And this was done, because the rules of the English grammar warranted the expression, and because any other mode of expression would have been a violation of these rules.
But the great argument (to omit all others) which Penn and Barclay insisted upon for the change of you, was that the pronoun thou, in addressing an individual, had been anciently in use, but that it had been deserted for you for no other purpose, than that of flattery to men; and that this dereliction of it was growing greater and greater, upon the same principle, in their own times.

Hence as christians, who were not to puff up the fleshly creature, it became them to return to the ancient and grammatical use of the pronoun thou, and to reject this growing fashion of the world.

"The word you, says William Penn, was first ascribed in the way of flattery, to proud Popes and Emperors, imitating the heathens vain homage to their gods, thereby ascribing a plural honour to a single person; as if one Pope had been made up of many gods, and one Emperor of many men; for which reason you, only to be addressed to many, became first spoken to one.

It seemed the word thou looked like too lean and thin a respect; and therefore some, bigger than they should be, would have a style suitable to their own ambition." It will be difficult for those, who now use the word you constantly to a single person, and who, in such use of it, never attach any idea of flattery to it, to conceive how it ever could have had the origin ascribed to it, or, what is more extraordinary, how men could believe themselves to be exalted, when others applied to them the word you instead of thou.

But history affords abundant evidence of the fact.
It is well known that Caligula ordered himself to be worshipped as a god.