Aristotle

Key ideas

1. Syllogistic logic. A syllogism is an argument in which, certain things being laid down, something else follows of necessity from them. In the Prior Analytics Aristotle works out which forms are valid, and in the Posterior Analytics he describes science as demonstration from first principles that are themselves reached through experience and induction.
2. Substance and the categories. Aristotle sorts what can be said of anything into ten categories: substance, quality, quantity, relation, place, time, position, having, acting and being affected. Individual things, this person or this horse, are primary substances, and everything else exists only as a feature of them.
3. Matter. An ordinary thing is a composite of matter and form, and its form is what makes its matter that kind of thing. A full explanation names four causes: the material (what it is made of), the formal (what it is), the efficient (what brought it about) and the final (what it is for).
4. Potentiality and actuality. Aristotle treats change as the realising of a potentiality, and holds that what is actual is prior to what is potential. He argues that the chain of change must end in an unmoved mover: pure activity, whose activity is thinking, which moves the heavens as an object of desire and thought.
5. The soul as the form of the body. In On the Soul, the soul is not a thing lodged in the body but the form of a living body: its capacity for the functions of life, from nutrition and perception to reasoning. How far the intellect, which he distinguishes into receptive and productive, is separable from the body is disputed.
6. Eudaimonia and the mean. The human good is eudaimonia, flourishing: activity of the soul in accordance with virtue over a complete life. Virtue is a settled disposition, formed by habit, to feel and act at the mean between excess and deficiency, as judged by practical wisdom.
7. The political animal. Humans are by nature political animals, and the city comes into being for the sake of life but exists for the sake of the good life. Constitutions are correct when rulers aim at the common advantage and deviant when they aim at their own; the most stable is a mixed constitution in which the middle class is strong.

Aristotle (384–322 BCE) was a Greek philosopher and polymath, a pupil of Plato, tutor of Alexander the Great and founder of the Lyceum in Athens. Called “the Stagirite” after his birthplace and, by medieval Christians, “the Philosopher”, he gave the first systematic account of logic and left theories of metaphysics, the soul, ethics and the city that shaped medieval philosophy in the Islamic, Jewish and Christian worlds.

What do we know of his life?

He was born in 384 BCE at Stagira, a small city in Macedonian northern Greece. At about seventeen he went to Athens to study in Plato’s Academy, and he stayed until Plato died in 347. He then spent about five years at Assos and on Lesbos, and in 343 Philip II of Macedon summoned him to tutor the thirteen-year-old Alexander; how long the tutoring lasted is unclear.

Back in Athens in 335, he founded the Lyceum, whose members became known as Peripatetics. After Alexander’s death in 323 he left Athens, probably because of anti-Macedonian feeling, and died the next year at Chalcis on Euboea.

What survives is not what he published. The Stanford Encyclopedia of Philosophy reports that he left perhaps as many as two hundred treatises, of which about thirty-one survive, mostly as lecture notes and drafts; the more polished dialogues, which Cicero praised, survive only in fragments. The name Organon for his logical works is later, and most scholars now think the Constitution of Athens a pupil’s work.

What did he contribute to logic and science?

In the logical works Aristotle set out the syllogism: if A is said of every B, and B of every C, then A is said of every C. Validity depends on form, not subject matter. The Posterior Analytics adds that science is demonstration from first principles, which we reach by induction from experience.

About a quarter of his surviving writings are biology: he dissected animals of many kinds, questioned bee-keepers and fishermen, and explained the parts of animals by the end each serves.

What is a substance, and what are the four causes?

Aristotle’s answer to what exists begins with substance: individual things are primary, and qualities, quantities and places depend on them. Each ordinary thing is a composite of matter and form (hylomorphism), and it is explained by four causes; in his biology the final cause, the end for the sake of which something develops, comes first. Change is the actualising of a potentiality, and the chain of change ends, in the Metaphysics, in an unmoved mover that is pure thinking and moves the heavens as the object of desire.

In On the Soul, the soul is the form of a living body, with nutritive, perceptive and rational capacities, so that mind and body are inseparable, though distinct in thought.

What is the good life?

The Nicomachean Ethics argues from function. A good harp-player plays the harp well; the work of a human being is a working of the soul in accordance with reason; so, in Chase’s translation, the Good of Man is “a working of the Soul in the way of Excellence”, and, he adds, “it is not one swallow or one fine day that makes a spring”. That is eudaimonia, flourishing.

A virtue of character is formed by habit and lies at the mean, which Aristotle says is relative to us: “that which is neither too much nor too little for the particular individual”. Courage lies between cowardice and rashness. What finds the mean in a particular case is practical wisdom, which cannot be reduced to rules. This is the root of modern virtue ethics. Book X ranks contemplation highest, and scholars disagree how that fits with the rest.

What did he say about the city?

William Ellis’s translation of the Politics says that “man is naturally a political animal”. The Ethics ends by pointing to the Politics: people become good through laws and institutions. Aristotle classes constitutions as correct or deviant by whether rulers aim at the common advantage, and commends a mixed constitution in which the middle class is strong, as freest from faction. He also argued that some people are slaves by nature and that the deliberative faculty in women lacks authority. The Stanford Encyclopedia finds these arguments unconvincing to modern readers, and any honest reading of the Politics must weigh them.

The Poetics defines tragedy as an imitation (mimesis) of an action, “through pity and fear effecting the proper purgation of these emotions” (Butcher), the idea later called catharsis, and holds that poetry is “a more philosophical and a higher thing than history” because it tends to express the universal.

What came after him?

Medieval Muslim scholars called him “the First Teacher”, and al-Farabi was in turn called the “Second Master”. Ibn Rushd was known in the West as “the Commentator”, Maimonides drew on him, and Thomas Aquinas built a synthesis of Aristotle and Christian doctrine. His physics was not systematically replaced until the Enlightenment, and his logic remained influential into the nineteenth century.

How should you start reading Aristotle?

Begin with the Nicomachean Ethics, Book I chapter 7 on the function argument and Book II chapter 6 on the mean, in the library. Then read the opening of the Politics and the central chapters of the Poetics. The Categories, Metaphysics and On the Soul are harder; use a modern translation with notes.