Which C.S. Lewis book developed talks first broadcast by the BBC during World War II?

Mere Christianity developed from C.S. Lewis’s BBC radio talks broadcast during World War II.

The talks were delivered between 1941 and 1944, when Lewis addressed listeners in Britain about basic Christian beliefs. He later revised and expanded the material into a book published in 1952. The title refers to the shared core of Christian doctrine rather than to one particular denomination.

Lewis organized the work around moral law, Christian belief, and the practical meaning of Christian conduct. Its accessible broadcast style helped make complex theological ideas understandable to a wide audience. The book became one of his most influential works of Christian apologetics.

The radio talks were not originally broadcast under the complete book title in the same form. They appeared in stages under titles including Broadcast Talks and Christian Behaviour before the material was collected and revised as Mere Christianity.