According to Gibbon, in the XXIst chapter of The Decline and Fall of the Roman Empire, the emperor Constantine addressed to the leaders of the contending parties of Orthodoxy and Arianism, to Bishop Alexander of Constantinople, and to the presbyter Arius, a “moderating epistle” in which the emperor tells them that they are arguing about “a trifling and subtle question, concerning an incomprehensible point of law“.
Later on, Constantine himself became embroiled in those same subtle controversies, but what interests me about his epistle is the appeal it contains to “the example of the Greek philosophers” as an ideal model for civilized conversation. Speaking of Constantine, Gibbon writes that,
he seriously recommend to the clergy of Alexandria the example of the Greek philosophers; who could maintain their arguments without losing their temper, and assert their freedom without violating their friendship.
What we have, in that quotation, is, of course, Gibbon’s own subtle recommendation to his readers. Here is a translation of the text in Constantine’s letter, which Gibbon is referring to:
You know that philosophers, though they all adhere to one system, are yet frequently at issue on certain points, and differ, perhaps, in their degree of knowledge. Yet they are brought back to harmony of opinion by the uniting power of their common teachings. (source: http://www.fourthcentury.com/urkunde-17/ )