What was the original format of C.S. Lewis’s Mere Christianity?

Mere Christianity originated as BBC radio broadcasts by C.S. Lewis.

Lewis delivered the first series of talks in 1941, during the Second World War, and followed it with further broadcasts in 1942 and 1944. The talks were aimed at a broad British audience and presented basic Christian beliefs in accessible language rather than focusing on the doctrines of one denomination.

The broadcasts were later revised and collected into books. The resulting volume, Mere Christianity, became one of Lewis’s most widely read Christian apologetic works. Its title refers to what Lewis regarded as the central beliefs shared by the historic Christian traditions.

The book is therefore not originally a university lecture course, newspaper column, or stage work. Its radio origin matters because Lewis deliberately used a conversational style suited to listeners, helping explain why the prose remains direct and relatively approachable compared with some of his academic writing.