Tao te ching verse 11

Thirty spokes connect to the wheel's hub;
yet, it is the centre hole that makes it useful.
Clay is shaped into a vessel;
yet, it is the emptiness within that makes it useful.
Doors and windows are cut for a room;
yet it is the space where there is nothing that makes it useful.
Therefore, though advantage comes from what is;usefulness comes from what is not.