Thrasymachus's challenge

Thrasymachus has the misfortune of being remembered through the eyes of someone who despised him. He was a Sophist, one of the professional teachers who flourished in Athens during the time of Socrates. Unlike Socrates the Sophists charged a fee for their instruction, and Plato is quick to insinuate that they liked money more than truth. Plato is especially hard on Thrasymachus, who is introduced in the ‘Republic’ like this:

While we had been talking [says Socrates] Thrasymachus had often tried to interrupt, but had been prevented by those sitting near him, who wanted to hear the argument concluded; but when we paused, he was no longer able to contain himself and gathered himself together and sprang on us like a wild beast, as if he wanted to tear us in pieces. Polemarchus and I were scared stuff, as Thrasymachus burst out and said, “What is all this nonsense, Socrates?”

The “nonsense” was a discussion of the nature of justice. Thrasymachus was impatient because Socrates and his friends were assuming that justice is something real and important. Thrasymachus denied this. According to him, people believe in right and wrong only because they are taught to obey the rules of their society. These rules, however, are merely human contrivances. Thrasymachus added that the ethical code of a society will reflect the interest of its ruling classes, so when ordinary people think they must “do the right thing,” they are just being chumps. ~ Page 150