Which C.S. Lewis book developed from his BBC radio broadcasts?

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

Lewis delivered a series of talks during the Second World War, beginning in 1941, to explain and defend basic Christian beliefs for a general audience. The talks were later revised and collected in book form as Mere Christianity, first published in 1952.

The title refers to the shared core of belief that Lewis saw across the main historic Christian traditions. The book is organized around themes including morality, Christian belief, and the meaning of Christian conduct. It was not written as a technical academic treatise, which helped make it one of Lewis’s most widely read works.

The Problem of Pain, The Abolition of Man, and Miracles were also important Lewis books, but they did not originate as the same BBC broadcast series. Mere Christianity remains especially associated with radio communication because its first audience heard Lewis speaking directly through wartime broadcasts.