C.S. Lewis gave the BBC radio talks later collected as Mere Christianity between 1941 and 1944.
The broadcasts were delivered during the Second World War, when radio reached a large British audience. Lewis was asked to explain and defend basic Christian beliefs in language accessible to listeners who were not specialists in theology. The talks were later revised and assembled into book form rather than simply reproduced as broadcast scripts.
Mere Christianity is organized around common Christian beliefs rather than the distinctive doctrines of one denomination. Its title refers to what Lewis regarded as the central, shared core of Christianity. The book is often mistaken for a single speech or a novel, but it developed from a sequence of wartime radio talks, followed by additional broadcast material and editorial shaping.