What is the name of C.S. Lewis’s Christian apologetics book based on wartime radio talks?

Mere Christianity is C.S. Lewis’s apologetics book based on wartime radio talks.

The talks were broadcast by the BBC during the Second World War, beginning in 1941. Lewis presented arguments about morality, human nature, and Christian belief in language intended for a broad public audience rather than only for academics or theologians. The broadcasts were later revised and collected into books.

The title Mere Christianity refers to the basic beliefs shared across the historic Christian traditions, rather than to one denomination. Lewis organized the final work into three broad sections: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” and “Christian Behaviour.”

The book is often confused with The Problem of Pain because both are influential works of Lewis’s Christian writing. The Problem of Pain is a separate 1940 book focused especially on suffering and divine goodness. Mere Christianity grew directly out of the BBC talks and became one of Lewis’s best-known nonfiction works.