"The safest general characterization of the European philosophical tradition is that it consists of a series of footnotes to Plato."
--Alfred North Whitehead, Process and Reality, 1929
Plato (c. 427 BC - c. 347 BC) was an immensely influential classical Greek philosopher, student of Socrates and teacher of Aristotle. His most famous work is The Republic (Greek Politeia, 'city') in which he outlines his vision of an "ideal" state. He also wrote the Laws and many dialogues in which Socrates is the main participant.
Plato was born in Athens, into a moderately well-to-do aristocratic family. His father was named Ariston and his mother Perictione. An ancestor, Glaucon, was one of the best-known members of the Athenian nobility. Plato's own real name was "Aristocles". The nickname Plato originates from wrestling circles, that much is agreed on. Since Plato means "broad," it probably refers either to his physical appearance or possibly wrestling stance or style.
He founded the Academy, one of the earliest known organized schools in Western civilization, named after the spot it was founded on, holy to the hero Academus. Aristotle was a student there for many years. It operated until it was closed by Justinian I of Byzantium in 529 A.D.
Plato became a pupil of Socrates in his youth, and--according to his own account, anyhow--attended his master's trial, though not his execution. Unlike Socrates, Plato wrote down his philosophical views and left a considerable number of manuscripts (see below). He was deeply affected by the city's treatment of Socrates: much of his early work enshrines his memories of his teacher, and much of his ethical writing suggests a desire to found a society where similar injustices could not occur.
Plato was also deeply influenced by the Pythagoreans, whose notions of numerical harmony have clear echoes in Plato's notion of the Forms (sometimes thus capitalized; see below); by Anaxagoras, who taught Socrates and who held that the mind or reason pervades everything; and by Parmenides, who argued the unity of all things.
In Plato's writings one finds the heliocentric theory of the universe long before it was advanced by Aristarchus (and revived still later and given a scientific footing by Copernicus, Galileo, and Kepler). One finds debates concerning aristocratic and democratic forms of government. One finds debates concerning the role of heredity and environment in human intelligence and personality long before the modern "nature versus nurture" debate began in the time of Hobbes and Locke, with its modern continuation in such controversial works as The Mismeasure of Man and The Bell Curve. One finds arguments for the subjectivity--and the objectivity--of human knowledge which foreshadow modern debates between Hume and Kant, or between the postmodernists and their opponents. Even the myth of the lost city or continent of Atlantis originates as an illustrative story told by Plato in his Timaeus and Critias.
Plato wrote his philosophy down mainly in the form of dialogues in which several characters discuss a topic by asking questions of one another. The early ones, where Socrates figures prominently and his own teaching style is used, are called the Socratic Dialogues. But the philosophy expressed in his dialogues changed a great deal over the course of Plato's life, and this makes it difficult to determine whether an opinion expressed in one of these dialogues is an idea of Socrates', or Plato's. (Plato himself appears only very briefly in two of the dialogues, and says nothing.) It is generally agreed that Plato's earlier works are more closely based on Socrates' thought, whereas his later writing increasingly breaks away with the views of his former teacher. In the middle dialogues, Socrates becomes a mouthpiece for Plato's own philosophy, and the question-and-answer style is more pro forma. The later dialogues are closer to being simply treatises, and Socrates is often absent or quiet.
Plato's Metaphysics: Platonism, or realismOne of Plato's legacies, and perhaps his greatest, was his dualistic metaphysics, often called (in metaphysics) simply "realism" or "Platonism." Whatever it is called, Plato's metaphysics divides the world into two distinct aspects: the intelligible world of "forms" and the perceptual world we see around us. He saw the perceptual world, and the things in it, as imperfect copies of the intelligible forms or ideas. These forms are unchangable and perfect, and are only comprehensible by the use of the intellect or understanding (i.e., a capacity of the mind that does not include sense-perception or imagination).
In the Republic Books VI and VII, Plato used a number of metaphors to explain his metaphysical views: the metaphor of the sun, the well-known allegory of the cave, and most explicitly, the divided line. Taken together, these metaphors convey a complex and, in places, difficult theory: there is something called The Form of the Good (often interpreted as Plato's God), which is the ultimate object of knowledge and which as it were sheds light on all the other forms (i.e., universals: abstract kinds and attributes) and from which all other forms "emanate." The Form of the Good does this in somewhat the same way as the sun sheds light on, or makes visible and "generates," things in the perceptual world. (See Plato's metaphor of the sun.) But indeed, in the perceptual world, the particular objects we see around us bear only a dim resemblance to the more ultimately real forms of Plato's intelligible world: it is as if we are seeing shadows of cut-out shapes on the walls of a cave, which are mere representations of the reality outside the cave, illuminated by the sun. (See Plato's allegory of the cave.) We can imagine everything in the universe represented on a line of increasing reality; it is divided once in the middle, and then once again in each of the resulting parts. The first division represents that between the intelligible and the perceptual worlds. Then there is a corresponding division in each of these worlds: the segment representing the perceptual world is divided into segments representing "real things" on the one hand, and shadows, reflections, and representations on the other. Similarly, the segment representing the intelligible world is divided into segments representing first principles and most general forms, on the one hand, and more derivative, "reflected" forms, on the other. (See the divided line of Plato.) The form of government derived from this philosophy turns out to be one of a rigidly fixed hierarchy of hereditary classes, in which the arts are mostly suppressed for the good of the state, the size of the city and its social classes is determined by mathematical formula, and eugenic measures are applied secretly by rigging the lotteries in which the right to reproduce is allocated. The tightness of connection of such government to the lofty and original philosophy in the book has been debated.
Plato's metaphysics, and particularly the dualism between the intelligible and the perceptual, would inspire later Neoplatonic thinkers (see Plotinus) and Gnosticism) and other metaphysical realists. For more on Platonic realism in general, see Platonic realism and the Forms.
Plato also had some influential opinions on the nature of knowledge and learning which he propounded in the Meno, which began with the question of whether virtue can be taught, and proceeded to expound the concepts of recollection, learning as the discovery of pre-existing knowledge, and right opinion, opinions which are correct but have no clear justification.
A short history of Plato scholarship
Plato's thought is often compared with that of his best and most famous student, Aristotle, whose reputation during the Middle Ages so completely eclipsed that of Plato that the Scholastic philosophers referred to Aristotle as "the Philosopher."
One of the characteristics of the Middle Ages was reliance on authority and on scholastic commentaries on writings of Plato and other historically important philosophers, rather than accessing their original works. In fact, Plato's original writings were essentially lost to western civilization until their reintroduction in the twelfth century through the Arab scholars who not only maintained the original Greek texts of the ancients, but expanded them by writing extensive commentaries and interpretations on Plato's and Aristotle's works (see Al-Farabi, Avicenna, Averroes). These were eventually translated into Latin and later, into the local vernacular.
Only in the Renaissance, with the general resurgence of interest in classical civilization, did knowledge of Plato's philosophy become more widespread. Many of the greatest early modern scientists (e.g., Galileo) and artists (with the support of the Plato-inspired Lorenzo de Medici) who broke with Scholasticism and fostered the flowering of the Renaissance saw Plato's philosophy as the basis for progress in the arts and sciences.
Today, Plato's reputation is as easily on a par with Aristotle's. Many college students have read Plato but not Aristotle, in large part because the former's greater accessibility.