Let’s suppose, then, that there were two such rings, one worn by a just and the other by an unjust person. Now, no one, it seems, would be so incorruptible that he would stay on the path of justice or stay away from other people’s property, when he could take whatever he wanted from the marketplace with impunity, go into people’s houses and have sex with anyone he wished, kill or release from prison anyone he wished, and do all the other things that would make him like a god among humans…

No one believes justice to be a good when it is kept private, since, wherever either person thinks he can do injustice with impunity, he does it.

-Plato, Book II of The Republic