While virtue makes man choose the right ends, practical wisdom makes him choose the right means, but practical wisdom cannot exist independently of virtue. The power to attain an end, whether good or bad, is mere talent or cleverness, and is raised above the level of roguery only by the presence of virtue. Just as practical wisdom implies moral virtue, moral virtue in the proper sense implies practical wisdom, and it is impossible to develop moral virtue without thorough training in practical wisdom.
A man may start life with a natural virtue (e.g.. a disposition to be just or temperate), but if this is unaccompanied by knowledge of the effects that various kinds of action are likely to have, this disposition can never become genuine moral virtue and remains wasteful or even dangerous. Thus, in its true sense, virtue cannot be complete without the possession of practical wisdom. Socrates was wrong when he said that virtue was only wisdom, but he was right to see that virtue is a form of knowledge.
Though the natural virtues can exist in isolation from each other, the moral virtues are interdependent, for possession of any moral virtue implies possession of practical wisdom, and possession of practical wisdom implies possession of all the moral virtues. A man with practical wisdom controls his instinctive tendencies and directs his own life to the highest good — balanced development of his moral character (i.e., virtue).
As a final point, it may be mentioned that practical wisdom is subordinate to theoretical wisdom, but since practical wisdom determines what studies are pursued in any state, it acts in the interests of theoretical wisdom.
To sum up, practical wisdom or prudence is excellence of the deliberative faculty of the soul and enables one to exercise right choice. It enables us to choose the right means for attaining the right ends as determined by virtue. While not the same as virtue, practical wisdom makes the existence of virtue possible. The right rule reached by the deliberative analysis of a man with practical wisdom tells him that the end of human life is attained by certain actions that are intermediate between extremes. Moral virtue can be defined as obedience to this rule.