If the Great Way perishes there will morality and duty. When cleverness and knowledge arise great lies will flourish. When relatives fall out with one another there will be filial duty and love. When states are in confusion there will be faithful servants.
The Tao gives birth to One. One gives birth to yin and yang. Yin and yang give birth to all things... The complete whole is the complete whole. So also is any part the complete whole... But forget about understanding and harmonizing and making all things one. The universe is already a harmonious oneness; just realize it.
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.