Mein Kampf by Adolf Hitler

Generally speaking a man should not publicly take part in politics before he has reached the age of thirty, though, of course, exceptions must be made in the case of those who are naturally gifted with extraordinary political abilities. That at least is my opinion to-day.

And the reason for it is that until he reaches his thirtieth year or thereabouts a man's mental development will mostly consist in acquiring and sifting such knowledge as is necessary for the groundwork of a general platform from which he can examine the different political problems that arise from day to day and be able to adopt a definite attitude towards each. A man must first acquire a fund of general ideas and fit them together so as to form an organic structure of personal thought or outlook on life--a WELTANSCHAUUNG. Then he will have that mental equipment without which he cannot form his own judgments on particular questions of the day, and he will have acquired those qualities that are necessary for consistency and steadfastness in the formation of political opinions. Such a man is now qualified, at least subjectively, to take his part in the political conduct of public affairs.