Read this summary of Plato's Republic. Pay particular attention to the summary of Books 6,7, and 8; the Theory of Universals; to the definition of justice; and to the Ideal City. What are the four types of government which Plato rejects, and why does he reject them?
Socrates' argument is that in the ideal city, a true philosopher with understanding of forms will facilitate the harmonious co-operation of all the citizens of the city – the governance of a city-state is likened to the command of a ship, the Ship of State. This philosopher-king must be intelligent, reliable, and willing to lead a simple life. However, these qualities are rarely manifested on their own, and so they must be encouraged through education and the study of the Good. Just as visible objects must be illuminated in order to be seen, so must also be true of objects of knowledge if light is cast on them.