Glaucon breaks all good things into three classes. The first kinds, we desire for their own sake, like the experience of harmless pleasure. The second, we want only for the value they bring, though they may be onerous, like exercise or medicine. The third class comprises things we desire for their own sake and the value they offer, like knowledge and health. Glaucon argues that justice belongs to the second class of good: it's a burden that nevertheless brings rewards. The only reason anyone conducts themselves virtuously, he reasons, is due to external influences. So it's appearing—not actually being—virtuous that matters. Socrates, as written by Plato, disagrees, countering that justice belongs to the third class of good, offering both extrinsic and intrinsic benefits. Socrates argues that the human soul has three parts: reason, spirit, and appetite. Reason guides an individual to truth and knowledge, and is influenced by either spirit or appetite. Spirit is righteous, ambitious, and the source of bold action, while appetite consists of baser, bodily desires. To Socrates, the philosopher is led by reason, and their spirit keeps their appetite in check, making them the most just and the happiest. Even without consequences for self-serving wrongdoings, they wouldn't commit them. Meanwhile, the tyrant succumbs to appetite and acts unjustly.