What does Plato say about the soul?

According to Plato, the soul is like a mini-state in that it contains three parts. Reason's function is to rule, and the spiritual element is to obey reason. The third element, appetite, is to work and obey. Harmony, or true justice, exists when all components behave as they should, subject to reason. Man should have the ability to control each of these elements so that they function as they should, without infringing on each other. Inner peace exists when this is achieved. Man's nature or personality is determined by the dominance and function of each of these three elements. A slave mentality results in lack of inner freedom and causes inner turmoil. This is the individual who can't think for himself.