Tao Te Ching Chapter 11

Thirty spokes unite around the nave;

From their not-being (loss of their individuality)

Arises the utility of the wheel.

Mold clay into a vessel;

From its not-being (in the vessel's hollow)

Arises the utility of the vessel.

Cut out doors and windows in the house (-wall),

From their not-being (empty space) arises the utility of the house.

Therefore by the existence of things we profit.

And by the non-existence of things we are served.

Tao Te Ching