In the Republic crater VI and VII, Plato starts to define the purpose of a philosopher and where can the “cleanest” source of knowledge is found. Through many questions posed by Adeimantus to Socrates, Plato defines philosophers as individuals who have a clear understanding of the divine, but not the best knowledge of it—for knowledge has never been as the most valuable principle for Plato. On the other hand, in other plays by Plato, opinion remains one of the most valuable principles for the definition of a philosopher. Plato also appears to be wanting but not demanding, that philosophers should partake in public affairs for the city’s own benefit. A good guardian should strive to become a philosopher, for that is what defines a perfect guardian.

People define good as something based on the opinions of the majorities and the authorities but frequently, the majorities and the authorities don’t have the right knowledge and opinion about what is good. Good is not opinion but without good there would be no opinion about good. Which relates to the example with the sun. The sun gives the idea of the good but is not the good itself so there must be some external source of judgment and opinion in order to elaborate on the idea of good. The sun is the base of goodness and the only way of reaching good is through hypothesis and constant change in opinion.