Justice can mean either lawfulness or fairness, since injustice is lawlessness and unfairness. The laws encourage people to behave virtuously, so the just person, who by definition is lawful, will necessarily be virtuous. Virtue differs from justice because it deals with one’s moral state, while justice deals with one’s relations with others. Universal justice is that state of a person who is generally lawful and fair. Particular justice deals with the “divisible” goods of honor, money, and safety, where one person’s gain of such goods results in a corresponding loss by someone else.

There are two forms of particular justice: distributive and rectificatory. Distributive justice deals with the distribution of wealth among the members of a community. It employs geometric proportion: what each person receives is directly proportional to his or her merit, so a good person will receive more than a bad person. This justice is a virtuous mean between the vices of giving more than a person deserves and giving less.

Rectificatory justice remedies unequal distributions of gain and loss between two people. Rectification may be called for in cases of injustice involving voluntary transactions like trade or involuntary transactions like theft or assault. Justice is restored in a court case, where the judge ensures that the gains and losses of both parties are equaled out, thus restoring a mean.

Justice must be distributed proportionately. For instance, a shoemaker and a farmer cannot exchange one shoe for one harvest, since shoes and harvests are not of equal value. Rather, the shoemaker would have to give a number of shoes proportional in value to the crops the farmer provides. Money reflects the demand placed on various goods and allows for just exchanges.

Political justice and domestic justice are related but distinct. Political justice is governed by the rule of law, while domestic justice relies more on respect. Political justice is based in part on natural law, which is the same for all people, and in part on particular legal conventions, which vary from place to place.

An agent is responsible only for acts of injustice performed voluntarily. We call injustice done out of ignorance “mistakes,” injustice done because plans went awry “misadventures,” and injustice done knowingly but without premeditation “injuries.” Ignorance is an excuse only if it is reasonably unavoidable.