Once upon a time, there lived a philosopher named Chuang Chou, who dreamed vividly that he was a butterfly. He thought that he was indeed a butterfly, and he totally forgot that he had been so-called Chuang Chou. Later when he woke up, he found himself turning into Chuang Chou again. His body, hands and legs, was none other than himself. Thus he wondered, "Which one is the real me? Am I the man, Chuang Chou, who dreamed of turning into a butterfly, or the butterfly becoming a man in its dream?"