Which book by C.S. Lewis collected his BBC radio talks on Christian belief?

Mere Christianity collected C.S. Lewis’s BBC radio talks on Christian belief. The talks were broadcast in Britain between 1941 and 1944 and later revised into book form.

Lewis was invited to speak during the Second World War, when radio reached a broad audience facing national crisis. His broadcasts explained shared Christian ideas in accessible language rather than focusing on differences among denominations. The published work is organized into sections based on the broadcasts: Right and Wrong as a Clue to the Meaning of the Universe, What Christians Believe, Christian Behaviour, and Beyond Personality.

The title refers to the common core of Christian belief, not to a separate denomination. Lewis’s arguments about morality, the Trinity, and Christian conduct made the book one of his most influential works of apologetics.

The material was published in separate volumes before being combined as Mere Christianity in 1952. That publication history can cause confusion about whether the title describes the original broadcasts or the later collected book.