"The thirty spokes converge at one hub, but the utility of the cart is a function of the nothingness inside the hub. We throw clay to shape a pot, but the utility of the clay pot is a function of the nothingness inside it. We bore out doors and windows to make a dwelling, but the utility of the dwelling is a function of the nothingness inside it. Thus, it might be something that provides the value, but it is nothing that provides the utility."

----- Dao De Jing - Chapter 11

(Recommended by Patrick Pujda)