"What Is Man?" is a short story by American writer Mark Twain, published in 1906. It is a dialogue between a Young Man and an Old Man regarding the nature of man. This was Twain's most serious, philosophical and private book. He kept it locked in his desk, considered it to be his Bible, and spoke of it as such to friends when he read them passages. He had written it, rewritten it, was finally satisfied with it, but still chose not to release it until after his death. It appears in the form of a dialogue between an old man and a young man who discuss who and what mankind really is and provides a new and different way of looking at who we are and the way we live. Anyone who thinks Twain was not a brilliant philosopher should read this book. We consider ourselves as free and autonomous people, yet this book puts forth the ideas that 1) We are nothing more than machines and originate nothing - not even a single thought; 2) All conduct arises from one motive - self-satisfaction; 3) Our temperament is completely permanent and unchangeable; and 4) Man is of course a product of heredity, and our future, being fixed, is irrevocable -- which makes life completely predetermined