Laotzu's Tao and Wu Wei, by Dwight Goddard and Henri Borel, , at sacred-texts.com
Although the wheel has thirty spokes its utility lies in the emptiness of the hub. The jar is made by kneading clay, but its usefulness consists in its capacity. A room is made by cutting out windows and doors through the walls, but the space the walls contain measures the room's value.
In the same way matter is necessary to form, but the value of reality lies in its immateriality.
(Or thus: a material body is necessary to existence, but the value of a life is measured by its immaterial soul.)