Glaucon and Adeimantus, both brothers and Athenians (brothers of Plato), make up the bulk of the remainder of the Republic. Both brothers are praised by Socrates for their noble actions as soldiers at Megara and also for their aristocratic lineage, descending from Ariston (meaning “excellence”). The Battle of Megara was a crucial victory for the Athenians in the Peloponnesian War against Sparta.
Socrates begins the next section thinking he has freed himself from argument, but acknowledging that the acts of Book I seems to have only been a “prelude” (357a). While Thrasymachus, the foreign tyrant, has been tamed in Book I, his exchange with Socrates appearing to be little more than a joke taking lightly the virtue on justice in question, Glaucon. Thrasymachus takes his sophisticated art seriously, but not the question of justice.
At any rate, the inquiry into the nature of justice has now passed beyond the three claims of Book I, each definition falling short, and has passed to the more refined Athenian brothers who both launch an inauthentic attack on justice, in order to hear Socrates make a substantial praise of justice. Glaucon claims there are three kinds of goods 1) that which is good for its own sake, 2) that which is good for its own sake and for another 3) and that which is good for another sake. When asked, Socrates supposes that justice is the second kind of good which occurs for its own sake, as well as another sake. Glaucon defends Thrasymachus’s thesis that injustice is preferable to justice, but only in order to receive a proper praise of justice by Socrates.
First, Glaucon gives an account of the origin of justice. According to this argument, people commit justice unwillingly. They are always and everywhere seeking to commit acts of injustice for their own seeming profit, and to minimize their own suffering of injustice. It is the base, or slave, morality of Nietzsche laid out in the Genealogy of Morals. When it cannot be avoided, people look to make compacts with others neither to commit injustice nor to suffer it. The great masses of weak men commit wanton acts of injustice toward one another. Each man commits injustice and fears receiving acts of injustice toward themselves. Therefore, born of fear, men make compacts with one another in attempt to enforce justice. In contradistinction to Thrasymachus, Glaucon claims that justice is the advantage of the weaker. The perfectly just man and the perfectly unjust man are what Glaucon is concerned with. His conception of both is entirely divorced from art and nature, unlike Thrasymachus. However, like Thrasymachus he holds fast to the claim that the good life is fundamentally tyrannical. The paradox of honor and justice is that they both presuppose and also precede life in importance. Once he has completed this account of the origins of justice, Glaucon defers to the poets.
Here, Glaucon is given recourse to recount the famous story of Gyges, the Lydian shepherd. Recall Herodotus’s story of Gyges’s who looks upon the king’s wife at the king’s suggestion and must either kill himself or else kill the king and thereby become king himself, the latter of which he chooses (at the urging of the king’s wife). In Socrates’s tale, a great thunderstorm and earthquake happens, opening a chasm in the ground which Gyges first saw, wondered at, and then “went down”. He saw many marvelous things, one of which was a hollow bronze horse with windows and upon looking in he a larger than life corpse inside. It had no clothes, save for a gold ring which he slipped off and took. When it was time for the shepherds to give their regular report of the flocks to the king, Gyges turned the collett of the ring inward towards his hand and became invisible, and vice versa. He then became a messenger for the king. Upon arriving, he committed adultery with the king’s wife and killed the king so he became ruler.
Lastly, building on his two prior key points, Glaucon considers the perfectly just and the perfectly unjust man. The former may appear to be just to the masses and gains power, while the latter undergoes much suffering in the name of justice. The key distinction Glaucon makes is between seeming to be just, and actually being just, between opinion and truth. Recall that Glaucon is the reason Socrates remains in the Piraeus and he is also responsible for much of the remaining dialogue in the Republic. At any rate, Socrates must defend the just man who leads a mostly miserable life, according to Glaucon.
Before Socrates can respond in “delight”, Adeimantus comes to a strong defense of his brother, Glaucon. He adds that parents extoll the virtues of justice to their children not for its own sake, but for the praise and reputation one receives for being just. For this argument he cites the authority of Homer and Hesiod, the poets. He also adds that Socrates’s genuine praise of justice must exclude divine rewards and punishments, along with not relying upon the authority of the poets. Glaucon’s defense is characterized by his manliness and impetuosity, while Adeimantus is moderate and quiet. Adeimantus is interested in justice as pleasantness and easiness.
The demands from the two brothers on Socrates can be summarized as follows: Socrates must praise justice as choiceworthy for its own sake, that justice is a pleasant option to choose, and also that justice will make a man happy, even in the midst of extreme suffering. According to these demands, we must judge Socrates’s defense of justice throughout the remainder of the Republic and also in considering his treatment of the poets and the gods.