The Uses of Not

The Taoist philosopher Lao Tse wrote extensively on  the concept of "Ma" including his poem "The Uses of Not":

Thirty spokes meet in the hub,

but the empty spaces between them

is the essence of the wheel.

Pots are formed from clay,

but the empty between it

is the essence of the pot.

Walls with windows and doors form the house,

but the empty space within it

is the essence of the house.