Political Philosophy Spring 2024

Justice in the City


Plato sets out to answer a question about individuals: why should someone be just? But before he addresses that question, he starts on what looks like a different one: what is justice in a city?

Plato’s assumption is that justice is the same for the city and for the individual, such that a description of justice in the city would help us to answer our original question about justice in the individual.

So Plato is going to try to answer four questions.

  1. What is a just city?

  2. Why is it good for a city to be just?

  3. What is a just person? (“individual” or “soul” are equivalent terms)

  4. Why is it good for a person to be just?

And he is going to try to answer these questions while also maintaining this assumption:

  1. Justice in the city is the same as it is in the individual soul.

Can he keep all five balls in the air? He comes surprisingly close! Plato is awesome.

I will start by summarizing the readings from Books II and III. Then I will say a bit about the selection and education of the guardians. Finally, we will talk about the first part of Book IV.

What happens in Books II and III

Socrates begins by explaining why people form cities in the first place.

The most basic reason is that we aren’t self-sufficient; we need to work with others to meet our needs. We do this through a division of labor (370b).

The kind of city that would be sufficient to meet our needs would be quite simple. There would be a division of labor but its members would only work to meet their needs. Glaucon describes this as a city fit for pigs, without proper furniture, the arts, and so on. So they move on to describe a second, luxurious city that would succeed it.

They did not find justice in the first city; if they had, that would be the end of the book. So you would expect the second city to be a step forward. But that does not seem to be Plato’s attitude. He seems to regard it as a step backwards. He calls the city of pigs “healthy” and its successor, where they will find justice, “fevered” (373a). I have to confess that I do not understand what he thinks about the first city, that is, the city of pigs. Is it bad or good? The rest of the argument does not depend on answering that, as far as I can see. So the fact that I do not know the answer is not a big deal. But it bugs me.

Moving along to the luxurious city, we find that it brings conflict, and hence the need for what Plato calls “guardians” to defend the city against outsiders who will want to take its goods.

But a class of guardians who are strong enough to defend the city from outsiders will also be capable of exploiting the insiders. We formed a city to benefit from a division of labor but that would be a bad deal if it meant being enslaved by the army. Is the situation hopeless? Plato thinks not. Guard dogs are ferocious towards outsiders but not their owners. Why? They are selected and trained to behave that way. Couldn’t we do something similar for guardians? Could a program of selection and training produce people who will defend the city from outsiders without taking advantage of the insiders?

Plato thinks the answer is yes and he describes how the selection and training of the guardians should go. You will find a lot of what he says rather eccentric. There is a lot of emphasis on music and poetry, for instance. It is not a modern educational program.

I am going to ask you to put the details to one side and consider the basic idea. That idea is that a society should put a lot of effort into identifying and training its leaders. You can have leaders who have been trained to be good at the job. Or you can have leaders who are good at being elected, as in a democracy. Or you can have leaders who are or good at picking their parents, as in a monarchy. Which system makes the most sense? It is not a bad question.

Where we are headed

This is what Plato is aiming at. There are three parts in the city and there are three corresponding parts of the soul.

Part of the City Part of the Soul
Guardians Rational
Auxiliaries Spirited
Productive class Appetitive

The guardians are the rulers. The auxiliaries are the security force; they are potential guardians who did not make the cut. The productive class is everyone else, that is, the people who make and sell goods and services. We will get to the soul next time.

Justice consists in each one of these parts sticking to its role and not interfering with the others. Here is what he says about the city.

the city was thought to be just when each of the three natural classes within it did its own work. (435b)

the principle that it is right for someone who is by nature a cobbler to practice cobblery and nothing else, for the carpenter to practice carpentry, and the same for the others is a sort of image of justice — that’s why it’s beneficial. (443c)

You can see why this would be a good thing. Everyone is doing what they do best. You cannot get better than best! It is less clear why you would call it justice.

A split among the virtues in Book IV

Virtues are good qualities. Vices, by contrast, are bad ones.

Plato says a good city would have four virtues: wisdom, courage, moderation, and justice. Why only four? Got me.

The city has the first two virtues, wisdom and courage, because of the roles played by the different classes. For instance, the city is wise because it is ruled by the class that knows the most about what is good and is the most dedicated to the city: the guardians. And it is courageous because the auxiliaries are in charge of their defense.

Note that the city is not courageous because everyone is courageous; it is only the auxiliaries who have to be courageous (see 429b). Nor is the city wise because everyone is wise (428e). The city has these qualities because a particular class plays its role: the guardians run the city and the auxiliaries defend it.

The third and fourth virtues, moderation and justice, are different. The city is moderate and just because, in some sense, everyone in it is moderate and just.1

Wisdom and courage follow what I will call the predominant part rule: the city has virtue V because the relevant predominant part of the city has the virtue V. Justice and moderation follow what I called the part-whole rule: the whole city has virtue V because all of its parts (the individual members) of the city have virtue V.

Main points

These are the things you should know.

  1. What are the parts of the city called?

  2. What are the parts of the soul called?

  3. What is the difference between wisdom and courage, on the one hand, and moderation and justice, on the other hand, as virtues of the city?


Plato. 1997. “Republic.” In Complete Works, edited by John M. Cooper, translated by G. M. A. Grube and C. D. C. Reeve. Indianapolis, IN: Hackett Publishing Company.

  1. If you are unsure of what the difference between moderation and justice is, you’re in good company. I can’t figure it out either. They are, at least, very close. Fortunately, nothing much turns on our ability to separate them so we can let it go.↩︎