It is true that zeal is the soul of the virtues, but most certainly, Monsieur, it must be according to knowledge, as Saint Paul says; that means: according to knowledge of experience. And because young people ordinarily do not possess this experiential knowledge, their zeal goes to excess, especially in those who have a natural asperity.
Correspondence, Conferences, Documents: Correspondence; January 1640-July 1646) (ed. 1990) - ISBN: 9780911782790