Ursula K. Le Guin
Thirty spokes meet in the hub. Where the wheel isn’t is where it’s useful.
Hollowed out, clay makes a pot. Where the pot’s not is where it’s useful.
Cut doors and windows to make a room. Where the room isn’t, there’s room for you.
So the profit in what is is in the use of what isn’t.
Note UKLG: One of the things I love about Lao Tzu is he is so funny. He’s explaining a profound and difficult truth here, one of those counter-intuitive truths that, when the mind can accept them, suddenly double the size of the universe. He goes about it with this deadpan simplicity, talking about pots.