Ancient and Medieval Philosophy: The Origin of Western Thought – Plato

Plato statue / Photo by lentina_x, Creative Commons

By Dr. Garth Kemerling / 11.12.2011
Professor of Philosophy
Capella University

Philosophy Pages

Plato: Immortality and the Forms

William Blake, The Spirit of Plato unfolds his Worlds to Milton in Contemplation / Pushkin State Museum of Fine Art

A Faithful Student

The most illustrious student Socrates had in philosophy was Plato, whose beautifully written dialogues not only offered an admiring account of the teachings of his master but also provided him with an opportunity to develop and express his own insightful philosophical views. In the remainder of our readings from Platonic dialogues, we will assume that the “Socrates” who speaks is merely a fictional character created by the author, attributing the philosophical doctrines to Plato himself. In the middle and late dialogues, Plato employed the conversational structure as a way of presenting dialectic, a pattern of argumentation that examines each issue from several sides, exploring the interplay of alternative ideas while subjecting all of them to evaluation by reason.

Plato was a more nearly systematic thinker than Socrates had been. He established his own school of philosophy, the Academy, during the fourth century, and he did not hesitate to offer a generation of young Athenians the positive results of his brilliant reasoning. Although he shared Socrates’s interest in ethical and social philosophy, Plato was much more concerned to establish his views on matters of metaphysics and epistemology, trying to discover the ultimate constituents of reality and the grounds for our knowledge of them.


Plato’s Μενων (Meno) is a transitional dialogue: although it is Socratic in tone, it introduces some of the epistemological and metaphysical themes that we will see developed more fully in the middle dialogues, which are clearly Plato’s own. In a setting uncluttered by concern for Socrates’s fate, it centers on the general problem of the origins of our moral knowledge.

The Greek notion of αρετη [aretê], or virtue, is that of an ability or skill in some particular respect. The virtue of a baker is what enables the baker to produce good bread; the virtue of the gardener is what enables the gardener to grow nice flowers; etc. In this sense, virtues clearly differ from person to person and from goal to goal. But Socrates is interested in true virtue, which (like genuine health) should be the same for everyone. This broad concept of virtue may include such specific virtues as courage, wisdom, or moderation, but it should nevertheless be possible to offer a perfectly general description of virtue as a whole, the skill or ability to be fully human. But what is that?

When Meno suggests that virtue is simply the desire for good things, Socrates argues that this cannot be the case. Since different human beings are unequal in virtue, virtue must be something that varies among them, he argues, but desire for one believes to be good is perfectly universal Since no human being ever knowingly desires what is bad, differences in their conduct must be a consequence of differences in what they know. (Meno 77e) This is a remarkable claim. Socrates holds that knowing what is right automatically results in the desire to do it, even though this feature of our moral experience could be doubted. (Aristotle, for example, would later explicitly disagree with this view, carefully outlining the conditions under which weakness of willinterferes with moral conduct.) In this context, however, the Socratic position effectively shifts the focus of the dialogue from morality to epistemology: the question really at stake is how we know what virtue is.

The Basis for Virtue

For questions of this sort, Socrates raises a serious dilemma: how can we ever learn what we do not know? Either we already know what we are looking for, in which case we don’t need to look, or we don’t know what we’re looking for, in which case we wouldn’t recognize it if we found it. (Meno 80e) The paradox of knowledge is that, in the most fundamental questions about our own nature and function, it seems impossible for us to learn anything. The only escape, Socrates proposed, is to acknowledge that we already know what we need to know. This is the doctrine of recollection, Plato’s conviction that our most basic knowledge comes when we bring back to mind our acquaintance with eternal realities during a previous existence of the soul.

The example offered in this dialogue is discovery of an irrational number, the square root of 2. Socrates leads an uneducated boy through the sophisticated geometrical demonstration with careful questions, showing that the boy somehow already knows the correct answers on his own. All of us have had the experience (usually in mathematical contexts, Plato believed) of suddenly realizing the truth of something of which we had been unaware, and it does often feel as if we are not really discovering something entirely new but rather merely remembering something we already knew. Such experiences lend some plausibility to Plato’s claim that recollection may be the source of our true opinions about the most fundamental features of reality. (Meno 85d) What is more, this doctrine provides an explanation of the effectiveness of Socratic method: the goal is not to convey new information but rather to elicit awareness of something that an individual already knows implicitly.

The further question of the dialogue is whether or not virtue can be taught. On the one hand, it seems that virtue must be a kind of wisdom, which we usually assume to be one of the acquirable benefits of education. On the other hand, if virtue could be taught, we should be able to identify both those who teach it and those who learn from them, which we cannot easily do in fact. (Meno 96c) (Here Socrates offers a scathing attack on the sophists, who had often claimed that they were effective teachers of virtue.) So it seems that virtue cannot be taught. Plato later came to disagree with his teacher on this point, arguing that genuine knowledge of virtue is attainable through application of appropriate educational methods.

Perhaps our best alternative, Socrates held, is to suppose that virtue is a (divinely bestowed?) true opinion that merely happens to lack the sort of rational justification which would earn it the status of certain knowledge. Whether or not we agree with this rather gloomy conclusion about the unteachability of virtue, the distinction between genuine knowledge and mere true opinion is of the greatest importance. For philosophical knowledge, it is not enough to accept beliefs that happen to be true; we must also have reasons that adequately support them.


The Φαιδων (Phaedo) concludes Plato’s description of the life of Socrates. Its final pages provide what appears to be an accurate account of the death of one of the most colorful personalities in the history of philosophy. (Phaedo115b) But most of the dialogue is filled with Plato’s own effort to establish with perfect certainty what Socrates had only been willing to speculate about in the Apology, that the human soul is truly immortal.

As Plato saw it, hope of survival comes naturally to the philosopher, whose whole life is one of preparation for death. What happens when we die, after all, is that the human soul separates from the human body, and it is concern for the soul rather than the body that characterizes a philosophical life. In fact, Plato argued that since knowledge of the most important matters in life is clearest to the soul alone, its customary attachment to a mortal body often serves only as a distraction from what counts. Here I am, thinking seriously about eternal truth, and then . . . I get hungry or sleepy, and the needs of the body interfere with my study. So, Plato concluded, the philosopher may properly look forward to death as a release from bodily limitations. (Phaedo 67d)

But is there really any reason to believe that the soul can continue to exist and function after the body dies? Plato supposed that there is, and his arguments on this point occupy the bulk of the Phaedo.

The Cycle of Opposites

The first argument is based on the cyclical interchange by means of which every quality comes into being from its own opposite. Hot comes from cold and cold from hot: that is, hot things are just cold things that have warmed up, and cold things are just hot things that have cooled off. Similarly, people who are awake are just people who were asleep but then woke up, while people who are asleep are just people who were awake but then dozed off.

But then, Plato argues by analogy, death must come from life and life from death. (Phaedo 71c-d) That is, people who are dead are just people who were alive but then experienced the transition we call dying, and people who are alive are just people who were among the dead but then experienced the transition we call being born. This suggests a perpetual recycling of human souls from the realm of the living to the realm of the dead and back.

If this is an accurate image of reality, it would certainly follow that my soul will continue to exist after the death of my body. But it also supposes that my soul existed before the birth of my body as well. This may seem like an extravagant speculation, but Plato held that there is ample evidence of its truth in the course of ordinary human life and learning.

The Forms

As Socrates had proposed in the Meno, the most important varieties of human knowledge are really cases of recollection. Consider, for example, our knowledge of equality. We have no difficulty in deciding whether or not two people are perfectly equal in height. In fact, they are never exactly the same height, since we recognize that it would always be possible to discover some difference—however minute—with a more careful, precise measurement. By this standard, all of the examples we perceive in ordinary life only approach, but never fully attain, perfect equality. But notice that since we realize the truth of this important qualification on our experience, we must somehow know for sure what true equality is, even though we have never seen it. (Phaedo 75b)

Plato believed that the same point could be made with regard to many other abstract concepts: even though we perceive only their imperfect instances, we have genuine knowledge of truth, goodness, and beauty no less than of equality. Things of this sort are the Platonic Forms, abstract entities that exist independently of the sensible world. Ordinary objects are imperfect and changeable, but they faintly copy the perfect and immutable Forms. Thus, all of the information we acquire about sensible objects (like knowing what the high and low temperatures were yesterday) is temporary, insignificant, and unreliable, while genuine knowledge of the Forms themselves (like knowing that 93 – 67 = 26) perfectly certain forever.

Since we really do have knowledge of these supra-sensible realities, knowledge that we cannot possibly have obtained through any bodily experience, Plato argued, it follows that this knowledge must be a form of recollection and that our souls must have been acquainted with the Forms prior to our births. But in that case, the existence of our mortal bodies cannot be essential to the existence of our souls—before birth or after death—and we are therefore immortal.

Immortality of the Soul

Use of the dialogue as a literary device made it easy for Plato not only to present his own position (in the voice of Socrates) but also to consider (in the voices of other characters) significant objections that might be raised against it. This doesn’t mean that philosophy is merely an idle game of argument and counter-argument, he pointed out, because it remains our goal to discover the one line of argument that leads to the truth. The philosopher cautiously investigates every possibility and examines every side of an issue, precisely because that increases the chances of arriving eventually at a correct account of reality.

Thus, Simmias suggests that the relationship between the soul and the body may be like that between musical harmony and the strings of a lyre that produces it. In this case, even though the soul is significantly different from the body, it could not reasonably be expected to survive the utter destruction of that physical thing. (This is an early statement of a view of human nature that would later come to be called epiphenomenalism.) But Socrates replies that this analogy will not hold, since the soul exercises direct control over the motions of the body, as the harmony does not over those of the lyre. Plato’s suggestion here seems to be that it would become impossible to provide an adequate account of human morality, of the proper standards for acting rightly, if Simmias were right.

Cebes offers a more difficult objection: what if the body is like a garment worn by the soul? Even though I continue to exist longer than any single article of my clothing does, there will come a time when I die, and some of my clothes will probably continue to exist. In the same way, even if the argument from opposites has shown that the soul can in principle outlast the life of any particular human body, there might come a time when the soul itself ceases to exist. Even if there is life after death, Cebes suggests, the soul may not be truly immortal.

In response to this criticism, Plato significantly revised the argument from opposities by incorporating an additional conception of the role of the Forms. Each Form, he now maintains, is the cause of all of every particular instance that bears its name: the form of Beauty causes the beauty of any beautiful thing; the form of Equality causes the equality of any pair of equal things; etc. But then, since the soul is living, it must participate in the Form of Life, and thus it cannot ever die. (Phaedo 105d) The soul is perfectly and certainly imperishable, not only for this life, but forever.

Despite the apparent force of these logical arguments, Plato chose to conclude the Phaedo by supplementing them with a mythical image of life after death. This concrete picture of the existence of a world beyond our own is imagined, not reasoned, so it cannot promise to deliver the same perfect representation of the truth. But if we are not fully convinced by the certainty of rational arguments, we may yet take some comfort from the suggestions of a pleasant story.

Plato: The State and the Soul

Wikimedia Commons

The Republic

The most comprehensive statement of Plato’s mature philosophical views appears in Πολιτεια (The Republic), an extended treatment of the most fundamental principles for the conduct of human life. Using the character “Socrates” as a fictional spokesman, Plato considers the nature and value of justice and the other virtues as they appear both in the structure of society as a whole and in the personality of an individual human being. This naturally leads to discussions of human nature, the achievement of knowledge, the distinction between appearance and reality, the components of an effective education, and the foundations of morality.

Because it covers so many issues, The Republic can be read in several different ways: as a treatise on political theory and practice, as a pedagogical handbook, or as a defence of ethical conduct, for example. Although we’ll take notice of each of these features along the way, our primary focus in what follows will be on the basic metaphysical and epistemological issues, foundational questions about who we are, what is real, and about how we know it. Read in this fashion, the dialogue as a whole invites us to share in Plato’s vision of our place within the ultimate structure of reality.

What is Justice?

Book I of The Republic appears to be a Socratic dialogue on the nature of justice (Gk. δικαιωσυνη [dikaiôsunê]). As always, the goal of the discussion is to discover the genuine nature of the subject at hand, but the process involves the proposal, criticism, and rejection of several inadequate attempts at defining what justice really is.

The elderly, wealthy Cephalus suggests that justice involves nothing more than telling the truth and repaying one’s debts. But Socrates points out that in certain (admittedly unusual) circumstances, following these simple rules without exception could produce disastrous results. (Republic 331c) Returning a borrowed weapon to an insane friend, for example, would be an instance of following the rule but would not seem to be an instance of just action. The presentation of a counter-example of this sort tends to show that the proposed definition of justice is incorrect, since its application does not correspond with our ordinary notion of justice.

In an effort to avoid such difficulties, Polemarchus offers a refinement of the definition by proposing that justice means “giving to each what is owed.” The new definition codifies formally our deeply-entrenched practice of seeking always to help our friends and harm our enemies. This evades the earlier counter-example, since the just act of refusing to return the borrowed weapon would clearly benefit one’s friend. But Socrates points out that harsh treatment of our enemies is only likely to render them even more unjust than they already are. (Republic 335d) Since, as we saw in the Phaedo, opposites invariably exclude each other, the production of injustice could never be an element within the character of true justice; so this definition, too, must be mistaken.

The Privilege of Power

At this point in the dialogue, Plato introduces Thrasymachus the sophist, another fictionalized portrait of an historical personality. After impatiently dismissing what has gone before, Thrasymachus recommends that we regard justice as the advantage of the stronger; those in positions of power simply use their might to decree what shall be right. This, too, expresses a fairly common (if somewhat pessimistic) view of the facts about social organization.

But of course Socrates has other ideas. For one thing, if the ruling party mistakenly legislates to its own disadvantage, justice will require the rest of us to perform the (apparently) contradictory feat of both doing what they decree and also doing what is best for them. More significantly, Socrates argues that the best ruler must always be someone who knows how to rule, someone who understands ruling as a craft. But since crafts of any sort invariably aim to produce some external goal (Gk. τελος [télos]), good practitioners of each craft always act for the sake of that goal, never in their own interest alone. Thus, good rulers, like good shepherds, must try to do what is best for those who have been entrusted to them, rather than seeking their own welfare. (Republic 342e)

Beaten down by the force of Socratic questioning, Thrasymachus lashes out bitterly and then shifts the focus of the debate completely. If Socrates does happen to be right about the nature of justice, he declares, then it follows that a life devoted to injustice is be more to one’s advantage than a life devoted to justice. Surely anyone would prefer to profit by committing an act of injustice against another than to suffer as the victim of an act of injustice committed by someone else. (“Do unto others before they do unto you.”) Thus, according to Thrasymachus, injustice is better than justice.

Some preliminary answers come immediately to mind: the personal rewards to be gained from performing a job well are commonly distinct from its intrinsic aims; just people are rightly regarded as superior to unjust people in intelligence and character; every society believes that justice (as conceived in that society) is morally obligatory; and justice is the proper virtue (Gk. αρετη [aretê]) of the human soul. But if Socrates himself might have been satisfied with responses of this sort, Plato the philosophical writer was not. There must be an answer that derives more fundamentally from the nature of reality.

Is Justice Better than Injustice?

When Thrasymachus falls silent, other characters from the dialogue continue to pursue the central questions: what is justice, how can we achieve it, and what is its value? Not everyone will agree that justice should be defended as worthwhile for its own sake, rather than for the extrinsic advantages that may result from its practice.

It helps to have a concrete example in mind. So Glaucon recounts the story of Gyges, the shepherd who discovered a ring that rendered him invisible and immediately embarked on a life of crime with perfect impunity. The point is to suggest that human beings—given an opportunity to do so without being caught and therefore without suffering any punishment or loss of good reputation—would naturally choose a life of injustice, in order to maximize their own interests.

Adeimantus narrows the discussion even further by pointing out that the personal benefits of having a good reputation are often acquired by anyone who merely appears to act justly, whether or not that person really does so. (Republic 363a) This suggests the possibility of achieving the greatest possible advantage by having it both ways: act unjustly while preserving the outward appearance of being just, instead of acting justly while risking the outward appearance of injustice. In order to demonstrate once and for all that justice really is valuable for its own sake alone, Plato must show that a life of the second sort is superior to a life of the first sort.

Thrasymachus, Glaucon, and Adeimantus have given voice to a fundamental issue at the heart of any effort to improve human conduct by appealing to the principles of moral philosophy. If what I am morally required to do can (in some circumstances) be different from what I would choose do for my own benefit, then why should I be moral? Plato wrote the remainder of The Republicin an attempt to provide an adequate, satisfying answer to this question.

After Book I, the entire dialogue is pervaded by an extended analogy between the justice of individual human beings and the that of an entire society or city-state. Since the crucial elements of justice may be easier to observe on the larger scale (Republic 369a), Plato began with a detailed analysis of the formation, structure, and organization of an ideal state before applying its results to a description of personal life.

Why We Form a Society

Imagining their likely origins in the prehistorical past, Plato argued that societies are invariably formed for a particular purpose. Individual human beings are not self-sufficient; no one working alone can acquire all of the genuine necessities of life. In order to resolve this difficulty, we gather together into communities for the mutual achievement of our common goals. This succeeds because we can work more efficiently if each of us specializes in the practice of a specific craft: I make all of the shoes; you grow all of the vegetables; she does all of the carpentry; etc. Thus, Plato held that separation of functions and specialization of labor are the keys to the establishment of a worthwhile society.

The result of this original impulse is a society composed of many individuals, organized into distinct classes (clothiers, farmers, builders, etc.) according to the value of their role in providing some component part of the common good. But the smooth operation of the whole society will require some additional services that become necessary only because of the creation of the social organization itself—the adjudication of disputes among members and the defense of the city against external attacks, for example. Therefore, carrying the principle of specialization one step further, Plato proposed the establishment of an additional class of citizens, the guardians who are responsible for management of the society itself.

In fact, Plato held that effective social life requires guardians of two distinct sorts: there must be both soldiers whose function is to defend the state against external enemies and to enforce its laws, and rulers who resolve disagreements among citizens and make decisions about public policy. The guardians collectively, then, are those individuals whose special craft is just the task of governance itself.

Training the Guardians

In order to fulfill their proper functions, these people will have to be special human beings indeed. Plato hinted early on that one of their most evident characteristics will be a temperamental inclination toward philosophical thinking. As we’ve already seen in the Apology and in the Phaedo, it is the philosopher above all others who excels at investigating serious questions about human life and at judging what is true and best. But how are personal qualities of this sort to be fostered and developed in an appropriate number of individual citizens? (Republic 376d)

The answer, Plato believed, was to rely upon the value of a good education. (Remember, he operated his own school at Athens!) We’ll have an opportunity to consider his notions about higher education later, but his plan for the elementary education of guardians for the ideal state appears in Book III. Its central concern is an emphasis on achieving the proper balance of many disparate components—physical training and musical performance along with basic intellectual development.

One notable feature of this method of raising children is Plato’s demand for strict censorship of literary materials, especially poetry and drama. He argued that early absorption in fictional accounts can dull an person’s ability to make accurate judgments regarding matters of fact and that excessive participation in dramatic recitations might encourage some people to emulate the worst behavior of the tragic heros. (Republic 395c) Worst of all, excessive attention to fictional contexts may lead to a kind of self-deception, in which individuals are ignorant of the truth about their own natures as human beings. (Republic 382b) Thus, on Plato’s view, it is vital for a society to exercise strict control over the content of everything that children read, see, or hear. As we will later notice, Aristotle had very different ideas.

Training of the sort described here (and later) is intended only for those children who will eventually become the guardians of the state. Their performance at this level of education properly determines both whether they are qualified to do so and, if so, whether each of them deserves to be a ruler or a soldier. A society should design its educational system as a means to distinguish among future citizens whose functions will differ and to provide training appropriate to the abilities of each.

Divisions of the State

The principle of specialization thus leads to a stratified society. Platobelieved that the ideal state comprises members of three distinct classes: rulers, soldiers, and the people. Although he officially maintained that membership in the guardian classes should be based solely upon the possession of appropriate skills, Plato presumed that future guardians will typically be the offspring of those who presently hold similar positions of honor. If citizens express any dissatisfaction with the roles to which they are assigned, he proposed that they be told the “useful falsehood” that human beings (like the metals gold, silver, and bronze) possess different natures that fit each of them to a particular function within the operation of the society as a whole. (Republic 415a)

Notice that this myth (Gk. μυθος [mythos]) cuts both ways. It can certainly be used as a method of social control, by encouraging ordinary people to accept their position at the bottom of the heap, subject to governance by the higher classes. But Plato also held that the myth justifies severe restrictions on the life of the guardians: since they are already gifted with superior natures, they have no need for wealth or other external rewards. In fact, Plato held that guardians should own no private property, should live and eat together at government expense, and should earn no salary greater than necessary to supply their most basic needs. Under this regime, no one will have any venal motive for seeking a position of leadership, and those who are chosen to be guardians will govern solely from a concern to seek the welfare of the state in what is best for all of its citizens.

Having developed a general description of the structure of an ideal society, Plato maintained that the proper functions performed by its disparate classes, working together for the common good, provide a ready account of the need to develop significant social qualities or virtues.

Since the rulers are responsible for making decisions according to which the entire city will be governed, they must have the virtue of wisdom (Gk. σοφια [sophía]), the capacity to comprehend reality and to make impartial judgments about it.
Soldiers charged with the defense of the city against external and internal enemies, on the other hand, need the virtue of courage (Gk. ανδρεια [andreia]), the willingness to carry out their orders in the face of danger without regard for personal risk.
The rest of the people in the city must follow its leaders instead of pursuing their private interests, so they must exhibit the virtue ofmoderation (Gk. σωφρσυνη [sophrosúnê]), the subordination of personal desires to a higher purpose.
When each of these classes performs its own role appropriately and does not try to take over the function of any other class, Plato held, the entire city as a whole will operate smoothly, exhibiting the harmony that is genuine justice. (Republic 433e)We can therefore understand all of the cardinal virtues by considering how each is embodied in the organization of an ideal city.

Wise Decisions

Courageous Actions

Farmers, Merchants, and other People
(Moderated Desires)

Justice itself is not the exclusive responsibility of any one class of citizens, but emerges from the harmonious interrelationship of each component of the society with every other. Next we’ll see how Plato applied this conception of the virtues to the lives of individual human beings.

The Virtues in Human Souls

Remember that the basic plan of the Republic is to draw a systematic analogy between the operation of society as a whole and the life of any individual human being. So Plato supposed that people exhibit the same features, perform the same functions, and embody the same virtues that city-states do. Applying the analogy in this way presumes that each of us, like the state, is a complex whole made up of several distinct parts, each of which has its own proper role. But Plato argued that there is ample evidence of this in our everyday experience. When faced with choices about what to do, we commonly feel the tug of contrary impulses drawing us in different directions at once, and the most natural explanation for this phenomenon is to distinguish between distinct elements of our selves. (Republic 436b)

Thus, the analogy holds. In addition to the physical body, which corresponds to the land, buildings, and other material resources of a city, Plato held that every human being includes three souls (Gk. ψυχη [psychê]) that correspond to the three classes of citizen within the state, each of them contributing in its own way to the successful operation of the whole person.

The rational soul (mind or intellect) is the thinking portion within each of us, which discerns what is real and not merely apparent, judges what is true and what is false, and wisely makes the rational decisions in accordance with which human life is most properly lived.

The spirited soul (will or volition), on the other hand, is the active portion; its function is to carry out the dictates of reason in practical life,courageously doing whatever the intellect has determined to be best.

Finally, the appetitive soul (emotion or desire) is the portion of each of us that wants and feels many things, most of which must be deferred in the face of rational pursuits if we are to achieve a salutary degree of self-control.
In the Phaedrus, Plato presented this theory even more graphically, comparing the rational soul to a charioteer whose vehicle is drawn by two horses, one powerful but unruly (desire) and the other disciplined and obedient (will).On Plato’s view, then, an human being is properly said to be just when the three souls perform their proper functions in harmony with each other, working in consonance for the good of the person as a whole.

Rational Soul (Thinking)

Spirited Soul (Willing)

Appetitive Soul (Feeling)

As in a well-organized state, the justice of an individual human being emerges only from the interrelationship among its separate components. (Republic 443d)Plato’s account of a tripartite division within the self has exerted an enormous influence on the philosophy of human nature in the Western tradition. Although few philosophers whole-heartedly adopt his hypostasizationof three distinct souls, nearly everyone acknowledges some differentiation among the functions of thinking, willing, and feeling. (Even in The Wizard of Oz, Dorothy’s quest depends upon the cooperation of her three friends—Scarecrow, Lion, and Tin Woodsman—each of whom exemplifies one of the three aspects of human nature.) Perhaps any adequate view of human life requires some explanation or account (Gk. λογος [logos]) of how we incorporate intellect, volition, and desire in the whole of our existence.

In the context of his larger argument, Plato’s theory of human nature provides the foundation for another answer to the question of why justice is better than injustice. On the view developed here, true justice is a kind of good health, attainable only through the harmonious cooperative effort of the three souls. In an unjust person, on the other hand, the disparate parts are in perpetual turmoil, merely coexisting with each other in an unhealthy, poorly-functioning, dis-integrated personality. Plato developed this theme in greater detail in the final books of The Republic.

Plato: Education and the Value of Justice

Plato’s Allegory of the cave, by Jan Saenredam, after Cornelis van Haarlem, engraving, 1604 / British Museum, London

Men and Women

As an account of political organization on the larger scale, Plato’s defense of an aristocratic government was unlikely to win broad approval in democratic Athens. He used the characters Glaucon and Adeimantus to voice practical objections against the plan. They are especially concerned (as Plato’s Athenian contemporaries may well have been) with some of its provisions for the guardian class, including the participation of both men and women, the elimination of families, and the education of children.

Most fifth-century Greeks, like many twentieth-century Americans, supposed that natural differences between males and females of the human species entail a significant differentiation of their proper social roles. Although Plato granted that men and women are different in height, strength, and similar qualities, he noted that these differences are not universal; that is, for example, although it may be true that most men are taller than most women, there are certainly some women who are taller than many men. What is more, he denied that there is any systematic difference between men and women with respect to the abilities relevant to guardianship—the capacity to understand reality and make reasonable judgments about it. (Republic 454d) Thus, Plato maintained that prospective guardians, both male and female, should receive the same education and be assigned to the same vital functions within the society.

In addition, Plato believed that the interests of the state are best preserved if children are raised and educated by the society as a whole, rather than by their biological parents. So he proposed a simple (if startlingly unfamiliar) scheme for the breeding, nurturing, and training of children in the guardian class. (Note that the same children who are not permitted to watch and listen to “dangerous” art are encouraged to witness first-hand the violence of war.) The presumed pleasures of family life, Plato held, are among the benefits that the higher classes of a society must be prepared to forego.

Philosopher / Kings

A general objection to the impracticability of the entire enterprise remains. Even if we are persuaded that Plato’s aristocracy is the ideal way to structure a city-state, is there any possibility that it will actually be implemented in a human society? Of course there is a sense in which it doesn’t matter; what ought to be is more significant for Plato than what is, and philosophers generally are concerned with a truth that transcends the facts of everyday life.

But Plato also believed that an ideal state, embodying the highest and best capabilities of human social life, can really be achieved, if the right people are put in charge. Since the key to the success of the whole is the wisdom of the rulers who make decisions for the entire city, Plato held that the perfect society will occur only when kings become philosophers or philosophers are made kings. (Republic 473d)

Only those with a philosophical temperament, Plato supposed, are competent to judge between what merely seems to be the case and what really is, between the misleading, transient appearances of sensible objects and the the permanent reality of unchanging, abstract forms. Thus, the theory of forms is central to Plato’s philosophy once again: the philosophers who think about such things are not idle dreamers, but the true realists in a society. It is precisely their detachment from the realm of sensory images that renders them capable of making accurate judgments about the most important issues of human life.

Thus, despite prevalent public skepticism about philosophers, it is to them that an ideal society must turn for the wisdom to conduct its affairs properly. But philosophers are made, not born. So we need to examine the program of education by means of which Plato supposed that the future philosopher-kings can acquire the knowledge necessary for their function as decision-makers for the society as a whole.

The Strucure of Human Knowledge

Since an ideal society will be ruled by those of its citizens who are most aware of what really matters, it is vital to consider how that society can best raise and educate its philosophers. Plato supposed that under the usual haphazard methods of childrearing, accidents of birth often restrict the opportunities for personal development, faulty upbringing prevents most people from achieving everything of which they are capable, and the promise of easy fame or wealth distracts some of the most able young people from the rigors of intellectual pursuits. But he believed that those with the greatest ability—that is, people with a natural disposition fit for philosophical study—must receive the best education, engaging in a regimen of mental discipline that grows more strict with every passing year of their lives.

The highest goal in all of education, Plato believed, is knowledge of the Good; that is, not merely an awareness of particular benefits and pleasures, but acquaintance with the Form itself. Just as the sun provides illumination by means of which we are able to perceive everything in the visual world, he argued, so the Form of the Good provides the ultimate standard by means of which we can apprehend the reality of everything that has value. (Republic508e) Objects are worthwhile to the extent that they participate in this crucial form.

So, too, our apprehension of reality occurs in different degrees, depending upon the nature of the objects with which it is concerned in each case. Thus, there is a fundamental difference between the mere opinion (Gk. δοξα [dóxa]) we can have regarding the visible realm of sensible objects and the genuineknowledge (Gk. επιστημη [epistêmê]) we can have of the invisible realm of the Forms themselves. In fact, Plato held that each of these has two distinct varieties, so that we can picture the entire array of human cognition as a line divided proportionately into four segments. (Republic 509d)

At the lowest level of reality are shadows, pictures, and other images, with respect to which imagination (Gk. εικασια [eikásia]) or conjecture is the appropriate degree of awareness, although it provides only the most primitive and unreliable opinions.

The visible realm also contains ordinary physical objects, and our perception of them provides the basis for belief (Gk. πιστις [pístis]), the most accurate possible conception of the nature and relationship of temporal things.

Moving upward into the intelligible realm, we first become acquainted with the relatively simple Forms of numbers, shapes, and other mathematical entities; we can achieve systematic knowledge of these objects through a disciplined application of the understanding (Gk. διανοια [diánoia]).

Finally, at the highest level of all, are the more significant Forms—true Equality, Beauty, Truth, and of course the Good itself. These permanent objects of knowledge are directly apprehended by intuition (Gk. νοησις [nóêsis]), the fundamental capacity of human reason to comprehend the true nature of reality.

The Allegory of the Cave

Plato recognized that the picture of the Divided Line may be difficult for many of us to understand. Although it accurately represents the different levels of reality and corresponding degrees of knowledge, there is a sense in which one cannot appreciate its full significance without first having achieved the highest level. So, for the benefit of those of us who are still learning but would like to grasp what he is talking about, Plato offered a simpler story in which each of the same structural components appears in a way that we can all comprehend at our own level. This is the Allegory of the Cave.

Suppose that there is a group of human beings who have lived their entire lives trapped in a subterranean chamber lit by a large fire behind them. Chained in place, these cave-dwellers can see nothing but shadows (of their own bodies and of other things) projected on a flat wall in front of them. Some of these people will be content to do no more than notice the play of light and shadow, while the more clever among them will become highly skilled observers of the patterns that most regularly occur. In both cases, however, they cannot truly comprehend what they see, since they are prevented from grasping its true source and nature. (Republic 514a)

Now suppose that one of these human beings manages to break the chains, climb through the torturous passage to the surface, and escape the cave. With eyes accustomed only to the dim light of the former habitation, this individual will at first be blinded by the brightness of the surface world, able to look only upon the shadows and reflections of the real world. But after some time and effort, the former cave-dweller will become able to appreciate the full variety of the newly-discovered world, looking at trees, mountains, and (eventually) the sun itself.

Finally, suppose that this escapee returns to the cave, trying to persuade its inhabitants that there is another, better, more real world than the one in which they have so long been content to dwell. They are unlikely to be impressed by the pleas of this extraordinary individual, Plato noted, especially since their former companion, having travelled to the bright surface world, is now inept and clumsy in the dim realm of the cave. Nevertheless, it would have been in the best interest of these residents of the cave to entrust their lives to the one enlightened member of their company, whose acquaintance with other things is a unique qualification for genuine knowledge.

Plato seriously intended this allegory as a representation of the state of ordinary human existence. We, like the people raised in a cave, are trapped in a world of impermanence and partiality, the realm of sensible objects. Entranced by the particular and immediate experiences these things provide, we are unlikely to appreciate the declarations of philosophers, the few among us who, like the escapee, have made the effort to achieve eternal knowledge of the permanent forms. But, like them, it would serve us best if we were to follow this guidance, discipline our own minds, and seek an accurate understanding of the highest objects of human contemplation.

An Educational Program

Having already described the elementary education and physical training that properly occupy the first twenty years of the life of prospective guardians,Plato applied his account of the structure of human knowledge in order to prescribe the disciplined pursuit of their higher education.

It naturally begins with mathematics, the vital first step in learning to turn away from the realm of sensible particulars to the transcendent forms of reality. Arithmetic provides for the preliminary development of abstract concepts, but Plato held that geometry is especially valuable for its careful attention to the eternal forms. Study of the (mathematical, not observational) disciplines of astronomy and harmonics encourage the further development of the skills of abstract thinking and proportional reasoning.

Only after completing this thorough mathematical foundation are the future rulers of the city prepared to begin their study of philosophy, systematizing their grasp of mathematical truth, learning to recognize and eliminate all of their presuppositions, and grounding all genuine knowledge firmly on the foundation of their intuitive grasp of the reality of the Forms. Finally, an extended period of apprenticeship will help them to learn how to apply everything they have learned to the decisions necessary for the welfare of the city as a whole. Only in their fifties will the best philosophers among them be fit to rule over their fellow-citizens.

Kinds of State or Person

In order to explain the distinction between justice and injustice more fully, Plato devoted much of the remainder of The Republic to a detailed discussion of five different kinds of government (and, by analogy, five different kinds of person), ranked in order from best to worst:

A society organized in the ideally efficient way Plato has already described is said to have an aristocratic government. Similarly, an aristocratic person is one whose rational, spirited, and appetitive souls work together properly. Such governments and people are the most genuine examples of true justice at the social and personal levels.

In a defective timocratic society, on the other hand, the courageous soldiers have usurped for themselves the privilege of making decisions that properly belongs only to its better-educated rulers. A timocratic person is therefore someone who is more concerned with belligerently defending personal honor than with wisely choosing what is truly best.

In an oligarchic government, both classes of guardian have been pressed into the service of a ruling group comprising a few powerful and wealthy citizens. By analogy, an oligarchic personality is someone whose every thought and action is devoted to the self-indulgent goal of amassing greater wealth.

Even more disastrously, a democratic government holds out the promise of equality for all of its citizens but delivers only the anarchy of an unruly mob, each of whose members is interested only in the pursuit of private interests. The parallel case of a democratic person is someone who is utterly controlled by desires, acknowledging no bounds of taste or virtue in the perpetual effort to achieve the momentary satisfaction that pleasure provides.

Finally, the tyrranic society is one in which a single individual has gained control over the mob, restoring order io place of anarchy, but serving only personal welfare instead of the interests of the whole city. A tyrranic person, then, must be one whose entire life is focussed upon the satisfaction of a single desire at the expense of everything else that truly matters. Governments and people of this last variety are most perfectly unjust, even though they may appear to be well-organized and effective.

Although Plato presents these five types of government or person as if there is a natural progression from each to the next, his chief concern is to exhibit the relative degree of justice achieved by each. The most perfect contrast between justice and injustice arises in a comparison between the aristocratic and the tyrranic instances.

Justice is Better than Injustice

Thus, we are finally prepared to understand the full force of Plato’s answer to the original challenge of showing that justice is superior to injustice. He offered three arguments, each of which is designed to demonstrate the intrinsicmerits of being a just person.

First, Plato noted that the just life of an aristocratic person arises from an effortless harmony among internal elements of the soul, while the unjust life of a tyrranic person can maintain its characteristic imbalance only by the exertion of an enormous effort. Thus, it is simply easier to be just than to be unjust. (Republic 580a) This argument makes sense even independently of Plato’s larger theory; it is a generalized version of the fairly common notion that it is easier to be honest than to keep track of the truth along with a number of false stories about it.

Second, Plato claimed that tyrranic individuals can appreciate only pleasures of the body, monetary profits, and the benefits of favorable public reputation, all of which are by their nature transitory. Aristocratic people, on the other hand, can accept these things in moderation but also transcend them in order to enjoy the delights of intellectual achievement through direct acquaintance with the immutable Forms. (Republic 583a) This argument relies more heavily upon adoption of Plato’s entire theory of human nature, as developed in The Republicand other dialogues; it is likely to influence only those who have already experienced the full range of intellectual advantages for themselves.

Finally, Plato resorted to myth (just as he had at the close of the Phaedo by imagining that justice will be rewarded with steady progression in a series of lives hereafter. This “Myth of Er” isn’t philosophical argument at all. Even if it were literally true and demonstrable that the just are rewarded in the afterlife, that would be only an extrinsic motive for being just, not a proof of its intrinsic value.

Although it is a masterly treatment of human nature and politics, The Republic was not Plato’s only discussion of these significant issues. His dialogue Gorgias includes an eloquent appeal on behalf of the life of justice and personal non-violence in all things. The Statesman devotes extended attention to the practical matter of securing effective government under the less-than-ideal conditions most of us commonly face. And the unfinishedΛεγεισ (Laws) is a lengthy analysis of the history of Athenian political life.