Which C.S. Lewis book developed from his 1940s BBC radio broadcasts about Christianity?

Mere Christianity developed from C.S. Lewis’s BBC radio broadcasts about Christianity in the 1940s. The talks were later revised and collected into the book published in stages between 1943 and 1952.

Lewis designed the broadcasts to explain shared Christian ideas in language accessible to listeners during the Second World War. He aimed to discuss the common core of Christian belief rather than defend one denomination’s distinctive doctrines.

The final book is divided into sections commonly titled Right and Wrong as a Clue to the Meaning of the Universe, What Christians Believe, Christian Behaviour, and Beyond Personality. Its arguments cover morality, belief, virtue, and the Christian understanding of God and Christ.

Mere Christianity is sometimes mistaken for a transcript of one uninterrupted radio series. It is better understood as a revised book based on multiple broadcast series, with Lewis reshaping the spoken material for print.