What was the title of C.S. Lewis’s book based on his wartime BBC radio broadcasts?

Mere Christianity is the book based on C.S. Lewis’s wartime BBC radio broadcasts.

Lewis delivered the original broadcasts between 1941 and 1944, when Britain was at war. The talks were intended to explain central Christian ideas to a broad audience rather than present the distinctive doctrines of one denomination.

The material was later revised and collected in book form. Mere Christianity discusses morality, belief, repentance, Christian virtues, and the doctrine of the Trinity in accessible language. Its title refers to what Lewis regarded as shared Christianity rather than a particular church tradition.

The book is sometimes confused with The Problem of Pain, another major apologetic work by Lewis. The Problem of Pain examines suffering and divine goodness, while Mere Christianity grew directly out of the BBC broadcasts.