Which BBC radio series became the basis for C.S. Lewis’s book Mere Christianity?

Broadcast talks became the basis for C.S. Lewis’s book Mere Christianity.

During World War II, C.S. Lewis delivered a series of short radio talks for the BBC. The talks were broadcast between 1941 and 1944 and explained basic Christian beliefs in language intended for a broad audience, including listeners serving in wartime Britain. Lewis was already known for his literary scholarship, but the broadcasts made him widely recognized as a Christian communicator.

The material was later revised and collected in book form. Mere Christianity was published in 1952, with sections developed from the earlier radio talks. The book discusses morality, Christian doctrine, and the meaning of faith without focusing on one denomination.

A frequent misunderstanding is that Mere Christianity was first written as a conventional book. Its origins were spoken broadcasts, and the conversational style reflects that beginning. The BBC talks also helped establish Lewis's reputation beyond universities and literary circles.