Nineteen Eighty-Four: George Orwell

Doublethink:
To know and not to know, to be conscious of complete truthfulness while telling carefully constructed lies, to hold simultaneously two opinions which canceled out, knowing them to be contradictory and believing in both of them, to use logic against logic, to repudiate morality while laying claim to it, to believe that democracy was impossible and that the party was guardian of democracy, to forget, whatever it was necessary to forget, then to draw it back into memory again at the moment it was needed, and then promptly forget it again, and above all to apply the same process to the process itself-that was the ultimate subtlety: consciously to include unconsciousness, and then, once again, to become unconscious of the act of hypnosis you had just performed. Even to understand the word "doublethink" involved the use of doublethink.
- George Orwell.