Book 5, Chapter 1. In Book V, Aristotle turns to questions about justice—namely, what sort of actions justice and injustice are concerned with, and what extremes justice is the mean between. Justice is concerned with what is lawful and fair, and injustice with what’s lawless and unfair.
The virtue of justice is concerned with a broader range of scenarios than those previously discussed—with far-reaching implications for society—which is why Aristotle devotes an entire book to it.
In a larger sense, justice is concerned with everyone’s benefit—what we call “just,” Aristotle says, “is whatever produces and maintains happiness and its parts for a political community.” The law procures such justice by requiring “actions in accord with the other virtues” and prohibiting those associated with vices.
Aristotle says that this type of justice—well established in law—is “complete virtue.” He quotes the proverb, “in justice all virtue is summed up.” The reason justice is such “complete virtue” is that it’s the exercise of the virtues “in relation to another, not only in what concerns [oneself],” something not everyone can achieve. In sum, “insofar as virtue is related to another, it is justice, and insofar as it is a certain sort of state without qualification, it is virtue.”
Unlike the other virtues in isolation, justice looks out for the benefit of fellow members of the community. In fact, when any other virtue is exercised in relation to others, it can be properly classified as justice. That’s why Aristotle considers justice a kind of summation of all virtue.
Book 5, Chapters 2-7. Aristotle discusses various “species” of the just. With regard to justice in distribution, the just is the intermediate between fair and unfair; it must be proportionate (seeking “equal shares for equal people”). In contrast, the just in transactions has to do with proportionality—the law’s treatment of differences in harm inflicted and its attempt to restore a situation to equality (for example, in situations where theft, wounding, or death have occurred). In such cases, something must be subtracted from the one who has more and given to the one who has less. There is also justice in exchange—reciprocity—which holds cities together; currency helps maintain this kind of justice. Political justice pertains more broadly to maintaining a common life among equals.
Each of the “species” of justice named by Aristotle in some way seeks to maintain or restore fairness within a community. For example, justice in exchange is important because communities are sustained partly through people’s exchange of goods with one another, a process which often requires equalization through price-setting.
Book 5, Chapters 8-9. The question of whether or not an act is voluntary helps to determine whether it’s an instance of injustice or not—for example, if harm is inflicted beyond the “reasonable expectation” of the person causing it, then it’s a misfortune, not an injustice. Factors like ignorance, and whether an act was committed in anger, also factor into deciding whether a harm is to be pardoned or not. Likewise, an act is not just unless there’s been deliberation and a decision to act justly.
Aristotle’s preconditions for virtue apply to questions of justice and law, too—since virtue must be voluntary, the question of a person’s will and intent can help in judging whether justice or injustice have occurred.
Book 5, Chapters 10-11. Aristotle argues that decency is actually superior to justice. He claims that this is because a universal law sometimes falls short of being able to address every particular, and in such cases, decency makes up the deficiency in the law. A decent person, for example, might choose not to be “an exact stickler for justice in the bad way, but [takes] less than he might even though he has the law on his side.”
Legislation cannot adequately address every scenario, and in such cases, the virtue of decency helps to set things right. Decency is basically a discerning attitude which understands that justice is bigger than the law. This is another example of the importance of wisdom, not assuming that virtues can be woodenly applied.