Socrates’s infamous exchange with Thrasymachus occurs in two parts. In the first part, Thrasymachus lashes out at Socrates claiming that justice is the advantage of the stronger, and also that injustice is more profitable than justice. In the second part, after Socrates has successfully tamed the tyrant, Thrasymachus placates Socrates with a “banquet” of words (354a). This exchange ends Book I, yet the interlocutors are still left wondering about the nature of justice –what is the just?
At the outset of the exchange, Socrates twice says that he is “frightened” of Thrasymachus and he compares him to a “wild beast” because Thrasymachus discourteously enters the discussion. Throughout Book I, Thrasymachus was being forcibly restrained until he could contain himself no longer. Angrily, Thrasymachus demands that Socrates answer his own questions, while Socrates hides under the veil of ignorance by claiming he does not know anything. Socrates turns the conversation back on Thrasymachus by asking questions.
Thrasymachus demands that Socrates pay a fine for his learning (a common practice for the Sophists). Socrates amusingly says he will pay Thrasymachus when he gets some money, but Glaucon reassures Thrasymachus that they all will pay for Socrates. The debt of the philosopher is paid by his friends.
Fittingly, the most savage man present gives the most savage opinion of justice. Thrasymachus claims that justice is the advantage of the stronger -that is good, only for the receiver and bad for the giver. He is the blushing tyrant, proved wrong in his own Unjust Speech, while the Just Speech triumphs, unlike in Aristophanes’s The Clouds which lampoons Socrates for teaching his students about the superiority of the Unjust Speech. At any rate, one could make the claim that Cephalus is the oligarch, Polemarchus is the democrat, and Thrasymachus is the tyrant. However, we encounter a problem -why would the tyrant attempt to teach others about the practice of tyranny? Socrates ultimately succeeds in taming Thrasymachus, and Plato makes it clear that we should not behave toward Thrasymachus the same way he behaves toward Socrates. Polemarchus comes to the defense of Socrates and Cleitophon briefly comes to the defense of Thrasymachus.
When the question comes up whether or not the ruler can set down any fallible laws or unjust laws, Thrasymachus claims that any ruler who establishes fallible or unjust laws is not a ruler in the true sense. Justice, for Thrasymachus, demands complete obedience to the infallible laws of the ruler. In comparing Thrasymachus’s thesis to doctors and sailors, Socrates demonstrates that the doctor doesn’t heal for the doctor’s sake, but for the health of the body. Therefore, the ruler rules for the advantage of the city, not the advantage of the ruler. In considering this explanation, Socrates agrees that the just is somewhat of advantage, but is unsure of whether it is the advantage of the stronger.
Thrasymachus fires back. He claims that injustice, ultimately, is preferable than justice. Injustice is more masterful, freer, and mightier. Thrasymachus not only claims that justice is the advantage of the stronger, but also he claims that the life of the unjust man is stronger than of the just man, an ontological claim.
Socrates begins his refutation of Thrasymachus by equating virtue with justice, to which Thrasymachus agrees, and he asks if the unjust man is prudent and good, if the unmusical man is musical, the unwise man wise, unmedical man medical, and so on. Thrasymachus dragged his feet at these assertions and produced a “wonderful quantity of sweat, for it was summer” –he sweats because of the heat and not because of the argument (per Leo Strauss). Thrasymachus also “blushes” (350d), which Leo Strauss claims is also due to the warm summer weather. Socrates and Thrasymachus come to a conclusion that justice is virtue and wisdom, and injustice is both vice and lack of learning. Next, they must consider whether or not injustice is also mighty, as Thrasymachus had originally claimed. Thrasymachus sarcastically and spitefully says he will just simply nod his head in agreement with Socrates, in mindless complicity, because that is clearly what Socrates wishes.
Socrates considers the unjust city that enslaves other cities (an accusation leveled against Athens during the Peloponnesian War, per Thucydides), and also other unjust groups, such as bands of robbers, or pirates –would they be able to exist together if the men acted unjustly toward one another? It comes to light that injustice is a kind of power that disrupts harmony and makes it impossible to accomplish anything. The same problem becomes apparent within the individual soul of an unjust man.
Now that the pious aristocrat, the war-loving democrat, and the abusive tyrant have all been tamed, Book I of the Republic is concluded.
For this reading I used Allan Bloom’s essential translation of Plato’s Republic, as well as Leo Strauss’s The City and Man and his lectures.