Because reason...is the only thing that makes us men, and distinguishes us from the beasts, I would prefer to believe that it exists, in its entirety, in each of us.

Each problem that I solved became a rule, which served afterwards to solve other problems.

Except our own thoughts, there is nothing absolutely in our power.

It is contrary to reasoning to say that there is a vacuum or space in which there is absolutely nothing.

There is nothing more ancient than the truth.

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

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