The “happiness of fish” refers to a story in the Zhuangzhi, which is a Chinese book (c. 286 BCE), and one of the foundational texts of Taoism. The story consists of a dialog between Chuang Tzu and Hui Tzu, Most of the Zhuangzi passages portray Hui Tzu (or Hui Shi) as a rival of Zhuangzi. Hui Shi acts as an intellectual opponent – he argues the alternative viewpoint, or criticizes the Taoist perspective, and his arguments are often laced with humor. The following famous story of the Zhuang-Hui dialogues concerns the subjectivity of happiness, and whether we can know anything about other subjects.
Chuang Tzu and Hui Tzu were strolling along the dam of the Hao River when Chuang Tzu said, “See how the minnows come out and dart around where they please! That’s what fish really enjoy!”
Hui Tzu said, “You’re not a fish – how do you know what fish enjoy?”
Chuang Tzu said, “You’re not I, so how do you know I don’t know what fish enjoy?”
Hui Tzu said, “I’m not you, so I certainly don’t know what you know. On the other hand, you’re certainly not a fish ‑ so that still proves you don’t know what fish enjoy!”
Chuang Tzu said, “Let’s go back to your original question, please. You asked me how I know what fish enjoy ‑ so you already knew I knew it when you asked the question. I know it by standing here beside the Hao.”
IN: Watson, Burton (1964): Chuang Tzu: Basic Writings. New York: Columbia University Press. Page 17.