The Uses of Not

Thirty spokes
Meet in the hub,
Where the wheel isn't
Is where it's useful.

Hollowed out,
Clay makes a pot.
Where the pot's not
Is where it's useful.

Cut doors and windows
To make a room.
Where the room isn't,
There's room for you.

So the profit in what is
Is in the use of what isn't.

~~Lao Tzu