Which C.S. Lewis book presents a series of conversations defending Christianity?

Mere Christianity presents a series of conversations defending and explaining basic Christian belief. C.S. Lewis adapted the material from radio talks broadcast by the BBC during World War II.

The book is organized around moral law, Christian belief, and Christian conduct. Lewis aimed to describe shared ideas among major Christian traditions rather than argue for one denomination’s distinctive doctrines.

The title reflects that purpose: “mere Christianity” means the common core of belief Lewis believed was shared across historic Christian denominations. The final book appeared in 1952 after material from several broadcast series was revised and combined. It became one of Lewis’s most widely read works of Christian apologetics.