As astronomy is the daughter of idleness, geometry is the daughter of property.

A well-cultivated mind is, so to speak, made up of all the minds of preceding ages; it is only one single mind which has been educated during all this time.

A philosopher will not believe what he sees because he is too busy speculating about what he does not see.

Leibniz never married; he had considered it at the age of fifty; but the person he had in mind asked for time to reflect. This gave Leibniz time to reflect, too, and so he never married.

We must always skim over pleasures. They are like marshy lands that we must travel nimbly, hardly daring to put down our feet.

It is the passions that do and undo everything.

Mathematicians are like lovers. Grant a mathematician the least principle, and he will draw from it a consequence which you must also grant him, and from this consequence another.