Not Exactly a Socratic Dialog
SOCRATES: Now, see whether you agree with me about this: if a carpenter attempts to do the work of a shoemaker, or a shoemaker that of a carpenter, or they exchange their tools or honors with one another, or if the same person tries to do both jobs, and all other such exchanges are made, do you think that does any great harm to the city?
SOCRATES: But I imagine that when someone who is, by nature, a craftsman or some other sort of moneymaker is puffed up by wealth, or by having [b] a majority of votes, or by his own strength, or by some other such thing, and attempts to enter the class of soldiers; or when one of the soldiers who is unworthy to do so tries to enter that of judge and guardian, and these exchange their tools and honors; or when the same person tries to do all these things at once, then I imagine you will agree that these exchanges and this meddling destroy the city.
CIPCON: Sounds implausible.
SOCRATES: So, meddling and exchange among these three classes is the [c] greatest harm that can happen to the city and would rightly be called the worst evil one could do to it.
CIPCON: That's ridiculous.
SOCRATES: That, then, is what injustice is. But let’s put it in reverse: the opposite of this—when the moneymaking, auxiliary, and guardian class each do their own work in the city—is justice, isn’t it, and makes the city just?
CIPCON: That’s the dumbest thing that you've said today, and that's clearing a very high bar. You could really use a course in elementary logic.
Not Quite Readings in Ancient Greek Philosophy: From Thales to Aristotle (p. 303). Hackett Publishing Company, Inc.. Kindle Edition.