What was C.S. Lewis’s wartime radio-talk series later published as Mere Christianity?

C.S. Lewis’s Mere Christianity began as a series of broadcast talks. The BBC asked Lewis to explain and defend basic Christian beliefs for a general wartime audience, and the talks were broadcast during the early 1940s.

Lewis delivered the material in several groups of broadcasts, including The Case for Christianity, Christian Behaviour, and Beyond Personality. He revised the talks for publication, and the resulting book, Mere Christianity, appeared in assembled form in 1952. Its purpose was to present what Lewis regarded as common ground among historic Christian traditions rather than to argue for one denomination.

The work is sometimes described as a set of sermons, but the broadcasts were aimed at radio listeners and used conversational, accessible language. The BBC broadcasts made Lewis widely known beyond academic and literary circles. They also helped establish the apologetic style associated with his later nonfiction, including arguments about morality, reason, and Christian belief.