In the past, Zhuang Zhou dreamed of a butterfly, which was a lifelike butterfly. He said that he was suitable for his ambition and did not know Zhou. Suddenly I feel like I'm in a state of confusion. I don't know that Zhou's dream is Hu Dieyu, and Hu Die's dream is Zhou Yu? Zhou and Hu Die must be different. This is called materialization. ("Zhuangzi·Equality of Things")