On Moral Duties (De Officiis)

The essay discusses what is honorable (Book I), what is expedient or to one's advantage (Book II), and what to do when the honorable and expedient conflict (Book III). Cicero says they are the same and that they only appear to be in conflict. In Book III, Cicero expresses his own ideas. Michael Grant tells us that "Cicero himself seems to have regarded this treatise as his spiritual testament and masterpiece."