Summary

Published in 1952, C.S. Lewis's Mere Christianity stands as one of the most influential works of Christian apologetics in the 20th century. In this collection of essays, originating as a series of BBC radio talks given during World War II, Lewis, a former atheist, presents a rational case for faith. Divided into four parts, the book covers arguments for God's existence, core Christian theology, ethics, and the nature of God. Lewis's famous “Liar, Lunatic, or Lord” trilemma, which defends the divinity of Jesus, is one of the work's most discussed elements. Mere Christianity has been translated into over 30 languages and sold millions of copies worldwide. Accessible and heartfelt, Mere Christianity frequently appears on lists of the most important Christian books and continues to resonate with readers of all  denominations. 

Plot

Mere Christianity is a collection of C.S. Lewis's radio broadcasts during World War II, later compiled into book form. The content is divided into four main sections, each exploring different aspects of Christian faith and philosophy.

The first section presents Lewis's arguments for the existence of God, focusing on the concept of moral law and how it points to a higher power. Lewis contends that humans have an innate sense of right and wrong, which he believes indicates the presence of a divine creator.

In the second part, Lewis delves into Christian theology, presenting his famous “Liar, Lunatic, or Lord” trilemma regarding Jesus Christ. He argues that Jesus must have been either a liar, a madman, or truly the Son of God, rejecting the possibility that he was simply a great moral teacher.

The third and fourth sections explore Christian ethics and the nature of God, respectively. Lewis discusses cardinal virtues, the concept of Christian marriage, and the idea of pride as the root of all sin. He concludes by examining the Christian understanding of the Trinity and the process of becoming more Christ-like in one's daily life.

Themes

• The existence and nature of moral law

• Arguments for the existence of God

• The divinity of Jesus Christ

• Christian virtues and ethics

• The problem of pride and self-centeredness

• The importance of faith, hope and charity

• The Christian conception of God and spirituality

Setting

Mere Christianity originated as a series of BBC radio broadcasts delivered by C.S. Lewis during World War II, from 1941 to 1944. The setting is thus wartime Britain, with Lewis speaking to a nation enduring the hardships and uncertainties of global conflict. His talks were aimed at providing spiritual guidance and explaining the fundamentals of Christian faith to a broad audience seeking meaning and hope amid the chaos of war.

While the broadcasts were focused on Britain, the ideas Lewis presented were intended to transcend national boundaries and speak to universal human experiences. The “mere” Christianity he described aimed to distill the core beliefs shared by all Christian denominations, rather than delving into doctrinal differences. This approach allowed Lewis to address listeners across the English-speaking world, including in America where the talks were also broadcast.

Though rooted in a specific historical moment, Mere Christianity deals with timeless philosophical and theological questions. Lewis draws on examples from everyday life to illustrate abstract concepts, creating a sense of intimacy with his audience despite the impersonal medium of radio.

Key Figures

• C.S. Lewis: The author. Lewis was a British writer and lay theologian who converted from atheism to Christianity in his 30s. He became one of the most influential Christian apologists of the 20th century. In Mere Christianity, Lewis presents his arguments for the existence of God and the core beliefs of Christianity in a clear, logical manner accessible to a wide audience.

• God: The central figure in Christian theology. In Mere Christianity, Lewis argues for God's existence and explores the nature of God as understood in Christian doctrine. He presents God as a personal, omnipotent, and loving being who created the universe and desires a relationship with humanity.

• Jesus Christ: The son of God in Christian theology. Lewis discusses Jesus's claims to divinity and presents his famous “Liar, Lunatic, or Lord” trilemma as an argument for Christ's divine nature. He explores Jesus's role in Christian salvation and his teachings on morality and ethics.

• James Welch: The Director of Religious Broadcasting for the BBC who invited Lewis to give the radio talks that would eventually become Mere Christianity. Welch's invitation was instrumental in bringing Lewis's ideas to a wider audience.

• The Devil: While not a major character, Lewis occasionally refers to the Devil (or Satan) as the personification of evil and temptation in Christian theology. He discusses the concept of spiritual warfare between good and evil forces.

Quick facts

• Mere Christianity originated as a series of BBC radio talks given by C.S. Lewis during World War II.

• The talks were originally broadcast live, with Lewis having to strictly adhere to time limits.

• Mere Christianity was first published as three separate volumes before being combined into one book in 1952.

• The title “Mere Christianity” refers to the core beliefs shared by all Christian denominations.

• Mere Christianity has been translated into over 30 languages and sold millions of copies worldwide.

• The book introduces Lewis's famous “Liar, Lunatic, or Lord” trilemma argument about Jesus.

• Mere Christianity has been cited by many public figures, including the geneticist Francis Collins and attorney Charles Colson, as influencing their conversion to Christianity.

• In 2000, Christianity Today named it one of the most influential Christian books of the 20th century.

• Lewis intentionally avoided discussing denominational differences to focus on core Christian beliefs.

About the Author

C.S. Lewis (1898-1963) was one of the most influential writers and intellectuals of the 20th century. He wrote more than 30 books spanning multiple genres, including fantasy, science fiction, and Christian apologetics. He is perhaps best known for The Chronicles of Narnia, a beloved series of children's fantasy novels that have sold over 100 million copies worldwide and been adapted into major motion pictures.

Born in Belfast, Ireland, Lewis began his career as an academic, holding prestigious positions at both Oxford and Cambridge universities, where he taught English literature. He was a member of the informal literary discussion group known as the Inklings, which included his close friend J.R.R. Tolkien. Lewis's scholarly work focused on medieval and Renaissance literature, but it was his religious writings that brought him widespread fame. Books like Mere Christianity and The Screwtape Letters established Lewis as a leading Christian apologist, using reason and imagination to defend and explain the faith.

Lewis's personal life was marked by tragedy and unexpected joy. Raised in a religious household, he became an atheist as a young man before reconverting to Christianity in his early 30s. The death of his wife Joy Davidman from cancer in 1960, just a few years after their marriage, inspired his raw and deeply personal book A Grief Observed. Despite his fame, Lewis eschewed the limelight and political involvement, preferring to focus on his writing and academic work.

Lewis's influence has only grown. His works continue to sell millions of copies each year and inspire new generations of readers and writers. Lewis societies exist around the world to study and discuss his ideas, and he was honored with a memorial in Poets' Corner at Westminster Abbey in 2013. Whether through his imaginative fiction, incisive apologetics, or profound reflections on faith and human nature, C.S. Lewis remains a towering figure in both literature and Christian thought.