What is the title of C.S. Lewis’s book based on broadcasts given during World War II?

Mere Christianity is C.S. Lewis’s book based on radio broadcasts given during World War II.

The broadcasts were delivered by Lewis for the BBC between 1941 and 1944. They aimed to explain and defend central Christian beliefs in language that ordinary listeners could understand, rather than presenting a detailed account of one denomination’s distinctive teachings.

Lewis revised the broadcast scripts for publication. The material first appeared in parts under titles including The Case for Christianity, Christian Behaviour, and Beyond Personality. These sections were later brought together as Mere Christianity, a title that refers to the shared core of historic Christian belief.

The book is not a transcript of a single wartime lecture. It is a shaped collection that developed from several series of talks and subsequent revisions. Its opening discussion of morality, often called the “Law of Nature” argument, and its treatment of Christian virtues helped make the work one of Lewis’s most widely read apologetic books.