Plato identifies justice in the city with the help of two premises.
The explanation of why the city is just involves first explaining why it has the three other virtues. The remaining features of the city explain why it is just.
Plato did believe that the city has the virtues he lists because at least some of its individual members have those virtues. Having virtuous individual members is a necessary condition for the city’s being virtuous.
However, having virtuous individual members is not a sufficient condition of the city’s being virtuous. This is because the virtuous members have to play particular roles in the city.
For example, it isn’t enough to have courageous auxiliaries. Rather, the auxiliaries have to play their role in defending the city. Suppose it were otherwise. Suppose the auxiliaries are as courageous as possible, but every time the Persians come to the city gates, the auxiliaries are ordered to stay in their barracks while the city elders surrender the town. Is that a courageous city? No. Does it have courageous members? Yes.
So what does Plato mean when he refers to the happiness of the city, as distinct from the happiness of the guardians (see p. 95)? Dan pushed us to address this question at the beginning of class.
I have to confess that I don’t know the answer. I don’t think that Plato thought of the happiness of the city as consisting only in the happiness of its members. He certainly didn’t think of the virtues of the city as consisting only in the virtues of its members. But, on the other hand, I’m not sure that I know what to make of the suggestion that a city could be happy in some way beyond the happiness of its members.
When Plato says that justice is everyone’s performing his role he seems to be changing the question, as Rob pointed out. We got into this because justice seemed to involve concern for others. Since that is so, there is a question about why an individual would find it anything other than second best for himself. How does this stuff about roles have anything to do with that question?
Here’s an analogy that might help. When Plato says that justice is everyone’s performing his role, it’s like a doctor saying “this virus is what makes these symptoms appear.” In this case, the “symptoms” are the behaviors characteristic of justice: not sneaking into the king’s house, seducing his wife, killing him, and taking over the kingdom, for instance.
What makes a person just, what makes a person behave in honest, non-sneaky, non-seductive, non-killing, and non-taking-over-kingdom ways, is that the parts of his soul play their correct roles.
What makes being just good, in turn, is what makes having your soul in order good. I think that’s what he’s trying to say.