What is consciousness?

Is experience a brain process, an illusion, something extra, or something everywhere?

Physicalism: it will be explained

Consciousness is a physical process in the brain. The hard problem reflects the limits of our current concepts, not a gap in nature.

Best argument: Every past mystery about life and mind, from heredity to vitalism's 'life force', dissolved as science advanced. We already know that experience changes precisely with brain states: anaesthesia removes it, damage alters it, stimulation produces it. The simplest hypothesis is that experience is certain brain activity, described from the inside. An explanatory gap in our understanding does not imply a gap in the world.
Strongest objection: The comparison with vitalism fails. Life was always a matter of functions (metabolism, reproduction), so explaining the functions explained life. Consciousness is not obviously a function. One can imagine all the functions occurring without any experience, which is the point of philosophical zombies.
The reply: Physicalists reply that what we can imagine is a poor guide to what is possible, and that the sense of a remaining mystery may itself be explained by how our brains represent their own states.
Defended by: Daniel Dennett, Patricia Churchland, Ned Block

Phenomenal consciousness, as philosophers define it, does not exist. What needs explaining is why we are so convinced that it does.

Best argument: Keith Frankish and Daniel Dennett argue that our brains represent their own processing in a simplified, misleading way, as if there were ineffable inner qualities. The 'meta-problem' is to explain why we judge that we have such qualities. Solve that, and nothing is left over, because the qualities were never there.
Strongest objection: To most people this seems to deny the most obvious fact there is. If I am in pain, the pain is not an illusion; even an illusion of pain would be a painful experience. Illusionism seems to deny the very thing it was meant to explain.
The reply: Illusionists accept that pain is real and terrible; what they deny is a particular theory of it, namely that it has intrinsic, private, ineffable qualities over and above its role in the mind.
Defended by: Daniel Dennett, Keith Frankish

III

Conscious experience is not physical. It is a further feature of reality, linked to the brain but not identical to it.

Best argument: No amount of physical description seems to entail facts about experience. Mary in her black and white room knows every physical fact about colour vision, yet learns something new when she sees red. If so, there are facts beyond the physical facts. Chalmers proposes property dualism: experience is a fundamental property, as basic as mass or charge, linked to physical structure by psychophysical laws.
Strongest objection: If experience is non-physical, how does it affect the physical world? Your pain makes you say 'ouch', yet physics appears causally closed: every physical event has a sufficient physical cause. Dualism seems to make consciousness either a ghost that breaks physics or an idle spectator.
The reply: Some dualists accept that consciousness is causally idle (epiphenomenalism); others argue that physics only describes structure and leaves room for experience to be what fills that structure.
Defended by: David Chalmers, René Descartes, Frank Jackson (early)

Some form of experience is a basic feature of all matter. Brains do not create consciousness; they organise it.

Best argument: Physics tells us what matter does, never what it is in itself. Bertrand Russell and Arthur Eddington suggested that the intrinsic nature behind physical structure might be experiential. Then there is no mystery of how experience emerges from wholly non-experiential stuff, because it never does.
Strongest objection: The 'combination problem': how do countless micro-experiences combine into a single unified subject like you? Electrons with flickers of experience do not obviously add up to someone tasting coffee. Many also find the idea that a rock has an inner life simply implausible.
The reply: Panpsychists answer that most objects (rocks, chairs) are not subjects at all, only aggregates; only certain organised systems combine experience into a unified mind. The combination problem is real, they grant, but no harder than the hard problem.
Defended by: Philip Goff, Galen Strawson, Bertrand Russell

There is a natural explanation of consciousness, but human minds may be incapable of grasping it.

Best argument: Colin McGinn notes that every species has cognitive limits: a dog cannot understand calculus. It would be surprising if humans had no such limits, and consciousness is exactly where our concepts seem to fail.
Strongest objection: It is premature to declare defeat. Many problems once thought permanently beyond us were solved, and mysterianism risks discouraging the research that might solve this one.
Defended by: Colin McGinn

Is there a hard problem of consciousness?

Choose one to see how people answer.

For the full background, variations and open questions, read the entry: Why is there something it is like to be you?.