Which C.S. Lewis book presents Christian ideas through conversations broadcast on British radio?

Mere Christianity presents C.S. Lewis’s Christian ideas through conversations first broadcast on British radio.

The material began as a series of BBC radio talks during the Second World War. Lewis aimed to explain basic Christian beliefs in accessible language to a broad audience rather than present a technical theological treatise.

The talks were later revised and published in book form. Mere Christianity is organized around themes including morality, Christian belief, and the nature of Christian conduct. Its title refers to the shared core of belief across major Christian traditions.

Readers sometimes treat the book as a transcript of untouched broadcasts, but Lewis revised the material for publication. The work is also distinct from The Problem of Pain, which examines suffering, and from Miracles, which argues for the possibility and significance of miracles.