That one man should be lord ever many thousand Romans, who were the masters of the world was in itself a degrading thought.

But they consoled themselves by the haughty consideration, that they were yielding obedience, not to man, but to an incarnate demon or good genius, or especial envoy from heaven.

They considered also the emperor as an office, and as an office, including and representing many other offices, and hence considering him as a man in the plural number, they had less objection to address him in a plural manner.
The Quakers, in behalf of their assertions on this subject, quote the opinions of several learned men, and of those in particular, who, from the nature of their respective writings, had occasion to look into the origin and construction of the words and expressions of language.
Howell, in his epistle to the nobility of England before his French and English Dictionary, takes notice, "that both in France, and in other nations, the word thou was used in speaking of one, but by succession of time, when the Roman commonwealth grew into an empire, the courtiers began to magnify the emperor, as being furnished with power to confer dignities and offices, using the word you, yea, and deifying him with more remarkable titles, concerning which matter we read in the epistles of Symmachus to the emperors Theodosius and Valentinian, where he useth these forms of speaking, Vestra AEternitas, vestrum numen, vestra serenitas, vestra Clementia, that is, your, and not thy eternity, godhead, serenity, clemency.

So that the word you in the plural number, together with the other titles and compellations of honour, seem to have taken their rise from despotic government, which afterwards, by degrees, came to be derived to private persons." He says also in his History of France, that "in ancient times, the peasants addressed their kings by the appellation of thou, but that pride and flattery first put inferiors upon paying a plural respect to the single person of every superior, and superiors upon receiving it." John Maresius, of the French Academy, in the preface to his Clovis, speaks much to the same effect.

"Let none wonder, says he, that the word thou is used in this work to princes and princesses, for we use the same to God, and of old the same was used to Alexanders, Caesars, queens, and empresses.