We have been told that virtue comes about by choosing a mean between vicious extremes according to the right principle. This is only as helpful as telling a sick person that health comes about by choosing medicine according to what a doctor might prescribe. That is, we have no helpful understanding of virtue until we learn what this right principle is. To learn about the right principle, we must examine the intellectual virtues.

The soul is divided into a rational part and an irrational part. The rational part can be further divided into a contemplative part, which studies the invariable truths of science and mathematics, and a    calculative part, which deals with the practical matters of human life. Right reasoning with respect to the contemplative intellect   corresponds to truth. With the practical intellect, right reasoning corresponds to proper deliberation that leads to making the right choice.

There are five intellectual virtues by which the soul arrives at truth. First, scientific knowledge arrives at eternal truths by means of deduction or induction. Second, art or technical skill involves production according to proper reasoning. Third, prudence or practical wisdom helps us to pursue the good life generally. Fourth, intuition helps us to grasp first principles from which we derive scientific truths. Fifth, wisdom is a combination of scientific knowledge and intuition, which helps us arrive at the highest truths of all. Political science is a species of prudence, since it involves ensuring the good life for an entire city.

Resourcefulness, or good deliberation, is not the same thing as scientific knowledge, opinion, or conjecture. It is a process that helps achieve the ends envisaged by prudence. Understanding is a form of judgment regarding practical matters, which helps us determine what is equitable. Judgment, understanding, prudence, and intuition are all natural gifts that help us determine the right course of action.

The intellectual virtues help us to know what is just and admirable, and the moral virtues help us to do just and admirable deeds. We might wonder what value the intellectual virtues have, then, since knowledge is useless without action. First, the intellectual virtues lead to happiness, and so are ends in themselves. Second, the intellectual virtues help us determine the best means to the ends at which the moral virtues teach us to aim. Without prudence and cleverness, a well-disposed person can never be truly virtuous, because these intellectual virtues help us grasp the right principles of action.


At the beginning of Book II, Aristotle distinguishes between moral virtues, which we learn through habit and practice, and intellectual virtues, which we learn through instruction. Books II to V deal with the moral virtues. Book 6 turns to intellectual virtues.

Within intellectual virtue, Aristotle distinguishes the contemplative from the calculative. Contemplative reasoning deals with eternal truths. For Aristotle, these are truths unrelated to human action, as revealed in the natural sciences and mathematics. Contemplative reasoning makes use of the intellectual virtues of scientific knowledge, intuition, and wisdom. Scientific knowledge consists mostly of logical inferences derived from first principles. These first principles cannot themselves be inferred through scientific reasoning, but can be grasped only through intuition.

Wisdom is a combination of intuition and scientific knowledge, involving a deep understanding of the natural world. The Greek word for wisdom is sophia, and our word philosopher literally means “lover of wisdom.” Wisdom is the highest of all intellectual virtues, because it involves a profound understanding of the eternal truths of the universe. Such understanding is brought about by philosophy. Though Aristotle thinks his work on ethics and politics is important, he rates his work on science, metaphysics, and logic as much more important.

However, the Ethics is concerned with the practical and noneternal matters of the human world, so contemplative reasoning receives relatively brief mention. So does art, or technical skill, which is important mostly to artists and artisans, and does not fall within the scope of the Ethics. Art, or technical skill, guides us in the correct manner of producing things. Prudence, or practical wisdom, guides us in the correct manner of action. This intellectual virtue, which is closely tied to the rational deliberation and choice necessary to the moral virtues, is the central focus of Aristotle’s discussion of the intellectual virtues in Nicomachean Ethics.

The Greek word translated as “prudence” or “practical wisdom” is phronesis, which conveys a general sense of knowing the proper behavior in all situations. Phronesis is an intellectual virtue rather than a moral virtue because we learn it through instruction and not practice, but it is very closely connected to the moral virtues. Without phronesis, it would be impossible to practice the moral virtues properly. A person who has all the right moral virtues knows what ends to pursue, but without phronesis, that person will not know how to set about pursuing the right ends. Contrary to modern assumptions, Aristotle is telling us that having one’s heart in the right place is not good enough: being a good person requires a kind of practical intelligence as well as a good disposition.

On the other hand, a person who has phronesis but does not have the right moral virtues will be very effective in devising means to personal ends, but those ends might not be noble. The villain in a James Bond film might be seen as a portrait of a person with phronesis but no moral virtue.

The logical syllogism, which was invented and perfected by Aristotle, consists of three terms: a major premise, which states some general truth; a minor premise, which states some particular truth; and a conclusion. For instance, the major premise “all humans are mammals” and the minor premise “Aristotle is a human” lead to the conclusion “Aristotle is a mammal.” Aristotle takes the syllogism to be the basic unit of reasoning and applies it not only to reasoning in the sciences but also to practical reasoning.

Phronesis, then, consists of practical syllogisms with three terms. The major premise states some general practical truth—for example, “Always hold the door open for elderly people.” The minor premise states a particular fact related to the major premise—for example, “An elderly person is coming toward this door.” The conclusion is the action that the major and minor premises entail—in other words, holding the door open for the elderly person.

The practical syllogism cannot be completed without both moral virtue and phronesis. Moral virtue supplies us with the appropriate major premises, and phronesis helps us to move from the major premise to an appropriate course of action. Without phronesis, the virtuous person would not necessarily know how to act, and without moral virtue, the clever person would not always pursue the appropriate ends.