Apologetics
C.S. Lewis and the Case for Christianity
A former atheist built the most famous argument for faith in the 20th century. It still holds up.
C.S. Lewis didn't grow up believing in God. He grew up, lost his mother to cancer at age nine, survived the trenches of World War I, and concluded that the universe was cruel and pointless. He was a committed atheist — not casually, but intellectually. He thought Christianity was a myth, and he was confident about it.
Then he changed his mind. And the book that came out of it — Mere Christianity — became the most influential work of Christian apologetics in the 20th century.
The Setup
Lewis was a professor at Oxford, surrounded by brilliant minds. Two of his closest friends — J.R.R. Tolkien and Hugo Dyson — were Christians. Lewis found this irritating. These were not stupid men. Why did they believe something so obviously false?
The conversations continued for years. Slowly, Lewis found his objections crumbling — not because of emotional pressure, but because the intellectual case for Christianity was stronger than he expected.
In 1931, Lewis became a Christian. Not enthusiastically. He later described himself as "the most dejected and reluctant convert in all England." He didn't want it to be true. He just couldn't escape the evidence.
The Core Argument
Mere Christianity started as a series of BBC radio talks during World War II. Lewis wasn't writing for theologians — he was writing for ordinary people in the middle of a crisis, trying to make sense of the world.
His argument builds in layers:
Layer 1: The Moral Law. Every human being has a sense of right and wrong. Not identical moral codes, but a shared framework. Lewis argued this moral can't be explained by evolution or culture alone — it points to something beyond us.
Layer 2: The Lawgiver. If there's a real moral law, there must be a real moral Lawgiver. The standard has to come from somewhere. Lewis argued it comes from a Mind behind the universe — what we call God.
Layer 3: The Trilemma. This is the argument Lewis is most famous for. claimed to be God. Lewis said there are only three possibilities:
- Lord — He was telling the truth, and he really is God
- Liar — He knew he wasn't God but said it anyway
- Lunatic — He genuinely believed he was God but was mentally ill
Lewis argued that everything we know about — his teaching, his character, his impact — makes the liar and lunatic options untenable. Which leaves one option.
Why It Still Works
The trilemma gets criticized. Scholars point out that Lewis oversimplified — maybe Jesus was misquoted, or maybe "Son of God" meant something different in first-century Judaism.
These are fair questions. But Lewis's fundamental point stands: Jesus's claims are not the claims of a merely good teacher. He claimed authority to forgive sins. He claimed to have existed before . He accepted . Either those claims are true, or something is seriously wrong with the person making them.
The "great moral teacher" option — which many people prefer — is the one Lewis argued is actually impossible. A great moral teacher doesn't lie about being God.
What Makes Lewis Different
Lewis wasn't arguing from inside the church. He was arguing as someone who had been OUTSIDE it and been dragged in by the evidence. That's what gives Mere Christianity its power.
He also deliberately avoided denominational arguments. He wasn't making a case for Catholicism or Protestantism or Anglicanism. He was making a case for the basic claims that all Christians share: God exists, is who he said he was, and that changes everything.
"I am trying here to prevent anyone saying the really foolish thing that people often say about Him: 'I'm ready to accept Jesus as a great moral teacher, but I don't accept His claim to be God.' That is the one thing we must not say."
The Bottom Line
Lewis didn't become a Christian because it felt good. He became one because he followed the evidence and couldn't escape the conclusion.
Mere Christianity isn't a warm, fuzzy book about faith. It's a rigorous, carefully reasoned argument that respects the reader's intelligence. It assumes you have doubts. It assumes you have objections. And it walks through them one by one.
Eighty years later, it remains the book that people hand to friends who say, "I just can't believe in this stuff." Because Lewis was that friend once. And he found his way through.