Now do you not see that the eye embraces the beauty of the whole world? It counsels and corrects all the arts of mankind... it is the prince of mathematics, and the sciences founded on it are absolutely certain. It has measured the distances and sizes of the stars it has discovered the elements and their location... it has given birth to architecture and to perspective and to the divine art of painting.

Every action needs to be prompted by a motive. To know and to will are two operations of the human mind. Discerning, judging, deliberating are acts of the human mind.

Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.

Men of genius sometimes accomplish most when they work least, for they are thinking out inventions.

Just as eating against one's will is injurious to health, so studying without a liking for it spoils the memory, and it retains nothing it takes in.

Avoid the precepts of those thinkers whose reasoning is not confirmed by experience.

Thirst will parch your tongue and your body will waste through lack of sleep ere you can describe in words that which painting instantly sets before the eye.