What is "Xuan"? The concept of "Xuan" was first seen in Laozi: "Tao can be Tao, but it is extraordinary. The name can be named. It's very famous. Nameless, the beginning of heaven and earth; Fame is the mother of everything. Therefore, there is often no desire to see its wonders; There is always a desire to watch. Both of them have different names. They are both called Xuan. Mysterious and mysterious, the gate of Wan Qi. " Later, the definition of "Xuan" was even more. Wang Bi's "A Brief Introduction to Laozi" said: "The deep one is also deep." Zhang Heng said: "Mysterious and invisible things are the roots of nature; If you start from scratch, you can do it first; Including morality, building Gankun. " Shuowen interprets "Xuan" as "You Yuan". Those black and red ones are mysterious, just like those that are hidden and covered. Su Zhe's note in the Song Dynasty: "Anyone who is far away from everything must have dark black. So Lao Tzu often sends mysterious messages.
In fact, the original meaning of the word "Xuan" is subtle. Laozi regards "Xuan" as an abstract noun concept, which has the same meaning as the concepts of "Tao", "Nothing" and "Being". "Being the same mystery" means "being the same" and "being the same". The correct interpretation of "both have different names, both are called metaphysics, and both are called metaphysics" should be: ("you" and "nothing") both have different names because of "Tao"; The "same" is called "Xuan"; Similarity and sameness are the keys to understanding Tao. The phrase "the mysterious is the door of Wan Qi" means that it is also the way to understand everything in the world. Special emphasis is placed on "similarity", so it can also be said that similarity and sameness are the key to understanding everything in the world.
Therefore, it can be said that metaphysics is the universal law "Tao" of all things in the world, which is the same as "Tao". "Xuan" is the ontology that generates all things in the universe, which embodies the infinite metaphysics of all things.