What was C.S. Lewis’s Christian apologetics book based on wartime radio broadcasts called?

C.S. Lewis’s apologetics book based on wartime radio broadcasts is Mere Christianity.

The book developed from a series of radio talks Lewis gave for the BBC during the Second World War. The broadcasts began in 1941, when Britain was under severe wartime pressure, and Lewis’s clear speaking style made him widely recognized. The talks were later revised and collected in book form.

Mere Christianity presents a case for basic Christian belief rather than arguing for one denomination. Lewis discusses morality, human behavior, Christian doctrine, and the significance of Jesus. The title refers to what he regarded as shared or central Christian belief across denominational divisions.

The work is often confused with The Problem of Pain, another major apologetics book by Lewis, but that book addresses suffering and divine goodness. Mere Christianity is specifically connected to the BBC talks. Its conversational structure reflects its origin in spoken broadcasts rather than in a single uninterrupted manuscript.