Chapter 10
Thirty spokes converge upon a single hub; it is in the emptiness at the center that the usefulness of the wheel lies.
Clay is shaped to form a vessel; it is in the emptiness within that the usefulness of the vessel lies.
Doors and windows are cut out to make a room; it is in the emptiness within that the usefulness of the room lies.
Thus, presence provides the conditions for benefit; absence provides the capacity for function.