Plato’s Republic aims to teach us that justice, in itself, is worthwhile, and that it is better to be just than unjust. It is better to be just than unjust for the just person avoids a life of misery, and the just person lives a happy life. It also goes so far as to teach the value of moderation and self-control to citizens of democracy and democracy itself.
In trying to create the argument of why it is better to be just than unjust, Plato first creates an analogy of the state/city to individuals. In the state, there exist different roles or classes. The city contains four virtues which are dispersed amongst the different classes in society. The four virtues consist of wisdom, courage, temperance/moderation, and justice (pg. 94-109) Temperance, or moderation, and justice are universally dispersed amongst everyone in the city; however, courage and wisdom are granted to a select few, particularly the Guardians (pg. 88-96). It is emphasized in Book IV that there are roles in society, and analogous to this, is the individual which also possesses specific roles, or parts. As there are different classes in society that play a specific role, there are different parts in an individual, specifically three, that have a particular purpose: spirit, appetite, and reason (pg. 88-110). Appetite corresponds to the desires, the wants of the individual. Clashing with this is reason and logic that tries to tame these urges. The balance between these two is defined by spirit, which is the character of the individual (pg. 101-109). For a just society, the guardians must be dominant, and as it is with an individual, for it to be just, reason must be dominant over the other parts. A correct balance must be maintained to be just, which leads to the ultimate conclusion of ...