The Platonic soul consists of three parts which are located in different regions of the body:
- the logos (λογιστικόν), or logistikon, located in the head, is related to reason and regulates the other parts.
- the thymos (θυμοειδές), or thumoeides, located near the chest region, is related to spirit.
- the eros (ἐπιθυμητικόν), or epithumetikon, located in the stomach, is related to one’s desires.
In his treatise the Republic, and also with the chariot allegory in Phaedrus, Plato asserted that the three parts of the psyche also correspond to the three classes of a society (viz. the rulers, the military, and the ordinary citizens). The function of the epithymetikon is to produce and seek pleasure. The function of the logistikon is to gently rule through the love of learning. The function of the thymoeides is to obey the directions of the logistikon while ferociously defending the whole from external invasion and internal disorder.
Whether in a city or an individual, justice (δικαιοσύνη,dikaiosyne) is declared to be the state of the whole in which each part fulfills its function, while temperance is the state of the whole where each part does not attempt to interfere in the functions of the others. Injustice (ἀδικία, adikia) is the contrary state of the whole, often taking the specific form in which the spirited is obedient to the appetitive, while they together either ignore the logical entirely or employ it in their pursuits of pleasure.