Let us resume our inquiry and state, in view of the fact that all knowledge and every pursuit aims at some good, what it is that we say political science aims at and what is the highest of all goods achievable by action. Verbally there is very general agreement; for both the general run of men and people of superior refinement say that it is happiness, and identify living well and doing well with being happy; but with regard to what happiness is they differ, and the many do not give the same account as the wise. For the former think it is some plain and obvious thing, like pleasure, wealth, or honour; they differ, however, from one another- and often even the same man identifies it with different things, with health when he is ill, with wealth when he is poor; but, conscious of their ignorance, they admire those who proclaim some great ideal that is above their comprehension. Now some thought that apart from these many goods there is another which is self-subsistent and causes the goodness of all these as well. To examine all the opinions that have been held were perhaps somewhat fruitless; enough to examine those that are most prevalent or that seem to be arguable.Let us not fail to notice, however, that there is a difference between arguments from and those to the first principles. For Plato, too, was right in raising this question and asking, as he used to do, 'are we on the way from or to the first principles?' There is a difference, as there is in a race-course between the course from the judges to the turning-point and the way back. For, while we must begin with what is known, things are objects of knowledge in two senses- some to us, some without qualification. Presumably, then, we must begin with things known to us. Hence any one who is to listen intelligently to lectures about what is noble and just, and generally, about the subjects of political science must have been brought up in good habits.* For the fact is the starting-point, and if this is sufficiently plain to him, he will not at the start need the reason as well; and the man who has been well brought up has or can easily get starting points. And as for him who neither has nor can get them, let him hear the words of Hesiod:Far best is he who knows all things himself;Good, he that hearkens when men counsel right;But he who neither knows, nor lays to heartAnother's wisdom, is a useless wight.
This 'resuming our inquiry' or 'beginning again' is something that Aristotle likes to do. In Physics I, he lays out a whole system for thinking about how motion is possible and explicable, only to reject it as inadequate and start again with a new approach in Physics II. Yet the inquiry in the first book was worthwhile; without it, you would not have noticed or understood the things that were necessary to the second start.
Here we are not setting aside the first three parts of the book, but rather framing them as similarly necessary prefaces for the inquiry that can now begin in earnest. You really needed all three of those prefaces to understand what follows.
Another thing that Aristotle likes to do in the beginning of his inquiries is to give us an account of the opinions of the Wise. This often includes poetics, as here. Sometimes we are told the names of people who held the various opinions, and sometimes not. What he is good about is giving an account of the field he is entering as it stands at the time of his entry. We know what has been thought so far; he will then tell us briefly what is wrong with it, and then begin to try to resolve the problems identified with the existing Wise opinion.
So here we get the first real problem of the Ethics: the Wise say that happiness is the goal of both ethics and political science.** However, they disagree about what 'happiness' entails. So before we can go very far, we have to determine what this happiness is that we are aiming at as our target.
* Here is an opportunity to engage with one of my own teachers, Professor Iakovos Vasiliou, currently at CUNY. When I knew him he was a young man starting out as a professor at Georgia State University in Atlanta (which, I notice, his biography no longer mentions). He wrote an early paper on the role of the good upbringing that Aristotle mentions in passing here that is a good introduction to the world of students that Aristotle was engaging himself, and to the Greek culture of the time. You should be able to access the text as an independent researcher, if you wish; you can also try Academia.com if JSTOR didn't work for you.
** It is important to grasp that Aristotle intends these two sciences to have the same end because they are meant to be aligned with each other. A 'science' in ancient Greece is not a modern science, because there was no scientific method like ours; it is, rather, a unified field of study. Ethics is the science of proper behavior for a human being, which is -- we have just learned -- pointed at maximizing human happiness (however that ends up being defined). Political Science is the science of organizing a community of human beings in such a way that they can all best pursue their individual goods, i.e., that very same happiness that is the end of ethics. Politics is supposed to grow out of ethics in this way, and a good politics can be judged from a bad one by whether and to what degree it supports the end of their ethics for the people of the community.