Chapter 16 explained simply

16. 1. The (state of) vacancy should be brought to the utmost degree, and that of stillness guarded with unwearying vigour. All things alike go through their processes of activity, and (then) we see them return (to their original state). When things (in the vegetable world) have displayed their luxuriant growth, we see each of them return to its root. This returning to their root is what we call the state of stillness; and that stillness may be called a reporting that they have fulfilled their appointed end. 2. The report of that fulfilment is the regular, unchanging rule. To know that unchanging rule is to be intelligent; not to know it leads to wild movements and evil issues. The knowledge of that unchanging rule produces a (grand) capacity and forbearance, and that capacity and forbearance lead to a community (of feeling with all things). From this community of feeling comes a kingliness of character; and he who is king-like goes on to be heaven-like. In that likeness to heaven he possesses the Tao. Possessed of the Tao, he endures long; and to the end of his bodily life, is exempt from all danger of decay.