Which Christian apologetics book did C.S. Lewis publish in 1952?

C.S. Lewis published Mere Christianity in 1952. The book developed ideas first presented in radio broadcasts made for the BBC during the Second World War.

Lewis organized the work around arguments about morality, Christian belief, and the person of Jesus Christ. He did not intend it as a detailed defense of one denomination; instead, he presented what he considered the shared core of traditional Christian belief. The title refers to this common ground.

The book grew from three earlier broadcast series: The Case for Christianity, Christian Behaviour, and Beyond Personality. Lewis revised the talks for print, and the resulting volume became one of his most widely read works of Christian apologetics. It is often confused with The Problem of Pain, another major theological work by Lewis, but that book appeared in 1940.