What was the name of the Christian radio-talk book based on C.S. Lewis’s BBC broadcasts?

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

Lewis delivered the talks during the Second World War, beginning in 1941, and later revised and collected them in book form. Mere Christianity presents a case for shared foundational Christian beliefs rather than defending one particular denomination. Its chapters discuss morality, belief, Christian conduct, and the doctrine of the Trinity.

The work became one of Lewis’s best-known books of Christian apologetics. Its title uses “mere” in the sense of basic or common Christianity: the central beliefs held across many historic Christian traditions. Lewis was an Anglican, but the book was intended for a broad audience.

The talks were not originally broadcast as one single book. They appeared in stages under titles including Broadcast Talks and Christian Behaviour before being brought together with a third section as Mere Christianity. This publishing history explains why the book is often described as both a radio-talk series and a later collection.