Political Philosophy Spring 2024

Glaucon’s Challenge


Plato’s goal in the Republic is to answer Glaucon’s challenge. The challenge appears to be straightforward. Socrates has to show that justice falls into the category of things that are valued both for their own sake and also for what comes from them.

Glaucon himself makes the case for thinking that justice belongs to a different category of things, namely, the ones that are valued only for what comes from them. Being just is like taking medicine or engaging in unpleasant physical training: if you could get the results you wanted without it, you would not do it (357).

I want to discuss two questions about Glaucon’s challenge.

  1. Why do the participants in the dialogue all agree that Glaucon and Thrasymachus are basically saying the same thing?

  2. How does Glaucon characterize an unjust person?

Thrasymachus and Glaucon

Thrasymachus is a bit of a mess. Sometimes he says that justice is something that the strong impose on the weak; that is what he means when he calls justice the advantage of the stronger. Other times he says that justice is a constraint that the strong ignore; that is what he means when he calls justice another’s advantage. He never really puts it all together to give a clear statement of what he believes.

Even worse, Socrates’s refutations of Thrasymachus are not much better. At best, they are more clever than convincing. Thrasymachus gives up but only because he is outmatched. Neither he nor the reader understands why Socrates is right.

I suspect Plato did this on purpose. He thought that people like Thrasymachus were incoherent and he had doubts about Socrates’s way of arguing. So if you are thinking you must be missing something, you might reconsider. It’s a mess because the author wanted it that way, not because there is a deeper meaning that you cannot discover.

In any event, none of this matters for our purposess. We are not going to try to figure out exactly what Thrasymachus is saying or exactly how Socrates’s arguments work. The figure we care about the most is Glaucon. So if you are feeling overwhelmed in the second half of Book I that is both normal and not really a problem. You just need to get a feel the kind of thing that Thrasymachus is saying. Don’t sweat the details.

One thing we do care about is how Glaucon’s position is like Thrasymachus’s. Here is why I think that is a question worth answering.

Thrasymachus portrays justice as a fraud. In theory, there is a distinction between might and right and justice applies equally to all. But in practice, justice is either imposed by the strong on the weak or it is a constraint that the weak respect and the strong ignore.

Glaucon, by contrast, describes justice as a reasonable looking deal. People found it impossible to get along without rules, so they made some rules, and that’s what we call justice.

Those two stories look quite different to me. But Plato treats them as being the same thing. Why?

What is an unjust person like?

I’m going to give away the end of the story here.

Glaucon characterizes the unjust person in two different ways.

  1. As someone who is exclusively concerned with outdoing others and always acquiring more of anything (359c). On this way of understanding injustice, unjust people are competitive or greedy (or both).

  2. As someone who is indifferent towards the rules of justice in pursuing his or her aims (362b-c). Here, unjust people are amoral concerning the means they use to achieve their ends but their ends are not necessarily competitive or greedy.

At the end of the book, Plato is going to argue that the life of the first kind of person is miserable. That person’s life is governed by what others do or by a mindless drive to acquire things. He will make a good case for thinking that this kind of life is empty and out of control. At least, I am persuaded.

However I am not convinced that Plato ever comes to grips with the second way of being unjust. Since that kind of unjust life seems much more attractive to me, I think it’s the one to beat. But I also think it is left standing at the end of the book.

I want to set that point up now. So let’s talk about the difference between 1 and 2.

Main ideas

These are things you should feel have an opinion about by the end of class.

  1. What is Glaucon’s challenge?
  2. How is it related to Thrasymachus’s attacks on justice?
  3. What is an unjust person like, according to Glaucon?


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.