Thrasymachus was a prominent figure in ancient Greek philosophy, known primarily for his role in Plato's dialogue, the Republic. He was a sophist, a teacher of rhetoric and philosophy, who argued that justice is the advantage of the stronger. His views challenged traditional notions of morality and ethics, emphasizing power and self-interest. In the Republic, Thrasymachus engages in a debate with Socrates, asserting that rulers create laws to benefit themselves. His ideas sparked significant discussion about the nature of justice and the relationship between power and morality, influencing later philosophical thought on these topics.