Which C.S. Lewis book began as BBC radio broadcasts about Christian belief?

Mere Christianity began as BBC radio broadcasts about Christian belief. C.S. Lewis delivered the talks during the Second World War, and they were later revised and collected as a book.

The broadcasts were first transmitted in 1941, with additional series following in 1942 and 1944. Lewis spoke to a general audience rather than addressing only theologians. His aim was to explain ideas shared across major Christian traditions in accessible language.

The talks were published in stages under titles including Broadcast Talks and Christian Behaviour. The material was eventually combined and revised as Mere Christianity, whose first complete book edition appeared in 1952. Its title refers to the common or central beliefs Lewis believed united Christians.

The work became one of Lewis’s most influential apologetic books. Its “trilemma” discussion of Jesus and its treatment of morality, pride, and Christian conduct are frequently quoted, although readers sometimes overlook that the text originated in wartime radio talks rather than as a single manuscript.