Plato's Republic is the Ideally Just Society

MayCaesar

Plato was a philosopher, and philosophers prefer order over chaos strongly, because this is how raw logic works: it is perfectly ordered. However, human organisms are not as ordered, and such strict hierarchical systems tend to fail due to the natural difference between individuals and the unpredictability of their actions.

Is Plato's system just? Depending on the used definition of justice, it may or may not be. A principal problem I see with the justice in it is that it is, by design, a class-based society, and that immediately implies that a part of how people are treated is based on their class and not on their merit, individual qualities and so on. This is unjust towards those who work hard to improve their merit or individual qualities, but remain restricted by the limitations of their class. 

Is Plato's system effective? I think that, just as in case of communism, it can only be built through extreme violence (as highly ordered systems are not natural, and many individuals will always rebel against the order) and maintained through totalitarian means. It has enforced Darwinist elements in it (people's roles are defined by the nature, not by the people's own preferences), which is known to not work very well as a foundation of a political system. I do not think Plato's Republic is viable; the closest we have to the Plato's Republic is the Indian caste system, and that system does not look very appealing to me personally.

What is interesting, however, is how Plato's Republic has certain elements similar to the modern principle of checks and balances. In Plato's design, the three classes have the duty to not let the other classes step out of their intended role. I have not studied it in detail, but it is very likely that the Founding Fathers studied Plato's works (they were particularly interested in the Greek and Roman political designs, so they could not miss them) and found inspiration in his ideas on the Republic.