How many things rely for their definition -- whether in whole or in part -- on what they are not?
I think many things may be like this -- relying on the earnest descriptions of what they are not and yet gob-stoppered or wildly and ineptly garrulous when it comes to saying what they actually are. Any honest evaluation of what such things are dribbles through the fingers like a fistful of water.
Maybe it's all a bit like what the Supreme Court Justice said about pornography (approximately): "I may not know what it is, but I know it when I see it."
This is useful to know, I think. If the only -- or perhaps most frequently employed -- way of saying what something is is to depict what it is not, then how reliable is saying what it is not in saying what it is? And if you can't say what it is and if you can't reliably say what it isn't ... well, maybe it's all porn.
I'm not interested in this as a philosophy exam test question. I just think it's useful on a personal level.