C.S. Lewis began broadcasting the talks that became Mere Christianity in 1941. The BBC invited him to give radio talks about Christian belief during the Second World War.
Lewis delivered the broadcasts in a direct, conversational style intended for a broad audience rather than a specialist theological readership. Additional series followed in 1942 and 1944. The talks were later revised and assembled in book form, with the title Mere Christianity referring to the shared core of belief Lewis believed united many Christian traditions.
The book is not a transcript of one uninterrupted 1941 series. It combines material from the wartime broadcasts and related talks, arranged into sections on right and wrong, Christian belief, and Christian behavior. Because the broadcasts were delivered over several years, 1941, 1942, and 1944 can all appear in accounts of the project; 1941 is the starting year.