You can think of it as a shadow cast by the subconscious over consciousness or as the shadow cast by the conscious over subconsciousness. Either way we all die, either way there's a polarity or a duality and either way consciousness requires a borrowed understanding and a shared definition. A man called Robert Lawrence Kuhn, not that nice man Thomas 'paradigm' Kuhn, but Robert 'I'm fabulous' Kuhn who amongst other things is an Investment Banker, a television personality and an expert on China, concluded that a world taxonomy of consciousness would have to include nearly three hundred theories of consciousness. The majority of those theories suggest a duality. Why bother? I'll tell you. Jung, in a very Immanuel 'let's not bother to prove this' Kantian way, decided we people shared a collective unconsciousness out of which it was possible to extract archetypes. As a result Jung was able to see a polarity between the conscious and subconscious, and out of this polarity he was able to usefully address neurosis, which I, without any evidence, suspect Jung preferred to think of as hysteria. Strictly speaking a monist theory of consciousness would be obliged to posit a universal consciousness, that would include plants, galaxies, the universe, everything. A monist theory would consider the end of the universe as the completion of the whole and the return to unity. So, as it stands, the big bang was our moment of birth, then when the universe reaches a limit to expansion, gravity pulls us back to our beginning and we end in the belly of a massive black hole. As a dying man I'm coming to the end of my ability to tolerate living in a shadow and I'm pretty damn sure my subconscious is too which is basically why neither of us gives a hoot for straight lines any longer.