Moral virtue is ... a mean between two vices, that of excess and that of defect, and ... it is no small task to hit the mean in each case, as it is not, for example, any chance comer, but only the geometer, who can find the center of a given circle.
The Good of man is the active exercise of his soul's faculties in conformity with excellence or virtue, or if there be several human excellences or virtues, in conformity with the best and most perfect among them.
It has been well said that 'he who has never learned to obey cannot be a good commander.' The two are not the same, but the good citizen ought to be capable of both; he should know how to govern like a freeman, and how to obey like a freeman - these are the virtues of a citizen.
It [Justice] is complete virtue in the fullest sense, because it is the active exercise of complete virtue; and it is complete because its possessor can exercise it in relation to another person, and not only by himself.
The life of theoretical philosophy is the best and happiest a man can lead. Few men are capable of it and then only intermittently. For the rest there is a second-best way of life, that of moral virtue and practical wisdom.