The Tripartite Theory of the Soul

Desire and Belief in the Parts of the Soul

In the Republic, Plato has Socrates argue for what has come to be known as The Tripartite Theory of the Soul. This theory is inconsistent with the position in the Protagoras that the soul is reason and that desires stem from beliefs about what is good and what is bad.

This change in thinking about the soul has consequences. One of difficulties we encountered in trying to understand Socrates is what he thought goes on the soul of someone who is living the good life. We have this same problem, but now the soul is more than reason.

The Soul has Rational and Nonrational Parts

In the Republic, the soul is tripartite. One part is reason, but now the soul also had two other parts that do not engage in the thinking that characterizes reason. It is traditional to describe this fact about the soul by saying that it has one "rational" part and two "nonrational" parts.

 The rational part is "reason." The two nonrational parts are "spirit" and "appetite."

All three parts of the soul can give rise to desires. The desires 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 of appetite and spirit do not depend on any beliefs about what is good and what is bad.

As with the parts of the soul, it is traditional to use "rational" and "nonrational" to describe these desires. The desires of reason are rational. The desires of spirit and appetite are nonrational.

Conflict in Motivation in the Soul

Plato comes to the Tripartite Theory of the Soul in an effort to understand the phenomenon of being overcome by pleasure. In the Protagoras, Socrates says that someone is not a "master of himself" when this happens. Plato thinks this requires that the soul is more than reason.

  "Yet is not the expression mastery of oneself (κρείττω αὑτοῦ) ridiculous? He who is stronger than himself would also presumably be weaker than himself, and he who is weaker than himself, stronger, since the same person is induced by all these expressions.
  Of course, Socrates.
  Nonetheless, the expression seems to me to mean that, in the soul there is a better part and a worse part and that, whenever the naturally better part is in control of the worse, this is expressed with the words mastery of oneself. This, at any rate, is a term of praise. But when the smaller and better part is overpowered by the larger part, because of bad upbringing or bad company, this is called yielding to one's self (ἥττω ἑαυτοῦ)" (Republic IV.430e).

An Argument from Opposites

"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).

  "Thirst itself is in its nature only for drink itself.
  Absolutely.
  Hence the soul of the thirsty person, insofar as he is thirsty, is does not wish anything else but to drink, and it wants this and is impelled toward it.
  Clearly" (Republic IV.439b).

  "Are we to say 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 to drink and a something that forbids, a different something that masters (κρατοῦν) 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 gets passionately excited by 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). Cf. Phaedo 94b.

  "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 knew a desire to see them and at the same time was disgusted and turned away. For a time he struggled and veiled his head, but finally, overpowered (κρατούμενος) by his desire, he pushed his eyes wide open, 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 anger sometimes fights against desires, as one thing against another.
  Yes, it does, Socrates" (Republic IV.439e).

   "And don’t we often notice on other occasions that when desires force (βιάζωνταί) someone contrary to his rational calculation, he reproaches himself and feels anger at the thing in him that is doing the forcing; and just as if there were two warring factions, such a person’s spirit becomes the ally of his reason? But spirit partnering the appetites to do what reason has decided should not be done—I do not imagine you would say that you had ever seen that, either in yourself or in anyone else.
   No, by Zeus, I would not" (Republic IV.440a).

  "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
Socrates tries to establish the existence of reason and appetite in the soul as part of an explanation of what is going on when someone is thirsty but refuses to drink. Socrates thinks that the person has opposite motivations: one that stems from appetite and another that stems from reason.

Because the motivation to drink and the motivation not to drink are opposites, Socrates thinks that they must belong to different parts of the soul. The appetitive part of the soul "bids" the person to drink, and the reasoning part of the soul "forbids" him to drink.

Socrates thinks that the existence of opposite motivations requires the soul to have parts because the soul moves the body and that it can simultaneously move it in opposite ways only if one part is moving the body in one way and another part is moving it in the other way.

In addition to appetite and reason, Socrates also 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 behavior, it follows that there is a third part in the soul. This is the spirited part.

Another Argument for Reason

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, for example, 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.

This argument for reason depends on the premise that accepting and rejecting are opposites (Republic IV.437b). The soul rejects and accepts that the lines are equal in length. So, given the principle about opposites, this happens in different parts of the soul.

This, it seems, requires that the "inferior parts of the soul" can have "beliefs" (δόξαι).

How are these beliefs different from the beliefs of reason?

The example suggests that beliefs in the nonrational parts of the soul are representations produced by the senses, memory, and imagination. They are not beliefs about nonsensible reality produced in reason by measurement, questioning, and other such methods.

Reason Should be the Ruler in the Soul

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.

  "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).

This can seem straightforward enough, but is not easy to see the mechanism according to which the motivations in the three parts of the soul result in a specific action.

Consider Socrates' example in which "some men sometimes though thirsty refuse to drink." They do not drink, but the appetite in their souls still "bids" them to drink.

Why does this "bidding" not result in action?

The answer, it seems, is that reason is in control. This answer, however, is not very informative. It does not explain why the "forbidding" in reason wins over the "bidding" in appetite.

The same problem arises for Socrates' Leontius example. In this case, although reason "forbids" looking, the "bidding" in the appetite results in looking.

Why does this "bidding" result in action?

The answer, it seems, is that appetite is in control. This answer, again, is not very informative. It does not explain why the "bidding" in appetite wins over the "forbidding" in reason.

How Reason Becomes the Ruler in the Soul



"[I]n children the first childish sensations are pleasure and pain, and that it is in these first that virtue and vice come to the soul; but as to wisdom and settled true opinions, a man is lucky if they come to him even in old age and; he that is possessed of these blessings, and all that they comprise, is indeed a perfect man. I term education, then, that in which virtue first comes to children. When pleasure and love, and pain and hatred, spring up rightly in the souls of those who are unable as yet to grasp the reason; and when, after grasping reason, they consent thereunto that they have been rightly trained in fitting practices:—this consent, viewed as a whole, is virtue, while the part of it that is rightly trained in respect of pleasures and pains, so as to hate what ought to be hated, right from the beginning up to the very end, and to love what ought to be loved, if you were to mark this part off in your account and call it education, you would be giving it, in my opinion, its right name" (Laws II.653a).

Cf. Laws II.659d; Aristotle, Nicomachean Ethics II.3.1104b.
Although it is not clear how reason wins when there is contrary motivation in the appetite, Socrates does explain how reason comes to be in control and thus the ruler in the soul. This happens in education that trains the appetitive and spirited part of the soul to make them exist in "harmony" with reason and its beliefs about what is good and what is bad.

Education is a matter of training children so that they form the correct motivations. Because they are "especially malleable and best take on whatever pattern one wishes to impress on" them, they are not "to hear any old stories made up by just anyone, then, and to take beliefs into their souls that are, for the most part, the opposite of the ones we think they should hold when they are grown up" (Republic II.377b). Impressions in children are hard to change. So "the first stories they hear about virtue should be the best ones for them to hear" (Republic II.378e).

Stories about virtue mould the spirited part of the soul to like and dislike the appropriate things. Together with training for the appetitive, this ensures that reason is the ruler in the soul.

"Since he feels distaste correctly, he will praise fine things, be pleased by them, take them into his soul, and, through being nourished by them, become fine and good. What is ugly or shameful, on the other hand, he will correctly condemn and hate while he is still young, before he is able to grasp the reason And, because he has been so trained, he will welcome the reason when it comes and recognize it easily because of its kinship with himself" (Republic III.401e).




Perseus Digital Library

Plato's Republic, Theaetetus, Timaeus, Philebus

Henry George Liddell, Robert Scott, A Greek-English Lexicon

βούλησις, boulēsis, noun, "willing"
επιθυμία, epithymia, noun, "appetite"
ἐπιθυμητικός, epithymētikos, adjective, "desiring, coveting, lusting after"

Plato uses ἐπιθυμητικός and θυμοειδής as adjectives corresponding to the επιθυμία and the θυμός.

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"
πρόνοια, pronoia, noun, "foresight," opposed to επιθυμία




"There is reason to believe that Socrates thought that there is no such thing as acting against one's own better judgment [as in the Protagoras, for example, the many think happens when someone is overcome by pleasure]. ... 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: Studies in Hellenistic Ethics, 93-100. Cambridge University Press, 1986).

"We have a tendency, or at least for a very long time have had a tendency, to understand Plato and Aristotle as if they claimed that it were the task of reason to provide us with the right beliefs or, better still, knowledge and understanding, while the task of the nonrational part of the soul is to provide us with the desires to motivate us to act virtuously in light of the knowledge and understanding provided by reason. But ... this is not the view of Plato and Aristotle. According to them, it is not the task of reason to provide us only with the appropriate knowledge and understanding; it is also its task to provide us with the appropriate desires. To act virtuously is to act from choice, and to act from choice is to act on a desire of reason. The cognitive and the desiderative or conative aspects of reason are so intimately linked that we may wonder whether in fact we should distinguish, as I did earlier, between the belief of reason that it is a good thing to act in a certain way and the desire of reason which this belief gives rise to, or whether, instead, we should not just say that we are motivated by the belief that it is a good thing to act in this way, recognizing this as a special kind of belief which can motivate us, just as the Stoics think that desires are nothing but a special kind of belief. ... Further, the modern scholarly view, that according to Plato and Aristotle, reason provides the beliefs and the nonrational part of the soul provides the motivating desires, is grossly inadequate in that it overlooks their view that, just as reason has a desiderative aspect, so the nonrational part of the soul and its desires have a cognitive aspect. ... We shall understand this better if we take into account that Plato and Aristotle distinguish three forms of desire, corresponding to the three different parts of the soul, and also, at least sometimes, seem to assume that each of these forms of desire has a natural range of objects which it naturally latches on to. Appetite aims at pleasant things, which give bodily satisfaction; spirit (θυμός) aims at honorable things; and reason aims at good things. ... When we see a delicious piece of cake, it will be appetite which has the impression that it would be very pleasant to have this piece of cake. Since appetite lacks reason, it has no critical distance from its impression. For it to have this impression amounts to the same as its having this belief. Similarly, the spirited part (θυμός), being sensitive to what is honorable, will have the impression that it would be shameful to have yet another piece of cake" (Michael Frede, A Free Will. Origins of the Notion in Ancient Thought, 49-51. University of California Press, 2011).




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