Which 1943 C.S. Lewis book presents Christianity through broadcast talks?

Mere Christianity presents C.S. Lewis’s Christian ideas through material originally delivered as broadcast talks.

The talks were made for the BBC during the Second World War, beginning in 1941. Lewis aimed to explain what he saw as the shared core of Christian belief rather than defend one particular denomination.

The resulting book was published in 1952 after the broadcast material had been revised and expanded. It is arranged in four parts: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” “Christian Behaviour,” and “Beyond Personality.”

The title does not mean that the book is about a separate religion called “mere Christianity.” Lewis used the phrase for the common Christian faith beneath denominational differences. The work became one of his best-known books of Christian apologetics.