Aristotle

For more than a thousand years, in Arabic, Hebrew and Latin, he was simply called “the Philosopher”. Dante placed him in Limbo as il maestro di color che sanno — “the master of those who know”. Aristotle founded formal logic, invented biology as a systematic science, wrote the first treatises on ethics, politics, rhetoric, poetics, psychology and metaphysics as distinct disciplines, and shaped the vocabulary in which we still think: substance, essence, category, energy, potential, matter, form, cause, principle, induction, syllogism, catharsis.

He was also, in a way his teacher Plato was not, an observer. Where Plato looked up from the world to the eternal Forms, Aristotle looked down at the world — at octopuses, embryos, constitutions, tragedies and friendships — and found the forms there, in the things themselves. Raphael’s School of Athens catches it: Plato points to the heavens; Aristotle holds his hand flat, palm down, toward the earth.

This essay covers his life, the shape of his work, and his main doctrines in logic, physics, biology, psychology, metaphysics, ethics, politics and poetics, with the classic objections and his long afterlife in three religions.

Life

Stagira and the Academy

Aristotle was born in 384 BCE at Stagira, a small Greek town on the Chalcidice peninsula in the north Aegean. His father, Nicomachus, was physician to King Amyntas III of Macedon (the grandfather of Alexander the Great), and the family belonged to the Asclepiadae, a guild of physicians. Both parents died when he was young.

At seventeen, in 367, he was sent to Athens and entered Plato‘s Academy. He stayed for twenty years — as student, researcher and teacher — until Plato’s death in 348/7. Ancient anecdotes say Plato called him “the reader” and “the mind of the school”, and that their relationship cooled; but it is clear that Aristotle’s thought was formed by constant argument with Platonism. Even his criticisms of the Forms are written in the first person plural: “we” Platonists.

Assos, Lesbos and the lagoon

When Plato died, the leadership of the Academy went to his nephew Speusippus. Aristotle left Athens — perhaps from disappointment, perhaps because anti-Macedonian feeling made Athens uncomfortable after Philip of Macedon sacked the city of Olynthus in 348. He went to Assos on the coast of Asia Minor, at the invitation of Hermias, a former slave who had become ruler of the region and a friend of philosophers. Aristotle married Hermias’s niece (or adopted daughter) Pythias. When Hermias was betrayed to the Persians and tortured to death, Aristotle wrote a hymn in his memory.

From Assos he moved to the island of Lesbos, where he worked with Theophrastus, a native of the island who would become his successor. It was here, around the lagoon of Pyrrha (the modern Kalloni), that Aristotle conducted much of the biological research recorded in his zoological works: dissecting, observing and questioning fishermen. The biologist Armand Marie Leroi’s book The Lagoon (2014) reconstructs this work and argues that Aristotle invented the science of biology there.

Tutor to Alexander

In 343/2 Philip II invited Aristotle to Macedon to tutor his thirteen-year-old son Alexander, at Mieza. What Aristotle taught him, and how much influence he had, is unknown; the stories (that Alexander slept with an annotated Iliad under his pillow, that he sent his teacher specimens from Asia) are probably later inventions. Their views certainly diverged: Aristotle advised treating Greeks as friends and “barbarians” as plants or animals; Alexander married Persian princesses and wanted to fuse the peoples.

The Lyceum

In 335, after Alexander’s accession, Aristotle returned to Athens and founded his own school in a gymnasium sacred to Apollo Lyceius — the Lyceum. Because he taught while walking in its covered walkway (peripatos), his followers were called the Peripatetics. The Lyceum was a research institute: Aristotle and his students assembled a library, collected constitutions of 158 Greek cities (only the Constitution of Athens survives, rediscovered on papyrus in 1890), compiled lists of victors at the Pythian games, and organized research in botany (Theophrastus), the history of mathematics (Eudemus), and the history of philosophy.

His wife Pythias died; he then lived with Herpyllis, by whom he had a son, Nicomachus — after whom (or by whom) the Nicomachean Ethics may be named.

Exile and death

When Alexander died in 323, anti-Macedonian feeling exploded in Athens. Aristotle was charged with impiety (the pretext was his hymn to Hermias). Remembering Socrates, he left for Chalcis on Euboea, his mother’s hometown, reportedly saying he would not allow the Athenians “to sin twice against philosophy”. He died there in 322, aged sixty-two. His will, preserved by Diogenes Laertius, is humane: it provides for Herpyllis, frees several slaves, and asks that Pythias’s bones be buried with his.

The corpus

What survives

Aristotle wrote two kinds of works. The exoteric works — dialogues and popular writings intended for publication — were admired in antiquity for their style; Cicero spoke of Aristotle’s “golden stream of eloquence”. Almost all are lost.

What survives are the esoteric or acroamatic works — lecture notes, research files and treatises for use within the school. They are dense, compressed, often repetitive, full of false starts, puzzles and cross-references. They are about a fifth of what he wrote, perhaps a million words.

A famous (and probably embellished) story told by Strabo holds that after Theophrastus’s death the manuscripts were hidden in a cellar at Scepsis in Asia Minor to keep them from the kings of Pergamon, rotted for a century and a half, were bought by a book collector, taken to Rome by Sulla, and finally edited by Andronicus of Rhodes in the first century BCE, who gave the corpus the arrangement we still use.

The map of knowledge

Aristotle divided knowledge into three kinds:

Kind	Aim	Disciplines
Theoretical	Truth for its own sake	First philosophy (metaphysics/theology), mathematics, natural philosophy (physics, biology, psychology)
Practical	Acting well	Ethics, politics
Productive	Making things	Rhetoric, poetics, the crafts

Logic is not one of the sciences but their instrument (organon) — hence the name later given to his logical works.

Logic

The Organon

The six works of the Organon are: Categories, On Interpretation, Prior Analytics, Posterior Analytics, Topics, and Sophistical Refutations. Together they constitute the first systematic logic in history. Immanuel Kant wrote in 1787 that logic had not had to take a single step backward since Aristotle, nor been able to take a single step forward, and “to all appearance seems to be finished and complete”. (Frege, a century later, proved him wrong.)

Terms and propositions

On Interpretation analyses simple statements of the form “S is P” by quantity (universal or particular) and quality (affirmative or negative), yielding the four standard forms later labelled A, E, I and O:

Form	Example	Name
A	All humans are mortal	Universal affirmative
E	No humans are mortal	Universal negative
I	Some humans are mortal	Particular affirmative
O	Some humans are not mortal	Particular negative

Their logical relations — contradictories, contraries, subcontraries — were later arranged in the “square of opposition”. The same work contains the famous sea-battle puzzle (ch. 9): if it is already true today that there will be a sea-battle tomorrow, is the battle necessary? Aristotle seems to answer that statements about future contingents are not yet true or false — an early challenge to the principle of bivalence that still interests logicians.

The syllogism

The Prior Analytics defines a syllogism (sullogismos, “reckoning together”) as “a discourse in which, certain things being stated, something other than what is stated follows of necessity from their being so” (24b18). Its paradigm is the categorical syllogism with two premises sharing a “middle term”:

All animals are mortal. All humans are animals. Therefore all humans are mortal.

Aristotle systematically examined every combination of premise forms in three “figures”, determined which are valid, and proved their validity — reducing the imperfect syllogisms to the perfect ones of the first figure. Medieval logicians gave the valid moods mnemonic names: Barbara, Celarent, Darii, Ferio… This is the first formal system in history — the first time anyone recognized that validity depends on form, using letters as variables.

Demonstration and first principles

The Posterior Analytics asks what scientific knowledge (epistēmē) is. To know something scientifically is to know its cause, and to know that it could not be otherwise. Scientific knowledge is expressed in demonstrations: syllogisms whose premises are true, primary, immediate, better known than, prior to, and causes of the conclusion.

But demonstrations must start somewhere; if every premise needed proof, there would be an infinite regress. So there must be first principles grasped not by demonstration but by nous — intellectual insight — which arises from perception, memory and experience through induction (epagōgē). The chapter that ends the work (II.19) describes how a universal emerges from many perceptions “like a rout in battle stopped by first one man making a stand and then another, until the original formation has been restored”.

The principle of non-contradiction

In Metaphysics IV, Aristotle defends “the firmest of all principles”: “it is impossible for the same thing at the same time to belong and not to belong to the same thing in the same respect” (1005b19). It cannot be proved — any proof would presuppose it — but it can be defended elenctically: anyone who denies it must say something definite, and in doing so relies on it. Someone who refuses to say anything definite “is no better than a vegetable” (1006a15).

Dialectic and fallacies

The Topics is a handbook of dialectical argument — reasoning from reputable opinions (endoxa) rather than from first principles — and Aristotle’s own method often begins with the endoxa, surveys the puzzles (aporiai), and tries to save as much of the received opinion as possible. Sophistical Refutations is the first catalogue of fallacies: equivocation, amphiboly, begging the question, false cause, many questions, and more.

Categories and substance

The short Categories — perhaps the most influential philosophical text ever written, measured by commentaries — classifies “things that are said” into ten kinds:

Category	Example
Substance	man, horse
Quantity	two cubits long
Quality	white, grammatical
Relation	double, half, larger
Place	in the Lyceum
Time	yesterday
Position	lying, sitting
Having (state)	shod, armed
Action	cutting
Passion (being acted on)	being cut

Substance is primary. “Primary substances” are individuals — this man, this horse — which are neither “said of” nor “in” any subject; they are the ultimate subjects of predication. Everything else exists only as a property of, or relation among, substances. Whiteness exists only as the whiteness of something. “Secondary substances” are the species and genera (man, animal) to which individuals belong.

This is a direct inversion of Plato. For Plato, the universal (the Form of Man) is most real and particulars are shadows. For the Aristotle of the Categories, the particular — Socrates — is most real, and “man” exists only because individual men do.

Nature, change and the four causes

Nature

The Physics is the study of nature (phusis), defined as “a principle of motion and rest in that to which it belongs primarily” (192b21). Natural things — animals, plants, the elements — have their source of change within them; artifacts do not. A bed, if planted, would not sprout a bed; if anything, a tree.

Matter, form and privation

The Presocratics and Parmenides had argued that change is impossible: what comes to be must come either from what is (in which case it already is) or from what is not (and nothing comes from nothing). Aristotle’s answer is that every change involves three things: a subject (matter) that persists, a form it acquires, and a privation (lack of that form) from which it starts. When the unmusical man becomes musical, the man persists, losing unmusicality and gaining musicality. Change does not come from sheer nothing, but from something-lacking-something.

Potentiality and actuality

The deeper tool is the distinction between potentiality (dunamis) and actuality (energeia, entelecheia). The acorn is potentially an oak; the oak is the acorn’s actuality. Bronze is potentially a statue. A sleeping geometer is potentially, and a geometer doing geometry is actually, contemplating. Motion is defined (with notorious compression) as “the actuality of what potentially is, as such” (201a10) — the actualizing of a potential while it is still being actualized.

Our words “energy” and “potential” come from these terms.

The four causes

To understand anything, says Aristotle, is to grasp its “why” (dia ti) — its causes (aitiai, better translated “explanations” or “becauses”). There are four:

Cause	Question	Statue example	Oak example
Material	What is it made of?	Bronze	Wood, sap, cells
Formal	What is it? Its essence or structure	The shape of Pericles	The form and organization of an oak
Efficient	What produced it?	The sculptor	The parent oak
Final	What is it for? Its end (telos)	To honour Pericles	To be a flourishing oak

In natural things, form, end and efficient cause often coincide: the form of the oak is what the acorn grows toward and what the parent oak transmits.

Teleology

Aristotle insists that nature acts for the sake of something. “Nature does nothing in vain” (Politics 1253a9). He considers the objection — anticipating Darwin — that perhaps teeth simply happen to grow sharp in front and broad behind, and the animals with such teeth survived while others perished, “as Empedocles says the man-faced ox-progeny did” (Physics II.8, 198b). He rejects it: what happens always or for the most part cannot be due to chance; and natural processes are regular, so they must be for an end.

This is the most contested part of his physics. Modern biology explains apparent design by natural selection; but philosophers of biology note that “function” talk — the heart is for pumping blood — remains indispensable, and some describe it as “Aristotelian teleology naturalized”.

Place, time, void, infinity

The Physics also contains Aristotle’s analysis of place (the inner boundary of the containing body), time (“the number of motion in respect of before and after”, 219b1), the infinite (which exists only potentially — you can always divide further — never as an actual completed totality), and the void (which he argues cannot exist). He offers solutions to Parmenides‘s pupil Zeno’s paradoxes of motion.

The heavens and the elements

In On the Heavens, the cosmos is spherical, finite, eternal, and divided into two regions. Below the moon, four elements — earth, water, air, fire — move naturally in straight lines toward or away from the centre: heavy things fall, light things rise. Above the moon, the stars and planets are made of a fifth element (aithēr, later “quintessence”) whose natural motion is eternal circular rotation. Heavier bodies fall faster in proportion to their weight — a claim Galileo would demolish (though not, probably, by dropping balls from the Leaning Tower).

This picture, systematized by Ptolemy, held for nearly two thousand years. Its collapse in the Scientific Revolution — Copernicus, Kepler, Galileo, Newton — was in large part the collapse of Aristotelian physics.

The biologist

A science invented

About a quarter of Aristotle’s surviving works are biological: History of Animals, Parts of Animals, Generation of Animals, Movement of Animals, and shorter treatises. He describes some five hundred species. His observations were often astonishing:

• He described the hectocotylus, the modified arm male octopuses use to transfer sperm — dismissed as a fable until the nineteenth century.
• He reported that the smooth dogfish nourishes its embryo through a placenta-like structure — confirmed by Johannes Müller in 1842.
• He followed the development of the chick embryo day by day, opening eggs at intervals, and saw the heart beating as a speck of blood on the third day.
• He classified dolphins and whales with land mammals, not fish, because they breathe air and bear live young nursed with milk.

He also made famous errors: that men have more teeth than women, that the heart (not the brain) is the seat of thought (the brain cools the blood), that in reproduction the male provides the form and the female only the matter.

His great methodological lecture, Parts of Animals I.5, defends the study of humble creatures against those who prefer the heavens. He quotes Heraclitus, who, when visitors hesitated to enter because they found him warming himself at the kitchen stove, told them “come in, there are gods here too” — and says we should approach every animal without distaste, “for each of them will reveal to us something natural and something beautiful” (645a).

Charles Darwin, sent a new translation in 1882, wrote: “Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere school-boys to old Aristotle.”

The ladder of nature

Aristotle arranged living things on a graded scale — from plants through sponges and shellfish to animals with blood and finally humans — though he recognized that the boundaries are fuzzy: “nature proceeds little by little from things lifeless to animal life in such a way that it is impossible to determine the exact line of demarcation” (History of Animals 588b4). The medieval “great chain of being” grew from this.

The soul

The soul as form of the body

On the Soul (De Anima) is the founding text of psychology — but “psychology” in a broad sense, since every living thing has a psuchē. The soul is not a separate thing lodged in the body, as Plato held, but the form of a natural body that has life potentially — more precisely, its “first actuality” (412a27). The soul is to the body as the shape is to the wax, or as sight is to the eye: “if the eye were an animal, sight would be its soul” (412b18).

So it makes no more sense to ask whether soul and body are one than to ask whether the wax and its shape are one. This hylomorphism — neither dualism nor reductive materialism — has been revived by some contemporary philosophers of mind as a third way.

Levels of soul

There are nested capacities:

• Nutritive soul — growth, nutrition, reproduction; all living things, including plants.
• Sensitive soul — perception, desire, locomotion; animals.
• Rational soul — thought; humans.

Perception and thought

Perception is the reception of the form of the perceived object without its matter, “as wax receives the impression of a signet ring without the iron or gold” (424a19). Each sense has its proper object (colour for sight, sound for hearing), but there are “common sensibles” (motion, shape, number) perceived by several senses, and a “common sense” that unifies them. Phantasia — imagination or appearance — mediates between perception and thought: “the soul never thinks without an image” (431a16).

Thinking is like perceiving: the intellect becomes, in a way, what it thinks — “the soul is, in a way, all things” (431b21).

The active intellect

The most mysterious passage in Aristotle is De Anima III.5, barely a dozen lines long. There is an intellect that “becomes all things” and one that “makes all things”, like light making potential colours actual; the latter is “separable, impassive, unmixed”, “immortal and eternal”. Is this active intellect part of each human soul, or a single divine intellect shared by all? The question divided the Greek commentators (Alexander of Aphrodisias identified it with God), the Arabic philosophers (Averroes argued for a single intellect for all humankind), and the Latin West (Aquinas wrote a treatise On the Unity of the Intellect against the Averroists). It remains open.

First philosophy

Being qua being

The Metaphysics is fourteen books assembled by editors; the title means simply “after the Physics”. It begins: “All men by nature desire to know” (980a21) — a sign of which is our delight in the senses, especially sight. Wisdom is knowledge of first causes; and philosophy begins in wonder.

Aristotle describes the subject of the Metaphysics in several ways: the study of first causes; the study of being qua being (to on hēi on) — of what belongs to beings simply insofar as they are; the study of substance; and theology. How these fit together is a long-running puzzle.

“Being is said in many ways” (1003a33), but always with reference to one central sense — as “healthy” is said of medicine, complexions and exercise in reference to health. Scholars call this pros hen (“toward one”) equivocity. The central sense of being is substance (ousia).

What is substance?

Books VII–IX (Zeta, Eta, Theta), among the most difficult texts in philosophy, ask what substance is. Candidates: the subject (substratum), the essence, the universal, the genus. Matter fails (it is not separable or a “this”); the universal fails (against Plato: no universal is a substance). Aristotle concludes — or seems to — that substance in the primary sense is form, understood as essence (to ti ēn einai, literally “the what-it-was-to-be”), the actuality that makes a parcel of matter this kind of thing. Whether form here is individual or universal is fiercely debated.

The unmoved mover

Book XII (Lambda) contains Aristotle’s theology. Motion is eternal (time cannot have a beginning — a “before” the beginning would be a time). Eternal motion requires an eternal cause. That cause cannot itself be in motion, or we would need a further cause. So there must be an unmoved mover — pure actuality with no potentiality, hence immaterial.

How does it move the heavens without moving? As an object of love moves the lover (1072b3): the outermost heavenly sphere, desiring to imitate its perfection, moves in eternal circular motion; the rest of the cosmos follows.

What does this god do? It thinks — and since it must think the best thing, it thinks itself: “its thinking is a thinking of thinking” (noēsis noēseōs, 1074b34). It does not know or care about the world. “On such a principle, then, depend the heavens and the world of nature” (1072b14).

This impersonal god, borrowed and transformed, became the god of the “first mover” argument in Avicenna, Maimonides and Aquinas’s First Way.

Ethics

The human good

The Nicomachean Ethics — the most widely read of his works — begins: “Every art and every inquiry, and similarly every action and pursuit, is thought to aim at some good” (1094a1). Some goods are sought for the sake of others; there must be one sought for its own sake, or desire would be “empty and vain”. Everyone agrees on its name: eudaimonia — happiness, flourishing, living well (see Eudaimonia). But what is it? Pleasure? Honour? Wealth? Aristotle rejects each.

He warns at the outset that ethics cannot have the precision of mathematics: “it is the mark of an educated person to look for precision in each class of things just so far as the nature of the subject admits” (1094b23). And the student must already have been raised with good habits; lectures will not make the wicked good.

The function argument

To find the good of a human being, ask what a human being’s function (ergon) is, as the good of a flute-player lies in playing the flute well. Living is shared with plants; perceiving with animals. What is distinctive of humans is the activity of the soul in accordance with reason. So the human good is “activity of soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete” — and, he adds, “in a complete life. For one swallow does not make a spring, nor does one day” (1098a16–19).

Virtue as a mean

Virtue (aretē, “excellence”) is a state of character (hexis) — a settled disposition, acquired by habituation: “we become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts” (1103b1). (The popular saying “we are what we repeatedly do; excellence, then, is not an act but a habit” is Will Durant’s paraphrase, not Aristotle’s sentence.)

Each moral virtue is a mean between two vices, one of excess, one of deficiency — relative to us, as the right amount of food differs for the wrestler Milo and for a beginner:

Sphere	Deficiency	Mean (virtue)	Excess
Fear and confidence	Cowardice	Courage	Rashness
Pleasures	Insensibility	Temperance	Self-indulgence
Giving money	Meanness	Generosity	Prodigality
Large-scale spending	Pettiness	Magnificence	Vulgarity
Honour (great)	Smallness of soul	Greatness of soul (megalopsuchia)	Vanity
Anger	Lack of spirit	Good temper	Irascibility
Truthfulness about oneself	Self-deprecation	Truthfulness	Boastfulness
Amusement	Boorishness	Wit	Buffoonery
Social pleasantness	Quarrelsomeness	Friendliness	Obsequiousness

The mean is not mediocrity: it is “to feel them at the right times, with reference to the right objects, towards the right people, with the right motive, and in the right way” (1106b21). And some actions have no mean — adultery, theft and murder are wrong in themselves.

Choice and responsibility

Book III analyses voluntary action — the first systematic theory of moral responsibility. An act is involuntary if done under force (the wind carries you off) or through ignorance of particular circumstances (you did not know the gun was loaded). Acts done under duress (throwing cargo overboard in a storm) are “mixed”. Choice (prohairesis) is deliberate desire for things within our power, following deliberation about means.

Practical wisdom

Book VI turns to the intellectual virtues. The key one for action is phronēsis — practical wisdom, the ability to perceive what is called for in particular situations and to deliberate well about living well. It cannot be reduced to rules; it is like the perception of the experienced doctor or helmsman. Moral virtue makes the goal right; practical wisdom makes the means right. “It is not possible to be good in the strict sense without practical wisdom, nor practically wise without moral virtue” (1144b31).

Akrasia

Book VII returns to the Socratic puzzle of weakness of will (akrasia): how can someone know the better and do the worse? Aristotle’s answer is subtle — the akratic has knowledge in a way, but under the influence of passion it is like the knowledge of someone asleep, mad or drunk, who can recite verses of Empedocles without understanding them. He thus saves the phenomenon that Socrates denied.

Friendship

Books VIII and IX — a fifth of the Ethics — are about friendship (philia). “Without friends no one would choose to live, though he had all other goods” (1155a5). There are three kinds, based on utility, pleasure and virtue. The first two are accidental and dissolve when the benefit ends. Complete friendship is between good people who love each other for their own sake and wish each other good for the other’s sake; it is rare and takes time — “people cannot know each other until they have eaten salt together”. A friend is “another self” (1166a31). (The saying “a friend is a single soul dwelling in two bodies” is attributed to Aristotle by Diogenes Laertius, not found in his works.)

Contemplation

The Ethics ends (X.7–8) with a surprise. The happiest life is the life of contemplation (theōria) — the activity of the best part of us, intellect, directed to the best objects. It is the most continuous, self-sufficient, leisured and pleasant of activities, and the most divine. “We must not follow those who advise us, being men, to think of human things, and, being mortal, of mortal things, but must, so far as we can, make ourselves immortal” (1177b31). The life of moral virtue is happy “in a secondary degree”.

How this ending fits with the rest of the Ethics — the “inclusive” versus “dominant” end debate — is one of the major questions in Aristotle scholarship.

Politics

The political animal

The Politics begins with the household and the village and ends with the polis, the city-state, which “comes into being for the sake of life, but exists for the sake of the good life” (1252b30). “Man is by nature a political animal” (1253a2) — more so than bees or herd animals, because he alone has speech (logos), which can express not only pleasure and pain but the just and the unjust. “He who is unable to live in society, or has no need because he is sufficient for himself, must be either a beast or a god” (1253a29).

Natural slavery and women

Book I contains the most notorious doctrine in Aristotle: that some people are slaves by nature — capable of perceiving reason but not of deliberating — and that for them slavery is beneficial and just. Aristotle concedes that many actual slaves (war captives) are not natural slaves, which makes much actual slavery unjust by his own lights; but he never questions the institution. He also holds that the female deliberative faculty is “without authority” (1260a13). These doctrines were used for centuries to justify slavery (including in the debates at Valladolid in 1550 over the Indigenous peoples of the Americas), and modern Aristotelians must reckon with them.

Against Plato’s Republic

Book II criticizes Plato’s Republic. Common property breeds neglect: “that which is common to the greatest number has the least care bestowed upon it” (1261b33) — an early statement of the “tragedy of the commons”. Common families would dilute affection into “watery” friendship. Unity can be pushed too far: a city is by nature a plurality.

Constitutions

Aristotle classifies constitutions by who rules (one, few, many) and in whose interest (the common good or the rulers’ own):

	Correct (common good)	Deviant (rulers’ interest)
One	Kingship	Tyranny
Few	Aristocracy	Oligarchy
Many	Polity	Democracy

(In his usage, “democracy” means rule by the poor in their own interest.) The most practicable good constitution is polity, a mixture of oligarchy and democracy, resting on a large middle class — which is most stable because it is neither envious of the rich nor despised by the poor (1295b). He also argues, in the famous “summation” passage (1281b), that the many, each with a little virtue and wisdom, may collectively judge better than a few experts — “as a feast to which many contribute is better than a dinner provided out of a single purse”. This is an ancestor of arguments for democratic deliberation and “the wisdom of crowds”.

A citizen is one who shares in ruling and being ruled in turn (1277b).

Rhetoric and Poetics

Rhetoric

The Rhetoric defines its subject as “the faculty of observing in any given case the available means of persuasion” (1355b26). There are three modes of proof: ethos (the character of the speaker), pathos (the emotions of the audience), and logos (the argument itself). Its analysis of the emotions in Book II — anger, calm, love, hatred, fear, confidence, shame, pity, indignation, envy — is a masterpiece of psychology.

Poetics

The short Poetics (the second book, on comedy, is lost — the premise of Umberto Eco’s novel The Name of the Rose) is the founding text of literary theory.

Imitation is natural. Humans are the most imitative of animals and learn first through imitation; we delight in imitations even of things painful to see, like corpses, because we learn from them.

Tragedy defined.

Tragedy is an imitation of an action that is serious, complete, and of a certain magnitude… through pity and fear effecting the proper purgation (katharsis) of these emotions. (1449b24)

Plot first. Of tragedy’s six parts — plot, character, thought, diction, song, spectacle — plot (muthos) is “the soul of tragedy”. It must have a beginning, middle and end, and its events must follow by necessity or probability.

The best plots turn on reversal (peripeteia) and recognition (anagnōrisis), ideally at once, as in Oedipus the King, where the messenger who comes to free Oedipus from fear reveals who he is.

The tragic hero should be neither wholly good nor wholly bad, but someone like us who falls through some error (hamartia) — a mistake of judgment, not necessarily a moral flaw.

Poetry and history. “Poetry is something more philosophic and of graver import than history, since its statements are of the nature rather of universals, whereas those of history are singulars” (1451b5). The historian says what Alcibiades did; the poet, what such a person would do.

What catharsis means — purgation (medical), purification (religious), or clarification (intellectual) — is a centuries-old controversy. The “three unities” of time, place and action attributed to Aristotle by Renaissance critics are mostly theirs; he insists only on unity of action.

Every discussion of Hamlet’s delay, Lear’s error or Macbeth’s fall still uses his vocabulary.

Further doctrines

Justice and equity

Book V of the Nicomachean Ethics is the first systematic theory of justice. Aristotle distinguishes general justice — lawfulness, virtue as a whole in relation to others — from particular justice, concerned with fair shares. Particular justice takes two forms:

• Distributive justice governs the division of honours, money and other goods among members of a community. It is a geometrical proportion: equals should receive equal shares, unequals unequal ones, in proportion to merit. But what counts as merit is itself contested — “democrats identify it with the status of freeman, supporters of oligarchy with wealth, … supporters of aristocracy with excellence” (1131a27). Most political conflict, Aristotle sees, is a quarrel about the criterion of desert.
• Corrective justice governs transactions — voluntary (sales, loans) and involuntary (theft, assault). It is an arithmetical proportion: the judge restores the equality disturbed by the wrong, regardless of who the parties are. “It makes no difference whether a good man has defrauded a bad man or a bad man a good one” (1132a2). This is the ancestor of the theory of tort and contract.

He adds a discussion of reciprocity in exchange, which leads him to money: since a shoemaker and a builder produce incommensurable goods, money arose as a measure that makes them commensurable, “by convention” — the Greek for money, nomisma, comes from nomos, law or custom.

The most subtle part is on equity (epieikeia). Laws are universal, but some cases cannot be correctly covered by a universal rule. When a case falls outside the law’s intention, equity corrects the law “where it is defective owing to its universality” (1137b26), deciding as the lawgiver himself would have decided had he been present. Equity is like the leaden ruler used by builders on Lesbos, which bends to the shape of the stone. Every modern legal system that distinguishes the letter of the law from its spirit is in his debt.

Pleasure

Aristotle discusses pleasure twice (Book VII and Book X), steering between those who say pleasure is the good (Eudoxus) and those who say it is bad (Speusippus). His view: pleasure is not a process or a filling of a lack, as Plato thought, but something that completes an activity — “as an end which supervenes as the bloom of youth does on those in the flower of their age” (1174b33). Each activity has its own proper pleasure; the pleasure of doing geometry intensifies doing geometry, while a competing pleasure (listening to a flute in the next room) disrupts it. So pleasures differ in kind and value as their activities do, and the pleasures of the good person are the true ones. This analysis anticipates modern psychology of “flow”.

The great-souled man

Few passages in Aristotle have provoked more discomfort than the portrait of the megalopsuchos, the “great-souled” or “magnanimous” man (IV.3). He thinks himself worthy of great things and is worthy of them; he cares above all for honour, but even honour he does not value highly; he is ashamed to receive benefits and glad to confer them; he speaks openly, is ironic toward the many, walks slowly, has a deep voice and level speech, and “possesses beautiful and profitless things rather than profitable and useful ones”. To some readers he is the crown of the virtues; to others (Bertrand Russell, for one) an insufferable aristocrat. Christian writers struggled to reconcile him with humility. He tells us a great deal about the Greek ethics of honour that Friedrich Nietzsche admired.

Household management and the critique of money-making

In Politics I, Aristotle distinguishes household management (oikonomikē, whence “economics”), which acquires the goods needed for living well and has a natural limit, from money-making (chrēmatistikē), the art of acquiring wealth without limit. Exchange to meet needs is natural; accumulation of money for its own sake is not. The most unnatural form is usury: interest is money breeding money, “the birth of money from money” (tokos, “offspring”, is also the Greek for interest), “the most hated sort, and with the greatest reason” (1258b2). This text grounded medieval Christian and Islamic prohibitions of usury, and its distinction between use-value and exchange-value was taken up by Karl Marx.

Leisure, music and education

The last books of the Politics sketch the best constitution, and much of them concern education. The aim of the city is the good life, and the good life requires leisure (scholē — whence “school”), which is not idleness but time for the activities worth doing for their own sake. “We are busy so that we may have leisure, and make war so that we may live in peace” (Ethics 1177b4). Education must therefore train citizens not only for work and war but for the noble use of leisure — above all through music, which shapes character by imitating states of the soul. Different musical modes have different ethical effects: the Phrygian is exciting, the Dorian steady and manly. Education should be public, the same for all citizens, and the concern of the city.

Aristotle and Indian logic

It is worth setting Aristotle’s syllogism beside the five-membered inference (pañcāvayava) of the Indian Nyāya school, systematized in the Nyāya Sūtras (perhaps early centuries CE):

1. Thesis (pratijñā): The hill has fire.
2. Reason (hetu): Because it has smoke.
3. Example (udāharaṇa): Wherever there is smoke, there is fire — as in a kitchen.
4. Application (upanaya): This hill has smoke such as is invariably accompanied by fire.
5. Conclusion (nigamana): Therefore the hill has fire.

The Nyāya form makes explicit the universal “pervasion” (vyāpti) and grounds it in an example, combining deduction with an inductive anchor; it also states the thesis first, as in a debate. Whether there was any historical contact between Greek and Indian logic remains unknown — but the comparison illuminates both: Aristotle abstracts form from content with letters as variables; the Naiyāyikas never cut the link between logic and epistemology.

Puzzles that remain

Aristotle left his heirs a set of problems they are still working on:

• Universals. If forms exist only in things, how can the same form be in many things — and is form individual or universal?
• Teleology. Does nature really act for ends, or only appear to? Can function be explained without purpose?
• The intellect. Is the active intellect personal and mortal, or impersonal and immortal?
• The good life. Is happiness one dominant activity (contemplation) or an inclusive whole of goods (virtue, friends, health, honour)?
• Moral luck. Aristotle says happiness requires external goods — health, wealth, friends, good birth, even good looks — and that the fate of Priam, virtuous but ruined, cannot be called happy. How much of a good life is in our control? (Bernard Williams and Martha Nussbaum revived this question.)
• Slavery and women. Can his ethics be separated from the social hierarchies he took for granted?

Aristotle against Plato

Question	Plato	Aristotle
Where are the forms?	Separate, eternal, in a realm of their own	In things, as their structure and essence
What is most real?	The universal Form	The individual substance
How do we know?	Recollection; reason turned away from the senses	Perception, memory, experience, induction, then insight
The soul	A separate, immortal substance imprisoned in the body	The form of the living body
The good	A transcendent Form of the Good	The human good — flourishing, achieved in action
Politics	Rule by philosopher-kings; common property for guardians	Mixed constitution; private property; rule by law and the middle class
Art	Imitation of imitation; dangerous	Natural, educational, cathartic
Method	Dialectic up to first principles	Survey of opinions, puzzles, observation, then demonstration

The long afterlife

Antiquity

Theophrastus succeeded him and wrote on plants and on characters (Characters, sketches of types like the Flatterer and the Boor, which inspired La Bruyère). The Peripatetic school continued; from the second century CE, commentators such as Alexander of Aphrodisias made Aristotle the object of systematic exegesis. Neoplatonists like Porphyry tried to harmonize him with Plato; Porphyry’s Isagoge, an introduction to the Categories, became a standard textbook for a millennium.

The Arabic world

From the eighth century, in Abbasid Baghdad, translators — many of them Syriac-speaking Christians like Ḥunayn ibn Isḥāq — rendered Aristotle into Arabic. Al-Kindī began Islamic philosophy (falsafa); al-Fārābī was called “the Second Teacher” (after Aristotle, the First); Ibn Sīnā (Avicenna) built a vast new system on Aristotelian foundations; and Ibn Rushd (Averroes) of Córdoba wrote such complete commentaries that the Latins called him simply “the Commentator”. The Jewish philosopher Maimonides made Aristotle the basis of his Guide for the Perplexed.

The Latin West

Boethius translated the logical works in the sixth century; for six hundred years most of the rest was unknown in the Latin West. In the twelfth and thirteenth centuries, through translations from Arabic and Greek in Toledo, Sicily and elsewhere, the whole corpus arrived, provoking a crisis — Aristotle taught that the world is eternal and (on some readings) that the soul is mortal. Church authorities banned his natural philosophy at Paris in 1210. But Albert the Great and his pupil Thomas Aquinas made him the philosophical foundation of Christian theology; by the late thirteenth century he was the core of the university curriculum. The Condemnation of 1277 in Paris listed 219 propositions, many Aristotelian or Averroist, that could not be taught.

The Scientific Revolution

In the sixteenth and seventeenth centuries, Aristotelian physics and cosmology were overthrown. Galileo’s Dialogue (1632) gave the Aristotelian position to a character named Simplicio. René Descartes, Hobbes and Bacon attacked “scholastic” forms and final causes as empty explanations — Molière mocked the doctor who explains opium’s power to induce sleep by its “dormitive virtue” (virtus dormitiva), a jibe Friedrich Nietzsche would later turn against Immanuel Kant.

Revivals

Yet Aristotle kept returning. Franz Brentano’s dissertation on the many senses of being in Aristotle inspired the young Martin Heidegger, whose Being and Time began as a reading of Aristotle. Hannah Arendt’s The Human Condition draws on his distinction between action and production. In ethics, Elizabeth Anscombe’s “Modern Moral Philosophy” (1958) called for a return to virtue; Philippa Foot, Alasdair MacIntyre (After Virtue, 1981), Martha Nussbaum (The Fragility of Goodness, 1986) and Rosalind Hursthouse built virtue ethics into one of the three main approaches to ethics today. The “capabilities approach” of Nussbaum and Amartya Sen is explicitly Aristotelian. In metaphysics, “neo-Aristotelians” have revived essence, powers and hylomorphism.

Key terms

Ousia (substance)

What is most fundamentally real — in the Categories, the individual; in the Metaphysics, form or essence.

Hylomorphism

The doctrine that physical things are compounds of matter (hylē) and form (morphē).

Dunamis / Energeia

Potentiality and actuality — the acorn and the oak.

The four causes

Material, formal, efficient, final — the four kinds of explanation.

Telos

End, purpose, that for the sake of which.

Using Aristotle in conversation

• On habits: “We become just by doing just acts.” Character is built by practice, not by resolution.
• On moderation that isn’t mediocrity: courage is the mean between cowardice and rashness — feel the right thing, at the right time, toward the right people, in the right way.
• On precision: demand only as much precision as the subject allows — ethics is not mathematics.
• On friendship: distinguish friends of utility, of pleasure, and of virtue — and notice how few of the third you have.