It is the assumption of this book that there is a typical human nature. It is the aim of this book to seek it. Just like a surgeon, a psychiatrist can make all sorts of basic assumptions when a patient lies down upon the couch. He can assume that the patient knows what it means to love, to envy, to trust, to think, to speak, to fear, to smile, to bargain, to covet, to dream, to remember, to sing, to quarrel, to lie. The 'smile' of a baboon is a threat; the smile of a man is a sign of pleasure: it is human nature, the world over.