Which C.S. Lewis book collects his 1940s BBC broadcasts about Christian belief?

Mere Christianity collects C.S. Lewis’s 1940s BBC broadcasts about Christian belief. The book presents arguments and explanations intended for a broad audience rather than a specialist theological readership.

Lewis originally delivered broadcast talks during the Second World War. He later revised and expanded them into the published work, which is arranged in four sections: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.”

The title refers to the shared core of traditional Christian belief, not to a separate denomination. Lewis did not write the broadcasts as a complete treatment of every Christian doctrine. Readers also sometimes confuse Mere Christianity with The Problem of Pain, another apologetic work, but the two books had different origins and emphases.