C.S. Lewis' "Mere Christianity" presents a foundational defense of universal morality and Christian theology by first establishing the existence of a shared human sense of right and wrong. He argues that this Moral Law is not a mere social convention or instinct, but a real objective standard that suggests a higher power exists behind the universe. Lewis explores how humanity has consistently failed to meet this standard, creating a need for the Atonement provided by Jesus Christ. By distinguishing "mere" Christianity from denominational disputes, he focuses on the central doctrines common to the faith. Ultimately, the text describes the transformation of the individual through a new kind of life offered by Christ. Lewis concludes that this spiritual evolution requires a deliberate choice to align oneself with God before the finality of the world's end.