How we cite our quotes: Stephanus pagination (the standardized way in which every text of Plato is divided). Every edition and translation will have this pagination in the margins.
Quote #4
"If we should watch a city coming into being in speech... would we also see its justice coming into being, and its injustice?" (369a)
In this famous Eureka! moment, Socrates explicitly lays out the primary goal of imagining a city: to discover the meaning and origin of justice.
Quote #5
"In the next place, get yourself an adequate light and look yourself... whether we can somehow see where the justice [in the city] might be and where the injustice..." (427d)
Using the metaphor of light and exploration, Socrates imagines that he and his philosophical pals need to search through their city looking for that elusive thing—justice.
Quote #6
"Well, then, my friend... this—the practice of minding one's own business—when it comes into being in a certain way, is probably justice." (433b)
Socrates imagines that justice is a principle not so much of fairness but of just doing your own thing. Did you see that one coming? Of course, by "doing your own thing," Socrates doesn't mean that you should just go out and do whatever you want; he means that everyone has some innate qualities or "business" that they should develop and put to unhindered use.