What was the title of C.S. Lewis’s 1950 Christian apologetics book about basic beliefs?

C.S. Lewis’s 1950 Christian apologetics book about basic beliefs was Mere Christianity.

The book developed from talks Lewis delivered in radio broadcasts during the Second World War. The talks were aimed at a general British audience rather than at specialists, and Lewis tried to explain shared Christian beliefs in accessible language.

Mere Christianity is organized into discussions of morality, Christian belief, and the practical implications of faith. Its title refers to what Lewis considered the common or central beliefs of Christianity, rather than the distinctive doctrines of one denomination.

The work is often confused with The Problem of Pain, published in 1940, or Miracles, published in 1947. Those books address related theological questions, but Mere Christianity specifically grew out of Lewis’s wartime broadcast talks and became one of his most widely read apologetic works.