The Law of Human Nature
When people quarrel, a person is trying to show that the other person is wrong. In order for this to happen, both of them have to agree on what is Right and Wrong. Just like in a soccer game, we cannot say a player commits a foul if the rule is not agreed by everyone.
This human morality of Right and Wrong is called the Law of Nature. to be more exact, The Law of Human Nature. In modern days, people refer the Law of Nature as the law of gravity, chemistry or heredity. We live by this kind of Law of Nature, our physical body has no freedom of choosing to obey or disobey the rule of gravity. We throw a rock, it falls. We jump up high, we fall back to the ground. We obey the Law of Nature no matter how much we are trying to go against them.
This is very similar to the Law of Human Nature. These laws are also called the Moral Law that all humans agree to. For example, you must not put yourself first before others. True that different cultures might have different morals. One culture says it's Right for a man to marry just one woman, and the other culture says it's Right for a man to marry as many women as he desires. But both cultures have a common morality of men having to marry the woman he likes. the Law of Human Nature is the soccer game's rule that all humans agree to, consciously or unconsciously.
In other words, we are rather "pressed on" by the Law of Human Nature. However, we never truly follow these rule of descent behavior. Even if we do not believe in it, our conscience brings guilt to us when we do not behave decently. Because we cannot help facing the fact of breaking it.
We are left off by two points. Firstly, all humans on this earth have an idea that they should behave in a certain way, and that we have no power against it. Secondly, we always fail to behave in that certain way. We have the ability to know it, but not the ability to practice it. This is a big clue and foundation to the meaning of us and the universe we live in.