"The safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato."
— Alfred North Whitehead
Platōn of Athens was a Greek philosopher: the first Western philosopher, in fact, from whom we have complete surviving works. His importance is neatly summed up above. He is also the major source for info about his mentor Socrates, of whose life he wrote many Real Person Fics. Aristotle studied under him.A central concept of his philosophy was the theory that everything we perceive in reality and every idea we have is an imperfect representation of an ideal, archetypal, unchanging Form, the nature of which can only be understood through reason. The Platonic Cave originated as a metaphor for the relationship between our actual perception and this more fundamental reality and as an illustration of another metaphor, the divided line, itself a simile for our perceptual progression.His works contain the Ur Example of Utopia and Atlantis, and the Trope Namer for Platonic Cave. (And, sadly for many lovesick folk, he was also the trope namer for "Platonic Relationship.")
It is, however, essential to remember that democracy was very different back then. The power of the Athenian assembly was not restricted by rules or a system of checks and balances. On a moment's whim, a majority of active citizens could decide anything, no matter how stupid and/or immoral (and in fact, stupid decisions taken on the spur of the moment were partly responsible for Athens losing the Peloponnesian War).
Plato also criticized all existing forms of governments; all of them were imperfect, none of them were able to deliver what most of the people who lived under them really wanted, and to this day this is still largely true. What Plato advocated for, however, is a system much closer to what we would call a representative form of government, or a Republic, which is a form of indirect democracy. Plato would also have been very appreciative of the modern systems of checks and balances, as well as the modern constitutional forms of government, all of which derive at least in part from his writings.
Due to the Dead: Socrates jokes about in Phaedo: to bury him, they would have to catch him. They will only bury his body.
Be of good cheer, then, my dear Crito, and say that you are burying my body only, and do with that whatever is usual, and what you think best.
Good Republic, Evil Empire: A common theme in his political writings. Plato considered a government which obeyed the rule of law and followed wisdom to be the best of all states, run by merit and working for the good of all people. By contrast, Plato's description of the evils of tyranny are shocking and prescient.
Hobbes Was Right: He did not approve of direct democracy as it existed in his day, and believed the best form of government to be, essentially, the rule of the most enlightened and wise men of society. Of course, he predated Hobbes by a couple thousand years, and wouldn't have agreed with him on many other things (like the possibility of finding the wise men of society, to say nothing of their differences in the meaning of the highest good).
He did, however, prefer the evils of democracy to the evils of tyranny — which is exactly what you'd get if you screwed up the absolute-rule thing.
Logic Bomb: (See the Anvilicious entry on the YMMV page) If you could explain it, they would already understand in the first place, but you have to explain it to them so they can learn to understand (it could be argued that as it was meant for his students anyway this was its purpose in the first place).
Mood Whiplash: Countless instances of 'By Zeus, you're Right, Socrates!... I think.' in his dialogues.
Speech-Centric Work: Many of his works, such as The Republic, are presented as dialogues between two characters.
Utopia Justifies the Means: Played straight in Republic, where Socrates discusses what lies to tell to lower classes, and why and how people should be "removed" if they are a problem. He also expresses an extreme distaste for liberty, free speech, and artistic freedom (see Democracy Is Bad above).
This one requires a great deal of explanation. Plato was never against liberty or intellectual/artistic freedom in itself, but he was very aware of the susceptibility of people to be persuaded by irrational appeal. Then and now, many people have been swayed by dictators who talk a good talk and have plenty of artful propaganda behind them. The ability of art and speech to be turned to evil ends is what Plato feared, hence his suspicion of artists and ideas on creating morally-upright stories for the young. Of course, much of what Plato said in his dialogues was not necessarily what he actually advocated, but was part of an extended thought exercise. His Republic in particular was a dialogue about justice, not a blueprint for a perfect state. To put it more simply, Plato preferred a society in which rational debate and intellectual substance would guide public policy, not hype, appearance and style. Even to this day, many people complain that getting elected has as much to do with making oneself look good and making one's opponents look bad, something Plato would have hated.
More to the point, there are many aspects of modern society that would make Plato proud, such as rating systems for movies and television, censorship of certain words on public TV, and fairy tales, which are watered-down versions of older, much harsher and often morally questionable stories.
Yes-Man: Since the dialogues which Plato wrote are basically just author tracts, Plato has Socrates spout off very extensive lists of premises that are simply immediately accepted by everyone present. Characters can go on for pages only saying, "Yes," "Certainly," "Very true," and "No doubt," while Socrates talks for paragraph after paragraph.