As an opening statement of the Tao Te Ching, Lao-tzu simply acknowledges the limitations of our language. Such limitation of language is well recognized in philosophy.
Lao-tzu introduces Heng Tao and Heng Names as the order of nature and the proper descriptions of the myriad things. Lao-tzu begins by saying that we can discuss this order, but our words cannot fully describe Heng Tao. We can use names (Wu and Yu) to describe the nature of the myriad things, but these names cannot fully describe the nature of the myriad things.
The proper order of the myriad things as manifested in the phenomenal world should reflect the principle of Tao. We often call this order of the myriad things as “the manifestations of Tao.” We may say that the manifestations of Tao reflect the principle of Tao. We may also say that the principle of Tao is revealed in the manifestations.
For our logic discussion, the reality of Tao defines a “whole domain,” and, in this whole domain, Wu and Yu are sub-domains. The principle of Tao is the way we use Wu and Yu to represent Tao. If we understand how Lao-tzu describes this order in the next few verses, we can identify his principle.