After twelve lines of pure negation, chapter fourteen ends with an instruction that is entirely concrete: hold to the ancient way in order to manage what is present, and to know the ancient beginning is called the thread of the way.
The turn is abrupt and it is the most important thing in the chapter. Having established that the subject cannot be seen, heard, held or named, the text does not conclude that nothing can be done with it. It concludes that it can be used, and specifically that it can be used to handle current affairs.
That combination, an object of knowledge that is entirely indescribable and entirely practical, is the characteristic position of this book. It is not offering a mystery to contemplate. It is offering something to work with, and its refusal to describe that something is not a devotional gesture but a claim that the description would not help.
The word rendered as thread carries the sense of a guiding line running through a sequence, and it is the same idea as the mother of chapter fifty-two, held on to while knowing the children, and the one of chapter thirty-nine, attained by heaven, earth, spirits, valleys and rulers alike. In each case a single continuity is claimed to run through everything and to be graspable at any point in it.
Whether that is a metaphysical claim or a recommendation about how to pay attention is not something the text decides.