Which C.S. Lewis book collects his World War II-era radio talks on Christianity?

C.S. Lewis’s World War II-era radio talks on Christianity were collected in Mere Christianity.

The book developed from a series of BBC radio broadcasts Lewis delivered between 1941 and 1944. The talks were aimed at a general audience rather than specialists, and they presented what Lewis called the common or “mere” beliefs shared by many Christian traditions. The broadcasts were later revised and assembled into book form, with the title Mere Christianity.

The work is organized into four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.” Lewis discusses morality, belief, virtue, free will, and the Christian understanding of God and Christ.

Mere Christianity is sometimes mistaken for a single wartime speech or for The Problem of Pain, which is a separate book published in 1940. Its broadcast origin explains its conversational style and its lasting reach among readers who encountered Lewis through radio before reading him in print.