Under what title were C.S. Lewis’s BBC radio talks later published as a book?

C.S. Lewis’s BBC radio talks were later published as Mere Christianity.

Lewis gave the talks during the Second World War, beginning in 1941, for BBC radio listeners in Britain. They were designed to explain basic Christian beliefs in accessible language rather than to present the distinctive doctrines of one denomination. The broadcasts made Lewis widely known beyond his academic and literary circles.

The talks were first published in separate collections: Broadcast Talks in 1942, Christian Behaviour in 1943, and Beyond Personality in 1944. Lewis later revised and combined this material, and the resulting book was published under the title Mere Christianity in 1952.

The title refers to the shared core of historic Christian belief. It does not mean that Lewis considered every Christian teaching unimportant; instead, he focused on doctrines he believed were held across major traditions. The work is therefore different from The Problem of Pain, which addresses suffering, and Miracles, which concentrates on the supernatural.