“I have broken free of that, like a slave who has got away from a rabid and savage master.” 

Socrates has just asked the elderly Cephalus whether he misses any of the physical pleasures of youth, such as sex or drinking. Cephalus responds that, far from missing them, he feels liberated by not having these desires. This exchange sets the tone for Socrates’ later criticisms of bodily pleasure as associated with enslavement.

“…it has to be the art of giving benefit and harm to friends and enemies respectively.” 

Polemarchus attempts to define morality in response to Socrates’ question. He repeats the conventional view that it is about helping those close to you. However, this definition rests on the shaky premise that we always necessarily choose good friends.

“Suppose there were two such rings, then—one worn by our moral person, the other by the immoral person.” 

Glaucon uses a myth to outline the cynical position that morality is a form of self-justification on the part of people too weak or cowardly to be immoral. The myth is about a magic ring that gives its wearer the power to turn invisible. Glaucon wonders whether an ostensibly moral person would act differently to the immoral one if he were given the ring.