Thirty spokes on a cartwheel
Go towards the hub that is the center
— but look, there is nothing at the center
and that is precisely why it works!
If you mold a cup you have to make a hollow:
it is the emptiness within that makes it useful.
In a house or a room it is the empty spaces
— the doors, the windows — that make it usable.
They all use what they are made of
to do what they do,
but without their nothingness they would be nothing.
---Tao Te Ching, Chapter 11---