Thrasymachus’ first definition of justice is easy to state, but it is not so immediately clear how it is to be interpreted. Justice, he claims, is the advantage of the stronger. On its own, such a sentence could imply that what is beneficial to the stronger is just for and therefore, beneficial to the weaker, and Socrates accordingly asks whether this understanding is accurate. Thrasymachus promptly responds in the negative. The interpretation he proceeds to expound upon can be summed up by adapting slightly his original definition: justice is that which obtains the advantage of the stronger. To support this definition, he points to the example of ruling a city. Any ruling class will fashion the laws of the commonwealth with a view to its own benefit, he asserts. Since it is just to obey the law, those who behave justly will be acting for the advantage of the rulers (whom Thrasymachus interchangeably terms “the stronger”).
Socrates makes his first objection at this moment, but I will treat this here only incidentally: merely insofar as it allows us to see why Thrasymachus introduces the craftsman analogy. Socrates objects that rulers are, as humans, bound to make mistakes - to confuse their disadvantage with their advantage on occasion. In this case just obedience to laws would work to the ruler’s disadvantage. Thrasymachus responds promptly, saying that a man who makes a mistake in ruling is not at that moment a ruler in the strict sense, and introduces the craftsman analogy to support this idea. Insofar as a man is a craftsman, he will not make any mistakes; mistakes are rooted in ignorance, and so can only occur when a man’s knowledge of his craft is incomplete. The quandary which Socrates introduces is thus avoided by Thrasymachus’ qualification that errors are never made by rulers as rulers.
Though the analogy works at first to Thrasymachus’ advantage, Socrates promptly turns it against him in a new objection. All arts, he asserts, are exercised with a view to the benefit of the subject rather than to the benefit of the artisan. The doctor employs his medical art for the betterment of the patient, the pilot navigates for the safety of the ship and the sailors, and so forth. Like Thrasymachus, he identifies ruling as an art, and claims that ruling also is exercised with a view to the subjects’ benefit. Throughout the argument, Thrasymachus passively assents to Socrates’ individual points. But as we shall see later, he rejects the conclusion drawn from these.
From an objective viewpoint, one immediately questionable aspect of this argument is Socrates’ idea that ruling is an art in the same sense that medicine and...