Not every action or emotion however admits of the observance of a due mean. Indeed the very names of some directly imply evil, for instance malice, shamelessness, envy, and, of actions, adultery, theft, murder. All these and similar actions and feelings are blamed as being bad in themselves; it is not the excess or deficiency of them that we blame. It is impossible therefore ever to go right in regard to them - one must always be wrong.
AristotleWhereas young people become accomplished in geometry and mathematics, and wise within these limits, prudent young people do not seem to be found. The reason is that prudence is concerned with particulars as well as universals, and particulars become known from experience, but a young person lacks experience, since some length of time is needed to produce it.
AristotleAgain, it is possible to fail in many ways (for evil belongs to the class of the unlimited and good to that of the limited), while to succeed is possible only in one way (for which reason also one is easy and the other difficultโto miss the mark easy, to hit it difficult); for these reasons also, then, excess and defect are characteristic of vice, and the mean of virtue; For men are good in but one way, but bad in many.
Aristotle