At this point Thrasymachus changes his tack. As Socrates is trying to sum up the main argument, he asks, “Do you say that complete injustice is more profitable than complete justice?”
“Indeed I do, and I have explained why.”
“Well then, how do you classify them? Is one of them a virtue, the other a vice?”
“Of course.”
“So justice is a virtue, injustice a vice?”
“That’s likely,” Thrasymachus answers sarcastically, “my friend, since I maintain that injustice is profitable and justice is not.”
“What then?”
“The opposite.”
“Justice is a vice?”
“No, but ingenuous naivete.”
“Do you call injustice depravity?”
“No, but sagacity.”[28]
Socrates recognizes that Thrasymachus has reversed his argument again. Just when the philosopher is in a position to refute the sophist by showing that justice could not be the advantage of the stronger because it sought the advantage of the weaker, the sophist changes his ground. Justice may be like a craft, but it is injustice that is desirable and praiseworthy. Injustice confers the greatest benefits. To refute this view, Socrates cannot simply reveal the character of virtue, but he must show that justice is more profitable than injustice.
Socrates now asks Thrasymachus to consider how the just and unjust person act with respect to others. The just person will try to outdo the unjust but not the just. The unjust person will try to outdo both the just and the unjust, as Thraysmachus agrees. But will a musician try to outdo a musician, a doctor another doctor? To extend Socrates’ argument, imagine a person with the art of arithmetic. He says that two plus two is four. To outdo him, the unjust person must say that two plus two is five, or three, or some other number. But he cannot maintain his unjust arithmetic for long without getting his sums wrong and exposing himself as a fraud. Socrates has used the Craft Analogy again to reveal the weakness of injustice. Thrasymachus blushes.
Socrates turns to a second argument. Will a city, he asks, or any group of people be stronger if its members practice justice or injustice? If the citizens of a city practice injustice, won’t their interrelations degenerate into strife, enmity, and civil war? Even a band of robbers has to expect its members to behave fairly among themselves in order to execute a robbery. Imagine, in a modern setting, a group of bank robbers in which keeper of the guns doesn’t bring ammunition, the bag man doesn’t bring bags, the driver of the getaway car doesn’t put gas in the tank, and the lookout man goes to sleep. Even to rob a bank, there must be a minimal kind of justice among thieves. Injustice is inherently self-defeating, while justice builds a strong community.[29]
Thrasymachus’ might-makes-right philosophy is now completely refuted. Insofar as justice is a virtue, it is like a craft that benefits the weaker. Even if one rejects the appeal to virtue as naive, it can be shown that injustice is inherently weak. A craft, being based on scientific knowledge, is stronger than any competing practice. Any association based on injustice will generate inner conflict and defeat itself, whereas an association based on justice is inherently cohesive and self-sustaining. Even to the small degree injustice can succeed, it is parasitic on justice.
Thrasymachus the bully advocating a bully’s ideology is disarmed and reduced to sullen agreement.
Socrates makes one final suggestion. Everything has a function: a horse, an eye, a knife. These things cannot function properly without a corresponding excellence or virtue, for instance sight for an eye, sharpness for a knife. Does the soul then have a function, perhaps ruling, planning, living? Yes. Will soul then have an appropriate virtue? And will that virtue not be justice? So a just soul will live well and be happy, and an unjust soul will live badly and be wretched. So even at the level of the individual soul, considered apart from society and the polis, justice is essential for living the good life. “Accordingly, my dear Thrasymachus, injustice is never more profitable than justice.”[30]
But, just as it appears Socrates has completely validated justice as doing good in his conversation with Polemarchus, and vindicated justice against injustice in his conversation with Thrasymachus, he realizes that he has failed to do what he set out to do, to define what justice is. Without knowing this, we cannot be sure that anything else we have said about it is right. We need to start all over again.
How can Socrates, who bases virtue on definitions that seem to be always just out of reach, defeat the ideology of imperialists and the rationalizations of immoralists?
[28].Plato Republic 348b-d.
[29].Plato Republic 351a-352d.
[30].Plato Republic 352d-354a.