Lao-tzu uses Wu and Yu as the conventional starting points to describe the true nature of the myriad things.
In Verse 2, we note that Lao-tzu associates both Wu and Yu with the nature of the myriad things. Lao-tzu defines Wu and Yu as two opposite views on the myriad things, with the following definitions:
- Wu, as the origin, does not show any differentiation (appearance) of the individual things, so the myriad things are considered to be the same.
- Yu, as the mother, shows all things with clear differentiation, so the myriad things are considered Each thing has a clear boundary.
Therefore, Wu and Yu are two conventionally well-defined and distinct dualistic concepts. These two conventional objects, Wu and Yu, represent the opposite ways of describing the orders of the myriad things. In such a dualistic framework, the myriad things are either the same (Wu) or different (Yu). Wu and Yu are the concepts of “sameness” and the “difference” in the descriptions of the myriad things.
The “true” relationship of the myriad things cannot be Wu or Yu. Wu and Yu by themselves are not realistic. However, Wu and Yu are two simple concepts that we understand and share, so we can use Wu and Yu as useful objects in our discussion of the true relationship.
 In the Mawangdui version, both Wu and Yu are associated with the myriad things. This shows the scope of Tao as the philosophy of nature. In Wang Bi’s version, Wu is defined as the “origin of Heaven and Earth” instead of the “origin of the myriad things.”