Plato was one of the first to develop the concept of a political utopia. In The Republic, he attempts to define justice by using the character of Socrates in a debate. Plato then continues to outline the guidelines for a just society. Plato's utopia appears, at first, to be an excellent idea. However, after further examination, his perfect society is less than ideal. Several flaws are obvious when considering Plato's vision from a contemporary perspective. In addition, in The Politics Aristotle critiques Plato's ideal city and offers his own model for society. .
Plato tries to define justice by implementing the Socratic method of oral teaching through dialogue. He uses Socrates as the protagonist who poses the question: What is justice? Socrates then proceeds to eliminate his opponents by attacking the weaknesses and exposing the limitations of their arguments. By refuting the flawed logic of his opponents, Socrates shows what is not justice.
Plato assigns characters to Socrates" dialogue partners who argue differing opinions. The first is Cephalus, who states that justice is to return what you have taken. The main critique of Cephalus" argument is that his proposal is instrumental not intrinsic. The next challenger is Polemarchus. His describes justice as helping your friends and hurting your enemies. He advocates proportionality, to treat others how they deserve to be treated. Plato simply rebuts that we are unable to fairly judge our friends and our enemies because we are biased. The next person that Socrates responds to is Thrasymachus who declares that there in no justice; he says that those in power dictate justice and that justice changes with regimes. The idea that justice is in the interest of the stronger is the most convincing that Socrates encounters. Socrates does not have a strong defense to this argument. Thrasymachus is a precursor for later political theorists.