Editing Consciousness (section)

==Problem of definition==
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| quote  = About forty meanings attributed to the term ''consciousness'' can be identified and categorized based on ''functions'' and ''experiences''. The prospects for reaching any single, agreed-upon, theory-independent definition of consciousness appear remote.<ref>{{cite journal|last1 = Vimal|first1 = R. L. P.|last2 = Sansthana|first2 = D. A.|year = 2010|title = On the Quest of Defining Consciousness|url = http://sites.google.com/site/rlpvimal/Home/2010-Vimal-DefineC-LVCR-3-2.pdf|journal = Mind and Matter|volume = 8|issue = 1| pages = 93–121}}{{Dead link|date=January 2024}}</ref>
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Scholars are divided <!-- In the late 20th century, philosophers like [[David W. Hamlyn|Hamlyn]], [[Richard Rorty|Rorty]], and [[Kathy Wilkes|Wilkes]] have disagreed with [[Charles H. Kahn|Kahn]], [[W. F. R. Hardie|Hardie]], and [[Deborah Modrak|Modrak]] CLARIFICATION IS NEEDED: WHO THOUGHT WHAT? --> as to whether [[Aristotle]] had a concept of consciousness. He does not use any single word or terminology that is clearly similar to the [[phenomenon]] or [[concept]] defined by John Locke. Victor Caston contends that Aristotle did have a concept more clearly similar to [[perception]].<ref name="caston02">{{cite book|last1=Caston|first1=Victor|title=Mind|date=2002|publisher=Oxford University Press|page=751|url=http://ancphil.lsa.umich.edu/-/downloads/faculty/caston/aristotle-consciousness.pdf|archive-url=https://ghostarchive.org/archive/20221009/http://ancphil.lsa.umich.edu/-/downloads/faculty/caston/aristotle-consciousness.pdf|archive-date=2022-10-09|url-status=live|chapter=Aristotle on Consciousness}}</ref>

Modern dictionary definitions of the word ''consciousness'' evolved over several centuries and reflect a range of seemingly related meanings, with some differences that have been controversial, such as the distinction between ''inward awareness'' and ''perception'' of the physical world, or the distinction between ''conscious'' and ''unconscious'', or the notion of a ''mental entity'' or ''mental activity'' that is not physical.

The common-usage definitions of ''consciousness'' in ''[[Webster's Third New International Dictionary]]'' (1966) are as follows:<!--  EXACTLY AS FOLLOWS:  Do not rewrite the list content or structure! -->
#* ''awareness or perception of an inward psychological or spiritual fact; intuitively perceived knowledge of something in one's inner self''
#* ''inward awareness of an external object, state, or fact''
#* ''concerned awareness;'' INTEREST, CONCERN—''often used with an attributive noun [e.g. class consciousness]''
# ''the state or activity that is characterized by sensation, emotion, volition, or thought; mind in the broadest possible sense; something in nature that is distinguished from the physical''
# ''the totality in psychology of sensations, perceptions, ideas, attitudes, and [[feelings]] of which an individual or a group is aware at any given time or within a particular time span—''compare STREAM OF CONSCIOUSNESS
# ''waking life (as that to which one returns after sleep, trance, fever) wherein all one's mental powers have returned . . .''
# ''the part of mental life or psychic content in psychoanalysis that is immediately available to the ego—''compare PRECONSCIOUS, UNCONSCIOUS

The ''[[Cambridge English Dictionary]]'' defines consciousness as "the state of being awake, thinking, and knowing what is happening around you", as well as "the state of understanding and realizing something".<ref>{{cite dictionary|url=https://dictionary.cambridge.org/dictionary/english/consciousness|entry=consciousness|encyclopedia=Cambridge English Dictionary|publisher=Cambridge University Press|access-date=2018-10-23|archive-date=2021-03-07|archive-url=https://web.archive.org/web/20210307210954/https://dictionary.cambridge.org/dictionary/english/consciousness|url-status=live |title=Consciousness}}</ref>
The ''[[Oxford Living Dictionary]]'' defines consciousness as "[t]he state of being aware of and responsive to one's surroundings", "[a] person's awareness or perception of something", and "[t]he fact of awareness by the mind of itself and the world".<ref>{{cite dictionary|url=https://en.oxforddictionaries.com/definition/consciousness|archive-url=https://web.archive.org/web/20160925102008/https://en.oxforddictionaries.com/definition/consciousness|url-status=dead|archive-date=September 25, 2016|entry=consciousness|dictionary=Oxford Living Dictionary|publisher=Oxford University Press|title=Consciousness - definition of consciousness in English &#124; Oxford Dictionaries}}</ref>

Philosophers have attempted to clarify technical distinctions by using a [[jargon]] of their own. The corresponding entry in the ''[[Routledge Encyclopedia of Philosophy]]'' (1998) reads:
;'''Consciousness''':Philosophers have used the term ''consciousness'' for four main topics: knowledge in general, intentionality, introspection (and the knowledge it specifically generates) and phenomenal experience... Something within one's mind is 'introspectively conscious' just in case one introspects it (or is poised to do so). Introspection is often thought to deliver one's primary knowledge of one's mental life. An experience or other mental entity is 'phenomenally conscious' just in case there is 'something it is like' for one to have it. The clearest examples are: perceptual experience, such as tastings and seeings; bodily-sensational experiences, such as those of pains, tickles and itches; imaginative experiences, such as those of one's own actions or perceptions; and streams of thought, as in the experience of thinking 'in words' or 'in images'. Introspection and phenomenality seem independent, or dissociable, although this is controversial.<ref name=Craig>{{cite encyclopedia|author=Edward Craig|encyclopedia=Routledge Encyclopedia of Philosophy|publisher=Routledge|entry=Consciousness|year=1998|isbn=978-0-415-18707-7|author-link=Edward Craig (philosopher)}}</ref>

===Traditional metaphors for mind===
During the early 19th century, the emerging field of [[geology]] inspired a popular [[metaphor]] that the mind likewise had hidden layers "which recorded the past of the individual".{{r|JJ76|p=3}} By 1875, most psychologists believed that "consciousness was but a small part of mental life",{{r|JJ76|p=3}} and this idea underlies the goal of [[Freudian psychology|Freudian therapy]], to expose the {{em|unconscious layer}} of the mind.

Other metaphors from various sciences inspired other analyses of the mind, for example: [[Johann Friedrich Herbart]] described ideas as being attracted and repulsed like magnets; [[John Stuart Mill]] developed the idea of "mental chemistry" and "mental compounds", and [[Edward B. Titchener]] sought the "structure" of the mind by analyzing its "elements". The abstract idea of ''states of consciousness'' mirrored the concept of [[states of matter]].

In 1892, [[William James]] noted that the "ambiguous word 'content' has been recently invented instead of 'object'" and that the metaphor of mind as a {{em|container}} seemed to minimize the dualistic problem of how "states of consciousness can {{em|know}}" things, or objects;{{r|WJames92|p=465}} by 1899 psychologists were busily studying the "contents of conscious experience by [[introspection]] and [[experiment]]".<ref name=Thomas67 />{{rp|365}} Another popular metaphor was James's doctrine of the [[stream of consciousness (psychology)|stream of consciousness]], with continuity, fringes, and transitions.{{r|WJames92|p=vii}}{{efn|From the introduction by [[Ralph Barton Perry]], 1948.}}

James discussed the difficulties of describing and studying psychological phenomena, recognizing that commonly-used terminology was a necessary and acceptable starting point towards more precise, scientifically justified language. Prime examples were phrases like ''inner experience'' and ''personal consciousness'':
{{blockquote|The first and foremost concrete fact which every one will affirm to belong to his inner experience is the fact that {{em|consciousness of some sort goes on. 'States of mind' succeed each other in him}}. [...] But everyone knows what the terms mean [only] in a rough way; [...] When I say {{em|every 'state' or 'thought' is part of a personal consciousness}}, 'personal consciousness' is one of the terms in question. Its meaning we know so long as no one asks us to define it, but to give an accurate account of it is the most difficult of philosophic tasks. [...] The only states of consciousness that we naturally deal with are found in personal consciousnesses, minds, selves, concrete particular I's and you's.{{r|WJames92|pp=152–153}}}}

===From introspection to awareness and experience===
Prior to the 20th century, philosophers treated the phenomenon of consciousness as the "inner world [of] one's own mind", and [[introspection]] was the mind "attending to" itself,{{efn|From the ''Macmillan Encyclopedia of Philosophy'' (1967): "Locke's use of 'consciousness' was widely adopted in British philosophy. In the late nineteenth century the term 'introspection' began to be used. [[G. F. Stout]]'s definition is typical: "To introspect is to attend to the workings of one's own mind" [... (1899)]".<ref name=Landesman67>{{cite encyclopedia|last1=Landesman|first1=Charles Jr.|editor1-last=Edwards|editor1-first=Paul|encyclopedia=The Encyclopedia of Philosophy|contribution=Consciousness|volume= 2|date=1967|publisher=Macmillan, Inc.|pages=191–195|edition=Reprint 1972}}</ref>{{rp|191–192}}}} an activity seemingly distinct from that of perceiving the 'outer world' and its physical phenomena. In 1892 [[William James]] noted the distinction along with doubts about the inward character of the mind:{{blockquote|'Things' have been doubted, but thoughts and feelings have never been doubted. The outer world, but never the inner world, has been denied. Everyone assumes that we have direct introspective acquaintance with our thinking activity as such, with our consciousness as something inward and contrasted with the outer objects which it knows. Yet I must confess that for my part I cannot feel sure of this conclusion. [...] It seems as if consciousness as an inner activity were rather a ''postulate'' than a sensibly given fact...<ref name=WJames92>{{cite book|last1=James|first1=William|title=Psychology|date=1948|orig-date=1892|publisher=Fine Editions Press, World Publishing Co.|location=Cleveland}}</ref>{{rp|467}}}}
By the 1960s, for many philosophers and psychologists who talked about consciousness, the word no longer meant the 'inner world' but an indefinite, large category called ''[[awareness]]'', as in the following example:<!-- Without an established definition or an obvious thing, event or experience that consciousness must refer to, a number of items are often presented as examples, as in the following claim: -->
{{blockquote|It is difficult for modern Western man to grasp that the Greeks really had no concept of consciousness in that they did not class together phenomena as varied as problem solving, remembering, imagining, perceiving, feeling pain, dreaming, and acting on the grounds that all these are manifestations of being aware or being conscious.<ref name="EPhil-Psyc" >{{cite encyclopedia|last1=Peters|first1=R. S.|last2=Mace|first2=C. A.|editor1-last=Edwards|editor1-first=Paul|encyclopedia=The Encyclopedia of Philosophy|contribution=Psychology|volume= 7|date=1967|publisher=Macmillan, Inc.|pages=1–27|edition=Reprint 1972}}</ref>{{rp|4}}}}

Many philosophers and scientists have been unhappy about the difficulty of producing a definition that does not involve circularity or fuzziness.<ref name=Sutherland/> In The ''Macmillan Dictionary of Psychology'' (1989 edition), [[Stuart Sutherland]] emphasized external awareness, and expressed a skeptical attitude more than a definition:

{{blockquote|'''Consciousness'''—The having of perceptions, thoughts, and [[feelings]]; awareness. The term is impossible to define except in terms that are unintelligible without a grasp of what consciousness means. Many fall into the trap of equating consciousness with [[self-consciousness]]—to be conscious it is only necessary to be aware of the external world. Consciousness is a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it has evolved. Nothing worth reading has been written on it.<ref name=Sutherland>{{cite book|author=Stuart Sutherland|title=Macmillan Dictionary of Psychology|publisher=Macmillan|chapter=Consciousness|year=1989|isbn=978-0-333-38829-7|author-link=Stuart Sutherland}}</ref>}}
Using 'awareness', however, as a definition or synonym of consciousness is not a simple matter:
{{blockquote|text=If awareness of the environment . . . is the criterion of consciousness, then even the protozoans are conscious. If awareness of awareness is required, then it is doubtful whether the great apes and human infants are conscious.<ref name=Thomas67>{{cite encyclopedia|last= Thomas|first= Garth J.|encyclopedia= Encyclopædia Britannica|date=1967|volume=6|pages=366|title= Consciousness}}</ref>}}
In 1974, philosopher [[Thomas Nagel]] used 'consciousness', 'conscious experience', 'subjective experience' and the 'subjective character of experience' as synonyms for something that "occurs at many levels of animal life&nbsp;... [although] it is difficult to say in general what provides evidence of it."<ref name=NagelBat1>{{cite journal | last1 = Nagel | first1 = Thomas | year = 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 |url={{google books |plainurl=y |id=fBGPBRX3JsQC|page=165}}}}</ref> Nagel's terminology also included what has been described as "the standard 'what it's like' locution"<ref name=Levine10>Levine, Joseph (2010). Review of Uriah Kriegel, Subjective Consciousness: A Self-Representational Theory. ''Notre Dame Philosophical Reviews'' 2010 (3).</ref> in reference to the impenetrable [[subjectivity]] of any organism's [[experience]] which Nagel referred to as "inner life" without implying any kind of introspection. On Nagel's approach, [[Peter Hacker]] commented:{{r|Hacker2002|p=158}} "Consciousness, thus conceived, is extended to the whole domain of 'experience'—of 'Life' {{em|subjectively understood}}." He regarded this as a "novel analysis of consciousness"{{r|Hacker2012|p=14}} and has been particularly critical of Nagel's terminology and its philosophical consequences.{{r|Hacker2012}} In 2002 he attacked Nagel's 'what it's like' phrase as "malconstructed" and meaningless English—it sounds as if it asks for an analogy, but does not—and he called Nagel's approach logically "misconceived" as a definition of consciousness.<ref name=Hacker2002>{{cite journal |author-link= Peter Hacker |last= Hacker |first= P.M.S. |url=http://www.phps.at/texte/HackerP1.pdf |title= Is there anything it is like to be a bat? |journal= Philosophy |volume= 77 |date= 2002 |issue= 2 |pages= 157–174 |doi=10.1017/s0031819102000220}}</ref> In 2012 Hacker went further and asserted that Nagel had "laid the groundwork for&nbsp;... forty years of fresh confusion about consciousness" and that "the contemporary philosophical conception of consciousness that is embraced by the 'consciousness studies community' is incoherent".{{r|Hacker2012|p=13-15}}

===Influence on research===
Many philosophers have argued that consciousness is a unitary concept that is understood by the majority of people despite the difficulty philosophers have had defining it.<ref name="Antony2001">{{cite journal|author=Michael V. Antony|year=2001|title=Is ''consciousness'' ambiguous?|journal=Journal of Consciousness Studies|volume=8|pages=19–44}}</ref> The term 'subjective experience', following Nagel, is amibiguous, as philosophers seem to differ from non-philosophers in their intuitions about its meaning.<ref>{{cite journal |author=Justin Sytsma |author2=Edouard Machery |title=Two conceptions of subjective experience |journal=Philosophical Studies |year=2010 |volume=151 |issue=2 |pages=299–327 |doi=10.1007/s11098-009-9439-x|s2cid=2444730 |url=http://philsci-archive.pitt.edu/archive/00004888/01/Two_Conceptions_of_Subjective_Experience.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://philsci-archive.pitt.edu/archive/00004888/01/Two_Conceptions_of_Subjective_Experience.pdf |archive-date=2022-10-09 |url-status=live}}</ref> [[Max Velmans]] proposed that the "everyday understanding of consciousness" uncontroversially "refers to experience itself rather than any particular thing that we observe or experience" and he added that consciousness "is [therefore] exemplified by {{em|all}} the things that we observe or experience",{{r|Velmans2009|p=4}}<!--COMMENT: Velman's statement is a confusion of logical categories, an error of logical typing. Empirical science has discovered much about the processes of perception because there are 'objects' perceived by 'organs' of perception; but "experience itself" is an idea, a concept, an abstraction. Since 'experience' is not some 'thing' experienced, therefore (by definition) it cannot be empirically analyzed, reduced or compared. The 'things that we actually observe or experience' are examples of 'things' and 'kinds of things'; it's incorrect to call them 'examples of experience'! --> whether thoughts, feelings, or perceptions. [[Max Velmans|Velmans]] noted however, as of 2009, that there was a deep level of "confusion and internal division"<ref name=Velmans2009>{{cite journal|author=Max Velmans|title=How to define consciousness—and how not to define consciousness|journal=Journal of Consciousness Studies|year=2009|volume=16|pages=139–156|author-link=Max Velmans}}</ref> among experts about the phenomenon of consciousness, because researchers lacked "a sufficiently well-specified use of the term...to agree that they are investigating the same thing".{{r|Velmans2009|p=3}} He argued additionally that "pre-existing theoretical commitments" to competing explanations of consciousness might be a source of bias.

Within the "modern consciousness studies" community the technical phrase 'phenomenal consciousness' is a common synonym for all forms of awareness, or simply '[[experience]]',{{r|Velmans2009|p=4|quote=In common usage, the term "consciousness" is often synonymous with "awareness", "conscious awareness", and "experience".}} without differentiating between inner and outer, or between higher and lower types. With advances in brain research, "the presence or absence of ''experienced phenomena''"{{r|Velmans2009|p=3}} of any kind underlies the work of those [[neuroscientist]]s who seek "to analyze the precise relation of [[Phenomenology (psychology)|conscious phenomenology]] to its associated information processing" in the brain.{{r|Velmans2009|p=10}} This [[neuroscience|neuroscientific]] goal is to find the "neural correlates of consciousness" (NCC). One criticism of this goal is that it begins with a theoretical commitment to the neurological origin of all "experienced phenomena" whether inner or outer.{{efn|"Investigating "how experience ensues from the brain", rather than exploring a factual claim, betrays a philosophical commitment".<ref name="Gomez2019">{{cite journal|last1=Gomez-Marin|first1=Alex|last2=Arnau|first2=Juan|title=The False Problem of Consciousness|journal=Behavior of Organisms Laboratory|date=2019|url=http://philsci-archive.pitt.edu/15699/1/MS_GomezMarin_Arnau.pdf}}</ref>}} Also, the fact that the easiest 'content of consciousness' to be so analyzed is "the experienced three-dimensional world (the phenomenal world) beyond the body surface"{{r|Velmans2009|p=4}} invites another criticism, that most consciousness research since the 1990s, perhaps because of bias, has focused on processes of [[perception|external perception]].<ref name="Frith2016">{{cite book|editor-last1=Engel|editor-first1=Andreas K.|last1=Frith|first1=Chris|last2=Metzinger|first2=Thomas|title= The Pragmatic Turn: Toward Action-Oriented Views in Cognitive Science|url=https://www.researchgate.net/publication/304657860|chapter=What's the Use of Consciousness? How the Stab of Conscience Made Us Really Conscious|pages=193–214|isbn= 9780262034326|doi= 10.7551/mitpress/9780262034326.003.0012|date=March 2016|author-link1=Chris Frith|author-link2=Thomas Metzinger}}</ref>

From a [[history of psychology]] perspective, [[Julian Jaynes]] rejected popular but "superficial views of consciousness"{{r|JJ90|p=447}} especially those which equate it with "that vaguest of terms, [[experience]]".<ref name=JJ76>{{cite book|last=Jaynes|first=Julian|date=1976|isbn=0-395-20729-0|author-link=Julian Jaynes|publisher=Houghton Mifflin|title=The Origin of Consciousness in the Breakdown of the Bicameral Mind|url=https://archive.org/details/originofconsciou0000unse|url-access=registration}}</ref>{{rp|8}} In 1976 he insisted that if not for [[introspection]], which for decades had been ignored or taken for granted rather than explained, there could be no "conception of what consciousness is"{{r|JJ76|p=18}} and in 1990, he reaffirmed the traditional idea of the phenomenon called 'consciousness', writing that "its [[denotation|denotative definition]] is, as it was for René Descartes, John Locke, and [[David Hume]], what is introspectable".{{r|JJ90|p=450}} Jaynes saw consciousness as an important but small part of human mentality, and he asserted: "there can be no progress in the science of consciousness until&nbsp;... what is introspectable [is] sharply distinguished"{{r|JJ90|p=447}} from the {{em|unconscious}} processes of [[cognition]] such as [[perception]], reactive [[awareness]] and [[attention]], and automatic forms of [[learning]], [[problem-solving]], and [[decision-making]].{{r|JJ76|p=21-47}}

The [[cognitive science]] point of view—with an inter-disciplinary perspective involving fields such as [[psychology]], [[linguistics]] and [[anthropology]]<ref>{{Cite book|url=https://books.google.com/books?id=PKCHAgAAQBAJ&q=Consciousness+in+anthropology&pg=PP1|title=Questions of Consciousness|last1=Cohen|first1=A. P.|last2=Rapport|first2=N.|publisher=Routledge|year=1995|isbn=978-1-134-80469-6|location=London}}</ref>—requires no agreed definition of "consciousness" but studies the interaction of many processes besides perception. For some researchers, consciousness is linked to some kind of "selfhood", for example to certain pragmatic issues such as the feeling of agency and the effects of regret<ref name="Frith2016" /> and action on experience of one's own body or social identity.<ref name="Seth2016">{{cite book|editor-last1=Engel|editor-first1=Andreas K.|last1=Seth|first1=Anil|title= The Pragmatic Turn: Toward Action-Oriented Views in Cognitive Science |chapter=Action-Oriented Understanding of Consciousness and the Structure of Experience|pages=261–282|isbn=978-0-262-03432-6|doi= 10.7551/mitpress/9780262034326.003.0012|date=March 2016|author-link1=Anil Seth}}</ref> Similarly [[Daniel Kahneman]], who focused on systematic errors in perception, memory and decision-making, has differentiated between two kinds of mental processes, or cognitive "systems":<ref name="Kahneman2011">{{cite book|first=Daniel|last=Kahneman|title=Thinking, Fast and Slow|url=https://books.google.com/books?id=ZuKTvERuPG8C|year=2011|publisher=Macmillan|isbn=978-1-429-96935-2}}</ref> the "fast" activities that are primary, automatic and "cannot be turned off",{{r|Kahneman2011|p=22}} and the "slow", deliberate, effortful activities of a secondary system "often associated with the subjective experience of agency, choice, and concentration".{{r|Kahneman2011|p=13}} Kahneman's two systems have been described as "roughly corresponding to unconscious and conscious processes".<ref name="Kuijsten2016">{{cite book|last=Kuijsten|first=Marcel|year=2016|editor-last=Kuijsten|editor-first=Marcel|chapter=Introduction|title=Gods, Voices, and the Bicameral Mind: The Theories of Julian Jaynes|pages=1–15|publisher=Julian Jaynes Society|isbn=978-0-979-07443-1|location=Henderson, NV}}</ref>{{rp|8}} The two systems can interact, for example in sharing the control of attention.{{r|Kahneman2011|p=22}} While System 1 can be impulsive, "System 2 is in charge of self-control",{{r|Kahneman2011|p=26}} and "When we think of ourselves, we identify with System 2, the conscious, reasoning self that has beliefs, makes choices, and decides what to think about and what to do".{{r|Kahneman2011|p=21}}

<!-- Others, though, have argued that the level of disagreement about the meaning of the word indicates that it either means different things to different people (for instance, the [[Objectivity (philosophy)|objective]] versus [[Subjectivism|subjective]] aspects of consciousness), that it encompasses a variety of distinct meanings with no simple element in common,<ref name=Velmans2009>{{cite journal|first=Max|last=Velmans|title=How to define consciousness—and how not to define consciousness|journal=Journal of Consciousness Studies|year=2009|volume=16|pages=139–156|author-link=Max Velmans}}</ref> -->Some have argued that we should eliminate the concept from our understanding of the mind, a position known as consciousness semanticism.<ref>{{cite book|last=Anthis|first=Jacy|title=Biologically Inspired Cognitive Architectures 2021|chapter=Consciousness Semanticism: A Precise Eliminativist Theory of Consciousness|series=Studies in Computational Intelligence|year=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|archive-date=7 August 2022|archive-url=https://web.archive.org/web/20220807144036/https://link.springer.com/chapter/10.1007/978-3-030-96993-6_3|url-status=live}}</ref>
<!-- Al Byrd, the author of Superhuman Creators, defines consciousness, for animals, humans and artificial agents, as the effect of integrating and filtering many different types of affordance awareness; that is, awareness of the action possibilities in an environment. According to this definition, all agents that can perceive and act on affordances are conscious to some extent. -->

In [[medicine]], a "level of consciousness" terminology is used to describe a patient's [[arousal]] and responsiveness, which can be seen as a continuum of states ranging from full alertness and [[Understanding|comprehension]], through disorientation, [[delirium]], loss of meaningful communication, and finally loss of movement in response to painful [[Stimulus (physiology)|stimuli]].<ref>{{cite book|first=Güven|last=Güzeldere|title=The Nature of Consciousness: Philosophical Debates|year=1997|editor-first=Ned|editor-last=Block|editor2-first=Owen|editor2-last=Flanagan|editor3-first=Güven|editor3-last=Güzeldere|pages=1–67|location=Cambridge, MA|publisher=MIT Press}}</ref> Issues of practical concern include how the level of consciousness can be assessed in severely ill, comatose, or anesthetized people, and how to treat conditions in which consciousness is impaired or disrupted.<ref>{{cite journal|title=Late recovery from the minimally conscious state: ethical and policy implications|first1=J. J.|last1=Fins|first2=N. D.|last2=Schiff|first3=K. M.|last3=Foley|journal=Neurology|year=2007|volume=68|pages=304–307|pmid=17242341|doi=10.1212/01.wnl.0000252376.43779.96|issue=4|s2cid=32561349}}</ref> The degree or level of consciousness is measured by standardized behavior observation scales such as the [[Glasgow Coma Scale]].