Craig frames the problem of evil like so:
His contention is that (2) is the weak point of the argument. As Craig acknowledges "Everybody admits that the world is filled with apparently gratuitous suffering", but does Craig sufficiently deal with the problem? Here are his responses.
- If God exists, gratuitous evil does not exist.
- Gratuitous evil exists.
- Therefore, God does not exist.
1. We are not in a good position to assess with confidence the probability that God lacks morally sufficient reasons for permitting the suffering in the world."Once we contemplate God’s providence over the whole of history, then it becomes evident how hopeless it is for limited observers to speculate on the probability that some evil we see is ultimately gratuitous."
2. Christian theism entails doctrines that increase the probability of the coexistence of God and evil.
(i) The chief purpose of life is not happiness, but the knowledge of God."Many evils occur in life that may be utterly pointless with respect to producing human happiness; but they may not be pointless with respect to producing a deeper, saving knowledge of God."
(ii) Mankind has been accorded significant moral freedom to rebel against God and his purpose."The horrendous moral evils in the world are testimony to man’s depravity in this state of spiritual alienation from God."
(iii) God’s purpose spills over into eternal life."Given the prospect of eternal life, we should not expect to see in this life God’s compensation for every evil we experience. Some may be justified only in light of eternity."
(iv) The knowledge of God is an incommensurable good."[T]he person who knows God, no matter what he or she suffers, no matter how awful his or her pain, can still truly say, “God is good to me!” simply in virtue of the fact that he or she knows God."
3. There is better warrant for believing that God exists than that the evil in the world is really gratuitous."[I]f God exists, then the evil in the world is not really gratuitous."
I would wonder just how viable each of those options are. (1) is an concession to our ignorance on matters at all. If the objection held, then we'd just as equally be able to say that the evidence of an all-evil God or a morally-indifferent God is just as likely as an omnibenevolent God. So whatever other reasons one would have to believe that there's a divine power, we'd have no reason to favour just what nature that divine power embodies. Would believers be comfortable in accepting that the universe is just as easily made by a malevolent deity as an omnibenevolent one?
(2) is a curious strategy, not least because it immediately conjures up the Epicurean objection: "Is he able, but not willing? Then he is malevolent." Even if knowledge of God was an immesurable good, why would we need to have gratuitous suffering alongside it? If it doesn't matter, then it's powerful evidence against God's benevolence. One might be able to make the case iff suffering increased the likelihood of knowledge of God, but then that would require good evidence in its favour. Knowledge of the Christian God is largely based on the actions of Christian evangelism rather than by suffering directly. Most people throughout our species' history have suffered (sometimes gratuitously) without there even being the idea of Christianity, let alone the exposure to it. So the premises (2i), (2ii), and (2iv) don't even make sense for most of the suffering we have.
Furthermore, most life evidentially can suffer, and there's no question of a chimpanzee or an octopus having knowledge of God. Other animals react much the same to pain as we do, so why would a God allow them to suffer when none of the four responses even begin to address animal suffering? Craig's answer from elsewhere is "God has shielded almost the entire animal kingdom throughout its history from an awareness of being in pain!" Though almost doesn't include all animals beside from human, even if Craig is correct in interpreting the evidence as other great apes have the structures, yet don't have knowledge of God. So at best Craig has merely reduced the scope of animal suffering but not eliminated the problem.
The idea of heaven (2iii) seems to work against the notion of a benevolent God. Far from a saving grace, it highlights exactly what the problem of evil says - this world doesn't look like it was created by a benevolent God. If God could have created the world without gratuitous suffering, then why do we have gratuitous suffering? Also, why would a child need to die slowly and painfully of cancer before heaven rather than just getting into heaven without experiencing that suffering at all? Similarly, (2ii) asks the question of why a benevolent God would create us in such a depraved way. Quite a lot of atheists, for example, are quite civilised and don't contribute to the gratuitous suffering of our fellow humans. Their spiritual alienation from God doesn't lead to total depravity. Meanwhile there are believers who tortured others in the name of their faith. Did they have spiritual alienation? Besides, most suffering in the world has nothing to do with the actions of humanity - spiritually alienated or not.
For (3) to work, we would need to have greater confidence in the evidence for God's existence than the evidence for gratuitous suffering. Since we have very good evidence for gratuitous suffering such that Craig acknowledges the apparent gratuitous suffering, so it's setting a really high bar for evidence for God. It's not helped by the problem that other arguments for God, as Stephen Law points out, are neutral on the moral characteristics for God. So even if the other arguments are very persuasive, they wouldn't be evidence against the actual gratuitous suffering in the world. Perhaps a morally-indifferent God or an omnimalevolent God would be a better fit for the data. But even if we ignore that issue (perhaps God is necessarily omnibenevolent), that the morally-indifferent god or omnimalevolent god would be a better fit for the data would suggest that the evidence really doesn't favour God over the fact of gratuitous suffering.