Which C.S. Lewis book collects his 1941 BBC talks later known as Mere Christianity?

Mere Christianity is the C.S. Lewis book that collects and develops material from his wartime BBC broadcasts. The broadcasts were delivered between 1941 and 1944 and were intended to explain basic Christian beliefs to a broad radio audience.

Lewis first presented the material in three broadcast series. The first was published as The Case for Christianity, the second as Christian Behaviour, and the third as Beyond Personality. These parts were later revised and combined as Mere Christianity, which appeared in book form in 1952.

The word “mere” refers to what Lewis regarded as common or central Christianity shared across major historic traditions. He was not trying to create a new denomination. The book discusses morality, Christian belief, and the figure of Christ in a conversational style shaped by radio presentation.

The broadcasts made Lewis a prominent public religious voice in Britain during the Second World War. Mere Christianity is therefore not the title of the original 1941 broadcast series, but of the later consolidated book.