"Lao Tzu was able to teach the Tao because he not only could let the Tao guide him and have direct experience of the Tao, but also was able to introduce and utilize the powerful coupling concepts of Non-Being and Being to describe and teach the Tao, so that he knew what he taught and knew how to teach for sure. And this is the main reason for Lao Tzu to be the greatest teacher of the Tao in the history."