Given the cause nature produces the effect in the briefest manner that it can employ.
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 VinciObstacles cannot crush me. Every obstacle yields to stern resolve. He who is fixed to a star does not change his mind.
Leonardo da Vinci