It is generally supposed that the fact that the world contains a vast amount of suffering, much of it truly horrible suffering, confronts those who believe in an all-powerful and benevolent Creator with a serious problem: to explain why such a Creator would permit this. Many reflective people are convinced that the problem, the problem of evil, is insoluble. The reasons that underlie this conviction can be formulated as a powerful argument for the non-existence of God, the so-called argument from evil: If there were a God, he would not permit the existence of vast amounts of truly horrible suffering; since such suffering exists, there is no God. Peter van Inwagen examines this argument, which he regards as a paradigmatically philosophical argument. His conclusion is that (like most philosophical arguments) it is a failure. He seeks to demonstrate, not that God exists, but the fact that the world contains a vast amount of suffering does not show that God does not exist. Along the way he discusses a wide range of topics of interest to philosophers and theologians, such as: the concept of God; what might be meant by describing a philosophical argument as a failure; the distinction between versions of the argument from evil that depend on the vast amount of evil in the world and versions of the argument that depend on a particular evil, such as the Lisbon earthquake or the death of a fawn in a forest fire; the free-will defense; animal suffering; and the problem of the hiddenness of God.