This statement, which appears in Book I, Chapter 3, is the first of a number of caveats with which Aristotle warns us not to expect any precise rules or codes of conduct. This is not laziness on Aristotle’s part, but, as he explains, the nature of the beast. Ethics deals with the vagaries of human life and must remain flexible enough to account for the great deal of variety and possibility.

Furthermore, Aristotle tells us that virtue cannot be taught in a classroom but can be learned only through constant practice until it becomes habitual. If virtue consisted of hard and fast rules, it would indeed be possible to lay them out explicitly in a classroom. Unfortunately for those hoping for the easy road to success, no such rules exist. Knowing what to do is a matter of applying phronesis, or prudence, on a case-by-case basis.

This quotation from Book I, Chapter 7, connects Aristotle’s conception of happiness and the good life with his conception of virtue. We should observe first that “the good for man is an activity.” The word activity translates from the Greek energeia, which signifies not only physical activity but also mental activity as seemingly inactive as contemplation or daydreaming. The point is that the good life is not an end state that we achieve but rather a way of life that we live. We might consider the cliché “life is a journey, not a destination” to convey some sense of the distinction Aristotle has in mind.

The bulk of the Ethics is devoted to discussing the various moral and intellectual virtues. These virtues are dispositions to behave in the correct way. They are not themselves activities, but they ensure that our activities will be of the right kind. To live “in accordance with virtue,” then, is to live in such a way that our activities flow naturally from a virtuous disposition.

In Books VI and X, Aristotle suggests that the intellectual virtue of wisdom is the “best and most perfect kind” of virtue, and he ultimately concludes that the good for man is rational contemplation in accordance with the intellectual virtue of wisdom.

This quotation from Book II, Chapter 6, gives us a clear expression of Aristotle’s Doctrine of the Mean: virtue is a mean disposition between the vicious extremes of excess and deficiency. In calling virtue a “purposive” disposition, Aristotle means that virtue is not just a disposition we sit on and do nothing about, but is rather the impetus that leads us to virtuous activity.

Aristotle gives no rules as to what counts as a mean. His reason is that the mean depends greatly on the person and the situation. Rather than lay down any rules, he recommends phronesis, or prudence, which helps us reason our way through practical matters and determine the best course to take.

Aristotle makes this assertion in Book VIII, Chapter 1. Neither friendship nor justice is listed in Aristotle’s table of virtues and vices, because both are more general than the particular virtues and vices listed there. In Book V, Aristotle explains that justice comprehends all the virtues, since acting justly consists essentially of acting in accordance with all the virtues.

Aristotle bases his conception of justice on a conception of fair exchange, and does the same for friendship. Friendships are balanced by the fact that each friend gives as much as receives. Hence, justice and friendship are closely connected.

Citizens in the Greek city-states were expected to take a very active role in the government of their city-state, so justice and civic duty would have been a concern for all. A complete life could not have been lived in solitude, so justice and friendliness between fellow citizens was essential.

Near the end of the Ethics, in Book X, Chapter 7, Aristotle concludes that contemplation is the highest human good. Aristotle distinguishes rationality, and the intellect in particular, as the highest human functions, since these are the functions that distinguish us from other animals. It is also through the intellect that we can think about philosophy, God, and nature, which Aristotle considers to be far more noble objects of thought than the daily matters of human society. Consequently, he reasons that a life of continuous contemplation is the best possible human life. Of course, life cannot consist solely of contemplation, since practical matters always need dealing with, but in Aristotle’s view, the more contemplation the better. Practical wisdom and the moral virtues are noble and essential to securing the good life, but the good life itself consists foremost of contemplation.