A ruler is self-controlled if one’s reason is in charge and the other two parts of the mind do not interfere with the reason. The same is for the state. The rulers rule the state, the soldiers protect the state, and the craftsmen perform their individual trade. The classes should carry out their specific duties and not interfere with one another. To make sure that the classes will act upon their own tasks, Socrates also included this in the noble lie. He will tell the citizens the gods assigned them to their class because they are best suited for that job. The rulers would have gold in them, the soldiers would have silver, and the craftsmen would have iron or bronze. It is, however, possible for them to move from one class to another. This is mentioned because Plato understands that it is possible, for example, for a craftsman’s son to have the abilities to become a soldier or vice versa.
The last virtue is of course justice. Justice can be described as “minding your own business.” The state and the ruler is just when its three classes or parts execute its own duties and do not interfere with each other. Therefore, injustice must be the opposite or as Socrates says, “…it must be a kind of civil war between the three parts, a meddling and doing of another’s work, a rebellion by some part against the whole soul in order to rule it inappropriately (Plato