The Tripartite Soul

In the Republic, Plato argues that the soul has three parts. He reaches the division through conflict: a thirsty man who refuses to drink shows two things pulling against each other, so the soul cannot be a single thing. The parts are reason (logistikon), which seeks truth and ought to rule; spirit (thymos), the seat of honor, anger, and ambition, the natural ally of reason; and appetite (epithymia), the unruly mass of bodily desires for food, drink, and sex.

Justice as right order

Justice in the individual, Plato argues, is the right ordering of these parts — reason governing with wisdom, spirit enforcing its decisions with courage, appetite obeying — each doing its own work and not usurping another's. This mirrors the just city with its rulers, guardians, and producers, and vice is simply the rule of a lower part over the whole, as in the tyrannical soul ruled by its basest desires.

In myth and tradition

The charioteer myth of the Phaedrus gives the same structure mythic form: reason drives a pair of winged horses, one noble (spirit) and one unruly (appetite). The threefold soul became the foundation of Platonist moral psychology, though later thinkers debated whether the lower parts survive death or fall away as the soul ascends, and Plotinus set the whole embodied soul beneath a higher self that never wholly descends.