What was the title of C.S. Lewis’s book based on BBC radio talks from 1941 to 1944?

C.S. Lewis’s book based on BBC radio talks from 1941 to 1944 is Mere Christianity.

Mere Christianity developed from a series of BBC broadcasts Lewis delivered during the Second World War. The talks aimed to explain and defend basic Christian beliefs shared across many Christian traditions rather than promote one denomination. The material was later revised and published in book form.

The title refers to “mere Christianity,” Lewis’s term for the central beliefs held in common by historic Christian denominations. The book is arranged in four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.”

Some readers mistake it for a transcript of a single broadcast series, but the published work combines material from multiple wartime radio talks and later editorial revisions.