I think the structure of the Republic is vitally important to understanding its meaning. Every dialogue, and especially this one, is an organized whole, and none of the parts will be fully understood if the nature of the whole is overlooked. Perhaps a first clue towards discovering this structure is in the obvious point that the dialogue is a drama, a type of play. If I were to divide Plato’s Republic into five acts as in a play, I would carve it this way:
ACT I: Exposition and introduction to the question concerning the nature of justice (Book I to Book II, ending at 367a)
ACT II: Building the “City in Speech” and the discovery of virtue (remainder of Book II to Book IV)
ACT III: The Philosophical Core (Books V, VI, & VII)
ACT IV: The Degradation of the City (Books VIII & IX)
ACT V: Epilogue (Book X)
This is the “ten-thousand foot view” of the dialogue. From that perspective it is possible to notice that Plato’s five-act play follows Freytag’s pattern of a dramatic arc: (i) exposition, (ii) rising action, (iii) climax, (iv) falling action, and (v) denouement. The “inciting incident” would be the question of whether the just life is better than the unjust life (367e), and the “resolution” would be the agreement that the just life is indeed better (end of Book IX). Aristotle’s three stage pattern is also applicable if we combine Act I and II to constitute a protasis, leave Act III alone as the epitasis, and combine the remaining books to produce the catastrophe. The value of this foray into poetics is twofold for the interpreter of the Republic: (1) to take advantage of the parallelism between Acts I & V and Acts II & IV, each pair of which can be studied as a diptych to examine the same theme from differing but symmetrical points of view. (What, for instance, does the Myth of Er that ends Book X have to do with Book I’s opening scene in the house of Cephalos? Such a question can only be asked if the symmetry is noticed.) And, (2) to attend to the climax as the core teaching towards which the rising action converges and the falling action diverges.
The Republic, I think, has two centers. One is a geometrical center, the other is the erotic center, i.e., focus of aspiration. The geometrical center is at 473c-d, the pronouncement that “political power and philosophy must entirely coincide.” The placement is exact. If one were to transcribe the the entire Republic on a single long page, without any breaks between the lines, and then fold the paper in two, top onto bottom, the crease would fall on this passage! What I am calling the erotic center is the Divided Line analogy at the end of Book VI (509d – 511e), flanked on each side by the Sun Analogy and Cave Allegory. The ultimate subject matter, the Good/agathon, is not really present in the dialogue itself, only indicated by the liturgical posture effected by it.
Next, each of the Acts can be parceled into distinct scenes. My division of the central Act III, for instance, would have at least five scenes, with a division something like this: (i) the “Female Drama,” with its three “waves” building up to the discovery/birth of the Philosopher ruler (opening of Book V to 474b); (ii) the attempt to distinguish the philosophers from the “philodoxers,” which includes the central knowledge/opinion discussion (474b – 504d); (iii) the search for the Good/agathon, which includes the erotic center as described (504d – end of Book VI); (iv) the Cave Allegory and the “way back down” (beginning of Book VII – 521b); (v) the education of the philosopher (521c – 541b).
Finally, there are also several discontinuities in the Republic that should attract attention, for the same reasons that disruptions in the metrical patterns of poems are often indicators of moments of special interest:
1) The ending of Book I to the beginning of Book II, marked by the sentence that begins “When I had said this, I thought I had done with the discussion…” (357a), in which a certain dissatisfaction with Socrates’ “victory” over Thrasymachus is registered and the dialogue is forced to take a new turn.
2) The ending of Book IV to the beginning of Book V, in which the discussion seems about to turn to a discussion of the types of cities (a discussion that finally picks up at the beginning of Book VIII) and yet is turned off course again by an interruption by Socrates’ interlocutors. In fact if you were to rip out of your text the entirety of Books V, VI, and VII (and cut out the first few sentences of Book VIII that announce the return to where Book IV left off), it is doubtful that anyone reading the edited text would notice the omission. It is exceedingly strange that the beating heart of a text, its very center, could be excised without leaving a mark!
3) The discussion of imitation/mimesis at the beginning of Book X seems out of place. What is it doing there rather than in the discussion of music/poetry in Book III?
To conclude: in the Phaedrus dialogue, Socrates compared an account/logos to a living animal, that must be butchered at its natural joints (265e – 266a). Although I may have nicked the bone in places, I am certainly confident in both the large divisions (I am not the first to see them where I have) and the discontinuous exceptions that prove the rule. Wholes, as I have mentioned before in this blog, make possible the felt absences that provide impetus to Plato’s teaching. I do not believe any of my own discoveries in the Republic would have been possible without careful attention paid to its structure.