Though 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 VinciWhoever despises the high wisdom of mathematics nourishes himself on delusion and will never still the sophistic sciences whose only product is an eternal uproar.
Leonardo da VinciThose who are in love with practice without knowledge are like the sailor who gets into a ship without rudder or compass and who never can be certain whether he is going. Practice must always be founded on sound theory, and to this Perspective is the guide and the gateway; and without this nothing can be done well in the matter of drawing.
Leonardo da Vinci