In his new home, Athens, Diogenes' mission became the metaphorical adulterating/defacing of the "coinage" of custom. Custom, he alleged, was the false coin of human morality. Instead of being troubled by what is really evil, people make a big fuss over what is merely conventionally evil. This distinction between nature ("physis") and custom ("nomos") is a favorite theme of ancient Greek philosophy, and one that Plato takes up in The Republic, in the legend of the Ring of Gyges.^[7]