Clay is fashioned into vessels; but it is on their empty hollowness that their use depends. You don't want the glass or the brass or the clay, when you buy a vessel, you want the empty space, or capacity to carry liquid. The thing itself is worth nothing, but its ability, or emptiness, to receive what is worth having. Man is worth nothing. His ability to receive insight is worth everything. The door and windows are cut out (from the walls) to form an apartment; but it is on the empty space (within), that its use depends.
The way of Gautama Sakyamuni is called the "middle way;" for it avoids extremes. One pair of extremes is that of the outright pursuit of worldly desires, on the one hand, and the severe, ascetic, bodily discipline of such contemporaries of the Buddha as the Jainas, on the other, whose austerity was disigned to culminate in annihilation of the physical frame.