The Tao that can be spoken is not the eternal Tao. The name that can be named is not the eternal name. The nameless is the origin of Heaven and Earth. The named is the mother of myriad things. Thus, constantly without desire, one observes its essence. Constantly with desire, one observes its manifestations. These two emerge together but differ in name. The unity is said to be the mystery. Mystery of mysteries, the door to all wonders.