My attempts at interpreting T.S. Eliot have been temporarily derailed, so I thought I might return to Republic and make some more comments about the meaning of Socrates' statement that he will "watch a city coming into being in speech."
The great danger of reading Plato (a danger that Socrates is keenly aware of) is that we assume that we already know what he is talking about. What makes Socratic philosophy so glorious is that this danger is itself the very subject-matter of all the dialogues. Thus the question "what is justice," which is ostensibly motivating the entire dialogue, both presumes that we already have some idea what we are looking for (that is, we have some correct opinion about the nature of justice) and that we nonetheless do not know what we are looking for (since we cannot look for what we already have). Thus Socrates dismantles the fine arguments of Cephalus and Polemarchus, arguments that are not incorrect (after all, we do generally say that it is just to "speak the truth and give back what we take"). Yet their definitions are incomplete, and they must be dismantled if they are to be properly reassembled into the appropriate dialectical whole.
The above sounds rather Hegelian, so we should point out the manner in which Socrates is engaging in something completely opposite from Hegel. One way of seeing the difference is to observe Socrates' deep reverence for the divine. We find in Phaedrus, for instance, Socrates expressing a fear of inadvertently offending the gods by speaking unjustly of the nature of love. Hegel interprets the daemon that speaks to Socrates as the voice of reason; we should not make this mistake as Hegel is purposely (but necessarily) misreading the dialogues. The practice of dialectic will lead to the knowledge of justice, not the creation of justice.