C.S. Lewis began the BBC radio broadcasts later adapted as Mere Christianity in 1941. The talks were addressed to a broad wartime British audience rather than a specialist academic readership.
Lewis was invited to explain Christian belief in accessible language. The broadcasts were delivered in several series between 1941 and 1944, and their success led to printed collections. Mere Christianity, published in book form in 1952, brought together revised versions of this material.
The title is often treated as if it were the name of the original radio program, but it became the title of the collected book. Lewis did not present a detailed account of one denomination; he aimed to describe shared Christian beliefs. The broadcasts helped establish his reputation as a major popular Christian writer.