How applicable is the craft analogy for discussing the virtues, like justice?

Question

In Book I of The Republic, Socrates uses a craft analogy (CA) as part of his argument against Thrasymachus to convince him that justice is not the advantage of the stronger. To do so he equates ruling to a craft. Crafts tend to a certain domain (e.g., doctor), and their purpose is to make the objects of their domain better (e.g., patients). From this he concludes that "no one in any position of rule, insofar as he is a ruler, seeks or orders what is advantageous to himself, but what is advantageous to his subjects; the ones of whom he is himself the craftsman."

This seemed like a big jump to me, which entails some underlying premises which are not made explicit as part of the argument. Robert Coltert specifies these underlying premises as such:

1. First, it presupposes that the virtues [in this case, justice] are analogous to the crafts in all salient aspects.
2. The second assumption is that all crafts have the same structure and are analogous to one another.

If these assumptions do not hold, then the use of the CA as a method of refutation is called into question because various crafts might have different structures and a definition of virtue need not make that virtue be analogous to every craft, and thus the CA is not a reliable method of investigation.

Furthermore, a bigger problem with the CA arises further in the argument when Socrates claims wage-earning is an auxiliary craft other crafts rely on:

If wage-earning is a craft - and Socrates calls it one at 346c - then wage-earning is itself a counterexample to the claim that no craft benefits its practitioner. The benefit provided by wage-earning is the wages that the practitioner receives.

These two underlying premises seem quite far-stretched to me, and I was surprised they were not given any further attention as part of the dialogue in Book I.

• What are some arguments for these underlying premises to be true?
• Does Socrates or later philosophers discuss this exact issue elsewhere? I only found the discussion by Robert Coltert, thus do not known how widespread this concern is.

Answer 1

These two underlying premises seem quite far-stretched

To me, it's the attribution to Socrates of these two premises that seems a bit far-stretched. Let's examine them in order.

First, it presupposes that the virtues [in this case, justice] are analogous to the crafts in all salient aspects.

This seems wrong, even nonsensical. I don't see what kind of analogy could there be between a virtue and a craft. The relation seems rather to be something like the following:

a. A good ruler is one who works for the benefit of the ruled, not for one's own benefit.

There is no one in any rule who, in so far as he is a ruler, considers or enjoins what is for his own interest, but always what is for the interest of his subject..

b. Justice is a good quality of action.

Then the just has turned out to be wise and good and the unjust evil and ignorant.

c. Therefore, justice cannot be the benefit of the ruler, pace Thrasymachus.

Next,

The second assumption is that all crafts have the same structure and are analogous to one another.

Not quite. Socrates does make this general assertion, but it is not an assumption in his argument. The argument does not depend on this generalization, but on a more direct analogy between specified particular cases. Just as the good doctor works for the benefit of the patients, just as the good pilot works for the benefit of his crew and passengers, so any good ruler works for the benefit of the ruled, and not for the benefit of oneself.

Then, I continued, no physician, in so far as he is a physician, considers his own good in what he prescribes, but the good of his patient ...
And the pilot likewise ... will provide and prescribe for the interest of the sailor who is under him, and not for his own or the ruler's interest ...
Then ... there is no one in any rule who, in so far as he is a ruler, considers or enjoins what is for his own interest, but always what is for the interest of his subject or suitable to his art; to that he looks, and that alone he considers in everything which he says and does.

Answer 2

This thread is kind of a mess because it too much reads passages out of context in Republic i. The analogy drawn between craft and virtue is set up by Polemarchus insisting the justice is benefitting friends. Well, one will then need knowledge of friends and how to benefit them. The crafts are kinds of knowledge distinguished by the unique benefit their knowledge is the power to produce for some limited class of objects in some limited domain. So medicine is the knowledge (hopefully) for producing health in living bodies in the domain of health and sickness and so on. When they, Socrates and Polemarchus, go looking for justice as if it were a craft, no matter what benefit they try out in no matter what domain, there is already there an art for that. So justice ends up being useful only when we're not doing anything with anything. This suggests that justice is NOT a craft since fairness would seem to cut across ALL domains. Next, it turns out that craft knowledge is of and capable of being used for contrary purposes. It is the same knowledge that produces hacking as defense. So one can be a crafterson and be rather sleazy (no commitment of character). But to be just, one seemingly needs a commitment of character. Finally, Thrasymachus drives the craft analogy because he insists that rulers have expert knowledge that never fails them. Now, if justice is like a craft and crafts never benefit the practitioner of the craft, as in Socrates refutation, then justice NEVER benefits the practitioner. And we know Socrates doesn't endorse that! Justice is like a craft in that it provides and benefit and you do need knowledge, but Plato gives way too many hints that the analogy doesn't work. And the background is likely sophism: crafts can be taught. Unclear virtue can be.