Chapter 39 explained simply

39. 1. The things which from of old have got the One (the Tao) are-- Heaven which by it is bright and pure; Earth rendered thereby firm and sure; Spirits with powers by it supplied; Valleys kept full throughout their void All creatures which through it do live Princes and kings who from it get The model which to all they give. All these are the results of the One (Tao). 2. If heaven were not thus pure, it soon would rend; If earth were not thus sure, 'twould break and bend; Without these powers, the spirits soon would fail; If not so filled, the drought would parch each vale; Without that life, creatures would pass away; Princes and kings, without that moral sway, However grand and high, would all decay. 3. Thus it is that dignity finds its (firm) root in its (previous) meanness, and what is lofty finds its stability in the lowness (from which it rises). Hence princes and kings call themselves 'Orphans,' 'Men of small virtue,' and as 'Carriages without a nave.' Is not this an acknowledgment that in their considering themselves mean they see the foundation of their dignity? So it is that in the enumeration of the different parts of a carriage we do not come on what makes it answer the ends of a carriage. They do not wish to show themselves elegant-looking as jade, but (prefer) to be coarse-looking as an (ordinary) stone.