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The Greek philosopher Plato was among the most important and creative thinkers of the ancient world. His work set forth most of the important problems and concepts of Western philosophy, psychology, logic, and politics, and his influence has remained profound from ancient to modern times.


Plato was born in Athens in c.428 BC. Both his parents were of distinguished Athenian families, and his stepfather, an associate of Pericles, was an active participant in the political and cultural life of Periclean Athens. Plato seems as a young man to have been destined for an aristocratic political career. The excesses of Athenian political life, however, both under the oligarchical rule (404-403) of the so-called Thirty Tyrants and under the restored democracy, seem to have led him to give up these ambitions. In particular, the execution (399) of SOCRATES had a profound effect on his plans. The older philosopher was a close friend of Plato's family, and Plato's writings attest to Socrates' great influence on him.

After Socrates' death Plato retired from active Athenian life and traveled widely for a number of years. In c.388 he journeyed to Italy and Sicily, where he became the friend of Dionysius the Elder, ruler of Syracuse, and his brother-in-law Dion. The following year he returned to Athens, where he founded the Academy, an institution devoted to research and instruction in philosophy and the sciences. Most of his life thereafter was spent in teaching and guiding the activities of the Academy. When Dionysius died (367), Dion invited Plato to return to Syracuse to undertake the philosophical education of the new ruler, Dionysius the Younger. Plato went, perhaps with the hope of founding the rule of a philosopher-king as envisioned in his work the Republic. The visit, however, ended (366) in failure. In 361, Plato went to Syracuse again. This visit proved even more disastrous, and he returned (360) to the Academy. Plato died in 348 or 347 BC.


Plato's published writings, of which apparently all are preserved, consist of some 26 dramatic dialogues on philosophical and related themes. To call them all dialogues is perhaps inaccurate; the Apology purports to be the speech made by Socrates at his trial, and a number of the works are substantially monologues. All, however, are dramatic in the sense that Plato places the discourse in the mouths of characters who may or may not be based on historical persons; Socrates is a focal character in all but a few of the dialogues. Critics agree that the dialogues are of a high literary quality; Plato is generally recognized as a master of the dialogue form and as one of the great prose stylists of the Greek language.

Early Dialogues

The precise chronological ordering of the dialogues remains unclear, but stylistic and thematic considerations suggest a rough division into three periods. The earliest dialogues, begun after 399 BC, are seen by many scholars as memorials to the life and teaching of Socrates. Three of them, the Euthyphro, APOLOGY, and CRITO, describe Socrates' conduct immediately before, during, and after his trial. The early writings include a series of short dialogues that end with no clear and definitive solution to the problems raised. Characteristically, Plato has Socrates ask questions of the form "What is X?" and insist that he wants not examples or instances of X but what it is to be X, the essential nature, or Form, of X. In the Charmides the discussion concerns the question "What is temperance?"; in the Laches, "What is courage?"; in the Euthyphro, "What is holiness?" The first book of the Republic may originally have been such a dialogue, devoted to the question "What is justice?"

Socrates holds that an understanding of the essential nature in each case is of primary importance, but he does not claim himself to have any such understanding. A formal mode of cross-examination called elenchus, in which the answers to questions put by Socrates are shown to result in a contradiction of the answerer's original statement, reveals the ignorance of the answerer as well. Typically, these answerers are self-professed experts (the title characters of the Gorgias and Protagoras, for example, were leading SOPHISTS); thus their inability to provide a definition is particularly noteworthy. In the Apology, Socrates describes his mission as one of exposing this ignorance, an exposure he takes to be a necessary preliminary to true wisdom. Although the dialogues appear to end in ignorance, the dialectical structure of each work is such that a complex and subtle understanding of the concept emerges.

Middle Dialogues

The dialogues of the middle period were begun after the founding of the Academy. Here more openly positive doctrines begin to emerge in the discourse of Socrates. The dialogues of this period include what is widely thought to be Plato's greatest work, the REPUBLIC. Beginning with a discussion on the nature of justice, the dialogue articulates a vision of an ideal political community and the education appropriate to the rulers of such a community. Justice is revealed to be a principle of each thing performing the function most appropriate to its nature, a principle of the proper adjudication of activity and being. In political terms, this principle is embodied in a society in which citizens perform the tasks for which they are best suited; in the individual human soul the principle is to be discovered when each part of the soul performs its proper and appropriate function. Reason in both instances is to rule, but in both the political community and the individual soul, justice is ideally coupled with the virtue of temperance, the harmony and self-mastery that results when all elements agree as to which should do what. Thus the rule of reason is not a tyranny but the harmonious rule of the happily unified individual and society.

In the middle books of this dialogue, Plato develops, as an account of the nature of being and understanding, the theory of Forms foreshadowed in his earlier writings. The Form is introduced as a principle explaining individual instances of being X, the very thing itself that is meant by the name X and that is the transcendent object of understanding what it is to be X. The Forms constitute a realm of unchanging being to which the world of individual changing objects is subordinate. The Form of good enjoys a unique status, responsible for the being and intelligibility of the world as a whole.

In the Theaetetus the nature of understanding itself is explored. A critique of suggested definitions shows that understanding, or knowledge, involves judgment concerning the being of things, not a mere acquaintance with them in perception or simple mental awareness. The Phaedo and the Symposium are dramatically elaborate pieces dealing, respectively, with death and love. The Phaedo, which represents Socrates' final hours, considers the nature of the soul and portrays the philosophical life as a separation of soul from body, which prepares the philosopher for death. In the dramatically powerful Symposium, Socrates portrays love as the creative attraction toward the beautiful and the good itself.

Late Dialogues

In the dialogues of the later period, begun after Plato returned from Syracuse, the figure of Socrates recedes into the background. In the Sophist and Statesman the central figure is an unnamed visitor from Elea. The Sophist shows how a proper understanding of appearance depends on an account of being and nonbeing and of the relation between particulars and Forms. In the Parmenides the theory of Forms comes under exacting scrutiny, and arguments are presented to show that the Forms cannot be entities of the same sort as those whose being they explain. The Timaeus presents a semimythical description of the origin and nature of the universe, and the Philebus considers the place of pleasure in the good life. In the Laws, Plato's longest and last work, a model constitution for an ideal city is considered.


Central to Plato's thought is the power of reason to reveal the intelligibility and order governing the changing world of appearance and to create, at both the political and the individual level, a harmonious and happy life. Socrates' view that virtue is a form of understanding and that the good life must consequently be grounded in knowledge is refined into the view that philosophical education is to effect a harmony between reason and passion, a life of self-mastery in which reason governs the will not as something alien to it but as its natural guide and source. The doctrine of recollection, according to which learning is the remembering of a wisdom that the soul enjoyed prior to its incarnation, is a mythical statement of this view that neither reason nor the intelligible order that it reveals is alien to the human soul.

This order--seen by Plato as providing an account both of the being and of the intelligibility of the world of appearance--is articulated in the theory of Forms. Forms are the principles of being in the world, of the fact that the world presents itself as instances of being this or that, as well as the principles of human understanding of those instances of being. The nature and intelligibility of the world of appearance can thus be accounted for, in Plato's view, only by recognizing it as an "image" of the truly intelligible structure of being itself, which is the world of Forms. The relationship between Forms and particulars, or between the world of being and the world of appearance, was recognized by Plato to be deeply problematic. He remained clear, however, that no theory could fail to recognize both features of the world without falling prey to either the relativism of Heraclitus or the monism of Parmenides, both of which destroy the very possibility of being and understanding.

The world of being, itself governed by the Form of the good, is seen by Plato as also the source of value and the object of proper desire. The philosopher is thus pictured as in love with the Forms, that is, in love with the world as it truly is. His wish to see through the world of flux to the true principles of its being is thus basically an act of love. This love is not simply an attraction to the good but a creative force for the procreation of the good. Directed toward others, it is the power of education, the bringing to birth of understanding and virtue through the process of dialectic, as portrayed in Socrates' relation to the youths about him.

Reason for Plato, as for the Greek tradition in general, is most clearly manifest in LOGOS, the word, and language, as the medium in which reason articulates being, is a central topic throughout the dialogues. Plato was impressed by the fact that language has the capacity both to articulate the intelligibility of the world and to belie the world's true being. He constantly addresses the question of how to purge language of its potential deceptiveness, how to win the fidelity of words to the world. Bad poetry and bad rhetoric alike are pathological forms of the inescapable dissociation of word and world; the Platonic question is how to make this dissociation benign. The central vehicle that Plato envisions for this purpose is dialectic, the dialogue that refines and articulates the true shape and tendency of speech and understanding. This dialectic is presented mimetically in the dialogues themselves, which are thus not simply presentations of philosophical views but representations of philosophy at work, of human beings engaged in the distinctively human and highly civilized activity of rational conversation.


The influence of Plato's thought is seen in the continuing vitality of the Platonic tradition through subsequent centuries. The major philosophers of late Hellenism, most notably PLOTINUS and PROCLUS, were self-professed Platonists. After the closing of the Academy, NEOPLATONISM continued to flourish in the Islamic and Byzantine world, and Latin Neoplatonism was a strong intellectual factor throughout the Middle Ages. During the Renaissance there occurred a great rebirth of Platonic thought in the West. The Byzantine philosopher Giorgius Gemistus Pletho (c.1355-1452) introduced the study of Plato to Renaissance Florence, and the subsequent translations and commentaries of Marsilio FICINO and others laid the groundwork for a flourishing school of Platonic thought in the Florentine Academy. In 17th-century England the rationalistic theologians known as the CAMBRIDGE PLATONISTS based much of their thinking on Plato. The 19th and 20th centuries have witnessed, besides the important influence of Plato on the romantic movement, the development of a strong Anglo-European tradition of Platonic scholarship.

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L. A. Kosman

Bibliography: Friedlander, Paul, Plato, trans. by Hans Meyerhoff, 3 vols. (1958-69); Gosling, J. C. B., Plato (1973; repr. 1984); Grube, G. M. A., Plato's Thought (1935; repr. 1980); Hall, R.W., Plato (1981); Hamilton, Edith, and Cairns, Huntington, eds., The Collected Dialogues of Plato Including the Letters (1961); Koyre, Alexandre, Discovering Plato, trans. by L. C. Rosenfield (1945); Melling, D.J., Understanding Plato (1987); Randall, John Herman, Jr., Plato, Dramatist of the Life of Reason (1970); Ryle, Gilbert, Plato's Progress (1966); Shorey, Paul, What Plato Said (1933); Taylor, A. E., Plato: The Man and His Work, 4th ed. (1937); Vlastos, Gregory, ed., Plato, a Collection of Critical Essays, 2 vols. (1971); Woodbridge, F. J. E., The Son of Apollo (1929).

Picture Caption[s]

The Greek philosopher Plato (c.428-347 BC) remains one of the most influential thinkers in Western civilization. Plato's dialogues, in their exploration of the basic questions raised by philosophical inquiries, were seminal works in the history of thought. Plato was a pupil of Socrates, and his interest in education led to his founding (387 BC) of the Academy in Athens. (The Bettmann Archive)