Plato identifies political justice as harmony in a structured political body. An ideal state consists of three main classes of people: producers, auxiliaries, and the guardians (rulers); a state is just when relations between these three classes are right. Justice is a principle of specialization: a principle that requires that each person fulfils the societal role to which nature fitted him or her, and does not interfere in any other business.
Socrates describes philosophers as "those who love the sight of truth" (475-e). He claims that what makes philosophers different from lovers of sights and sounds is that they apprehend the Forms. While lovers of sights and sounds love beautiful things, they are unable to see the nature of beauty itself. The Philosophers, on the other hand, believe that beauty exists and can see both it and the things it participates in. In order to back up this claim, that only philosophers can have knowledge, Socrates paints a metaphysical and epistemological picture. He divides the concept of knowledge into: what is, what is not and an intermediate between being and not being. This intermediate between knowledge and ignorance is what he defines as an opinion and casts it as a fallible power. Furthermore, knowledge is the strongest infallible power that is set over the "being" or what is. Given that only philosophers can have knowledge, Socrates emphasizes that they are clearly the ones best able to grasp what is good for the state, and so are in the