All human activities aim at some end that we consider good. Most activities are a means to a higher end. The highest human good, then, is that activity that is an end in itself. That good is happiness. When we aim at happiness, we do so for its own sake, not because happiness helps us realize some other end. The goal of the Ethics is to determine how best to achieve happiness. This study is necessarily imprecise, since so much depends on particular circumstances.

Happiness depends on living in accordance with appropriate virtues. Virtue is a disposition rather than an activity. That is, a virtuous person is naturally disposed to behave in the right ways and for the right reasons, and to feel pleasure in behaving rightly. Virtue is a mean state between the extremes of excess and deficiency. This mean varies from person to person, so there are no hard and fast rules as to how best to avoid vice.

Only voluntary actions are praiseworthy or blameworthy. We can define voluntary action as any action that originates in the agent and not in some outside force like a push or a stumble. There are borderline cases, however, as when someone is compelled to behave dishonorably under severe threat. Voluntary action is characterized by rational deliberation and choice, where the agent determines the best course of action by reasoning how best to achieve desirable ends.

One by one, Aristotle discusses the various moral virtues and their corresponding vices. Courage consists of confidence in the face of fear. Temperance consists of not giving in too easily to the pleasures of physical sensation. Liberality and magnificence consist of giving away varying amounts of money in appropriate and tasteful ways. Magnanimity and proper ambition consist of having the right disposition toward honor and knowing what is one’s due. Patience is the appropriate disposition toward anger, though it is sometimes appropriate to show some degree of anger. The three social virtues of amiability, sincerity, and wit make for pleasant and engaging interaction with others. Modesty is not properly a virtue, but an appropriate disposition toward shame, which is admirable in the young.

Justice in a sense encompasses all the other virtues, since being just consists of exhibiting virtue generally. In human affairs, there are two primary forms of justice: distributive and rectificatory. Distributive justice deals with the distribution of wealth or honors among a group of people and should be given according to merit. Rectificatory justice deals with exchanges between two or more people and should always aim at restoring a sense of balance and equality between the people concerned. It is impossible to treat oneself unjustly or to suffer injustice willingly. While the laws are a good guideline, they do not cover every particular case. On occasion, agreed-upon equity must settle cases that the laws do not.

While the moral virtues dispose us to behave in the correct manner, it is necessary also to have the right intellectual virtues in order to reason properly about how to behave. There are five intellectual virtues. Three of them—scientific knowledge, intuition, and wisdom—consist of contemplative reasoning, which is detached from human affairs. The other two—art or technical skill and prudence—consist of calculative reasoning, which helps us make our way in the world. Prudence is the intellectual virtue that helps us reason properly about ethical matters.

Incontinence is a peculiar form of badness. Unlike vice, incontinence does not involve willing bad behavior. Rather, it consists of knowing what is good but lacking the self-control to do good. Incontinence is not as bad as vice, since it is partially involuntary.

There are three kinds of friendship: friendship based on utility, friendship based on pleasure, and friendship based on goodness of character. The first two kinds of friendship are based on superficial qualities, so these sorts of friendship are not generally long lasting. Friendship based on goodness of character is the best kind of friendship, because these friends love one another for who they are and not for what they stand to gain from one another. Friendship generally exists between equals, though there are cases, like the father-son relationship, which rely on unequal exchanges.

Political institutions rely on friendly feelings between citizens, so friendship and justice are closely connected. There are three forms of constitution based on different kinds of relationships. Of the three, monarchy is preferable to aristocracy or timocracy.

Ideally, our feelings for our friends should reflect our feelings for ourselves. Self-love is more important than friendship, since only people who treat themselves with appropriate care and respect can achieve proper virtue and happiness. Though a happy person is theoretically self-sufficient, friendship is an important and essential aspect of the good life.

Pleasure accompanies and perfects our activities. A good person will feel pleasure in doing good things. The highest good of all is rational contemplation. A life that consists exclusively of contemplation is obviously impossible, but we should aim to approximate this ideal as closely as possible. The practical sciences, then, help us find the right path toward this highest good and help us deal with the practical matters of everyday life that inevitably occupy a great deal of our time and attention.