For those colours which you wish to be beautiful, always first prepare a pure white ground.

A day will come in which men will look upon an animal's murder the same way they look today upon a man's murder.

In life beauty perishes, but not in art.

Many will think they may reasonably blame me by alleging that my proofs are opposed to the authority of certain men held in the highest reverence by their inexperienced judgments; not considering that my works are the issue of pure and simple experience.

The supreme misfortune is when theory outstrips performance

He who is fixed to a star does not change his mind.

We know more about the movement of celestial bodies than about the soil underfoot.