Which C.S. Lewis book originated from radio broadcasts during World War II?

Mere Christianity originated from C.S. Lewis’s radio broadcasts during World War II.

The BBC invited Lewis to give a series of talks about Christian belief during the Second World War. The broadcasts aired between 1941 and 1944, and Lewis later revised and collected them as Mere Christianity. The book presents a broad defense of shared Christian ideas rather than a detailed explanation of one denomination’s distinctive doctrines.

Lewis organized the material around moral law, Christian beliefs, and Christian behavior. His goal was to explain what he called “mere Christianity,” meaning the common ground historically shared by major Christian traditions. The work became one of his best-known apologetic books.

The title can be confused with The Problem of Pain, which was published in 1940 and was not based on the wartime broadcasts. Mere Christianity also differs from The Case for Christianity, which collected earlier broadcast material before the final expanded book appeared. Its radio origin helped make Lewis’s ideas accessible to a large general audience.