Human subtlety will never devise an invention more beautiful, more simple or more direct than does nature because in her inventions nothing is lacking, and nothing is superfluous.
Leonardo da VinciPainting is concerned with the ten things you can see: these are darkness and brightness, substance and color, form and place, remoteness and nearness, movement and rest.
Leonardo da VinciAvoid the precepts of those thinkers whose reasoning is not confirmed by experience.
Leonardo da VinciWe must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.
Leonardo da Vinci