Socrates establishes three arguments to demonstrate that a man who is just lives a happier and better life than an unjust man.
Socrates takes as his first example the tyrant. It might appear to an immature thinker, or a child, that the tyrant, exercising despotism as he does, is surely a happy man; after all, it is plain that the tyrant can live surrounded by pomp and ceremony and all that wealth can buy. All of his subjects he may treat as objects; he can kill any citizen of his state at whim. But we must remember that the tyrant himself is just as much a slave to his own mad master, his lust, as his subjects are enslaved to his tyranny. The best parts of the tyrant's soul are governed, tyrannically, by the worst part of his soul, and he can never escape the dark prison of his days. The tyrant, who is never in control of himself, is miserable.
In contrast to the tyrant, the just man is free; he is enslaved to nothing, for nothing in his desires or emotions can captivate him; since his whole life is governed by his reason, he lives a self-controlled life, happy in his knowledge and happy that he knows it.
In initiating his second argument, Socrates repeats his argument that the soul is divided into three parts: reason, the spirited part, and desire. So we must remember that there exist three basic types of men: the man of reason who seeks knowledge; the "spirited" man who seeks honor and success; and the man of desire who seeks gain (wealth) and satisfaction. Remember that the man of reason possesses knowledge of the Forms, hence, Justice. Thus it is that the first man is the just man; the second, the timocratic man; and the third is a sort of mixture of the oligarchic, democratic, and tyrannical man. If we were to ask each of these men if he thought himself to be the happiest of the three, each would probably answer yes. It is entirely possible that each man may have experienced happiness, but only the man of reason could have experienced the happiness of knowledge because he alone of the three possesses it, besides possessing the happiness of the other two men. Thus it is that the man of justice is correct in his judging himself to be the happiest. And it is self-evident that the man of reason is best fitted to judge, since he alone of the three knows Justice.
Socrates' third argument proves out by his making a distinction between pure (positive) pleasure and illusory pleasure (a kind of pleasure which is reliant upon an antecedent "pain"). Such an illusory pleasure might be that of eating (because we are hungry), or drinking, or, one assumes, any sort of sensual pleasure. But pure pleasure, such as the study of knowledge, is reflective of the pleasures of the soul independent of the body, such as aesthetic pleasures or contemplation of the Forms. And we must remember that the illusory pleasures are merely images; knowledge and its study are real. Thus it is that the just man, secure in his knowledge, is the happiest of men.
At this point in the dialogue, Socrates summarizes his argument for the just man, and he answers the other participants in the debate who had argued that the unjust man would lead the best life so long as he could keep his reputation intact, thus fooling his fellow-citizens.
Now we may behold the unjust man, who has ruined his own life by denying his reason and feeding to surfeit his bestial appetites. Nothing can ever profit him for the evils he has visited upon himself, as well as upon others. A man must learn to govern himself through his exercise of reason, lest he live a life of misery. And if he cannot be guided by his own reason, he should, like the craftsmen in the Ideal State, learn to be guided by the intelligence and reason of others — the philosopher-rulers, who will grant him justice and provide for him a happy and fruitful existence.
Thus we have made our way through the major argument of our dialogue. We would be wise at this point to review the entire dialogue to date, refreshing our memories of the material discussed and the major theses advanced and refutations attempted by the participants. We should also at this point review the Socratic method employed throughout the dialogue, the various rhetorical ploys the speakers employ, and the systems of logic they adopt in their quest of knowledge.
First, throughout the entire dialogue, Socrates has employed argument by analogy, a rhetorical device that seeks to establish similarities between the point of the case being argued and like cases (for example, the similarities between the knowledge of a common dog and a Guardian in their shared ability to discern a friend from a potential enemy). In the summary (immediately preceding) we have demonstrated Socrates' argument from examples of types of unjust men. And then Socrates argues the just versus the unjust man by arguing comparisons and contrasts. Socrates, we remember, has initiated every major movement in his argument by arguing questions of meaning, in which cases he seeks definitions. (A dictionary definition, also known as a lexical definition, usually will not suffice in philosophical debate, which requires an extended, or rhetorical, definition.) In each case of Socrates' arguing specific examples of what may be proved out to be demonstrably true — empirical evidence — he is arguing questions of fact. In Book X of our dialogue, Socrates will argue Platonic theory, or conjecture — questions of probability.
We are now ready for Book X of the present dialogue, which presents Plato's view of the arts and Plato's theory of the immortality of the soul.
foot-pad a highwayman who traveled on foot, robbing travelers; a mugger might be the modern equivalent.
inanition lack of strength or spirit; emptiness; weakness.
Chimera a mythical monster, usually depicted as having a lion's head, a goat's body, and a serpent's tail.
Scylla another monster, this one the female personification of a rock, dangerous to ships, on the Italian side of the Straits of Messina, opposite the whirlpool Charybdis (which was personified as Scylla's companion monster).
Cerberus a mythical three-headed dog that guards the gate of Hades.
caitiff a mean, evil, or cowardly person; a wretch.
"By the dog of Egypt" a mild oath; the "dog of Egypt" is Anubis, an Egyptian god pictured as having the head of a dog who leads the dead to judgment. Socrates probably "swears" by this barbarian god to express emphasis without being sacrilegious, as he would be were he to invoke the name of a god of the Hellenes.