The scientific approach to a fact is to explain it, not to ignore or dismiss it, so accepting the first fact makes consciousness a valid subject for science. The question the hard problem raises is:
“Why does conscious experience exist?” (Chalmers, 1996)(p5)
Those who argue that the universe is a machine so consciousness can’t exist must also agree that they are machines, so why should we listen only to them? A detailed review of theories on consciousness divides them exhaustively into six categories A-F (Chalmers, 2003):
A. Materialism-A. Consciousness doesn’t exist except as an imagined effect of the physical brain (Dennett, 1991). If physical causes explain everything, there is nothing beyond the physical brain that needs explaining, so the hard problem doesn’t exist.
B. Materialism-B. Consciousness exists but is identical to certain physical brain states for all practical purposes (Block & Stalnaker, 1999). If consciousness equates to physical states, the hard problem is solved.
C. Materialism-C. Consciousness exists but is a physical derivative of the brain in theory (Nagel, 1974) (Edelman, 2003). If physical causes explain everything, they will one day explain consciousness so the hard problem will be solved, eventually.
The above theories argue that consciousness arises from a physical process because physical realism is correct. Yet it isn’t easy to argue that the observer experience is imaginary (A) or that it equates to matter states (B), so most believers in physical realism are left hoping that a miracle will one-day derive consciousness from matter.
D. Dualism-D. Consciousness exists by itself to cause physical events and physical events in turn cause consciousness (Stapp, 1993). If consciousness exists apart from matter to explain what it can’t, the hard problem is solved.
E. Dualism-E. Consciousness is a brain by-product that helps survival but doesn’t affect physical reality (Zizzi, 2003). If consciousness is just an epiphenomenon of physical activity, the hard problem is solved.
F. Neutral Monism-F. Consciousness is an intrinsic property of reality just as matter is. If both consciousness and matter have the same primal cause, the hard problem is solved.
These theories argue that consciousness is a non-physical reality. Dualism lets consciousness affect matter from a non-physical realm (D), Dualism-E lets it exist but have no effect on matter, and neutral monism (F) sees both consciousness and matter as derivative, but as Chalmers notes:
“No-one has yet developed any sort of detailed theory in this class, and it is not yet clear whether such a theory can be developed.” (Chalmers, 2003)
Quantum realism is therefore a neutral monism but first, we consider physical realism.