In the last verse, Lao-tzu tells us how we can see the mysteries of Tao. The mystery of Tao shows equally in the appearances of Heng Wu and Heng Yu.
Lao-tzu characterizes such mysteries as xuan 玄, which means dark, obscure, and indistinct, etc. These manifestations are obscure, because they cannot be identified with any distinct object in our mind.
We translate xuan as mysterious or profound. This profoundness can be shown analytically in our logic structure, where xuan is the keyword that describes conceptually a “complementary” state of Wu and Yu without clear separation. When we describe the manifestations, our words will appear to be vague, fuzzy, indeterminate and self-contradictory. Therefore, Lao-tzu emphasizes that the mystery of Tao as found in both manifestations are profoundness upon profoundness.
We may now conclude our discussion of this Chapter. We have identified several keywords that should be carefully interpreted to show the logic of Tao philosophy. This includes Tao, Heng, Wu and Yu (Names), Heng Wu and Heng Yu (Heng Names), objects, manifestations of Tao, profoundness, principle of Tao, etc. We have to use these terms carefully in our discussion of logic. These terms are listed in the Appendix, with other important terms.