C.S. Lewis — Mere Christianity and the Moral Law

Why It Matters

Lewis wrote Mere Christianity as radio broadcasts during World War II — wartime England, when the question of whether there is an objective difference between good and evil was not academic but urgent. He was arguing against moral relativism not as an intellectual exercise but as an act of resistance: the idea that some things are genuinely wrong, not merely unfashionable or inconvenient, was a claim with real stakes. That claim still has real stakes.

The argument from the Moral Law is one of the most elegant natural theology arguments ever made. It does not require theological premises — it starts from ordinary human experience (quarrels, fairness, conscience) and argues that this experience cannot be explained without reference to something outside the natural order. Whether you find the argument ultimately convincing or not, understanding it changes how you think about morality and its foundations.

Lewis was one of the greatest intellectual converts of the twentieth century. He was a convinced atheist, trained in philosophy and literature, who spent years resisting the conclusion his own reasoning was producing. His account of how and why he eventually accepted it is one of the most intellectually honest conversion narratives ever written. He is valuable not just for his conclusions but for his method: the willingness to follow an argument honestly wherever it leads, even when the destination is inconvenient.

A Story

The Most Reluctant Convert in England

In 1929, C.S. Lewis — then a don at Oxford, a convinced atheist and materialist — knelt in his room and admitted that God was God. He described himself as 'the most dejected and reluctant convert in all England.' He did not want it to be true. He had spent years trying to find arguments against the conclusion his own reasoning was reaching, and he had run out of objections.

Lewis had been an atheist since his early teens. His mother died when he was nine years old; he had prayed for her recovery and she had not recovered. He drew the obvious conclusion: either there is no God, or God is not in the business of answering prayers. He went off to the Great War, was wounded at the Battle of Arras, and returned to Oxford to study philosophy and literature with ferocious intelligence and a settled determination to make sense of the world without any supernatural assistance.

But the arguments kept failing. He was first a realist about absolute value — he believed in a world of objective ideals, beautiful in themselves. He was persuaded by Idealism that the absolute mind was required to ground those ideals. Then his friend Owen Barfield argued so effectively against the materialism he was clinging to that Lewis later said Barfield 'killed' his last hope of being an uncomplicated materialist. He fought with enormous energy against the conclusion, and he lost.

The final step came in a conversation with his friends Hugo Dyson and J.R.R. Tolkien late one night, walking the paths of Addison's Walk at Oxford. They talked about myth and meaning and the strange way that pagan myths about dying and rising gods seemed to be pointing at something. Lewis had always loved those myths but dismissed them as beautiful lies. Tolkien argued that they were true myths — myths in which the truth of the universe was expressing itself imperfectly, reaching toward the one myth that would turn out to be fact. Lewis could not answer this.

A few days later, on a trip to the zoo, he felt the shift happen. He got on the bus one way and arrived at the zoo another way. He had not decided anything; something had resolved.

But Lewis's Christianity was not Augustinian — it was not grounded in personal experience of grace or restlessness. It was grounded in argument. Twelve years after his conversion, during the dark early years of World War II, the BBC asked him to give radio talks explaining Christian belief to a general audience. He did not begin with scripture or church authority. He began with quarrels.

'I want to begin by trying to get you to see,' he said, 'that there is something curious about the way human beings argue with each other.' When two people quarrel — really quarrel, not just fight — each person appeals to some standard that the other person ought to recognize. 'That's not fair.' 'That's not my fault.' 'You promised.' These appeals only make sense if there is a standard that everyone knows and that everyone is bound by, whether or not they choose to observe it.

He called it the Law of Human Nature, or the Moral Law. It is not the same as instinct, because instinct cannot tell you which instinct to follow when they conflict. It is not the same as social convention, because you can stand outside social convention and judge it — and that judgment implies a standard beyond convention. Something is telling you what you ought to do. That something cannot be inside the natural world, because it stands in judgment over the natural world. What it is, Lewis argued, is what the whole natural world is inside of.

Vocabulary

Moral Law

Lewis's term for the universal standard of behavior that human beings seem to know and consistently appeal to, even when they violate it. It is the basis of every appeal to fairness, honesty, and decency — the standard that makes genuine quarreling (as opposed to mere fighting) possible. Lewis argues its existence points to a Lawgiver.

Natural law

The tradition in philosophy and theology — running from Aristotle through Aquinas to Lewis — that moral truths are discoverable by reason from human nature and the structure of reality, independent of divine revelation. Natural law holds that some things are genuinely right or wrong, not merely socially constructed or culturally relative.

Mere Christianity

Lewis's term for the core of Christian belief that nearly all Christians across denominations share — the 'hall' before the 'rooms' of specific traditions. His book by this title argues for the truth of this core from first principles, without appealing to any particular church's authority.

Moral relativism

The view that moral claims are not objectively true or false but relative to individuals, cultures, or times. Lewis argues against this with the observation that no one actually lives as though it were true — everyone appeals to objective standards when wronged, which implies they believe in those standards.

Theism

The belief that there is a God — a personal, moral being who created and sustains the universe. Lewis's argument from the Moral Law is an argument for theism: that the existence of moral reality points to a moral ground of all reality. Theism is distinct from deism (a God who creates but does not interact) and from Christianity specifically.

Guided Teaching

Lewis's argument is elegant precisely because it begins with something everyone has experienced. Think of the last time someone treated you unfairly. What did you feel? You probably felt something like 'that was wrong' — not merely 'I didn't like that,' but 'that was actually wrong, and they should know it.' Lewis asks: what is the basis of that feeling? If morality is purely personal preference, then 'that was wrong' means nothing more than 'I disliked that.' But that is not what you meant. You meant there was a standard that they violated — a standard they should have recognized. Where does that standard come from?

The two easy answers are instinct and social convention. Lewis takes both seriously and rejects both. Instinct can't be the answer, because when two instincts conflict — say, the instinct for self-preservation and the instinct to help someone in danger — the Moral Law tells you which one to follow, rather than being identical to either of them. Something stands above instinct, judging it. Social convention can't be the answer because you can judge a society's conventions as cruel or unjust, and that judgment implies a standard outside any particular society's conventions. Where is it coming from?

Lewis's conclusion is that the Moral Law is evidence for a Reality beyond the natural world — a Reality that is moral through and through, that human beings have some kind of contact with through conscience. He is careful about what the argument proves and what it doesn't. It proves that something like a Lawgiver exists. It does not prove Christianity specifically. The next step — from Theism to Christianity — requires different arguments. But the first step is the crucial one, and it is available to anyone who is willing to take their own moral experience seriously.

Here is the hardest challenge Lewis poses: do you actually believe morality is relative? Not as an intellectual position, but in how you live. If someone breaks a promise to you, or treats you unjustly, or lies to you — do you feel merely 'that's not to my taste,' or do you feel 'that was actually wrong'? If the latter, you already believe in objective morality. You may not have a good theory of where it comes from, but you believe in it. Lewis is inviting you to be honest about what you already believe — and then to follow that belief to its implications, wherever they lead.

For Discussion

1. 1.Lewis starts with quarrels. Why is quarreling philosophically significant? What does it reveal about our moral assumptions?
2. 2.What is the Moral Law, and how does Lewis argue that it is different from instinct and social convention?
3. 3.Lewis says the Moral Law points to a Lawgiver. Is the inference sound? What is the strongest objection to it, and how would Lewis respond?
4. 4.Lewis was a reluctant convert — he did not want it to be true. Does his reluctance make his conversion more or less credible? Why?
5. 5.How does Lewis's argument relate to what Aristotle said about human nature and virtue? Are they compatible, or do they conflict?
6. 6.If morality is objective — if there really is a Moral Law — does that change anything about how you live? What would be different?

Practice

The Quarrel Analysis

1. 1.Think of a recent genuine dispute — a situation in which you felt treated unfairly, or in which you witnessed something that seemed genuinely wrong. Describe the situation briefly in writing.
2. 2.Now analyze the moral claim you made (explicitly or implicitly). What standard were you appealing to? Where does that standard come from? Try to answer this as precisely as possible: not 'from society' but from which society, and why should its standards bind anyone?
3. 3.Now apply Lewis's test: is the standard you appealed to the same as instinct? Is it the same as social convention? If not, what is it?
4. 4.Write a paragraph responding to this question honestly: Do you believe there are things that are genuinely, objectively wrong — not just unfashionable or personally displeasing, but actually wrong, in a way that does not depend on any particular person's or culture's preferences? What is the basis of that belief?
5. 5.Discuss your paragraph with a parent. Ask them whether they think moral relativism is livable — whether anyone actually lives as though morality is merely a matter of preference.

Memory Questions

1. 1.What is Lewis's Moral Law, and how does he argue for its existence?
2. 2.Why does Lewis reject the idea that the Moral Law is simply instinct?
3. 3.Why does Lewis reject the idea that the Moral Law is simply social convention?
4. 4.Why does Lewis describe himself as 'the most reluctant convert in England'?
5. 5.What does Lewis argue the Moral Law points to, and what does it not prove on its own?