Which book collected C.S. Lewis’s BBC broadcasts on Christianity?

Mere Christianity collected C.S. Lewis’s BBC broadcasts on Christianity. The broadcasts were delivered during the Second World War, beginning with radio talks in 1941, and were later revised and assembled into book form.

Lewis designed the talks to explain shared Christian ideas rather than defend one particular denomination. He discussed morality, belief in God, Christian doctrine, and the meaning of faith in language intended for a broad radio audience. The title refers to what Lewis regarded as the common core of Christianity.

The book is divided into four parts: Right and Wrong as a Clue to the Meaning of the Universe, What Christians Believe, Christian Behaviour, and Beyond Personality. The final part develops Lewis’s account of Christian doctrine and the Trinity.

Readers sometimes call Mere Christianity a single original book written from the start in that form. It was instead built from wartime broadcasts and earlier printed collections, then revised for publication. It became one of Lewis’s most widely read works of Christian apologetics.