Prudence as well as Moral Virtue determines the complete performance of a man's proper function: Virtue ensures the rightness of the end we aim at, Prudence ensures the rightness of the means we adopt to gain that end.
AristotleThe soul has two parts, one rational and the other irrational. Let us now similarly divide the rational part, and let it be assumed that there are two rational faculties, one whereby we contemplate those things whose first principles are invariable, and one whereby we contemplate those things which admit of variation.
Aristotle