Oricine îşi susține un argument prin apelarea la o autoritate nu îşi foloseşte inteligența; el îşi utilizează doar memoria. - Leonardo da Vinci

If you condemn painting, which is the only imitator of all visible works of nature, you will certainly despise a subtle invention which brings philosophy and subtle speculation to the consideration of the nature of all forms — seas and plains, trees, animals, plants and flowers — which are surrounded by shade and light. And this is true knowledge and the legitimate issue of nature; for painting is born of nature — or, to speak more correctly, we will say it is the grandchild of nature; for all visible things are produced by nature, and these her children have given birth to painting. Hence we may justly call it the grandchild of nature and related to God.

May it please our great Author that I may demonstrate the nature of man and his customs, in the way I describe his figure.

Shadow is not the absence of light, merely the obstruction of the luminous rays by an opaque body. Shadow is of the nature of darkness. Light is of the nature of a luminous body; one conceals and the other reveals. They are always associated and inseparable from all objects. But shadow is a more powerful agent than light, for it can impede and entirely deprive bodies of their light, while light can never entirely expel shadow from a body, that is from an opaque body.