When the world is ruled according to the Way, the ghosts lose their power. The ghosts do not really lose their power, but it is not used to harm people.
Clay is fashioned into vessels; it is on their empty hollowness that their use depends. Doors and windows are cut out to make a dwelling, and on the empty space within, its use depends. Thus, while the existence of things may be good, it is the non-existence in them that makes them serviceable.
Softness triumphs over hardness, feebleness over strength. What is more malleable is always superior over that which is immoveable. This is the principle of controlling things by going along with them, of mastery through adaptation.
Without going outside, you may know the whole world, without looking through the window, you may see the ways of heaven. The farther you go, the less you know. Thus the sage knows without traveling; he sees without looking; he works without doing.