CS Lewis opens his book Mere Christianity by talking about how often you will hear people saying things like: "That’s my seat, I had to get up to go and do so and so" or "Let me have a bit of your orange- I gave you some of mine yesterday" or "You promised you were going to do such and such, go and do it".
He points out that if you pay attention to people talking for a bit you will notice how we all seem to be appealing to a common standard of behavior- an unwritten set of rules that everybody is assumed to understand and have in common. You will notice that when people disagree, they will usually say something like "well you ought to have announced before you left that you would want your chair back" or "things were quite different when you gave me your orange" or "I promised to do such and such only if this and that". In other words, they are in turn appealing back to the same set of shared, unwritten standards to argue their case. Lewis points out that you almost never hear someone say: "Well, to hell with your standards!"
That's mostly true- but I have found that it is an excellent way to win arguments.