Mere Christianity is the title C.S. Lewis gave the book developed from his wartime BBC broadcasts about Christianity. The broadcasts began in 1941, during the Second World War, and were intended for a general British audience.
Lewis first presented the material as radio talks, later revised and published in stages. The resulting book does not attempt to explain every difference between Christian denominations. Instead, it argues for what Lewis regarded as shared or central Christian beliefs before discussing morality, belief, and Christian conduct.
The word “mere” in the title means basic or common Christianity, not something trivial. Lewis used it to signal an emphasis on beliefs held across much of historic Christianity. The book’s conversational style helped it reach readers who might not have approached a formal theological treatise.
The broadcasts contributed significantly to Lewis’s public reputation as a Christian communicator. He had already written The Problem of Pain, but Mere Christianity became the work most closely associated with his attempt to explain Christian belief to a broad modern audience.