Discourses, "Of Disputation or Discussion" (§1)

“What things a man must learn in order to be able to apply the art of disputation, has been accurately shown by our philosophers (the Stoics); but with respect to the proper use of the things, we are entirely without practice. Only give to any of us, whom you please, an illiterate man to discuss with, and he cannot discover how to deal with the man.”