The usefulness of a pot comes from its emptiness.
We join spokes together in a wheel,
But it is the center hole
That makes the wagon move.
We shape clay into a pot,
But it is the emptiness inside
That holds whatever we want.
We hammer wood for a house,
But it is the inner space
That makes it livable.
We work with being,
But non-being is what we use.
(Source: Lao Tzu—Tao Te Ching)