What Christian book by C.S. Lewis grew from his BBC radio broadcasts?

Mere Christianity grew from C.S. Lewis’s BBC radio broadcasts.

Lewis delivered the broadcasts during the Second World War, beginning in 1941. The talks were aimed at a general audience rather than an academic one and explained shared Christian beliefs in accessible language. They were later revised and collected into the book Mere Christianity, first published in 1952.

The title refers to what Lewis regarded as the central beliefs common to historic Christianity, rather than to one denomination. The book discusses morality, belief, Christian doctrine, and the meaning of conversion. Its conversational style helped make it one of Lewis’s most widely read works of Christian apologetics.

The broadcasts were not originally delivered as a single book. Their radio format shaped Lewis’s use of examples, clear definitions, and direct explanation. The book’s structure reflects the process of revising those talks for print.