Accordingly, seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us; and because some men err in reasoning, and fall into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for demonstrations; and finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep, while there is at that time not one of them true, I supposed that all the objects (presentations) that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams. But immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the sceptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search.
~ Discourse on Method, René Descartes
Finally Pilate began to take offense. Although she was hampered by huge ignorances, but not in any way unintelligent, when she realized what her situation in the world was and would probably always be she threw away every assumption she had learned and began at zero. First off, she cut her hair. That was one thing she didn’t want to have to think about anymore. Then she tackled the problem of trying to decide how she wanted to live and what was valuable to her. When am I happy and when am I sad and what is the difference? What do I need to know to stay alive? What is true in the world? Her mind traveled crooked streets and aimless goat paths, arriving sometimes at profundity, other times at the revelations of a three-year old. Throughout this fresh, if common, pursuit of knowledge, one conviction crowned her efforts: since death held no terrors for her (she spoke often to the dead), she knew there was nothing to fear.
~ Song of Solomon, Toni Morrison
He picked up the children’s history book and looked at the portrait of Big Brother which formed its frontispiece. The hypnotic eyes gazed into his own. It was as though some huge force were pressing down upon you – something that penetrated inside your skull, battering against your brain, frightening you out of your beliefs, persuading you, almost, to deny the evidence of your senses. In the end the Party would announce that two and two made five, and you would have to believe it. It was inevitable that they should make that claim sooner or later: the logic of their position demanded it. Not merely the validity of experience, but the very existence of external reality, was tacitly denied by their philosophy. The heresy of heresies was common sense. And what was terrifying was not that they would kill you for thinking otherwise, but that they might be right. For, after all, how do we know that two and two make four? Or that the force of gravity works? Or that the past is unchangeable? If both the past and the external world exist only in the mind, and if the mind itself is controllable — what then?
~ Nineteen Eighty-Four, George Orwell