We join spokes together in a wheel,

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.  -  Tao de Ching