Notes on Nicomachean Ethics
Book 1 Part 3
Our discussion will be adequate if it has as much clearness as the subject-matter admits of, for precision is not to be sought for alike in all discussions, any more than in all the products of the crafts.
It’s an important Aristotelian concept that not all sciences have the same precision. At one hand, you have mathematics, and at the other hand, probably rhetoric or something similar. Medicine is in the not precise realm.
Now fine and just actions, which political science investigates, admit of much variety and fluctuation of opinion, so that they may be thought to exist only by convention, and not by nature.
Here, Aristotle gives the goal, the good of political science, which is the fine and just action. It’s of couse also the goal of ethics on an individual level. He suggests here that we might think those things are conventional instead of natural. Natural here means from reason or according to some nature of men. It’s an argument that is often made, that morality cannot be objective because there is a lot of diversity in it.
for before now men have been undone by reason of their wealth, and others by reason of their courage. We must be content, then, in speaking of such subjects and with such premisses to indicate the truth roughly and in outline,
So things that are usually considered good like wealth and courage can sometimes give bad outcome, along with the diversity of things, means that the subject of behavior can only be vague and about the most cases, not some absolute. It’s a low definition science.
or it is the mark of an educated man to look for precision in each class of things just so far as the nature of the subject admits; it is evidently equally foolish to accept probable reasoning from a mathematician and to demand from a rhetorician scientific proofs.
Ironically, “educated” people today are clueless about this and will ask mathematical precision for vague things, which just proves their lack of education. It can be seen often in debates. It’s a strategy some people use to pretend to win, by asking for quotes and rote memory things. It’s a sad state of affair and if people had read this text, maybe they would not do it, or maybe they would but people would know they are uneducated.
Now each man judges well the things he knows, and of these he is a good judge. And so the man who has been educated in a subject is a good judge of that subject, and the man who has received an all-round education is a good judge in general.
Experts are usually good for their expertise, but better educated people are good in general.
Hence a young man is not a proper hearer of lectures on political science; for he is inexperienced in the actions that occur in life, but its discussions start from these and are about these; and, further, since he tends to follow his passions, his study will be vain and unprofitable, because the end aimed at is not knowledge but action.
Usually University students disagree with this. But they don’t know and that’s the point. But now we have a small redefinition of the goal, that it is not about “knowing” the right target, but it’s about the action of aiming. That’s pretty important, especially in a US Protestant-led culture, where “values” are portrayed as virtues. Because those values are simply the end, and young people can get that. They can be ideologues and have all the right values. But ethics is about action. And it’s not something you can learn by discussing. Either you know the action or you don’t. Old people do, so they have an advantage over the young. They can discuss those things they know.
And it makes no difference whether he is young in years or youthful in character; the defect does not depend on time, but on his living, and pursuing each successive object, as passion directs. For to such persons, as to the incontinent, knowledge brings no profit; but to those who desire and act in accordance with a rational principle knowledge about such matters will be of great benefit.
Now Aristotle clarifies, it is not really youth itself that is the problem, it’s more one of character. People that simply follow their passions never learn, no matter how long they live. So for those people, learning about ethics is useless. It kind of goes against what Socrates was saying, that evil is done by ignorance. Aristotle will say it’s more a question of having unruly passions.
These remarks about the student, the sort of treatment to be expected, and the purpose of the inquiry, may be taken as our preface.
So far the introduction explained for who the book is, the type of science it is and the goal of the inquiry. Hedonists who are looking for absolute values will be disappointed.

Not sure I completely understand, but I guess he's saying young people have ideas, not actions (experiences) and we cannot reduce politics or the discuss of morals into absolutes, for there is no absolute answer. It's not only the inability to accept vaugenes and ambiguity but also the inability to keep communal good or the good of the state above one's individual good, which hedonist individual lacks. And therefore, not all are ready to study or discuss this.
Hope I'm getting it right :p