Which C.S. Lewis book grew out of his BBC radio talks broadcast during World War II?

Mere Christianity grew out of C.S. Lewis’s BBC radio talks broadcast during World War II. The talks were delivered between 1941 and 1944 and later revised into book form.

Lewis aimed to explain central Christian beliefs in language accessible to a broad British radio audience. He organized the material around shared Christian ideas rather than the distinctive doctrines of one denomination, which helped the work reach readers across several traditions.

The finished book was published in 1952. It is sometimes mistaken for a transcript of a single broadcast series, but the published text combines and reshapes material from multiple wartime talks. Lewis’s “trilemma” discussion about Jesus—Lord, liar, or lunatic—became one of the book’s most frequently quoted sections.