Formerly, I, Zhuang Zhou, dreamt that I was a butterfly, a butterfly flying about, feeling that it was enjoying itself. I did not know that it was Zhou. Suddenly I awoke, and was myself again, the veritable Zhou. I did not know whether it had formerly been Zhou dreaming that he was a butterfly, or whether it was now a butterfly dreaming that it was Zhou. But between Zhou and a butterfly there must be a difference. This is a case of what is called the Transformation of Things.