C.S. Lewis’s BBC broadcasts that became Mere Christianity began in 1941. The talks were delivered during the Second World War and introduced ordinary radio listeners to arguments about Christian belief and moral reasoning.
The broadcasts were not initially released as one complete book. Lewis’s talks were later revised and collected in stages, with The Case for Christianity appearing in 1943, Christian Behaviour in 1943, and Beyond Personality in 1944. These sections were eventually brought together as Mere Christianity.
The title refers to what Lewis regarded as the central beliefs shared across historic Christian traditions, rather than to the distinctive practices of one denomination. He used examples from everyday life, including moral disagreement, choices, and the image of a fleet of ships traveling together.
The wartime broadcasts made Lewis a national public figure. Their conversational style also helped distinguish him from the highly technical prose expected from an academic. The book remains one of his best-known works of Christian apologetics.