
“Let the orator whom I propose to form, then, be such a one as is characterized by the definition of Marcus Cato, a good man skilled in speaking. But the requisite which Cato has placed first in this definition—that an orator should be a good man—is naturally of more estimation and importance than the other.”
Sit ergo nobis orator quem constituimus is qui a M. Catone finitur vir bonus dicendi peritus, verum, id quod et ille posuit prius et ipsa natura potius ac maius est, utique vir bonus.
Book XII, Chapter I, 1; translation by Rev. John Selby Watson
De Institutione Oratoria (c. 95 AD)