Slashdot

Thirty spokes line the wheels hub, but it is the center hole that makes it useful.

Mold clay into a vessel, it is the emptiness inside that makes it useful.

Cut windows and doors for a house, it is the emptiness within that makes them useful.

Therefore profit comes from what is there, usefulness from what is not there.

Tao te Ching (11) - (retranscribed)