Happiness is the highest good and the end at which all our activities ultimately aim. All our activities aim at some end, though most of these ends are means toward other ends. For example, we go grocery shopping to buy food, but buying food is itself a means toward the end of eating well and thriftily. Eating well and thriftily is also not an end in itself but a means to other ends. Only happiness is an end in itself, so it is the ultimate end at which all our activities aim. As such, it is the supreme good. The difficulty is that people don’t agree on what makes for a happy or good life, so the purpose of the Ethics is to find an answer to this question. By its nature, the investigation is imprecise because there are so many variables involved when considering a person’s life as a whole.

Aristotle defines the supreme good as an activity of the rational soul in accordance with virtue. Virtue for the Greeks is equivalent to excellence. A man has virtue as a flautist, for instance, if he plays the flute well, since playing the flute is the distinctive activity of a flautist. A virtuous person is someone who performs the distinctive activity of being human well. Rationality is our distinctive activity, that is, the activity that distinguishes us from plants and animals. All living things have a nutritive soul, which governs growth and nutrition. Humans and animals are distinct from plants in having a sensitive soul, which governs locomotion and instinct. Humans are distinct above all for having also a rational soul, which governs thought. Since our rationality is our distinctive activity, its exercise is the supreme good.

Aristotle defines moral virtue as a disposition to behave in the right manner and as a mean between extremes of deficiency and excess, which are vices. We learn moral virtue primarily through habit and practice rather than through reasoning and instruction. Virtue is a matter of having the appropriate attitude toward pain and pleasure. For example, a coward will suffer undue fear in the face of danger, whereas a rash person will not suffer sufficient fear. Aristotle lists the principle virtues along with their corresponding vices, as represented in the following table. A virtuous person exhibits all of the virtues: they do not properly exist as distinct qualities but rather as different aspects of a virtuous life.

We can only be held responsible for actions we perform voluntarily and not for cases involving physical compulsion or unavoidable ignorance. The best measure of moral judgment is choice, since choices are always made voluntarily by means of rational deliberation. We always choose to aim at the good, but people are often ignorant of what is good and so aim at some apparent good instead, which is in fact a vice.

The Nicomachean Ethics advances an understanding of ethics known as virtue ethics because of its heavy reliance on the concept of virtue. The word we translate as virtue is aretê, and it could equally be translated as “excellence.” Something has aretê if it performs its function well. A good horseman, for example, has the aretê of being good at handling horses, and a good knife has the aretê of sharpness. For the Greeks, moral virtue is not essentially different from these other kinds of excellence. The Greeks do not have a distinctive concept of morality like we do, which carries associations of sanctity or duty. Moral virtue is simply a matter of performing well in the function of being human. For the Greeks, the motivation for being good is not based in a divine legislator or a set of moral dos and don’ts but rather in the same kind of striving after excellence that might make an athlete train hard. The Greek word ethos, from which we derive the word ethics, literally means “character,” and Aristotle’s goal is to describe what qualities constitute an excellent character.

The important lesson to draw from Aristotle’s Doctrine of the Mean is that virtue consists of finding an appropriate middle ground between two extremes. As such, each virtue has not one opposite but two. The opposite of courage is both cowardice and rashness, for example. This idea that there are two opposites for every virtue goes against much of the received wisdom of Aristotle’s time, including Plato’s writings on virtue. It also emphasizes the importance of moderation: we achieve virtue by finding a middle ground, not by aiming for an extreme. Where exactly this middle ground lies, however, is less obvious. Aristotle repeats a number of times that his table presents only a rough approximation and that virtues lie closer to one vice than another to different extents for different people. The Table of Virtues just presented is not intended as a set of exact rules. On the contrary, Aristotle argues that a truly virtuous person will naturally be inclined to behave appropriately and will have no need of rules.

Aristotle is clear that we arrive at moral virtue primarily through practice and that the value of studying ethical texts such as the one he has written is limited. This view makes sense when we consider that moral virtue is not essentially different from other forms of excellence as far as the Greeks are concerned. If we want to achieve excellence in rock climbing, for instance, it helps to study texts that show us how to improve our technique, but we can’t make any significant improvements except by getting on a rock wall and practicing. Analogously, it helps to read texts like the Nicomachean Ethics to get a clearer understanding of moral virtue, but the only way to become more virtuous is through practice. We can only become more courageous by making a point of facing down our fears, and we can only become more patient by making a habit of controlling our anger. Since practice, not study, is the key to becoming virtuous, Aristotle takes a strong interest in the education of the young. He perceives that there is only so much we can do to improve a nasty adult, and we can more easily mold virtuous youths by instilling the proper habits in them from a young age.

Aristotle calls happiness an “activity,” which distinguishes his conception of happiness both from our modern conception of happiness and from virtue, which Aristotle calls a “disposition.” We tend to think of happiness as an emotional state and hence as something we are, rather than as something we do. The Greek word generally translated as “happiness” is eudaimonia, and it can equally be rendered as “success” or “flourishing.” People who are eudaimon are not in a particular emotional state so much as they are living successfully. While happiness is the activity of living well, virtue represents the potential to live well. Excelling in all the moral virtues is fine and good, but it doesn’t ensure our happiness unless we exercise those virtues. Courageous people who never test their courage by facing down fear have virtue, but they are not happy. Aristotle illustrates this distinction between happiness and virtue by saying that the best athletes only win at the Olympic Games if they compete. A virtuous person who does not exercise virtue is like an athlete who sits on the sideline and watches. Aristotle has a proactive conception of the good life: happiness waits only for those who go out and seize it.