In defending the view that justice is the advantage of the stronger, Thrasymachus puzzlingly claims that rulers never err and that any practitioner of a skill or expertise (τέχνη) is infallible. In what follows, Socrates offers a number of arguments directed against Thrasymachus’ views concerning the nature of skill, ruling, and justice. However, both Thrasymachus’ views and Socrates’ arguments against Thrasymachus’ views have frequently been misunderstood. In this paper, I clarify Thrasymachus’ views concerning the nature of skill and ability, reconstruct Socrates’ arguments against Thrasymachus’ views concerning skill and justice, and argue that Socrates’ arguments are better than often supposed.