It is not enough to have a good mind. The main thing is to use it well.

I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake.

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.

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

In the matter of a difficult question it is more likely that the truth should have been discovered by the few than by the many.

[About Pierre de Fermat] It cannot be denied that he has had many exceptional ideas, and that he is a highly intelligent man. For my part, however, I have always been taught to take a broad overview of things, in order to be able to deduce from them general rules, which might be applicable elsewhere.

At last I will devote myself sincerely and without reservation to the general demolition of my opinions.