In the Republic Thrasymachus puts forwards what might be the first argument based on an ordinary language conception of philosophy (and is thus a kind of empirical argument well). Obviously this is the exact opposite of the philosophical method used in the majority of the Republic. Most of the Republic proceeds on the assumption that the majority of speakers could easily be wrong in their use of words and, furthermore, that the correct understanding of concepts such as justice can be achieved through philosophical insight stemming from the rational reflection on the concepts achieved when we leave behind our existing biases and prejudices. This method is itself justified by Plato’s metaphysical and epistemic doctrines, since he believes that the mind has direct access to the world of forms, and thus can perceive general truths, such as those about justice, directly. The method of Plato and the method of Thrasymachus couldn’t be less alike, and yet Plato never criticizes Thrasymachus’ method, and in fact Thrasymachus himself is unable to completely adhere to it. And so an opportunity for the two methods to go head to head is missed.
But before I say any more about the method of Thrasymachus let me first discuss the argument he invokes to defend his claim that justice is the advantage of the strongest. First Thrasymachus says who the stronger are (since Socrates has just previously claimed that he cannot understand Thrasymachus specifically on this point). He states that the strong are the ruling party, the person or persons who make the laws. Thrasymachus then goes on to observe that the rulers always create laws that are to their advantage. “a democracy democratic laws and a tyranny autocratic and the others likewise”. (338e) And finally he notes that everywhere this is called justice. This argument can only be considered valid if we accept the key premise behind ordinary language philosophy, that the meaning of words is determined by how the majority of people use those words. And thus if the majority of people use the word “justice” to refer to rules designed for the advantage of the stronger then justice is the advantage of the stronger. Naturally such a method drags with it an empirical investigation as well, which Thrasymachus sums up in his second claim, namely that all (or at least most) people do in fact use the word to designate this thing. Thrasymachus’ empirical claim then is that all ruling parties do in fact make laws to their advantage, a claim which must be falsified or confirmed by actually going out there and looking at what ruling parties do.
Socrates is of course unhappy with this conclusion and so he challenges Thrasymachus. But he does not challenge his method, he does not dispute the claim that justice is whatever the majority of people happen to call just. And he very easily could have. Knowing Socrates he probably would have argued by analogy, and perhaps reasoned that we wouldn’t consider counterfeit money genuine even if the majority of people were fooled by it, and thus that we shouldn’t consider Thrasymachus’ “counterfeit justice” real justice, even if citizens believe it to be such. But Socrates does not do this. Instead he simply points out that surely some rulers error and enact laws not to their advantage. And thus what people call just cannot always be the advantage of the strong. Obviously this criticism could in turn be rejected by an ordinary language philosopher who had refined their method. They might argue that the meaning of a word is what it most often is used to refer to, and thus that as long as the majority of rulers enact laws to their advantage most of the time that Thrasymachus’ conclusion holds. But, on the other hand, Thrasymachus’ claim may not in fact hold, many, probably most, government have a pattern of enacting laws that are not completely to their advantage. And so let us simply accept that there is something wrong with Thrasymachus’ epistemic generalization.
Thrasymachus’ friend Cleitophon is the first to respond to this criticism. He attempts to avoid such objections by reinterpreting Thrasymachus’ original claim, saying that “by the advantage of the superior he meant what the superior supposed to be for his advantage.” (340b) And this could be improved further by adopting a new claim, similar to Thrasymachus’ original, that justice is what the stronger desires. This avoids the possible confusions arising from making a distinction between what is to the stronger’s advantage and what they think is to their advantage. And it has the virtue of allowing for ruling parties, however rare, who may be guided by principles and not purely by their selfish desires.
However Thrasymachus rejects this improvement. Instead he pursues a much stranger course, redefining what a ruler is so that people only count as rulers when they are in fact making laws that actually are to their advantage. In fact he would extend this to all professions, stating that “do you call one who is mistaken about the sick a physician in respect to his mistake or one who goes wrong in his calculation a calculator when he goes wrong and in respect of this error? Yet that is what we say literally – we say that the physician has erred and the calculator and the schoolmaster.” (340d) Here Thrasymachus is abandoning his method, or at least one of the assumptions that underpins it. Previously we were to accept as just whatever most people call just. And yet now Thrasymachus would have us believe that most people can be in error when they call someone a ruler, if they are ruling in a way that is not to their advantage. Socrates does not follow up on this, but clearly we must admit that, given this, Thrasymachus’ argument falls down because of internal contradictions: either he is wrong now or he was wrong earlier, and so we need consider it no further.
This leaves us with two pressing questions: why did Thrasymachus abandon his method and why did Socrates completely overlook the methodological issues? One of my colleagues has suggested that Thrasymachus makes methodological mistakes because his method is not the motivation for his claims. Rather Thrasymachus is committed to the idea that justice is to the advantage of the stronger (perhaps he was channeling Nietzsche) and was simply using whatever tools would allow him to get to that conclusion. And thus Thrasymachus is moved to abandon his method rather than his claim. Perhaps that is part of it, but the Thrasymachus of the Republic is probably at least a bit fictional, surely Plato didn’t have to make him reason in such an illogical way (i.e. prioritizing the conclusion over the premises, which is methodologically backwards because we should always be less certain of the conclusion than we are of the premises, else we should be arguing in the other direction). Maybe Plato simply isn’t sensitive to such methodological issues. Although Thrasymachus uses a different methodology to arrive at his claims perhaps this is an accident, a single argument which has appeared for this theory of justice, but which was never examined from a methodological standpoint because it was the only one of its kind. Or it may be because Plato (and Socrates) simply don’t have a way to deal with the argument on the methodological level, which may also explain why Cleitophon’s modified (and more resilient) claim receives no attention whatsoever. Although Plato has the firm belief that his method works and can lead us to the truth he simply may not have a way to justify it from a methodologically neutral position, or argue against alternate methods. Thus the issue remains untouched even though everything else, from metaphysics to epistemology, seems to receive some time in the Republic.