter?
If Craig and Moreland's arguments about a lack of ultimate significance make any sense at all, then they make sense even if there is a God. God may desire this or that, but so what? Ultimately, what's the point even if God really desires it? Would it actually have made any difference if nothing, including God, had ever existed?
Reasonable Faith, pp. 71-73
Scaling the Secular City , p. 130