Which C.S. Lewis book argues that Christianity is a form of ‘mere’ or essential belief?

Mere Christianity is the C.S. Lewis book that presents Christianity as a shared core of essential belief.

The book developed from radio talks Lewis gave for the BBC during the Second World War. The talks were broadcast between 1941 and 1944, and Lewis later revised and combined them into a book published in 1952.

Lewis uses “mere Christianity” to mean the common beliefs held across historic Christian traditions, rather than the distinctive practices of one denomination. The book discusses morality, human nature, Christian doctrine, and the figure of Jesus Christ.

The title does not mean Christianity is trivial or merely minimal. Instead, Lewis uses “mere” in the older sense of the basic or shared substance of a subject. The work remains one of his most widely read nonfiction books and helped establish his public reputation as a Christian apologist.