Populism and "the Constitution" in Dickens

From "Bleak House" (chapter 16, "Tom-all-Alone's"):

It must be a strange state to be like Jo! To shuffle through the streets, unfamiliar with the shapes, and in utter darkness as to the meaning, of those mysterious symbols, so abundant over the shops, and at the corners of streets, and on the doors, and in the windows! To see people read, and to see people write, and to see the postmen deliver letters, and not to have the least idea of all that language—to be, to every scrap of it, stone blind and dumb! It must be very puzzling to see the good company going to the churches on Sundays, with their books in their hands, and to think (for perhaps Jo DOES think at odd times) what does it all mean, and if it means anything to anybody, how comes it that it means nothing to me? To be hustled, and jostled, and moved on; and really to feel that it would appear to be perfectly true that I have no business here, or there, or anywhere; and yet to be perplexed by the consideration that I AM here somehow, too, and everybody overlooked me until I became the creature that I am! It must be a strange state, not merely to be told that I am scarcely human (as in the case of my offering myself for a witness), but to feel it of my own knowledge all my life! To see the horses, dogs, and cattle go by me and to know that in ignorance I belong to them and not to the superior beings in my shape, whose delicacy I offend! Jo's ideas of a criminal trial, or a judge, or a bishop, or a government, or that inestimable jewel to him (if he only knew it) the Constitution, should be strange!