There are three classes of people: those who see, those who see when they are shown, those who do not see.
Leonardo da VinciAnyone who invokes authors in discussion is not using his intelligence but his memory.
Leonardo da VinciWhy does the eye see a thing more clearly in dreams than the imagination when awake?
Leonardo da VinciAll our knowledge hast its origins in our perceptions … In nature there is no effect without a cause … Experience never errs; it is only your judgments that err by promising themselves effects such as are not caused by your experiments … Science is the observation of things possible, whether present or past; prescience is the knowledge of things which may come to pass.
Leonardo da Vinci