How do we know that anything really exists, that anything is really the way it seems ot us through our senses?
Rene DescartesThe reading of all good books is indeed like a conversation with the noblest men of past centuries who were the authors of them, nay a carefully studied conversation, in which they reveal to us none but the best of their thoughts.
Rene DescartesBut I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming.
Rene Descartes