What kind of broadcasts formed the original basis of C.S. Lewis’s Mere Christianity?

C.S. Lewis’s Mere Christianity began as BBC radio broadcasts.

Lewis delivered a series of short talks for the BBC during the Second World War. The first series was broadcast in 1941, followed by additional series in 1942 and 1944. He spoke directly to a broad public audience about basic Christian beliefs rather than presenting a denominational theological system.

The talks were later revised and collected into book form. Mere Christianity was published in 1952 and brought together material from the broadcasts in three major sections: “Right and Wrong as a Clue to the Meaning of the Universe,” “What Christians Believe,” and “Christian Behaviour.”

The title does not mean a new church or denomination. Lewis used “mere Christianity” for the common core of beliefs shared by historic Christian traditions. The book is therefore rooted in radio talks, although its final form was edited and expanded for print.