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{{Short description|Philosophical concept}}

In the [[philosophy of mind]], the '''hard problem of consciousness''' is to explain why and how humans and other organisms have [[qualia]], [[Consciousness#Types of consciousness|phenomenal consciousness]], or [[subjective character of experience|subjective experience]].<ref name="Chalmers" /><ref name="Harnad"/> It is contrasted with the "easy problems" of explaining why and how physical systems give a human being the ability to discriminate, to integrate information, and to perform behavioural functions such as watching, listening, speaking (including generating an utterance that appears to refer to personal behaviour or belief), and so forth.<ref name="Chalmers" /> The easy problems are amenable to functional explanation—that is, explanations that are mechanistic or behavioural—since each physical system can be explained purely by reference to the "structure and dynamics" that underpin the phenomenon.<ref name="Chalmers" /><ref name="Cooney" />

Proponents of the hard problem propose that it is categorically different from the easy problems since no mechanistic or behavioural explanation could explain the character of an experience, not even in principle. Even after all the relevant functional facts are explicated, they argue, there will still remain a further question: "why is the performance of these functions accompanied by experience?"<ref name="Chalmers" /> To bolster their case, proponents of the hard problem frequently turn to various philosophical thought experiments, involving [[philosophical zombie]]s, or [[inverted spectrum|inverted qualia]], or the [[Knowledge Argument|ineffability of colour experiences]], or the unknowability of foreign states of consciousness, such as the experience of [[what is it like to be a bat?|being a bat]].

[[File:David Chalmers, delivering a talk at De La Salle University-Manila, March 27, 2012.jpg|thumb|right|265px|Chalmers on stage for an [[Alan Turing Year]] event at [[De La Salle University]], Manila, 27 March 2012]]

The terms "hard problem" and "easy problems" were coined by the [[philosopher]] [[David Chalmers]] in a 1994 talk given at [[The Science of Consciousness]] conference held in Tucson, Arizona.<ref>[https://www.youtube.com/watch?v=_lWp-6hH_6g|Hard Problem of Consciousness (Tuscan 1994)]</ref> The following year, the main talking points of Chalmers' talk were published in ''[[The Journal of Consciousness Studies]]''.<ref name="Chalmers" /> The publication gained significant attention from consciousness researchers and became the subject of a special volume of the journal,<ref>JCS vol. 4, pp. 3-46, 1997</ref><ref>{{
cite journal
| last=Chalmers
| first=David
| title=Moving forward on the problem of consciousness
| journal=Journal of Consciousness Studies
| volume=4
| issue=1
| pages=3–46}}</ref> which was later published into a book.<ref>{{
cite book
| last=Shear
| first=Jonathan
| year=1997
| title=Explaining Consciousness: The Hard Problem
| publisher=MIT Press|isbn=978-0262692212}}</ref> 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".<ref>{{Cite web|title=Episode 83, The David Chalmers Interview (Part I - Consciousness)|url=https://thepanpsycast.com/panpsycast2/episode83-1|access-date=2020-09-05|website=The Panpsycast Philosophy Podcast|date=19 July 2020|language=en-GB}}</ref> 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."<ref name="pinker-time">{{cite magazine|last1=Pinker|first1=Steven|author-link1=Steven Pinker|date=29 January 2007|title=The Brain: The Mystery of Consciousness|url=http://content.time.com/time/magazine/article/0,9171,1580394-1,00.html|archive-url=https://web.archive.org/web/20130917143400/http://content.time.com/time/magazine/article/0,9171,1580394-1,00.html|url-status=dead|archive-date=September 17, 2013|magazine=Time|access-date=19 December 2018}}</ref>

The existence of the hard problem is disputed. It has been accepted by some [[Philosophy of mind|philosophers of mind]] such as [[Joseph Levine (philosopher)|Joseph Levine]],<ref>
{{Cite journal|last=Levine|first=Joseph|date=2009-01-15|title=The Explanatory Gap|url=https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199262618.001.0001/oxfordhb-9780199262618-e-17|journal=The Oxford Handbook of Philosophy of Mind|pages=281–291|doi=10.1093/oxfordhb/9780199262618.003.0017|isbn=978-0199262618|url-access=subscription}}</ref> [[Colin McGinn]],<ref name="mcginn-2012">{{cite web|url=http://www.newstatesman.com/ideas/2012/02/consciousness-mind-brain|title=All machine and no ghost?|last=McGinn|first=Colin|author-link=Colin McGinn|date=20 February 2012|work=[[New Statesman]]|access-date=27 March 2012}}</ref> and [[Ned Block]]<ref name="harder-problem">{{cite journal|last1=Block|first1=Ned|title=The Harder Problem of Consciousness|journal=The Journal of Philosophy|date=2002|volume=99|issue=8|pages=391–425|jstor=3655621|doi=10.2307/3655621|s2cid=111383062|url=https://philpapers.org/rec/BLOTHP}}
</ref> and [[Cognitive neuroscience|cognitive neuroscientists]] such as [[Francisco Varela]],<ref>{{cite journal|last1=Varela|first1=F.J.|title=Neurophenomenology: a methodological remedy for the hard problem|journal=Journal of Consciousness Studies|date=1 April 1996|volume=3|issue=4|pages=330–349|url=https://www.ingentaconnect.com/content/imp/jcs/1996/00000003/00000004/718}}</ref> [[Giulio Tononi]],<ref name="iit-koch-et-al">{{cite journal|last1=Tononi|first1=Giulio|last2=Boly|first2=Melanie|last3=Massimini|first3=Marcello|last4=Koch|first4=Christof|title=Integrated information theory: from consciousness to its physical substrate|journal=Nature Reviews Neuroscience|date=July 2016|volume=17|issue=7|pages=450–461|doi=10.1038/nrn.2016.44|pmid=27225071|s2cid=21347087}}</ref><ref name="tononi+koch">{{cite journal|last1=Tononi|first1=Giulio|last2=Koch|first2=Christof|title=Consciousness: here, there and everywhere?|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|date=March 2015|volume=370|issue=1668|pages=20140167|doi=10.1098/rstb.2014.0167|pmid=25823865|pmc=4387509}}</ref> and [[Christof Koch]].<ref name="iit-koch-et-al"/><ref name="tononi+koch"/> On the other hand, its existence is denied by other philosophers of mind, such as [[Daniel Dennett]],<ref name=Dennett/> [[Massimo Pigliucci]],<ref name=Pigliucci2013>
{{cite journal|author1=Massimo Pigliucci|author-link=Massimo Pigliucci|title=What hard problem?|journal=Philosophy Now|date=2013|issue=99|url=http://philpapers.org/archive/PIGWHP.pdf}}
</ref> [[Thomas Metzinger]], [[Patricia Churchland]],<ref name="pat-churchland-1996">{{cite journal|last1=Churchland|first1=Patricia|title=The Hornswoggle Problem|journal=Journal of Consciousness Studies|date=1996|volume=3|issue=5–6|pages=402–408|url=http://joelvelasco.net/teaching/2300/hornswoggleprob.pdf|access-date=10 January 2021}}</ref> and [[Keith Frankish]],<ref name="frankish">
{{cite journal|last1=Frankish|first1=Keith| author-link=Keith Frankish| title=Illusionism as a Theory of Consciousness|journal=Journal of Consciousness Studies|date=2016|volume=23|issue=11–12|pages=11–39|url=https://nbviewer.jupyter.org/github/k0711/kf_articles/blob/master/Frankish_Illusionism%20as%20a%20theory%20of%20consciousness_eprint.pdf|access-date=20 December 2018}}</ref> and by cognitive neuroscientists such as [[Stanislas Dehaene]],<ref name="Dehaene" /> [[Bernard Baars]],<ref name="dc-gw">{{cite journal|last1=Edelman|first1=Gerald|last2=Gally|first2=Joseph|last3=Baars|first3=Bernard|title=Biology of Consciousness|journal=Frontiers in Psychology|date=2011|volume=2|issue=4|pages=4|doi=10.3389/fpsyg.2011.00004|pmid=21713129|pmc=3111444 
|doi-access=free}}</ref> [[Anil Seth]],<ref name="seth-aeon"/> and [[Antonio Damasio]].<ref>{{cite podcast| url=https://www.preposterousuniverse.com/podcast/2019/04/29/episode-44-antonio-damasio-on-feelings-thoughts-and-the-evolution-of-humanity/| title=Sean Carroll's Mindscape| website=Preposterousuniverse.com| publisher=Sean Carroll| host=Sean Carroll| date=29 April 2019| time=1:04.46| quote= I’m just saying that the idea of a hard problem that you cannot transpose, I think is wrong.}}</ref> Clinical neurologist and sceptic [[Steven Novella]] has dismissed it as "the hard non-problem".<ref>{{cite web|title=Psychological Scales. The Hard Problem of Consciousness.|url=https://scales.arabpsychology.com/2022/11/19/hard-problem-of-consciousness-2/|website=arabpsychology.com|access-date=2023-10-29}}</ref> According to a 2020 [[PhilPapers]] survey, a majority (62.42%) of the philosophers surveyed said they believed that the hard problem is a genuine problem, while 29.72% said that it does not exist.{{r|philpapers2020}}

There are a number of other potential [[List of philosophical problems|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.<ref name="harder-problem"/> Another potential philosophical problem which is closely related to Benj Hellie's [[vertiginous question]]<ref>{{cite journal |last1=Hellie |first1=Benj |last2= |first2= |date=2013 |title=Against Egalitarianism |url=https://philpapers.org/rec/HELCFC |journal=Analysis |volume=73 |issue= |publisher= |pages=304–320 |doi=10.1093/analys/ans101 |access-date=}}</ref>, 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.<ref>{{cite journal|last=Roberts|first=Tim S.|title=''The Even Harder Problem of Consciousness'' by Roberts. Tim S.|journal=NeuroQuantology|date=September 2007|volume=5|issue=2|pages=214–221|doi=10.14704/nq.2007.5.2.129 |url=https://www.researchgate.net/publication/228618472}}</ref>

==Overview==
Cognitive scientist [[David Chalmers]] first formulated the hard problem in his paper "Facing up to the problem of consciousness" (1995)<ref name="Chalmers" /> and expanded upon it in ''[[The Conscious Mind]]'' (1996). His works provoked comment. Some, such as philosopher [[David Lewis (philosopher)|David Lewis]] and Steven Pinker, have praised Chalmers for his argumentative rigour and "impeccable clarity".<ref name=":0" /> Pinker later said, in 2018, "In the end I still think that the hard problem is a meaningful conceptual problem, but agree with Dennett that it is not a meaningful scientific problem. No one will ever get a grant to study whether you are a zombie or whether the same Captain Kirk walks on the deck of the Enterprise and the surface of Zakdorn. And I agree with several other philosophers that it may be futile to hope for a solution at all, precisely because it is a conceptual problem, or, more accurately, a problem with our concepts."<ref>{{cite book|first1=Steven|last1=Pinker|date=2018|title=Enlightenment Now|page=481|isbn=9780525427575|publisher=Viking}}</ref> [[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.<ref name=":1" /><ref>{{cite book|doi=10.1016/S0079-6123(05)49020-2|chapter=A neurophilosophical slant on consciousness research|title=Cortical Function: A View from the Thalamus|series=Progress in Brain Research|year=2005|last1=Churchland|first1=Patricia Smith|volume=149|pages=285–293|pmid=16226591|isbn=9780444516794}}</ref>

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: "''the feeling of what it is like to be something."'' Consciousness, in this sense, is synonymous with ''experience.''<ref name="Bat" /><ref name=":0" />

=== Chalmers' formulation ===
{{Quote|text=. . .even when we have explained the performance of all the cognitive and behavioral functions in the vicinity of experience—perceptual discrimination, categorization, internal access, verbal report—there may still remain a further unanswered question: ''Why is the performance of these functions accompanied by experience?''|author=David Chalmers|title=Facing up to the problem of consciousness|source=}}The problems of consciousness, Chalmers argues, are of two kinds: the ''easy problems'' and the ''hard problem''.

==== Easy problems ====
The easy problems are amenable to reductive enquiry. They are a [[logical consequence]] of lower-level facts about the world, similar to how a clock's ability to tell time is a logical consequence of its clockwork and structure, or a hurricane being a logical consequence of the structures and functions of certain weather patterns. A clock, a hurricane, and the easy problems, are all the sum of their parts (as are most things).<ref name=":0" />

The easy problems relevant to consciousness concern mechanistic analysis of the neural processes that accompany behaviour. Examples of these include how sensory systems work, how sensory data is processed in the brain, how that data influences behaviour or verbal reports, the neural basis of thought and emotion, and so on. They are problems that can be analysed through "structures and functions".<ref name=":0" />

==== Hard problem ====
The hard problem, in contrast, is the problem of ''why'' and ''how'' those processes are accompanied by experience.<ref name="Chalmers" /> It may further include the question of why these processes are accompanied by this or that particular experience, rather than some other kind of experience. In other words, the hard problem is the problem of explaining why certain mechanisms are accompanied by conscious experience.<ref name=":0">{{Cite book|last=Chalmers|first=David|title=The Conscious Mind|publisher=Oxford University Press|year=1996|location=New York|pages=xii–xiii, 95–106, backcover}}</ref> 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 [[Irreducibility|irreducible]] to physical systems such as the brain. This is the topic of the next section.

==== How the easy and hard problems are related ====
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 problems. 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.<ref name=":2">{{Cite web |title=Hard Problem of Consciousness |url=https://iep.utm.edu/hard-problem-of-conciousness/ |access-date=2024-10-09 |website=Internet Encyclopedia of Philosophy |language=en-US}}</ref>

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.<ref name=":0" /><ref name=":2" />[[File:Inverted_qualia_of_colour_strawberry.jpg|thumb|The hard problem is often illustrated by appealing to the logical possibility of inverted visible spectra. If there is no logical contradiction in supposing that one's colour vision could be inverted, it follows that mechanistic explanations of visual processing do not determine facts about what it is like to see colours.|280x280px]] An explanation for all of the relevant physical facts about neural processing would leave unexplained facts about what it is like to feel pain. This is in part because functions and physical structures of any sort could conceivably exist in the absence of experience. Alternatively, they could exist alongside a different set of experiences. For example, it is [[Logical possibility|logically possible]] for a perfect replica of Chalmers to have no experience at all, or for it to have a different set of experiences (such as an inverted visible spectrum, so that the blue-yellow red-green axes of its visual field are flipped).<ref name=":2" />

The same cannot be said about clocks, hurricanes, or other physical things. In those cases, a structural or functional description is a complete description. A perfect replica of a clock is a clock, a perfect replica of a hurricane is a hurricane, and so on. The difference is that physical things are nothing more than their physical constituents. For example, water is nothing more than H<sub>2</sub>O molecules, and understanding everything about H<sub>2</sub>O molecules is to understand everything there is to know about water. But consciousness is not like this. Knowing everything there is to know about the brain, or any physical system, is not to know everything there is to know about consciousness. Consciousness, then, must not be purely physical.<ref name=":0" />

==== Implications for physicalism ====
{{See also|Physicalism}}
[[File:Sturnus vulgaris -Rotterdam, South Holland, Netherlands -flock-8.ogv|thumb|right|A swarm of birds showing high order structure emerging from simpler physical constituents]]

Chalmers's idea contradicts [[physicalism]], sometimes labelled [[materialism]]. This is the view that everything that exists is a physical or material thing, so everything can be reduced to microphysical things. For example, the rings of Saturn are a physical thing because they are nothing more than a complex arrangement of a large number of subatomic particles interacting in a certain way. According to physicalism, everything, including consciousness, can be explained by appeal to its microphysical constituents. Chalmers's ''hard problem'' presents a [[counterexample]] to this view and to other phenomena like swarms of birds, since it suggests that consciousness, and analogously swarms of birds, cannot be reductively explained by appealing to their physical constituents. Thus, if the hard problem is a real problem then physicalism must be false, and if physicalism is true then the hard problem must not be a real problem.{{cn|date=September 2022}}

Though Chalmers rejects physicalism, he is still a [[Naturalism (philosophy)|naturalist]].<ref name=":0" />{{importance inline|date=April 2023}}

[[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.<ref>{{cite web |url=https://philpapers.org/rec/LISTFA |title=The first-personal argument against physicalism |last=List |first=Christian |date=2023 |website= |publisher= |access-date=4 March 2025 |quote=}}</ref> 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.<ref>{{cite web |url=https://philarchive.org/rec/LISAQF |title=A quadrilemma for theories of consciousness |last=List |first=Christian |date=2023 |website= |publisher=The Philosophical Quarterly |access-date=4 March 2025 |quote=}}</ref> 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.<ref>{{cite web |url=https://philarchive.org/rec/LISTMT-2 |title=The many-worlds theory of consciousness |last=List |first=Christian |date=2023 |website= |publisher=The Philosophical Quarterly |access-date=4 March 2025 |quote=}}</ref>

=== Historical precedents ===
{{Wikiquote}}
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."<ref name="Moving forward">{{cite journal
| last=Chalmers
| first=David
| author-link=David Chalmers
| date=January 1997
| title=Moving forward on the problem of consciousness| journal=[[Journal of Consciousness Studies]]
| volume=4
| issue=1
| pages=3–46 
| url=https://philpapers.org/rec/CHAMFO}}</ref> He states that all his original 1996 paper contributed to the discussion was "a catchy name, a minor reformulation of philosophically familiar points".<ref name="Moving forward" />

Among others, thinkers who have made arguments similar to Chalmers' formulation of the hard problem include [[Isaac Newton]],<ref name="chalmers-2020">{{cite journal|last1=Chalmers|first1=David|title=Is the hard problem of consciousness universal?|journal=Journal of Consciousness Studies|date=2020|volume=27|issue=5–6|pages=227–257|url=http://consc.net/papers/universal.pdf|access-date=22 February 2022}}</ref> [[John Locke]],<ref>{{cite book|last=Locke|first=John|author-link=John Locke|date=1722|title=The works of John Locke: in three volumes|location=London|publisher=Printed for A. Churchill, and A. Manship, and sold by W. Taylor in Pater-noster-Row|volume=1|page=[https://books.google.com/books?id=0BfmAAAAMAAJ&pg=PA293 293]}}</ref> [[Gottfried Wilhelm Leibniz]],<ref name="Aranyosi" /><ref name="chalmers-2020"/> [[John Stuart Mill]],<ref>Mill, John Stuart. ''A System of Logic'' (1843), Book V, Chapter V, section 3</ref> and [[Thomas Henry Huxley]].<ref>{{cite book|last1=Huxley|first1=Thomas Henry|author-link1=Thomas Henry Huxley|last2=Youmans|first2=William Jay|author-link2=William Jay Youmans|date=1868|title=The elements of physiology and hygiene: a text-book for educational institutions|location=New York|publisher=D. Appleton and company|page=[https://books.google.com/books?id=aVUAAAAAYAAJ&pg=PA178 178]}}</ref><ref name="chalmers-2020"/> Likewise, Asian philosophers like [[Dharmakirti]] and [[Guifeng Zongmi]] discussed the problem of how consciousness arises from unconscious matter.<ref name="chalmers-2020"/><ref name="arnold-2021">{{cite book|last1=Arnold|first1=Dan|editor1-last=Emmanuel|editor1-first=Steven M.|title=Philosophy's Big Questions: Comparing Buddhist and Western Approaches|date=2021|publisher=Columbia University Press|location=New York|isbn=978-0231174879|pages=97–128|chapter=Philosophy of Mind’s “Hard Problem” in Light of Buddhist Idealism}}</ref><ref>Bryan Van Norden, {{Citation|title=Buddhism Comes to China| date=17 March 2021 |url=https://www.youtube.com/watch?v=Q1xv3HmUddY|language=en|access-date=2021-12-29}}</ref><ref>Tiwald, Justin; Van Norden, Bryan W. eds. (2005), ''Readings in Later Chinese Philosophy,'' p. 101. Hackett Publishing.</ref> 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.<ref>{{Cite book |last=Shankara |first=Adi |title=Tattva Bodha |last2=Chaturvedi |first2=Shraddhesh |publisher=Vedic Scriptures Publishing |year=2019 |isbn=9781701001374 |location=Amroha, Uttar Pradesh, India |trans-title=Understanding Reality}}</ref><ref>{{Cite web |last=Vas |first=Andre |date=29 October 2023 |title=23 – Tattva Bodha: Existence-Consciousness Alone Is (Satchit Meaning) |url=https://www.yesvedanta.com/tattva-bodha-discourses/discourse-23/ |url-status=live |access-date=19 January 2025 |website=Yes Vedanta |archive-url=https://web.archive.org/web/20250122101033/https://www.yesvedanta.com/tattva-bodha-discourses/discourse-23/ |archive-date=Jan 22, 2025 }}</ref>

=== Related concepts ===

==== The mind–body problem ====
{{Main|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?" ====
{{Main|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.<ref name="Bat"/> He believes "every subjective phenomenon is essentially connected with a single point of view, and it seems inevitable that an objective, physical theory will abandon that point of view."<ref name="Bat">{{cite journal|last=Nagel|first=Thomas|author-link=Thomas Nagel|date=October 1974|title=What is it like to be a bat?|journal=[[The Philosophical Review]]|volume=83|issue=4|pages=435–450|doi=10.2307/2183914|jstor=2183914|s2cid=49125889}}</ref>

==== Explanatory gap ====
{{Main|Explanatory gap}}
{{see also|Reductionism}}
In 1983, the philosopher [[Joseph Levine (philosopher)|Joseph Levine]] proposed that there is an ''explanatory gap'' between our understanding of the physical world and our understanding of consciousness.<ref name=Levine1983>Levine, J. 1983. “Materialism and qualia: the explanatory gap”. ''Pacific Philosophical Quarterly'', 64: 354–361.</ref>

Levine's 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 [[Group C nerve fiber|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 [[Contingency (philosophy)|contingent]], rather than [[Necessity and sufficiency|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).<ref name="jw-iep">{{cite web|last1=Weisberg|first1=Josh|title=The Hard Problem of Consciousness|url=https://www.iep.utm.edu/hard-con/|website=Internet Encyclopedia of Philosophy}}</ref>

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.<ref name="jw-iep" />

Levine does not think that the explanatory gap means that consciousness is not physical; he is open to the idea that the explanatory gap is only an [[Epistemology|epistemological]] problem for physicalism.<ref name="jw-iep" /> In contrast, Chalmers thinks that the hard problem of consciousness does show that consciousness is not physical.<ref name=":0" />

==== Philosophical zombies ====
{{Main|Philosophical zombie}}
Philosophical zombies are a thought experiment commonly used in discussions of the hard problem.<ref>{{Cite web|last=Seager|first=William|title=Are Zombies Logically Possible?|url=https://www.utsc.utoronto.ca/~seager/zombie.html|access-date=2020-09-03|website=www.utsc.utoronto.ca}}</ref><ref>{{Cite journal|last1=Kaszniak|first1=Alfred W.|last2=Scott|first2=Andrew C.|date=2007|title=Zombie Killer|s2cid=14891432|journal=Association of Scientific Studies of Consciousness}}</ref> They are hypothetical beings physically identical to humans but that lack conscious experience.<ref>{{Cite web|last=Polger|first=Tom|title=Zombies: Entry|url=https://host.uniroma3.it/progetti/kant/field/zombies.htm|access-date=2020-09-03|website=host.uniroma3.it|archive-date=2020-06-15|archive-url=https://web.archive.org/web/20200615155145/http://host.uniroma3.it/progetti/kant/field/zombies.htm|url-status=dead}}</ref> 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.<ref>{{Citation|last=Kirk|first=Robert|title=Zombies|date=2019|url=https://plato.stanford.edu/archives/spr2019/entries/zombies/|encyclopedia=The Stanford Encyclopedia of Philosophy|editor-last=Zalta|editor-first=Edward N.|edition=Spring 2019|publisher=Metaphysics Research Lab, Stanford University|access-date=2020-09-03}}</ref> 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."<ref name=":3">[[David Chalmers]] (1996) ''The Conscious Mind: In Search of a Fundamental Theory'', pp. 153–56. Oxford University Press, New York, {{ISBN|0-19-511789-1}} (Pbk.)</ref> Daniel Dennett, a philosopher of mind, criticised the field's use of "the zombie hunch" which he deems an "embarrassment"<ref>Dennett, Daniel (1999), [https://www.nyu.edu/gsas/dept/philo/courses/consciousness/papers/DD-zombie.html "The Zombie Hunch: Extinction of an Intuition?"],{{dead link|date=January 2025}} ''Royal Institute of Philosophy Millennial Lecture''</ref> that ought to "be dropped like a hot potato".<ref name=":1">Dennett, Daniel; commentary on T. Moody, O. Flanagan and T. Polger. "[https://ase.tufts.edu/cogstud/dennett/papers/unzombie.htm The Unimagined Preposterous of Zombies]", ''Journal of Consciousness Studies'' vol. 2, no. 4, 1995, pp. 322–326.</ref>

==== Knowledge argument ====
{{Main|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.<ref name="Nida-Rümelin2019">{{cite encyclopedia|author1=Martine Nida-Rümelin|author2=Donnchadh O Conaill|title=Qualia: The Knowledge Argument|date=2019|encyclopedia=The Stanford Encyclopedia of Philosophy|editor=Edward N. Zalta|edition=Winter 2019|publisher=Metaphysics Research Lab, Stanford University|url=https://plato.stanford.edu/archives/win2019/entries/qualia-knowledge/|access-date=2020-09-03}}</ref> Chalmers believes<ref name=":3" /> that when Mary sees the colour red for the first time, she gains new knowledge — the knowledge of "what red looks like" — which is distinct from, and irreducible to, her prior physical knowledge of the brain or visual system. A stronger form of the knowledge argument<ref name="Nida-Rümelin2019"/> claims not merely that Mary would lack subjective ''knowledge'' of "what red looks like," but that she would lack knowledge of an objective ''fact'' about the world: namely, "what red looks like," a non-physical fact that can be learned only through direct experience (qualia). Others, such as Thomas Nagel, take a "[[physicalism|physicalist]]" position, disagree with the argument in its stronger and/or weaker forms.<ref name="Nida-Rümelin2019"/> For example, [[Thomas Nagel|Nagel]] put forward a "speculative proposal" of devising a language that could "explain to a person blind from birth what it is like to see."<ref name="Bat"/> The knowledge argument implies that such a language could not exist.

==Philosophical responses==
[[David Chalmers|David Chalmers']] formulation of the hard problem of consciousness provoked considerable debate within [[philosophy of mind]], as well as scientific research.<ref name="jw-iep"/>

[[File:Dualism-vs-Monism.png|thumb|A diagram showing the relationship between various views concerning the relationship between consciousness and the physical world]]
The hard problem is considered a problem primarily for [[physicalism|physicalist]] views of the mind (the view that the mind is a physical object or process), since physical explanations tend to be functional, or structural. Because of this, some physicalists have responded to the hard problem by seeking to show that it dissolves upon analysis. Other researchers accept the problem as real and seek to develop a theory of consciousness' place in the world that can solve it, by either modifying physicalism or abandoning it in favour of an alternative [[ontology]] (such as [[panpsychism]] or [[Mind–body dualism|dualism]]).
A third response has been to accept the hard problem as real but deny human cognitive faculties can solve it.

[[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%).<ref name="philpapers2020">{{cite journal
| last1 = Bourget
| first1 = David
| last2 = Chalmers
| first2 = David J.
| year = 2020
| title = Philosophers on Philosophy: The 2020 PhilPapers Survey
| journal = Philosophers' Imprint
| url = https://survey2020.philpeople.org
}}</ref>

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.<ref>{{cite journal| last1 = Bourget| first1 = David| last2 = Chalmers| first2 = David J.| year = 2014| title = What Do Philosophers Believe?| journal = Philosophical Studies| volume = 170| issue = 3| pages = 465–500| doi = 10.1007/s11098-013-0259-7| s2cid = 254936498| url = https://philpapers.org/rec/BOUWDP}}</ref> 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".<ref name="philpapers2020" />

Different solutions have been proposed to the hard problem of consciousness. The sections below taxonomizes the various responses to the hard problem. The shape of this taxonomy was first introduced by Chalmers in a 2003 literature review on the topic.<ref name="Chalmers-caipin">{{cite book|last1=Chalmers|first1=David|author-link=David Chalmers|editor1-last=Stich|editor1-first=Stephen P.|editor2-last=Warfield|editor2-first=Ted A.|title=Blackwell Guide to the Philosophy of Mind|date=2003|publisher=Blackwell|location=Malden, MA|chapter=Consciousness and its Place in Nature|pages=102–142|isbn=9780470998762|doi=10.1002/9780470998762.ch5}}</ref> The labelling convention of this taxonomy has been incorporated into the technical vocabulary of analytic philosophy, being used by philosophers such as Adrian Boutel,<ref>{{cite journal| last = Boutel| first = Adrian| year = 2013| title = How to be a Type-C Physicalist| journal = Philosophical Studies| volume = 164| issue = 2| pages = 301–320| doi = 10.1007/s11098-012-9854-2| s2cid = 254941872| url = https://philpapers.org/rec/BOUHTB| url-access = subscription}}</ref> Raamy Majeed,<ref name="majeed2016" /> Janet Levin,<ref name="Levin 2008 402–425">{{cite journal
| last = Levin
| first = Janet
| year = 2008
| title = Taking Type-B Materialism Seriously
| journal = Mind and Language
| volume = 23
| issue = 4
| pages = 402–425
| doi = 10.1111/j.1468-0017.2008.00349.x
| url = https://philpapers.org/rec/LEVTTM
| url-access = subscription
}}</ref> Pete Mandik & Josh Weisberg,<ref>{{cite book
| last1 = Mandik
| first1 = Pete
| last2 = Weisberg
| first2 = Josh
| year = 2008
| title = Type-Q Materialism
| editor-first = Chase
| editor-last = Wrenn
| publisher = Peter Lang Publishing Group
| url = https://philpapers.org/rec/MANTM
}}
</ref> Roberto Pereira,<ref>{{cite journal
| last = Pereira
| first = Roberto Horácio Sá
| year = 2016
| title = In Defence of Type-A Materialism
| journal = Diametros
| volume = 49
| issue = 49
| pages = 68–83
| doi = 10.13153/diam.49.2016.921
| url = https://philpapers.org/rec/PERIDO-3
}}
</ref> and Helen Yetter-Chappell.<ref>{{cite journal| last = Yetter-Chappell| first = Helen| year = 2017| title = Dissolving Type-B Physicalism| journal = Philosophical Perspectives| volume = 31| issue = 1| pages = 469–498| doi = 10.1111/phpe.12099| url = https://philpapers.org/rec/YETDTP-2}}
</ref>

===Type-A Materialism===
{{further|Reductive materialism|A priori physicalism}}
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. So, once all the relevant functions and behaviours have been accounted for, there will not be any facts left over in need of explanation.<ref name="Chalmers-caipin"/> Thinkers who subscribe to type-A materialism include [[Paul Churchland|Paul]] and [[Patricia Churchland]], [[Daniel Dennett]], [[Keith Frankish]], and [[Thomas Metzinger]].

Some type-A materialists believe in the reality of phenomenal consciousness but believe it is nothing extra in addition to certain functions or behaviours. This view is sometimes referred to as ''strong reductionism''.<ref name="jw-iep"/><ref name="Chalmers-caipin"/> Other type-A materialists may reject the existence of phenomenal consciousness entirely. This view is referred to as [[eliminative materialism]] or [[illusionism (consciousness)|illusionism]].<ref name="sep-elim"/><ref name="frankish-2016">{{cite journal
|last=Frankish
|first=K.
|year=2016
|title=Illusionism as a theory of consciousness
|journal=Journal of Consciousness Studies
|volume=23
|issue=11–12
|pages=11–39
}}</ref><ref name="dennett 2016">{{cite journal
| last = Dennett
| first = Daniel
| year = 2016
| title = Illusionism as the Obvious Default Theory of Consciousness
| journal = Journal of Consciousness Studies
| volume = 23
| issue = 11–12
| pages = 65–72
| url = https://philpapers.org/rec/DENIAT-3
}}
</ref>

====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.<ref name="jw-iep"/>

Broadly, strong reductionists accept that conscious experience is real but argue it can be fully understood in functional terms as an emergent property of the material brain.<ref name="jw-iep"/> In contrast to weak reductionists (see above), strong reductionists reject ideas used to support the existence of a hard problem (that the same functional organization could exist without consciousness, or that a blind person who understood vision through a textbook would not know everything about sight) as simply mistaken intuitions.<ref name="jw-iep"/><ref name="Chalmers-caipin"/>

A notable family of strong reductionist accounts are the [[higher-order theories of consciousness]].<ref>{{cite encyclopedia|first=Peter|last=Carruthers|author-link=Peter Carruthers (philosopher)|title=Higher-order theories of consciousness|encyclopedia=[[Stanford Encyclopedia of Philosophy]]|url=http://plato.stanford.edu/entries/consciousness-higher/|date=2016|publisher=Metaphysics Research Lab, Stanford University}}</ref><ref name="jw-iep"/> In 2005, the philosopher [[Peter Carruthers (philosopher)|Peter Carruthers]] wrote about "recognitional concepts of experience", that is, "a capacity to recognize [a] type of experience when it occurs in one's own mental life," and suggested that such a capacity could explain phenomenal consciousness without positing qualia.<ref name=Carruthers>{{cite book|title=Consciousness: essays from a higher-order perspective|chapter=Phenomenal concepts and higher-order experiments|last=Carruthers|first=Peter|author-link=Peter Carruthers (philosopher)|chapter-url=https://books.google.com/books?id=FKI4flNaGjUC&pg=PA79|pages=79 ''ff''|isbn=978-0191535048|publisher=Oxford University Press|year=2005}}</ref> On the higher-order view, since consciousness is a representation, and representation is fully functionally analysable, there is no hard problem of consciousness.<ref name="jw-iep"/>

The philosophers Glenn Carruthers and Elizabeth Schier said in 2012 that the main arguments for the existence of a hard problem—[[philosophical zombies]], [[Mary's room]], and [[What Is it Like to Be a Bat?|Nagel's bats]]—are only persuasive if one already assumes that "consciousness must be independent of the structure and function of mental states, i.e. that there is a hard problem." Hence, the arguments [[beg the question]]. The authors suggest that "instead of letting our conclusions on the thought experiments guide our theories of consciousness, we should let our theories of consciousness guide our conclusions from the thought experiments."<ref name=CarruthersSchier2012>{{cite conference|last1=Carruthers|first1=Glenn|last2=Schier|first2=Elizabeth|title=Dissolving the hard problem of consciousness|book-title=Consciousness Online fourth conference|date=2012|url=http://consciousnessonline.files.wordpress.com/2012/01/disolvinghardproblem.pdf|access-date=7 July 2014}}</ref>

The philosopher [[Massimo Pigliucci]] argued in 2013 that the hard problem is misguided, resulting from a "category mistake".<ref name=Pigliucci2013/> He said: "Of course an explanation isn't the same as an experience, but that's because the two are completely independent categories, like colors and triangles. It is obvious that I cannot experience what it is like to be you, but I can potentially have a complete explanation of how and why it is possible to be you."<ref name="Pigliucci2013"/>

In 2017, the philosopher Marco Stango, in a paper on [[John Dewey]]'s approach to the problem of consciousness (which preceded Chalmers' formulation of the hard problem by over half a century), noted that Dewey's approach would see the hard problem as the consequence of an unjustified assumption that feelings and functional behaviours are not the same physical process: "For the Deweyan philosopher, the 'hard problem' of consciousness is a 'conceptual fact' only in the sense that it is a {{em|philosophical mistake}}: the mistake of failing to see that the physical can be had as an episode of immediate sentiency."<ref>{{cite journal|last=Stango|first=Marco|date=Summer 2017|title=A Deweyan assessment of three major tendencies in philosophy of consciousness|journal=Transactions of the Charles S. Peirce Society|volume=53|issue=3|pages=466–490|doi=10.2979/trancharpeirsoc.53.3.06|s2cid=148690536|url=http://muse.jhu.edu/article/680916|url-access=subscription}}</ref>

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.<ref name ="Metzinger">{{cite web|last1=Harris|first1=Sam|author-link= Sam Harris|title=Making Sense #96|url=https://samharris.org/subscriber-extras/96-nature-consciousness/|website=SamHarris.org|publisher=Sam Harris|access-date=27 August 2020|quote=(25.45) TM:I think it will not be a mystery. Life is not a mystery anymore, but a hundred and fifty years ago many people thought that this is an irreducible mystery. (25:57) Harris:So you’re not a fan anymore, if you ever were, of the framing by David Chalmers of the Hard Problem of Consciousness? Metzinger: No, that’s so boring. I mean, that’s last century. I mean, you know, we all respect Dave [Chalmers], and we know he is very smart and has got a very fast mind, no debate about that. But conceivability arguments are just very, very weak. If you have an ill-defined folk psychological umbrella term like “consciousness”, then you can pull off all kinds of scenarios and zombie thought experiments. It doesn’t really… It helped to clarify some issues in the mid 90’s, but the consciousness community has listened to this and just moved on. I mean nobody of the serious researchers in the field thinks about this anymore, but it has taken on like a folkloristic life of its own. A lot of people talk about the Hard Problem who wouldn’t be able to state what it consists in now.}}</ref> Brian Jonathan Garrett has also argued that the hard problem suffers from flaws analogous to those of vitalism.<ref>{{cite journal|last1=Garrett|first1=Brian Jonathan|title=What the History of Vitalism Teaches Us About Consciousness and the 'Hard Problem'|journal=Philosophy and Phenomenological Research|date=May 2006|volume=72|issue=3|pages=576–588|doi=10.1111/j.1933-1592.2006.tb00584.x}}</ref>

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.<ref name=Hacker>{{cite journal|title=Hacker's challenge|url=http://philpapers.org/rec/HACHC|last=Hacker|first=Peter|author-link=Peter Hacker|journal=The Philosophers' Magazine|volume=51|issue=51|pages=23–32|year=2010|doi=10.5840/tpm2010517|url-access=subscription}}</ref> 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."<ref name="Hacker"/> Hacker's critique extends beyond Chalmers and the hard problem, being directed against contemporary philosophy of mind and neuroscience more broadly. Along with the neuroscientist [[Max Bennett (scientist)|Max Bennett]], he has argued that most of contemporary neuroscience remains implicitly [[Dualism (philosophy of mind)|dualistic]] in its conceptualisations and is predicated on the ''[[Mereology|mereological]] fallacy'' of ascribing psychological concepts to the brain that can properly be ascribed only to the person as a whole.<ref name="schaal-review">{{cite journal|last1=Schaal|first1=David W.|title=Naming Our Concerns About Neuroscience: A Review of Bennett and Hacker's ''Philosophical Foundations of Neuroscience''|journal=Journal of the Experimental Analysis of Behavior|date=2005|volume=84|issue=3|pages=683–692|doi=10.1901/jeab.2005.83-05|pmid=16596986|pmc=1389787}}</ref> 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".<ref name=Hacker/>

====Eliminative materialism / Illusionism====
{{main|Eliminative materialism}}

Eliminative materialism or eliminativism is the view that many or all of the [[mental states]] used in [[folk psychology]] (i.e., common-sense ways of discussing the mind) do not, upon scientific examination, correspond to real brain mechanisms.<ref name="sep-elim">{{cite encyclopedia|last=Ramsey|first=William|editor-last=Zalta|editor-first=Edward N.|editor-link=Edward N. Zalta|encyclopedia=Stanford Encyclopedia of Philosophy|title=Eliminative Materialism|year=2019|url=https://plato.stanford.edu/entries/materialism-eliminative/|access-date=1 April 2019}}</ref> According the 2020 [[PhilPapers]] survey, 4.51% of philosophers surveyed subscribe to eliminativism.<ref name="philpapers2020" />

While [[Patricia Churchland]] and [[Paul Churchland]] have famously applied eliminative materialism to [[propositional attitudes]], philosophers including [[Daniel Dennett]], [[Georges Rey]], and [[Keith Frankish]] have applied it to [[qualia]] or [[phenomenal consciousness]] (i.e., conscious experience).<ref name="sep-elim"/> On their view, it is mistaken not only to believe there is a hard problem of consciousness, but to believe phenomenal consciousness exists at all.<ref name="frankish"/>{{r|dennett 2016}}

This stance has recently taken on the name of ''illusionism'': the view that phenomenal consciousness is an illusion. The term was popularized by the philosopher [[Keith Frankish]].<ref name="frankish-2016" /> Frankish argues that "illusionism" is preferable to "eliminativism" for labelling the view that phenomenal consciousness is an illusion. More substantively, Frankish argues that illusionism about phenomenal consciousness is preferable to realism about phenomenal consciousness. He states: "Theories of consciousness typically address the hard problem. They accept that phenomenal consciousness is real and aim to explain how it comes to exist. There is, however, another approach, which holds that phenomenal consciousness is an illusion and aims to explain why it seems to exist."<ref name="frankish"/> Frankish concludes that illusionism "replaces the hard problem with the illusion problem—the problem of explaining how the illusion of phenomenality arises and why it is so powerful."<ref name="frankish"/>

The philosopher [[Daniel Dennett]] was another prominent figure associated with illusionism. After Frankish published a paper in the [[Journal of Consciousness Studies]] titled ''Illusionism as a Theory of Consciousness,''<ref name="frankish-2016" /> Dennett responded with his own paper humorously titled ''Illusionism as the Obvious Default Theory of Consciousness.''<ref name="dennett 2016"/> Dennett had been arguing for the illusory status of consciousness since early on in his career. For example, in 1979 he published a paper titled ''On the Absence of [[Phenomenology (philosophy)|Phenomenology]]'' (where he argues for the nonexistence of phenomenal consciousness).<ref>{{cite book
| last = Dennett
| first = Daniel C.
| year = 1979
| chapter = On the Absence of Phenomenology
| editor-first = Donald F.
| editor-last = Gustafson
| editor2-first = Bangs L.
| editor2-last = Tapscott
| title = Body, Mind, and Method
| publisher = Kluwer Academic Publishers
| pages = 93–113
}}</ref> Similar ideas have been explicated in his 1991 book [[Consciousness Explained]].<ref name="Dennett1991">{{cite book
| last = Dennett
| first = Daniel C.
| title = Consciousness Explained
| year = 1991
| publisher = Penguin Books
}}</ref> Dennett argues that the so-called "hard problem" will be solved in the process of solving what Chalmers terms the "easy problems".<ref name=Dennett/> He compares consciousness to stage magic and its capability to create extraordinary illusions out of ordinary things.<ref name=Dennett3/> To show how people might be commonly fooled into overstating the accuracy of their introspective abilities, he describes a phenomenon called [[change blindness]], a visual process that involves failure to detect scenery changes in a series of alternating images.<ref name=Dennett2/>{{page needed|date=January 2021}} He accordingly argues that consciousness need not be what it seems to be based on introspection. To address the question of the hard problem, or how and why physical processes give rise to experience, Dennett states that the phenomenon of having experience is nothing more than the performance of functions or the production of behaviour, which can also be referred to as the easy problems of consciousness.<ref name=Dennett/> Thus, Dennett argues that the hard problem of experience is included among—not separate from—the easy problems, and therefore they can only be explained together as a cohesive unit.<ref name=Dennett3/>

Eliminativists differ on the role they believe [[intuition|intuitive]] judgement plays in creating the apparent reality of consciousness. The philosopher [[Jacy Reese Anthis]] is of the position that this issue is born of an overreliance on intuition, calling philosophical discussions on the topic of consciousness a form of "intuition jousting".<ref name="anthis">{{cite book|last1=Anthis|first1=Jacy|title=Biologically Inspired Cognitive Architectures 2021|chapter=Consciousness Semanticism: A Precise Eliminativist Theory of Consciousness|series=Studies in Computational Intelligence|date=2022|volume=1032|pages=20–41|doi=10.1007/978-3-030-96993-6_3|isbn=978-3-030-96992-9|chapter-url=https://philarchive.org/rec/ANTCSA|access-date=7 August 2022}}</ref> But when the issue is tackled with "formal argumentation" and "precise semantics" then the hard problem will dissolve.<ref name="anthis" /> The philosopher Elizabeth Irvine, in contrast, can be read as having the opposite view, since she argues that phenomenal properties (that is, properties of consciousness) do not exist in our [[folk psychology|common-sense view of the world]]. She states that "the hard problem of consciousness may not be a genuine problem for non-philosophers (despite its overwhelming obviousness to philosophers)."<ref>{{cite book|last=Irvine|first=Elizabeth|date=2013|title=Consciousness as a scientific concept: a philosophy of science perspective|series=Studies in brain and mind|volume=5|location=Dordrecht; New York|publisher=[[Springer-Verlag]]|isbn=9789400751729|page=[https://books.google.com/books?id=jO4HNB7OoUgC&pg=PA167 167]}}</ref>

A complete illusionist theory of consciousness must include the description of a [[Mechanism (biology)|mechanism]] by which the illusion of subjective experience is had and reported by people. Various philosophers and scientists have proposed possible theories.<ref name="meta-problem">{{cite journal|last1=Chalmers|first1=David|title=The Meta-Problem of Consciousness|journal=Journal of Consciousness Studies|date=2018|volume=25|issue=9–10|pages=6–61|url=http://consc.net/papers/metaproblem.pdf|access-date=6 February 2019}}</ref> 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.<ref name="Consciousness as engineering"/><ref name="Consciousness as engineering2"/>

===== Criticisms =====
The main criticisms of eliminative materialism and illusionism hinge on the counterintuitive nature of the view. Arguments of this form are called ''Moorean Arguments''. A Moorean argument seeks to undermine the conclusion of an argument by asserting that the [[negation]] of that conclusion is more certain than the [[premise]]s of the argument.<ref>{{cite journal
| last = Scarfone
| first = Matthew
| year = 2022
| title = Using and Abusing Moorean Arguments
| journal = Journal of the American Philosophical Association
| volume = 8
| issue = 1
| pages = 52–71
| doi = 10.1017/apa.2020.47
| s2cid = 239672728
| url = https://philpapers.org/rec/SCAUAA-2
}}</ref>

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.<ref group="note">"But, without any delusive representations of images or phantasms, I am most certain that I am, and that I know and delight in this. In respect to these truths I am not at all afraid of the arguments of the Academians, who say, What if you are deceived? For if I am deceived, I am. For he who is not, cannot be deceived..."</ref><ref>{{cite book
| last = Augustine of Hippo
| title = City of God
| chapter = Book 11, Chapter 26
}}</ref>

{{Wikisource|Discourse on the Method/Part 4|Descartes' Discourse on the Method/Part 4}}
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").<ref>{{cite book
| last = Descartes
| first = René
| year = 1637
| title = Discourse on the Method
| chapter = 4
}}</ref> 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.<ref>{{cite book
| last = Descartes
| first = René
| year = 1641
| title = Meditations on First Philosophy
| chapter = Second Meditation
}}</ref>

This same general argumentative structure is still in use today. For example, 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.<ref name="chalmers202-illusionism">{{cite journal
| last = Chalmers
| first = David
| year = 2020
| title = Debunking Arguments for Illusionism
| journal = Journal of Consciousness Studies
| volume = 27
| issue = 5–6
| pages = 258–281
| url = https://philpapers.org/rec/CHADAF-2
}}</ref> 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."<ref name="chalmers2020-illusionism">{{cite journal| last = Chalmers| first = David| year = 2002| title = Debunking Arguments for Illusionism| journal = Journal of Consciousness Studies| volume = 27| issue = 5–6| pages = 258–281| url = https://philpapers.org/rec/CHADAF-2}}</ref>

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."<ref>
{{cite web
|last=Strawson
|first=G.
|year=2018
|title=The Consciousness Deniers
|url=https://www.nybooks.com/daily/2018/03/13/the-consciousness-deniers/
|website=The New York Review of Books
}}</ref> 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."<ref>
{{cite book
|last=Koch
|first=Christof
|year=2019
|title=The Feeling of Life Itself: Why Consciousness is Everywhere But Can't be Computed
|publisher=MIT Press
|pages=2
}}</ref> Koch takes the prevalence of eliminativism as evidence that "much of twentieth-century analytic philosophy has gone to the dogs".<ref>
{{cite book
|last=Koch
|first=Christof
|year=2019
|title=The Feeling of Life Itself: Why Consciousness is Everywhere But Can't be Computed
|publisher=MIT Press
|pages=3
}}</ref>

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.<ref>{{Cite web |last=Frankish |first=Keith |date=2022-12-02 |title=A dilemma for illusionists — and another for realists! |url=https://www.keithfrankish.com/blog/a-dilemma-for-illusionists-and-another-for-realists/ |access-date=2025-02-01 |website=Keith Frankish |language=en-GB}}</ref>

===Type-B Materialism===
{{further|Phenomenal concept strategy|A posteriori physicalism}}
Type-B Materialism, also known as ''Weak Reductionism'' or ''[[A priori and a posteriori|A Posteriori]] Physicalism'', is the view that the hard problem stems from human psychology, and is therefore not indicative of a genuine [[ontology|ontological]] gap between consciousness and the physical world.<ref name="jw-iep"/> Like Type-A Materialists, Type-B Materialists are committed to [[physicalism]]. Unlike Type-A Materialists, however, Type-B Materialists ''do'' accept inconceivability arguments often cited in support of the hard problem, but with a key caveat: that inconceivability arguments give us insight only into how the human mind ''tends to conceptualize'' the relationship between mind and matter, but not into what the true nature of this relationship actually is.<ref name="jw-iep"/><ref name="Chalmers-caipin"/> According to this view, there is a gap between two ways of knowing (introspection and neuroscience) that will not be resolved by understanding all the underlying neurobiology, but still believe that consciousness and neurobiology are one and the same in reality.<ref name="jw-iep"/>

While Type-B Materialists all agree that intuitions about the hard problem are psychological rather than ontological in origin, they differ as to whether our intuitions about the hard problem are innate or culturally conditioned. This has been dubbed the "hard-wired/soft-wired distinction."<ref>{{cite journal
| last = Balmer
| first = A.
| year = 2020
| title = Soft-Wired Illusionism vs. the Meta-Problem of Consciousness
| journal = Journal of Consciousness Studies
| volume = 27
| issue = 5–6
| pages = 26–37
| url = https://philpapers.org/rec/BALSIV
}}</ref><ref name="DCuniversal">{{cite journal
| last = Chalmers
| first = David
| year = 2020
| title = Is the Hard Problem of Consciousness Universal?
| journal = Journal of Consciousness Studies
| volume = 27
| issue = 5–6
| pages = 227–257
}}</ref> 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".<ref name="DCuniversal" /> Those that believe our intuitions are culturally conditioned subscribe to the "soft-wired view". Unless otherwise specified, the term ''Type-B Materialism'' refers to the hard-wired view.<ref name="DCuniversal" />

Notable philosophers who subscribe to Type-B Materialism include [[David Papineau]],<ref>{{cite journal
| last = Papineau
| first = D.
| year = 2019
| title = Response to Chalmers' 'The Meta-Problem of Consciousness'
| journal = Journal of Consciousness Studies
| volume = 26
| issue = 9–10
| pages = 173–181
| url = https://philpapers.org/rec/PAPRTC-6
}}</ref> [[Joseph Levine (philosopher)|Joseph Levine]],<ref name="J. Levine 1999, pp 3">J. Levine, "Conceivability, Identity, and the Explanatory Gap" in Stuart R. Hameroff, Alfred W. Kaszniak and David Chalmers (eds.), ''Towards a Science of Consciousness III: The Third Tucson Discussions and Debates'', The MIT Press, 1999,. pp 3–12.</ref> and Janet Levine.<ref name="Levin 2008 402–425"/>

====The "hard-wired view"====
Joseph Levine (who formulated the notion of the [[explanatory gap]]) states: "The explanatory gap argument doesn't demonstrate a gap in nature, but a gap in our understanding of nature."<ref name="J. Levine 1999, pp 3"/> He nevertheless contends that full scientific understanding will not close the gap,<ref name="jw-iep"/> and that analogous gaps do not exist for other [[Identity (philosophy)|identities]] in nature, such as that between water and H<sub>2</sub>O.<ref name="rjg-iep">{{cite web|last1=Gennaro|first1=Rocco J.|title=Consciousness|url=https://www.iep.utm.edu/consciou|website=Internet Encyclopedia of Philosophy}}</ref> 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.<ref name="block-stalnaker">{{cite journal|last1=Block|first1=Ned|last2=Stalnaker|first2=Robert|title=Conceptual Analysis, Dualism, and the Explanatory Gap|journal=The Philosophical Review|date=1999|volume=108|issue=1|pages=1–46|jstor=2998259|doi=10.2307/2998259|citeseerx=10.1.1.693.2421|url=http://www.nyu.edu/gsas/dept/philo/faculty/block/papers/ExplanatoryGap.pdf}}</ref><ref name="harder-problem"/>

To explain why these two ways of knowing (i.e. third-person scientific observation and first-person introspection) yield such different understandings of consciousness, weak reductionists often invoke the ''phenomenal concepts strategy'', which argues the difference stems from our inaccurate [[Phenomenal consciousness|phenomenal]] concepts (i.e., how we think about consciousness), not from the nature of consciousness itself.<ref name="stoljar-2005">{{cite journal|last1=Stoljar|first1=Daniel|title=Physicalism and Phenomenal Concepts|journal=Mind & Language|date=2005|volume=20|issue=5|pages=469–494|doi=10.1111/j.0268-1064.2005.00296.x}}</ref><ref name="chalmers-pceg">{{cite book|last1=Chalmers|first1=David|editor1-last=Alter|editor1-first=Torin|editor2-last=Walter|editor2-first=Sven|title=Phenomenal Concepts and Phenomenal Knowledge: New Essays on Consciousness and Physicalism|date=2006|publisher=Oxford University Press|isbn=9780195171655|chapter-url=http://consc.net/papers/pceg.pdf|access-date=27 March 2019|chapter=Phenomenal Concepts and the Explanatory Gap}}</ref> By this view, the hard problem of consciousness stems from a dualism of concepts, not from a dualism of properties or substances.<ref name="jw-iep"/>

====The "soft-wired view"====
Some consciousness researchers have argued that the hard problem is a cultural artifact, unique to contemporary Western Culture. This is similar to Type-B Materialism, but it makes the further claim that the psychological facts that cause us to intuit the hard problem are not innate, but culturally conditioned. Notable researchers who hold this view include [[Anna Wierzbicka]],<ref name="AW2019">{{cite journal
| last = Wierzbicka
| first = A.
| year = 2019
| title = From 'Consciousness' to 'I Think, I Feel, I Know': A Commentary on David Chalmers
| journal = Journal of Consciousness Studies
| volume = 26
| issue = 9–10
| pages = 257–269
}}</ref> Hakwan Lau and Matthias Michel.<ref>{{cite journal
| last1 = Lau
| first1 = Hakwan
| last2 = Michel
| first2 = Matthias
| year = 2019
| title = A Socio-Historical Take on the Meta-Problem of Consciousness
| journal = Journal of Consciousness Studies
| volume = 26
| issue = 9–10
| pages = 136–147
}}</ref>

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 "[[Parochialism|parochially]] English."<ref name="AW2019"/> Weirzbicka calls David Chalmers out by name for using these words, arguing that if philosophers "were to use panhuman concepts expressed in crosstranslatable words" (such as ''know'', ''think'', or ''feel'') then the hard problem would dissolve.<ref name="AW2019"/> David Chalmers has responded to these criticisms by saying that he will not "apologise for using technical terms in an academic article . . . they play a key role in efficient communication in every discipline, including Wierzbicka’s".<ref name="DCuniversal" />

===Type-C Materialism===

Type-C materialists acknowledge a distinction between knowledge and experience<ref name="ChalmersGreen-aia"/> without asserting a more complete explanation for the experiential phenomenon. One taking this view would admit that there is an [[explanatory gap]] for which no answer to date may be satisfactory, but trust that inevitably the gap will be closed.<ref name="Chalmers-caipin"/> This is described by analogy to progression in other areas of science, such as [[mass-energy equivalence]] which would have been unfathomable in ancient times,<ref name="Chalmers-caipin"/> [[abiogenesis]] which was once considered paradoxical from an evolutionary framework,<ref>{{cite web | url=https://www.allaboutscience.org/abiogenesis.htm | title=Abiogenesis }}</ref><ref name="ChalmersGreen-aia">{{cite web | url=https://www.youtube.com/watch?v=hru5d_wsu7g | title=Is the hard problem of consciousness really that hard? &#124; Brian Greene and Pat Churchland lock horns | website=[[YouTube]] | date=9 July 2022 }}</ref> 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<ref name="Dennett1991"/><ref>''Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness.'' Daniel Stoljar. Oxford University Press.</ref> but just as resolvable as any other question in [[neuroscience]].

Because the explanatory question of consciousness is evaded, type-C materialism does not presuppose<ref name="RomainBrette">{{cite web | url=http://romainbrette.fr/notes-on-consciousness-x-why-i-am-not-a-panpsychist-reading-notes-on-philip-goffs-galileos-error/ | title=Notes on consciousness. (X) Why I am not a panpsychist - Reading notes on Philip Goff's "Galileo's error" | date=25 January 2022 }}</ref> the descriptive question, for instance that there is any self-consciousness, wakefulness, or even sentience<ref>Jan 14, 2014. "Consciousness". Sections 2.1 and 3. ''Stanford Encyclopedia of Philosophy.'' https://plato.stanford.edu/entries/consciousness/</ref> in a rock. Principally, the basis for the argument arises from the apparently high correlation of consciousness with living brain tissue,<ref>May 13, 2022. "Panpsychism". Section 4.4.2. ''Stanford Encyclopedia of Philosophy.'' https://plato.stanford.edu/entries/panpsychism/</ref> thereby rejecting [[panpsychism]]<ref name="RomainBrette"/> without explicitly formulating physical causation. More specifically this position denies the existence of [[philosophical zombies]]<ref name=CarruthersSchier2012/> for which there is an absence of data and no proposed method of testing.<ref>{{cite web | url=https://selfawarepatterns.com/2016/10/03/the-problems-with-philosophical-zombies/ | title=The problems with philosophical zombies | date=3 October 2016 }}</ref><ref>''Thinking about Consciousness.'' Chapter 3. "The Impossibility of Zombies". David Papineau. Oxford Academic.</ref> 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<ref name="Chalmers-caipin"/> depending on scientific discovery and its interpretation. With evidence of [[emergence]], it resolves to strong reductionism under type A. With a different, possibly cultural paradigm for understanding consciousness, it resolves to type-B materialism.<ref name=":2"/> If consciousness is explained by the [[quantum mind]], then it resolves to property dualism under type D.<ref name="Quantum Approaches to Consciousness">{{cite web|url=http://plato.stanford.edu/entries/qt-consciousness/|title=Quantum Approaches to Consciousness|publisher=Stanford Encyclopedia of Philosophy|orig-year=First published Tue Nov 30, 2004 |date=May 19, 2011}}</ref> With characterisation of intrinsic properties in physics extending beyond structure and dynamics, it could resolve to type-F monism.<ref name="Chalmers-caipin"/>

Richard Brown has defended an unorthodox form of type-C materialism which states that the hard problem cannot be decided ''a priori'' and the two major positions (physicalism and dualism) can only be vindicated empirically, i.e. through scientific advances. His version of type-C materialism is unorthodox because he claims that it does not collapse into the other positions. He uses "reverse zombie" and "reverse knowledge" thought experiments (anti-dualist versions of the standard anti-physicalist arguments) to show that ''a priori'' arguments beg the question and are only useful for revealing one's own intuitions, whether physicalist or dualist. The only reason why such thought experiments, both anti-physicalist and anti-dualist, seem intuitive is because they are ''prima facie'' conceivable but not ideally conceivable, where ideal conceivability involves knowledge of the completed science and thus the ability to deduce ''a priori'' the discovered identities, in the same way that "water is H₂O" was discovered empirically but the identity is deducible ''a priori''.<ref name="Brown2010">{{cite journal|last1=Brown|first1=Richard|title=Deprioritizing the A Priori Arguments Against Physicalism|journal=Journal of Consciousness Studies|date=2010|volume=17|issue=3–4|pages=47–69|url=http://philpapers.org/archive/BRODTA.pdf |via=PhilPapers |url-status=live |archive-url=https://web.archive.org/web/20240126233332/https://philpapers.org/archive/BRODTA.pdf |archive-date= Jan 26, 2024}}</ref>

===Type-D Dualism===
{{main|Dualism (philosophy of mind)|Interactionism (philosophy of mind)|Epiphenomenalism}}
[[Dualism (philosophy of mind)|Dualism]] views consciousness as either a non-physical [[Substance theory|substance]] separate from the brain or a non-physical [[Property (philosophy)|property]] of the physical brain.<ref name="iep-dualism">{{cite encyclopedia|last=Calef|first=Scott|encyclopedia=Internet Encyclopedia of Philosophy|title=Dualism and Mind|year=2014|url=https://www.iep.utm.edu/dualism/#H3|access-date=8 February 2019}}</ref> Dualism is the view that the mind is irreducible to the physical body.<ref name="iep-dualism"/> There are multiple dualist accounts of the causal relationship between the mental and the physical, of which interactionism and epiphenomenalism are the most common today. Interactionism posits that the mental and physical causally impact one another, and is associated with the thought of [[René Descartes]] (1596–1650).<ref name="Chalmers-caipin"/> Epiphenomenalism holds the mental is causally dependent on the physical, but does not in turn causally impact it.<ref name="Chalmers-caipin"/>

In contemporary philosophy, interactionism has been defended by philosophers including [[Martine Nida-Rümelin]],<ref name="mnr-dualism">{{cite encyclopedia|last1=Nida-Rümelin|first1=Martine|editor1-last=McLaughlin|editor1-first=Brian|editor2-last=Cohen|editor2-first=Jonathan|encyclopedia=Contemporary Debates in Philosophy of Mind|edition=1st|title=Dualist Emergentism|date=2006|publisher=Wiley-Blackwell|location=Malden, MA|isbn=978-1-405-11761-6|url=https://www.newdualism.org/papers/M.Nida-Rumelin/Nida-Rumelin-Dualist%20Emergentism%20-%2018%203%2006.pdf|access-date=1 February 2019}}</ref> while epiphenomenalism has been defended by philosophers including [[Frank Cameron Jackson|Frank Jackson]]<ref name="jackson-1">{{cite journal|last1=Jackson|first1=Frank|title=Epiphenomenal Qualia|journal=The Philosophical Quarterly|date=1982|volume=32|issue=127|pages=127–136|doi=10.2307/2960077|jstor=2960077|doi-access=free}}</ref><ref name="jackson-2">{{cite journal|last1=Jackson|first1=Frank|title=What Mary Didn't Know|journal=The Journal of Philosophy|date=1986|volume=83|issue=5|pages=291–295|doi=10.2307/2026143|jstor=2026143|s2cid=19000667}}</ref> (although Jackson later changed his stance to physicalism).<ref name="jackson-3">{{cite journal|last1=Jackson|first1=Frank|title=Mind and Illusion|journal=Royal Institute of Philosophy Supplements|date=2003|volume=53|pages=251–271|doi=10.1017/S1358246100008365|s2cid=170304272|url=https://www.researchgate.net/publication/231993032|access-date=6 February 2019}}</ref> Chalmers has also defended versions of both positions as plausible.<ref name="Chalmers-caipin"/> Traditional dualists such as Descartes believed the mental and the physical to be two separate [[Substance theory|substances]], or fundamental types of entities (hence "[[substance dualism]]"); some more recent dualists, however, accept only one substance, the physical, but state it has both mental and physical [[Property (philosophy)|properties]] (hence "[[property dualism]]").<ref name="iep-dualism"/>

===Type-E Dualism===
{{Expand section|See talk page|date=June 2023}}

===Type-F Monism===
{{main|Panpsychism|Neutral monism}}
Meanwhile, [[panpsychism]] and [[neutral monism]], broadly speaking, view consciousness as intrinsic to matter.<ref name="Chalmers-caipin"/> In its most basic form, panpsychism holds that all physical entities have minds (though its proponents take more qualified positions),<ref name="chalmers-panpsych">{{cite book|last1=Chalmers|first1=David|author-link=David Chalmers|editor1-last=Bruntrup|editor1-first=Godehard|editor2-last=Jaskolla|editor2-first=Ludwig|title=Panpsychism: Contemporary Perspectives|date=2016|publisher=Oxford University Press|location=Oxford, UK|chapter=Panpsychism and Panprotopsychism|pages=19–47|isbn=9780199359967|doi=10.1093/acprof:oso/9780199359943.003.0002}}</ref> 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.<ref name="sep-nm">{{cite encyclopedia|last=Stubenberg|first=Leopold|editor-last=Zalta|editor-first=Edward N.|editor-link=Edward N. Zalta|encyclopedia=Stanford Encyclopedia of Philosophy|title=Neutral monism|year=2016|url=https://plato.stanford.edu/entries/neutral-monism/|access-date=15 September 2018}}</ref>

Forms of panpsychism and neutral monism were defended in the early twentieth century by the psychologist [[William James]],<ref>{{cite journal|last1=Koch|first1=Christof|title=Is Consciousness Universal?|url=https://www.scientificamerican.com/article/is-consciousness-universal/|website=Scientific American|date=January 2014|access-date=13 September 2018|doi=10.1038/scientificamericanmind0114-26|url-access=subscription}}</ref><ref name="sep-panpsych">{{cite encyclopedia|last=Goff|first=Philip|author2=Seager|author2-first=William|author3=Allen-Hermanson|author3-first=Sean|editor-last=Zalta|editor-first=Edward N.|editor-link=Edward N. Zalta|encyclopedia=Stanford Encyclopedia of Philosophy|title=Panpsychism|year=2017|url=https://plato.stanford.edu/entries/panpsychism/|access-date=15 September 2018}}</ref><ref group=note>There has been debate over how best to characterize James' position. The ''Stanford Encyclopedia of Philosophy'' states: "James’s commitment to panpsychism remains somewhat controversial, since he also advanced a cogent set of objections against a version of the view, which he labelled the 'mind dust' theory, in chapter six of The Principles of Psychology ([1890] 1981). These objections are the inspiration for the so-called 'combination problem', around which much of the twenty first century literature on panpsychism focuses."</ref> the philosopher [[Alfred North Whitehead]],<ref name="sep-panpsych"/> the physicist [[Arthur Eddington]],<ref name="pcp-2016">{{cite book|last1=Brüntrup|first1=Godehard|last2=Jaskolla|first2=Ludwig|editor1-last=Bruntrup|editor1-first=Godehard|editor2-last=Jaskolla|editor2-first=Ludwig|title=Panpsychism: Contemporary Perspectives|date=2016|publisher=Oxford University Press|location=Oxford, UK|chapter=Introduction|pages=1–16|isbn=9780199359967|doi=10.1093/acprof:oso/9780199359943.003.0001}}</ref><ref name="iep-panpsych">{{cite encyclopedia|last=Skrbina|first=David|encyclopedia=Internet Encyclopedia of Philosophy|title=Panpsychism|url=https://www.iep.utm.edu/panpsych/|access-date=8 February 2019}}</ref> and the philosopher [[Bertrand Russell]],<ref name="chalmers-panpsych"/><ref name="sep-nm"/> and interest in these views has been revived in recent decades by philosophers including [[Thomas Nagel]],<ref name="sep-panpsych"/> [[Galen Strawson]],<ref name="sep-panpsych"/><ref name="strawson">{{cite journal|last1=Strawson|first1=Galen|title=Realistic monism: Why physicalism entails panpsychism|journal=Journal of Consciousness Studies|date=2006|volume=13|issue=10/11|pages=3–31|url=http://www.newdualism.org/papers/G.Strawson/strawson_on_panpsychism.pdf|access-date=15 September 2018}}</ref> [[Philip Goff (philosopher)|Philip Goff]],<ref name="sep-panpsych" /> and David Chalmers.<ref name="chalmers-panpsych"/> Chalmers describes his overall view as "naturalistic dualism",<ref name="Chalmers"/> but he says panpsychism is in a sense a form of physicalism,<ref name="Chalmers-caipin"/> as does Strawson.<ref name="strawson"/> Proponents of panpsychism argue it solves the hard problem of consciousness parsimoniously by making consciousness a fundamental feature of reality.<ref name="jw-iep"/><ref name="pn-goff">{{cite web|last1=Goff|first1=Philip|title=The Case for Panpsychism|url=https://philosophynow.org/issues/121/The_Case_For_Panpsychism|website=Philosophy Now|access-date=3 October 2018|date=2017}}</ref>

====Idealism and cosmopsychism====
{{Main|Idealism}}
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.<ref>{{Cite journal|url=https://philpapers.org/rec/KASTUI|title=The Universe in Consciousness|journal=Journal of Consciousness Studies|year=2018|volume=25|issue=5–6|pages=125–155|last1=Kastrup|first1=Bernardo}}</ref> [[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.<ref name="shani-keppler-2018">{{cite journal|last1=Shani|first1=Itay|last2=Keppler|first2=Joachim|title=Beyond combination: how cosmic consciousness grounds ordinary experience|journal=Journal of the American Philosophical Association|date=2018|volume=4|issue=3|pages=390–410|doi=10.1017/apa.2018.30|s2cid=125246376|doi-access=free}}</ref><ref name="shani-2015">{{cite journal|last1=Shani|first1=Itay|title=Cosmopsychism: A holistic approach to the metaphysics of experience|journal=Philosophical Papers|date=2015|volume=44|issue=3|pages=389–437|doi=10.1080/05568641.2015.1106709|s2cid=146624784}}</ref><ref name="albahari-2019">{{cite journal|last1=Albahari|first1=Miri|title=Perennial Idealism: A Mystical Solution to the Mind–Body Problem|journal=Philosophers' Imprint|date=2019|volume=19|issue=44|pages=1–37|s2cid=211538796}}</ref>

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.<ref name="kastrup-2018">{{cite journal|last1=Kastrup|first1=Bernardo|title=Conflating abstraction with empirical observation: The false mind-matter dichotomy|journal=Constructivist Foundations|date=2018|volume=13|issue=3}}</ref> 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).<ref>{{Cite thesis|url=https://philarchive.org/rec/KASAIA-3|title=Analytic Idealism: A consciousness-only ontology|year=2019|publisher=Radboud University Nijmegen|type=PhD Thesis|last1=Kastrup|first1=Bernardo}}</ref> 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 [[Panpsychism#Conscious realism|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."<ref name="hoffman-2008">{{cite journal|last1=Hoffman|first1=Donald D.|title=Conscious Realism and the Mind–Body Problem|journal=Mind and Matter|date=2008|volume=6|issue=1|pages=87–121|s2cid=3175512}}</ref>

David Chalmers calls this form of idealism one of "the handful of promising approaches to the mind–body problem."<ref name="chalmers-idealism">{{cite encyclopedia|last=Chalmers|first=David J.|author-link=David Chalmers|editor-last=Seager|editor-first=William|editor-link=William Seager (philosopher)|encyclopedia=The Routledge Handbook of Panpsychism|title=Idealism and the Mind–Body Problem|publisher=Routledge|isbn=978-1138817135| url=http://consc.net/papers/idealism.pdf|access-date=2 December 2019|date=2020|quote=Overall, I think cosmic idealism is the most promising version of idealism, and is about as promising as any version of panpsychism. It should be on the list of the handful of promising approaches to the mind–body problem.}}</ref>

===New mysterianism===
{{Main|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.<ref name="mcginn-1989">{{cite journal|last1=McGinn|first1=Colin|title=Can We Solve the Mind–Body Problem?|journal=Mind|date=1989|volume=98|issue=391|pages=349–366|doi=10.1093/mind/XCVIII.391.349|jstor=2254848}}</ref><ref name="mcginn-2012"/> McGinn draws on [[Noam Chomsky]]'s distinction between problems, which are in principle solvable, and mysteries, which human cognitive faculties are unequipped to ever understand, and places the [[mind–body problem]] in the latter category.<ref name="mcginn-1989"/> His position is that a [[Metaphysical naturalism|naturalistic]] explanation does exist but that the human mind is [[Cognitive closure (philosophy)|cognitively closed]] to it due to its limited range of intellectual abilities.<ref name="mcginn-1989"/> He cites [[Jerry Fodor]]'s concept of the [[modularity of mind]] in support of cognitive closure.<ref name="mcginn-1989"/>

While in McGinn's strong form, new mysterianism states that the relationship between consciousness and the material world can ''never'' be understood by the human mind, there are also weaker forms that argue it cannot be understood within existing paradigms but that advances in science or philosophy may open the way to other solutions (see above).<ref name="jw-iep"/> The ideas of [[Thomas Nagel]] and [[Joseph Levine (philosopher)|Joseph Levine]] fall into the second category.<ref name="jw-iep"/> Steven Pinker has also endorsed this weaker version of the view, summarising it as follows:<ref name="pinker-time"/>

<blockquote>And then there is the theory put forward by philosopher Colin McGinn that our vertigo when pondering the Hard Problem is itself a quirk of our brains. The brain is a product of evolution, and just as animal brains have their limitations, we have ours. Our brains can't hold a hundred numbers in memory, can't visualize seven-dimensional space and perhaps can't intuitively grasp why neural information processing observed from the outside should give rise to subjective experience on the inside. This is where I place my bet, though I admit that the theory could be demolished when an unborn genius—a Darwin or Einstein of consciousness—comes up with a flabbergasting new idea that suddenly makes it all clear to us.</blockquote>

=== Commentary on the problem's explanatory targets ===
Philosopher Raamy Majeed argued in 2016 that the hard problem is associated with two "explanatory targets":<ref name="majeed2016">{{cite journal|last=Majeed|first=Raamy|date=September 2016|title=The hard problem & its explanatory targets|journal=[[Ratio (journal)|Ratio]]|volume=29|issue=3|pages=298–311|doi=10.1111/rati.12103}}</ref>
#[PQ] Physical processing gives rise to experiences with a phenomenal character.
#[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 [[Feeling|felt]] states), whereas the second concerns the very nature of the phenomenal itself (i.e., what does the felt state [[What Is it Like to Be a Bat?|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).<ref>Fasching, W. Prakāśa. "A few reflections on the Advaitic understanding of consciousness as presence and its relevance for philosophy of mind." ''Phenomenology and the Cognitive Sciences'' (2020). https://doi.org/10.1007/s11097-020-09690-2</ref></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.<ref name="pinker-time"/><ref name="dennett-edge">{{cite web|last1=Dennett|first1=Daniel|title=The Hard Problem|url=https://www.edge.org/response-detail/25289|website=Edge.org|access-date=11 April 2019|date=2014}}</ref>{{Better source needed|date=May 2022|reason=These are not surveys.}}

===Neural correlates of consciousness===
{{further|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.<ref name="KochEtAl">{{cite journal|last1=Koch|first1=Christof|last2=Massimini|first2=Marcello|last3=Boly|first3=Melanie|last4=Tononi|first4=Giulio|title=Neural correlates of consciousness: Progress and problems|journal=Nature Reviews Neuroscience|date=April 2016|volume=17|issue=5|pages=307–321|doi=10.1038/nrn.2016.22|pmid=27094080|s2cid=5395332|url=https://www.researchgate.net/publication/301567963|access-date=14 April 2018}}</ref> 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".<ref name="chalmers-ncc">{{cite encyclopedia|last=Chalmers|first=David|editor1-last=Hameroff|editor1-first=Stuart|editor1-link=Stuart Hameroff|editor2-last=Kaszniak|editor2-first=Alfred|editor3-first=Alwyn|editor3-last=Scott|encyclopedia=Toward a Science of Consciousness II|title=On the Search for the Neural Correlate of Consciousness|year=1998|publisher=MIT Press|location=Cambridge, MA|isbn=9780262082624|url=http://consc.net/papers/ncc.pdf|access-date=17 April 2018}}</ref> 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.<ref name="chalmers-ncc"/></blockquote>

The neuroscientist and Nobel laureate [[Eric Kandel]] wrote that locating the NCCs would not solve the hard problem, but rather one of the so-called easy problems to which the hard problem is contrasted.<ref name="Kandel">{{cite book|author=Kandel Eric R.|year=2007|title=In search of memory: The emergence of a new science of mind|publisher=W. W. Norton & Company|isbn=978-0393329377|url=https://books.google.com/books?id=PFnRwWXzypgC|pages=380–382}}</ref> 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.<ref name="Kandel"/> However, neuroscientist [[Anil Seth]] argued that emphasis on the so-called hard problem is a distraction from what he calls the "real problem": understanding the neurobiology underlying consciousness, namely the neural correlates of various conscious processes.<ref name="seth-aeon">{{cite web|last1=Seth|first1=Anil|author-link=Anil Seth| title=The real problem|url=https://aeon.co/essays/the-hard-problem-of-consciousness-is-a-distraction-from-the-real-one|website=Aeon|access-date=22 April 2018|date=November 2016}}</ref> This more modest goal is the focus of most scientists working on consciousness.<ref name="Kandel"/> Psychologist [[Susan Blackmore]] believes, by contrast, that the search for the neural correlates of consciousness is futile and itself predicated on an erroneous belief in the hard problem of consciousness.<ref name="blackmore">{{cite web|last1=Blackmore|first1=Susan|title=The Neural Correlates of Consciousness|url=https://www.edge.org/response-detail/25457|website=Edge.org|access-date=22 April 2018|date=2014}}</ref>

===Computational cognition===
{{further|Computational theory of mind}}

A [[Functionalism (philosophy of mind)|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 cognition|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===
{{further|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.<ref name="comp-iit">{{cite journal|last1=Krohn|first1=Stephan|last2=Ostwald|first2=Dirk|title=Computing integrated information|journal=Neuroscience of Consciousness|date=2017|volume=2017|issue=1|pages=nix017|doi=10.1093/nc/nix017|pmid=30042849|pmc=6007153}}</ref><ref name="critique-iit">{{cite journal|last1=Cerullo|first1=Michael A.|editor1-last=Kording|editor1-first=Konrad P.|title=The Problem with Phi: A Critique of Integrated Information Theory|journal=PLOS Computational Biology|date=September 2015|volume=11|issue=9|pages=e1004286|pmid=26378789|pmc=4574706|doi=10.1371/journal.pcbi.1004286|bibcode=2015PLSCB..11E4286C|doi-access=free}}</ref> The theory proposes an [[Identity (philosophy)|identity]] between consciousness and integrated information, with the latter item (denoted as Φ) defined mathematically and thus in principle measurable.<ref name="critique-iit"/><ref name="morch-iit">{{cite web|last1=Mørch|first1=Hedda Hassel|title=The Integrated Information Theory of Consciousness|url=https://philosophynow.org/issues/121/The_Integrated_Information_Theory_of_Consciousness|website=Philosophy Now|access-date=22 April 2018|date=2017}}</ref> The hard problem of consciousness, write Tononi and Koch, may indeed be intractable when working from matter to consciousness.<ref name="tononi+koch"/> However, because IIT inverts this relationship and works from phenomenological axioms to matter, they say it could be able to solve the hard problem.<ref name="tononi+koch"/> In this vein, proponents have said the theory goes beyond identifying human neural correlates and can be extrapolated to all physical systems. Tononi wrote (along with two colleagues):

<blockquote>While identifying the "neural correlates of consciousness" is undoubtedly important, it is hard to see how it could ever lead to a satisfactory explanation of what consciousness is and how it comes about. As will be illustrated below, IIT offers a way to analyse systems of mechanisms to determine if they are properly structured to give rise to consciousness, how much of it, and of which kind.<ref name="iit-3.0">{{cite journal|last1=Oizumi|first1=Masafumi|last2=Albantakis|first2=Larissa|last3=Tononi|first3=Giulio|title=From the Phenomenology to the Mechanisms of Consciousness: Integrated Information Theory 3.0|journal=PLOS Computational Biology|date=May 2014|volume=10|issue=5|pages=e1003588|doi=10.1371/journal.pcbi.1003588|pmid=24811198|pmc=4014402|bibcode=2014PLSCB..10E3588O|doi-access=free}}</ref></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.<ref name="critique-iit"/> "Even if IIT is correct," he argues, "it does not explain why integrated information generates (or is) consciousness."<ref name="critique-iit"/> Chalmers agrees that IIT, if correct, would solve the "Pretty Hard Problem" rather than the hard problem.<ref name="mindt-2017">{{cite journal|last1=Mindt|first1=Garrett|title=The Problem with the 'Information' in Integrated Information Theory|journal=Journal of Consciousness Studies|date=2017|volume=24|issue=7–8|pages=130–154|url=http://newdualism.org/papers/G.Mindt/Mindt-JCS2017.pdf|access-date=22 February 2022}}</ref>

===Global workspace theory===
{{further|Global workspace theory}}

[[Global workspace theory]] (GWT) is a [[cognitive architecture]] and theory of consciousness proposed by the cognitive psychologist [[Bernard Baars]] in 1988.<ref name="baars-2005">{{cite book|doi=10.1016/S0079-6123(05)50004-9|citeseerx=10.1.1.456.2829|chapter=Global workspace theory of consciousness: Toward a cognitive neuroscience of human experience|title=The Boundaries of Consciousness: Neurobiology and Neuropathology|series=Progress in Brain Research|year=2005|last1=Baars|first1=Bernard J.|volume=150|pages=45–53|pmid=16186014|isbn=9780444518514}}</ref> Baars explains the theory with the metaphor of a theatre, with conscious processes represented by an illuminated stage.<ref name="baars-2005"/> This theatre integrates inputs from a variety of unconscious and otherwise autonomous networks in the brain and then broadcasts them to unconscious networks (represented in the metaphor by a broad, unlit "audience").<ref name="baars-2005"/> The theory has since been expanded upon by other scientists including cognitive neuroscientist [[Stanislas Dehaene]].<ref name="dehaene-naccache">{{cite journal|last1=Dehaene|first1=Stanislas|last2=Naccache|first2=Lionel|title=Towards a cognitive neuroscience of consciousness: basic evidence and a workspace framework|journal=Cognition|date=2001|volume=79|issue=1–2|pages=1–37|url=http://zoo.cs.yale.edu/classes/cs671/12f/12f-papers/dehaene-consciousness.pdf|access-date=5 April 2019|doi=10.1016/S0010-0277(00)00123-2|pmid=11164022|s2cid=1762431}}</ref>

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.<ref name="Chalmers"/> In particular, he said GWT provided a promising account of how information in the brain could become globally accessible, but argued that "now the question arises in a different form: why should global accessibility give rise to conscious experience? As always, this bridging question is unanswered."<ref name="Chalmers"/> J. W. Dalton similarly criticised GWT on the grounds that it provides, at best, an account of the cognitive ''function'' of consciousness, and fails to explain its experiential aspect.<ref name="dalton-1997">{{cite journal|last1=Dalton|first1=J. W.|title=The unfinished theatre|journal=Journal of Consciousness Studies|date=1997|volume=4|issue=4|pages=316–318}}</ref> 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."<ref name="elitzur-1997">{{cite journal|last1=Elitzur|first1=Avshalom C.|title=Why don't we know what Mary knows? Baars' reversing the problem of qualia|journal=Journal of Consciousness Studies|date=1997|volume=4|issue=4|pages=319–324}}</ref>

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.<ref name="dc-gw"/> Dehaene, in his 2014 book ''[[Consciousness and the Brain]]'', rejected the concept of qualia and argued that Chalmers' "easy problems" of consciousness are actually the hard problems.<ref name="Dehaene"/> He further stated that the "hard problem" is based only upon ill-defined intuitions that are continually shifting as understanding evolves:<ref name=Dehaene/>

<blockquote>Once our intuitions are educated by cognitive neuroscience and computer simulations, Chalmers' hard problem will evaporate. The hypothetical concept of qualia, pure mental experience, detached from any information-processing role, will be viewed as a peculiar idea of the prescientific era, much like [[vitalism]]... [Just as science dispatched vitalism] the science of consciousness will keep eating away at the hard problem of consciousness until it vanishes.</blockquote>

==Meta-problem==
In 2018, Chalmers highlighted what he calls the "'''meta-problem of consciousness'''", another problem related to the hard problem of consciousness:<ref name="meta-problem"/>

<blockquote>The meta-problem of consciousness is (to a first approximation) the problem of explaining why we think that there is a [hard] problem of consciousness.</blockquote>

In his "second approximation", he says it is the problem of explaining the behaviour of "[[Consciousness#Types of consciousness|phenomenal]] reports", and the behaviour of expressing a belief that there is a hard problem of consciousness.<ref name="meta-problem"/>

Explaining its significance, he says:<ref name="meta-problem"/>
<blockquote>Although the meta-problem is strictly speaking an easy problem, it is deeply connected to the hard problem. We can reasonably hope that a solution to the meta-problem will shed significant light on the hard problem. A particularly strong line holds that a solution to the meta-problem will solve or dissolve the hard problem. A weaker line holds that it will not remove the hard problem, but it will constrain the form of a solution.</blockquote>In other words, the 'strong line' holds that the solution to the meta-problem would provide an explanation of our beliefs about consciousness that is independent of consciousness. That would debunk our beliefs about consciousness, in the same way that explaining beliefs about god in evolutionary terms may provide arguments against theism itself.<ref>{{Citation|title=The Meta-Problem of Consciousness {{!}} Professor David Chalmers {{!}} Talks at Google| date=2 April 2019 |url=https://www.youtube.com/watch?v=OsYUWtLQBS0|language=en|access-date=2022-01-11}}</ref>

==In popular culture==
[[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".<ref>{{cite book|last1=Stoppard|first1=Tom|title=Programme notes|date=28 January 2015|publisher=[[Royal National Theatre]]|location=London|chapter=First Person}}</ref>

==See also==
{{Portal|Philosophy}}
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{cols|colwidth=20em}}
* [[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]]
{{colend}}
<!-- please keep entries in alphabetical order -->

==Notes==
{{Reflist|group=note}}

==References==
{{Reflist|30em|refs=
<ref name=Aranyosi>
Leibniz, ''Monadology,'' 17, as quoted by {{cite web|url=http://www.personal.ceu.hu/students/03/Istvan_Aranyosi/Chapter%20IV.pdf|last=Aranyosi|first=Istvan|title=Chalmers's zombie arguments|year=2004|edition=draft|publisher=Central European University Personal Pages}}
</ref>

<ref name=Chalmers>{{cite journal|url=http://consc.net/papers/facing.pdf|title=Facing up to the problem of consciousness|last=Chalmers|first=David|author-link=David Chalmers|journal=[[Journal of Consciousness Studies]]|volume= 2|issue=3|year=1995|pages=200–219}}
</ref>

<ref name=Cooney>
See Cooney's foreword to the reprint of Chalmers' paper: {{cite book|title=The place of mind|chapter=Chapter 27: Facing up to the problem of consciousness|editor=Brian Cooney|publisher=Cengage Learning|isbn=978-0534528256|year=1999|pages=382 ''ff''}}
</ref>

<ref name=Dehaene>
{{cite book|title=Consciousness and the brain: deciphering how the brain codes our thoughts|last=Dehaene|first=Stanislas|author-link=Stanislas Dehaene|isbn=978-0670025435|publisher=Viking Adult|year=2014|pages=[https://books.google.com/books?id=CWw2AAAAQBAJ&pg=PT197 259–266]}}
</ref>

<ref name=Dennett>
{{cite book|chapter-url=https://books.google.com/books?id=sicVcPjfPxUC&pg=RA3-PA59|pages=310 ''ff''|chapter=The tuned deck|title=Intuition pumps and other tools for thinking|year=2013|publisher=W. W. Norton & Company|isbn=978-0393240689|last=Dennett|first=Daniel C.|author-link=Daniel C. Dennett}} and also "Commentary on Chalmers": {{cite journal|last=Dennett|first=Daniel C.|author-link=Daniel C. Dennett|title=Facing backwards on the problem of consciousness|journal=[[Journal of Consciousness Studies]]|volume=3|issue=1|year=1996|pages=4–6|url=http://ase.tufts.edu/cogstud/dennett/papers/chalmers.htm}}
</ref>

<ref name=Dennett2>
{{cite book|last=Dennett|first=Daniel C.|author-link=Daniel C. Dennett|year=1991|title=Consciousness explained|isbn=978-0316180658|location=Boston|publisher=[[Little, Brown and Company]]|url-access=registration|url=https://archive.org/details/consciousnessexp00denn}}
</ref>

<ref name=Dennett3>
{{cite journal|last=Dennett|first=Daniel C.|author-link=Daniel C. Dennett|year=2003|title=Explaining the 'magic' of consciousness|journal=Journal of Cultural and Evolutionary Psychology|volume=1|issue=1|pages=7–19|doi=10.1556/jcep.1.2003.1.2|s2cid=144560246}}</ref>

<ref name=Harnad>
{{cite journal|last=Harnad|first=Stevan|author-link=Stevan Harnad|year=1995|url=http://cogprints.org/1601/6/harnad95.zombies.html|title=Why and how we are not zombies|journal=[[Journal of Consciousness Studies]]|volume=1|pages=164–167}} See also {{cite journal|last=Harnad|first=Stevan|author-link=Stevan Harnad|date=April 2000|title=How/why the mind–body problem is hard|journal=[[Journal of Consciousness Studies]]|volume=7|issue=4|pages=54–61|url=http://cogprints.org/1617/1/harnad00.mind.humphrey.html}}
</ref>

<ref name="Consciousness as engineering">
{{cite book|last=Graziano|first=Michael|year=2013|title=Consciousness and the social brain|location=Oxford; New York|publisher=[[Oxford University Press]]|isbn=978-0190263195}}
</ref>

<ref name="Consciousness as engineering2">
{{cite web|url=https://aeon.co/essays/can-we-make-consciousness-into-an-engineering-problem|title=Build-a-brain|author=Michael Graziano|date=10 July 2015|website=aeon.co|access-date=19 April 2018}}
</ref>
}}

==External links==
* {{Cite IEP|url-id=hard-con|title=The hard problem of consciousness|last=Weisberg|first=Josh}}

{{Philosophy of mind}}

{{Consciousness}}

[[Category:Arguments in philosophy of mind]]
[[Category:Consciousness]]
[[Category:Mind–body problem]]
[[Category:Open problems]]
[[Category:Philosophical problems]]