The BBC radio talks that formed the basis of C.S. Lewis’s Mere Christianity were broadcast talks. Lewis delivered the series during the Second World War, and the material was later revised and collected into book form.
The original broadcasts were arranged in three series: “The Case for Christianity” in 1941, “Christian Behaviour” in 1942, and “Beyond Personality” in 1944. Lewis used accessible language to explain shared Christian beliefs rather than argue for a particular denomination.
The book Mere Christianity was published in 1952. Because the individual radio series had their own titles, “Mere Christianity” was not the original broadcast title. The phrase became the name of the later collection and is now strongly associated with Lewis’s attempt to describe what he considered the common core of historic Christianity.