ring of Gyges a ring that gives its wearer invisibility, discussed in Plato’s Republic (II, 359b– 360d). Glaucon tells the story of a man who discovered the ring and used it to usurp the throne to defend the claim that those who behave justly do so only because they lack the power to act unjustly. If they could avoid paying the penalty of injustice, Glaucon argues, everyone would be unjust. See also PLATO, SOCRATES. W.J.P.