C.S. Lewis’s wartime radio talk series was called Broadcast Talks.
The BBC broadcast Lewis’s talks during the Second World War, beginning in 1941. He was invited to explain Christian belief to a broad public audience, and the talks were deliberately written in accessible language rather than as technical theology. Their radio format helped make Lewis a widely known public religious speaker.
The talks were issued in revised book form in stages. Christian Behaviour appeared in 1943, and Beyond Personality followed in 1944. These volumes, together with the first collection, were eventually revised and combined as Mere Christianity, a title that became much more famous than the original broadcast name.
Mere Christianity does not present the full teaching of one denomination. Lewis aimed to describe what he regarded as shared or central Christian belief. Readers sometimes call the original broadcasts Mere Christianity, but Broadcast Talks is the specific early title associated with the first collection.