Morality without God

C.S. Lewis on explaining morality without God:

Now [the Law of Decent Behaviour] is really so peculiar that one is tempted to try to explain it away. For instance, we might try to make out that when you say a man ought not to act as he does, you only mean the same as when you say that a stone is the wrong shape; namely, that what he is doing happens to be inconvenient to you. But that is simply untrue. A man occupying the corner seat in the train because he got there first, and a man who slipped into it while my back was turned and removed my bag, are both equally inconvenient. But I blame the second man and do not blame the first. I am not angry–except perhaps for a moment before I come to my senses with a man who trips me up by accident; I am angry with a man who tries to trip me up even if he does not succeed. Yet the first has hurt me and the second has not. Sometimes the behaviour which I call bad is not inconvenient to me at all, but the very opposite. In war, each side may find a traitor on the other side very useful. But though they use him and pay him they regard him as human vermin. So you cannot say that what we call decent behaviour in others is simply the behaviour that happens to be useful to us. And as for decent behaviour in ourselves, I suppose it is pretty obvious that it does not mean the behaviour that pays. It means things like being content with thirty shillings when you might have got three pounds, doing school work honestly when it would be easy to cheat, leaving a girl alone when you would like to make love to her, staying in dangerous places when you could go somewhere safer, keeping promises you would rather not keep, and telling the truth even when it makes you look a fool.

Some people say that though decent conduct does not mean what pays each particular person at a particular moment, still, it means what pays the human race as a whole; and that consequently there is no mystery about it. Human beings, after all. have some sense; they see that you cannot have any real safety or happiness except in a society where every one plays fair, and it is because they see this that they try to behave decently. Now, of course, it is perfectly true that safety and happiness can only come from individuals, classes, and nations being honest and fair and kind to each other. It is one of the most important truths in the world. But as an explanation of why we feel as we do about Right and Wrong it just misses the point. If we ask: ‘Why ought I to be unselfish?’ and you reply ‘Because it is good for society,’ we may then ask, ‘Why should I care what’s good for society except when it happens to pay me personally?’ and then you will have to say, ‘Because you ought to be unselfish’–which simply brings us back to where we started. You are saying what is true, but you are not getting any further. If a man asked what was the point of playing football, it would not be much good saying ‘in order to score goals,’ for trying to score goals is the game itself, not the reason for the game, and you would really only he saying that football was football–which is true, but not worth saying. In the same way, if a man asks what is the point of behaving decently, it is no good replying, ‘in order to benefit society,’ for trying to benefit society, in other words being unselfish (for ’society’ after all only means ‘other people’), is one of the things decent behaviour consists in; all you are really saying is that decent behaviour is decent behaviour. You would have said just as much if you had stopped at the statement, ‘Men ought to be unselfish.’

-Mere Christianity, Book 1 (Right and Wrong as a Clue to the Meaning of the Universe), Chapter 3 (The Reality of the Law)