Which C.S. Lewis book adapts lectures first broadcast by the BBC during World War II?

Mere Christianity adapts lectures that C.S. Lewis first broadcast on the BBC during World War II.

The broadcasts began in 1941, when Lewis was invited to speak about Christian belief to a wide radio audience. He delivered several series of talks, including “The Case for Christianity,” “Christian Behaviour,” and “Beyond Personality.” The material was later revised and collected as Mere Christianity, first published in book form in 1952.

Lewis aimed to explain what he regarded as shared or “mere” Christian beliefs rather than defend one denomination. The title therefore refers to common ground among historic Christian traditions. Major themes include moral law, human nature, virtue, and the relationship between Christian doctrine and everyday conduct.

The book is not a transcript of a single uninterrupted lecture. It combines revised broadcast material from different periods and was organized into four books in its collected form. Its radio origin helped Lewis reach listeners who would not normally read academic theology, contributing substantially to his reputation as a public Christian writer.