Glaucon asks Socrates if he can provide a defense of justice (right conduct) that will show not only that justice is good for the sake of its consequences but it is good in and of itself. In one of the most famous parts of Book II, Glaucon presents the myth of Gyges ring -- the ring of invisibility. Socrates must show that a just person would never use the ring to make himself invisible and do an unjust (wrong) act. There are other challenges of Glaucon. At the conclusion of Book II, Socrates begins to build his case by drawing an analogy between a just city and a just person.