Some of my favorite passages from the Tao de Ching

Three powerful examples of tangible objects deriving their utility from what is not there:

The Wheel: Thirty spokes join a central hub, but the empty hole for the axle is what allows the wagon to move.

The Vessel: Clay is molded into a pot, but the emptiness inside is what actually holds whatever you want.

The Room: Walls and windows are built, but the inner space makes the room livable.