Thrasymachism

It is a mistake to ascribe to Thrasymachus the opinion that “might makes right”, if one means this in a prescriptive sense.

Thrasymachus made no distinction between what is called justice and “true” justice. He always used the word “justice” to refer to the former, that is, to what the word means in popular use. What is called justice, in turn, is defined by the rulers of states when they write their legislation (338e) – and they always write it in the way that they think is advantageous for themselves.

So, while he did say that “justice is nothing other than what is advantageous for the stronger” (338c), this is not to mean something good about the stronger, as though they deserved to rule for being superior – as, for instance, Callicles thought, in the Gorgias, 483c – but rather something bad about justice. Justice is a fool’s game, says Thrasymachus, because it is a set of arbitrary rules created by self-interested legislators. This is plainly true of what is called justice in every state, in each according to its laws.

Accordingly, he denied that justice is a virtue (348c), since it is not good for the one who has it, as a virtue should be; rather, it is good for the unjust, in which he includes foremost the legislators themselves (343c), but also anyone else who breaks the laws when it is good to do so. Good, that is, for himself.

Thrasymachus is important to the Republic because he sharply divides the metaphysical good – the object of correctly-formed rational desire – from the moral good, that is, the just. He believes, very soundly, that “the good is what all desire”, and what all people seek through their rational actions; he denies that justice is good. To seek the just is, often, to seek the bad, as a sacrifice for the good of others.

That is, in modern terms, Thrasymachus is a moral non-naturalist. The moral good is arbitrary and has no relation to what rational people desire to seek; the (morally) “good life” is not necessarily the life that you want, even if your passions and reason are in perfect order. To be just, you must sometimes be irrational, and purposely act against your best interest.

It is, of course, impossible to prove him wrong, and the dialogue never does. What it does, instead, is persuasively present the correct doctrine, that the metaphysical and the moral good are the same. It does so by presenting a fundamentally correct moral psychology by means of an elaborate poetical metaphor; in the metaphor, a man is compared to a city, and a just man to a wisely ruled city, and an unjust man to an unwisely ruled one. Since no one denies that the wisely ruled city is the good city, the good appear to be the just.

The state is merely man writ large; the metaphor cannot truly prove anything, but only show more clearly a concept of human nature which someone already holds. Not everyone will hold it in the first place; there are still non-naturalists, and there may always be.