Once upon a time,
Chuang Tzu dreamed that he was a butterfly,
flying about enjoying itself.
It did not know that it was Chuang Chou. Suddenly he awoke,
and veritably was Chuang Chou again.
He did not know whether it was Chuang Chou dreaming that he was a butterfly,
or whether it was the butterfly dreaming that it was Chuang Chou.
Between Chuang Chou and the butterfly there must be some distinction.
This is a case of what is called the transformation of material things.