Chuang Tzu and Hui Tzu were walking next to the River Hao one evening when the following discussion occured.
Chuang Tzu: Look! Look at those fish swimming around so close to the surface and doing as they please. That is what fish really enjoy!
Hui Tzu: You aren't a fish. How can you say you know what a fish enjoys?
Chuang Tzu: You aren't me, so how can you know that I don't know what a fish enjoys?
Hui Tzu: I am most certainly not you, so I don't know what you know; You are definitely not a fish, so you don't know what a fish enjoys. So, there.
Chuang Tzu: Wait. Let's go back to the question, if you don't mind. You asked how I could know what a fish really enjoys. You already knew that I knew when you asked. I know by being here at the River Hao.
(paraphrased from The Book of Chuang Tzu translated by Palmer and Breuilly)