Zhuang Zhou dreamed of butterflies: That is to say, Zhuangzi dreamed of butterflies, and so did normal people.
Butterfly dreamed of seeing Zhuang Zhou: Zhuangzi thought that the butterfly might have dreamed of Zhuang Zhou, and it was the butterfly that hit Zhuang Zhou's dream.
No one seems to regard Zhuang Zhou as a madman because he raised this question. On the contrary, everyone admits that he is a great philosopher. Philosophers and lunatics are different from normal people, but they are different from normal people in different characteristics. Crazy people can't understand some basic common sense, for example, they can't distinguish dreams from reality like normal people, so they will encounter serious obstacles in their daily life. Philosophers fully understand the meaning of common sense, but they are not satisfied with common sense like normal people. Instead, we should get to the bottom of the common sense that everyone takes for granted and ask if it is really reasonable.
According to common sense, no matter what dreams I have, dreams are just dreams. When I wake up, I will return to real life, which is by no means a dream. However, the philosopher insisted: How do you know that the former is a dream and the latter is not a dream? What makes you distinguish between dreams and reality?
Don't underestimate this question, it's really not easy to answer. You might say that you can tell which dreams are and which are real by feeling. For example, the feeling in the dream is very vague, and the feeling after waking up is very clear; Things in dreams are often changeable and lack logic, while things in reality are relatively stable and coherent; People will wake up sooner or later in their dreams, but they can't wake up when they wake up, and so on. However, philosophers will ask you, are your feelings really that reliable? Sometimes you have this dream. The feeling is so clear and vivid that you don't know that you are dreaming and think that everything in your dream is true. So, how do you know that the whole life you experience when you are awake will not be a dream of this nature, but it will last longer? In fact, in most dreams, you really don't know that you are dreaming, and you won't find it was a dream until you wake up. So, is it because you haven't woken up from this big dream that you don't know that your waking life is also a dream? Is there really a principle difference between dreaming and waking up?
From this perspective, the question raised by Zhuang Zhou seems absurd, but it is actually a very important philosophical question. The question is: does this phenomenal world we perceive through our senses really exist? Zhuang Zhou is obviously skeptical about this. In his view, since we feel something that doesn't exist in our dreams, which proves that our feelings are very unreliable, the existence of ourselves and the world around us that we feel when we wake up is probably an illusion, an illusion like a dream.