Thirty spokes share one hub — in ancient times, a cart had thirty spokes, symbolizing the number of months. Sharing one hub means there is a hole in the center, so many spokes converge toward it. Those who cultivate themselves should eliminate emotions and desires, making the five internal organs empty and void so the spirit will return to them. Those who govern a country should have few abilities, unifying many weak individuals into strength. It is precisely because of the emptiness within that the function of the cart exists — the hub is hollow so the wheel can rotate; the carriage body is hollow so people can ride in it. Knead clay to make vessels — Shan means to mix; Zhi means earth or soil. Mix the clay to make vessels for food and drink. It is precisely because there is emptiness that a vessel can be used — because the interior is empty, it can hold and receive things. Chisel doors and windows to make a room — meaning building a house or dwelling. It is precisely because of emptiness that the function of a room exists: doors and windows are empty, allowing people to enter and exit; the interior is empty, so people can live there. Therefore, "having" provides benefit — benefit refers to objects useful in form and function. When there is something inside a vessel or people within a room, one fears the structure being damaged; when the abdomen contains spirit, one fears losing its form. It is "emptiness" that allows for use — it is precisely the void that allows one to hold and receive all things. Therefore, the formless can control the tangible. The Dao is emptiness.