The pronoun you, which grammarians had fixed to be of the plural number, was then occasionally used, but less than it is now, in addressing an individual.

George Fox therefore adopted thou in its place on this occasion, leaving the word you to be used only where two or more individuals were addressed.
George Fox however was not the first of the religious writers, who had noticed the improper use of the pronoun you.

Erasmus employed a treatise in shewing the propriety of thou when addressed to a single person, and in ridiculing the use of you on the same occasion.

Martin Luther also took great pains to expunge the word you from the station which it occupied, and to put thou in its place.

In his Ludus, he ridicules the use of the former by the, following invented sentence, "Magister, Vosestis iratus ?" This is as absurd, as if he had said in English "gentlemen art thou angry"?
But though George Fox was not the first to recommend the substitution of thou for you, he was the first to reduce this amended use of it to practice.