Ancient Greek Philosophy

Ancient Greek philosophy is the tradition of argued inquiry that began in the Greek cities of the eastern Aegean in the early sixth century BCE and reached its classical height in Athens with Socrates, Plato and Aristotle. Over about two and a half centuries, from Thales of Miletus around 585 BCE to the death of Aristotle in 322 BCE, a small number of thinkers scattered across the Greek world set out to explain nature, knowledge, the good life and the just city by reasoning and observation rather than by appeal to myth or the authority of priests and poets.

Its importance is hard to overstate. The vocabulary of Western thought, including the words philosophy, logic, ethics, physics, politics and metaphysics, comes from this period, and so do many of its enduring questions: what the world is ultimately made of, whether change is real, whether morality is natural or merely conventional, and what kind of knowledge is possible. Greek philosophy was not the only early tradition of systematic thought. At roughly the same time Indian philosophy and Chinese philosophy were taking shape, and the Buddha and Confucius were near contemporaries of the early Greek thinkers. But the Greek line, carried forward by Hellenistic and Roman philosophy and later by Arabic and Latin scholars, became the root of the philosophical traditions of Europe and the Islamic world.

In the sixth century BCE there was no Greek state. The Greek world of ancient Greece was a patchwork of several hundred independent city-states, each a polis with its own laws, gods and politics, stretching from the coast of Asia Minor in modern Turkey to Sicily, southern Italy and the shores of the Black Sea. Trade, colonisation and war kept these cities in constant contact with older civilisations. Greek merchants and mercenaries knew ancient Egypt, the Levantine ports of Phoenicia and the kingdoms of Mesopotamia, and from the 540s the cities of Ionia fell under the rule of the Achaemenid Empire of Persia.

Why systematic philosophy emerged here is debated. Historians point to a combination of factors: the absence of a powerful priestly class with a fixed sacred text, a culture of public argument in assemblies and law courts, the spread of alphabetic writing, contact with Egyptian and Babylonian mathematics and astronomy, and the wealth of trading cities such as Miletus. None of these alone explains the change, and the early thinkers drew freely on the poetry of Homer and Hesiod even as they criticised it.

A basic difficulty shapes everything known about this first phase. Almost none of the early philosophers' writings survive whole. What remains are fragments quoted by later authors, sometimes centuries later, and summaries of their views by Aristotle, his pupil Theophrastus and later compilers. Modern scholars still cite these scraps using the numbering of the edition by Hermann Diels and Walther Kranz. The thinkers before Socrates are conventionally called the Presocratics, although several were his contemporaries.

The story traditionally begins in Miletus, a rich Ionian port on the coast of Asia Minor. Thales of Miletus, active in the early sixth century, is reported to have held that water is the origin of all things and to have predicted the solar eclipse of 585 BCE, though that prediction is doubted by modern scholars. He left no writings, and his reputation as the first philosopher rests largely on Aristotle, who saw in him the first attempt to name a single underlying material from which everything comes.

His younger fellow citizens took the idea further. Anaximander argued that the source of things could not be any familiar substance such as water, since each element would overwhelm its opposite. He called it the apeiron, the boundless or indefinite, out of which opposites such as hot and cold separate. He is also credited with an early map of the known world and with an account of the earth hanging unsupported at the centre of the cosmos. Anaximenes chose air, and explained how air could become fire, water or stone by thinning and thickening. That move mattered: it replaced a story of origins with a mechanism that, in principle, accounted for change by a single process.

Pythagoras, born on the island of Samos, moved to Croton in southern Italy around 530 BCE and founded a community whose members followed strict rules of diet and conduct. He wrote nothing, and later admirers attributed so much to him, including the famous theorem, that the historical figure is very hard to recover. What seems secure is that he taught the immortality and transmigration of the soul and a disciplined way of life. His followers, among them Philolaus in the later fifth century, developed the idea that number and ratio underlie the order of the cosmos, inspired in part by the discovery that musical harmonies correspond to simple numerical ratios.

Xenophanes of Colophon, a wandering poet, attacked the gods of Homer for behaving like badly behaved humans, and observed that if horses could draw they would draw gods shaped like horses. He proposed instead a single greatest god unlike mortals, and was cautious about how far human beings could ever know the truth.

Heraclitus of Ephesus, writing around 500 BCE in a deliberately riddling style, held that the world is ever-living fire and in constant change, yet ordered by a rational principle he called the logos. His best-known images, such as the river into which one cannot step twice, express the idea that stability is produced by the balanced tension of opposites. He scorned those who piled up information without understanding, a criticism aimed at predecessors including Pythagoras.

The sharpest turn came in the Greek west. Parmenides of Elea, a colony on the Italian coast, wrote a poem in which a goddess shows him two paths, the way of truth and the way of mortal opinion. His central argument is that one cannot think or speak of what is not. From this he concluded that what is can neither come into being nor perish, since it would have to come from or pass into nothing; that it cannot be divided or move; and that the changing world of the senses is therefore an illusion.

The argument was startling, and its influence was enormous, because it forced every later thinker to explain how change and plurality could be real without violating its logic. His follower Zeno of Elea defended him with paradoxes, the best known showing that the swift Achilles can never overtake a tortoise if space is infinitely divisible. Melissus of Samos argued along similar lines that reality is one and unlimited.

The next generation accepted part of Parmenides' challenge: nothing truly comes from nothing. They answered it by positing several unchanging basic realities whose mixing and separating produces the appearance of change. Empedocles of Acragas in Sicily named four roots, earth, water, air and fire, moved by two forces he called Love and Strife, which alternately unite and divide them in a cosmic cycle. This scheme of four elements would survive, through Aristotle, into the early modern period. Anaxagoras of Clazomenae, who brought philosophy to Athens in the mid-fifth century, held that everything contains a portion of everything else and that an intelligence, Nous or Mind, set the original mixture spinning. He was reportedly prosecuted for impiety for calling the sun a fiery stone, and his friendship with Pericles may have made him a political target.

The most radical answer came from Leucippus and his pupil Democritus of Abdera in northern Greece. They proposed that reality consists of countless tiny, indivisible bodies, atoms, moving through empty space. Atoms differ only in shape, size and arrangement; colours, tastes and warmth exist only by convention, in the experience of the perceiver. The theory kept Parmenides' unchanging being, now broken into many pieces, while making motion possible through the void. Democritus also wrote extensively on ethics, recommending cheerfulness and moderation, though little of his huge output survives.

By the middle of the fifth century the centre of Greek intellectual life had shifted to Athens. The city had led the Greek resistance in the Greco-Persian Wars, from the Battle of Marathon in 490 BCE to the naval victory at Salamis in 480, and then built a maritime empire whose tribute paid for the Parthenon and for a radical democracy. In the assembly and the courts, citizens decided policy and lawsuits by persuasion, and the ability to speak well became the key to influence.

Into this market came the Sophists, travelling teachers who charged fees to instruct ambitious young men in rhetoric, argument and the skills of public life. Protagoras of Abdera, the most celebrated, declared that a human being is the measure of all things, usually taken to mean that truth is relative to the person or community judging. He also professed agnosticism about the gods. Gorgias of Leontini in Sicily, who dazzled Athens as an ambassador in 427 BCE, wrote a provocative treatise arguing that nothing exists, that if it did it could not be known, and that if known it could not be communicated. Others, such as Prodicus with his studies of word meanings and Hippias with his encyclopaedic learning, broadened the curriculum.

The Sophists' most influential theme was the contrast between physis, nature, and nomos, law or convention. If laws and moral codes differ from city to city, are they simply human inventions? Some argued that justice is a convention that restrains the natural desires of the strong. Much of what is known about the Sophists comes from Plato, who portrayed them as hucksters selling cleverness rather than wisdom, and gave the word sophistry its bad name. Modern scholars treat them more sympathetically, as serious thinkers about language, society and knowledge. The historian Herodotus, with his comparisons of the customs of different peoples, and the medical writers associated with Hippocrates, who sought natural causes of disease, belong to the same climate of inquiry.

Socrates, born in Athens in 469 BCE, the son of a stonemason and a midwife, wrote nothing. He spent his life in the public spaces of the city questioning anyone who would talk to him about courage, justice, piety and virtue. His method, known as the elenchus, was to ask for a definition, draw out its consequences and show that it conflicted with other things the speaker believed. The result was usually puzzlement rather than a final answer, but Socrates held that recognising one's own ignorance was the beginning of wisdom and that the unexamined life was not worth living. He seems to have believed that virtue is a kind of knowledge, so that no one does wrong willingly, and that caring for the soul matters more than wealth or reputation.

Socrates lived through the Peloponnesian War of 431 to 404 BCE, which ended in Athens' defeat by Sparta and a brief, brutal oligarchy, the Thirty Tyrants. Several of his associates, including Alcibiades and Critias, were notorious figures in these events. In 399 BCE, after democracy had been restored, he was prosecuted for impiety and for corrupting the young, convicted by a jury of several hundred citizens, and executed by drinking hemlock.

Because he left no writings, the historical Socrates must be pieced together from three very different sources: the comic playwright Aristophanes, who mocked him in the Clouds of 423 BCE as a crank teaching students to make the weaker argument the stronger; the soldier and writer Xenophon, whose Socrates is a practical moral adviser; and Plato, whose dialogues are the richest portrait but also vehicles for Plato's own ideas. Separating the two is known as the Socratic problem, and it has no agreed solution.

Plato, born around 428 BCE into a prominent Athenian family, was one of the young men around Socrates, and the execution of his teacher turned him away from a political career. He travelled, probably visiting southern Italy, where he encountered Pythagorean thought, and Syracuse in Sicily, where he later made two ill-fated attempts to influence its tyrant Dionysius II, if the letters attributed to him can be trusted. Around 387 BCE he founded the Academy, a school in a sacred grove outside the walls of Athens, which would last in one form or another for some three centuries.

Plato wrote dialogues rather than treatises, almost all of them with Socrates as the main speaker. Scholars traditionally divide them into early dialogues, which stay close to Socratic questioning about definitions; middle dialogues such as the Phaedo, Symposium and Republic, which set out bold theories; and late dialogues such as the Sophist, Timaeus and Laws, which revisit and criticise those theories. Whether this sequence reflects the order of writing and a real development in Plato's views is disputed.

His best-known doctrine is the theory of Forms. Beyond the changing objects of the senses, Plato argued, there are eternal and unchanging realities, the Form of Beauty, the Form of Justice, the Form of Equality, of which particular beautiful or just things are imperfect copies. Only the Forms can be truly known; the physical world offers only opinion. The theory answered both Heraclitus and Parmenides: the sensible world is in flux, but there is a realm of stable being that the mind can grasp. In the Republic, Plato pictured ordinary people as prisoners in a cave who mistake shadows for reality, and the philosopher as one who climbs out into the sunlight of the Good. He combined this with arguments that the soul is immortal and that learning is a kind of recollection of what the soul knew before birth.

The Republic also offers Plato's response to the Sophists' challenge. Against the claim that justice serves only the interests of the stronger, he argued that justice is a harmony of the soul in which reason governs spirit and appetite, and that the just person is happier than the unjust. The ideal city mirrors this order, ruled by philosopher-kings, guarded by a class without private property or family, and supported by producers. The scheme has been read as a utopia, a satire and a blueprint for authoritarian rule. In his last work, the Laws, Plato sketched a more practical constitution based on the rule of law.

Aristotle was born in 384 BCE at Stagira in Chalcidice, on the edge of the kingdom of Macedon, where his father served as court physician. He joined the Academy at about seventeen and stayed for twenty years, until Plato's death in 347. He then spent time in Asia Minor and on Lesbos, doing pioneering work in biology, and around 343 was engaged by Philip II of Macedon to tutor his son, the future Alexander the Great. In 335 he returned to Athens and founded his own school at the Lyceum, where he and his students collected books, natural specimens and the constitutions of 158 Greek cities.

Aristotle's surviving works, about thirty of perhaps two hundred, are mostly lecture notes and working drafts rather than polished books. Their range is extraordinary. In logic, he created the first formal system, the theory of the syllogism, which set out which patterns of argument are valid regardless of their content; it remained the core of logic until the nineteenth century. In metaphysics, he argued that the primary realities are individual substances, this man or this horse, rather than separate Forms. Every natural object is a compound of matter and form, the form being the structure and capacities that make it the kind of thing it is. To understand anything, he held, one must know four kinds of cause: what it is made of, what its form is, what brought it about and what it is for.

That last cause, the purpose or end, made his view of nature teleological: acorns grow in order to become oaks, eyes exist for seeing. His ethics follows the same pattern. Human beings, like everything else, have a characteristic function, which for them is the exercise of reason, and their good is eudaimonia, flourishing, achieved through a lifetime of virtuous activity. Virtues of character are settled habits lying in a mean between excess and deficiency, and they are acquired by practice, as one becomes a builder by building. In the Politics he described the human being as an animal made for life in a polis, compared constitutions and favoured a mixed regime. He also defended natural slavery and the subordination of women, views that reflected and justified the society around him.

Aristotle's method differed from his teacher's in emphasis. Where Plato looked beyond the senses, Aristotle began with careful observation and with the opinions of earlier thinkers and ordinary people, then worked through the puzzles they raised. His Poetics and Rhetoric applied the same analytic approach to tragedy and persuasion.

While Plato and Aristotle taught, the political world of the city-states was being overturned. Philip II made Macedon the dominant power in Greece, defeating Athens and Thebes at Chaeronea in 338 BCE. His son Alexander then conquered the Persian Empire, carrying Greek rule and culture as far as Egypt, Central Asia and the Indus, and creating the Macedonian Empire. When Alexander died in Babylon in 323, anti-Macedonian feeling erupted in Athens and Aristotle, long associated with the Macedonian court, was threatened with a charge of impiety. He withdrew to Chalcis on Euboea, reportedly so that the Athenians would not sin twice against philosophy, and died there in 322.

His death is the conventional end of the classical period. Philosophy did not decline, but its setting changed. The independent polis gave way to the large kingdoms of Alexander's successors, and new schools in Athens, the Stoics, the Epicureans and the Sceptics, asked how individuals could live well in a vast and uncertain world. That story continues in the Hellenistic and Roman schools and in the wider culture of the Hellenistic period.

The texts of Plato and Aristotle had a long and winding afterlife. Platonism, reshaped by Plotinus in the third century CE, deeply influenced early Christian thinkers such as Augustine of Hippo. Aristotle's works, organised by later editors, were translated from Greek through Syriac into Arabic in Baghdad under the Abbasid Caliphate, where philosophers such as Avicenna and Averroes wrote commentaries on them. From the twelfth century, Latin translations made from Arabic and from Greek returned them to western Europe, where Thomas Aquinas and other scholastics called Aristotle simply the Philosopher. These later chapters belong to Islamic and Jewish philosophy and medieval Christian philosophy.

The questions the Greeks posed still frame much of philosophy: the atomists anticipated, in outline, the physical picture of modern science; Parmenides' arguments still trouble metaphysicians; and the debate between Plato's view that knowledge lies beyond the senses and Aristotle's insistence on starting from experience runs through the whole later history of the subject.