What does it mean that children are not fish, but the pleasure of amphetamines?

original text

Zhuangzi and Keiko swim in Haoliang (1). Zhuangzi said, "Fish swim leisurely and have fun." Keiko said, "You are not a fish. How can you know that fish are happy?" ? Zhuangzi said, "You are not me. How do you know that I don't know that fish are happy?" " ? " Keiko said: "I am not a son, I really don't know my son;" Zi Gu is not a fish, but he doesn't know the happiness of fish. " Zhuangzi said, "Please follow this book. Confucius said,' You know a lot about fish', and he asked me because he knew what I knew. I know it very well. "

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Zhuangzi and Keiko play together on Haoshui Bridge. Zhuangzi said: "How leisurely the white mackerel swims, which is the happiness of the fish." Keiko said, "If you are not a fish, how do you know the happiness of the fish?" Zhuangzi said, "If you are not me, how do you know that I don't know the happiness of fish?" Keiko said, "I'm not you, although I don't know you;" You are not a fish, you don't know the happiness of fish, which is completely certain. " Zhuangzi said, "let's stick to the previous words. You just said' how do you know the happiness of fish', that is, you already know that I know the happiness of fish. Ask me, I know the happiness of fish on a good water bridge. "