What is theme of the passage?

Directions: Read the paragraph and answer the question that follows.

Every one has heard people quarrelling. 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.
Now what interests me about all these remarks is that the man who makes them is not merely saying that the other man's behaviour does not happen to please him. He is appealing to some kind of standard of behaviour which he expects the other man to know about. And the other man very seldom replies: To hell with your standards�. 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 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 some kind of Law or Rule of fair play or decent behaviour about which they really agreed. If they had not, they might, of course, fight like animals, but they could not quarrel in the human sense of the word Quarreling means trying to show that the other man is in the wrong. And there would be no sense in trying to do what unless you and he had some sort of agreement as to what Right and Wrong are; just as there would be no sense in saying that a footballer had committed a foul unless there was some agreement about the rules of football.