In the Book IV of Plato’s The Republic, Plato has Socrates make a series of arguments that attempt to establish that soul has three parts. Plato’s theory of soul is one of the earliest discussions on human psychology in the history of Western philosophy. This piece discusses and investigates the plausibility of Plato’s argument for the tripartite soul, i.e. that human soul has reason, spirit and appetite as three separate entities with different functions to perform for a just soul. It won’t discuss the question of justice in soul or the city, nor it will address the whole series of arguments for the tripartite soul in the Book IV. It only scrutinizes Plato’s argument for how ‘desiring and being averse are opposites’ in making the statement that there is a rational as well as an appetitive part in soul. It attempts to contend that Plato’s argument for the tripartite soul fail and proposes how an alternative theory of soul is possible.
Plato begins his analysis of the structure of the soul by propounding a general principle to the effect that opposite actions, emotions or mental states cannot respond to the same object and at the same time. To be precise, Plato maintains that it is “obvious” that the same object will not be willing to do or to undergo opposites in the same part of itself, in relation to the same thing, and at the same time. Plato maintains this to be almost commonsensical and evident. However, in actuality, Plato realizes that we find the opposite in the soul, i.e. it happens in our soul that we desire to something and at the same time averse in doing the same thing. Plato gives the analogy of a thirsty person –who is very thirty and wants to drink (tea, coke or vodka) to quench his thirst, but at the same he refuses to drink for various reasons. Then, the implication is, as Plato maintains, that this observation of phenomenon of pair opposites performing both assent and dissent in our soul at the same time must necessitate the existence of two entities in the soul –performing different functions –reason for rational calculation of our actions and appetite for simple satisfaction of sensual desires. To present Plato’s argument in simple terms:
Premise 1: Opposite actions, affections and states cannot happen to the same thing and at the same time, i.e. the same thing will not undergo opposite states at the same time.
Premise 2: Desiring and being averse are opposites.
Conclusion 1: Desiring and being averse at the same thing are opposites in the relation to the same object or activity.
Premise 3: It happens that the soul desires as well as averse at the same object or activity at the same time.
Conclusion 2: It follows that the human soul should at least include two distinct parts, namely a part that desires (appetite) and another that rejects the desires and regulate desires (rational).
I call this the first argument, because this is the argument he makes in an attempt to establish first that there are two distinct parts in the human soul. I think and would argue that it is a perfectly valid argument, but not a cogent and sound one.
First, the truth of the premise (1) is clearly not established. This principle of opposites which states that opposite actions and affections cannot happen at the same time in relation to the same object or activity may seem plausible from the standpoint of physical laws. For instance, an object cannot be both hot and cold at the same time. The problem, however, is that Plato derives his conclusion (2) with the assumption that this principle of opposites also applies to the human soul. Plato attempts from derive the proposition that there are two distinct entities in soul because one entity cannot perform such opposing activities at the same time. Therefore, it follows that there are two distinct entities performing these opposing activities. Plato simply assumes that one entity cannot perform two opposing activities at the same time in the soul, just like what seems to be the case in the physical world. For the first crime, Plato seems to equate physical activities to mental states or mental activities like desiring something. Second, Plato fails to realize that the conflict of desires doesn’t necessarily dictate a commander of desires –reason as an entity outside desires. I argue that reason is just another kind of desire. It is a calculated desire because it desires a desire to achieve a certain desire. For instance, the person Z restrains from eating ice-cream even though s/he really likes ice-cream, especially, right after dinner, but Z suppresses his or her ice-cream desire for the higher desire to be healthy. Therefore, I maintain that the human soul is consisting of various desires and sometimes these desires come into conflict.
To conclude, with the assumption that he has established that are two distinct parts in the human soul, Plato proceeds in inventing another entity in the soul –the spirited part. Realizing the difficulty of producing a third part, he takes the spirit part to be ‘a natural ally of reason’ and almost, disingenuously, maintains that the spirit is a third part. I won’t analyze the full argument here because as I have shown, there aren’t any parts –there are only desires in the mind and these desires manifest in different mental states.
Cooper, John M. (1997) Plato: Complete Works, Hackett Publishing Company, Indianapolis.