A huge immobile mass, on which stands precarious figures. The slender figures, warped by an obscure anamorphosis, have been salvaged from the darkness, retrieved and figured. But something has slipped from the sculptor's grasp. It is as if we are being presented with, in the plinth, the weight of a materiality which has escaped figuration. The plinth becomes the very figuration of what cannot be figured.
The context in which this is mentioned is what Spurious names the ‘dark side of what is known’, that which we become aware of, however, only in the act of trying to know, or to represent:
Then it is a matter of what escapes human knowledge as it were in the very act of knowing. It is the dark side of what is known even as it seems to allow itself to be known. It is not sheer indeterminacy, but a kind of reserve or resistance in that which gives itself to be known or understood
Thus in Giacometti, this resistant X comes to bulk larger and larger in his sculptures. the gravity (in both senses) of what has been left behind looms larger that what has been brought back.
I thought, by contrast of Rodin, whose figures often seem by contrast to have been won, triumphantly, from the inertia of matter, or as if matter has found the form for which it was striving, Rodin has done violence to the material under his hand it but also pulled from it its own implicit forms. Rodin’s figures seem to complete the matter out of which, struggling, they arise.
In each case, the 'rift' between figure and ground is different. This rift is both aesthetic in consequence and, I suppose, ontological in implication.
See also Young Hegelian's comments, here. [I intend to update this post later]