There are different relations between human benefits, so the standards of justice need concrete analysis. The relationship between people's benefits is divided into two types: one is conflict, one rises as the other fall (up-down); and the other type is non-conflict, one rise with the other rise or remain fixed (up-up). The non-conflict interests exist everywhere, and it is the unification of interests. The unification of interests is also called win-win and harmony. It is the most ideal situation. The act of justice in this relationship is both selfish and good.

Theorem: Benefit of each person is the criterion of justice when benefits of people are in the up-up relation.

When interests are united, they do not cause conflicts between people. They are what all people are willing to accept and are the basis for people's cooperation.

there are two kinds of up-down. (a) the total benefit is not able to rise or avoid to fall; (b) the total benefit is able to rise or avoid to fall.

Theorem: Both choices on benefit between the subject and others may be justice when benefits conflict and the total benefit is not able to rise or avoid to fall.

For example, there is only one champion in a sports competition. Whatever you choose it means someone has to sacrifice. At this time, whatever you choose is justice.

If the sum of benefits may increase, then one party needs to make sacrifice to achieve Paretian optimization. At this time, the choice of justice is to sacrifice the interests of someone in order to realize the greatest benefit.

Theorem: The maximization of benefit is justice when benefits conflict and the total benefit is able to rise or avoid to fall.

In many countries, efficiency is prioritized and fairness is taken into consideration. Efficiency here refers to the maximization of social benefits, not to the efficiency of a machine or a social organization.

Although it is difficult to calculate the sum of interests, people have been making such calculations and comparisons. For example, after the Vietnam War, Americans felt that national interests were overestimated and they no longer wished to sacrifice their own interests for national interests. But after