Zhuang Zhou once had a dream in which he turned into a butterfly. He flew through the air, feeling like a truly free and spirited creature.
In the dream, he was delighted and exhilarated, unaware that this butterfly was merely a figment of his dream. After a while, he awoke to find himself as Zhuang Zhou once more, not a butterfly. He was astonished and could not tell whether he had dreamed of becoming a butterfly, or a butterfly was now dreaming of being him.