"It is not enough to possess a good mind; one must make good use of it."

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

"The first precept was never to accept anything for true which I did not clearly know to be such."

"To be a good philosopher, one must be a good mathematician."

"The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge."