Aristotle's insult

Hence the young man is not a fit student of Moral Philosophy, for he has no experience in the actions of life, while all that is said presupposes and is concerned with these: and in the next place, since he is apt to follow the impulses of his passions, he will hear as though he heard not, and to no profit, the end in view being practice and not mere knowledge.

And I draw no distinction between young in years, and youthful in temper and disposition: the defect to which I allude being no direct result of the time, but of living at the beck and call of passion, and following each object as it arises. For to them that are such the knowledge comes to be unprofitable, as to those of imperfect self-control: but, to those who form their desires and act in accordance with reason , to have knowledge on these points must be very profitable.

Ethics Book I