What title did C.S. Lewis give his BBC radio talks later collected as a book?

C.S. Lewis gave the BBC radio talks later collected under the title Mere Christianity.

The broadcasts were delivered during the Second World War, beginning in 1941, and were intended for a broad public audience rather than an academic one. Lewis explained basic Christian beliefs through clear arguments, illustrations, and familiar moral experiences.

The talks were issued in stages as books, including Broadcast Talks and Christian Behaviour, before being revised and combined as Mere Christianity in 1952. The final title refers to the shared core of historic Christian belief rather than to one particular denomination.

Readers sometimes assume that Mere Christianity began as a single manuscript written for publication. It instead developed from spoken broadcasts and later editorial revision. The work became one of Lewis’s best-known apologetic books and helped establish his public reputation as a communicator of Christian ideas.