Which C.S. Lewis book adapts BBC radio talks into an introduction to Christian belief?

Mere Christianity adapts C.S. Lewis’s BBC radio talks into an introduction to Christian belief.

The book grew out of radio broadcasts Lewis gave during the Second World War. The talks were delivered between 1941 and 1944 and were intended to explain basic Christian ideas to a broad audience. Lewis later revised and combined the material into book form, with Mere Christianity appearing in 1952.

The work does not attempt to present the distinctive doctrines of one denomination. Instead, Lewis argues for what he calls “mere Christianity,” meaning the shared core of belief held across historic Christian traditions. Its sections discuss morality, belief, Christian conduct, and the doctrine of the Trinity.

The title can be confused with other Lewis apologetic works, including The Problem of Pain and Miracles. Unlike those books, Mere Christianity is especially associated with the wartime broadcasts and with Lewis’s effort to address listeners who may not have had formal theological training.