The central question of The Problem of Pain is why Christians believers suffer if their God is a good and benevolent God. Lewis goes to great lengths to examine the nature of suffering—its sterility (meaning its absence of lingering aftereffects), its role in teaching us empathy, how we cause pain on one another (as a result of the free will we have been granted by God), and how some suffering comes to those who, outwardly, seem not to deserve any suffering at all.

All suffering, and thus pain, Lewis argues, has a purpose that God has ordained. One purpose of pain is to remind us that we are only human, and only God is, or could be, omniscient (all-knowing) and omnipotent (all-powerful). This is the lesson of the doctrine of the Fall, in which Adam, the first human, chooses to be disobedient to God and eats fruit from the tree of knowledge of good and evil. As a result of Adam’s choice, all humans are separated from God, but both God and humans desire to be reinstated in close union once more.

Therefore, God sends us pain (as well as moments of joy and happiness, but these are temporary).