Encyclopedia of Philosophy: MORAL PHILOSOPHY: WISDOM AND UNDERSTANDING (the system of aristotle)

Wisdom is a practical virtue which is concerned with what is good for human beings. Wisdom is expressed in practical reasoning: reasoning which starts from a general conception or pattern of human well-being, considers the circumstances of particular cases calling for decision, and concludes with a prescription for action. Aristotle envisages the ethical reasoning of the wise person on the model of the professional reasoning of a physician, who starts with his knowledge of the medical art, applies it to the condition of the particular patient, and then issues, literally, a prescription.  Wisdom, then, is an essential prerequisite for the exercise of moral virtue; without it, the most well-intentioned person may do wrong. But moral virtue is also required for the possession of wisdom; for only the virtuous person has the sound conception of human well-being which is the first premiss of practical reasoning: wickedness perverts us and deludes us about the ultimate grounds of action. So wisdom is impossible without moral virtue.