Born: 429 BC. Died: 347 BC.


- The goal of intellectual inquiry is to discover the eternal immutable forms of 'ideas', which serve as the essence and ideal of all things; in this way a true philosopher seeks wisdom.

- These eternal truths, already in the mind, can be recalled by the imaterial and immortal intellect; they cannot be grasped by the bodily senses.

- Education consists in the perfecting the whole person in order to achieve self-mastery and self-realization.

- Education has as its goal, as should all human acts, knowledge of the good, for ignorance of the good leads to evil.

- A perfect society is but the external reflection of a harmoniously integrated soul where appetite and desire are under the command of reason.

- Only the Philosopher who has achieved true knowledge is fit to rule; democracy, the rule of the majority, is usually rooted in mere opinions.


Plato, Greek philosopher, one of the most creative and influential thinkers in Western philosophy.

Plato was born to an aristocratic family in Athens. His father, Ariston, was believed to have descended from the early kings of Athens. Perictione, his mother, was distantly related to the 6th century BC lawmaker Solon. When Plato was a child, his father died, and his mother married Pyrilampes, who was an associate of the statesman Pericles.

As a young man Plato had political ambitions, but he became disillusioned by the political leadership in Athens. He eventually became a disciple of Socrates, accepting his basic philosophy and dialectical style of debate: the pursuit of truth through questions, answers, and additional questions.

Plato witnessed the death of Socrates at the hands of the Athenian democracy in 399 BC. Perhaps fearing for his own safety, he left Athens temporarily and traveled to Italy, Sicily, and Egypt.

In 387 Plato founded the Academy in Athens, the institution often described as the first European university. It provided a comprehensive curriculum, including such subjects as astronomy, biology, mathematics, political theory, and philosophy. Aristotle was the Academy's most prominent student.

Pursuing an opportunity to combine philosophy and practical politics, Plato went to Sicily in 367 to tutor the new ruler of Syracuse, Dionysius the Younger, in the art of philosophical rule. The experiment failed. Plato made another trip to Syracuse in 361, but again his engagement in Sicilian affairs met with little success. The concluding years of his life were spent lecturing at the Academy and writing.

He died at about the age of 80 in Athens.


Plato's writings were in dialogue form; philosophical ideas were advanced, discussed, and criticized in the context of a conversation or debate involving two or more persons. The earliest collection of Plato's work includes 35 dialogues and 13 letters. The authenticity of a few of the dialogues and most of the letters has been disputed.

Early Dialogues

The dialogues may be divided into early, middle, and later periods of composition. The earliest represent Plato's attempt to communicate the philosophy and dialectical style of Socrates. Several of these dialogues take the same form. Socrates, encountering someone who claims to know much, professes to be ignorant and seeks assistance from the one who knows. As Socrates begins to raise questions, however, it becomes clear that the one reputed to be wise really does not know what he claims to know, and Socrates emerges as the wiser one because he at least knows that he does not know. Such knowledge, of course, is the beginning of wisdom. Included in this group of dialogues are Charmides (an attempt to define temperance), Lysis (a discussion of friendship), Laches (a pursuit of the meaning of courage), Protagoras (a defense of the thesis that virtue is knowledge and can be taught), Euthyphro (a consideration of the nature of piety), and Book I of the Republic (a discussion of justice).

Middle and Late Dialogues

The dialogues of the middle and later periods of Plato's life reflect his own philosophical development. The ideas in these works are attributed by most scholars to Plato himself, although Socrates continues to be the main character in many of the dialogues. The writings of the middle period include Gorgias (a consideration of several ethical questions), Meno (a discussion of the nature of knowledge), the Apology (Socrates' defense of himself at his trial against the charges of atheism and corrupting Athenian youth), Crito (Socrates' defense of obedience to the laws of the state), Phaedo (the death scene of Socrates, in which he discusses the theory of Forms, the nature of the soul, and the question of immortality), the Symposium (Plato's outstanding dramatic achievement, which contains several speeches on beauty and love), the Republic (Plato's supreme philosophical achievement, which is a detailed discussion of the nature of justice). The works of the later period include the Theaetetus (a denial that knowledge is to be identified with sense perception), Parmenides (a critical evaluation of the theory of Forms), Sophist (further consideration of the theory of Ideas, or Forms), Philebus (a discussion of the relationship between pleasure and the good), Timaeus (Plato's views on natural science and cosmology), and the Laws (a more practical analysis of political and social issues).

Theory of Forms

At the heart of Plato's philosophy is his theory of Forms, or Ideas. Ultimately, his view of knowledge, his ethical theory, his psychology, his concept of the state, and his perspective on art must be understood in terms of this theory.

Theory of Knowledge

Plato's theory of Forms and his theory of knowledge are so interrelated that they must be discussed together. Influenced by Socrates, Plato was convinced that knowledge is attainable. He was also convinced of two essential characteristics of knowledge. First, knowledge must be certain and infallible. Second, knowledge must have as its object that which is genuinely real as contrasted with that which is an appearance only. Because that which is fully real must, for Plato, be fixed, permanent, and unchanging, he identified the real with the ideal realm of being as opposed to the physical world of becoming. One consequence of this view was Plato's rejection of empiricism, the claim that knowledge is derived from sense experience. He thought that propositions derived from sense experience have, at most, a degree of probability. They are not certain. Furthermore, the objects of sense experience are changeable phenomena of the physical world. Hence, objects of sense experience are not proper objects of knowledge.

Plato's own theory of knowledge is found in the Republic, particularly in his discussion of the image of the divided line and the myth of the cave. In the former, Plato distinguishes between two levels of awareness: opinion and knowledge. Claims or assertions about the physical or visible world, including both commonsense observations and the propositions of science, are opinions only. Some of these opinions are well founded; some are not; but none of them counts as genuine knowledge. The higher level of awareness is knowledge, because there reason, rather than sense experience, is involved. Reason, properly used, results in intellectual insights that are certain, and the objects of these rational insights are the abiding universals, the eternal Forms or substances that constitute the real world.

The myth of the cave describes individuals chained deep within the recesses of a cave. Bound so that vision is restricted, they cannot see one another. The only thing visible is the wall of the cave upon which appear shadows cast by models or statues of animals and objects that are passed before a brightly burning fire. Breaking free, one of the individuals escapes from the cave into the light of day. With the aid of the sun, that person sees for the first time the real world and returns to the cave with the message that the only things they have seen heretofore are shadows and appearances and that the real world awaits them if they are willing to struggle free of their bonds. The shadowy environment of the cave symbolizes for Plato the physical world of appearances. Escape into the sun-filled setting outside the cave symbolizes the transition to the real world, the world of full and perfect being, the world of Forms, which is the proper object of knowledge.

Nature of Forms

The theory of Forms may best be understood in terms of mathematical entities. A circle, for instance, is defined as a plane figure composed of a series of points, all of which are equidistant from a given point. No one has ever actually seen such a figure, however.

What people have actually seen are drawn figures that are more or less close approximations of the ideal circle. In fact, when mathematicians define a circle, the points referred to are not spatial points at all; they are logical points. They do not occupy space. Nevertheless, although the Form of a circle has never been seen - indeed, could never be seen - mathematicians and others do in fact know what a circle is. That they can define a circle is evidence that they know what it is. For Plato, therefore, the Form “circularity” exists, but not in the physical world of space and time. It exists as a changeless object in the world of Forms or Ideas, which can be known only by reason. Forms have greater reality than objects in the physical world both because of their perfection and stability and because they are models, resemblance to which gives ordinary physical objects whatever reality they have. Circularity, squareness, and triangularity are excellent examples, then, of what Plato meant by Forms. An object existing in the physical world may be called a circle or a square or a triangle only to the extent that it resembles (“participates in” is Plato's phrase) the Form “circularity” or “squareness” or “triangularity.”

Plato extended his theory beyond the realm of mathematics. Indeed, he was most interested in its application in the field of social ethics. The theory was his way of explaining how the same universal term can refer to so many particular things or events. The word justice, for example, can be applied to hundreds of particular acts because these acts have something in common, namely, their resemblance to, or participation in, the Form “justice”. An individual is human to the extent that he or she resembles or participates in the Form “humanness”. If “humanness” is defined in terms of being a rational animal, then an individual is human to the extent that he or she is rational. A particular act is courageous or cowardly to the extent that it participates in its Form. An object is beautiful to the extent that it participates in the Idea, or Form, of beauty. Everything in the world of space and time is what it is by virtue of its resemblance to, or participation in, its universal Form. The ability to define the universal term is evidence that one has grasped the Form to which that universal refers.

Plato conceived the Forms as arranged hierarchically; the supreme Form is the Form of the Good, which, like the sun in the myth of the cave, illuminates all the other Ideas. There is a sense in which the Form of the Good represents Plato's movement in the direction of an ultimate principle of explanation. Ultimately, the theory of Forms is intended to explain how one comes to know and also how things have come to be as they are. In philosophical language, Plato's theory of Forms is both an epistemological (theory of knowledge) and an ontological (theory of being) thesis.

Political Theory

The Republic, Plato's major political work, is concerned with the question of justice and therefore with the questions “what is a just state” and “who is a just individual?”

The ideal state, according to Plato, is composed of three classes. The economic structure of the state is maintained by the merchant class. Security needs are met by the military class, and political leadership is provided by the philosopher-kings. A particular person's class is determined by an educational process that begins at birth and proceeds until that person has reached the maximum level of education compatible with interest and ability. Those who complete the entire educational process become philosopher-kings. They are the ones whose minds have been so developed that they are able to grasp the Forms and, therefore, to make the wisest decisions. Indeed, Plato's ideal educational system is primarily structured so as to produce philosopher-kings.

Plato associates the traditional Greek virtues with the class structure of the ideal state. Temperance is the unique virtue of the artisan class; courage is the virtue peculiar to the military class; and wisdom characterizes the rulers. Justice, the fourth virtue, characterizes society as a whole. The just state is one in which each class performs its own function well without infringing on the activities of the other classes. Plato divides the human soul into three parts: the rational part, the will, and the appetites. The just person is the one in whom the rational element, supported by the will, controls the appetites. An obvious analogy exists here with the threefold class structure of the state, in which the enlightened philosopher-kings, supported by the soldiers, govern the rest of society.


Plato's ethical theory rests on the assumption that virtue is knowledge and can be taught, which has to be understood in terms of his theory of Forms. As indicated previously, the ultimate Form for Plato is the Form of the Good, and knowledge of this Form is the source of guidance in moral decision making. Plato also argued that to know the good is to do the good. The corollary of this is that anyone who behaves immorally does so out of ignorance. This conclusion follows from Plato's conviction that the moral person is the truly happy person, and because individuals always desire their own happiness, they always desire to do that which is moral.


Plato had an essentially antagonistic view of art and the artist, although he approved of certain religious and moralistic kinds of art. Again, his approach is related to his theory of Forms. A beautiful flower, for example, is a copy or imitation of the universal Forms “flowerness” and “beauty.” The physical flower is one step removed from reality, that is, the Forms. A picture of the flower is, therefore, two steps removed from reality. This also meant that the artist is two steps removed from knowledge, and, indeed, Plato's frequent criticism of the artists is that they lack genuine knowledge of what they are doing. Artistic creation, Plato observed, seems to be rooted in a kind of inspired madness.


Plato's influence throughout the history of philosophy has been monumental. When he died, Speusippus became head of the Academy. The school continued in existence until AD 529, when it was closed by the Byzantine emperor Justinian I, who objected to its pagan teachings. Plato's impact on Jewish thought is apparent in the work of the 1st-century Alexandrian philosopher Philo Judaeus. Neo-platonism, founded by the 3rd-century philosopher Plotinus, was an important later development of Platonism. The theologians Clement of Alexandria, Origen, and St. Augustine were early Christian exponents of a Platonic perspective. Platonic ideas have had a crucial role in the development of Christian theology and also in medieval Islamic thought .

During the Renaissance, the primary focus of Platonic influence was the Florentine Academy, founded in the 15th century near Florence. Under the leadership of Marsilio Ficino, members of the Academy studied Plato in the original Greek. In England, Platonism was revived in the 17th century by Ralph Cudworth and others who became known as the Cambridge Platonists. Plato's influence has been extended into the 20th century by such thinkers as Alfred North Whitehead, who once paid him tribute by describing the history of philosophy as simply “a series of footnotes to Plato.“

Major Works of Plato

- Apology
- Charmides
- Clitophon
- Cratylus
- Crito
- Epistles
- Euthydemus
- Euthyphro
- First Alcibiades
- Gorgias
- Hippias Major
- Ion
- Laches
- Laws
- Lysis
- Menexenus
- Meno
- Parmenides
- Phaedo
- Phaedrus
- Philebus
- Protagoras
- Republic
- Sophist
- Statesman
- Symposium
- Theaetetus
- Timaeus

Quotes from Plato

- "He who advises a sick man, whose manner of life is prejudicial to health, is clearly bound first of all to change his patient's manner of life." (from "Epistles")

- "There can be no happiness either for the community or for the individual man, unless he passes his life under the rule of righteousness with the guidance of wisdom." (from "Epistles")

- "We should consider it a lesser evil to suffer great wrongs and outrages than to do them." (from "Epistles")

- "What task in life could I have performed nobler than this, to write what is of great service to mankind and to bring the nature of things into the light for all to see?." (from "Epistles")

- "Even God is said not to be able to fight against necessity." (from "Laws")

- "The first and highest form of the state and of the government and of the law is that in which there prevails most widely the ancient saying, that "Friends have all things in common."" (from "Laws")

- "The great principle of all is that no one of either sex should be without a commander; nor should the mind of anyone be accustomed to do anything, either in jest or earnest, of his own motion, but in war and in peace he should look to and follow his leader, even in the least things being under his guidance; for example, he should stand or move, or exercise, or wash, or take his meals, or get up in the night to keep guard and deliver messages when he is bidden; and in the hour of danger he should not pursue and not retreat except by order of his superior; and in a word, not teach the soul or accustom her to know or understand how to do anything apart from others. ... And we ought in time of peace from youth upwards to practice this habit of commanding others, and of being commanded by others." (from "Laws")

- "Mankind must have laws and conform to them, or their life would be as bad as that of the most savage beast." (from "Laws")

- "The stronger shall rule, and the weaker be ruled." (from "Laws")

- "Very rich and very good at the same time he cannot be." (from "Laws")

- "We must believe the legislator when he tells us that the soul is in all respects superior to the body, and that even in life what makes each one of us to be what we are is only the soul." (from "Laws")

- "The good is the beautiful." (from "Lysis")

- "Beloved Pan, and all ye other gods who haunt this place, give me beauty in the inward soul; and may the outward and inward man be at one." (from "Phaedrus")

- "I must first know myself, as the Delphian inscription says; to be curious about that which is not my concern, while I am still in ignorance of my own self would be ridiculous." (from "Phaedrus")

- "Self-motion is the very idea and essence of the soul." (from "Phaedrus")

- "As to the people, they have no understanding, and only repeat what their rulers are pleased to tell them." (from "Protagoras")

- "Knowledge is the food of the soul." (from "Protagoras")

- "When a man is compelled to choose one of two evils, no one will choose the greater when he may have the less[er]." (from "Protagoras")

- "A man is not to be reverenced more than the truth." (from "The Republic")

- "All men believe in their hearts that injustice is far more profitable to the individual than justice." (from "The Republic")

- "All the pursuits of men are the pursuits of women also, but in all of them a woman is inferior to a man." (from "The Republic")

- "Any city, however small, is in fact divided into two, one the city of the poor, the other of the rich; these are at war with one another." (from "The Republic")

- "The beginning is the most important part of any work, especially in the case of a young and tender thing; for that is the time at which the character is being formed and the desired impression is more readily taken." (from "The Republic")

- "The best of us ... delight in giving way to sympathy, and are in raptures at the excellence of the poet who stirs our feelings most." (from "The Republic")

- "Do not use compulsion, but let early education be rather a sort of amusement." (from "The Republic")

- "The excessive increase of anything often causes a reaction in the opposite direction." (from "The Republic")

- "The first thing will be to establish a censorship of the writers of fiction, and let the censors receive any tale of fiction which is good, and reject the bad; and we will desire mothers and nurses to tell their children the authorized ones only." (from "The Republic")

- "The four political virtues: wisdom, temperance, courage, and justice." (from "The Republic")

- "God proclaims as a first principle to the rulers, and above all else, that there is nothing which they should so anxiously guard, or of which they are to be such good guardians, as of the purity of the race." (from "The Republic")

- "He said: Who then are the true philosophers? Those, I said, who are lovers of the vision of truth." (from "The Republic")

- "I have hardly ever known a mathematician who was capable of reasoning." (from "The Republic")

- "If ... the ruler catches anybody beside himself lying in the State ... he will punish him for introducing a practice which is equally subversive and destructive of ship or State." (from "The Republic")

- "If anyone at all is to have the privilege of lying, the rulers of the State should be the persons; and they, in their dealings either with enemies or with their own citizens, may be allowed to lie for the public good." (from "The Republic")

- "[In the cave allegory] those whose who are destitute of philosophy may be compared to prisoners in a cave, who are only able to look in one direction because they are bound, and who have a fire behind them and a wall in front. Between them and the wall there is nothing; all that they see are shadows of themselves, and of objects behind them, cast on the wall by the light of the fire. Inevitably they regard these shadows as real, and have no notion of the objects to which they are due. At last some man succeeds in escaping from the cave to the light of the sun; for the first time he sees real things, and becomes aware that he had hitherto been deceived by shadows. If he is the sort of philosopher who is fit to become a guardian, he will feel it is his duty to those who were formerly his fellow prisoners to go down again into the cave, instruct them as to the truth, and show them the way up. But he will have difficulty in persuading them, because, coming out of the sunlight, he will see shadows less clearly then they do, and will seem to them stupider than before his escape." (from "The Republic")

- "Knowledge which is acquired under compulsion obtains no hold on the mind." (from "The Republic")

- "[Man] only blames injustice who, owing to cowardice or age or some weakness, has not the power of being unjust. And this is proved by the fact that when he obtains the power, he immediately becomes unjust as far as he can be." (from "The Republic")

- "Of all the things of a man's soul which he has within him, justice is the greatest good and injustice the greatest evil." (from "The Republic")

- "Our aim in founding the State was not the disproportionate happiness of any one class, but the greatest happiness of the whole." (from "The Republic")

- "Philosophy, the noblest pursuit of all." (from "The Republic")

- "The ruler who is good for anything ought not to beg his subjects to be ruled by him." (from "The Republic")

- "To physician, in so far as he is a physician, considers his own good in what he prescribes, but the good of his patient; for the true physician is also a ruler having the human body as a subject, and is not a mere moneymaker." (from "The Republic")

- "The soul of man is immortal and imperishable." (from "The Republic")

- "The State in which the rulers are most reluctant to govern is always the best and most quietly governed, and the state in which they are most eager, the worst." (from "The Republic")

- "There are three classes of men-lovers of wisdom, lovers of honor, lovers of gain." (from "The Republic")

- "There are three distinct classes, any meddling of one with another, or the change of one into another, is the greatest harm to the State, and may be most justly termed evil-doing." (from "The Republic")

- "They deem him their worst enemy who tells them the truth." (from "The Republic")

- "This and no other is the root from which a tyrant springs: When he first appears, he is a protector." (from "The Republic")

- "This is the sort of medicine and this is the sort of law, which you will sanction in your state. They will minister to better natures, giving health both of soul and of body; but those who are diseased in their bodies they will leave to die, and the corrupt and incurable souls they will put an end to themselves. That is clearly the best thing both for the patients and for the State." (from "The Republic")

- "The true creator is necessity, which is the mother of our invention." (from "The Republic")

- "Tyranny is the wretchedest form of government and the rule of a king the happiest." (from "The Republic")

- "[The tyrant] is always stirring up some war or other, in order that the people may require a leader." (from "The Republic")

- "Until philosophers are kings, or the kings and princes of this world have the spirit and power of philosophy, and political greatness and wisdom meet in one, and those commoner natures who pursue either to the exclusion of the other are compelled to stand aside, cities will never have rest from their evils-no, nor the human race-and then only will this our State have a possibility of life and behold the light of day." (from "The Republic")

- "When riches and virtue are placed together in the scales of the balance, the one always rises as the other falls." (from "The Republic")

- "When such men are only private individuals and before they get power, this is their character: they associate entirely with their own flatterers or ready tools; or if they want anything from anybody, they in their turn are equally ready to bow down before them; they profess every sort of affection for them, but when they have gained their point they know them no more. ...
   They are always either the masters or servants and never the friends of anybody; the tyrant never tastes of true freedom or friendship." (from "The Republic")

- "He whom Love touches not walks in darkness." (from "Symposium")

- "Herein is the evil of ignorance, that he who is neither good nor wise is nevertheless satisfied with himself: he has no desire for that of which he feels no want." (from "Symposium")

- "Love ... has the greatest power, and is the source of all our happiness and harmony, and makes us friends with the gods who are above us, and with one another." (from "Symposium")

- "The creation of the world-that is to say, the world of civilized order-is the victory of persuasion over force." (from "Adventures of Ideas" by Alfred North Whitehead)

- "No matter: I will live so that none shall believe him." (from "Concord Days" by Bronson Alcott)

- "Poets utter great and wise things which they do not themselves understand." (from "Essays: First Series" by Ralph Waldo Emerson)

- "The end to aim at is assimilation to God." (from "Lives of Eminent Philosophers" by Diogenes Laertius)

- "The visible is a shadow cast by the invisible." (from "Strength to Love" by Martin Luther King, Jr.)

- "Wise men talk because they have something to say: fools because they have to say something."


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