Which C.S. Lewis work is based on a series of BBC radio talks broadcast during World War II?

Mere Christianity is based on a series of BBC radio talks broadcast during World War II.

Lewis delivered the talks between 1941 and 1944, initially speaking to a British audience during wartime. He aimed to explain ideas shared across major Christian traditions rather than defend the distinctive doctrines of one denomination. The broadcasts were later revised, assembled, and published in book form as Mere Christianity.

The work is arranged around themes including moral law, Christian belief, and the virtues. Lewis’s radio voice and conversational style helped make the material accessible to listeners who might not have encountered academic theology. The book became one of his most widely read works of Christian apologetics.

The broadcasts should not be confused with The Case for Christianity, Christian Behaviour, or Beyond Personality, which were related publications that contributed to the eventual book. Mere Christianity is the title of the collected and revised argument, not the original name of every broadcast series.