C.S. Lewis began the BBC radio talks that became Mere Christianity in 1941. The broadcasts were delivered during the Second World War and were intended to explain basic Christian beliefs to a broad audience.
The talks were not originally released as one book. Lewis broadcast a series of talks between 1941 and 1944, and the material was later revised and collected into three sections: Christian Behaviour, Beyond Personality, and Right and Wrong as a Clue to the Meaning of the Universe.
The title Mere Christianity refers to the shared core of belief held across historic Christian traditions. Lewis did not present the broadcasts as a complete substitute for denominational teaching; instead, he aimed to discuss foundational ideas common to many churches.
The first broadcast year is sometimes confused with the year of book publication. Mere Christianity appeared in collected form in 1952, more than a decade after the initial BBC talks began.