How do you know?

One day Zhuangzi, a follower of Laozi, stood on a bridge with a friend. Gazing at the fish below, Zhuangzi spoke of the joy of a fish’s knowledge, which was true union with the Tao, living life as an uncarved block.

His friend said: "How do you know what a fish knows? You are not a fish."

To which Zhuangzi, replied: "How do you know what I know? You are not me."