Long ago, Zhuang Zhou dreamt he was a butterfly. He fluttered gaily, in a butterfly way, all to his pleasure, following his whims ! He did not know Zhou. Suddenly he woke up, and at once was Zhou again. But he did not know whether he was Zhou dreaming he was a butterfly, or a butterfly dreaming it was Zhou. Yet, between Zhou and the butterfly, a distinction must be made. This is called the transformation of things.