You can only know consciousness or experiencing if you what is is different to, out of what background it has come to be. What is the not or absence of experiencing? If you think of death as you imagine it to be the absolute nothing, absence of all experiencing as, say, under a general anaesthetic - although that is only an idea arising in consciousness. This is so overdetermined by conscious constructs as to be entirely misleading. Whatever it is that is the not of consciousness is as present an all-pervading as consciousness, and is precisely not the background in any sense, because it is not prefigured in any way. Consciousness is the making-unsurprising of not-consciousness, and so not-consciousness is the utter surprising of consciousness!