C. S. LEWIS AND THE MORAL ARGUMENT
[T]his Law or Rule about Right and Wrong used to be called the Law of Nature). . . .
This law was called the Law of Nature because people thought that every one knew it by nature and did not need to be taught it. They did not mean, of course, that you might not ﬁnd an odd individual here and there who did not know it, just as you ﬁnd a few people who are colour-blind or have no ear for a tune. But taking the race as a whole, they thought that the human idea of decent behaviour was obvious to every one. And I believe they were right. If they were not, then all the things we said about the war were nonsense. What was the sense in saying the enemy were in the wrong unless Right is a real thing which the Nazis at bottom knew as well as we did and ought to have practised? If they had had no notion of what we mean by right, then, though we might still have had to ﬁght them, we could no more have blamed them for that than for the colour of their hair.
I know that some people say the idea of a Law of Nature or decent behaviour known to all men is unsound, because different civilisations and different ages have had quite different moralities.
But this is not true. There have been differences between their moralities, but these have never amounted to anything like a total difference. If anyone will take the trouble to compare the moral teaching of, say, the ancient Egyptians, Babylonians, Hindus, Chinese, Greeks and Romans, what will really strike him will be how very like they are to each other and to our own. Some of the evidence for this I have put together in the appendix of another book called The Abolition of Man; but for our present purpose I need only ask the reader to think what a totally different morality would mean. Think of a country where people were admired for running away in battle, or where a man felt proud of double-crossing all the people who had been kindest to him. You might just as well try to imagine a country where two and two made five. Men have differed as regards what people you ought to be unselﬁsh to—whether it was only your own family, or your fellow countrymen, or everyone. But they have always agreed that you ought not to put yourself ﬁrst. Selﬁshness has never been admired. Men have differed as to whether you should have one wife or four. But they have always agreed that you must not simply have any woman you liked.
But the most remarkable thing is this. Whenever you ﬁnd a man who says he does not believe in real Right and Wrong, you will ﬁnd the same man going back on this a moment later. He may break his promise to you, but if you try breaking one to him he will be complaining “It’s not fair” before you can say Jack Robinson. A nation may say treaties do not matter; but then, next minute, they spoil their case by saying that the particular treaty they want to break was an unfair one. But if treaties do not matter, and if there is no such thing as Right and Wrong—in other words, if there is no Law of Nature—what is the difference between a fair treaty and an unfair one? Have they not let the cat out of the bag and shown that, whatever they say, they really know the Law of Nature just like anyone else?
C. S. Lewis
(Mere Christianity 4-5)