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.

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.

People almost always do great things without knowing how to do them, and are quite surprised to have done them.

Our sun enlightens the planets that belong to him; why may not every fixed star also have planets to which they give light?

Nature is never so admired as when she is understood.

A work of morality, politics, criticism will be more elegant, other things being equal, if it is shaped by the hand of geometry.

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.