Glaucon and Adeimantus have been silent, but now that the discussion in Book I has ended unsatisfactorily, they are disappointed with the outcome. Glaucon challenges Socrates not just to drive his interlocutors into contradiction, as he has done thus far, but to demonstrate once and for all that the just life really is better than the unjust life.

Socrates accepts the challenge and tries to meet it in the remaining books of the Republic.

The Search for Justice

Socrates first takes up the question of what justice is (Republic II.368c). This is what the reader might expect, given his practice in the early dialogues, but now, in the Republic, Socrates proceeds in an unexpected way. Instead of searching for what justice is, he searches for what justice is in a city and what it is in an individual. He says that he will search for what justice is in a city, because it is "bigger," and so presumably more straightforward to consider, and then, with the nature of justice in the city understood, he will search for what justice is in a human being.

This strategy can seem puzzling, but the Gorgias provides some explanation. Socrates says of a human being whose soul is properly organized and ordered that "if he did what is appropriate with respect to human beings, he would be doing what is just." He also says, a few lines earlier, that "when a certain order, the proper one for each thing, is present, a thing is good."

Remember also that Thrasymachus demanded that Socrates not explain what justice is by supplying a synonym. He wants Socrates to say what justice is in terms of the underlying facts.

"[D]o you yourself answer and tell us what you say the just is. And don't you be telling me that it is that which ought to be, or the beneficial or the profitable or the gainful or the advantageous, but express clearly and precisely whatever you say. For I won't take from you any such drivel as that" ( Republic I.336d; cf. Clitophon 409c).

These passages help explain the strategy Socrates pursues in the Republic. The suggestion is that the correct answer to the "What is justice?" question is the relatively uninformative one that justice is what is appropriate with respect to human beings. In the Republic, unlike in the early dialogues, the pursuit of a definition is no longer what drives the discussion. The search is for justice is in a city and in an individual. Socrates begins with the search for justice in the city. This is a search for the proper organization of human beings into cities.

P.Oxy.LII 3679, manuscript from the 3rd century AD, Plato's Republic V.472e-473d. (P.Oxy is the Oxyrhynchus Papyri.
Oxyrhynchus is a city in Egypt situated on a branch of the Nile river, about 185 miles south of Alexandria. The papyri
were in the town dumps, which provided ideal conditions for preservation.)

Justice in the City

Human beings organize themselves in cities to make their lives better. Cities provide the benefits of group living, but there are appropriate and inappropriate ways that human beings can organize themselves into a city. The appropriate organizations constitute justice in the city. These organizations function in a certain way.

Socrates says these organizations function so that the city has three parts. It has a guardian or ruling class. The rulers are lovers of wisdom (Republic V.473d). They introduce the rules, for production and distribution of goods and for behavior of individuals in the city more generally. The city also has an auxiliary class. Its job is to enforce the rules. Finally, the city has a working class to produce the services and material goods. The rulers must rule, the auxiliaries must enforce the rules, and the workers must produce the services and material goods.

"I think our city, if it has been rightly (ὀρθῶς) founded, is completely good (τελέως ἀγαθὴν). Clearly, then, it will be wise (σοφή), brave (ἀνδρεία), moderate (σώφρων), and just (δικαία). So if we find any of these qualities in it, the remainder will be that which we have not found" (Republic IV.427e).

Socrates says that this city is wise because the rulers are wise, brave because the auxiliaries are brave, moderate because everyone is controlled, and just because each of three parts does its own job.

"The proper functioning of the working class, the guardians, and the rulers, each doing its own work in the city, ... would be justice (δικαιοσύνη) and would render the city just" (Republic IV.434c-d).

Justice is in the Individual

Now that they have found justice in the city, they search for justice in an individual human being.

"If you call a thing by the same name whether it is big or little, it is like in the way in which it is called the same or like. Then a just man too will not differ at all from a just city in respect of the very form of justice, but will be like it. But now the city was thought to be just because three natural kinds existing in it performed each its own function, and again it was sober, brave, and wise because of certain other affections and habits of these three kinds. Then, my friend, we shall thus expect the individual also to have these same forms in his soul, and by reason of identical affections of these with those in the city to receive properly the same appellations" (Republic IV.435a-c).

Because human beings are psychological beings, what is appropriate for the individual human being is a certain organization of the parts of his psychology. The human soul is tripartite. The appropriate organization of these parts is one in which "reason" (λογιστικὸν) rules and has "spirit" (θυμοειδές) as its ally against "appetite (ἐπιθυμητικόν)."

"It is fitting for the reasoning part to rule (ἄρχειν), it being wise and exercising foresight on behalf of the whole soul, and for the spirited part to obey it and be its ally" (Republic IV.441e)."These two parts... will exercise authority over the appetitive part which is the largest part and is insatiable for possessions. They will watch over it to see that it is not filled with so-called pleasures of the body, and by becoming enlarged and strong thereby no longer does its own job but attempts to enslave and rule over those over whom it is not fitted to rule, and so upsets everyone's whole life" (Republic IV.442a-b).

This organization of the parts is justice in a human being.

Perseus Digital Library:
Plato's, Republic