Mere Christianity by C.S. Lewis is a classic work of Christian apologetics, adapted from WWII-era radio talks, that defends the essential, shared beliefs of Christianity. Lewis argues that a universal human awareness of moral law suggests a divine lawgiver, ultimately presenting a rational case for Jesus Christ as God and urging personal transformation. The book is structured into four parts: arguments for God, Christian theology, morality and behavior, and a discussion on the nature of God.