Which C.S. Lewis book presents Christian ideas through radio broadcasts?

Mere Christianity presents Christian ideas through material that began as radio broadcasts by C.S. Lewis during the Second World War. The talks were delivered for the BBC between 1941 and 1944 and later revised and collected as a book.

Lewis designed the broadcasts for a general audience rather than for specialists in theology. He discussed morality, belief, Christian doctrine, and the relationship between different Christian traditions. The title refers to what Lewis regarded as common or shared Christianity, rather than to one particular denomination.

The book is arranged in four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behavior,” and “Beyond Personality.” These sections preserve the accessible, spoken style of the original broadcasts while expanding their arguments.

Mere Christianity is sometimes confused with The Problem of Pain, another major apologetic work by Lewis. The latter focuses especially on suffering and the problem of evil, whereas Mere Christianity grew directly from his wartime radio talks.