Another Dream in the East

In the Fantasy Realm, cherished by countless beautiful dreams, there are also joy and sorrow, happiness and grief, infatuation and resentment. All it takes is one bout of laughter, and as you watch and listen, it all ends up as yet another great dream. This dreamlike world is wondrous beyond compare, and should exist only in fantasy. Yet Zhuang Zhou dreamed he was a butterfly, so how could he know the butterfly hadn't dreamed it was him?