Many spokes share the wheel's hub;
but it is the center hole that allows it to turn.
Shape clay into a vessel;
It is the empty space within that makes it useful.
Hammer wood to build a house,
the inner space is what makes it livable.
Cut doors and windows for a room;
It is the holes that make it usable.
Therefore benefit comes from what is there;
Usefulness from what is not there.
We work with being,
but non-being is what we use.