"Thirty spokes are joined together in a wheel,
but it is the center hole
that allows the wheel to function.

We mold clay into a pot,
but it is the emptiness inside
that makes the vessel useful.

We fashion wood for a house,
but it is the emptiness inside
that makes it livable.

We work with the substantial,
but the emptiness is what we use." - Lao Tzu (老子)