Plato

Plato (c. 428/427–348/347 BCE) was an Athenian philosopher, a follower of Socrates and the teacher of Aristotle. He is one of the most influential thinkers in history: his writings raised questions about justice, knowledge, reality, the soul, love, beauty and the best way to organize society that philosophers still discuss today.

Unlike most ancient authors, Plato’s entire body of work appears to have survived. He wrote dialogues—dramatic conversations between characters, usually led by Socrates. Plato himself never speaks in them, which makes it an intriguing challenge to work out what Plato himself believed.

Around 387 BCE he founded the Academy, a community for study and research in Athens, often described as a forerunner of the university. The twentieth-century philosopher Alfred North Whitehead famously remarked that the European philosophical tradition could be characterized as a series of footnotes to Plato—an exaggeration, but one that shows his importance.

Plato was born into a wealthy and politically prominent Athenian family. His father was Ariston and his mother Perictione; his brothers Glaucon and Adeimantus appear as characters in the Republic. Relatives on his mother’s side, Critias and Charmides, were leading members of the Thirty, the pro-Spartan oligarchy that ruled Athens briefly and violently in 404–403 BCE. According to the late ancient biographer Diogenes Laertius, “Plato” was a nickname, perhaps meaning “broad,” and his given name was Aristocles; this story is uncertain.

As a young man Plato joined the circle of Socrates. In 399 BCE, under the restored democracy, Socrates was tried on charges of impiety and corrupting the young and was executed by drinking hemlock. The event shaped Plato’s life and work. In the Seventh Letter (whose authenticity is debated), the author explains that he turned away from a political career in disgust at both the oligarchs and the democrats.

After Socrates’ death Plato reportedly spent time in Megara and travelled; stories of visits to Egypt and Cyrene are uncertain. He went to southern Italy, where he likely met the Pythagorean philosopher and statesman Archytas of Tarentum, and to Syracuse in Sicily, the court of the tyrant Dionysius I, where he befriended Dion. He returned to Sicily twice (around 367 and 361 BCE) in the hope of educating Dionysius II as a philosopher-ruler; both visits ended badly.

Plato founded the Academy around 387 BCE and taught there for about forty years. Aristotle arrived in 367 BCE and stayed for twenty years. Plato died in Athens around 348/347 BCE and was succeeded as head of the Academy by his nephew Speusippus.

Plato was born during the Peloponnesian War (431–404 BCE) between Athens and Sparta, and grew up as the Athenian democracy—which had built the Parthenon and flourished after the Persian Wars—waged a long and ultimately disastrous war. Athens was defeated in 404 BCE, briefly ruled by the Thirty, then restored as a democracy. These upheavals made questions about justice, leadership and the stability of states urgent.

Athens was also a centre of intellectual life. Sophists—professional teachers who taught rhetoric and argument for pay—travelled through Greek cities, and some claimed that justice and morality were matters of convention or power rather than nature. Earlier philosophers such as Heraclitus, Parmenides and the Pythagoreans had offered competing accounts of change, being and number. Plato’s dialogues respond to all these currents.

In a wider frame, Plato’s century saw the rise of Macedon, the Persian Achaemenid empire at its height, and in China the teachings of Mozi and Mencius. Plato died a decade before Philip II of Macedon’s victory at Chaeronea (338 BCE) and about a generation before Alexander the Great spread Greek culture across the Near East.

The Platonic corpus as arranged in antiquity by Thrasyllus (1st century CE) contains 36 “works” in nine groups of four (tetralogies): 35 dialogues and the Letters counted as one. Modern scholars consider several of these spurious or doubtful (for example Alcibiades II, Hipparchus, Theages), and the authenticity of a few others, such as Alcibiades I and Epinomis, is debated.

Scholars often group the dialogues into three periods. Early or “Socratic” dialogues (such as Euthyphro, Apology, Crito, Laches, Charmides) show Socrates questioning people about a virtue and ending without a definite answer (aporia, “impasse”). Middle dialogues (Phaedo, Symposium, Republic, Phaedrus) present bold theories about the Forms, the soul and the ideal city. Late dialogues (Theaetetus, Parmenides, Sophist, Statesman, Philebus, Timaeus, Critias, Laws) are more technical, sometimes criticize the earlier theory, and often give Socrates a smaller role; the Laws does not include him at all.

The dialogue form is part of the philosophy. Plato shows ideas being tested in conversation, with characters of different ages and views, set in specific places and times—the prison where Socrates awaits death (Crito, Phaedo), a drinking party (Symposium), a walk outside the city walls (Phaedrus). He also uses myths: the ring of Gyges, the myth of Er, Atlantis, and the charioteer of the soul.

Plato’s best-known idea is the theory of Forms (or Ideas; Greek eidos, idea). Beautiful things in the world come and go and are beautiful only in some ways; but Beauty itself—what makes them beautiful—is eternal, unchanging and perfectly what it is. The same holds for Justice, Equality, the Good and other Forms. For Plato, the Forms are the most real things, known by reason rather than by the senses.

In the Republic, Plato illustrates this with three linked images. The Sun: as the sun gives light and life to visible things, the Form of the Good gives truth and being to the Forms. The Divided Line: a line divided into sections representing images, physical things, mathematical objects and Forms, each more real and clearly known than the last. And the Cave (Republic Book VII): prisoners who see only shadows cast by firelight; one is freed, climbs painfully into the sunlight, and eventually sees the sun itself—then returns to free the others, who may ridicule or even kill him.

The theory is not presented as a finished system. In the Parmenides, the young Socrates is sharply challenged, including by the “Third Man” argument, which asks whether the Forms lead to an infinite regress. How Plato responded to these difficulties—whether he revised, abandoned or maintained the theory—is one of the great questions of Platonic scholarship.

For Plato the soul (psyche) is the true self, distinct from the body and, in the Phaedo, immortal. In the Meno, Socrates helps an untaught slave boy solve a geometry problem through questions alone, which he uses to argue that learning is really “recollection” (anamnesis)—the soul remembering what it knew before birth.

In the Republic and Phaedrus, Plato divides the soul into three parts: reason, spirit (thumos, the part associated with anger and honour) and appetite. In the Phaedrus this is pictured as a charioteer (reason) driving two horses, one noble and one unruly. Justice in the soul is harmony, with reason ruling, spirit supporting it, and appetite kept in check.

In the Theaetetus, Plato examines definitions of knowledge—as perception, as true belief, and as true belief with an “account” (logos)—and finds problems with each. This dialogue remains a foundational text in the theory of knowledge (epistemology).

In the Symposium, guests at a drinking party give speeches praising Eros (love). The comic poet Aristophanes tells a myth of original double humans split in two, each half forever seeking its partner. Socrates recounts the teaching of a wise woman, Diotima: love is a desire for the good and for immortality, and it can lead a person up a “ladder” from love of one beautiful body to love of all beauty, of souls, laws and knowledge, and finally to the vision of Beauty itself. The popular term “Platonic love” derives, loosely, from this dialogue.

The Timaeus offers an account of the creation of the cosmos by a divine craftsman (demiurge), who shapes the world as a living being on the model of the eternal Forms, using mathematical proportions and the elementary triangles of the four elements. It is presented as a “likely story” rather than certain knowledge. The Timaeus and Critias also introduce the story of Atlantis.

Plato’s ethics begins with Socrates’ claim, in the Apology, that the unexamined life is not worth living for a human being. The dialogues ask what virtue is, whether it can be taught, and whether it is better to suffer injustice than to do it (as Socrates argues in the Gorgias). Plato consistently holds that virtue is the key to happiness (eudaimonia, flourishing).

The Republic asks: what is justice, and is the just person happier than the unjust, even if no one knows? To answer, Socrates builds an ideal city in words, with three classes—rulers (guardians), auxiliaries (soldiers) and producers—mirroring the three parts of the soul. Guardians receive a long education in music, gymnastics, mathematics and dialectic; they hold no private property; women can be guardians on equal terms with men; and, most famously, there will be no end to troubles until philosophers become rulers or rulers become philosophers (Republic 473c–d).

The Republic also criticizes poetry and art as imitations far removed from truth and capable of corrupting character, and analyses how regimes decline from aristocracy through timocracy, oligarchy and democracy to tyranny. In his last and longest work, the Laws, Plato designs a more practical city, Magnesia, governed by detailed laws with preambles meant to persuade citizens.

Plato’s school took its name from the Akademeia, a sacred grove and gymnasium outside the walls of Athens associated with the hero Hekademos (Akademos). There Plato and his associates studied mathematics, astronomy, political theory and philosophy. Tradition says that the entrance bore the inscription “Let no one ignorant of geometry enter,” but this is attested only in late sources.

Members included the mathematicians Eudoxus of Cnidus and Theaetetus, and, for twenty years, Aristotle. Diogenes Laertius mentions two women who studied there, Axiothea of Phlius and Lastheneia of Mantinea. Members of the Academy were reportedly invited to help draft laws for various Greek cities.

After Plato the Academy passed through several phases, including a “skeptical” period under Arcesilaus and Carneades. Its activities at the original site ended around the time of the Roman general Sulla’s siege of Athens in 86 BCE. A Neoplatonist school later flourished in Athens until the sixth century CE; its decline is traditionally linked to a decree of Emperor Justinian in 529 CE.

In late antiquity, Neoplatonists such as Plotinus (3rd century CE) and Proclus (5th century CE) developed Plato’s ideas into a comprehensive metaphysical and religious system that profoundly influenced Christian theology (notably Augustine), as well as Jewish and Islamic thought.

For centuries in the Latin West the Timaeus was the only dialogue widely available (in the partial Latin translation of Calcidius, 4th century CE), so medieval European thinkers knew Plato above all as a cosmologist.

In the Islamic world, Plato (Aflāṭūn) was known through Arabic translations and summaries, some made at centres such as Baghdad’s House of Wisdom. Al-Farabi (d. 950) wrote on the philosophy of Plato and summarized the Laws, and his idea of the “virtuous city” draws on the Republic. Averroes (Ibn Rushd, 1126–1198) wrote a commentary on the Republic, which survives in Hebrew translation.

Byzantine scholars preserved Plato’s Greek text. At the Council of Florence (1438–1439), the Byzantine philosopher Gemistos Plethon stirred interest in Plato among Italian humanists. Marsilio Ficino translated the complete dialogues into Latin (printed 1484) under Medici patronage, and the first printed Greek edition was issued by Aldus Manutius in Venice in 1513. Since then Plato has been a constant presence in Western philosophy, political theory, literature and education, and his works are read in translation across the world, including in East Asia since the late nineteenth century.

The Socratic problem: Socrates wrote nothing, so our picture of him depends on Plato, Xenophon, Aristophanes’ comedy Clouds and remarks by Aristotle. How much of Plato’s “Socrates” is the historical Socrates? Gregory Vlastos influentially argued that the early dialogues represent the historical Socrates’ philosophy and the middle dialogues Plato’s own; many scholars, including Charles Kahn, have challenged this, arguing that even the “early” dialogues are Plato’s literary and philosophical constructions.

Chronology and development: The order of the dialogues is uncertain. Stylometry—statistical study of style, pioneered by Lewis Campbell in 1867—confirms a group of late works close to the Laws, which ancient testimony says was unfinished at Plato’s death, but it cannot securely order the early and middle dialogues. “Developmentalists” read the corpus as recording changes in Plato’s views; “unitarians” see a largely consistent philosophy presented from different angles.

Unwritten doctrines: Aristotle refers to Plato’s “unwritten teachings” (agrapha dogmata), apparently involving first principles called the One and the Indefinite Dyad. The “Tübingen school” (Hans Joachim Krämer, Konrad Gaiser) and later Giovanni Reale argued that these oral doctrines are the key to Plato’s real philosophy; most Anglophone scholars are skeptical and focus on the dialogues. The authenticity of the Seventh Letter, which criticizes writing philosophy down, is also disputed.

Politics: Karl Popper’s The Open Society and Its Enemies (1945) attacked Plato as a forerunner of totalitarianism; defenders reply that this reads the Republic too literally, ignores its irony and aims, or neglects the Laws. Feminist scholars have debated whether Book V’s female guardians show a proto-feminist position or subordinate women’s interests to the state.

Plato’s text comes down to us mainly through Byzantine manuscripts. The oldest complete medieval manuscript of the first six tetralogies is the “Clarke Plato” (Oxford, Bodleian Library, MS E. D. Clarke 39), copied in 895 CE for Arethas of Caesarea. Another key manuscript is Parisinus graecus 1807, from the ninth century, containing the last tetralogies including the Republic and Laws. Papyrus fragments from Egypt, such as those found at Oxyrhynchus, provide older but partial evidence.

Ancient biographical information comes from the Letters (of uncertain authenticity), Aristotle, and later writers, above all Diogenes Laertius’ Lives of Eminent Philosophers (Book III, probably 3rd century CE), which mixes reliable information with anecdote. Many “facts” in popular accounts, such as Plato’s wrestling career or original name, rest on this late testimony.

Plato is cited by Stephanus numbers—page numbers and section letters from Henri Estienne’s (Stephanus’) Greek edition of 1578, such as Republic 514a for the beginning of the cave allegory. The standard modern Greek text is the Oxford Classical Texts edition; a widely used English collection is Plato: Complete Works, edited by John M. Cooper (Hackett, 1997). The Greek text and English translations are also available online through the Perseus Digital Library.

Because Plato never speaks in his own voice, readers must decide how to relate the arguments to the dramatic context. A claim made by Socrates to a particular person, for a particular purpose, may not be Plato’s settled doctrine. Attention to irony, character, setting and the dialogue’s ending (for example, aporia) is part of philosophical interpretation, not a distraction from it.

Key Greek terms resist translation: eidos/idea (Form, Idea), psyche (soul, mind, life), aretē (virtue, excellence), dikaiosynē (justice, righteousness), eros (love, desire). Modern associations—such as “idea” meaning a mental thought, or “Platonic love” meaning non-physical friendship—can mislead.

Finally, “Platonism” has meant many things across two and a half millennia: Neoplatonic mysticism, Christian and Islamic theology, Renaissance humanism, and modern “mathematical Platonism” (the view that numbers exist independently of minds). Distinguishing Plato’s own texts from later Platonisms is an essential scholarly habit.