With me, everything turns into mathematics.

Archimedes, that he might transport the entire globe ... demanded only a point that was firm and immovable; so also, I shall be entitled to entertain the highest expectations, if I am fortunate enough to discover only one thing that is certain and indubitable.

Give me extension and motion and I will construct the universe.

The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.

Variant: When it is not in our power to follow what is true, we ought to follow what is most probable.

Here I beg you to observe in passing that the scruples that prevented ancient writers from using arithmetical terms in geometry, and which can only be a consequence of their inability to perceive clearly the relation between these two subjects, introduced much obscurity and confusion into their explanations.

The greatest minds are capable of the greatest vices as well as of the greatest virtues.