The great body of population dynamics, like those of the motion of the celestial bodies, can be solved—and what is most remarkable, there is a surpri… - Adolphe Quetelet

Expect not... that efforts for the moral regeneration of man can be immediately crowned with success; operations upon masses are ever slow in progress, and their effects distant.

We both call in experience to the support of our opinions; but, in your case, the experience is based on vague uncertainties, whilst I, more circumspect, strive never to lose sight of those scientific principles which ought to guide the observer in all his investigations. My aim is not to defend systems, or bolster up theories; I confine myself to the citation of facts, such as society presents to our view. If these facts be legitimately established, it follows that we must accept of and accommodate our reason to them.

Little by little his conversation, always instructive and animated, gave a special direction to my tastes, which would have led me by preference towards letters. I resolved to complete my scientific studies and followed the courses in advanced mathematics given by M. [Jean Guillaume] Gamier. It was at the same time agreed by us that, in order to relieve him in his work, I should give some of the other courses with which he was charged. I thus found myself his pupil and his colleague.