All our knowledge hast its origins in our perceptions โฆ In nature there is no effect without a cause โฆ Experience never errs; it is only your judgments that err by promising themselves effects such as are not caused by your experiments โฆ Science is the observation of things possible, whether present or past; prescience is the knowledge of things which may come to pass.
Leonardo da VinciAnd you who wish to represent by words the form of man and all the aspects of his membrification, relinquish that idea. For the more minutely you describe the more you will confine the mind of the reader, and the more you will keep him from the knowledge of the thing described. And so it is necessary to draw and to describe.
Leonardo da VinciThough I may not . . . be able to quote other authors, I shall rely on that which is much greater and more worthy - on experience.
Leonardo da Vinci