Brain in a vat

{{Short description|Philosophical thought experiment}} {{Redirect|Brain in a jar|the biology of a brain in a vat|Isolated brain}} {{Use dmy dates|date=September 2015}} thumb|right|280px|A brain in a vat that believes it is walking

In philosophy, the '''brain in a vat''' ('''BIV''') is a scenario used in a variety of thought experiments intended to draw out certain features of human conceptions of knowledge, reality, truth, mind, consciousness, and meaning. Gilbert Harman conceived the scenario,<ref>Harman, Gilbert (1973): ''Thought'', Princeton/NJ, p.5.</ref> which Hilary Putnam turned into a modernized version of René Descartes's evil demon thought experiment. Following many science fiction stories, the scenario involves a mad scientist who removes a person's brain from their body, suspend it in a vat of life-sustaining liquid, and connect its neurons by wires to a supercomputer that would provide it with electrical impulses identical to those a brain normally receives.<ref name="putnam">{{cite book|last=Putnam|first=Hilary|author-link=Hilary Putnam|chapter=Brains in a Vat|chapter-url=https://philosophy.as.uky.edu/sites/default/files/Brains%20in%20a%20Vat%20-%20Hilary%20Putnam.pdf|title=Reason, Truth And History| date=1981| publisher=University of Cambridge| place=Cambridge| archive-url=https://web.archive.org/web/20211006131612/https://philosophy.as.uky.edu/sites/default/files/Brains%20in%20a%20Vat%20-%20Hilary%20Putnam.pdf|archive-date=6 October 2021|access-date=21 April 2015}}</ref> According to such stories, the computer would then be simulating reality (including appropriate responses to the brain's own output) and the "disembodied" brain would continue to have perfectly normal conscious experiences, like those of a person with an embodied brain, without these being related to objects or events in the real world. According to Putnam, the thought of "being a brain-in-a-vat" is either false or meaningless.

Considered a cornerstone of semantic externalism, the argument produced significant literature,<ref>{{Cite web|url=https://plato.stanford.edu/Archives/spr2009/entries/brain-vat/|title=Brains in a Vat|first=Tony|last=Brueckner|date=29 October 2004| access-date=7 March 2025|website=Stanford Encyclopedia of Philosophy}}</ref> and works such as ''The Matrix'' franchise are considered inspired by Putnam's argument.<ref>{{Citation |last=Chalmers |first=David J |title=The Matrix As Metaphysics |date=2004-09-01 |url=http://dx.doi.org/10.1093/oso/9780195181067.003.0009 |work=Philosophers Explore The Matrix |pages=132–176 |access-date=2023-11-20 |publisher=Oxford University PressNew York, NY |doi=10.1093/oso/9780195181067.003.0009 |isbn=978-0-19-518106-7|url-access=subscription }}</ref>

== Intuitive version == Putnam's argument is based on the causal theory of reference, where a word describing a spatio-temporal object is meaningful if and only if it possesses an information-carrying causal relation to whatever it denotes. Next, an "envatted" brain is one whose entire world is composed of (say) electric manipulations performed by a computer simulation to which it is connected. With this much in place, consider the sentence "I am a brain in a vat" (BIV). In case you are not a brain in a vat, the sentence is false by definition. In case you are a brain in a vat, the terms "brain" and "vat" fail to denote actual brains and actual vats with whom you had an information-carrying causal interaction since, again by definition, the only interaction available is with the computer simulation, which is not information carrying. By the causal theory of reference, such references do not carry referential meaning. Thus, the sentence "I am a brain in a vat" is either false or meaningless.<ref name="putnam"/>

== Uses == The simplest use of brain-in-a-vat scenarios is as an argument for philosophical skepticism<ref>{{cite web |last1=Klein |first1=Peter |author-link=Peter D. Klein |title=Skepticism |website=Stanford Encyclopedia of Philosophy |url=http://plato.stanford.edu/entries/skepticism/ |date=2 June 2015 |access-date=7 January 2017}}</ref> and solipsism. A simple version of this runs as follows: since the brain in a vat gives and receives exactly the same impulses as it would if it were in a skull, and since these are its only way of interacting with its environment, then it is not possible to tell, ''from the perspective of that brain'', whether it is in a skull or a vat. Yet in the first case, most of the person's beliefs may be true (if they believe, say, that they are walking down the street, or eating ice-cream); in the latter case, their beliefs are false. Since the argument says if one cannot know whether one is a brain in a vat, then one cannot know whether most of one's beliefs might be completely false. Since, in principle, it is impossible to rule out oneself being a brain in a vat, there cannot be good grounds for believing any of the things one believes; a skeptical argument would contend that one certainly cannot ''know'' them, raising issues with the definition of knowledge. Other philosophers have drawn upon sensation and its relationship to meaning in order to question whether brains in vats are really deceived at all,<ref>{{Cite journal|last=Bouwsma|first=O.K.|date=1949|title=Descartes' Evil Genius|url=http://home.sandiego.edu/~baber/analytic/Bouwsma1949.pdf|journal=The Philosophical Review|volume=58| issue = 2|pages=149–151|doi=10.2307/2181388|jstor=2181388}}</ref> thus raising wider questions concerning perception, metaphysics, and the philosophy of language.

The brain-in-a-vat is a contemporary version of the argument given in Hindu Maya illusion, Zhuangzi's "Zhuangzi dreamed he was a butterfly", and the evil demon in René Descartes' ''Meditations on First Philosophy''.

Recently, many contemporary philosophers believe that virtual reality will seriously affect human autonomy as a form of brain in a vat. But another view is that VR will not destroy our cognitive structure or take away our connection with reality. On the contrary, VR will allow us to have more new propositions, new insights and new perspectives to see the world.<ref>{{Cite journal|last1=Cogburn|first1=Jon|last2=Silcox|first2=Mark|date=2014|title=Against Brain-in-a-Vatism: On the Value of Virtual Reality|url=http://link.springer.com/10.1007/s13347-013-0137-4|journal=Philosophy & Technology|language=en|volume=27|issue=4|pages=561–579|doi=10.1007/s13347-013-0137-4|s2cid=143774123|issn=2210-5433|url-access=subscription}}</ref>

== Philosophical debates == While the disembodied brain (the brain in a vat) can be seen as a helpful thought experiment, there are several philosophical debates surrounding the plausibility of the thought experiment. If these debates conclude that the thought experiment is implausible, a possible consequence would be that we are no closer to knowledge, truth, consciousness, representation, etc. than we were prior to the experiment.

=== Argument from biology === thumb|upright|A human brain in jar One argument against the BIV thought experiment derives from the idea that the BIV is not – and cannot be – biologically similar to that of an embodied brain (that is, a brain found in a person). Since the BIV is ''dis''embodied, it follows that it does not have similar biology to that of an embodied brain. That is, the BIV lacks the connections from the body to the brain, which renders the BIV neither neuroanatomically nor neurophysiologically similar to that of an embodied brain.<ref>{{Cite journal |url=https://philpapers.org/rec/HEYABI |title=A Brain in a Vat Cannot Break Out: Why the Singularity Must be Extended, Embedded, and Embodied |last=Heylighen |first=Francis |author-link=Francis Heylighen |date=2012 |journal=Journal of Consciousness Studies |volume=19 |issue=1–2 |pages=126–142 }}</ref><ref>{{Cite journal|url=https://muse.jhu.edu/article/521450 |title=Brain in a Vat or Body in a World? Brainbound versus Enactive Views of Experience|last1=Thompson |first1=Evan |author-link=Evan Thompson |last2=Cosmelli |first2=Diego |date=Spring 2011 |journal=Philosophical Topics |volume=39 |issue=1 |pages=163–180|doi=10.5840/philtopics201139119|s2cid=170332029|url-access=subscription }}</ref> If this is the case, we cannot say that it is even possible for the BIV to have similar experiences to the embodied brain, since the brains are not equal. However, it could be counter-argued that the hypothetical machine could be made to also replicate those types of inputs.

=== Argument from externalism === A second argument deals directly with the stimuli coming into the brain. This is often referred to as the account from externalism or ultra-externalism.<ref>{{Cite journal|title = Consciousness, Information and External Relations|last = Kirk|first = Robert|date = 1997|journal = Communication and Cognition |volume=30 |issue=3–4}}</ref> In the BIV, the brain receives stimuli from a machine. In an embodied brain, however, the brain receives the stimuli from the sensors found in the body (via touching, tasting, smelling, etc.) which receive their input from the external environment. This argument oftentimes leads to the conclusion that there is a difference between what the BIV is representing and what the embodied brain is representing. This debate has been hashed out, but remains unresolved, by several philosophers including Uriah Kriegel,<ref>{{Cite book|title = Current Controversies in Philosophy of Mind|last = Kriegel|first = Uriah|publisher = Routledge|year = 2014|pages = 180–95}}</ref> Colin McGinn,<ref>{{Cite journal|title = Consciousness and Content|last = McGinn|first = Colin|date = 1988|journal = Proceedings of the British Academy |volume=76|pages = 219–39}}</ref> and Robert D. Rupert,<ref>{{Cite book|chapter = The Sufficiency of Objective Representation|last = Rupert|first = Robert|publisher = Routledge|year = 2014|pages = 180–95|title = Current Controversies in Philosophy of Mind}}</ref> and has ramifications for philosophy of mind discussions on (but not limited to) representation, consciousness, content, cognition, and embodied cognition.<ref>{{Cite book|chapter = When Is Cognition Embodied?|last = Shapiro|first = Lawrence|publisher = Routledge|year = 2014|pages = 73–90|title = Current Controversies in Philosophy of Mind}}</ref>

=== Argument from incoherence === A third argument against BIV comes from a direction of incoherence, which was presented by the philosopher Hilary Putnam. He attempts to demonstrate this through the usage of a transcendental argument, in which he tries to illustrate that the thought experiment's incoherence lies on the basis that it is self-refuting.<ref>{{Cite journal|last1=CHEN|first1=Jiaming|last2=Lin|first2=Zhang|date=2012|title=On the Issues of Transcendental Argument|url=https://www.jstor.org/stable/44259404|journal=Frontiers of Philosophy in China|volume=7|issue=2|pages=255–269|jstor=44259404 |issn=1673-3436}}</ref> This relationship is further defined, through a theory of reference that suggested reference can not be assumed, and words are not automatically intrinsically connected with what it represents. This theory of reference would later become known as semantic externalism. This concept is further illustrated when Putnam establishes a scenario in which a monkey types out Hamlet by chance; however, this does not mean that the monkey is referring to the play, because the monkey has no knowledge of ''Hamlet'' and therefore can not refer back to it.<ref>{{Citation|last=Brueckner|first=Tony|editor-first1=Sanford C |editor-last1=Goldberg |title=Putnam on brains in a vat|url=http://dx.doi.org/10.1017/cbo9781107706965.002|work=The Brain in a Vat|year=2016 |pages=19–26|place=Cambridge|publisher=Cambridge University Press|doi=10.1017/cbo9781107706965.002 |isbn=9781107706965 |access-date=2021-09-23|url-access=subscription}}</ref> He then offers the "Twin Earth" example to demonstrate that two identical individuals, one on the Earth and another on a "twin Earth", may possess the exact same mental state and thoughts, yet refer to two different things.<ref name=":0">{{Cite book|last=Putnam|first=Hilary|title=Reason, Truth, and History|publisher=Cambridge University Press|year=1981|isbn=978-0-52129776-9|location=Cambridge|pages=14, 18–19}}</ref> For instance, when people think of cats, the referent of their thoughts would be the cats that are found on Earth. However, people's twins on twin Earth, though possessing the same thoughts, would instead be referring not to Earth's cats, but to twin Earth's cats. Bearing this in mind, he writes that a "pure" brain in a vat, i.e., one that has never existed outside of the simulation, could not even truthfully say that it was a brain in a vat. This is because the BIV, when it says "brain" and "vat", can only refer to objects within the simulation, not to things outside the simulation it does not have a relationship with. Putnam refers to this relationship as a "causal connection" which is sometimes referred to as "a causal constraint".<ref name=":1">{{Cite journal|last=Wright|first=Crispin|date=1992|title=On Putnam's Proof That We Are Not Brains-in-a-Vat|url=https://www.jstor.org/stable/4545146|journal=Proceedings of the Aristotelian Society|volume=92|pages=67–94|doi=10.1093/aristotelian/92.1.67 |jstor=4545146 |issn=0066-7374|url-access=subscription}}</ref><ref name="putnam" /> Therefore, what it says is demonstrably false. Alternatively, if the speaker is not actually a BIV, then the statement is also false. He concludes, then, that the statement "I'm a BIV" is necessarily false and self-refuting.<ref name=":0" /> This argument has been explored at length in philosophical literature since its publication. A potential loophole in Putnam's reference theory is that a brain on Earth that is "kidnapped", placed into a vat, and subjected to a simulation could still refer to brains and vats which are real in the sense of Putnam, and thus correctly say it is a brain in a vat according to Putnamian reference theory.<ref>{{Cite journal|last=Tymoczko|first=Thomas|date=1989|title=In Defense of Putnam's Brains|url=https://www.jstor.org/stable/4320079|journal=Philosophical Studies|volume=57| issue = 3|pages=294–295|doi=10.1007/BF00372698|jstor=4320079|s2cid=170928278|url-access=subscription}}</ref> However, the notion that the "pure" BIV is incorrect and the reference theory underpinning it remains influential in the philosophy of mind, language and metaphysics.<ref>{{Cite book|last=Heil|first=John|title=A Companion to Analytic Philosophy|publisher=Blackwell Publishers|year=2001|isbn=9780470998656|pages=404–412}}</ref><ref>{{Cite journal|last=Pritchard|first=Duncan|title=Putnam on Radical Skepticism: Wittgenstein, Cavell, and Occasion-Sensitive Semantics|url=https://www.dropbox.com/s/txcjor6qwz4wt98/PutnamOnRadicalScepticism.pdf?dl=0|journal=Engaging Putnam|pages=1–2}}</ref> Anthony L. Brueckner has formulated an extension of Putnam's argument which rules out this loophole by employing a disquotational principle. It will be discussed in the following two sections.

=== Reconstructions of Putnam's argument === An issue that has arisen with Putnam's argument is that his premises only imply the metalinguistic statement "my utterances of 'I am a BIV' are false", but a skeptic may demand the object-language statement "I am a BIV" to be proven.<ref name=":5">{{Cite journal|last=Brueckner|first=Anthony L.|date=1986|title=Brains in a Vat|url=https://www.jstor.org/stable/2026572|journal=The Journal of Philosophy|volume=83|issue=3|pages=148–167|doi=10.2307/2026572|jstor=2026572 |issn=0022-362X|url-access=subscription}}</ref><ref name=":6">{{Cite journal|last=Warfield|first=Ted A.|date=1995|title=Knowing the World and Knowing Our Minds|url=https://www.jstor.org/stable/2108437|journal=Philosophy and Phenomenological Research|volume=55|issue=3|pages=525–545|doi=10.2307/2108437|jstor=2108437 |issn=0031-8205|url-access=subscription}}</ref> To combat this issue, various philosophers have reconstructed Putnam's argument. Some, like Anthony L. Brueckner and Crispin Wright, have taken approaches that utilize disquotational principles.<ref name=":5" /><ref name=":1" /> Others, like Ted A. Warfield, have taken approaches that focus on the concepts of self-knowledge and priori.<ref name=":6" />

==== The disjunctive argument ==== One of the earliest but influential reconstructions of Putnam's transcendental argument was suggested by Anthony L. Brueckner. Brueckner's reconstruction is as follows: "(1) Either I am a BIV (speaking vat-English) or I am a non-BIV (speaking English). (2) If I am a BIV (speaking vat-English), then my utterances of 'I am a BIV' are true if I have sense impressions as of being a BIV. (3) If I am a BIV (speaking vat-English), then I do not have sense impressions as of being a BIV. (4) If I am a BIV (speaking vat-English), then my utterances of 'I am a BIV' are false. [(2), (3)] (5) If I am a non-BIV (speaking English), then my utterances of 'I am a BIV' are true if I am a BIV. (6) If I am a non-BIV (speaking English), then my utterances of 'I am a BIV' are false. [(5)] (7) My utterances of 'I am a BIV' are false. [(1), (4), (6)]"<ref name=":5" /> Though these premises further define Putnam's argument, they do not so far prove "I am not a BIV", because, although the premises imply the metalinguistic statement "my utterances 'I am a BIV' are false", they do not yet imply the object-language statement "I am not a BIV". To achieve the Putnamian conclusion, Brueckner strengthens his argument by employing the disquotational principle "My utterances of 'I am not a BIV' are true if I am not a BIV." This statement is justified since the metalanguage that contains the tokens for the disquotational principle also contains the object language tokens to which the utterances 'I am not a BIV' belong.<ref name=":5" />

[[File:Brainthatwouldntdie film poster.jpg|thumb|upright|A poster for the film ''The Brain That Wouldn't Die, 1962'']]

== In fiction == {{Main article|Isolated brain#In fiction}}

{{Div col|small=no}} * ''Agents of S.H.I.E.L.D.'', Season 4 * ''Alita: Battle Angel'' * ''Avatar'' * ''Bliss'' * "The Brain of Colonel Barham", a 1965 episode of the TV series ''The Outer Limits'' * ''The Brain of Morbius'' * ''Brain (novel)'' * ''Brainstorm'' * ''Caprica'' * ''Chappie'' * ''The City of Lost Children'' * ''Cold Lazarus'' * ''The Colossus of New York''<ref>{{cite web |url=http://monsterhuntermoviereviews.com/2013/09/27/the-colossus-of-new-york-1958/ |title=The Colossus of New York (1958) |date=September 27, 2013 |website=monsterhuntermoviereviews.com |publisher=MonsterHunter |access-date=March 11, 2018 |quote=It turns out that Jeremy's brain was sitting in a glass case of water hooked up to an EEG machine which led me to believe that they must have had some kind of clearance sale on set leftovers from Donovan's Brain.}} (with photo).</ref> * ''Dark Star'' * ''Donovan's Brain'' * ''Existenz'' * ''Fallout series'' ** ''Point Lookout'', an expansion pack for ''Fallout 3'' ** ''Old World Blues'', an expansion pack for ''Fallout: New Vegas'' ** ''Automatron'', an expansion pack for ''Fallout 4'' * "Flashes Before Your Eyes", an episode of ''Lost'' * ''Futurama'' * Gangers{{Broken anchor|date=2024-06-24|bot=User:Cewbot/log/20201008/configuration|target_link=List of Doctor Who universe creatures and aliens#Gangers|reason= The anchor (Gangers) has been deleted.}} in ''Doctor Who'' * ''Ghost in the Shell'' * ''Inception'' * "The Inner Light", an episode of ''Star Trek: The Next Generation'' * {{interlanguage link|Kavanozdaki Adam|tr}} * ''Lies of P'', in the Overture DLC * ''Lobotomy Corporation'' * ''The Man with Two Brains'' * ''The Matrix'' film series * "Out of Time", an episode of ''Red Dwarf'' * ''Possible Worlds'' * ''Psycho-Pass'' * ''Repo Men'' * ''RoboCop'' * ''Saints Row IV'' * "Ship in a Bottle", an episode of ''Star Trek: The Next Generation'' * ''Sid Meier's Alpha Centauri'' * ''Soma'' * ''Source Code'' * "Spock's Brain", an episode of ''Star Trek: The Original Series'' * ''The Star Diaries'' * ''Steins;Gate 0 '' * ''Strange Days'' * ''The Thirteenth Floor'' * ''Total Recall'' * ''Transcendence'' * ''Tron'' * ''Tron: Legacy'' * ''Upload (TV series)'' * "The Vacation Goo", an episode of ''American Dad!'' * ''Where am I?'', written by Daniel Dennett * ''The Whisperer in Darkness'' * "White Christmas - Part II", an episode of ''Black Mirror'' * "William and Mary" by Roald Dahl ** Adapted into the first episode of ''Way Out'' in 1961 ** Adapted again for ''Tales of the Unexpected'' in 1979 * ''World on a Wire''

==References== {{reflist}}

==External links== {{Commons category|Brain in a vat}} '''Philosophy''' * {{cite SEP |url-id=skepticism-content-externalism |title=Skepticism and Content Externalism |last=Brueckner |first=Tony}} * {{cite IEP|url-id=brainvat/}} * [http://chaospet.com/281-meaty-mouths/ Inverse "brain in a vat"] * [https://books.google.com/books?id=-7wANgqooB4C&pg=PA1 Putnam's discussion] of the "brains in a vat" in chapter one of {{cite book|title=Reason, Truth, and History|url=https://books.google.com/books?id=h3g3GicFWGoC |publisher=Cambridge University Press |location=Cambridge |year=1981 |page=222|isbn=978-0-52129776-9 }} * [http://www.sechumscm.org/WhereAmI.html 'Where Am I?'] by Daniel Dennett * [https://web.archive.org/web/20180724151447/http://www.mindspring.com/~mfpatton/harper's.htm "Brain in a Vat Brain Teaser"] – ''Harper's Magazine'' (1996)

'''Science''' * [https://web.archive.org/web/20160304042943/http://neural.bme.ufl.edu/page13/assets/NeuroFlght2.pdf ''Adaptive flight control with living neuronal networks on microelectrode arrays''] * [https://dx.doi.org/10.1007/978-3-540-78317-6_3 ''Architecture for Neuronal Cell Control of a Mobile Robot'']

{{DEFAULTSORT:Brain In A Vat}} Category:Hypothetical technology Category:Science fiction themes Category:Thought experiments in philosophy