thumb|[[David Chalmers on stage for an Alan Turing Year event at De La Salle University, Manila, 27 March 2012]]

In the philosophy of mind, the hard problem of consciousness (or simply the hard problem) is to explain how and why organisms have qualia, phenomenal consciousness, or subjective experience. The following year, the main talking points of Chalmers' talk were published in The Journal of Consciousness Studies. which was later published as a book. In 1996, Chalmers published The Conscious Mind, a book-length treatment of the hard problem, in which he elaborated on his core arguments and responded to counterarguments. His use of the word easy is "tongue-in-cheek". As the cognitive psychologist Steven Pinker puts it, they are about as easy as going to Mars or curing cancer. "That is, scientists more or less know what to look for, and with enough brainpower and funding, they would probably crack it in this century."

The existence of the hard problem is disputed. It has been accepted by some philosophers of mind such as Joseph Levine, Colin McGinn, and Ned Block and cognitive neuroscientists such as Francisco Varela, Giulio Tononi, and Christof Koch. Thomas Metzinger, Patricia Churchland, and Keith Frankish, and by cognitive neuroscientists such as Stanislas Dehaene, Anil Seth, Clinical neurologist and sceptic Steven Novella has dismissed it as "the hard non-problem". According to a 2020 PhilPapers survey, a majority (62.4%) of the philosophers surveyed said they believed that the hard problem is a genuine problem, while 29.7% said that it does not exist.

There are a number of other potential philosophical problems that are related to the Hard Problem. Ned Block believes that there exists a "Harder Problem of Consciousness", due to the possibility of different physical and functional neurological systems potentially having phenomenal overlap. dubbed "The Even Harder Problem of Consciousness", refers to why a given individual has their own particular personal identity, as opposed to existing as someone else. Finally, proposals in the 2020s have been made to reconcile views from neuroscience and the philosophy of mind from a representationalist perspective. This holds in particular for a cognitively inspired form of representationalism, which is presumed to offer a favourable perspective for bridging gaps between different views in cognitive neuroscience and the philosophy of mind, relating to concepts such as intentionality, emergence, consciousness, and qualia.

Overview

Cognitive scientist David Chalmers first formulated the hard problem in his 1995 paper, "Facing up to the problem of consciousness", Daniel Dennett and Patricia Churchland, among others, believe that the hard problem is best seen as a collection of easy problems that will be solved through further analysis of the brain and behaviour. Consciousness is an ambiguous term. It can be used to mean self consciousness, awareness, the state of being awake, and so on. Chalmers uses Thomas Nagel's definition of consciousness as "the feeling of what it is like to be something". In this sense, consciousness is synonymous with experience. For example, why should neural processing in the brain lead to the felt sensations of, say, feelings of hunger? And why should those neural firings lead to feelings of hunger rather than some other feeling (such as, for example, feelings of thirst)? Chalmers argues that it is conceivable that the relevant behaviours associated with hunger, or any other feeling, could occur even in the absence of that feeling. This suggests that experience is irreducible to physical systems such as the brain. This is the topic of the next section.

Chalmers believes that the hard problem is irreducible to the easy problems: solving the easy problems will not lead to a solution to the hard problem. This is because the easy problems pertain to the causal structure of the world while the hard problem pertains to consciousness, and facts about consciousness include facts that go beyond mere causal or structural description.

For example, suppose someone were to stub their foot and yelp. In this scenario, the easy problems are mechanistic explanations that involve the activity of the nervous system and brain and its relation to the environment (such as the propagation of nerve signals from the toe to the brain, the processing of that information and how it leads to yelping, and so on). The hard problem is the question of why these mechanisms are accompanied by the feeling of pain, or why these feelings of pain feel the particular way that they do. Chalmers argues that facts about the neural mechanisms of pain, and pain behaviours, do not lead to facts about conscious experience. Facts about conscious experience are, instead, further facts, not derivable from facts about the brain.

Although Chalmers rejects physicalism, he is still a naturalist. He proposes that consciousness is a fundamental feature of the natural world, not something supernatural, and seeks a nonreductive explanation within a naturalistic framework.

Christian List argues that the existence of first-person perspectives and the inability for physicalism to answer Hellie's vertiginous question is evidence against physicalism, since first-personal facts cannot supervene on physical third-personal facts. List also claims that there exists a "quadrilemma" for metaphysical theories of consciousness, and that for the metaphysical claims of first-person realism, non-solipsism, non-fragmentation, and one-world, at least one of these must be false. List has proposed a model he calls the "many-worlds theory of consciousness" in order to reconcile the subjective nature of consciousness without lapsing into solipsism.

Historical precedents

The hard problem of consciousness has scholarly antecedents considerably earlier than Chalmers. Chalmers himself notes that "a number of thinkers in the recent and distant past" have "recognised the particular difficulties of explaining consciousness." He states that all his original 1996 paper contributed to the discussion was "a catchy name, a minor reformulation of philosophically familiar points". Gottfried Wilhelm Leibniz, and Thomas Henry Huxley. The Tattva Bodha, an eighth-century text attributed to Adi Shankara from the Advaita Vedanta school of Hinduism, describes consciousness being anubhati, or self-revealing, illuminating all objects of knowledge without itself being a material object.

Mind–body problem

The mind–body problem is the problem of how the mind and the body relate. The mind-body problem is more general than the hard problem of consciousness, since it is the problem of discovering how the mind and body relate in general, thereby implicating any theoretical framework that broaches the topic. The hard problem, in contrast, is often construed as a problem uniquely faced by physicalist or materialist theories of mind.

"What Is It Like to Be a Bat?"

The philosopher Thomas Nagel posited in his 1974 paper "What Is It Like to Be a Bat?" that experiences are essentially subjective (accessible only to the individual undergoing them—i.e., felt only by the one feeling them), while physical states are essentially objective (accessible to multiple individuals). So he argued we have no idea what it could mean to claim that an essentially subjective state just is an essentially non-subjective state (i.e., that a felt state is nothing but a functional state). In other words, we have no idea of what reductivism amounts to.

Explanatory gap

In 1983, the philosopher Joseph Levine proposed that there is an explanatory gap between our understanding of the physical world and our understanding of consciousness. Levine disputes that conscious states are reducible to neuronal or brain states. He uses the example of pain (as an example of a conscious state) and its reduction to the firing of c-fibers (a kind of nerve cell). The difficulty is as follows: even if consciousness is physical, it is not clear which physical states correspond to which conscious states. The bridges between the two levels of description will be contingent, rather than necessary. This is significant because in most contexts, relating two scientific levels of descriptions (such as physics and chemistry) is done with the assurance of necessary connections between the two theories (for example, chemistry follows with necessity from physics).

Levine illustrates this with a thought experiment: Suppose that humanity were to encounter an alien species, and suppose it is known that the aliens do not have any c-fiber. Even if one knows this, it is not obvious that the aliens do not feel pain: that would remain an open question. This is because the fact that aliens do not have c-fibers does not entail that they do not feel pain (in other words, feelings of pain do not follow with logical necessity from the firing of c-fibers). Levine thinks such thought experiments demonstrate an explanatory gap between consciousness and the physical world: even if consciousness is reducible to physical things, consciousness cannot be explained in terms of physical things, because the link between physical things and consciousness is a contingent link. They are hypothetical beings physically identical to humans but that lack conscious experience. Philosophers such as Chalmers, Joseph Levine, and Saul Kripke take zombies as impossible within the bounds of nature but possible within the bounds of logic. This would imply that facts about experience are not logically entailed by the "physical" facts. Therefore, consciousness is irreducible. In Chalmers' words, "after God (hypothetically) created the world, he had more work to do." Daniel Dennett, a philosopher of mind, criticised the field's use of "the zombie hunch" which he deems an "embarrassment" that ought to "be dropped like a hot potato".

Knowledge argument

The knowledge argument, also known as Mary's Room, is another common thought experiment: A hypothetical neuroscientist named Mary has lived her whole life in a black-and-white room and has never seen colour before. She also happens to know everything there is to know about the brain and colour perception. Chalmers believes PhilPapers is an organisation that archives academic philosophy papers and periodically surveys professional philosophers about their views. It can be used to gauge professional attitudes towards the hard problem. As of the 2020 survey results, it seems that the majority of philosophers (62.42%) agree that the hard problem is real, with a substantial minority that disagrees (29.76%).

Attitudes towards physicalism also differ among professionals. In the 2009 PhilPapers survey, 56.5% of philosophers surveyed subscribed to physicalism and 27.1% of philosophers surveyed rejected physicalism. 16.4% fell into the "other" category. In the 2020 PhilPapers survey, 51.93% of philosophers surveyed indicated that they "accept or lean towards" physicalism and 32.08% indicated that they reject physicalism. 6.23% were "agnostic" or "undecided". The labelling convention of this taxonomy has been incorporated into the technical vocabulary of analytic philosophy, being used by philosophers such as Adrian Boutel, Raamy Majeed, Pete Mandik & Josh Weisberg, Roberto Pereira, and Helen Yetter-Chappell.

Type-A materialism

Type-A materialism, also known as reductive materialism or a priori physicalism, is a view characterised by a commitment to physicalism and a full rejection of the hard problem. By this view, the hard problem either does not exist or is just another easy problem, because every fact about the mind is a fact about the performance of various functions or behaviours. As a result, once all the relevant functions and behaviours have been accounted for, there will not be any facts left over in need of explanation.

Strong reductionism

Many philosophers have disputed that there is a hard problem of consciousness distinct from what Chalmers calls the easy problems of consciousness. Some among them, who are sometimes termed strong reductionists, hold that phenomenal consciousness (i.e., conscious experience) does exist but that it can be fully understood as reducible to the brain. On the higher-order view, since consciousness is a representation, and representation is fully functionally analysable, there is no hard problem of consciousness. The philosopher Massimo Pigliucci argued in 2013 that the hard problem is misguided, resulting from a "category mistake". The philosopher Thomas Metzinger likens the hard problem of consciousness to vitalism, a formerly widespread view in biology which was not so much solved as abandoned. Brian Jonathan Garrett has also argued that the hard problem suffers from flaws analogous to those of vitalism.

The philosopher Peter Hacker argues that the hard problem is misguided in that it asks how consciousness can emerge from matter, whereas in fact sentience emerges from the evolution of living organisms. He states: "The hard problem isn't a hard problem at all. The really hard problems are the problems the scientists are dealing with. ... The philosophical problem, like all philosophical problems, is a confusion in the conceptual scheme." Hacker further states that "consciousness studies", as it exists today, is "literally a total waste of time" and that "the conception of consciousness which they have is incoherent". According the 2020 PhilPapers survey, 4.51% of philosophers surveyed subscribe to eliminativism. Similar ideas have been explicated in his 1991 book Consciousness Explained. Dennett argues that the so-called "hard problem" will be solved in the process of solving what Chalmers terms the "easy problems". But when the issue is tackled with "formal argumentation" and "precise semantics" then the hard problem will dissolve.

A complete illusionist theory of consciousness must include the description of a mechanism by which the illusion of subjective experience is had and reported by people. Various philosophers and scientists have proposed possible theories. For example, in his book Consciousness and the Social Brain neuroscientist Michael Graziano advocates what he calls attention schema theory, in which our perception of being conscious is merely an error in perception, held by brains which evolved to hold erroneous and incomplete models of their own internal workings, just as they hold erroneous and incomplete models of their own bodies and of the external world. The roots of the Moorean Argument against illusionism extend back to Augustine of Hippo who stated that he could not be deceived regarding his own existence, since the very act of being deceived secures the existence of a being there to be the recipient of that deception. In the Early-Modern era, these arguments were repopularized by René Descartes, who coined the now famous phrase "Je pense, donc je suis" ("I think, therefore I am"). Descartes argued that even if he was maximally deceived (because, for example, an evil demon was manipulating all his senses) he would still know with certainty that his mind exists, because the state of being deceived requires a mind as a prerequisite.

This same general argumentative structure is still in use today. In 2002, David Chalmers published an explicitly Moorean argument against illusionism. The argument goes like this: The reality of consciousness is more certain than any theoretical commitments (to, for example, physicalism) that may be motivating the illusionist to deny the existence of consciousness. The reason for this is because we have direct "acquaintance" with consciousness, but we do not have direct acquaintance with anything else (including anything that could inform our beliefs in consciousness being an illusion). In other words: consciousness can be known directly, so the reality of consciousness is more certain than any philosophical or scientific theory that says otherwise. Chalmers concludes that "there is little doubt that something like the Moorean argument is the reason that most people reject illusionism and many find it crazy."

Eliminative materialism and illusionism have been the subject of criticism within the popular press. One highly cited example comes from the philosopher Galen Strawson who wrote an article in the New York Review of Books titled "The Consciousness Deniers". In it, Strawson describes illusionism as the "silliest claim ever made", next to which "every known religious belief is only a little less sensible than the belief that the grass is green." Another notable example comes from Christof Koch (a neuroscientist and one of the leading proponents of Integrated Information Theory) in his popular science book The Feeling of Life Itself. In the early pages of the book, Koch describes eliminativism as the "metaphysical counterpart to Cotard's syndrome, a psychiatric condition in which patients deny being alive." Koch takes the prevalence of eliminativism as evidence that "much of twentieth-century analytic philosophy has gone to the dogs".

Frankish has responded to such criticisms by asserting that "qualia realists" have to conceive of qualia as being either observational or theoretical in nature. If conceived of as observational, then realists cannot claim that illusionists are leaving anything out of their theories of consciousness, as such a claim would presuppose qualia as having certain theoretical components. If conceived of as theoretical, then illusionists are simply denying the theoretical components of qualia but not the mere fact that they exist, which is what they're attempting to explain in the first place.

Type-B materialism

Type-B materialism, also known as weak reductionism or a posteriori physicalism, is the view that the hard problem stems from human psychology, and is therefore not indicative of a genuine ontological gap between consciousness and the physical world. In relation to Type-B Materialism, those who believe that our intuitions about the hard problem are innate (and therefore common to all humans) subscribe to the "hard-wired view". Joseph Levine, and Janet Levine. The philosophers Ned Block and Robert Stalnaker agree that facts about what a conscious experience is like to the one experiencing it cannot be deduced from knowing all the facts about the underlying physiology, but by contrast argue that such gaps of knowledge are also present in many other cases in nature, such as the distinction between water and H<sub>2</sub>O. By this view, the hard problem of consciousness stems from a dualism of concepts, not from a dualism of properties or substances. Hakwan Lau and Matthias Michel. Wierzbicka (who is a linguist) argues that the vocabulary used by consciousness researchers (including words like experience and consciousness) are not universally translatable, and are "parochially English." or a suspected future theory of everything combining relativity and quantum mechanics. Similarly, type-C materialism posits that the problem of consciousness is a consequence of our ignorance, but just as resolvable as any other question in neuroscience.

Because the explanatory question of consciousness is evaded, type-C materialism does not presuppose the descriptive question, for instance that there is any self-consciousness, wakefulness, or even sentience in a rock. Principally, the basis for the argument arises from the apparently high correlation of consciousness with living brain tissue, thereby rejecting panpsychism Whether via the inconceivability or actual nonexistence of zombies, a contradiction is exposed nullifying the premise of the consciousness problem's "hardness".

Type-C materialism is compatible with several cases and could collapse into one of these other metaphysical views With characterisation of intrinsic properties in physics extending beyond structure and dynamics, it could resolve to type-F monism.

Type-D and Type-E dualism

Dualism views consciousness as either a non-physical substance separate from the brain or a non-physical property of the physical brain. Dualism is the view that the mind is irreducible to the physical body. while epiphenomenalism has been defended by philosophers including Frank Jackson, although Jackson later changed his stance to physicalism. Chalmers has also defended versions of both positions as plausible. while neutral monism, in at least some variations, holds that entities are composed of a substance with mental and physical aspects—and is thus sometimes described as a type of panpsychism.

Forms of panpsychism and neutral monism were defended in the early twentieth century by the psychologist William James, the philosopher Alfred North Whitehead, and the philosopher Bertrand Russell, Philip Goff,

Idealism and cosmopsychism

A traditional solution to the hard problem is idealism, according to which consciousness is fundamental and not simply an emergent property of matter. It is claimed that this avoids the hard problem entirely. Objective idealism and cosmopsychism consider mind or consciousness to be the fundamental substance of the universe. Proponents claim that this approach is immune to both the hard problem of consciousness and the combination problem that affects panpsychism.

From an idealist perspective, matter is a representation or image of mental processes. Supporters suggest that this avoids the problems associated with the materialist view of mind as an emergent property of a physical brain. Critics argue that this then leads to a decombination problem: how is it possible to split a single, universal conscious experience into multiple, distinct conscious experiences? In response, Bernardo Kastrup claims that nature hints at a mechanism for this in the condition dissociative identity disorder (previously known as Multiple Personality Disorder). Kastrup proposes dissociation as an example from nature showing that multiple minds with their own individual subjective experience could develop within a single universal mind.

Cognitive psychologist Donald D. Hoffman uses a mathematical model based around conscious agents, within a fundamentally conscious universe, to support conscious realism as a description of nature—one that falls within the objective idealism approaches to the hard problem: "The objective world, i.e., the world whose existence does not depend on the perceptions of a particular conscious agent, consists entirely of conscious agents." David Chalmers calls this form of idealism one of "the handful of promising approaches to the mind–body problem."

New mysterianism

New mysterianism, most significantly associated with the philosopher Colin McGinn, proposes that the human mind, in its current form, will not be able to explain consciousness.

  1. [PQ] Physical processing gives rise to experiences with a phenomenal character.
  2. [Q] Our phenomenal qualities are thus-and-so.

The first fact concerns the relationship between the physical and the phenomenal (i.e., how and why are some physical states felt states), whereas the second concerns the very nature of the phenomenal itself (i.e., what does the felt state feel like?). Wolfgang Fasching argues that the hard problem is not about qualia, but about the what-it-is-like-ness of experience in Nagel's sense—about the givenness of phenomenal contents:

<blockquote>Today there is a strong tendency to simply equate consciousness with the qualia. Yet there is clearly something not quite right about this. The "itchiness of itches" and the "hurtfulness of pain" are qualities we are conscious of. So philosophy of mind tends to treat consciousness as if it consisted simply of the contents of consciousness (the phenomenal qualities), while it really is precisely consciousness of contents, the very givenness of whatever is subjectively given. And therefore the problem of consciousness does not pertain so much to some alleged "mysterious, nonpublic objects", i.e. objects that seem to be only "visible" to the respective subject, but rather to the nature of "seeing" itself (and in today's philosophy of mind astonishingly little is said about the latter).</blockquote>

Relationship to scientific frameworks

Most neuroscientists and cognitive scientists believe that Chalmers' alleged "hard problem" will be solved, or be shown to not be a real problem, in the course of the solution of the so-called "easy problems", although a significant minority disagrees.

Neural correlates of consciousness

Since 1990, researchers including the molecular biologist Francis Crick and the neuroscientist Christof Koch have made significant progress toward identifying which neurobiological events occur concurrently to the experience of subjective consciousness. These postulated events are referred to as neural correlates of consciousness or NCCs. However, this research arguably addresses the question of which neurobiological mechanisms are linked to consciousness but not the question of why they should give rise to consciousness at all, the latter being the hard problem of consciousness as Chalmers formulated it. In "On the Search for the Neural Correlate of Consciousness", Chalmers said he is confident that, granting the principle that something such as what he terms "global availability" can be used as an indicator of consciousness, the neural correlates will be discovered "in a century or two". Nevertheless, he stated regarding their relationship to the hard problem of consciousness:

<blockquote>One can always ask why these processes of availability should give rise to consciousness in the first place. As yet we cannot explain why they do so, and it may well be that full details about the processes of availability will still fail to answer this question. Certainly, nothing in the standard methodology I have outlined answers the question; that methodology assumes a relation between availability and consciousness, and therefore does nothing to explain it. ... So the hard problem remains. But who knows: Somewhere along the line we may be led to the relevant insights that show why the link is there, and the hard problem may then be solved. Kandel went on to note Crick and Koch's suggestion that once the binding problem—understanding what accounts for the unity of experience—is solved, it will be possible to solve the hard problem empirically. This more modest goal is the focus of most scientists working on consciousness.

Computational cognition

A functionalist view in cognitive science holds that the mind is an information processing system, and that cognition and consciousness together are a form of computation. Cognition, distinct from consciousness, is explained by neural computation in the computational theory of cognition. The computational theory of mind asserts that not only cognition, but also phenomenal consciousness or qualia, are computational. While the computation system is realised by neurons rather than electronics, in theory it would be possible for artificial intelligence to be conscious.

Integrated information theory

Integrated information theory (IIT), developed by the neuroscientist and psychiatrist Giulio Tononi in 2004 and more recently also advocated by Koch, is one of the most discussed models of consciousness in neuroscience and elsewhere. The theory proposes an identity between consciousness and integrated information, with the latter item (denoted as Φ) defined mathematically and thus in principle measurable. The hard problem of consciousness, write Tononi and Koch, may indeed be intractable when working from matter to consciousness.</blockquote>

As part of a broader critique of IIT, Michael Cerullo suggested that the theory's proposed explanation is in fact for what he dubs (following Scott Aaronson) the "Pretty Hard Problem" of methodically inferring which physical systems are conscious—but would not solve Chalmers' hard problem.

Global workspace theory

Global workspace theory (GWT) is a cognitive architecture and theory of consciousness proposed by the cognitive psychologist Bernard Baars in 1988. Baars explains the theory with the metaphor of a theatre, with conscious processes represented by an illuminated stage.

In his original paper outlining the hard problem of consciousness, Chalmers discussed GWT as a theory that only targets one of the "easy problems" of consciousness. By contrast, A. C. Elitzur argued: "While [GWT] does not address the 'hard problem', namely, the very nature of consciousness, it constrains any theory that attempts to do so and provides important insights into the relation between consciousness and cognition."

For his part, Baars writes (along with two colleagues) that there is no hard problem of explaining qualia over and above the problem of explaining causal functions, because qualia are entailed by neural activity and themselves causal.

Meta-problem

In 2018, Chalmers highlighted what he calls the "meta-problem of consciousness", another problem related to the hard problem of consciousness:

Tom Stoppard's play The Hard Problem, first produced in 2015, is named after the hard problem of consciousness, which Stoppard defines as having "subjective First Person experiences".

See also

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  • Animal consciousness
  • Artificial consciousness
  • Binding problem
  • Blindsight
  • Chinese room
  • Cogito, ergo sum
  • Cryonics
  • Free will
  • Ideasthesia
  • Introspection
  • Knowledge by acquaintance
  • List of unsolved problems in biology
  • Mind–body problem
  • Phenomenalism
  • Philosophy of self
  • Primary–secondary quality distinction
  • Problem of mental causation
  • Problem of other minds
  • Vertiginous question
  • Consciousness causes collapse

<!-- please keep entries in alphabetical order -->

Notes

References