Just found this from Tim Keller, pastor at Redeemer Presbyterian in NYC. Though it’s long, it’s worth the read given the tragedy in Aurora, CO.
Horrendous, inexplicable suffering, though it cannot disprove God, is nonetheless a problem for the believer in the Bible. However, it is perhaps an even greater problem for nonbelievers. C. S. Lewis described how he had originally rejected the idea of God because of the cruelty of life. Then he came to realize that evil was even more problematic for his new atheism. In the end, he realized that suffering provided a better argument for God’s existence than one against it.

“My argument against God was that the universe seemed so cruel and unjust. But how had I got this idea of ‘just’ and ‘unjust’?…What was I comparing this universe with when I called it unjust?…Of course I could have given up my idea of justice by saying it was nothing but a private idea of my own. But if I did that, then my argument against God collapsed too–for the argument depended on saying that the world was really unjust, not simply that it did not happen to please my private fancies…Consequently atheism turns out to be too simple.”

Lewis recognized that modern objections to God are based on a sense of fair play and justice. People, we believe, ought not to suffer, be excluded, die of hunger or oppression. But the evolutionary mechanism of natural selection depends on death, destruction, and violence of the strong against the weak–these things are all perfectly natural. On what basis, then, does the atheist judge the natural world to be horribly wrong, unfair, and unjust? The nonbeliever in God doesn’t have a good basis for being outraged at injustice, which, as Lewis points out, was the reason for objecting to God in the first place. If you are sure that this natural world is unjust and filled with evil, you are assuming the reality of some extra-natural (or supernatural) standard by which to make your judgment. The philosopher Alvin Plantiga said it like this:

“Could there really be any such thing as horrifying wickedness [if there were no God and we just evolved]? I don’t see how. There can be such a thing only if there is a way that rational creatures are supposed to live, obliged to live…A [secular]way of looking at the world has no place for genuine moral obligation of any sort…and thus no way to say there is such a thing as genuine and wickedness. Accordingly, if you think there really is such a thing as horrifying wickedness (…and not just an illusion of some sort), then you have a powerful…argument [for the reality of God].”

In short, the problem of tragedy, suffering, and injustice is a problem for everyone. It is at least as big a problem for nonbelief in God as for belief. It is therefore a mistake, though an understandable one, to think that if you abandon belief in God it somehow makes the problem of evil easier to handle.

—Tim Keller from The Reason for God