The Tripartite Theory of the Soul

Desire and Belief in the Parts of the Soul

The Tripartite Theory of the Soul marks a change in Plato's thinking about the control a human being exercises over his actions and thus his life. In the Republic, Socrates departs from the position in the Protagoras. The soul, the Republic, consists in more than reason. It has two parts that do not engage in the thinking that characterizes reason. The soul is thus tripartite:

All three parts of the soul can give rise to desires. The desire of reason stems from beliefs about what is good and what is bad. This, however, is not true of the appetite and spirit. The desires of these parts do not depend on any beliefs about what is good and what is bad.

Now it is possible for someone to act contrary to his knowledge of what is good and what is bad. This has consequences for how to understand the competency involved in living the good life. The parts of the soul must have their proper organization. Reason must lead the way.

An Argument from Opposite Motions


"It is obvious that the same thing will never do or suffer (ποιεῖν ἢ πάσχειν) opposites in the same respect in relation to the same thing and at the same time. So that if ever we find this happening we shall know that it was not the same thing but a plurality" (Republic IV.436b).

  "Are we to say, then, that some men sometimes though thirsty refuse to drink?
  We are indeed, many and often.
  What then, should one affirm about them? Is it not that there is something in the soul that bids them drink and a something that forbids, a different something that masters that which bids?
  I think so.
  And is it not the fact that that which inhibits such actions arises when it arises from the calculations of reason (λογισμοῦ), but the impulses which draw and drag come through affections and diseases?
  Apparently.
  Not unreasonably, shall we claim that they are two and different from one another, naming that in the soul whereby it reckons and reasons the reasoning part (λογιστικὸν) and that with which it loves, hungers, thirsts, and feels the flutter and titillation of other desires, the unreasoning (ἀλόγιστόν) and appetitive part (ἐπιθυμητικόν)—companion of various repletions and pleasures.
  It would not be unreasonable but quite natural, Socrates" (Republic IV.439c).

  "Of the spirit (θυμοῦ), that with which we feel anger (θυμούμεθα), is it a third, or would it be the same as these [we have distinguished]?
  Perhaps with one of these, the appetitive.
  But I once heard a story which I believe, that Leontius the son of Aglaion, on his way up from the Peiraeus under the outer side of the northern wall, becoming aware of dead bodies that lay at the place of public execution at the same time felt a desire to see them and a repugnance and aversion, and that for a time he resisted and veiled his head, but overpowered in despite of all by his desire, with wide staring eyes he rushed up to the corpses and cried, ‘There, you wretches, take your fill of the fine spectacle!'
  I too have heard the story.
  Yet, surely, this anecdote signifies that the principle of anger sometimes fights against desires as an alien thing against an alien.
  Yes, it does, Socrates" (Republic IV.439e).

  "So in the soul, there is the spirited part (θυμοειδές), which is the helper of reason by nature (ἐπίκουρον ὂντῷ λογιστικῷ φύσει) unless it is corrupted by bad nurture?
  We have to assume it as a third, Socrates.
  Yes, provided it shall have been shown to be something different from the rational, as it has been shown to be other than the appetitive.
  That is not hard to be shown, Socrates. For that much one can see in children, that they are from their very birth chock-full of rage and high spirit, but as for reason, some of them, to my thinking, never participate in it, and the majority quite late.
  Yes, by heaven, excellently said, and further, one could see in animals that what you say is true" (Republic IV.441a).

  "The same magnitude, I presume, viewed from near and from far does not appear equal.
  Why, no.
  "And the same things appear bent and straight to those who view them in water and out, or concave and convex, owing to similar errors of vision about colors, and there is obviously every confusion of this sort in our souls. And so scene-painting in its exploitation of this weakness of our nature falls nothing short of witchcraft, and so do jugglery and many other such contrivances.
  True.
  And have not measuring and numbering and weighing proved to be most gracious aids to prevent the domination in our soul of the apparently greater or less or more or heavier, and to give the control to that which has reckoned and numbered or even weighed?
  Certainly.
  But this surely would be the function of the part of the soul that reasons and calculates (λογιστικοῦ).
  Why, yes, of that.
   And sometimes, when this has measured and declares that certain things are larger or that some are smaller than the others or equal, the opposite appears (φαίνεται) at the same time.
  Yes.
  And did we not say it is impossible for the same thing at one time to believe (δοξάζειν) opposites about the same thing?
  And we were right in affirming that.
  The part of the soul, then, that opines (δοξάζον) in contradiction of measurement could not be the same with that which conforms to it.
  Why, no.
   Further, that which puts its trust in measurement and reckoning must be the best part of the soul.
  Surely.
   That which opposes it must belong to the inferior parts of the soul.
  Necessarily.
  This, then, was what I wished to have agreed upon when I said that poetry, and in general the mimetic art, produces a product that is far removed from truth in the accomplishment of its task, and associates with the part in us that is remote from intelligence (φρονήσεως), and is its companion and friend for no sound and true purpose" (Republic X.602c).

The Müller-Lyer Illusion.
The second horizontal line appears longer than than the first, but in fact the two lines are the same in length.

Müller-Lyer Illusion

"Things about which we have at the same time a true belief may have a false appearance; for instance the sun appears to measure a foot across, but we are convinced that it is greater than the inhabited globe..." (Aristotle, On the Soul III.428b).
To begin to understand the Tripartite Theory of the Soul, consider an example Socrates gives to establish the existence of reason and appetite. In this example, someone is thirsty but refuses to drink. Socrates thinks there are contrary motivations in play here. One stems from appetite. This, if reason were not in control, gives rise to a desire that would move the person to take steps to drink. Reason, however, in the example, is in control. It has the belief that drinking is bad in the circumstances and thus desires not to drink. This overrules the appetite.

Socrates argues for this understanding in terms of a principle about opposite motions. In this argument, he conceives of the contrary motivations as opposite motions. The core idea, it seems, is that desires function in the soul to move us and that desires are thus motions.

In the example, someone who is thirsty is moving toward drinking. Because he reasons that drinking is bad, he is also moving away from drinking. Given the principle about opposite motions, the contrary motivations belong to different parts of the soul. The appetitive part of the soul "bids" him to drink. The reasoning part of the soul "forbids" to drink.

In addition to the existence of reason and appetite, Socrates argues for a third part of the soul.

He uses the case of Leontius to show that anger, which is in some part of the soul, sometimes conflicts with the appetitive part. This part could be reason, but Glaucon observes that children have spirit but "as for reason, some of them... never participate in it, and the majority quite late." So since children get angry with themselves, and reason does not play a controlling role in their actions, it follows that there is a third part in the soul. This is the spirited part.

Another Argument from Opposite Motions

Socrates gives another example too to show that reason is one of the parts of the soul.

In his discussion of imitation in Book X, Socrates notes that sometimes although reason "has measured and declares that certain things are larger or that some are smaller than the others or equal, the opposite appears (φαίνεται) to it at the same time."

Suppose, then, that lines are arranged so that one appears longer than the other, that measurement reveals they are equal in length, and that after measurement reveals they are equal, the appearance persists because the arrangement of the lines tricks the eyes.

The argument for reason seems to depend on the premise that accepting and rejecting are opposite motions (Republic IV.437b). There is a motion of accepting that one line is longer than the other, and there is a motion of rejecting that the lines are unequal. These motions are opposite. So, given the principle of opposites, they are in different parts of the soul.

So the "inferior parts of the soul" can have "beliefs" (δόξαι) These beliefs are representations the senses, memory, and imagination produce of sensible reality. They are not thoughts about nonsensible reality produced in reason by questioning and other methods.

The Beliefs that Give Rise to Desires

Appetite and spirit can move a human being to action. For this to happen, it seems that these parts of the soul must have states that give rise to desires.

What are these states? Are they beliefs?

One possibility is that they are beliefs, but unlike the desires of reason, the desires in appetite and spirit do not stem from beliefs about what is good and bad. The desires in the appetite stem from beliefs about pleasure. The desires in spirit stem from beliefs about honor.

There is no passage in which Socrates says exactly this about desire and the parts of the soul, but he does seem to think that appetite and spirit have beliefs that give rise to desires.

Some of these beliefs may be innate, but others human beings develop in response to their experiences. These beliefs can guide their lives. So, for example, their beliefs about what experiences are pleasurable and painful can give rise to desires for the pleasurable experiences and aversions to painful experiences. This, it seems, is what happens in the appetite.

The Harmonious Organization of the Parts

There are different possible organizations among the three parts of the soul. In the proper organization, reason rules, spirit is reason's ally, and appetite is under control. When the parts are so organized, they are in "harmony." Further, since reason knows what is good and what is bad, a human being whose soul is in harmony acts for the sake of the good.

  "Does it not belong to the reasoning part to rule, since it is wise and exercises foresight on behalf of the whole soul, and for the spirited part to obey and be its ally?
  Assuredly, Socrates" (Republic IV.441e).

How the Parts Come Together to Produce Action

It is not easy to see how the three parts come together so that there is action.

Consider Socrates' example that "some men sometimes though thirsty refuse to drink." Even in the case in which they do not drink, there is still something in their souls that "bids" them to drink. This something is the appetite, but how does it "bid" them to drink.

There is the temptation to take the "biding" to be a desire and to think that the strongest desire is the one that leads to action, This, though, assumes that we know what makes one desire stronger than another, and it is unclear that the Tripartite Theory says anything about this.

Maybe instead the "biding" consists in the fact that the appetite believes being thirsty is painful and drinking when thirsty is pleasant. If appetite were in control, it would give rise to a desire to drink. Reason, however, is in control. So appetite is frustrated. This frustration feels to us as if something is pushing us to act against our belief about what is best in the circumstances.

Even if something along these lines is the right way to understand the Tripartite Theory, we still need a clearer understanding of what it is for a part of the soul to be in control.

How Reason Changes Appetite and Spirit

Given that it "belongs to the reasoning part to rule" the other two parts of the soul (Republic IV.441e4), it seems that there must be some way or ways for reason to give "orders" to these parts to cause them to bring their behavior in line with what reason wishes.

In the Republic, however, because of the extensive education and system of censorship, it seems this is unnecessary. The society is organized so that when a person is young the appetitive and spirited part of his soul become habituated to acting in ways reason deems to be correct.

  "What, then, is our education (παιδεία)? Or is it hard to find a better than that which long time has discovered? Which is, I suppose, gymnastics (γυμναστική) for the body and for the soul music (μουσική).
  It is.
  And shall we not begin education in music earlier than in gymnastics?
  Of course.
  And under music you include tales, do you not?
  I do" (Republic II.376e).

The education in "music" and "gymnastics" is traditional. In the Republic, Socrates implements this education in a way he takes to avoid the mistakes of the past.



"For I fancy that you have long observed how men do not experience fear or distress when they have been rationally persuaded that evil is present or is approaching, but they do so when they get an image (φαντασίας) of those same things. For how could you stir the irrational by means of reason, unless you place before it a picture, as it were, that resembles a picture perceived by the eye? Thus some persons fall victim to desire as a result of a verbal account, and when given a vivid injunction to flee the charging lion, even though they have not seen it they are afraid" (Galen quoting Posidonius, The Doctrines of Plato and Hippocrates V.24-27).
In the Timaeus, though, which is traditionally a late dialogue, there is the suggestion that reason can change the appetite by enticing it with "images and appearances" (εἰδώλων καὶ φαντασμάτων) to cause pain or pleasure (71a) and thus to change its desires.

To understand how this might work, consider a compulsive behavior, such as smoking (to use a modern example). The appetite may form a habitual desire to smoke because smoking has been pleasurable in the past. Over time, this habit may become very strong. If, at some point, reason discovers that smoking is bad, this alone will not be enough to prevent the appetite from issuing the desire and hence from moving the person to smoke. To break the habit of acting on the desire that arises when one sees an opportunity to smoke, reason can form beliefs that imagine the painful consequences of smoking so that the appetite associates the pain depicted in these images with smoking and thus causes the appetite to lessen the strength of its liking for smoking.




Perseus Digital Library:
Plato's Republic, Theaetetus, Timaeus, Philebus

Henry George Liddell, Robert Scott, A Greek-English Lexicon:
βούλησις, boulēsis, noun, "willing"
Plato uses ἐπιθυμητικός and θυμοειδής as adjectives corresponding to the επιθυμία and the θυμός. επιθυμία, epithymia, noun, "appetite"
ἐπιθυμητικός, epithymētikos, adjective, "desiring, coveting, lusting after"
θυμοειδής, thymoeidēs, adjective, "high-spirited"
θυμός, thymos, noun, "strong feeling or passion"
λογιστικός, logistikos, adjective, "skilled or practiced in cacluating"
μουσική, mousikē, noun, "art over which the Muses preside"
ὄρεξις, orexis, noun, "appetency, conation, including ἐπιθυμία, θυμός, βούλησις"




"There is reason to believe that [the historical] Socrates thought that "...an irrational part of the soul with its own needs and demands..." What is this? A part of the soul that does not engage in reasoning. In the tripartite soul, spirit and appetite are the "irrational" parts. They are parts without reason.

What does it mean to say that "[i]f reason knew the truth, it could never get confused in this way"? The answer, it seems, is that reason knows the truth when all its beliefs are true. In this case, no argument for a false conclusion whose premises are taken from the beliefs of reason is valid.
there is no such thing as acting against one's own better judgment. What does happen is that reason in certain circumstances gets confused and, instead of holding on to its better judgment, follows some other judgment. If reason knew the truth, it could never get confused in this way. Thus, according to Socrates, such cases reveal nothing but a failure of reason which in its weakness does not hold on to the true belief, but accepts a false one and acts on it. Plato, Aristotle, and their followers, on the other hand, believed that such cases could not be explained as purely intellectual failures, that one had to assume that besides reason there is an irrational part of the soul with its own needs and demands which may conflict with the demands of reason and which may move us to act against the dictates of reason, if reason has not managed to bring the irrational part of the soul firmly under its control" (Michael Frede, "The Stoic Doctrine of the Affections of the Soul," 96. Norms of Nature, 93-100).




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