The reading of all good books is like a conversation with the finest minds of past centuries.

Nothing is more fairly distributed than common sense: no one thinks he needs more of it than he already has.

If I found any new truths in the sciences, I can say that they follow from, or depend on, five or six principal problems which I succeeded in solving and which I regard as so many battles where the fortunes of war were on my side.

There is nothing so far removed from us as to be beyond our reach, or so hidden that we cannot discover it.

Intuitive knowledge is an illumination of the soul, whereby it beholds in the light of God those things which it pleases Him to reveal to us by a direct impression of divine clearness.

Mathematics is a more powerful instrument of knowledge than any other that has been bequeathed to us by human agency.

How do we know that anything really exists, that anything is really the way it seems ot us through our senses?