Virtue is said to be hitting the mark, and rightly so. But we must ask: how can one find where the mark is which one should to aim at? How can we know, exactly, what we should be shooting for? We want both to have the right intentions, and, moreover, to actually carry them out.

Things which are correct obey a rational principle, they follow a right rule. This means they stand in proportion to other things. We already covered this when we talked about justice. There we said that a person ought to get profits from a business in proportion to how much they put into it. For instance, if each person were to put up half the money and do half the work then they should get half the profit. The rule here is that what you get out should be proportional to what you put in.

Now, in order for things to get put in proportion, they must be measured with some standard unit (e.g. meters). We have to have a sense of how much of something there is in order to know whether or not it is in proportion. And to hit the mark, we must learn to adjust our efforts so that we do not do too much or too little, but rather how much we do ends up in proportion with how much is actually needed. Suppose that we are preparing a sweet dish that calls for honey. There is a certain amount of sweet taste that we want to have. To have that, we have to put in the right amount of honey: we have to have the right proportion based on how many servings we are making. This correct proportion will be measured according to some standard (e.g. by the spoonful). If it is too sweet by some amount, then we reduce how much we use by our estimate and then see how that improves things. We might imagine, for instance, the correct proportion to be one spoonful per serving.

Again, the standard both helps us to form up our aim and tell by how far off we are, so that we can correct ourselves.

Having talked about the standard, let us now talk about the right rule.

We would not know which medicine to use if someone were to give us a catalog of medicines, and then say: "Use the same one that a doctor would." Well, a doctor does not just prescribe any medicine to anyone simply because it is generally prescribed for this or that. No, a doctor must deal with each patient and the conditions that apply to that patient especially; and the doctor must prescribe based on the principles of the medical art (which they gain through a long study of many cases). So it is also with the virtues, we have to not only know what is the right thing to do in the general case (e.g. avoid drinking too much), but we must also get the rule by which we can tell whether what we did was right or wrong in the specific case (e.g. whether we can pass a sobriety test), and we must have the standard by which we can measure (e.g. the number of drinks we have).

Before we said that there are two kinds of virtues: intellectual and moral. So far we have been talking about moral virtues. Now let us go into the intellectual virtues. And what is the difference between one's morals and one's intellect? Morals are about what one believes is good, generally speaking. For instance, one may generally believe that it is good to help out a friend in need (liberality). But morals do not, by themselves, tell us what specifically we should do. Of course, morals also do not tell us how to do a particular thing (e.g. how much we should give to this friend who is in this condition), though we may have good habits that work just fine most of the time.

Our morality is not, by itself, enough for us to be good. Our intellects, however, are something with which which we can work out the specifics and particulars of each case, so that we know just what to do. Intellect is about, for instance, figuring out what it would mean to do the liberal thing for this specific friend of ours in this specific situation (e.g. figure out what kind of help they need and how much they need). Intellect is about finding a path to an end (e.g. give them money directly or set them up with another friend who can help). So, if we want to actually be good in the many tricky situations that come up in life, we must investigate the intellect.

Since the intellect is closely wrapped up with the soul, let us say a few words about the soul first. At the end of Book One, we showed how the soul can be broken down into the rational and the irrational part. Now let us further break down the rational part. Each part of the soul has different kinds of things that it thinks about (i.e. its objects). For instance, the appetitive part thinks about food, so we say food is an object of the appetitive part. The virtuous mean (i.e. doing things right and good) is an object of the rational part.

Inside the rational part there are two pieces, and each of those is about another kind of object. The first part is the scientific. The second part is the calculative.

The calculative works with things like mathematics and logic. It deals with things which we can always count on to be true (e.g. a triangle will always have its angles add up to 180 degrees, no matter what). The scientific, on the other hand, works with things that we can well see to be true most of the time, though there are particular cases which are exceptions to the rule. Again, for the things which the calculative part deals with, whatever makes them be what they are will never change; these are invariable things. Once we know that the angles of a triangle add up to 180 degrees, we can use that whenever we deal with triangles, and do calculations based on it. There is no special case of triangles where the 180 degree rule does not hold. But Nature is different than Math. Nature is always surprising us even when things seem to be certain. The scientific part of the soul is what deals with things like Nature, which we cannot be absolutely certain about, variable things. Now, before we were talking about which medicine to give which patient. In the case where we know what ails the patient and we know what is the rule to follow, then we use our calculative faculty to figure out how much this particular patient should get. But let us also take the case where we get a patient and do not know what ails them (and Nature does often surprise us with new diseases). Here we must use the scientific part of our mind to investigate the symptoms and figure out what is the cause of the disease. This can vary. The two patients may present with the same basic symptoms, but the cause of those symptoms may vary, they may have two different diseases. Again, there we would use our scientific faculty to figure out what disease each patient has.

Now, how do these relate to finding the mark and being virtuous? Which will help us to know, for example, how much money to give, so as to be liberal? In the next chapter, we will look at what each part of the soul (viz. the calculative and the scientific) does when it is working at its best, and then figure out what that can best be used for (viz. its function). In Book One we did this, when we asked what it is that humans do especially over other animals. There we said that humans use reason to see what good there is to be done and do it. So likewise here, we will figure out what each part of the soul does especially well and what is the use of doing it especially well. Once we know that, we can then see how that part of the soul relates to virtue as a whole.