All men by nature desire to know.
It is owing to their wonder that men both now begin and at first began to philosophise.
Sometime in the early sixth century BCE, in the harbour town of Miletus on the coast of Asia Minor, a man named Thales proposed that everything was, at bottom, water. The claim itself matters less than its grammar: a single, natural, impersonal arche (ἀρχή) — origin — without recourse to gods. Aristotle would later count Thales as the first philosopher, and the discipline as we now know it begins with that gesture of substitution.
His successors Anaximander and Anaximenes pressed on — toward the boundless (apeiron) and toward air. The pre-Socratics were physicists and metaphysicians at once. They asked what stuff the world is made of and how change is possible.
By the fifth century BCE the centre of gravity had shifted to Athens. The Sophists arrived selling rhetoric; Socrates arrived asking, in the agora, what justice is. He wrote nothing. His pupil Plato wrote dialogues. Plato's pupil Aristotle wrote treatises on almost everything. After their deaths the Hellenistic schools — Epicureans, Stoics, Sceptics — turned philosophy toward the practical question of how to live.
This deck moves through the four traditional eras: pre-Socratic, classical, Aristotelian, Hellenistic.
You cannot step twice into the same river.
The first to propose a single material principle. Predicted (according to Herodotus I.74) the eclipse of 28 May 585 BCE. "All things are full of gods," he is said to have remarked.
The "obscure" of Ephesus. Reality is fire and flux, held in tension by the logos. DK B 51: opposition itself produces harmony, "as in the bow and the lyre."
Of Elea. In a hexameter poem on Truth and on Opinion, argued that what is, is, and what is not, cannot be. Change is illusion. Being is one, eternal, undivided.
Defended Parmenides with paradoxes. The arrow never moves; Achilles never overtakes the tortoise. The first known reductio ad absurdum arguments in the Western tradition.
With Leucippus, founded atomism. Reality is atoms (uncuttables) moving in the void. "By convention sweet, by convention bitter — but in reality atoms and void." (DK 68 B 9)
Founder of a brotherhood at Croton. "All is number." Fragments of his school survive only in later quotation, but the geometric soul of Greek philosophy descends from them.
The unexamined life is not worth living for a human being.
Socrates (c. 470 — 399 BCE) was an Athenian stonemason's son who turned the city into a classroom. He claimed to know nothing, asked everyone everything, and was eventually tried for impiety and corrupting the youth. He drank the hemlock. He wrote nothing — what we have is in Plato (mostly), Xenophon, and Aristophanes (who mocked him in The Clouds).
The Socratic method. By questioning, expose contradictions in your interlocutor's beliefs. Definition is the goal: What is justice? What is courage? What is piety? The method is captured in early dialogues (Euthyphro, Charmides, Laches). The interlocutor leaves perplexed (aporia). That perplexity is itself the beginning of knowledge.
The safest general characterisation of the European philosophical tradition is that it consists of a series of footnotes to Plato.
Plato (c. 428 — c. 348 BCE), Athenian aristocrat, founded the Academy in a sacred grove outside the city around 387 BCE. The institution would last almost a thousand years. He wrote dialogues, never treatises; Socrates is the central character of nearly all of them, though by the late dialogues Socrates is more or less Plato in costume.
The prisoners take shadows for reality. One escapes, climbs out into the sunlight, sees the Forms — and then, returning to the cave, is laughed at and threatened. Plato's image is at once epistemology (degrees of knowledge from eikasia to noēsis), psychology (the painful turn of the soul) and political (the philosopher who returns to govern is rarely thanked).
For Plato, beyond the changing world of sensation lies a realm of unchanging Forms (eidē): Justice itself, Beauty itself, Triangle itself. Particulars participate in (methexis) Forms. The visible world is a copy; mathematical objects are intermediate; Forms are intelligible; above them all stands the Form of the Good (Republic 508–509).
| Dialogue | Subject | Famous moment |
|---|---|---|
| Apology | Trial of Socrates | "I know that I know nothing." |
| Meno | Virtue, recollection | The slave-boy proves a geometric theorem. |
| Symposium | The nature of love | Diotima's ladder of beauty. |
| Phaedo | Immortality of soul | Socrates drinks the hemlock. |
| Republic | Justice; ideal city | Cave; divided line; sun. |
| Timaeus | Cosmology | The Demiurge; the receptacle. |
| Parmenides | Self-criticism of Forms | The "third man" regress. |
Plato is dear to me, but dearer still is truth.
Aristotle (384–322 BCE) of Stagira spent twenty years in Plato's Academy, then tutored the boy Alexander, then founded his own school in 335 BCE just outside Athens. His followers were Peripatetics — those who walk about. The corpus that survives, as edited by Andronicus of Rhodes around 60 BCE, covers logic, biology, physics, metaphysics, ethics, politics, rhetoric, poetics — almost the whole shape of the later university.
Where Plato pointed up, Raphael's School of Athens has Aristotle pointing across — at this world, the world of substances, of cabbages and tortoises and constitutions to be classified.
Each virtue is a mean between two vices — one of excess, one of deficiency. Courage stands between rashness and cowardice; generosity between prodigality and stinginess; modesty between shamelessness and bashfulness. Virtue is not a felt rule but a disposition, formed by habit, exercised with phronesis (practical wisdom), aimed at eudaimonia — flourishing, the activity of the soul in accordance with virtue, in a complete life.
| Vice (deficiency) | Virtue (mean) | Vice (excess) |
|---|---|---|
| cowardice | courage | rashness |
| insensibility | temperance | self-indulgence |
| stinginess | liberality | prodigality |
| pusillanimity | magnanimity | vanity |
| obsequiousness | friendliness | quarrelsomeness |
If some A is B, and all B is C, then some A is C.
In the Prior Analytics Aristotle invents formal logic. A syllogism is a deduction in which, certain things being supposed, something else necessarily follows. The classical figure:
This is mood Barbara — three universal affirmatives, in the first figure. Aristotle classified all valid moods. His Organon (Categories, On Interpretation, Prior & Posterior Analytics, Topics, Sophistical Refutations) governed Western logic for two thousand years, until Frege.
Death is nothing to us. When we exist, death is not; when death exists, we are not.
Epicurus taught in his Garden in Athens. Atomism inherited from Democritus; ethics aimed at ataraxia (untroubledness) through modest pleasure, friendship, and freedom from religious fear. Lucretius's De Rerum Natura is the great surviving Latin poem of the school.
Zeno of Citium taught in the Stoa Poikile (painted porch). Live in agreement with nature; the only true good is virtue; externals are indifferent. See Deck 09. Chrysippus, Seneca, Epictetus, Marcus Aurelius extend the school across five centuries.
Pyrrho counselled suspension of judgment (epochē); for every argument an equal counter-argument can be found. The Academic Sceptics (Arcesilaus, Carneades) made Plato's school a school of doubt. Sextus Empiricus's Outlines of Pyrrhonism (c. 200 CE) is the surviving manual.
Diogenes of Sinope lived in a barrel and asked Alexander to step out of his sunlight. Virtue is sufficient for happiness; convention is corruption. The Cynic provocations seeded both Stoicism and the long European tradition of philosophical scandal.
Plutarch and others kept Plato's flame, fusing him with Pythagoras and emerging mystical strands. Sets the scene for Plotinus.
Plotinus's Enneads describe the One, the Intellect, the Soul. The world is an emanation; the philosopher's task is the return. Through Augustine, this vocabulary enters Christian theology.
The Parthenon, completed in 438 BCE, was already a few decades old when Socrates began his loitering in the agora below. The buildings outlasted the philosophers; the philosophers' arguments outlasted the buildings. Both are still being read for the same reason: nothing else fitting has been built in their place.
| Author | Work | Date (approx) | Note |
|---|---|---|---|
| Heraclitus | On Nature (fragments, Diels-Kranz B 1–139) | c. 500 BCE | only fragments survive |
| Parmenides | On Nature (poem) | c. 475 BCE | Way of Truth, Way of Opinion |
| Plato | Republic | c. 380 BCE | justice, the soul, the city |
| Plato | Timaeus | c. 360 BCE | cosmology |
| Aristotle | Nicomachean Ethics | c. 340 BCE | virtue, eudaimonia |
| Aristotle | Metaphysics | c. 340 BCE | "first philosophy" |
| Aristotle | Politics | c. 335 BCE | man as zoon politikon |
| Epicurus | Letter to Menoeceus | c. 300 BCE | ethical programme |
| Lucretius | De Rerum Natura | c. 55 BCE | Latin Epicurean poem |
| Sextus Empiricus | Outlines of Pyrrhonism | c. 200 CE | sceptical handbook |
| Plotinus | Enneads | c. 270 CE | edited by Porphyry |
Origin, principle. The pre-Socratic search for what underlies the world.
Word, reason, account. For Heraclitus, the rational order of the cosmos; for Aristotle, the ordering of arguments.
Perplexity, the dead-end produced by Socratic questioning — and the necessary first step.
Flourishing, "the good life." Translated as happiness, but more like activity well lived.
Excellence, virtue — of a horse, a knife, or a person.
Practical wisdom; the capacity to deliberate well about how to live.
Form, look. Plato's intelligible objects; Aristotle's substantial form.
Substance, being. The central question of Aristotle's Metaphysics Z.
Tranquility, freedom from disturbance — the goal alike of Epicureans, Stoics, Sceptics.
The vocabulary of Western thought is still mostly Greek. We say theory and physics and politics, ethics and logic and metaphysics, with no awareness that these are all loanwords from a single small culture by the Aegean. The Greeks did not invent thinking — Egyptians and Mesopotamians and Indians thought beautifully too — but they did invent a particular self-conscious style of it: argued, public, written down, willing to follow an argument wherever it leads.
Modern virtue ethics (Anscombe, MacIntyre, Foot) is a deliberate return to Aristotle. Stoicism has been quietly reborn in cognitive behavioural therapy and in popular self-help. Plato's Forms shadow every debate about mathematical realism. The Sceptics are reborn whenever a scientist asks whether observation is theory-laden.
And the basic situation has not changed. We are mortal animals who live together in cities and quarrel about how to live. The Greeks were the first to put that situation in writing, with arguments rather than myths, and to ask who is responsible for it. They are not always right. They held slaves, distrusted democracy, despised manual labour. But they are still the conversation. To do philosophy in English in 2026 is to argue with them, however indirectly, about how to be a person.
Philosophy is the love of wisdom. Etymology is destiny.
An hour with the BBC's flagship discussion programme — Melvyn Bragg with three professors of ancient philosophy. The episode below treats Plato's Republic; the channel has scores more.
Watch · BBC In Our Time · Plato's Republic
All things flow.
Deck 01 of Philosophy · Vol. VI · The Deck Catalog