What was C.S. Lewis’s first published work of Christian apologetics?

C.S. Lewis’s first published work of Christian apologetics was The Problem of Pain. The book appeared in 1940 and examines why suffering exists if God is both good and omnipotent.

Lewis discusses divine goodness, human freedom, sin, hell, and animal pain. It was written as a reasoned defense of Christian belief rather than as a personal autobiography. The work helped establish him as a prominent Christian public intellectual during the Second World War.

The Problem of Pain is often confused with Mere Christianity, another major apologetic work by Lewis. Mere Christianity developed from wartime radio talks and was published in book form in 1952. The Problem of Pain, by contrast, began as a single authored study of suffering.