C.S. Lewis originally called his wartime radio talks Broadcast Talks. The talks were delivered for the BBC during the Second World War and later revised and collected in the book now known as Mere Christianity.
Lewis broadcast the first series in 1941, followed by further series in 1942 and 1944. The BBC broadcasts were intended for a broad British audience, so Lewis presented core Christian ideas in accessible language rather than arguing for one denomination. The talks helped make him a widely recognized public religious voice.
The later book title is better known than the original broadcast title, which can lead to confusion. Mere Christianity was published in book form in 1952 after the material had been revised and combined. The work presents what Lewis described as shared Christian beliefs, not a complete treatment of every theological disagreement.