A C.S. Lewis Quote (:

Everyone has heard people quarreling. Sometimes it sounds funny and sometimes it sounds merely unpleasant; but however it sounds, I believe we can learn something very important from listening to the kind of things they say. They say things like this: 'How'd you like it if anyone did the same to you?' - 'That's my seat, I was there first' - 'Leave him alone, he isn't doing you any harm' - 'Give me a bit of your orange, I gave you a bit of mine.' People say things like that everyday, educated people and uneducated people, and children as well as grown-ups. 

Now what interests me about all these remarks is that the man who makes them is not merely saying that the other man's behavior does not happen to please him. He is appealing to some kind of standard of behavior which he expects the other man to know about. And the other man very seldom replies: "To hell with your standard." Nearly always he tries to make out that what he has been doing does not really go against the standard, or that if it does there is some special excuse. He pretends that there is some special reason in this particular case why the person who took the seat first should not keep it, or that things were quite different when he was given the bit of orange. It looks, in fact, very much as if both parties had in mind the same kind of Law or Rule of fair play or decent behavior or morality or whatever you like to call it, about which they really agreed. Quarreling means to show that the other man is in the wrong.

And there would be no sense in trying to do that unless you and he had some sort of agreement as to what Right and Wrong are; just as there is no sense saying that a footballer had committed a foul unless there was some agreement about the rules of football. 

- "Mere Christianity" by C. S. Lewis