Which C.S. Lewis book collects his wartime radio talks on basic Christian beliefs?

C.S. Lewis’s book collecting his wartime radio talks on basic Christian beliefs is Mere Christianity.

Mere Christianity grew from a series of BBC radio broadcasts Lewis gave during the Second World War. The talks were delivered between 1941 and 1944 and aimed to explain beliefs shared by many Christian traditions rather than defend one denomination’s distinctive doctrines.

The material was later revised and published in separate parts: The Case for Christianity in 1943, Christian Behaviour in 1943, and Beyond Personality in 1944. These sections were combined as Mere Christianity in 1952. The final book is organized into four parts, including Lewis’s discussion of morality, Christian belief, and the theological virtues.

The title does not mean a vague or minimal religion. Lewis used “mere Christianity” for the common core of historical Christian belief. The book is therefore distinct from the original broadcast titles, although those broadcasts supplied its foundation.