In book 9 of Plato's Republic, Socrates begins by describing the personal defects of the tyrant and contrasting these with the attributes of the just man. The tyrant has no control over his appetites. Although he wants to enslave all those around him, he is himself a slave to his desires. The just man's appetites are governed by his reason, meaning that he is happier than the tyrant, whatever his material circumstances.

The three parts of the soul—reason, spirit, and appetite—correspond to three types of man. The just man is governed by reason in his love of knowledge, while the timocrat, in his desire for glory, is ruled by spirit. The third type of man is controlled by his appetites, and has elements of the oligarch, the democrat, and the tyrant.

Knowledge, glory, and the satisfaction of appetites all bring pleasure, but the just man knows that knowledge is the is the greatest of these, since the others are transient and unstable. To attain true happiness, one must be led by reason. People who are not reasonable themselves should submit to the reason of those who are.