One day Zhuangzi and Huizi are strolling on Bridge Hao.
Zhuangzi : "Look how happy the fish are just swimming around in the river."
Huizi : "How do you know they are happy? You are not a fish."
Zhuangzi: "And you are not me. How do you know I don't know the fish are happy?"
Huizi: "Of course I'm not you, and I don't know what you think;
But I do know that you're not a fish, and so you couldn't possibly know the fish are happy."
Zhuangzi: "Look, when you asked me how I knew the fish were happy,
you already knew that I knew the fish were happy.
  I knew it from my feelings standing on this bridge.