The parts of soul in the “Republic”
In the Republic Plato claims that the soul has three parts. The purpose of the theory of psychic tripartition is to understand disease and health in the soul in terms of the parts so as to devise a psychotherapy. The Republic only partly fulfills this purpose inasmuch as its theory of the parts is incomplete. A major defect of Plato's theory is that it contains no account either of the structure of the parts or of the framework within which they interact. For we need to understand this structure and this framework in order to have a fuller understanding of psychic health and therapy. In my dissertation I offer an account of the soul's parts that is suggested by the Republic, consistent with it, and illumines it. The key to understanding the parts of the soul is habit. Owing to the stability and persistence of habits, they are relatively independent of the self-conscious “I” of the soul. Habits can nonetheless make the soul act intelligently and therefore as if the “I” were the agent. Consequently, habit causes partially intelligent and personal activities in the soul that either conflict or agree. Habit's capacity to cause such activities suggests that the psychic parts, which according to the Republic also have this capacity, are systems of habits: habits of thinking, of desiring, and of feeling. As systems of habits, the lower psychic parts are precisely habitual residues or images of repeated rational activities. That is to say, the lower psychic parts relate to the rational one as particulars to their form. The fact that the lower parts are the offspring of reason suggests that the three parts are not alien forces condemned forever to conflict with one another, but that they can be reconciled and reintegrated within a harmonious whole. The therapy that yields this harmony is mainly a habituation of the soul into a pattern that resembles the Good; and a major component of this therapy is disciplined attention to images of the Good, the True, and the Beautiful. For we naturally imitate the things to which we attend.
McCombs, Richard Allen, "The parts of soul in the “Republic”" (2000). ETD Collection for Fordham University. AAI9981405.