Nicomachean Ethics

Chapter-by-chapter summary

Aristotle's text is divided into ten books. Each one is summarised below in order, with a line on why it matters.

Book I: The Good and Happiness

Aristotle begins by noting that every skill and choice aims at some good, and that these aims are ranked: bridle-making serves horse riding, which serves winning a war. The top of the ladder has to be something we want for its own sake. Nearly everyone calls that happiness (eudaimonia), but people disagree about what it is. He sets aside pleasure, honour and wealth, then argues from the human function: if the work of a human is reasoning well, happiness is activity of the soul that follows excellence, over a whole life. Why it matters: every later book answers this opening question.

Book II: Virtue and the Mean

Here Aristotle splits excellence into two kinds: excellence of thought, which is taught, and excellence of character, which is built by habit. We become just by doing just things and brave by doing brave things, much as builders learn by building. He then says that a virtue sits at a mean between two faults, one of excess and one of deficiency, and that the mean is relative to the person and the situation. Courage lies between cowardice and recklessness. Why it matters: ethics becomes training. Character is not a gift or a verdict but something we practise into being.

Book III: Choice, Courage and Temperance

This book asks when someone is responsible for what they do. An act is voluntary when its cause lies in the person and they know what they are doing; force and real ignorance excuse. Aristotle then describes choice as deliberate desire shaped by thinking about the means. He looks at two virtues: courage, which means facing fear for a worthy purpose, especially in battle, and temperance, which means moderation in bodily pleasures such as food and drink. Why it matters: praise and blame make sense only for actions that really belong to us.

Book IV: The Social Virtues

Book IV is a tour of the virtues of everyday life. Generosity is the right way to give and take money, and magnificence is the right way to spend big on public projects. Greatness of soul is a fitting sense of one's own worth, between vanity and false modesty. The book goes on to cover proper ambition, good temper in anger, friendliness, truthfulness about oneself and wit in play. Each has a mean and two faults. It closes with shame, which Aristotle treats as a feeling rather than a virtue. Why it matters: manners, money and conversation count as part of the moral life.

Book V: Justice

Book V is about justice. Aristotle separates general justice, which means obeying good laws, from particular justice, which is fairness in sharing out goods and in setting wrongs right. Distributive justice gives each person a share that matches their merit. Corrective justice restores balance after harm, like a judge who treats the two sides as equals. He also discusses fair exchange in trade, the role of money, and equity, which repairs the places where a law is too blunt for a case. Why it matters: it is one of the first careful accounts of fairness, and it still shapes how lawyers and philosophers talk about it.

Book VI: Intellectual Virtues and Practical Wisdom

Having covered virtues of character, Aristotle turns to virtues of thought. He lists five ways the mind reaches truth: craft knowledge, scientific knowledge, intuitive grasp of first principles, theoretical wisdom, and practical wisdom (phronesis). Practical wisdom is the ability to work out the right thing to do in a particular case. He argues that real virtue of character cannot exist without it, and that it cannot exist without good character. Why it matters: rules alone do not make a good person. Judgement in real situations links the mean to action.

Book VII: Self-Control and Pleasure

This book examines why people act against their own best judgement, a state called akrasia, often translated as weakness of will. Socrates had said this is impossible, because knowing the good means doing it. Aristotle disagrees: desire or anger can cloud knowledge in the moment, like a drunk reciting verses he does not feel. He also separates self-control from full virtue and from brutish states. The second half defends pleasure against those who call it always bad. Why it matters: knowing what is right and doing it turn out to be different problems.

Book VIII: Kinds of Friendship

This is the first of two books on friendship (philia). Aristotle says friendship is needed at every stage of life, by the young and the old, the rich and the poor. He lists three kinds, based on usefulness, on pleasure, or on goodness. Friendships of use and pleasure last only as long as the benefit does. Friendships between good people who value each other for who they are last longest, but they are rare and take time. He also links friendship to community life, comparing forms of government with family relations. Why it matters: it explains why some friendships fade and others last.

Book IX: Friendship in Practice

Book IX handles the difficult cases: what to do when a friend changes, when debts of gratitude conflict, or when a friend turns bad. Aristotle claims that healthy self-love, meaning care for the best part of yourself, is the root of friendship, and he calls a friend “another self”. He asks how many friends a person needs, and concludes that happy people need friends, because sharing life and activity deepens joy. Why it matters: friendship becomes part of happiness itself, not a handy extra.

Book X: Pleasure, Contemplation and Law

The finale returns to pleasure. Aristotle explains why it completes an activity without being the goal itself. Then he comes back to happiness and gives his boldest answer: the best life is contemplation, the use of reason to study what is highest and unchanging. A life of practical virtue among other people comes second. He ends by saying that argument alone cannot make people good; laws and upbringing are needed. That points straight to his Politics. Why it matters: it frames the book's central debate between the philosopher's life and the citizen's life.

Key people and terms

Aristotle

Greek philosopher (384–322 BC), a student of Plato and tutor of Alexander the Great. He founded the Lyceum school in Athens. The Nicomachean Ethics is usually read as his lecture material, edited into ten books.

Plato

Aristotle's teacher at the Academy. In Book I Aristotle criticises Plato's idea of a single Form of the Good, arguing that an abstract good is of little use to someone trying to act well in daily life.

Socrates

Plato's teacher, associated with the view that no one knowingly does wrong. In Book VII Aristotle pushes back, saying this cannot explain why people act against what they know to be best.

Eudaimonia

Usually translated as happiness or flourishing. It means living and acting well over a whole life, not feeling cheerful for a day. It is the goal that all other goals in the book point toward.

Arete (virtue)

The Greek word for excellence: whatever makes something do its job well. Virtues of character, such as courage and justice, come from habit. Virtues of thought, such as practical wisdom, come mainly from teaching and experience.

The mean

The fitting response between too much and too little, relative to the person and the situation. It is not a simple average. Courage, for instance, sits between cowardice and recklessness. Book II explains it.

Phronesis

Practical wisdom: the skill of seeing what to do in a particular situation. Book VI argues that it cannot be separated from good character, and it differs from theoretical wisdom (sophia), which studies unchanging truths.

Akrasia

Often called weakness of will: knowing what is best but acting against it because of desire or emotion. Book VII uses it to test Socrates' claim that knowledge always leads to right action.

Philia

The Greek word for friendship, covering family bonds and close companionship as well as friends. It is broader than romantic love. Books VIII and IX divide it into friendships of use, pleasure and goodness.

Theoria

Contemplation: using reason to study what is eternal and unchanging, for its own sake and not for any practical payoff. Book X calls it the highest form of happiness, with practical life in society coming second.

Writing about this book

The Nicomachean Ethics is a good book for essays because it invites you to test ideas against ordinary life. These questions are starting points; the argument has to be yours.

• Which habits have shaped your character? According to Book II, how could you change one on purpose?
• Pick a situation, such as speaking up in class, and name the “too much” and “too little” versions. What would the mean look like?
• Think of something you know is bad for you but keep doing. Would Socrates or Aristotle explain it better?
• Sort your friendships into use, pleasure and goodness. Does the sorting feel fair?
• If happiness is an activity rather than a mood, what would count as evidence of a happy week?

When you write, keep Aristotle's claims separate from your own opinions: “Aristotle argues…” and “I think…”. Remember that the mean is not a compromise or a refusal to take a stand. It is the search for the best response in a specific case. Quote sparingly and explain each idea in your own words.