Primers › Philosophy

Plato

Plato lived in Athens from about 428 to 347 BCE. He was Socrates’ student and Aristotle’s teacher [1]. The last primer ended with Socrates drinking hemlock in 399 BCE. Plato watched that happen, and most of what we know about Socrates comes from what Plato wrote afterward [2], [3].

This primer follows episode 4 of Philosophize This! [2] and checks it against the Stanford and Internet Encyclopedias of Philosophy and against Plato’s own text, the same way the Presocratics primer does. It covers five things:

1. Why Plato is so well known. He was a great writer, and that matters as much as his ideas.
2. Why Socrates is in almost everything he wrote.
3. Platonic love. Two speeches from the same dinner party: one says love is looking for the other half you lost, and the other says love is a climb toward beauty itself.
4. The allegory of the cave and the world of Forms. Plato’s picture of what’s really real and how we could ever know it.
5. Plato’s ideal city. How he’d raise good citizens, why philosophers should rule, and his ranking of governments from best to worst.

A few terms come up throughout:

• Dialogue. Plato wrote philosophy as conversations between characters, like scripts. Each one is called a dialogue and usually named after a character, like the Meno or the Phaedo [3].
• The Symposium and the Republic are the two dialogues this primer leans on most. The Symposium is about love. The Republic is about justice, in a person and in a whole city, and the cave is in it [3], [1].
• Form (capital F, also translated Idea). Plato’s name for the single perfect, unchanging thing that many imperfect things have in common. Lots of things are beautiful, and the Form of Beauty is beauty itself, the thing they all share [3]. A Form is not a shape here. The section on the world of Forms explains it properly.
• Eros is the Greek word for passionate or romantic love, usually translated “love.” It’s where “erotic” comes from [4].

Plato could write

The podcast opens with Alfred North Whitehead’s line that all of Western philosophy after Plato is a set of footnotes to Plato [2]. Part of the reason is that Plato’s books survived and his teachers’ didn’t. Socrates wrote nothing, and the Presocratics survive only as fragments other people quoted. Plato’s dialogues came down to us intact [3].

The Stanford encyclopedia calls Plato “one of the most dazzling writers in the Western literary tradition,” and says the subject of philosophy, as people usually think of it, “can be called his invention” [3]. The podcast says many historians rank his writing above Homer’s [2]. That’s a judgment call rather than a fact, but nobody disputes that he could write. An old story says he started out writing tragedies for the theater and burned one after hearing Socrates talk. Nobody knows if that’s true, but the Internet Encyclopedia says there’s no question of his “mastery of dialogue, characterization, and dramatic context” [1].

The dialogues read like short plays. Most open somewhere specific, like a prison, a rich man’s house, a drinking party, or a walk outside the city walls on a hot day. The people talking are mostly real Athenians with real reputations, and they have personalities [3]. A conversation starts out about something ordinary and drifts into a hard question about justice or love or knowledge [2].

Plato never speaks in his own voice in the dialogues, so he never just tells you what to believe [3]. Characters make arguments, other characters push back, and plenty of the dialogues end without an answer. The encyclopedia says this draws readers into thinking the problem through for themselves, and that the characters and conversation make the ideas interesting enough to reach a wider audience. Between that and the quality of the writing, Plato is often thought of as the ideal author to start philosophy with [3].

Socrates in nearly every dialogue

Socrates is the main speaker in most of Plato’s dialogues. He’s completely missing from only one, the Laws, which was one of the last things Plato wrote. In a few other late ones, like the Sophist, the Statesman, and the Timaeus, he’s there but someone else does most of the talking [3].

The podcast’s explanation is that Plato was deliberately typecasting Socrates as the wise man in every story, the way an actor gets known for one kind of role, so that Socrates would be remembered that way [2]. Plato did have reasons to want that. Athens had executed Socrates as a corrupter of the young, and Plato’s account of Socrates’ relationships with young men in the Symposium reads as a defense of him [4]. Plato called Socrates “the justest man alive,” or at least the Seventh Letter does, and scholars disagree about whether Plato wrote it [1], [3].

The encyclopedias add two things the podcast leaves out:

• Plato wasn’t the only one. After Socrates died, several of his followers wrote conversations starring him. Xenophon’s survive, and fragments of others do. Writing “Socratic discourses” was a genre, and Plato was arguing with the other writers about who Socrates really was [3], [1].
• Socrates turns into Plato. Scholars split the dialogues into early, middle, and late periods. In the early ones Socrates asks questions about ethics, says he doesn’t know the answers, and leaves the other person stuck, which fits what we know of the real man. In the middle ones a character still called Socrates starts confidently teaching new theories about the soul and the Forms. Those are Plato’s ideas. He kept the name, and the encyclopedia says that let him show his debt to his teacher and borrow “the extraordinary prestige of the man who was the wisest of his time” [3], [1].

So the podcast’s point about immortalizing Socrates holds up, and it came at a cost. Making Socrates speak for Plato means we often can’t tell where Socrates ends and Plato begins, the same Socratic problem the last primer ran into [2], [3]. The podcast doesn’t think Socrates would have minded, since he never claimed to have fixed beliefs anyway [2].

Platonic love

The Symposium is set at a drinking party, which is what the word means. After dinner the guests take turns giving speeches about love [2], [3]. Seven people speak [4]. Two of the speeches are the famous ones, and they disagree.

Most of the speeches, Diotima’s included, have in mind love between an older man and a younger one, a relationship Athenian custom had its own rules for, called paiderastia [4]. Both speeches below still have something to say about love in general, and the first one explains why some people love men and others love women.

Aristophanes: looking for your other half

Aristophanes, the comic playwright whose Clouds had mocked Socrates [3], tells a myth that is half joke and half serious [2], [5]:

1. Humans used to be round. Each had four arms, four legs, and one head with two faces looking opposite ways, and moved by cartwheeling. (The podcast says two heads. The text says one head, two faces.)
2. There were three sexes: all-male, all-female, and half-male half-female. The male ones came from the sun, the female ones from the earth, and the mixed ones from the moon.
3. They were strong and proud enough to attack the gods. Zeus didn’t want to wipe them out, because then nobody would make sacrifices to the gods. So he cut each one in half, which made them weaker and doubled the number of worshippers.
4. Ever since, each half has been looking for the other half it was cut from.

The three kinds of original people explain three kinds of attraction. Halves of the mixed people are drawn to the opposite sex, halves of the all-female people to women, and halves of the all-male people to men [5]. When two halves find each other they don’t want to be apart for a moment, and they can’t explain what they want from each other. If a god offered to weld them back into one person, they would say yes. Aristophanes sums it up: “the desire and pursuit of the whole is called love” [5].

On this view love is about getting back something that was already yours. The podcast puts it as a quest to fill in what you’re missing [2]. It’s also where we get the phrase “my other half” [1].

Socrates: climbing toward beauty

Socrates speaks later. He says he learned everything he knows about love from a woman named Diotima, from Mantinea, and repeats her lesson [4], [5]. She answers Aristophanes almost directly. People say lovers are looking for their other half, she says, but we don’t love the half or the whole unless it’s good. People will even have their own hands and feet cut off if those have gone bad [5]. You love something because it’s good or beautiful, not because it used to belong to you [2].

From there she builds up a definition:

• Love wants the good, forever. Not just to have good things but to keep them always [5].
• We can’t have anything forever, because we die. So love turns into a drive to make something that outlasts us, which Diotima calls “giving birth in beauty” [4]. Some people have children. Others go after fame, or make something that lasts, the way Homer’s poems and Solon’s laws did [5]. The podcast compares these achievements to a peacock’s feathers [2].
• Beautiful people are where this starts, not where it ends. Loving a beautiful person is the first rung of a ladder.

The ladder goes like this [5], [4]:

Each step loves a wider kind of beauty than the one below it. The top step is the only one that can't change or die.

1. One beautiful body. You fall for one person.
2. All beautiful bodies. You notice that this person’s beauty is the same kind of thing as other people’s beauty, and the obsession with one body relaxes. The podcast says the hot person turns out to be “not as much of a rare Pokémon” [2].
3. Beautiful souls. You start to value a beautiful character over a beautiful body, enough to love a good person who isn’t much to look at.
4. Beautiful laws and ways of life, the things that shape good character.
5. Beautiful knowledge. Every field of study, and the “vast sea of beauty” across all of them [5].
6. Beauty itself. At the top you see a beauty that never grows or fades, isn’t beautiful in one way and ugly in another, and isn’t the beauty of anything in particular. Everything else that’s beautiful gets its beauty from it [5]. That’s the Form of Beauty.

Diotima says this is the life most worth living [5]. Beauty itself can’t leave you or die on you, the podcast points out, but it can’t love you back either, because it’s perfect and doesn’t need anything [2].

One common reading is that you use people as steps and kick the ladder away once you’re up. The encyclopedia argues against that. The lover still loves the person, just not obsessively and not only for their looks, so the beloved “will now still be loved” when their looks fade [4].

The two side by side

What “platonic” means now

Today “platonic” usually means a close relationship without sex. The dictionary keeps both senses: the everyday one, and “love conceived by Plato as ascending from passion for the individual to contemplation of the universal and ideal” [6]. Plato’s version isn’t sexless friendship. It starts with physical attraction and climbs past it. Plato did see sex as a degraded, wasteful use of love’s power, though, and thought love only got what it really wanted through philosophy [1].

The world of Forms

The love speech ends at beauty itself, a perfect beauty that isn’t in any one beautiful thing. That idea runs under nearly everything Plato wrote [3].

It starts with Socrates’ question from the last primer: what is courage, or justice, or beauty? Socrates wanted whatever all just acts have in common. Aristotle says Socrates looked for that common thing but Plato separated it. Plato decided it couldn’t be anything in the world around us, because everything around us keeps changing [7].

The podcast uses trees [2]. No two trees are the same. They have different bark, different leaves, a knot here and a missing branch there, and you still recognize every one of them as a tree. They share some “tree-y-ness.” (Plato used dogs, the podcast says.) Plato’s claim is that this shared thing is real, more real than any single tree, and it’s the Form.

Forms have a few features in common [3], [1]:

• One over many. There are many beautiful things and one Beauty, many equal things and one Equality. The many things get their names and their qualities from the one.
• Perfect. Every beautiful thing is beautiful in some ways and not others, or for a while and then not. Beauty itself is just beautiful, completely and always.
• Unchanging and eternal. They aren’t in space or time.
• Known by thinking, not by the senses. You can see a beautiful face. You can only think your way to Beauty.

The encyclopedia’s list of Plato’s most important Forms is abstract: goodness, beauty, equality, sameness, difference [3]. Trees and dogs make easier examples, but these are the Forms Plato cared about most.

This also answers the Presocratics’ big argument. Heraclitus said everything is always changing, and Parmenides said real things can’t change at all [2]. Plato takes both. The world our senses show us changes constantly, and the Forms never change [2], [1].

The allegory of the cave

Plato gives his own picture of all this in Book VII of the Republic, and it’s probably the most famous image in philosophy [7]. Socrates tells it to Glaucon [8]:

The fire's light passes over the carried figure and lands on the back wall. The prisoners can only face the wall, so the shadow is all they ever see.

1. The prisoners. People have lived since childhood chained in an underground cave, legs and necks fixed so they can only look at the back wall.
2. The shadows. Behind them a fire burns. Between the fire and the prisoners is a low wall, and people walk along behind it holding up statues of people and animals, like puppeteers. The prisoners see only the shadows of those statues on the wall. They give the shadows names, and they think the shadows are the real things. Prisoners who get good at guessing which shadow comes next win honors from the others.
3. Turning around. One prisoner is freed and made to turn toward the fire. It hurts his eyes, the statues look less real to him than the shadows did, and he wants to go back to looking at the wall.
4. Out of the cave. He’s dragged up a steep path into the daylight and is blinded at first. He gets used to it slowly. First he can look at shadows and reflections in water, then at the things themselves, then at the night sky, and finally at the sun.
5. Going back down. If he went back to his old seat, his eyes would be useless in the dark and he’d be bad at the shadow-guessing game. The other prisoners would laugh at him and decide the trip up had ruined his eyes, so nobody should ever go. They wouldn’t just refuse to follow him. If anyone tried to unchain them and lead them up to the light, and they could get their hands on that person, they would kill him [8].

The podcast’s version is close, with two small differences [2]. It suggests the freed prisoner would probably just turn back to the wall, but in the text he gets dragged out whether he likes it or not. And it skips the last step. Plato wrote it two or three decades after Athens executed Socrates for questioning people [8], [1].

What each part stands for

Socrates explains the picture himself: the cave is the world we see, the fire is the sun, and the climb out is the soul rising to the world of thought, where the last and hardest thing to see is the Form of the Good [8]. The encyclopedia lines the rest up with the passage just before it in the Republic [7]:

After the climb

The podcast says Plato thought a philosopher’s job is to work out the Forms of as many things as they can in their lifetime [2]. Each one changes how you see the everyday version. The podcast compares it to watching football next to a pro player. You’re both watching the same game, but the player sees the strategy and the small details that you miss completely [2]. Plato thought the philosopher who has left the cave sees everyday life that way.

That also makes him hard to talk to. The prisoners only know the shadows, so when he talks about what’s outside, they have nothing to compare it to. Plato puts him in court, still “blinking” and not used to the dark again, forced to argue “about the images or the shadows of images of justice” with people “who have never yet seen absolute justice” [8]. He knows what justice really is and they don’t, so they argue past each other, and he comes off looking ridiculous. Plato says that shouldn’t surprise anyone. Laughing at someone whose eyes are still adjusting after coming down from the light makes less sense, he says, than laughing at someone who has never left the dark [8].

Plato still doesn’t let him stay outside. Later in Book VII, Socrates says the people who have made the climb can’t be allowed to stay up there, however much they’d like to. They “must be made to descend again among the prisoners.” Once their eyes adjust to the dark, they “will see ten thousand times better than the inhabitants of the den,” because they know what each shadow is a shadow of [8]. In the Republic, those people go back down to rule the city. The podcast calls that kind of ruler a philosopher king [2], and Plato’s ideal city at the end of this primer covers why he thought they should rule.

So the duty runs both ways. Climb as high as you can, all the way to the Form of the Good, and then come back down and help the people who are still watching shadows, even if they don’t want your help.

How would anyone know a Form?

You can’t see a Form, so how would you know when you’d reached one? Plato’s answer, mainly in the Meno, is that you already knew it before you were born. The soul is immortal and saw the Forms before birth, and learning is really recollection, remembering what the soul already knew [3], [1].

His evidence is a scene where Socrates questions a slave boy who has never studied geometry [1]. Socrates never tells him the answer. He only asks questions, and the boy reaches new conclusions on his own [2]. For Plato, if nobody taught him, the boy must have been remembering.

The doubled square

The problem is easy to state. Socrates draws a square 2 feet on a side, so its area is 4 square feet, and asks the boy how long the side of a square with double the area, 8 square feet, would have to be [9].

1. Double the side? The boy says 4 feet, confidently. Socrates has him draw it. A 4-foot square holds four of the original squares, 16 square feet, which is four times the area, not twice.
2. Something between 2 and 4, then? The boy tries 3 feet. That gives 3 × 3 = 9 square feet, still too big.
3. “I do not know.” The boy gives up. Socrates tells Meno that this is progress. Before, the boy thought he knew and didn’t. Now he knows he doesn’t know, which makes him ready to look [9]. That’s the elenchus from the last primer, working the way Socrates hoped it would.
4. The diagonal. Socrates draws four of the original squares together, the same 16-square-foot square as the first guess, and draws a line from corner to corner across each one. Those four lines make a tilted square in the middle. Each line cuts a small square exactly in half, and the tilted square is made of four of those halves. Four halves of 4 is 8. So the answer is to build the new square on the diagonal of the old one [9].

The original square is the outlined one in the top-left corner, 2 feet on a side and 4 square feet. Each diagonal cuts a small square in half, and the tilted square is made of four of those halves, so it holds 8.

The boy never names a number for the side, and Socrates doesn’t ask for one. They show the answer with a drawing. The number is easy to work out with algebra, though. Call the old side l and the new side L. The old area is l², and the new area has to be double that:

L² = 2 × l²
L  = √2 × l  ≈ 1.414 × l

So the new side is √2 times the old one, about 41% longer. For the 2-foot square that’s 2√2, about 2.83 feet, which is why 3 was close but too big. The √2 multiplies the side, not the area.

The diagonal comes out to the same length. A diagonal cuts a square into two right triangles whose two short sides are both l, so by the Pythagorean theorem the diagonal is √(l² + l²) = √(2l²) = √2 × l. The drawing and the algebra land in the same place, which is the kind of answer Plato thought you could reach by thinking alone.

The podcast calls this a breakthrough in epistemology, the study of what we know and how we know it, and credits Plato with laying the groundwork for the 17th-century rationalists, who also trusted reason over the senses [2].

Did Plato mean a separate world literally?

The podcast mentions that a lot of smart people doubt Plato really believed in a separate world full of perfect things floating around. On that reading he was saying something more modest, that justice is something different from any particular just act [2].

The scholarship doesn’t settle it. Aristotle, who studied with Plato, reported that Plato “separated” the Forms. Scholars still argue about what that means. It might mean only that you can’t define Beauty by pointing at beautiful things, or it might mean the Forms really exist apart from everything else [7]. Plato kept testing the theory himself. Another dialogue, the Parmenides, raises hard objections to the Forms and doesn’t answer them, and the Republic calls the Form of the Good a mystery that nobody yet fully understands [3].

Courage isn’t the same thing as any one brave act, and you can be wrong about what’s really beautiful or just, which means there’s something there to be wrong about. Plato’s answer to the Sophists’ “man is the measure” was that the measure is outside us [2].

Plato’s ideal city

The Republic is a book about justice, and the city it designs is there to answer one question: is it actually better to be just, or only better to look just [10]?

The ring of Gyges

Early on, Plato’s brother Glaucon makes the case for the other side with a story. A shepherd named Gyges finds a gold ring that makes him invisible when he turns it on his finger. He uses it to get into the king’s court, seduce the queen, kill the king, and take the kingdom [8]. Glaucon’s point is that anyone with that ring, a just person included, would do the same, because people only behave justly out of fear of getting caught [8]. He and his brother challenge Socrates to show that justice is worth having for its own sake, even for someone who is just and is punished for it while an unjust person is rewarded [10].

Socrates’ answer takes the rest of the book. Justice is easier to see in something big, he says, so he imagines a whole city, finds justice there, and then looks for the same thing inside a single person [10].

Justice in the city and in the soul

The ideal city has three classes of people, and Plato says a person’s soul has three matching parts [10], [2].

Guardians is Plato’s word for the people who look after the city, and he uses it two ways. Broadly, it means the two upper classes together, the rulers and the soldiers: the people the city chooses, raises, and trains for the job. Strictly, Plato saves “guardian” for the rulers alone and renames the young soldiers auxiliaries, “supporters of the principles of the rulers” [8]. The podcast uses the broad sense and has the rulers picked from the best of the guardians [2], and so does this primer from here on. Either way, guardians are a minority. The farmers, craftspeople, and traders, most of the city, are not guardians.

The three classes side by side:

Justice, in the city and in a person, is each part doing its own job: reason in charge, spirit backing it up, and appetite kept in its place [10]. A just person isn’t just someone who follows rules. Their soul is in order, and Socrates spends the last books arguing that this order makes the just person happier than the unjust one, whatever happens to them [10].

The last column is the noble lie, a story the founders would tell every citizen. Everyone is born from the same earth, so they’re all siblings, but the god mixed gold into the rulers, silver into the auxiliaries, and bronze and iron into everyone else. Children usually take after their parents, but not always, and a golden child born to bronze parents has to be raised up, just as a bronze child of gold parents has to move down [8]. Plato calls it a lie himself. Its job is to make people accept where they stand and feel loyal to the city as a whole [10].

Raising good citizens: stories and heroes

Plato thought character is shaped young and mostly by what children are exposed to, so the city controls it. The guardians’ children would have their diet, their exercise, and even the songs and poems they heard strictly regulated, and every story would have its hero act the way the city would want its leaders to act [2].

In the Republic this starts with the stories mothers and nurses tell. Socrates says the first thing the city needs is “a censorship of the writers of fiction”: keep the good tales, throw out the bad ones, and let children hear only the approved ones, since stories shape a child’s mind the way hands shape their body [8]. That rules out much of Homer, because his gods lie, fight, and behave badly, and his heroes despair and lose control. The young should only imitate characters who are “courageous, temperate, holy, free,” because imitation that starts young and goes on for years turns into “a second nature” [8]. The goal is a person who learns to love what’s good before they’re old enough to understand why, and then recognizes it when reason arrives [10].

Music and physical training round out the education. Too much of either makes a person soft or harsh, and the point of both together is a soul in harmony, courageous and self-controlled, rather than a performer or an athlete [8]. The podcast describes the aim as getting young people out of their egos, building a moral compass, and teaching them to think rationally [2].

Philosopher kings

The rulers are philosophers, people who have made the climb out of the cave and know what justice and goodness really are. Socrates admits it sounds absurd, and says it anyway [8]:

Until philosophers are kings, or the kings and princes of this world have the spirit and power of philosophy, … cities will never have rest from their evils.

The podcast’s version of the reason: who better to rule than someone who knows exactly what justice and fairness are, instead of flawed people imposing their own biased and often corrupt views [2]? The encyclopedia adds a second reason. Philosophers make good rulers because they know what’s good and don’t want to rule. They’d rather keep thinking, so they have to be made to take their turn, which is the trip back down into the cave from earlier [10]. Someone who wants power is exactly who shouldn’t have it.

Plato makes the case with a picture of a ship. The owner is big and strong but half deaf and short-sighted and doesn’t know much about sailing. The crew fight over who gets to steer, none of them have learned navigation, and they claim it can’t be taught. They drug the owner, take over the ship, and treat the real navigator, the one who studies the stars and winds, as a useless stargazer [8]. The ship is the city, the crew are the people competing for power, and the navigator is the philosopher.

The guardians would also live together with no private property, no gold or silver, and no private families, with children raised in common [2]. And women could be guardians and rulers on the same terms as men. Socrates says being a man or a woman matters for these jobs about as much as having long hair or short hair [10]. The podcast calls this unprecedented for its time [2]. The encyclopedia is more careful: Socrates’ reasons are about what’s good for the city, not for women, and the Republic also makes disparaging remarks about women [10].

From best to worst: five governments

In Books VIII and IX, Plato ranks five kinds of government, and pairs each one with a kind of person whose soul is run the same way [8], [10]. Each one decays into the next.

Each government grows out of the one to its left as the thing its rulers care about slides further from wisdom.

1. Aristocracy, rule by the best, meaning the philosopher kings. Wisdom is in charge, the way reason is in charge of a just soul [2], [10].
2. Timocracy, rule by people who love honor. It starts when the rulers come to value honor and victory over knowledge. Plato’s examples are Sparta and Crete [8]. The podcast calls it a military dictatorship [2], which is close, though Plato’s point is less about the army than about honor replacing wisdom as the thing the rulers want. Over time the honor-lovers also start wanting money [10].
3. Oligarchy, rule by the rich. Wealth becomes the measure of a person, a property requirement decides who can hold office, and the city splits into the rich and a growing class of poor [8], [10], [2].
4. Democracy, rule by the many. The poor overthrow the rich, and freedom becomes the highest good [2]. Plato’s description is half compliment and half warning: “a charming form of government, full of variety and disorder, and dispensing a sort of equality to equals and unequals alike” [8]. The democratic person treats every desire as equally worth satisfying, so no part of the soul is really in charge [10]. The podcast says Plato hated democracy, and pictures it ending in undisciplined pandemonium [2]. It was also a democracy that had put Socrates to death [1].
5. Tyranny, rule by one man’s lawless appetite. Too much freedom, Plato says, turns into its opposite: “the excess of liberty … seems only to pass into excess of slavery” [8]. The people’s favorite champion, set up as their protector, takes power and turns into a tyrant [8]. The podcast puts it as all the self-indulgence of democracy with no laws left at all [2]. Plato thought the tyrant was the unhappiest person there is, a slave to his own desires and never satisfied [10].

So democracy isn’t last on Plato’s list, but it’s next to last, and he saw it as the step right before the worst.

A good city, or a frightening one?

Read today, a lot of this sounds alarming: rulers who decide which stories children can hear, a lie told to keep everyone in their place, and no vote. In the twentieth century the philosopher Karl Popper charged the Republic with being a blueprint for totalitarianism [10].

The encyclopedia lays out both sides. The rulers do control the culture and spread a useful myth, and they aim at the unity of the city as a whole. But they rule for the benefit of the ruled rather than their own, they don’t want power in the first place, and the city is supposed to hold together because citizens agree about who should rule, not because they’re forced [10]. The objections that remain are the ones most modern readers would raise anyway: that nobody can be trusted with that much power however much they know, and that people have a right to govern themselves even when they’d govern badly [10].

References

Every source cited across the primers is collected on one page.