With the exception of a set of letters of dubious provenance, all of Plato’s surviving writings are in dialogue form, with the character of Socrates appearing in all but one of them. His 36 dialogues are generally ordered into early, middle and late, though their chronology is determined by style and content rather than specific dates.
The early dialogues offer a deep exploration of Socrates’ dialectic method of breaking down and analyzing ideas and presumptions. In the “Euthpyro” Socrates’ endless questioning pushes a religious expert to realize that he has no understanding of what “piety” means. Such analyses pushed his students towards grappling with so-called Platonic forms—the ineffable perfect models (truth, beauty, what a chair should look like) by which people judge objects and experiences.
In the middle dialogues Plato’s individual ideas and beliefs, though never advocated outright, emerge from the Socratic form. The “Symposium” is a series of drinking-party speeches on the nature of love, in which Socrates says the best thing to do with romantic desire is to convert it into amicable truth-seeking (an idea termed “Platonic love” by later writers). In the “Meno,” Socrates demonstrates that wisdom is less a matter of learning things than “recollecting” what the soul already knows, in the way that an untaught boy can be led to discover for himself a geometric proof.
The monumental “Republic” is a parallel exploration of the soul of a nation and of an individual. In both, Plato finds a three-part hierarchy between rulers, auxiliaries and citizens, and between reason, emotion and desire. Just as reason should reign supreme in the individual, so should a wise ruler control a society. Only those with wisdom (ideally a sort of “philosopher-king”) are able to discern the true nature of things. The experiences of the lower tiers of the state and of the soul are—as Plato’s famous analogy has it—related to true knowledge the way the shadows on the wall of a cave are related to, yet wholly different from, the forms that cast them.
Plato’s late dialogues are barely dialogues at all but rather explorations of specific topics. The “Timeaus” explains a cosmology intertwined with geometry, in which perfected three-dimensional shapes—cubes, pyramids, icosahedrons—are the “Platonic solids” out of which the whole universe is made. In the “Laws,” his final dialogue, Plato retreats from the pure theory of the “Republic,” suggesting that experience and history as well as wisdom can inform the running of an ideal state.