"I have never made any discoveries that were not based on the certainty of mathematics."

"The greatest good for man is to live according to reason."

"I confess that I have never found in my experience that anything which I once clearly understood could afterwards be called into doubt by me."

"It is not enough to know, one must also apply; it is not enough to wish, one must also do."

"The whole of philosophy is like a tree, whose roots are metaphysics, whose trunk is physics, and whose branches are all the other sciences."