Chapter sixteen begins with an instruction and then supplies an observation to justify it. Reach the limit of emptiness, hold fast to stillness; the ten thousand things rise together, and I watch their return.
The observation is agricultural and unmysterious. Things grow, flourish and go back to where they came from, and each returns to its root. The chapter names that going back stillness, and names the stillness a return to what was allotted.
Return is one of the book's organising ideas, stated most compactly in chapter forty, where returning is called the movement of the way. It is not a doctrine of rebirth and not a cyclical cosmology of ages. It is closer to a claim about the shape of any process: what rises subsides, and the subsiding is not a failure of the rising but its completion.
The position from which this is seen matters as much as what is seen. The chapter puts the observer at the limit of emptiness and holding to stillness, which is not a vantage point that could be occupied by someone in the middle of the rising and falling. What is being described is a way of watching, and the content of what is watched is almost secondary.
Knowing that constant, the chapter says, is called clarity. Not knowing it, people act blindly and come to harm, which is the only threat the chapter makes.