Plato and the Tripartition of Soul

In the Republic, Phaedrus, and Timaeus, Socrates holds that the psyche is complex, or has three distinct and semi-autonomous sources of motivation, which he calls the reasoning, spirited, and appetitive parts. While the rational part determines what is best overall and motivates us to pursue it, the spirited and appetitive parts incline us toward different objectives, such as victory, honor, and esteem, or the satisfaction of our desires for food, drink, and sex. While it is obvious that Socrates primarily characterizes and distinguishes the parts in terms of what each desires and pursues, what is less often brought to the fore is that he also characterizes and distinguishes the parts in terms of how they think. More specifically, he claims that the rational part forms its beliefs on the basis of rational calculation, while the spirited and appetitive parts form their beliefs on the basis of how things appear, without scrutinizing those appearances. Socrates’ dual characterization of the parts of the soul raises a question: why does he characterize each part as having the particular desires and cognitive abilities that he does? In general, how do facts about what a part desires relate to facts about how it thinks? In this paper, I suggest an answer to this question, one that I hope sheds light on the nature of the parts of the soul and so on Plato’s theory of tripartition more generally. I conclude by showing that Socrates’ theory bears a notable resemblance to contemporary dual process theories of judgment, according to which we have two distinct processes for forming judgments, one which is broadly akin to reflection and another to intuition.