Which 1943 book by C.S. Lewis collects his wartime radio talks on Christianity?

Mere Christianity collects C.S. Lewis’s wartime radio talks on Christianity.

The talks were broadcast by the BBC during World War II, beginning in 1941. Lewis presented arguments about morality, Christian belief, and the meaning of the faith in language intended for a broad audience rather than only clergy or academics.

The broadcasts were later revised and published in book form. The first section appeared as Broadcast Talks in 1942, followed by Christian Behaviour in 1943. These materials were brought together in Mere Christianity, published in 1952. The book’s title refers to the shared core of historic Christian belief, not to a separate denomination.

The work is often confused with The Problem of Pain, Lewis’s 1940 book about suffering and theology. Mere Christianity is also not a transcript of every broadcast exactly as aired; Lewis revised the talks for publication and organized them into a more systematic presentation.