It must not be thought that it is ever possible to reach the interior earth by any perseverance in mining: both because the exterior earth is too thick, in comparison with human strength; and especially because of the intermediate waters, which would gush forth with greater impetus, the deeper the place in which their veins were first opened; and which would drown all miners.

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

The first precept was never to accept a thing as true until I knew it as such without a single doubt.

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

There is a little gland in the brain in which the soul exercises its functions in a more particular way than in the other parts.

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

Intuition is the undoubting conception of a pure and attentive mind, which arises from the light of reason alone, and is more certain than deduction.