Which C.S. Lewis book presents material adapted from his wartime radio talks?

Mere Christianity presents material adapted from C.S. Lewis’s wartime radio talks.

The book grew from a series of BBC broadcasts Lewis delivered between 1941 and 1944. The talks were intended to explain and defend basic Christian beliefs to a broad audience during the Second World War.

Lewis later revised and expanded the broadcast material into three sections: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” and “Christian Behaviour.” The title refers to what Lewis called the common or central Christian faith shared across many denominations.

The work is not a detailed treatment of every Christian doctrine. Instead, it is an accessible apologetic argument that moves from moral experience toward broader Christian claims. Its conversational origins helped give the book its direct tone and made it one of Lewis’s most influential nonfiction works.