What Christian book by C.S. Lewis developed from wartime radio broadcasts?

Mere Christianity developed from C.S. Lewis’s wartime radio broadcasts.

The talks that became Mere Christianity were broadcast by the BBC during the Second World War, beginning in 1941. Lewis was invited to explain Christian belief to a general audience, and his clear, conversational style made the broadcasts popular. The material was later revised and published in book form in 1952.

The book is arranged in three main parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” and “Christian Behaviour.” A later section, “Beyond Personality,” discusses Christian ideas about the Trinity and spiritual life. Lewis aimed to present beliefs shared across major Christian traditions rather than defend one denomination.

Mere Christianity is not a novel, autobiography, or collection of the Narnia stories. It is also different from Christian Behaviour, which was one of the earlier broadcast-based volumes incorporated into the final work.