Discourses: Book 3 2 : 1
There are three fields of study in which the man who is going to be good and excellent must first have been trained. The first has to do with desires and aversions, that he may never fail to get what he desires, nor fall into what he avoids; the second with cases of choice and of refusal, and, in general, with duty, that he may act in an orderly fashion, upon good reasons, and not carelessly; the third with the avoidance of error and rashness in judgement, and, in general, about cases of assent. Among these the most important and especially pressing is that which has to do with the stronger emotions; for a strong emotion does not arise except a desire fails to attain its object, or an aversion falls into what it would avoid. This is the field of study which introduces to us confusions, tumults, misfortunes and calamities; and sorrows, lamentations, envies; and makes us envious and jealous—passions which make it impossible for us even to listen to reason. The second field of study deals with duty; for I ought not to be unfeeling like a statue, but should maintain my relations, both natural and acquired, as a religious man, as a son, a brother, a father, a citizen.