The two questions at the centre of chapter fifteen are the practical heart of it. Who can be muddy and let stillness slowly bring it to clarity? Who can be at rest and let movement slowly bring it to life?
The first image is exact and worth taking literally. Silt water clears if it is left alone, and it does not clear if it is stirred, filtered in haste or worked at. The clearing is not something anyone does; it is what happens when nothing is done. That is as compact a statement of the book's central practical claim as it contains anywhere, and unlike most of the paradoxes it describes a process anyone can observe in a bucket.
The second question reverses the terms and is less often quoted. Stillness produces clarity, and then something has to come out of the clarity, which the chapter describes as being slowly brought to life. Non-action is not a terminus.
The chapter closes on a line that connects both to the rest of the book: one who holds to this does not want to be full, and because he is not full he can be worn out and renewed rather than replaced. The refusal of fullness is chapter nine's argument about the brimming vessel, and the preference for what can be worn and renewed over what is complete runs through to chapter twenty-two, where being worn out is listed among the advantages.