Plato’s strategy is to first explain the concept of political justice and then that of individual justice. According to Socrates, The State is divided into three specific classes: Artisans, Soldiers, and Rulers. Artisans include members of the community whose function is to satisfy the material needs of the masses. They include businessmen, workers, and farmers. Solders consist of those whose function is to defend the community and therefore must possess the virtue of courage. Lastly, rulers are individuals whose function is to govern (Narveson, L4). They are said to possess the virtue of wisdom and they must not seek the fame of being a ruler. Artisans and Soldiers are required to be obedient to the Rulers. Socrates emphasizes that justice consists of having each class perform its own business and not interfere in the functions of its neighbours. Essentially, justice is a principle of specialization: a principle that requires each person to fulfill their societal role to which nature fitted him. In other words, a harmony amongst the classes.
Closer to the end of Book IV, Plato attempts to show that individual justice mirrors political justice. Socrates argues that humans often find themselves internally divided, being both impelled in a certain direction and simultaneously resisting this impulse. Socrates forms his theory of the soul on the principle that the same thing cannot go in two opposite directions at once and therefore, there must be different parts of the soul. Fundamentally, Socrates argues that the soul is also divided into three separate parts or classes. The first, is the “lowest” and includes the appetite, whose function is to satisfy bodily needs. It is the part of the soul that can be hungry for immoral gratification and has no rational consciousness in its desires. The second, or the “middle” encompasses the spirited element of the soul whose function is to control and tame the appetites. This part enables the soul to differentiate between good and bad. The “highest” is that of reason, whose function is to rule over the soul as a whole (Narveson, L4). The spirit naturally, if it has not been corrupted by bad upbringing, allies with the rational part.
Socrates sketches a psychological portrait of the tyrant in order to prove that injustice tortures a mans psyche, whereas a just soul is a happy, untroubled and calm (Plato, p.12). Based on this view, according to Plato, psychological health is detriment of justice. Socrates inferences suggest that internal peace is required if one is to get anything done. The psychologically unstable individual suffers from internal turmoil and conflict, thus reducing his efficiency. Personally, I disagree with this explanation of justice. I do not believe that an individual whose soul is “orderly” and “harmonious” in the sense that different parts of it are not going off in different directions, is always someone who is just in the sense of paying his debts, refraining from murder, and so on. It could be said that the unjust man’s soul will not be in harmony because his conscience will bother him. However, this is to say that he will recognize