Thirty spokes converge on the wheel's hub. But the center emptiness of the hole which allows the wheel to function.

We make a vessel from a lump of clay; It is the empty space within the vessel that makes it useful.

We cut out doors and windows to make a house; and it's on inner spaces where there's nothing that the usefulness of the house depends.

Thus, while the tangible has advantages, It is the intangible that is for usefulness.useful.

 第十一章用無利有

三十輻，共一轂，當其無，有車之用。埏埴以為器，當其無，有器之用。鑿戶牖以為室，當其無，有室之用。故有之以為利，無之以為用。

[譯文]

三十根輻條連接一個車轂之上, 有了車轂中空的部分，才有車的使用。和泥制成器皿，也恰恰是由于有器皿其中空部分，才有器皿的使用。建造房屋，開鑿門窗，亦是由于門窗及四壁構成的空間，才有房屋供人使用。

因此，顯現(xiàn)有形的宇宙萬物給人帶來便利，而無形的空才是獲得使用價值的基礎。