Adeimantus wants to know how in the world Socrates can defend creating a city like this where none of the things that make people happy are available or possible: gifts, wealth, relaxation, parties, travel, etc.
Socrates responds that Adeimantus is thinking about happiness in a way that is too narrow. Their city will be the happiest because they are interested in what will make the most number of people happy; they're not interested in just a particular happy few. Socrates says that it's just like painting a statue: the whole statue will be beautiful if things are painted as they should be. If someone only wanted the eyes to be as beautiful as possible and put lots of weird colors on them, they would no longer look like eyes, and the beauty of the entire statue would be ruined.
This city will have true guardians who actually care about the city. The rulers of most other cities just care about having lots of money and parties, which is why so many other cities are miserable.
Wealth and Poverty
Socrates describes how both wealth and poverty are the enemies of productivity, since they create either laziness or poor craftsmanship. They all agree that the guardians should be careful to make sure that the city suffers from neither of these conditions.
Adeimantus is worried, however, that their republic will be at a disadvantage in waging war if they have no wealth and other cities do. But Socrates says this isn't an issue at all, since their republic will be rich in wisdom, a far more important aspect of war than money. He even bets that their republic could take on two other cities.
Adeimantus seems mostly persuaded, but he's still worried about the ability of other big cities to accumulate wealth and power. Socrates then takes issue with the fact that Adeimantus is even thinking about these places as "cities." After all, they are (or will soon be) so large, bloated, and overpopulated that they really would amount to multiple cities. To avoid this problem in the republic, Socrates recommends charging the guardians with the task of keeping the city at an exact size, neither too large nor too small.
This fits in, Socrates says, with the city's overall goal of keeping things moderate and appropriate to what they are. If children, no matter what group of people they are born into, appear to have the qualities of a different group of people, they will be relocated so that "friends have all things in common" (423e).
If the guardians do their job, things in the city should just follow a nice, regulated cycle.
More on Education
Socrates and company still need to be particularly cautious about regulating those poets and making sure that all new music fits the rules. Socrates thinks this is something particularly important, since music is kind of seductive. On top of that, young children are totally impressionable, so if they aren't educated well right from the beginning, they're pretty much doomed.
The benefit of a good early education, however, is that fewer details of adult behavior will need to be regulated: everyone will be a virtuous and good citizen already. In fact, Socrates thinks you can only effectively regulate education, not specific behaviors.
As a result, they all agree that legislating trade and commerce is not necessary, since virtuous people will naturally conduct themselves honestly. Socrates talks about how foolish people are who think that laws and legislation, like drugs and medicines, are the best cure for bad behavior. Really, laws and legislation are useless, since the only way to prevent bad behavior is good education.
Socrates compares the task of men trying to fix a bad republic with more and more laws to Hercules fighting the Hydra, the monster that produces two new heads for every one cut off. Laws just end up producing more bad behavior.
So, they agree that they don't need to come up with any more legislation. They also agree to leave the issue of religion and religious practices to the enlightenment of the god Apollo.
Back to Justice in the Republic (Finally)
Socrates thinks that now that they've set up this imaginary city, they can try and figure out where in this city justice exists.
They agree that since they've created a city that is perfectly good, it is also, by definition, wise, courageous, moderate, and just. What Socrates recommends they do is try to identify where each of these qualities lies. After that, justice will be left over, so they'll know where and what it is.
First, they guess where wisdom might be found in the city: in the guardians who have the greatest knowledge. This knowledge isn't specific knowledge—like the knowledge of carpentry, for example—but a more general kind of knowledge about how to care for the city as a whole. They also agree that the guardians possessing this knowledge will be a very small in number—unlike those who know a lot about things like carpentry, who will be many in number.
Next, they consider courage and decide that this is located in their soldiers. But the kind of courage Socrates is interested in isn't just about not being afraid. Socrates sees courage as persevering in your convictions. He suggests that with the right education, the soldiers will be brave because they are certain of what's right. He compares this process to the process of color dyeing, in which you have to treat the fabric first to make sure the color doesn't wash out.
Then they think about moderation. They decide that moderation involves ordering and mastering desires and pleasures. They agree that their city has been designed on just this principle, since the guardians act as masters over the rest of the population. But since both the guardians and the citizens are in agreement about how the city should be run, it's clear that moderation, unlike wisdom and courage, exists throughout the whole city, not just in certain parts. Moderation makes everyone, weak and strong, work together.
It's the moment of truth, since now they have to discover where justice exists in the city. It seems like it might be a difficult journey.
Suddenly, Socrates realizes what they've been missing. He says it's been right in front of them this whole time: justice exists in the principle they established in the beginning, in which each person would excel at the single thing for which they are most suited. In this way, justice is kind of like the virtue of minding your own business.
Justice is also the principle that enables all the other virtues of the city— wisdom, courage, and moderation—to exist and be preserved.
Socrates explains that one way of coming to this conclusion was by thinking about which of the four virtues of the city was most important. He realizes that the city was best served by the fact that everyone knew his or her place.
Furthermore, he thought about how in the area of law and judgment, justice was also crucial because it ensured that everyone was given what was already theirs.
What's important for the smooth functioning of the city is exactly this organization based on natural capability. It wouldn't be too disruptive if various craftsmen switched jobs, just as long as the jobs got done. But it would be incredibly disruptive if classes switched places, so that a solider tried to build houses and a house builder tried to fight.
Here, for the first time, Socrates clearly lays out the three classes that will exist in this city: a general class of craftsmen, a class of soldiers, and a class of guardians.
It's agreed that in the city, justice will consist of everyone doing his or her job, while injustice will consist of everyone failing to do so.
Justice in the Individual
Socrates wants to go way back to the problem that started this whole conversation, which is what justice looks like in an individual. He hopes that the way justice functions in a city will be a good model for how it functions within a single person.
Since justice in the city is linked to the neat organization of three classes, Socrates needs to find the equivalent of those classes within one person. What he proposes is that there are three parts of a single soul that need to work together harmoniously for there to be justice.
Glaucon thinks this is an important idea and wants to explore it further.
Socrates suggests that a city must have the three categories of people because three distinct drives—a drive for procreation and food, a drive for spirit, and a love of learning—are distinct parts of human nature itself.
What Socrates wants to know now is whether all our actions come from the exact same part of ourselves or if there are three distinct parts that each govern their respective qualities and actions.
In order to answer this question, the group first needs to establish a basic understanding of how parts and wholes operate. Socrates wonders whether something can ever do one thing and the opposite thing at the same time (for example, to be still and to move at the same time). To figure this out, he uses the example of a person who is standing still but waving his arms. He says that we wouldn't think of this as oppositional; we'd think that this person had two distinct parts, one of which is moving and one of which is still.
It seems they've established that opposites can never exist in the very same thing at the same time, so now Socrates wants to figure out a bit more about opposites in the soul. He imagines that the soul is capable of two opposite motions: desiring (bringing in) and not desiring (thrusting out).
Socrates imagines that the most intense desires the soul feels are hunger and thirst. And even though there can be differences in exactly how the soul wants to satisfy those desires (maybe I want some water, but you want a strawberry smoothie), thirst will always be a desire for a drink (no one gets thirsty for some chicken fingers).
Socrates then wonders about knowledge and suggests that there is general knowledge, which aims at learning in general, but there are also specific kinds of knowledge. That means that knowledge about sickness and health, for example, is called medicine. It's a specific kind of knowledge; it's not knowledge in general. Socrates compares this to thirst being only about drink.
What Socrates really wants to understand, he reveals, is why people don't always act on their desires—why, for example, it's entirely possible for someone thirsty not to drink. Because they agreed before that a certain thing can't do two opposite things, it's clear that it doesn't make sense to say that "thirst" can hold someone back from drinking.
The Three-Part (Tripartite) Soul
Socrates suggests that something separate from thirst holds the person back, and that this is something calculating and rational.
Here's where it gets real, so perk up those ears. Socrates claims that the soul has two distinct parts: 1) a rational, calculating part and 2) a desiring, irrational part.
But remember how the republic has three, not two classes? Well, if we want these models to nicely align (and Socrates says we do), we have to deal with the fact that one part is missing. Socrates says it's the spirited class (soldiers) and wonders if the spirited quality should be seen as just an aspect of the rational or irrational part or if it should be given its own distinct part of the soul.
Socrates imagines that most people associate this spirited quality with anger, which makes everyone think that maybe the spirited class is just another part of the desiring, irrational part of the soul. But Socrates points out that anger can be a calculated and rational reaction as well; this explains why people get angry at themselves for doing something they know they shouldn't. This is a good quality.
Glaucon adds that spirit seems to be very prevalent in children, sometimes without either of the other parts of the soul—so they all agree that since spirit can either align itself with desires or with rationality, it ought to be its own third part of the soul.
Since their city has offered a nice model for thinking about the individual soul, Socrates turns toward the issue of just behavior. He believes that here, too, the model of the city will be useful.
Just as the city was wise, courageous, moderate, and just, so too must the individual soul be. Also, the city was just because each class of people minded their own business, so it follows that the just person is someone who keeps each part of his or her soul minding its own business.
The soul should be organized like the city, so that, just as the guardians rule the city, the rational and calculating part of the soul should rule, while the spirit, like the obedient soldiers, should help the rational part out.
Socrates imagines that a good education of music and athletics (like the one they've already described) will suit the individual very well and make the rational and spirited parts of the soul able to govern the third, irrational part. They will need to make sure that the irrational part never gains control. In particular, they want to always check the irrational part of the soul's desires for money and superficial pleasures.
The other qualities of the good city follow. People will be courageous if their spirited parts follow the guidance of their rational parts; they'll be wise if their rational parts know what is most beneficial for the whole body; and they'll be moderate if all three parts of their souls work together in harmony.
Socrates believes they've constructed a perfectly just man and suggests that knowing how this man operates would make it hard to believe that he would do anything unjust: no theft, betrayal, adultery, or irreverence.
The reason Socrates thinks the just man would never do these things is that each part of his soul is minding its own business and doing what it does best.
Socrates then reminds the group that when he speaks of things "minding their own business," he's really only speaking of an internal action. He doesn't literally mean that a shoemaker should absolutely only think about shoes, for instance. The just man will set his own self and home in such good order that he can, with rationality and good intention, turn his mind to various topics: money, politics, etc. He can do this because he can trust in the harmony and good judgment of his own soul.
Injustice in the Individual
Now that it seems they've conclusively discovered what justice means and where it comes from, Socrates wants to consider injustice.
Since order and harmony in the soul lead to justice, it follows that injustice involves some kind of disunion, which Socrates images as a kind of rebellion.
In this rebellion in the soul, all the parts of the soul are meddling in places they shouldn't, and parts that shouldn't be in control are trying to take control.
Socrates compares justice and injustice to health and sickness. He says that just as health is when the body is ordered and functioning according to nature, so too is justice when the soul is ordered and functioning according to nature. The opposite is true for sickness and injustice, both of which involve a violation of a natural order.
Virtue is therefore like health and beauty, while vice is like sickness and ugliness.
Even though they've established quite a bit about virtue and vice, Socrates still wants to definitely show that injustice isn't just bad—it's also unprofitable.
Glaucon thinks this is kind of silly: they've so clearly shown that justice is natural, so how could anyone profit while living contrary to nature?
Socrates agrees it's silly but thinks they ought to do it, anyway. He says that while virtue has only one form, vice comes in all kinds of forms. (It's kind of like that first line from Tolstoy's Anna Karenina.)