The philosopher king can therefore tell differences of the roles in the city because he/she is wise and are the only people who actually know what justice is, and can therefore watch to make sure the city is run in the proper manner. Because Socrates explains that the properties associated with making justice real are unchanging and the source of all just things, the Philosopher King must understand that individual items are not "justice" but are instead ideas associated with justice and not tangible. .
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The Philosopher King is a good ruler because in actuality they do not even seek to rule, they would prefer to spend their time pursuing knowledge, because of this, they do not rule in their own interest but only for the best interest of the city. They are compelled to rule because of the obligation to the city that has raised them and given them an opportunity to become a guardian, whose raising has included extensive education which requires a debt to be repaid by their servicing the city as their ruler.
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The education of the Philosopher King is a very important factor. The system that is set up will nurture the natural instincts of the Philosopher King and there fore is built around all of the attributes that are required to be the absolute ruler. There are four virtues found to be important for the Philosopher King to posses, the education systems nurtures these virtues and brings them to the forefront and also eliminates anyone who does not withstand the testing of each virtue. The virtues being: Wisdom, this is revealed by their unfaltering love of truth and their continual demonstration of the spirit of truthfulness; Moderation is proven by their disregard for physical pleasures instead they delight in intellectual discourse; Courage is shown by their honor and prestige of soldiers, along with their understanding that death is inconsequential because they know that the essence of things, including human souls are eternal; Justice is shown by their lack of concern over petty matters, their integrity and their understanding of the forms, what the many have in common.
