Republic IX.580d-587a

⊕ "The three parts of the soul have, it appears to me, three kinds of pleasure, one peculiar to each, and similarly with desires and kinds of rule" (Republic IX.580d).

τὸ φιλοχρήματον, τὸ φιλοκερδὲς.

  "[W]e called it the appetitive part because of the intensity of its appetites concerned with food and drink and love and their accompaniments, and likewise the money-loving part, because money is the chief instrument for the gratification of such desires.
  And rightly.
  And if we should also say that its pleasure and its love were for gain or profit, should we not thus best bring it together under one head in our discourse so as to understand each other when we speak of this part of the soul, and justify our calling it the money-loving and gain-loving part?
  I, at any rate, think so" (Republic IX.580e).

τὸ φιλόνικον.

  "And, again, of the high-spirited element, do we not say that it is wholly set on predominance and victory and good repute?
  Yes, indeed.
  And might we not appropriately designate it as the ambitious part and that which is covetous of honor?
  Most appropriately" (Republic IX.581a).

τὸ φιλόσοφον.

  "But surely it is obvious to everyone that all the endeavor of the part by which we learn is ever towards knowledge of the truth of things, and that it least of the three is concerned for wealth and reputation.
  Much the least.
  Lover of knowledge (φιλομαθὲς) and lover of wisdom (φιλόσοφον) would be suitable designations for that.
  Quite so (Republic IX.581b). "[T]hose desires of even the profit-loving and honor-loving parts of the soul, which follow knowledge and reason and pursue with their help those pleasures which intelligence prescribes, will attain the truest pleasures possible for them, since they are following the truth. These pleasures are proper to them, if that which is best for each thing may be said to be most proper to it. So if the whole soul follows the wisdom-loving part [reason] and there is no internal dissension, then each part will keep its own task and be just, and also each will reap its own pleasures, the best and the truest as far as possible" (Republic IX.586d).

Argument

1.  In the just soul, the parts of the soul have their truest possible pleasures.
2.  In the unjust soul, the parts of the soul do not have their truest possible pleasures.
3.  If (1) and (2) are true, then those whose souls are just have more pleasure.
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4.  Those whose souls are just have more pleasure.

Explanation

⊕

"[T]o be filled with what befits nature is pleasure (πληροῦσθαι τῶν φύσει προσηκόντων ἡδύ ἐστι)..." (Republic IX.585d). 1. In the triparite theory, the soul has three parts: appetite, spirit, and reason. Each part is capable of desire. The satisfaction of these desires is pleasurable to the extent that the object of the desire is appropriate or "proper." Certain things are good for a human being. These things are "proper." Other things are bad for a human being. These things are "improper." The better the thing is for a part of the soul, the more pleasurable it is to get that thing. So, for example, for someone who is thirsty, drinking water is more pleasurable than drinking mud.

In those whose souls are just, reason knows what is good and is in control. So they have the "truest pleasures possible" because the pleasures they pursue are "proper."

2. In those whose soul is unjust, the parts of the soul are not each doing its own job. Reason does not know what is good and what is bad or is not in control and does not direct action. In either case, the pleasures they pursue are not the "truest pleasures possible."

Evaluation

The argument is valid. If the premises are true, so must be the conclusion. The question, then, whether the premises are true, and very few of us are going to think they are.

Premises (1) and (2) depend on a certain conception of human beings and the world.

Socrates thinks the human soul has three parts (reason, spirit, and appetite), that there is an appropriate way for these parts to be organized, that the appropriate organization is the one in which reason knows what is good and what is bad and directs action on this basis, and that this organization of the parts of the soul constitutes justice in the individual human being.

Socrates also thinks that satisfying a desire can be more or less pleasurable depending on what someone does to satisfy it. This is pretty plausible, but Socrates seems to have something more in mind when he talks about "true" pleasures. He seems to think that for some bodily desires, we do not get much pleasure from anything we do to satisfy them.

  "[The many have not ever] been really filled with real things, nor ever tasted stable and pure pleasure, but with eyes ever bent upon the earth and heads bowed down over their tables they feast like cattle, grazing and copulating, ever greedy for more of these delights; and in their greed kicking and butting one another with horns and hooves of iron they slay one because their desires are insatiable. ⊕ "The part of the soul where the desires are, the licentious and fissured part, he called a leaky jar, because it is so insatiate" (Gorgias 493b). For the part they are trying to fill is like a vessel full of holes, and neither it nor the things they are trying to fill it with are real.
  You describe in quite oracular style, Socrates, the life of the multitude" (Republic IX.586a).

Socrates also thinks that engaging in the love of wisdom to think about the forms is particularly pleasurable because it is the activity that befits reason in the soul.

Moreover, even if we grant premises (1) and (2), it is not obvious that premise (3) is true.

It seems possible for pleasures in those whose souls are just to be "proper," and thus the "truest," but for the circumstances to prevent them from spending much time in the pleasures of reason. Without a calculus to sum pleasures, it might be that the life of some whose souls are just is less pleasurable than the life of the tyrant and others whose souls are not just.

We may wonder, then, whether Socrates has met Glaucon and Adeimantus's challenge. ⊕ "[You are saying, Socrates, that] if a man be caught criminally plotting to make himself a despot, and he be straight a way put on the rack and castrated and have his eyes burnt out, and after suffering himself, and seeing inflicted on his wife and children, a number of grievous torments of every kind, he be finally crucified or burnt in a coat of pitch, he will be happier than if he escapes and makes himself despot, and passes his life as the ruler in his city, doing whatever he likes, and envied and congratulated by the citizens and the foreigners besides" (Gorgias 473c).

They ask about the man who is subject to horrific punishment because he is wrongly thought to be unjust. He "will have to endure the lash, the rack, chains the branding-iron in his eyes, and finally, after every extremity of suffering, he will be impaled" (Republic II.361e), and they ask Socrates to show that the life this man lives is better than the life of a man who gets away with his crimes and has money, reputation, other things thought to be good.

For the sake of argument, we can assume the soul of this man is just and thus that he desires what is appropriate and gets these things to the extent that the world cooperates. The world, though, in the thought experiment, does not cooperate. The man spends little time in the love of wisdom and is subject to the punishments Plato's brothers describe.

This man desires not to be subject to the punishments, but his desire is frustrated.

⊕ "You, judges, must regard death hopefully and bear in mind this one truth: that no bad can come to a good man, in life or after death, and God does not neglect him" (Apology 41c). There is a temptation to think this frustration is very painful, but Socrates appears not to have this view. He thinks that those whose souls are not much concerned with the body. They have trained themselves to ignore its demands so that they spend time in the love of wisdom.

Further, Socrates thinks that the man in the challenge whose soul is unjust is in misery because he wrongly believes that satisfying the desires of the body is of the first importance. His life is like the life of someone who continually tries to satisfy his thirst by drinking mud.