Justified True Belief

(●) The student of Plato and tutor of Alexander, who invented formal logic, founded the study of living things, and reasoned from a moving world to an unmoved God. + When Dante, the medieval Italian poet, walks through the first circle of his Inferno, past the great pagans who lived before Christ, he sees one figure seated in the middle of the philosophic family with every one of them looking toward him, and he does not bother with the name. He calls him "the master of those who know." Thomas Aquinas, the thirteenth-century theologian, was even more economical: in thousands of citations he wrote simply "the Philosopher," and every reader in Europe knew who was meant. For roughly fifteen hundred years, in Christian, Muslim, and Jewish schools alike, to study logic, or nature, or the soul, was to study Aristotle. He earned it by range. No one before him, and arguably no one since, wrote seriously on so much: how valid reasoning works, what causes are, why things fall, how weather forms, how a chick grows inside its egg, what the soul is, what makes a person good, how cities should be governed, what makes a speech persuasive and a tragedy move an audience. Where his teacher Plato looked up from the world toward eternal Forms, the perfect patterns Plato believed lay behind everything we see, Aristotle bent down and looked at the world, and then reasoned upward from it. That is why he matters for Christian readers. He built the tools. The syllogism, the two-premises-and-a-conclusion form that deductive arguments for God still run on; the language of cause and effect; the pair of words act and potency, for what a thing is and what it could become; the idea of a first mover that nothing moves: all of these were his, and the greatest Christian theologians of the Middle Ages took them up and argued with them. He also shows where reason unaided stops. His God is real, eternal, and alive, and does not know that we exist. The church kept him close for both reasons. One fact worth carrying away: everything of his that we read, he never published. His polished books, the ones the Roman orator Cicero praised as "a golden stream of eloquence," are lost but for fragments. What survives are the working texts of his school, dense, unadorned, sometimes stitched together by later hands: about thirty works out of some two hundred titles the ancient lists give him. Reading Aristotle is less like reading a book than like sitting in on a course.

(●) 384 BC: Born in Stagira, a small Greek town near the Macedonian frontier, the son of a king’s physician. + Aristotle was born in 384 BC in Stagira, a Greek colony on the Chalcidice peninsula in the far north, a long way from Athens in miles and further in reputation. Athenians thought of Macedon, the kingdom next door, as half barbarian. His father Nicomachus was court physician to King Amyntas III of Macedon, the grandfather of Alexander the Great, and the family belonged to the Asclepiads, the old guild of physicians who traced their line to Asclepius, the god of healing. His mother Phaestis came from Chalcis on the island of Euboea, where the family kept property that would matter at the very end of his life. It is tempting, and probably right, to see the physician’s house in everything he later did. A doctor’s son learns early that you find things out by looking: at a wound, at a fever, at what happened to the last patient who had this. Plato reasoned from first principles; Aristotle, all his life, began with what could be seen and handled, and his biological works read like a physician’s case notes on the whole animal kingdom. Both parents died while he was still a boy. A family friend, Proxenus of Atarneus, took him in and raised him, and Aristotle never forgot it. Decades later he adopted Proxenus’ son Nicanor, and in his will he made Nicanor guardian of his children and asked that a statue be raised to Proxenus. He had been a foreigner’s ward and a northerner, and in Athens he would be a foreigner all his life: a resident alien, in Greek a metic, who could never own land or vote in the city where he did his greatest work.

(●) 367 BC: At seventeen he entered Plato’s Academy and stayed twenty years, as pupil, then colleague, then critic. + In 367 BC, at seventeen, Aristotle came south to Athens and joined the Academy, the school Plato had founded in a grove outside the walls twenty years earlier. One tradition says Plato was away in Sicily when the boy arrived, on his second and failed attempt to make a philosopher of a tyrant, so that Aristotle’s first months were spent under the astronomer Eudoxus. When Plato returned, the two most powerful minds of the ancient world were in the same building, and they stayed there together for two decades. Later biographers preserved two nicknames Plato is said to have given him, and neither can be verified, but both ring true. He called him "the Mind" of the school, and "the Reader," because Aristotle read. That sounds like a small thing until you remember that in a world where books were hand-copied scrolls, philosophy was done by talking, and a young man who built up a private library and studied texts alone was doing something new. He also wrote in these years, dialogues in Plato’s own manner that the ancient world admired; not one of them survives except in fragments quoted by later writers. Somewhere in those twenty years the pupil became a colleague, a grown man teaching and writing under the same roof as the man who had trained him. He did not stay a disciple. The core of Plato’s teaching was that the things we see are copies of perfect Forms existing on their own, somewhere beyond the world of change: there is a Form of "horse," and every horse in every field is a rough copy of it. Aristotle came to think that explained nothing. A Form of "horse" floating apart from every horse does not help you understand a single horse; whatever makes a horse a horse is in the horse. He said so in writing, and he knew what it cost him. Setting out to criticize the Forms in his Ethics, he wrote that "while both are dear, piety requires us to honour truth above our friends." The popular version, "Plato is dear to me, but truth is dearer still," is a later paraphrase of that line. The affection in it is real: he never stopped calling the Forms the doctrine of "our friends."

(●) 347 BC: Plato died, and Aristotle left Athens for the coast of Asia Minor, where he married and began to study living things. + Plato died in 347 BC and his nephew Speusippus was chosen to lead the Academy. Aristotle left the city the same year. Was he passed over and hurt? Or did he simply leave because Athens had become an unsafe place for anyone connected with Macedon? Philip of Macedon had razed Stagira itself in 349 BC and destroyed the nearby city of Olynthus in 348 BC, and Athens had not forgotten it. We simply don’t know. Probably both were true. He crossed the Aegean to Assos, a hillside town on the coast of Asia Minor, the great peninsula that is Turkey today, at the invitation of its ruler Hermias of Atarneus. Hermias is one of the strangest figures in the story: a former slave, according to the ancient accounts, who had studied at the Academy and now governed a small territory of his own. He gave the philosophers a home. Aristotle married Pythias, Hermias’ niece and adopted daughter, and they had a daughter, also named Pythias. Around 345 BC he moved across the water to Mytilene on the island of Lesbos, where he met Theophrastus, a native of the island who became his closest colleague for the rest of his life. On Lesbos, in the shallow lagoon at Pyrrha, Aristotle did something no philosopher had done before. He watched. He talked to fishermen, opened up animals, and wrote down what he found: the catfish that guards its eggs, the dogfish whose unborn young are attached to the mother by a cord like a mammal’s, the octopus’s specialized mating arm. Naturalists disbelieved several of these reports until the nineteenth century confirmed them. Darwin, reading a new translation of the Parts of Animals two months before he died, wrote to the translator that Linnaeus and Cuvier, the two great naturalists of the generations before his own, had been his two gods, "but they were mere school-boys to old Aristotle." The interlude ended in horror. Around 341 BC Hermias was betrayed to the Persians, carried to their emperor (the Greeks called him simply the Great King), tortured to reveal what he knew of Philip’s plans, and executed; his last message, the story goes, was that he had done nothing unworthy of philosophy. Aristotle wrote a hymn to Virtue in his memory and set up a memorial at Delphi. That poem would be used against him eighteen years later.

(●) 343 BC: Philip of Macedon hired him to teach a thirteen-year-old prince named Alexander. + In 343 BC King Philip II, the son of the king Aristotle’s father had served, summoned him to Macedon to educate his heir. Alexander was thirteen. Plutarch, the Greek biographer who wrote a life of Alexander, says the lessons were held at Mieza, in a sanctuary of the Nymphs with stone benches and shaded walks that were still pointed out to visitors four hundred years later. The prince was taught Homer above all; he kept a copy of the Iliad edited by Aristotle, and on campaign he slept with it under his pillow beside his dagger. Philip paid the teacher in an unusual coin. He rebuilt Stagira, which he himself had razed, and brought its scattered citizens home. The lessons lasted perhaps three years. In 340 BC Alexander, sixteen, was left as regent while his father went to war, and the schooling was over. What did the teacher make of the pupil? Aristotle’s Politics holds that human beings flourish in a city small enough that the citizens know one another, and it takes a dim view of Persians. His student conquered Persia, married a Persian princess, and asked the Greeks to worship him. The two men drifted apart, and something worse than drift came in 327 BC, when Alexander had the expedition’s historian Callisthenes, a young relative of Aristotle’s, arrested for a supposed conspiracy. He died in custody, and the ancient accounts disagree over whether he was hanged or sickened in chains. When Alexander died in Babylon a rumor spread that the old tutor had supplied the poison. Plutarch passes the rumor on and adds that most writers think the whole poisoning story a fabrication, and no historian believes it. There is a lesson in the failure, and Aristotle would have been the first to draw it. He taught that virtue is formed by habit and that a good upbringing is the foundation of a good life, and his most famous pupil became the ancient world’s standing proof that a great teacher is not enough.

(●) 335 BC: Back in Athens at fifty, he founded the Lyceum and spent twelve years teaching, collecting, and writing the works we have. + With Alexander secure on the throne and Greece quiet under Macedonian control, Aristotle returned to Athens in 335 BC, now about fifty years old. As a resident alien he could not buy property, so he set up in a public gymnasium east of the city, in a grove sacred to Apollo Lyceios, and the school took the name of the place: the Lyceum. Its covered walkway, in Greek a peripatos, gave his followers their name too. They were the Peripatetics, and the tradition that the master lectured while strolling up and down comes from the same word. The Lyceum was something new: not only a school but a research institute. Aristotle built up a library of his own, and the geographer Strabo says he was the first man he knew of to collect books, and that the kings of Egypt learned from him how to arrange one. He and his students collected the constitutions of 158 Greek cities, catalogued the winners of the Pythian games (Delphi’s answer to the Olympics), gathered maps, and dissected animals. Of those 158 constitutions exactly one, the constitution of Athens, survives in more than fragments; it turned up on a papyrus in the Egyptian sand and was published in 1891. A later story says he taught the hard subjects to his students in the morning and gave public lectures in the afternoon. His Metaphysics opens with the sentence that could stand over the whole enterprise: "All men by nature desire to know." These twelve years produced, or finished, most of the works we read: the logic, the Physics, the Metaphysics, the treatise on the soul, the Ethics and Politics, the books on animals. They are not books in our sense. They are lecture texts, written for people who were going to hear them explained, which is why they are so compressed and why they sometimes argue with themselves. The private life went on beneath the work. Pythias died in these years, and Aristotle lived afterward with a woman from Stagira named Herpyllis, who bore him a son, Nicomachus, the name the Nicomachean Ethics carries.

(●) 323 BC: Alexander died, Athens turned on the Macedonians, and Aristotle left rather than let the city "sin twice against philosophy"; he died the next year at Chalcis. + In June of 323 BC Alexander died of a fever in Babylon at thirty-two, and Athens rose against Macedon within weeks. Aristotle had been the friend of Macedonian kings his whole life, and he was an obvious target. A priest named Eurymedon brought a charge of impiety against him, or a man named Demophilus did, depending on which ancient source you follow, and it was the same charge that had killed Socrates seventy-six years before. The pretext was the old hymn for Hermias, which the prosecution read as worshiping a mortal man as a god. A tradition recorded by the writer Aelian says Aristotle left with a remark that Athenians have never quite forgiven: he would not let the city sin twice against philosophy. He withdrew to Chalcis on Euboea, to his mother’s family property, and died there in 322 BC at about sixty-two. Diogenes Laertius, the ancient compiler of philosophers’ lives, following the chronicler Apollodorus, says the death was a natural one; a lone later writer claimed he drank poison, and nobody credits it. His will survives, copied out by the same Diogenes, and it is the most human document we have from him. He asks that the bones of his wife Pythias be laid beside him, as she had wished. He tells his executors to care for Herpyllis "in memory of me and of the steady affection which Herpyllis has borne towards me," with money, servants, and a house at Chalcis or Stagira, whichever she prefers. He arranges his daughter’s marriage to Nicanor. He frees several of his slaves by name, and orders that none of those who waited on him be sold. Theophrastus, his partner of more than twenty years, took over the Lyceum. The books nearly did not survive him. Theophrastus left the library to a pupil, Neleus, whose heirs (so Strabo and Plutarch tell it) hid the manuscripts in a cellar at Scepsis to keep them from the book-collecting kings of Pergamon, where damp and moths got at them. They were bought by a collector, seized by the Roman general Sulla when he sacked Athens in 86 BC, carried to Rome, and finally edited and arranged by Andronicus of Rhodes in the first century BC. Modern scholars think the story is overdramatic (other copies circulated), but Andronicus’ arrangement is the Aristotle we still read, and it is the reason the words metaphysics and organon exist at all: both are names his editors gave to groups of his manuscripts, not titles he chose.

What He Taught

(T1) Sound reasoning has a shape, and the shape can be written down and checked. + A mother hears that every child who ate the potato salad at the picnic got sick, and then hears that her son ate the potato salad. She does not need anyone to tell her the third thing. It is already there, and it is there with a kind of force: given the first two, the third cannot fail. Aristotle is the first person we know of who stopped and asked what that force is, and who noticed that it has nothing to do with potato salad. It comes from the shape of the statements. "All B are C; this A is a B; so this A is a C" will deliver its conclusion whatever you put in for A, B, and C. He called such an argument a syllogism, a piece of reasoning in which, certain things being laid down, something else follows from them by necessity. Two premises, one conclusion. He was also the first to use letters as placeholders, which is why that skeleton reads like algebra: variables in logic are his invention. In the Prior Analytics he worked through every possible arrangement of two premises and sorted the ones that guarantee their conclusion from the ones that merely look as if they do, and in the Sophistical Refutations he catalogued the ways an argument can go wrong while sounding right: using a word in two senses, assuming what you set out to prove, and a dozen more. The six logical works together were later named the Organon, the "tool," because logic is the instrument every other science picks up. Two distinctions from these books have never stopped being useful. The first is the difference between a valid argument and a true one. An argument can be perfectly built and still have a false premise: "all birds fly; penguins are birds; so penguins fly" is valid and wrong, and the fault lies in the first line, not in the reasoning. The second is the difference between deduction and induction. A syllogism moves from a general rule to a particular case with certainty, while the move in the other direction, from many observed cases to a general rule, gives only probability. He was clear-eyed about both, and he never confused them. When a modern apologist writes "whatever begins to exist has a cause; the universe began to exist; therefore the universe has a cause," he is writing in a form Aristotle invented. And the form held. The German philosopher Kant remarked in 1787 that logic had not been able to advance a single step since Aristotle and looked "to all appearance a closed and completed body of doctrine." That was overstated, since the Stoics (the rival school of the generation after him) and the medieval logicians had already gone past him at points, but the deep change waited for two mathematicians, George Boole in the 1850s and Gottlob Frege in 1879, more than two thousand years after the Prior Analytics.

(Q) "A syllogism is discourse in which, certain things being stated, something other than what is stated follows of necessity from their being so." + Source: Aristotle, Prior Analytics I.1, 24b18–20 (Jenkinson translation, Oxford, 1928). The definition that opens formal logic. The whole weight sits on the words "of necessity": the conclusion of a valid argument is not likely, or reasonable, or usually so; given the premises, it cannot be otherwise. The reference numbers used for every Aristotle citation are called Bekker numbers, after the 1831 Berlin edition whose page, column (a or b), and line every scholar still cites. "24b18" means page 24, right-hand column, line 18, so a quotation can be found in any edition or translation in the world.

(T2) Nature does nothing in vain: every natural thing acts for an end. + Ask a child why the kitchen table exists and you can give four different true answers. Because it is made of oak. Because it has a flat top and four legs, which is what makes it a table rather than a pile of oak. Because a carpenter built it. Because a family needed somewhere to eat. Aristotle, in the second book of the Physics, said that a full explanation of anything answers all four, and he named them the material, formal, efficient, and final causes: what a thing is made of, what makes it the kind of thing it is, what brought it about, and what it is for. His own example was a bronze statue rather than a table, but the point is the same, and the fourth answer is the one he cared about most. The startling claim is that the fourth answer applies to nature as much as to carpentry. The eye is for seeing; teeth are shaped for cutting and grinding; the swallow builds its nest for its young; roots grow down and not up because the food is down there. Nobody planned any of that, and yet it is not chance. Aristotle knew the alternative, because an earlier thinker, Empedocles, had proposed something like natural selection: perhaps teeth simply came out sharp by accident, and the creatures whose accidents happened to be useful survived. Aristotle’s reply was that chance does not produce regularity. Luck explains the one-off, and things that happen always or nearly always, like teeth coming in sharp in every generation, need a different kind of cause. Hence his refrain, repeated across half a dozen works: nature does nothing in vain. Underneath this lies the pair of terms that did more work in later theology than any others he coined. An acorn is not an oak, but it is not nothing in relation to an oak either: it is an oak in potentiality, and the grown tree is that same oak in actuality. Every change in the world, he argued, is the actualizing of a potential that was already there: cold coffee is potentially hot, a block of marble is potentially a statue, a child is potentially a reader. This let him answer two earlier thinkers at once. Parmenides had argued that change is an illusion, and Heraclitus that everything is in flux and nothing holds still. Change is real, Aristotle said, and it can be understood, because it always runs from a potency to its act. Christian thinkers found here a philosophy that took the order of the world seriously without making the world divine, and they made two things of it. The fifth of Aquinas’ five ways, the five short proofs of God’s existence that open his Summa Theologiae, argues that things without minds, like the swallow, act for ends only if directed by something with a mind, "as the arrow is shot to its mark by the archer." And the whole idea of natural law, that the good of a thing is the fulfillment of its nature, is the final cause carried into ethics. Aristotle himself stopped short. His ends are built into things; no archer aims them. The church supplied the archer. Honesty requires adding that his physics, as opposed to his biology, was mostly wrong. He held that heavier bodies fall faster, that the heavens are made of a fifth element that never changes, and that the earth sits at the center of everything, and when these opinions became dogma in the universities they held science back. His teleology fared far better. The word is a later coinage from the Greek telos, an end or goal, and it means explanation by what a thing is for, the fourth of the four causes. In his study of living things it was the part that lasted, and the same Darwin whose theory finally replaced it could not stop admiring the observer.

(Q) "If then it is both by nature and for an end that the swallow makes its nest and the spider its web, and plants grow leaves for the sake of the fruit and send their roots down (not up) for the sake of nourishment, it is plain that this kind of cause is operative in things which come to be and are by nature." + Source: Aristotle, Physics II.8, 199a26–30 (Hardie and Gaye translation, Oxford, 1930). The argument that purpose is at work in nature, made not from an abstract principle but from a swallow, a spider, and a root. The contrast inside the parenthesis is Aristotle’s own, down and not up: the root does not merely grow, it grows in the direction that serves the plant.

(T3) Behind all the motion in the world stands one unmoved mover, which he called God. + A man pushes a stone with a stick. The stone moves only while the stick moves it, and the stick moves only while the hand moves it. That is Aristotle’s own example, from the eighth book of the Physics, and the question he asks about it is simple. Suppose the series of "moved by" never reached anything that moves without being moved. A train of boxcars, however long, does not roll unless somewhere there is an engine, and adding boxcars to infinity does not help. So there must be a first mover, and since motion never began (Aristotle thought the world eternal) the first mover is not first in time, the way a starting pistol is first, but first in dependence, right now, the way the engine is first while the train is moving. What must such a mover be like? Recall the acorn (T2). Anything that changes goes from potency to act, and only what is already actual can bring that about: cold coffee does not heat itself. A mover that nothing moves therefore has no unrealized potential in it at all. It is pure actuality, and everything else follows from that. It is eternal, because coming to be and passing away are changes, and it cannot change. It is immaterial, because matter is exactly the stuff that can become something else. It is one, and it is unchanging. In the twelfth book of the Metaphysics Aristotle says what it does. It thinks, because thought is the highest activity, and it thinks the highest object, which is itself: "its thinking is a thinking on thinking." Its life is the life we taste in our best moments of understanding and can hold only for a short time. And it moves the heavens not by pushing but by being desired, the way a beloved moves a lover across a room without lifting a finger: it "produces motion as being loved." This is the passage where a pagan, reasoning from nothing but motion, arrives at a living God, and Christians from the twelfth century on read it with something like awe. The first of Aquinas’ five ways is this argument almost line for line, and the second (from causes) and third (from necessary being) are built from the same materials. It also has to be read honestly, because the God it reaches is strange. In the same book Aristotle, trying to account for all the separate motions of the planets, multiplies the unmoved movers to forty-seven or fifty-five. His first mover does not know the world exists: for the perfect mind to think of anything less than itself would be a step down. It did not make the world and does not govern it. It cannot be prayed to, because it could not hear. Aristotle had proved that there is a God, and left him without a single thought for us.

(Q) "We say therefore that God is a living being, eternal, most good, so that life and duration continuous and eternal belong to God; for this is God." + Source: Aristotle, Metaphysics XII.7, 1072b28–30 (Ross translation, Oxford, 1908). The sentence in which the unmoved mover receives its name. Aristotle has just argued that the activity of thought is life itself, and that the first mover’s self-sufficient thinking is the best and most enduring life there is. Medieval readers noticed how close "living, eternal, most good" stands to the language of the Psalms, and how far the rest of the chapter stands from it.

(T4) The soul is the form of the living body, not a ghost imprisoned in it. + Press a seal into warm wax and you get a shape. Now try to answer the question "are the wax and the shape one thing or two?" It is not a hard question; it is a bad one. The shape is not a second object sitting inside the wax, and it is not the wax either. It is the wax formed. That, said Aristotle in On the Soul, is what the soul is to the body. Take an eye: sight is what an eye is for, and an eye that cannot see is an eye only in the way a painted eye is. The soul is to the whole living body what sight is to the eye, the set of capacities that make this body a living body rather than a corpse. His technical definition, "the first grade of actuality of a natural body having life potentially in it," says exactly that in the vocabulary of act and potency (T2). Later philosophers named this view hylomorphism, from the Greek for matter (hyle) and form (morphe): a living thing is one substance, matter and form together, not two things bolted together. It is the opposite of Plato’s picture, in which the soul is a prisoner doing time in the body and longing to get out. On Aristotle’s view the soul does not want out, because a soul without a body is like sight without an eye. Souls come in grades: plants have the powers of nourishment and growth, animals add sensation and movement, and human beings add reason. The same book teaches that knowledge begins in the senses. The mind at birth is like a writing tablet with nothing yet written on it, and universals (the idea of "horse" that fits every horse) are reached by seeing many horses, remembering them, and letting experience settle into understanding. Plato had said the soul remembers truths it knew before birth. Aristotle said it learns them, from the world, through the body it lives in. Then comes the passage that started two thousand years of argument. In fifteen lines of the third book he distinguishes a mind that receives from a mind that makes, and says of the second that "this alone is immortal and eternal." Does that mean a person survives death? His commentators split three ways. Alexander of Aphrodisias, the most authoritative of his ancient commentators, said no. The Muslim philosopher Averroes said there is one immortal intellect shared by all mankind, and no individual survival. Thomas Aquinas argued that each person’s soul survives because understanding is not the act of any bodily organ. Even Aquinas, though, admitted the limit. Commenting on Paul’s chapter on the resurrection (1 Corinthians 15), he wrote that "my soul is not I," and that if only souls are saved, no man is saved. A soul waiting for its body is exactly what Aristotle’s philosophy would lead you to expect, and it is why Christian thinkers found in him, more than in Plato, a friend to the doctrine that the body will rise.

(Q) "That is why we can wholly dismiss as unnecessary the question whether the soul and the body are one: it is as meaningless as to ask whether the wax and the shape given to it by the stamp are one, or generally the matter of a thing and that of which it is the matter." + Source: Aristotle, On the Soul II.1, 412b6–9 (J. A. Smith translation, Oxford, 1931). Aristotle has just given his definition of the soul, and here he draws the consequence: soul and body are not two things that need joining, any more than a shape needs joining to the wax it is the shape of.

(T5) The happy life is a whole life of activity in accordance with virtue. + Nobody becomes a pianist by reading about pianos. You become one by playing, badly, and then a little less badly, until one day your hands know things your head could not have told them. Aristotle thought goodness works the same way. "We become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts," he wrote in the Nicomachean Ethics, and the word he used for the result was hexis, a settled disposition, a habit in the deepest sense: not something you have to think about but something you have become. A virtue is a good habit of that kind; a vice is a bad one. The book opens by asking what all human activity is finally for, and answers with the word eudaimonia. It is usually translated "happiness," but it does not mean a feeling. It means a life going well, flourishing, the way a tree flourishes when it has the soil and light its nature calls for. And what does a human nature call for? Aristotle’s answer runs through what a human is for. A knife is for cutting, and a good knife cuts well; a human being is the animal that reasons, and a good human life is rational activity done well, over a whole lifetime. One swallow, he says, does not make a summer, and one good day does not make a happy man. His best-known tool is the doctrine of the mean. Courage lies between cowardice and recklessness, generosity between stinginess and waste, good temper between spinelessness and rage. This is not a counsel of moderation, as if the virtuous person felt everything by halves. It is a bullseye: the right amount, at the right time, toward the right people, for the right reason. Hitting it takes practical wisdom, phronesis, the trained judgment of an experienced person who can see what this situation needs, and Aristotle thought no rulebook could replace it. Since such training needs good laws and a good upbringing, and since "man is by nature a political animal," the Ethics runs straight into the Politics: the city exists so that people can live not merely together but well. Christian moral thought took nearly all of this up. Aquinas’ long treatment of habits and virtues in the Summa is Aristotle’s ethics received and corrected, with the four cardinal virtues (prudence, justice, courage, temperance) kept, and three theological virtues (faith, hope, love) set above them, which no amount of practice can produce because they are given by grace. In the twentieth century the philosophers Elizabeth Anscombe and Alasdair MacIntyre revived his approach against ethics built on rules alone, and C. S. Lewis, in The Abolition of Man, cited him for the claim that the aim of education is to make the pupil like and dislike what he ought. The gospel parts from him on the substance of virtue as well, and sharply (†).

(Q) "Human good turns out to be activity of soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete. But we must add ‘in a complete life.’ For one swallow does not make a summer, nor does one day; and so too one day, or a short time, does not make a man blessed and happy." + Source: Aristotle, Nicomachean Ethics I.7, 1098a16–20 (Ross translation, Oxford, 1925). The conclusion of the argument from what a human being is for. Happiness is an activity, not a possession or a mood, and it is measured over a lifetime rather than an afternoon.

(Q) "But 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, and strain every nerve to live in accordance with the best thing in us." + Source: Aristotle, Nicomachean Ethics X.7, 1177b31–34 (Ross translation, Oxford, 1925). The last book of the Ethics argues that the highest human life is the life of understanding, because it is the activity most like God’s (T3). Christian readers heard in it an echo of Plato’s counsel to become like God so far as a human can, and of Paul’s "set your minds on things that are above" (Colossians 3:2). They also noticed the qualifier "so far as we can," and that Aristotle’s God does nothing to close the remaining distance from the other side.

What Christian Thinkers Made of Him

(†) For its first thousand years the church knew him mainly as a logician, and distrusted even that. + The early Christians inherited Plato as a friend and Aristotle as a suspect. Tertullian, the fierce North African church writer, groaned around AD 200 over the heretics who had learned their trade from him: "Unhappy Aristotle! who invented for these men dialectics, the art of building up and pulling down." In the fourth century the Arian teachers Aetius and Eunomius, who argued that the Son was a creature rather than God, were accused by their orthodox opponents of reasoning out of Aristotle’s Categories rather than out of Scripture. The worry was not foolish. A method for winning arguments is a dangerous thing in the wrong hands. And yet the church could not do without him. Around AD 510 the Roman statesman Boethius, a Christian, set out to translate all of Aristotle and all of Plato into Latin and show that they agreed. He was executed around AD 524, long before the project was done. He had translated more of the logic than the schools managed to keep; only two short works stayed in circulation, the Categories and On Interpretation, and they were nearly all the Aristotle the Latin West possessed for the next six hundred years. Every monk who learned to argue learned to argue from them. In the Greek East, John of Damascus opened his great summary of the faith in the eighth century with a primer of Aristotelian logic, borrowing the terms substance, nature, and person to say precisely what the church meant by one God in three persons and one Christ in two natures. The rest of Aristotle came home to Christendom by the strangest of roads. His works passed from Greek into Syriac (the language of the eastern churches) and Arabic, and for three centuries it was Muslim philosophers, al-Farabi, Avicenna, and above all Averroes, whom the Latin scholars simply called "the Commentator," who kept him alive and thought hardest about him, along with the Jewish philosopher Maimonides. When the Latin West wanted Aristotle back, it had to learn him first from Toledo, the Spanish city where the translators worked, and from the mosque and the synagogue.

(†) Thomas Aquinas called him simply "the Philosopher" and built the Five Ways on his foundations. + In the twelfth century, translators in Toledo and Venice began turning the whole corpus into Latin, and Aristotle hit the new universities like weather. Paris panicked. In 1210 lecturing on his natural philosophy (the Physics and the books on nature) was banned on pain of excommunication; the ban was repeated in 1215, softened by Pope Gregory IX in 1231 to hold only until the books "shall have been examined and purged from all suspicion of errors," and by 1255 the same faculty required every one of his known works for the degree. Forty-five years from forbidden to compulsory. The man who made the peace was a Dominican friar. Thomas Aquinas, taught by Albert the Great, wrote line-by-line commentaries on a dozen of Aristotle’s works, using fresh translations made straight from the Greek for him by his fellow Dominican William of Moerbeke. In the Summa Theologiae, his great summary of Christian theology, he cites "the Philosopher" on nearly every page, and the five ways of proving God’s existence at its opening run on Aristotle’s rails: the first from motion and the unmoved mover (T3), the second from causes, the fifth from the purposes at work in mindless nature (T2). His account of the human being as one substance of soul and body is Aristotle’s (T4), and a Western church council at Vienne in 1312 wrote that definition of the soul into its decrees. His treatise on virtue is Aristotle’s ethics with grace poured in on top (T5). But Aquinas was never a disciple. Philosophy, he said, is theology’s handmaid, and he corrected the master wherever Scripture required: creation from nothing, God’s knowledge of and care for every creature, the survival of the individual soul, the resurrection, grace. Even so, the church stayed nervous. In 1277, three years after Aquinas died, the bishop of Paris condemned 219 propositions being taught in the arts faculty, some of them close to Thomas’ own. Dante, a generation later, settled the matter for the imagination of Europe when he placed Aristotle at the center of the noble pagans in Limbo, the outer edge of his Hell where the virtuous who never knew Christ live without torment and without hope, "the master of those who know."

(†) The Reformers and the new scientists both threw him out, and he came back anyway. + Martin Luther could not stand him. In the disputation he posted in 1517, a set of theses put up for academic debate a few weeks before the more famous ninety-five, he wrote that "virtually the entire Ethics of Aristotle is the worst enemy of grace" and that "the whole Aristotle is to theology as darkness is to light." Three years later he advised the German nobility to throw the Physics, Metaphysics, On the Soul, and Ethics out of the universities altogether. The objection was not to logic. It was to a picture of goodness as something a person builds by practice (T5), which to Luther looked like the doctrine of self-made righteousness that had nearly destroyed him. Yet within twenty years his own colleague Philip Melanchthon had put Aristotle’s logic, rhetoric, ethics, and physics back into the curriculum at Wittenberg, and the Protestant theologians of the next century, Reformed and Lutheran alike, reasoned in his categories as fluently as any Dominican. The scientists were the more lasting rebellion. Francis Bacon called his 1620 manifesto for the new science the Novum Organum, the "new tool," a title aimed squarely at Aristotle’s old one, and Galileo made the Aristotelian professors into comic characters. They were right about the physics. The five elements, the crystalline heavens, the earth at rest at the center: all of it fell, and it deserved to. What did not fall was the rest. In 1879 Pope Leo XIII made Aquinas, and with him Aristotle, the standard of Catholic philosophy again. In 1958 the philosopher Elizabeth Anscombe argued that modern moral philosophy had lost its way and should go back to Aristotle’s questions about virtue, and in 1981 Alasdair MacIntyre’s After Virtue put the choice of the age as "Nietzsche or Aristotle" (Nietzsche being the nineteenth-century philosopher who had pronounced the old morality dead) and chose Aristotle. Contemporary Christian philosophers still run cosmological arguments in the vocabulary of act and potency, and the argument from motion is, in its modern dress, a live option again. Thrown out twice, he kept walking back through the door.

(†) Where the gospel parts company with him: a God who creates, knows, and loves; the resurrection; humility; and grace. + The church kept Aristotle as a servant, and it had to correct him at six points, every one of them serious. - Creation. Aristotle held that the world has always existed and that God is its final cause, the goal it moves toward, not its maker. Scripture opens with a beginning and a Maker (Genesis 1:1; John 1:3; Hebrews 11:3). Medieval Christians argued among themselves about whether reason alone could prove a beginning (the Franciscan Bonaventure said yes, Aquinas said no), but none doubted that revelation taught it, and the Kalam argument for a beginning of the universe (kalam is the Arabic word for the theology of the medieval Muslim schools) was sharpened by Muslim theologians precisely against Aristotle’s followers. - Providence. His unmoved mover thinks only of itself (T3). The God of Scripture counts the hairs of your head and marks the fall of a sparrow (Matthew 10:29–30), and "God is love" (1 John 4:8) is a sentence Aristotle could not have written about his first mover. - The person after death. At most his philosophy leaves an impersonal intellect that survives, and no resurrection at all. The gospel promises the raising of the body and of the person: "if Christ has not been raised, your faith is futile" (1 Corinthians 15:17); "I am the resurrection and the life" (John 11:25). - Pride and humility. His portrait of the best man, the "great-souled" man of the Ethics, is someone who deserves great honors and knows it, who is ashamed to receive a favor and quick to confer one, and who walks slowly and speaks in a deep voice. Humility is not on Aristotle’s list of virtues; love of enemies is not on it either. The gospel begins with "Blessed are the poor in spirit" (Matthew 5:3), shows the Lord of glory washing feet (John 13:14), and commands love for enemies (Matthew 5:44) and the mind of Christ, who "emptied himself" (Philippians 2:5–8). - Who counts. The Politics teaches that some people are slaves by nature and that the female is inferior to the male, and the good life it describes is for leisured male citizens. Scripture says every human being bears the image of God (Genesis 1:27), that in Christ "there is neither Jew nor Greek, there is neither slave nor free" (Galatians 3:28), and it sends a runaway slave home to his master as "a beloved brother" (Philemon 16). - Grace. For Aristotle virtue is achieved: practice makes the good person, and the person who fails had the wrong training or the wrong luck. Paul describes a man who knows the good and cannot do it (Romans 7:18–19), and the cure is not more practice but a gift: "by grace you have been saved through faith. And this is not your own doing" (Ephesians 2:8–9), and a goodness the Spirit grows (Galatians 5:22–23). Aristotle got the shape of reasoning right, and the shape of nature nearly right, and the shape of God wrong in exactly the ways that only a God who speaks could correct. The church kept him because a servant that good is worth correcting, and because he showed, more plainly than anyone before Christ, how far a first-rate mind can climb by looking hard at the world, and where it must stop.