Plato’s The Republic is a book about Socrates (Plato’s teacher) and several interlocutors attempting to find the nature of justice, and to prove that justice is superior to injustice. While Plato is the author, Socrates is the main character who presents Plato’s arguments. It seems likely that Socrates usually speaks with Plato’s voice throughout the text. To prove this point about justice, Socrates proposes to first examine justice in the state, since it will be larger and more readily apparent in a larger community, and then use this as a metaphor for the individual. As a result, The Republic is a work that combines both political and moral philosophy. I would call it mostly a political philosophy text. Of its eleven chapters, seven of them are devoted purely to the details of Plato’s ideal state. Of the remaining four, two of those chapters contain significant political elements, as they discuss morality explicitly through the metaphor of the state. Thus, we can call The Republic a political philosophy book with an undertone of moral philosophy included.
Thus, in order to examine the book and it’s conclusions, we have to ask the following:
- What is the nature of justice, according to Plato?
- What was Plato’s ideal political state like?
- What was Plato’s ideal morality, and how did it relate to the state?
After this, I’ll give my own thoughts on the matter.
It is worth noting that in this review, I’ll often be using gendered terms such as “craftsman” when looking at Plato’s arguments. This is because these are the words he generally uses, and thus using these terms stays closer to his own statements. When making my own thoughts or refutations, I’ll aim to switch back to gender-neutral terms.
At the start of the book, Socrates enters a dialogue about the nature of justice, and demonstrates what justice is not. First to step up is Polemarchus, who claims justice is a technē that enables us to help our friends and hurt our enemies. Technē is a Greek word that can mean various types of professional and creative skills. One could think of it as a skill, art, or craft. Socrates argues against this with several arguments. But the most important argument, the one we will come back to, is this.
Justice is what lets us help our friends, but harm our enemies. However, if we harm someone, we make them worse, by the standards of human excellence (arētē). But justice is human excellence. Thus, by making them worse, we make them more unjust. So a just man would not use his goodness (arētē) to make other people more unjust.
You may notice that the term arētē has been used twice here for different things - human excellence and goodness. This, too, is incredibly important. Socrates says “justice is human excellence”, meaning “justice is arētē”. Arētē means both excellence and goodness in the original Greek, and thus it does not seem a coincidence that Socrates pairs these two together a lot. To Socrates, human excellence and moral virtue are one and the same.
The second theory of justice is given by Thrasymachus, a sophist (paid orator and educator) who claims justice is what is in the interest of the stronger party. Thrasymachus continues later on and says that an unjust man will have more strength, freedom, and power than a just man. While it is not stated outright, my understanding of the implication of this is that Thrasymachus claims the unjust man achieves greater excellence than the just man, and since justice is human excellence, that means justice must be whatever is in the stronger party’s interest.
Socrates argues against this by talking about cooperation - saying that unjust men will naturally work against each other and even themselves, which would surely reduce that seeming strength, freedom, and power. Socrates then goes on to state one of the central themes of The Republic. The “function” of a thing is what it does best, life is a function of the mind, and thus a just mind must have a good life, while an unjust mind a bad one.
Adeimantus and Glaucon, who serve as the interlocutors for the rest of the book, then present the final case for injustice. Socrates says that justice should be welcomed both for its own sake and for the consequences it brings. Glaucon says that if justice is to be worthwhile for its own sake, it must be better to be a just man that everyone thinks is evil, rather than an unjust man that everyone thinks is virtuous. Adeimantus follows this up by saying it is to man’s advantage not to be just for the purposes of cooperation, but to have a reputation for justice and pretend to co-operate with legitimately just individuals. They then ask Socrates to prove that justice is worthwhile for its own sake, even if no worldly consequences for injustice are ever revealed. The case for this is what sets the stage for the rest of the book, and allows Socrates to extend upon what he said above.
Socrates goes on to say that justice is hard to find, but since larger things are easier to see [citation needed] we can start by finding justice in the community, then see if that maps to the individual. He starts by presenting a founding principle of the community - the idea of specialization. Each individual should do one job, and do one job well - the farmer should farm, the weaver should weave, the builder should build, and they should utilize trade in order to ensure they’re all better off. This philosophy of “Each person does a single job and does it well” is repeated often throughout The Republic.
Once a society desires luxuries, Socrates says, it must become large enough and ambitious enough to require soldiers for warfare and defense. Soldiering is itself a profession, and requires a dedicated soldier class called Guardians. It is worth noting that in Athens at the time, almost all able-bodied male citizens would participate in battle, whether as a soldier if they could afford equipment, or rowing the boats if not. Plato’s application of the specialization principle here thus goes against the orthodoxy of the time.
Socrates then brings up another of his central ideas - the Guardians must have a philosophic distribution. He does so via the following argument: Guardians should be like watchdogs, being aggressive towards enemies while protective towards friends. But the only difference between a friend and an enemy to a watchdog is that the dog is friendly towards those it knows. Therefore, if the dog alters its behavior based on knowledge, the dog must have a love of knowledge, which is the same as a philosophic disposition. Guard dogs are natural philosophers, and so too should our Guardians be. Yeah, this isn’t the last time we’ll run into a somewhat questionable metaphor from Plato. Apparently, the idea that the dog might be trained to do this and thus values obedience above all else didn’t occur to him. And while “obedience at all costs” may be considered by some a decent trait for a soldier, it makes for a pretty lousy philosopher.
Thus, I find this particular argument quite unconvincing.
Socrates then goes on to how these Guardians should be educated. He talks for a long time about art and poetry and what is and isn’t acceptable. To sum up - any representation of heroes and gods showing weakness, duplicity, negative emotions, and moral vice is unacceptable to Plato’s Republic. The Guardians may then think “Well, if it’s okay for Achilles and Zeus to act in such a way, why not me?” and we can’t have that in our soldier class. Socrates believes it fully justified to censor art, poetry, and even the genres of music allowed in the Republic in order to create this optimal environment for the Guardians.
One of the more jarring sections for modern readers appears next, when he talks about the physical education (read: military education) of the Guardians. In a section on health, he says that simplicity of exercise produces simplicity of health, and looks down greatly on the chronically ill. He says that anyone who cannot survive the routine of his ordinary job is of no use to himself or society, and thus the unhealthy should be left to die, and those whose psychological constitution is “incurably corrupt” will be put to death. Glaucon agrees this is for the best for both the individual sufferer and for society.
This is a jarring and callous section, but it also showcases the consequences of Plato’s beliefs. We will go into this in more detail later, but let us remember that for Plato, human excellence and moral virtue were heavily intertwined, and the same word is used for both. Plato is also very much a collectivist - he is focused on the health of the state and society, and the individuals within it are of little to no moral concern. Plato existed a couple of thousand years before liberalism, and that shows here.
Finally, Plato extends on his class system further, dividing the Guardians into two classes - Rulers (who rule, obviously) and Auxiliaries, who act as the soldier class. He says those who pass rigorous tests of body and mind will become Rulers, and that both Rulers and Auxiliaries should live a communistic type of lifestyle. They own no property of their own and are forbidden from handling silver or gold. Everything they need (and nothing else) will be provided by the rest of society as a tax. Plato believes this will prevent tyranny in the Guardians. This system is fairly similar to that of Sparta, with the added change of this communistic lifestyle. As we’ll see later, Plato believed Spartan society was perhaps the best society currently existing, second only to this ideal state he’s constructing here. Considering Sparta beat Athens in the Peloponnesian War a couple of decades earlier, this is a pretty sensible view to take. He goes on to stress the importance of the education system he has set up remaining unchanged throughout the generations and then, having set up the society to his satisfaction, moves to examine justice once more.
So, after sixty pages of detailing his ideal society, we finally get to the ostensible point of all this - the nature of justice. Socrates opens by saying that a perfect state will have the four cardinal virtues - wisdom, courage, self-discipline, and justice. The state has these four in the following ways:
That just leaves justice. Justice, Socrates states, is the quality that allows the first three to come into being and preserves them. This quality is the previously-argued concept of “One man, one job”. In other words, justice is when each person performs their duty in the state and does not stray from it - abandoning this is the worst of evils.
Socrates then draws an allegory to the individual. The individual, he argues, is represented by three aspects that parallel the three classes of our state. We have the mind, or reason, represented by our Rulers. We have the spirit, represented by our Auxiliaries. And we have the appetite, represented by our workers. The spirit is a translation of the Greek word thumos, which is less “spirit” as in “spiritual” and more “spirit” as in “competitive spirit”. Thumos represents courage, anger, passion, and ambition.
So then, what is justice in the individual? Justice in the individual is when each of these three parts is in its proper place. The appetite must be subordinate to the thumos, and the thumos must be subordinate to reason. Injustice is a civil war between these, where appetite or ambition rules over the mind and takes over a person, overcoming their rationality, the most noble part of them.
Finally, Socrates provides examples of how a just man would behave. He says that a just man would be the last person to perform any number of immoral acts, including stealing money, breaking a promise, committing adultery, being irreligious, or betraying his country. This showcases how Socrates, and by extension Plato, think of morality. Plato does not think of morality in terms of a universal system of right and wrong like utilitarianism or deontology. Plato sees morality as a natural outgrowth of character - if you are a just person who embodies arētē (i.e, your ambition and your appetites are subordinate to your reason, where they belong) you will naturally act in a moral way. Should your ambition or appetites reign supreme, you surely cannot help but act badly. It is no coincidence that Aristotle, Plato’s student, would be the one to formalize the theory of virtue ethics that argues for exactly this.
At this point, Adeimantus interrupts Socrates and tells him that he has been dodging the question of women and families in the ideal state. First, Socrates deals with women. While women are weaker than men, he said, they aren’t qualitatively different to men in the sense of both being specialized for different things. Thus, if we want to optimally use the talents of both men and women, women should be allowed to participate in all occupations in society, including participating as soldiers and as philosopher-rulers. This would be considered pretty progressive fifty years ago. Even today, saying that women should be able to be frontline combatants is far from a universal belief.
Then we move on to childbearing, and things become much more fraught. Remember Plato’s belief about the Guardians earlier. They can be allowed to hold no property, lest this lead them to lord over their fellows. They cannot be allowed to be slave to the passions, and romance and sex are of course the greatest passions of all. However, we still need to raise new Guardians, and while some crossing of classes is permitted, most Guardians will be children of Guardians. So how do we handle that?
Socrates says “It would be a sin either for mating or for anything else in a truly happy society to take place without regulation.” This is a very illuminating passage. As we said before, Plato was a collectivist, and we see now that he is decidedly authoritarian as well. Plato’s justice on a societal level is when each class stays in its lane. The rulers command, and everyone else obeys. To provide a mitigating factor to Plato’s views, he appears here to be talking purely about the Guardians - the workers can do as they like. The Guardians, too, own no material possessions and live a communal lifestyle designed to ensure they cannot, even in principle, steal benefits for themselves by wielding this unchecked power.
Plato goes on to draw an analogy between the Guardians and livestock. For breeding horses or dogs, you want to ensure pedigree and breed the best males and females with each other. Thus, we should do the same with our Guardians. However, Guardians aren’t dogs - they won’t take a life of involuntary celibacy lying down, so the solution is to create a rigged lot-drawing system that just so happens to pair the best Guardians with each other most of the time. Any children born from the subpar Guardians to maintain the illusion of fairness should be quietly moved outside of the Guardians into the worker class.
Finally, we move to the family. Guardians don’t have traditional families. Instead, their families are generational. Anyone born of the same generation is brother and sister, and anyone of an older one is mother and father. This means that romantic entanglements would have to be between “siblings”. These could also inadvertently be blood siblings - since the Guardians don’t recognise such a concept, nobody, including the individuals, would ever know. This doesn’t seem to bother Plato.
Plato then talks about the education of the Rulers, the philosopher kings and queens who will rule the Republic. The ones who are chosen for this must be intelligent, hard-working, and courageous - able to endure trials of the mind and have the courage to maintain moral convictions despite the allure of pleasure and the fear of pain. He then goes on to talk about how true philosophers simply don’t arise in current society, since society doesn’t value them, listen to them, or produce them - instead, the youths who have keen minds and bodies (and are thus suitable for philosophy) become popular and well-liked and society corrupts them. Socrates (and thus, presumably his pupil Plato) is perhaps the sole exception because of his “divine sign”, a voice in his head that forbids him from doing things. Keen-eyed readers may recognise this as a “conscience”.
To determine the true end of the philosopher-ruler, we need to digress slightly into Plato’s theory of forms. According to Plato, the world can be divided into forms and representations. A representation is something that actually exists in the world, whereas a form is an abstract, unchanging ideal - what modern philosophy might call “true X” or “X in itself”. A circle, for instance, is an abstract ideal, whereas a real circle like those you find on car wheels is an imperfect representation of the ideal. After all, even the roundest circle has some minor imperfections in it that deviates from a perfect circle. This is where the term “Platonic ideal” comes from.
One ambiguity that is not dealt with is the inherent subjectivity of some “Forms”. For instance, Plato uses a table as an example, saying that real tables are representations of the ideal Table, the thing that is purely a table and nothing else, a table-in-itself. But in the real world, the ideal table depends on the function a given individual wants it for. A grand dining table might be ideal for a family that enjoys hosting dinner parties, but isn’t ideal for a couple who live in a small apartment. Thus, how can there be a single ideal table, when the ideal table depends on the circumstances of its use? This is not addressed in the text of the Republic, and is a fairly serious flaw in the argument of Forms, especially when one extends this same argument to things more important than tables, like beauty, justice, or moral virtue.
Plato claims that knowledge must be based on these ideal, unchanging, abstract forms, because the real-life representation of these forms are imperfect and ever-changing. Thus, they fall under opinion, not knowledge. We can further subdivide these. The highest form of knowledge is pure thought, which is reasoning and debate over the nature of forms. This is the sole province of philosophers. Slightly below this we have reason, which largely concerns itself with mathematical objects. After all, a geometric circle isn’t “real”, but it isn’t as useful as a Form like beauty or truth. For this reason, mathematics is an important part of the education of a philosopher, who must be taught to think abstractly. Below this, we have opinion, which is separated into belief (knowledge about real, imperfect things) and illusion, which is representation of those real things. A representation is something like a painting, story, or sculpture - an imperfect image of a real thing. Plato believed that forms were to real objects as real objects were to their representations. This explains some of his disdain towards the arts - art is a shadow of a shadow, a representation of something that is never truly real in the first place.
To explain why philosopher-rulers are necessary, Plato uses his now famous allegory of the cave. The part most people know goes like this - imagine a bunch of people chained to the spot so their heads can’t move. Behind them, fires are lit, and in front of them, the people see shadows on the wall. Since that’s all they can see, and since these shadows gesticulate when the real people speak, they would come to believe these illusions were the real world. This is how most people see the world, where the shadows are real things, and the actual real things, the things behind the chained people, are Forms. He then goes on to say that if someone were to somehow leave this place and go into the light, they would find it confusing and blinding at first. It would take a long time for them to see and process things. They would need to start by looking at shadows, reflections, then real objects, then lights, and finally they could look at the Sun itself, which shines light upon all other things and allows us to see them. But once they did, they would never again see the shadow-world the same way.
The Sun, here, is a metaphor for the Form of the Good, the ultimate form from which all lesser virtues like Honesty and Truth can be seen, just like the Sun’s light lets us see the real world. Philosophy is about improving one’s ability to metaphorically see the light so they can look upon brighter things, eventually seeing the sun itself. These philosophers, upon seeing the world’s true splendor, will be reluctant to go down into the cave again and speak to the trapped people there and tell them of the truth - but they must, for the sake of their duty. Such a person would care not who the leader of these trapped people were, or for any of the trappings of fame and status in the shadow world of the cave. This makes them the perfect ruler - in addition to the knowledge of the Good that is so important to society, the only people that would resist the allure of power are those who see a greater world of philosophy, and perform politics solely out of duty to their fellow man rather than greed or lust for power.
Finally, Plato aims to shine a light on injustice. Just like he has used his ideal society as a metaphor for just character, so too will he use the various types of imperfect societies as a metaphor and an explanation for unjust characters. (There are two more chapters after this, which go into detail on why art is terrible and what rewards await the just soul in the afterlife, but they are unimportant to the central argument)
Socrates says there are four imperfect societies, each of which is worse than the last. His own society is at the top, and he calls it a monarchy or aristocracy, depending on whether there are one or many philosopher-rulers - either is acceptable here. The imperfect societies in descending order are timarchy, oligarchy, democracy, and tyranny.
A timarchy is a system much like that of ancient Sparta. It is ruled by soldiers, but it does not feature Plato’s philosopher-rulers or forbid the Guardians from owning property. This causes it to become warlike and greedy as the rulers seek wealth for themselves.
A timarchy could be created from Plato’s Republic if the ruling classes (Auxiliaries and Rulers) are divided. This could happen, he claims, if Plato’s system of eugenics isn’t properly followed, which causes the Guardians to allow themselves to own property. Now that the Guardians can attain riches, their ambition takes over. If we recall, the ideal person according to Plato is one where the appetite is subordinate to the spirit, and the spirit subordinate to the mind. In the timarchic character, the spirit takes over the mind, causing greed. When someone acquires more wealth than they need to live a good life, this is their ambition exceeding their reason. Reason is used in service of ambition, not the other way around.
An oligarchy is the next system down. Plato describes an oligarchy as a society where wealth is all that counts, where political power is in the hands of the rich, and the poor have none. This is similar to the idea of late-stage capitalism we see in the modern left. In Plato’s oligarchy, a certain amount of wealth and property is necessary to hold office. He also claims an oligarchy will inevitably split society into the rich and the poor, and that the worst possibility is a man can sell all he has (equipment, tools, and so on) and then have no useful function left. The closest analogy to this would be those caught in poverty traps today.
Plato claims an oligarchy would form when enough wealth forms in private hands that power falls to them and outside of the military rulers. The oligarchic character is concerned with money for its own sake. He tends to be quite frugal, and keeps his appetites in check lest he squander too much of his fortune. The same order of character (ambition -> reason -> appetite) is at play, but it is squandered towards more frivolous ends.
The next step down is a democracy. It is worth noting here that Athenian democracy, of which Plato lived in, was very different to modern democracy. In Athenian democracy, many important positions were drawn by lot, and any citizen could act as a prosecutor, bringing a criminal case before the courts. This is how Socrates died, and probably affects Plato’s views a fair bit. Plato claims oligarchy turns to democracy when the next generation rises up from an oligarchy. They have wealth, but don’t value it as much as those who fought to get it, so they are more willing to squander it.
A democracy forms from an oligarchy, Plato claims, when a combination of extravagance and predatory behavior causes a vast increase in the numbers of the poor, until the poor revolt against their oppressors and overthrow the rich, either through violence or the threat of violence. Socrates admits a democracy is actually “the most attractive of all societies''. It has a great deal of freedom and happiness. The democratic individual is torn between the frugal austerity of the oligarch, and a desire to indulge the appetites unrestrained. This usually creates a balance where the democratic individual wastes a lot of money and energy pursuing these appetites, but doesn’t go completely off the deep end. That’s reserved for our worst item - tyranny.
Tyranny is roughly what you’d expect, but we’ll start with how Plato believes we get there. Plato believes a tyranny arises from a democracy when the democratic desire of liberty above all becomes excessive. Rulers behave like subjects, subjects behave like rulers, and the extreme is reached when slaves have the same liberty as their owners, and we have complete equality and liberty in relations between the sexes. This prediction has, shall we say, not aged well.
Finally, Socrates says, citizens become so sensitive that any restraint at all is deemed intolerable, and they disregard all written and unwritten laws in their determination to have no master. This is an interesting passage, given that both the left and right can probably point to examples of where they see the other side doing this - the right talks about how social justice involves the tearing down of all our precious Western customs and traditions to suit their personal wants, and the left says the anti-vax movement is all about refusing even mild, reasonable demands from authority even when it’s clearly for the greater good.
This, however, Plato insists leads to tyranny. A popular leader will rob the rich, keep as much as they can for themselves, and spread the rest among the common people. When the rich resist this, a struggle emerges, causing a popular leader to arise. But that popular leader is destined to fall to corruption. Eventually he uses his power to take an enemy to court and have them sentenced to death. Enjoying this power, he does it more and more and becomes a tyrant.
Plato then returns to his original argument way back in the first chapter on justice. The tyrant is, after all, the ultimate unjust man - a man of unlimited power who uses flagrant injustice to make it so. So what is the life of a tyrant like? Plato claims he is a man enslaved by his most base desires that can never be satisfied. And they must always fear overthrow, so they need to surround themselves with stupid and servile followers - smart, ambitious ones may overthrow him. This is how the tyrant lives - eternally unfulfilled, surrounded by spineless yes-men, without a true friend in all the world.
Thus, Socrates concludes, the wickedest man is also the unhappiest. The higher up we go in our ladder of societies, the more just they are, and the people who best embody that state are happier too. The happiest of all people are the philosopher-rulers who embody the Republic, the ideal state. After all, there are three types of pleasure - indulging the appetite (through food, drink, and sex), indulging the spirit (through competition, ambition, and striving), and indulging the mind (through seeking the highest of knowledge) Socrates says that the mind is the noblest of these, and while a philosopher can taste the pleasure of indulging one’s appetite as a young man, the tyrant will never know what it is like to have pleasure of the mind. Thus, the philosopher is the best equipped to judge which pleasure is best, given that he is the only one who can taste them all. And as philosophers choose to live lives of the mind…well, that’s proof that it’s the most pleasurable, isn’t it?
Thus, Socrates concludes his grand argument. The just man is the happiest. Justice involves the appetite being subordinate to the spirit, and the spirit subordinate to reason. Only with this can one truly taste and appreciate the pleasures of the mind, the noblest and greatest of pleasures that life can bring. The less just one is, the further away from this one gets - and so even if a tyrant lives their entire life unchallenged and never faces judgment, in this life and the hereafter, they aren’t truly happy. They may think themselves happy, getting everything they could want, but they cannot comprehend the higher levels of satisfaction and eudaimonia (life worth living) that awaits them. Thus, justice is worthwhile - not just because it’s the right thing to do, but for its own sake.
If I had to summarize The Republic’s argument in two sentences, it would be this: “Both societies and people work best when the mind reigns supreme over the spirit, and the spirit reigns supreme over the appetite. When each element of a society or person performs only its proper function and performs it well, that is the nature of both justice and human excellence.”
These twin ideas of “One person should do one job well” and “There should be a clear hierarchy of control where some roles are superior to others” leads to Plato’s conclusions. Plato’s class system follows from this hierarchy of control. It makes perfect sense that he would have to have an authoritarian regime. Justice is when everyone stays in their lane. The rulers rule, the soldiers fight who they’re told to, and the workers do what they’re told to.
Morally, Plato believes that morality is a natural outgrowth of character. The just man would not steal or lie, since it is their ambition or their greed that causes people to do such things. If these were properly subordinated to the mind, there would be no problem. This idea would be expanded upon by Aristotle, though my understanding of Aristotle is that he does see morality as a domain unto itself. From Plato he takes the idea of moral behavior arising naturally from virtue, but unlike Plato he sees virtue as its own domain of excellence rather than something that arises naturally from a well-ordered mind.
There are some positives to this approach of Plato. Firstly, a just society is a society consisting of healthy, competent, and wise individuals. This is a worthy goal for a society to aspire to. Plato wanted everyone in his society to flourish and excel. While he didn’t bring up the idea of universal education, the idea of educating an entire class of individuals via the state was a pretty radical idea back in his day, when education was largely done privately. He also believed that women could contribute to society in all ways, including being Guardians and even Rulers - he saw no reason why some women couldn’t have the necessary excellence of mind and body for such a feat.
Plato’s idea of morality as an outgrowth of character is a precursor to virtue ethics, created by his student Aristotle. Virtue ethics is a major theory of ethics to this day for a reason, and it’s an eminently practical one. It is my personal opinion that if you want to become a better person, practicing virtuous behavior is a far better way to become a better person than reading theory. Theory should be used merely to guide practice.
That said, there are many more negatives than positives, in my opinion. First of all, the nature of justice in Plato’s society is when people stay in their own lane. Things like “Questioning authority” and “Seeking to change jobs” are a threat to Plato’s social order, and considered morally wrong. If you’re a worker, the morally just thing to do is to do your job no matter what - anything else is immoral. Plato claims that lack of unity is the worst thing that a society could possibly have happen to it, and the easiest way to have a united state is if everyone puts their head down and does whatever the rulers tell it to, just like a virtuous person will control their appetite when it demands pizza and make a rational decision about it rather than take marching orders from their stomach. Of course, if your stomach was a thinking, feeling being with moral agency, that would be a very different story.
There is also a rather serious downside to Plato’s ideas of justice and morality. We can make the argument with a few propositions. Morality is achieved by having a good character. Justice is the chief virtue of character. Justice is when someone does their job and does it well. Therefore, we can conclude, if someone cannot do a job well, they are a bad person.
What about those who can’t achieve this excellence, and cannot contribute to society? Plato has an answer to this - they’re better off dead, for their sake and the sake of society at large. Plato’s answer to the disabled is that if they can make a living for themselves, great. If not, that’s proof that they can’t achieve the only thing in life that matters, and thus they’re better off dying in the street. This leads to the most glaring omission in all of The Republic. The cardinal virtues are courage, wisdom, self-discipline, and justice - the last of which is merely a well-ordered and disciplined mind. In four hundred pages, not once does Plato talk of kindness, compassion, or mercy.
The closest he comes is in Chapter 1, when he claims that it would be unjust to harm any individual, lest you make them weaker and reduce their excellence. However, he never speaks of actively helping other people to raise their excellence, let alone supporting the people who can’t achieve it at all. When Plato speaks of moral acts, he speaks of avoiding wrong acts, not of performing kind ones. He says a just man will avoid stealing from their neighbor, but not that he will share his own bread. The idea of lifting others up and helping the vulnerable has no place in Plato’s moral calculus - and why should it? If morality is an outgrowth of character, good people will be able to contribute to society on their own. If they can’t, that’s proof they deserve what happens to them. Hey, technically you’re not harming them - you’re just letting them die on their own. Perfectly morally justified, right?
Finally, there is that of the philosopher-ruler and the Forms. We have already spoken of one issue with the Forms - what does it mean for something to be an “ideal table” if an ideal table depends on the needs of the individual or group who wants one? This is a minor quibble when we’re talking about tables, but a pretty serious question when talking about justice, beauty, and so on. Given everyone has their own ideas of what these things are, how do we determine the Forms? Plato says this is achieved through the most advanced stage of philosophical education, dialectic. Dialectic is a form of rational discussion and debate that is superior even to mathematical reasoning, because mathematics starts from a set of axioms, and dialectic tears those assumptions down to the first principle of everything, whatever that may be, then builds the Forms up from there.
This is the idea of “tabula rasa”, a blank slate, and it’s pretty thoroughly refuted by modern science. Psychology and neurobiology can both agree - we’re not a blank slate, and we can’t be. We all see the world through our own filters which are put into us by birth, upbringing, and society, and while we have the ability to tweak our own filters, we can never completely remove them. The kind of person who could discover truly perfect, timeless, universal beauty, virtue, justice, or the Form of the Good (if there even was such a thing) doesn’t exist, and never will.
I give Plato a pretty harsh critique in this essay, but let’s end on an uplifting note. Socrates is the father of Western philosophy, and Plato his mouthpiece. Plato brought philosophy into a golden age, and we can see a great deal of influence in philosophy from him. I haven’t read anywhere near enough philosophy to truly understand the depth of his influence on the West, but two sources stick out - Aristotelian virtue ethics, which we have already spoken of, and the Stoics’ view on the nature of humanity.
The Stoics believe that the purpose of a thing is to do what only that thing can do, or what that thing does best - a horse’s purpose is to be ridden, and a screwdriver’s purpose is to turn screws. When you put it that way, you could replace “purpose” with “excellence” and lose nothing. An excellent horse is an excellent mount. An excellent screwdriver is an excellent screw-turner. A human’s purpose is to be a rational, social being. Thus, the purpose of our existence according to the Stoics was to use our reasoning, and to use it for the benefit of humanity. This probably seems familiar to you, and that’s because this idea permeates the West even to this very day.
Plato is some of the earliest work in a truly deep and influential field. Plato was a giant on whom countless others have now stood on. It’s rough, it contains plenty of problems, but it contains the seed of truly great things. For this reason, even though I didn’t personally get a lot out of The Republic in terms of improving my life, or changing how I felt society should organize itself, I don’t regret the time I spent with it for a moment. Overall, I recommend it if you’re interested in learning about the field of philosophy as a whole. If you’re looking for works with more immediate instrumental value, works that provide immediate guidance on how to be a better person or to improve your life, I’d start with the Stoics.