Justice is a virtue of the soul. Myth of the ring of Gyges shows that only the fear of getting caught or the reward of others' respect is the motive for being just. Socrates must show that justice is good in itself and not just for the co nsequences. Wisdom The justice of the state is the harmonious working together of the three classes, each one doing what it is best able to do. Purpose is to promote good character in a good body.
People learn by imitation.
People will imitate characters in stories and dramas. Therefore, poetry and drama must be censored to promote good character. Method of proof is useful training for doing philosophy. Harmonics the theory of ratios not just of audible sounds but a general theory. Plato suggests that a unified theory of mathematics ultimately derived from the One should be possible.