Plato is primarily concerned with knowing the good. In the Republic, Plato intends to define justice and describes an elaborate city-state setup with the goal of being a just city. A guardian class of philosophers rules in Plato's city, because these are the only people who can know the good. Everyone else's role in the city is to do their work to support the city so that the guardians are able to philosophize. Aristotle does not follow this concept of knowing the good, but instead advocates doing good. In Aristotle's city, people should do the best they can at their craft so they can flourish and be good. This concept carries over to the politics of the city, as political scientists should do good by making just laws that allow the citizens to do good through just habituation. Because Plato is primarily concerned with knowing the good, while Aristotle is primarily concerned with being good, I will show that they have contrasting political theories, and that Aristotle's political theory is more realistic and obtainable than Plato's political theory.
Although Plato never says what the good actually is, he does state that only philosophers can know what the good is (). Plato offers two analogies as to why philosophers are capable of ruling, and why they should rule. The first is the analogy of a ship. On this ship, the captain is removed and the sailors fight for control of the ship. The sailors who take power of the ship are not the best fit to navigate, but they are the best at practicing politics and building a following of people. The sailors who are best fit to navigate do not practice politics and are not given the opportunity to rule. These sailors are the philosophers of the world; they are the best at leading a society, but because they do not practice politics, they will never rise to power.
The parable of the cave is the second analogy for philosophers. Plato describes a cave in which people are locked in a...