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 is not.

Lao Tzu, Tao Te Ching, Verse 11
Translated by Ursula K. Le Guin