Which C.S. Lewis book grew out of his 1941–1944 BBC radio talks about Christianity?

Mere Christianity grew out of C.S. Lewis’s 1941–1944 BBC radio talks about Christianity.

The broadcasts were first delivered during the Second World War, when Lewis became widely known as a speaker as well as a writer. He aimed to explain shared Christian beliefs rather than defend one particular denomination.

The talks were later revised and collected in book form. Mere Christianity is divided into sections that discuss moral law, Christian belief, Christian behavior, and the idea of the Trinity. The title refers to the basic beliefs Lewis saw as common to the major Christian traditions.

It is sometimes mistaken for a transcript of a single uninterrupted radio series. In fact, the book developed from several broadcast series and was edited for publication. The work’s influence comes partly from its accessible style: Lewis used everyday examples and logical argument rather than writing as a technical theologian.