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."
Chuang Tzu (Zhuangzi) – translated by Burton Watson
Image links to its source at metmuseum.org
The Pleasure of the Fishes - Zhou Dongqing, late 13th century