Since happiness is an activity of soul in accordance with perfect virtue, we must consider the nature of virtue; for perhaps we shall thus see better the nature of happiness.
This answers some of the objections that have been raised in the comments. We have now a definition of happiness, but it entails a definition of virtue. We need to study the virtues now, in order to better understand even the defined concept of "happiness."
The true student of politics, too, is thought to have studied virtue above all things; for he wishes to make his fellow citizens good and obedient to the laws.As an example of this we have the lawgivers of the Cretans and the Spartans, and any others of the kind that there may have been. And if this inquiry belongs to political science, clearly the pursuit of it will be in accordance with our original plan.
Emphasis added. The student of politics isn't studying virtue to make himself better, note, but to make his fellow citizens good and obedient to the laws. This is a point of discontinuity between Aristotle and American society, and to some degree between the Modern world and Aristotle. Americans think of virtue as a private matter. The function of the law is not to make us good people, but to set the most minimal limits possible on human behavior in order to enable us to be free within those limits. What we choose to do with that freedom is where we find out whether or not we are virtuous. It isn't anyone else's business.
Among the other Moderns, a less-strong version of this idea prevails. Kant, for example, divides his Metaphysics of Morals into two Doctrines: the Doctrine of Right, and the Doctrine of Virtue. The dividing point between those two is whether or not the state has the right to use physical force against you to require you obey. The Doctrine of Right is where force is permitted -- interestingly, marriage law is included here -- and the Doctrine of Virtue is where no one is allowed to force you to do the right thing. There is still a right thing, but it is yours to decide whether to be good or bad.
That is not true for Aristotle. As we will see when we reach his discussion of Justice, the point of the laws is to mandate virtuous behavior, to make everyone behave as if they were virtuous. You may not get genuinely virtuous people that way, but you at least get a society in which people are treating each other as if they were the virtuous people they aren't really.
Aristotle also wants people to develop the internal virtues, and to come to that point we have already discussed in which they want to be virtuous and find it pleasant to be. However, virtue is a matter of habituation; being forced to be better for a while can help you internalize the habits, and at least takes care of some of the bad behavior.
But clearly the virtue we must study is human virtue; for the good we were seeking was human good and the happiness human happiness. By human virtue we mean not that of the body but that of the soul; and happiness also we call an activity of soul.
Thus, this will not be a book on weightlifting or fast running, but on courage and justice.
But if this is so, clearly the student of politics must know somehow the facts about soul, as the man who is to heal the eyes or the body as a whole must know about the eyes or the body; and all the more since politics is more prized and better than medicine; but even among doctors the best educated spend much labour on acquiring knowledge of the body. The student of politics, then, must study the soul, and must study it with these objects in view, and do so just to the extent which is sufficient for the questions we are discussing; for further precision is perhaps something more laborious than our purposes require.
Socrates would have taken this and made a problem out of it for showing that the inquiry wasn't working well. Aristotle manfully accepts that we have to understand the subordinate questions in light of our inquiry into the prior questions. This is a difference between him and his predecessors.
This is a longer chapter, so I will put the rest after a jump break. There's an important new concept here, so don't skip it.



