The Tripartite Theory of the Soul

Some Desires are Not Beliefs about What is Good or What is Bad

In the Republic, Socrates argues that the thinking in the soul consists in more than reasoning. He argues there are two parts that do not engage in reasoning. In this way, the soul is tripartite:

All three parts of the soul can have desires. The desire in reason is or stems from beliefs about what is good and what is bad. This, however, is not true of the appetite and spirit. The desires in these parts arise independently of any beliefs about what is good and what is bad.

The 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).

  "The soul of the thirsty then, in so far as it thirsts, wishes nothing else than to drink, and yearns for this and its impulse is towards this.
  Then if anything draws it back when thirsty it must be something different in it from that which thirsts and drives it like a beast to drink. For it cannot be, we say, that the same thing with the same part of itself at the same time acts in opposite ways about the same thing.
  We must admit that it does not.
  So I fancy it is not well said of the archer that his hands at the same time thrust away the bow and draw it nigh, but we should rather say that there is one hand that puts it away and another that draws it to.
  By all means.
  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?
  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.439a).
To begin to understand the Tripartite Theory of the Soul, consider the 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 two desires in play here. One stems from appetite. This is the desire to drink. In the absence of a contrary desire from reason, this appetitive desire would move the person to take steps to drink. Reason, however, in the example, has the desire not to drink because it has the belief that drinking is bad in the circumstances. If reason rules, the path from the appetitive desire to action is interrupted. Reason overrides the appetite.

Socrates argues for this understanding in terms of a principle about opposite motions.

In this argument, he conceives of desire and aversion with respect to a given thing as opposite motions of the soul. Desire is the motion to the thing, and aversion is the motion away from the thing. If someone is thirsty, then his thirst gives him a desire to drink. If, however, he thinks that drinking is bad in the circumstances, he also has a desire to not drink. Given the principle about opposite motions and that the desires to drink and to not drink are opposite motions, Socrates concludes the two desires belong to different parts of the soul. The appetitive part of the soul has the desire to drink, and the reasoning part of the soul has the desire not to drink.

  "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, ye 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 (τῷ 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).
In addition to the existence of reason and appetite, Socrates argues for a third part of the soul. He says, in the case of Leontius (Republic IV.439e-440a), that some part of the soul conflicts with the appetitive part and also that children have spirit but "as for reason (λογισμοῦ), some of them... never participate in it, and the majority quite late" (Republic IV.441a). The argument in these remarks seems to be that a conflict of the sort in Leontius also occurs in children and animals (Republic IV.441b) but since animals lack reason and reason does not play a controlling role in the actions of children, there must be a third part of the soul. This part is spirit.

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).

The Representations Necessary for Action

  "In heaven's name, then, this business of imitation is concerned with the third remove from truth, is it not?
  Yes, Socrates.
  And now again, to what element in man is its function and potency related?
  Of what are you speaking?
  Of this: 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.
  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?
  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) to it at the same time.
  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.
   That which opposes it must belong to the inferior parts of the soul.
  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).

"So we were right not to admit him into a well-ordered city, because he arouses and nourishes this part in the soul, and by strengthening it tends to destroy the rational part (τὸ λογιστικόν), just as when in a city one puts bad men in power and turns the city over to them and ruins the better sort. Precisely in the same manner we shall say that the mimetic poet sets up in each individual soul a bad constitution by making images far removed from reality, and by currying favor with the senseless (ἀνοήτῳ) part that cannot distinguish the greater from the less, but thinks the same thing now one, now the other" (Republic X.605b).

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

"[T]hings 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).
Appetite and spirit can move a human being to action. For this to happen, it seems that there must representations of what to desire. Further, to trigger these desires in particular circumstances, it seems that there must be representations of how the world is.

What are these representations? Are they beliefs? Do they belong to appetite and spirit?

An Argument for Belief in Appetite and Spirit

In this discussion of imitation, 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" (Republic X.602e).

Suppose, then, that lines are arranged so that one appears longer than the other, that measurement reveals they are equal in length, that after measurement reveals they are equal, the appearance persists because the arrangement of the lines tricks the eyes. Is this appearance a belief that belongs to one of the "inferior parts of the soul" (Republic X.603a)?

Certainly it seems true that the unequal appearance of the lines results from looking, not reasoning. So if reason is the superior part of the soul, and perception is in the inferior parts, then this appearance is the result of a process that seems to begin in the inferior parts of the soul.

Is this appearance a belief in one of the inferior parts of the soul?

In the example, there are contradictory propositions each with a different history. How Socrates understands these propositions and their histories is difficult to see, but he seems to understand them in terms of "belief forming motions" (to which the principle of opposites applies). The proposition that one line is longer than the other comes from looking at the two lines. The proposition that the lines are equal in length comes from drawing a conclusion in terms of measurement. The issue, it seems, is which proposition to believe. Socrates thinks, correctly it seems, that it is rational to believe the second proposition and to reject the first. Equally, although Socrates does not point this out, it seems that for someone who looks at the lines but does not know about the illusion, it is rational to believe the first proposition.

The "belief forming motions" are in different parts of the soul. There is a motion of assent to the proposition that one line is longer than the other. This is a motion to believe the proposition. There is a motion of dissent from this proposition. This is a motion to not believe the proposition. These "belief forming motions" are opposites (Republic IV.437b). One is toward believing the proposition. The other is away from believing the proposition. So, given the principle of opposites, these "belief forming motions" are motions of different parts of the soul. In the case in which it is rational not to believe that one line is longer, it seems that reason stops the opposite motion to believe from resulting in belief (just as in the example to establish reason and appetite, reason stops the motion to drink in appetite from resulting in drinking).

If reason does not stop the belief forming motion, what part has the resulting belief?

The answer, it seems, is that the belief is one of the inferior parts of the soul. Further, when the beliefs have their origin in these parts (appetite and spirit), they are a matter the use of the senses, memory, and imagination to grasp sensible features reality. The beliefs that have their origin in reason are different. The cognition in reason includes the use of questioning and other methods (such as "measuring and numbering and weighing") to grasp nonsensible features of reality.

How Reason Rules Spirit and Appetite

Given that it "belongs to the reasoning part to rule" the other two parts of the soul (Republic IV.441e4), there must be some way or ways for reason to control these parts.

In the Republic, it is through the extensive education and system of censorship that this control occurs. The society is organized so that when a person is young the appetitive and spirited part of his soul become habituated to having the desires 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.
  And tales are of two species, the one true and the other false.
  Yes" (Republic II.376e).

"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, which is traditionally a late dialogue, there is the suggestion that reason can control 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 takes less anticipatory pleasure in smoking. Reason, in this way, can use the power of imagination to recalibrate the strength of the desire to smoke.

In the Republic, however, there is no need to correct the desires of the appetite because the education does not allow them to become inappropriately strong in the first place.

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 " 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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