M. Tullius Cicero, De Officiis
Walter Miller, Ed.

[4] I believe, of course, that if Plato had been willing to devote himself to forensic oratory, he could have spoken with the greatest eloquence and power; and that if Demosthenes had continued the studies he pursued with Plato and had wished to expound his views, he could have done so with elegance and brilliancy. I feel the same way about Aristotle and Isocrates, each of whom, engrossed in his own profession, undervalued that of the other.

[p. 7] 2. But since I have decided to write you a little¹ now (and a great deal by and by), I wish, if possible, to begin with a matter most suited at once to your years and to my position. Although philosophy offers many problems, both important and useful, that have been fully and carefully discussed by philosophers, those teachings which have been handed down on the subject of moral duties seem to have the widest practical application. For no phase of life, whether public or private, whether in business or in the home, whether one is working on what concerns oneself alone or dealing with another, can be without its moral duty; on the discharge of such duties depends all that is morally right, and on their neglect all that is morally wrong in life.