Nicomachean Ethics II.4

The question might be asked, what we mean by saying that we must become just by doing just acts, and temperate by doing temperate acts; for if men do just and temperate acts, they are already just and temperate, exactly as, if they do what is in accordance with the laws of grammar and of music, they are grammarians and musicians. 

Or is this not true even of the arts? It is possible to do something that is in accordance with the laws of grammar, either by chance or at the suggestion of another. A man will be a grammarian, then, only when he has both done something grammatical and done it grammatically; and this means doing it in accordance with the grammatical knowledge in himself.

As I have alluded to twice already in this discussion, Aristotle's account of the virtue of justice is going to look like what he is describing here. Justice has two components, fairness and lawfulness; and 'lawfulness' means not "obedience to any laws that may happen to exist," but specifically that the laws that exist should compel people to behave as a virtuous person would.  Thus, it is not necessary to be just yourself in order to behave justly -- which is what he is getting at here. You can be compelled to do so by threat of punishments and shames.

If you behave justly only through fear of punishment and not because you feel inclined to treat others justly, then even though you have behaved justly you are not yourself just. We have now seen enough to distinguish several possible states of character (presented in descending order of virtue): 

1) The person who behaves justly because he takes pleasure in being just even when it is costly, as he is habituated to it and would find anything else uncomfortable. 

2) The person who behaves justly because he knows it is right intellectually, but still finds it painful to render costly justice to others.

3) The person who behaves justly only because he fears the punishment, but would find it more pleasant to behave unjustly because he is habituated to pursuing his own advantage; he finds the costly, just thing uncomfortable.

4) The person who does not behave justly because his habituated injustice is more powerful than his fear of shame or punishment. 

5) The truly vicious person who takes pleasure in being unjust. 

The truly vicious and the truly virtuous actually look fairly similar because they are inverse cases. They are both fully formed characters who are no longer struggling with their actions because their ethics are settled. There are cases in the middle where people are struggling with pleasure or pain, fear or a desire to receive honors, or trying to do what they understand is right even though it hurts. There are parallels on each side of that also. We will talk more about this later.

Again, the case of the arts and that of the virtues are not similar; for the products of the arts have their goodness in themselves, so that it is enough that they should have a certain character, but if the acts that are in accordance with the virtues have themselves a certain character it does not follow that they are done justly or temperately.

To rephrase this slightly: someone performing music well is creating a beauty that is good in itself regardless of why they do it. It doesn't really matter if they are talented or just well-instructed. Someone performing a just act is also creating a good that is good regardless of why he does it -- that is exactly why the laws should compel virtuous behavior even from the vicious -- but it matters a great deal what his internal state is in determining whether he is virtuous or not. 

The [ethical] agent also must be in a certain condition when he does them [in order to be fully virtuous]; in the first place he must have knowledge, secondly he must choose the acts, and choose them for their own sakes, and thirdly his action must proceed from a firm and unchangeable character.

Remember that sentence. It lays out the precise conditions Aristotle holds for virtue to be complete. They are each necessary conditions, e.g. it's not complete virtue if you did an action ignorantly, lacking knowledge of virtue; it is not fully virtuous if you didn't choose the act, but were compelled; etc. 

These are not reckoned in as conditions of the possession of the arts, except the bare knowledge; but as a condition of the possession of the virtues knowledge has little or no weight, while the other conditions count not for a little but for everything, i.e. the very conditions which result from often doing just and temperate acts.

What is this 'little or no weight'? The knowing of what is right isn't heavy here: even the worst man in the numbered scale above knows what is right, at least knows what the just law requires. Knowledge isn't very heavy in determining how virtuous you are if the very best and the very worst person have that in common.

Actions, then, are called just and temperate when they are such as the just or the temperate man would do; but it is not the man who does these that is just and temperate, but the man who also does them as just and temperate men do them. It is well said, then, that it is by doing just acts that the just man is produced, and by doing temperate acts the temperate man; without doing these no one would have even a prospect of becoming good.

As the practice of just acts becomes a habit, it will eventually become pleasurable because it becomes comfortable whereas stealing would then be uncomfortable: you can imagine how uncomfortable most men who are used to paying their own way would be with shoplifting. Perhaps as a child they might have wanted to take a piece of candy they couldn't pay for from the store; but as a man habituated to the justice of paying for his goods, they probably would never think of shoplifting, let alone do it.

But most people do not do these, but take refuge in theory and think they are being philosophers and will become good in this way, behaving somewhat like patients who listen attentively to their doctors, but do none of the things they are ordered to do. As the latter will not be made well in body by such a course of treatment, the former will not be made well in soul by such a course of philosophy.

In a way this is a restatement of the 'little or no weight' of knowledge to virtue. Knowing the philosophy about what is right counts for almost nothing in determining if you are virtuous. Your practices count for everything because they shape your internal character until it is fully formed.