What is the difference between phronesis and sophia in Aristotle's ethics?
Sophia for Aristotle is theoretical accuracy, whereas phronesis is practical wisdom. More technically, sophia is the virtue of the part of the soul responsible for theoretical accuracy, the purely rational, human part of the soul, whereas phronesis is the virtue of the part of the soul responsible (on Aristotle's account) for the application of practical and theoretical reasoning to the world, and is as such, concerned mainly with minding (φρονεῖν) the particulars relevant for action.
Sophia as such concerns the universal starting points of reason -- the universal premises from which all syllogistic reasoning proceeds --, and is how the soul gains episteme, whereas phronesis, is how we grasp the relevance of proper particulars as they pertain to action. For this reason, phronesis, according to Aristotle needs time to develop -- age is a necessary, but not sufficient condition for practical wisdom -- because the mind must learn how different particulars relate to each other and which causes produce which effects. On account of its dealing with the particulars of action, and indeed, how the universals relate to the particulars. Since it deals with particulars, and how particulars relate to universals, Aristotle locates it in a different part of the rational soul: the λογιστική in which the purely rational part connects to the animal part. In modern brain science, we might relate this to the corpus collosum, which enables all the different brain regions to talk to each other: phronesis is the virtue of the part of the soul by which the purely rational and human can talk to the bodily, the animal.
Sophia on the other hand, is clear-sightedness, and Aristotle, in Book 6 of the Nicomachean Ethics, traces its etymology back to its original use with craftsmen -- a sophos cobbler for instance, was one who knew the knowledge of his craft so precisely that he could produce any show. Likewise for the sophos doctor, who could heal any disease, or the sophos poet, who could write any poem. This accuracy -- precision as it pertains to knowledge and skill -- when abstracted from any particular skill, Aristotle calls sophia simpliciter [ἁπλῶς]. Hence perhaps we can see the resonance of his definition with the Socratic account of wisdom as "knowledge of how to use goods generally" which though present in Plato's Meno and Euthydemus (for instance), is, in my opinion, most forcefully represented in Xenophon's Oeconomicus. The argument goes as follows:
-Is money good?
-Certainly Socrates.
-But is it good if you don't know how to use it?
-How do you mean Socrates?
-Well, if some rich and noble youth were to use his ample means to hire the services of a prostitute,
would it benefit him [this is really the example used]? Would he in any way be improved or would he be diminished in wealth, physical health, and the health of his soul?
-Certainly not Socrates.
-So then it seems money isn't good, unless one knows how to use it.
- Certainly.
- And in that way money derives its whole use from the knowledge of how to use it?
- Certainly Socrates.
- So then it appears that knowledge is the good?
- Yes, Socrates, knowledge is the good.
- What about scientific knowledge? For instance the knowledge of shipbuilding or medicine. Are these good unless we know how to use them?
-By the preceding argument, I'm forced to agree Socrates.
- So then it appears that no good, whether material or formal, is good for us unless we know how to use it, both in itself and to our benefit.
- It appears so Socrates.
-But what about this particular kind of knowledge, the knowledge of how to use things to our advantage. Will not this knowledge be everywhere and always good?
-By Zeus, it seems so Socrates!
-And what would you call this knowledge? Should we not call it sophia?
-We should Socrates.
-Then it seems, that before we acquire any of the other goods, money, physical beauty, scientific knowledge, or power in the city, we ought first extend all our efforts towards acquiring this?
-Indeed Socrates!
etc.
Hence, from Socrates (through Plato and Xenophon) we perhaps get a sense of what Aristotle thinks about wisdom: it is practical, it is universal, and it is how we direct our own actions for our own benefit. In each case it is an accuracy and an aim. When it is present in craftsmen or scientists, it is bound within the limits of a skill. A Doctor for instance, who is presented with a patient with painfully cold legs, can tell you that we ought to rub the legs if we are to cure the coldness, and can furthermore tell us why, medically and physiologically speaking, rubbing the legs produces heat (friction and blood circulation). This is a kind of wisdom, and the doctor who has it may alone truly be termed a "physician." It defines his kind. However, the doctor, qua doctor, is not equally suited to answer the question: "why should doctors heal?" or "should I heal this person, even though he is a bad man?" Such questions, are, so to speak, above her paygrade, and are the domain of wisdom proper, pure sophia, along with nous, or intellect.
Likewise, phronesis, on our doctor analogy, deals with the question "are these legs cold?" "do these legs require rubbing?" It is about connecting the abstract medical knowledge to a living patient. (Far from a mere philosophical spectre, we can see the danger of sophia without phronesis, in the examples of surgeons, who though capable of removing a gallbladder, often perform the operation mechanically on the wrong patient, because they do not care to check whether the patient they assumed they were working on actually is the patient they assumed they were working on!).
In this way, both phronesis and sophia can be conceived both as different steps in the syllogism (sophia with the starting point and middle terms; phronesis with the practical conclusion), and as dealing with different answers to the question why. To see why, consider the following analogy:
Ship captains must save their passengers.
They can save their passengers by avoiding waves.
They can avoid the waves by moving their wheel in such-and-such a way.
Here are waves, that must be avoided in the way enumerated.
So, I, the captain, must move my wheel in such and such a way to save my passengers.
Sophia is present in steps 1-3, though it is present in 1 in a different way as it is present in 2 and 3 (In 1 it is pure, in 2-3, it is technical wisdom). Likewise, phronesis is present in 4, or, more precisely, in the movement between steps 2-3 and step 4. And whereas steps 1-3, and the virtue of sophia, are concerned with the abstract operation of the science of ship-piloting (why does avoiding save? why does moving the wheel avoid?), and its definition as such (why must ship captains save their passengers?), irrespectively; he virtue of phronesis is concerned with how the universals relate to particulars (why must I turn the wheel now?) -- with what the particulars mean. Hence, in this relation, we can see implicitly a unity between Aristotle's ethics, philosophy of mind, and metaphysics:
Phronesis is the characteristic excellence of a certain part of the rational soul, concerned primarily with identifying how practical universals relate to current particulars, and hence with a different kind of "why" than sophia, which is the characteristic excellence of another part of the rational soul, concerned primarily with universals (technical or pure), and explaining the causes which connect them.