From Euthydemus by Plato: Socrates on True Happiness

Them wisdom always makes men happy: for be wisdom no man would ever err, and therefore he must act rightly and succeed, or his wisdom would be wisdom no longer. Appears to be that the goods of which we spoke before are not to be regarded as goods in themselves, but the degree of good and evil in them depends on whether they are or are not under the guidance of knowledge: under the guidance of ignorance, they are greater evils than their opposites, inasmuch as they are more able to minister to the evil principle which rules them; and when under the guidance of wisdom and prudence, they are greater goods.