Do we live in a world that was created by a god who is all-powerful, all-knowing, and all good? Christians think we do. Yet a powerful reason for doubting this confronts us every day: the world contains a vast amount of pain and suffering. If God is all-knowing, he knows how much suffering there is. If he is all-powerful, he could have created a world without so much of it - and he would have done so if he were all good.

Christians usually respond that God bestowed on us the gift of free will, and hence is not responsible for the evil we do. But this reply fails to deal with the suffering of those who drown in floods, are burned alive in forest fires caused by lightning, or die of hunger or thirst during a drought.

Christians sometimes attempt to explain this suffering by saying that all humans are sinners, and so deserve their fate, even if it is a horrible one. But infants and small children are just as likely to suffer and die in natural disasters as adults, and it seems impossible that they could deserve to suffer and die.

Once again, some Christians say that we have all inherited the original sin committed by Eve, who defied God's decree against eating from the tree of knowledge. This is a triply repellent idea, for it implies that knowledge is bad, disobeying God's will is the greatest sin of all, and children inherit the sins of their ancestors, and may justly be punished for them.

Even if were to accept all this, the problem remains unresolved. For animals also suffer from floods, fires, and droughts, and, since they are not descended from Adam and Eve, they cannot have inherited original sin.

In earlier times, when original sin was taken more seriously than it generally is today, the suffering of animals posed a particularly difficult problem for thoughtful Christians. The 17th-century French philosopher René Descartes solved it by the drastic expedient of denying that animals can suffer. Animals, he maintained, are merely ingenious mechanisms, and we should not take their cries and struggles as a sign of pain, any more than we take the sound of an alarm clock as a sign that it has consciousness.

People who live with a dog or a cat are not likely to find that persuasive. Last month, at Biola University, a Christian college in southern California, I debated the existence of God with the conservative commentator Dinesh D'Souza. In recent months, D'Souza has made a point of debating prominent atheists, but he, too, struggled to find a convincing answer to the problem I outlined above.

He first said that, because humans can live forever in heaven, the suffering of this world is less important than it would be if our life in this world were the only life we had. That still fails to explain why an all-powerful and all-good god would permit it. Relatively insignificant as this suffering may be from the perspective of eternity, the world would be better without it, or at least without most of it. (Some say that we need to have some suffering to appreciate what it is like to be happy. Maybe, but we surely don't need as much as we have.)

Next, D'Souza argued that since God gave us life, we are not in a position to complain if our life is not perfect. He used the example of a child born with one limb missing. If life itself is a gift, he said, we are not wronged by being given less than we might want. In response I pointed out that we condemn mothers who cause harm to their babies by using alcohol or cocaine when pregnant. Yet since they have given life to their children, it seems that, on D'Souza's view, there is nothing wrong with what they have done.

Finally, D'Souza fell back, as many Christians do when pressed, on the claim that we should not expect to understand God's reasons for creating the world as it is. It is as if an ant should try to understand our decisions, so puny is our intelligence in comparison with the infinite wisdom of God. (This is the answer given, in more poetic form, in The Book of Job.) But once we abdicate our powers of reason in this way, we may as well believe anything at all.

Moreover, the assertion that our intelligence is puny in comparison with God's presupposes just the point that is under debate - that there is a god who is all-knowing, all-powerful, and all good. The evidence of our own eyes makes it more plausible to believe that the world was not created by any god at all. If, however, we insist on believing in divine creation, we are forced to admit that the God who made the world cannot be all-powerful and all good. He must be either evil or a bungler.

In cooperation with Project Syndicate, 2008.