“昔者庄周梦為蝴蝶,栩栩然蝴蝶也,自喻适志与,不知周也。俄然觉,则蘧蘧然周也。不知周之梦為蝴蝶与,蝴蝶之梦為周与?週与蝴蝶则必有分矣。此之谓物化。”
Once Zhuangzi dreamt he was a butterfly, a butterfly flitting and fluttering around, happy with himself and doing as he pleased. He didn’t know he was Zhuangzi. Suddenly he woke up and there he was, solid and unmistakable Zhuangzi. But he didn’t know if he was Zhuangzi who had dreamt he was a butterfly, or a butterfly dreaming he was Zhuangzi. Between Zhuangzi and a butterfly there must be some distinction! This is called the Transformation of Things. (2, tr. Burton Watson 1968:49)
[source: http://en.wikipedia.org/wiki/Zhuangzi#The_butterfly_dream]