Consciousness is…
Consciousness is brain activity.
Consciousness is an emergent property of neural networks.
Consciousness is an emergent property of predictive coding in the brain.
Consciousness is an emergent property of multi-scale brain connectivity.
Consciousness is an emergent property of energy flow and information exchange in neural circuits.
Consciousness is an emergent property of information integration across the universe.
Consciousness is an illusion.
Consciousness is the brain's way of modelling itself.
Consciousness is a computational process.
Consciousness is integrated information.
Consciousness is the electromagnetic field of the brain.
Consciousness is synaptic resonance.
Consciousness is global neuronal workspace activation.
Consciousness is biological feedback loops.
Consciousness is a recursive self-model.
Consciousness is a byproduct of language evolution.
Consciousness is a linguistic/social construction
Consciousness is reflexive awareness.
Consciousness is a simulation.
Consciousness is pure information.
Consciousness is the body's way of integrating sensory data.
Consciousness is the sum of adaptive cognitive modules.
Consciousness is a field (like electromagnetism).
Consciousness is a torsion field effect in spacetime.
Consciousness is matter becoming aware of itself.
Consciousness is a fundamental property of the universe.
Consciousness is an evolutionary adaptation for social coordination.
Consciousness is the Bayesian brain generating probabilistic models of the world.
Consciousness is a neural correlate of attention.
Consciousness is a state-dependent pattern of thalamo-cortical oscillations.
Consciousness is a dynamical system near criticality (edge of chaos).
Consciousness is the functional integration of distributed cortical networks.
Consciousness is an epiphenomenon of metabolic processes in neurons.
Consciousness is a computational bottleneck for serial information processing.
Consciousness is the brain's solution to the credit assignment problem.
Consciousness is the dynamic binding of disparate neural signals into unified perception.
Consciousness is the result of high-dimensional attractor states in neural networks.
Consciousness is the synchronisation of gamma wave activity across brain regions.
Consciousness is a form of virtual reality generated by the brain for action selection.
Consciousness is a constraint-satisfaction process optimising for coherence.
Consciousness is the capacity for meta-cognition and error monitoring.
Consciousness is wavefunction collapse? No, that would be woo-woo [link TBD].
What, exactly, is consciousness?
What does it do?
How, why and when did it evolve?
How is it related to physical reality?
As you can see from the list above, there is no shortage of suggestions as to what consciousness is – and these are just a selection of the sort which are at least trying to sound scientific. This is the biggest unsolved mystery in science, and it is a mystery like no other. Can you think of another example of a thing (if “thing” is the right word), which the majority of people agree is in need of some sort of a scientific explanation, but for which there is no consensus as to whether it really exists, let alone what it is?
The abundance and variety of “Consciousness is X” statements reflects a widespread belief that if only we can find the correct physical X then the job will be done, or at the very least we will be able to start the work of putting flesh on what is finally the right set of bones. But while the search for X continues in every nook and cranny people can dream up, far less attention is paid to the precise meaning of the other two words (“consciousness” and “is”).
What sort of statements are these supposed to be? Are they definitions? Are they theories? Or are they something else entirely? This is crucial, for the simple reason that if we do not have a stable and widely accepted definition of X then our prospects of arriving at a stable and widely accepted theory of X are negligible. If they are intended as definitions then they must be rejected, simply because they do not accurately reflect the way people actually use the word “consciousness”. When we say “consciousness” we don't mean “brain activity”, and that applies to everybody, including physicalists. If we did, then the statement “Consciousness is brain activity” would take on the meaning “Brain activity is brain activity”, which communicates nothing at all, and isn't what is meant by the people who say it. We actually use the word “consciousness” to refer to subjective experiences: our own personal experience of reality, and that of other people and at least some other animals. This requires a private ostensive definition: we “mentally point” to our own conscious experiences and associate the word “consciousness” with all of that. Then, if we want to avoid solipsism, we must presume our intuition is correct: that we share a reality with other conscious beings. These statements, therefore, do not work as definitions.
We must therefore presume that they are at least trying to be theories, but superficially resembling theories does not qualify them as actual theories. That would need much more than just an X – the X itself can't amount to theory unless there is also a detailed explanation what the word “is” is supposed to mean. Since consciousness very obviously isn't identical to brain activity or any of the other X's on this list, they are all just vague hypotheses which don't adequately address the central question. If you are claiming X is Y, but X prima facie very different to Y, and your theory consists of nothing more than the single word “is”, then you don't actually have a theory. A theory of consciousness must coherently and unambiguously explain how consciousness is related to everything else that exists (and brains in particular). Furthermore, if we want to claim the theory is scientific rather than metaphysical then presumably that must include how it is related to the material world, and I say “presumably” because science and materialism are not the same thing, even though they've been joined at the hip for four centuries.
However, the mere act of asking such a question sets up another major problem: if we're saying that there is a relationship between consciousness and brain activity, and that that relationship isn't one of identity then we've introduced a concept which is both non-material by definition, and which also refers to something which we have acknowledged the existence of. In other words, if consciousness is something material then what else can it possibly be except for brain activity? Materialism is the claim that only material things exist, so if consciousness has a relationship with brain activity, and the relationship isn't one of identity, then materialism cannot be true. The only relationship between consciousness and brain activity which is consistent with materialism is identity. “Is” needs to mean “is identical to”, or materialism collapses.
Philosopher David Chalmers has called this “the Hard Problem of Consciousness”: the problem of explaining how it is possible for consciousness to “arise” or “emerge” from the physical architecture of a living brain. Chalmers' own formulation of this problem involves what he calls “philosophical zombies” (p-zombies) – imaginary entities which behave exactly like humans at all times, but which experience nothing at all. He argues that the very conceivability of such entities should be telling us that the physical facts are never going to be enough to account for consciousness.
While I agree wholeheartedly with Chalmers' conclusion, I cannot accept his argument. I can't conceive of a p-zombie because by definition they behave like ordinary humans at all times, which means that if you asked one whether it is conscious it would necessarily reply with something like “Of course I am! Why are you even asking me that?” In other words, I can't imagine a zombie that believes it is conscious. It might be convincingly human in some respects ...but so are large language models (AIs). However, it would not be capable of understanding consciousness or anything that depends upon it, or at least not like a conscious being understands those things. It would actually say something like “Consciousness? I have never been able to understand what that word is supposed to mean.”, in which case it wouldn't be a p-zombie, because that is not how normal humans talk.
My own formulation of the Hard Problem makes clear that the problem is not just hard but impossible. The only sort of material world we can directly know, and can be absolutely certain exists in the form it appears to exist, is the one we are consciously aware of. I am certain that I am directly aware of a material world. I presume it is in some way derived from a real, mind-external objective reality, but I cannot be certain what form that world exists in. Could it be non-material? Could it be information, for example? We have no grounds for ruling such a thing out. Therefore, from our own perspective, the only material world we can be certain about exists within consciousness. The Hard Problem is therefore the task of explaining consciousness in terms of a material world when their relationship in the reality as we experience is the other way around.
This line of reasoning has historically led people to non-materialistic metaphysical positions which grant a foundational role for consciousness in the structure of reality – usually some kind of idealism, dualism or panpsychism, all of which solve the Hard Problem by claiming that consciousness has been present in some form since the beginning. Unfortunately, this just sets up yet another unsolvable problem. Scientists may not be able to agree what consciousness is, but that doesn't prevent us from finding a lot of correlations between the contents of consciousness and specific structures and processes in brains (Chalmers calls these the “easy problems”). In other words, we are justified in believing that brains are necessary for consciousness, even if they are insufficient (i.e. even if something else is also necessary). It is not possible to reconcile this with the idea that consciousness has been present since the beginning, unless brains were also there at the beginning, which nobody is proposing. This is one of the primary reasons that none of these non-materialistic metaphysical positions has been able to mount a serious challenge to physicalism. They don't offer a secure foundation for a new science of consciousness, and it is difficult to see how they ever could. All three predate the Scientific Revolution, and if any of them are to sustain a future paradigm shift, then we are in need of a convincing explanation as to what brains are for. Brains are too complex and too biologically expensive to be a mere receiver of a complex signal coming from some unknown source via some unknown mechanism. If that is the way reality works, then what is cognition for? Another suggestion is that the brain is a “filter” for even more complex information, but the details are missing and it is not a great fit for the empirical evidence.
Consciousness, therefore, is not merely an unsolved problem for science; it is an unframed one – a profound gap in the architecture of science itself. The roots of this omission lie in the origins of modern science. The methodological revolution of the 17th century succeeded by excluding consciousness. Galileo and Descartes both argued that objective reality must be defined in terms of mathematical quantities – length, mass, velocity, and force – leaving subjective experience to philosophy or theology. This strategic division allowed physics to flourish, but it came at a cost: the subjective domain of experience was bracketed off as scientifically intractable. Cartesian dualism created a conceptual firewall between mind and matter, and for centuries the physical sciences developed exclusively on one side of it.
For the full refutation of materialism and physicalism go here.
I must emphasise that the Hard Problem arises specifically within the context of a materialist or physicalist ontology. For dualists, idealists, and other non-physicalists, consciousness is either fundamental to reality or systematically accounted for (even if this causes other serious problems). In contrast, physicalism must attempt to explain how consciousness arises from an ontology that explicitly excludes it at the outset. In this light, “hard” becomes a euphemism for “impossible” but rejecting physicalism does not automatically offer a viable way forward, because there is no consensus on an alternative. Existing responses to acceptance of the intractability of the Hard Problem can be categorised as follows:
Some philosophers and cognitive scientists have responded to the Hard Problem by denying the existence of consciousness altogether. Eliminative materialists contend that our intuitions about subjective experience are systematically mistaken and that a mature neuroscience will dispense with consciousness as a theoretical entity. While logically consistent, this position is deeply counter-intuitive and self-defeating. It sacrifices the undeniable reality of experience to preserve the coherence of materialism.
In contrast, idealist theories assert that consciousness is the fundamental substrate of reality, with the physical world emerging from or within it. This position has a long philosophical lineage and has gained renewed attention in recent years, but idealism continues to face significant resistance, largely because it appears to minimise the ontological status of the physical world and invites the problematic implication of disembodied minds: that consciousness can exist independently of any physical substrate, brains included.
Panpsychism proposes that consciousness is a ubiquitous feature of the natural world, present to some degree in all matter. Rather than emerging from complex arrangements of non-conscious parts, consciousness is posited as a fundamental property akin to mass or charge. This view attempts to bridge the explanatory gap by denying that consciousness must "emerge" at all. While panpsychism has gained increasing traction as dissatisfaction with physicalism grows, it suffers from its own counter-intuitive implications. Do people really believe that rocks are conscious? The answer is usually that rocks are conscious in a very different way to humans, but most of us cannot bring ourselves to believe that rocks experience anything at all. Panpsychism also struggles to explain how micro-experiences combine to form unified macro-experiences – a version of the Binding Problem.
A final position holds that consciousness “emerges” from sufficiently complex arrangements of matter. This form of emergentism attempts to preserve materialist commitments while acknowledging the novelty of consciousness, but doesn't get us any closer to a coherent explanation. To assert that a radically different ontological category (subjectivity) emerges from physical complexity is to posit a form of naturalistic magic unless the nature of this emergence, and the causal interaction between consciousness and the brain, can be clearly explained. Why does consciousness emerge? Under what conditions? Does it exert causal influence, and if so, how? If it does not, how can the brain know anything about it?
I call this wider problematic the “Even Harder Problem of Consciousness”: concluding that physicalism is incoherent is not enough, because currently nothing else can command a consensus either. And yet it is not that we are entirely lacking in clues. For example, even though we have no idea what it is or what it does, we are perfectly capable of turning it of. All we need to do is figure out how general anaesthesia actually works, and we'll have our answer...
The Hard Problem of Consciousness is a problem only under materialist or physicalist assumptions. From the perspective of 2PC it is readily resolved: consciousness is not produced by matter per se but arises from the instantiation of a unified self-model that grounds Phase 2 embodiment. The Even Harder Problem, by contrast, concerns the lack of a framework capable of uniting competing metaphysical perspectives. This problem remains open: I cannot claim to have solved it until such time as 2PC has convinced a sufficiently broad community that it provides both a coherent foundation for scientific explanation and a complete, internally consistent model of reality.