Brain in a vat

Brain in a vat

In philosophy, the brain in a vat is an element used in a variety of thought experiments intended to draw out certain features of our ideas of knowledge, reality, truth, mind, and meaning. It is drawn from the idea, common to many science fiction stories, that a mad scientist might remove a person's brain from the body, suspend it in a vat of life-sustaining liquid, and connect its neurons by wires to a supercomputer which would provide it with electrical impulses identical to those the brain normally receives. According to such stories, the computer would then be simulating reality (including appropriate responses to the brain's own output) and the person with the "disembodied" brain would continue to have perfectly normal conscious experiences without these being related to objects or events in the real world.

The simplest use of brain-in-a-vat scenarios is as an argument for philosophical skepticism and Solipsism. A simple version of this runs as follows: Since the brain in a vat gives and receives the exact 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 he believes, say, that he is walking down the street, or eating ice-cream); in the latter case they are false. Since, the argument says, you cannot know whether you are a brain in a vat, then you cannot know whether most of your beliefs might be completely false. Since, in principle, it is impossible to rule out your being a brain in a vat, you cannot have good grounds for believing any of the things you believe; you certainly cannot know them.

This argument is a contemporary version of the argument given by Descartes in Meditations on First Philosophy (which he eventually rejects) that he could not trust his perceptions on the grounds that an evil demon might, conceivably, be controlling his every experience. It is also more distantly related to Descartes' argument that he cannot trust his perceptions because he may be dreaming (Descartes' dream argument is preceded by Zhuangzi in "Chuang Chou dreamed he was a butterfly".). In this latter argument the worry about active deception is removed.

Philosophical responses

Such puzzles have been worked over in many variations by philosophers in recent decades. American philosopher Hilary Putnam popularized the modern terminology over Descartes's "evil daemon," although it brings up such complications and objections as whether the mind is reducible to the workings of a brain. Some, including Barry Stroud, continue to insist that such puzzles constitute an unanswerable objection to any knowledge claims.^[1] Hilary Putnam argued against the special case of a brain born in a vat.^[2] In the first chapter of his 1982 Reason, Truth, and History, Putnam claims that the thought experiment is inconsistent on the grounds that a brain born in a vat could not have the sort of history and interaction with the world that would allow its thoughts or words to be about the vat that it is in.

In other words, if a brain in a vat stated "I am a brain in a vat", it would always be stating a falsehood. If the brain making this statement lives in the "real" world, then it is not a brain in a vat. On the other hand, if the brain making this statement is really just a brain in the vat then by stating "I am a brain in a vat" what the brain is really stating is "I am what nerve stimuli have convinced me is a 'brain,' and I reside in an image that I have been convinced is called a 'vat'." That is, a brain in a vat would never be thinking about real brains or real vats, but rather about images sent into it that resemble real brains or real vats. This of course makes our definition of "real" even more muddled. This refutation of the vat theory is a consequence of his endorsement, at that time, of the causal theory of reference. Roughly, in this case: if you've never experienced the real world, then you can't have thoughts about it, whether to deny or affirm them. Putnam contends that by "brain" and "vat" the brain in a vat must be referring not to things in the "outside" world but to elements of its own "virtual world"; and it is clearly not a brain in a vat in that sense. One of the other problems is that the supposed brain in a vat cannot have any evidence for being a brain in a vat, because that would be saying "I have what nerve stimuli have convinced me is evidence to my being a brain in a vat" and also "Nerve stimuli have convinced me of the fact that I am a brain in a vat"

Many writers, however, have found Putnam's proposed solution unsatisfying, as it appears, in this regard at least, to depend on a shaky theory of meaning: that we cannot meaningfully talk or think about the "external" world because we cannot experience it; sounds like a version of the outmoded verification principle.^[3] Consider the following quote: "How can the fact that, in the case of the brains in a vat, the language is connected by the program with sensory inputs which do not intrinsically or extrinsically represent trees (or anything external) possibly bring it about that the whole system of representations, the language in use, does refer to or represent trees or any thing external?" Putnam here argues from the lack of sensory inputs representing (real world) trees to our inability to meaningfully think about trees. But it is not clear why the referents of our terms must be accessible to us in experience. One cannot, for example, have experience of other people's private states of consciousness; does this imply that one cannot meaningfully ascribe mental states to others?

Subsequent writers on the topic have been particularly interested in the problems it presents for content: that is, how - if at all - can the brain's thoughts be about a person or place with whom it has never interacted and which perhaps does not exist.

References in popular culture

This "In popular culture" section may contain too many minor or trivial references. Please reorganize this content to explain the subject's impact on popular culture rather than simply listing appearances, and remove trivia references. (September 2009)

• The use of similar ideas in movies is not infrequent, as in "Abre Los Ojos" (Open Your Eyes) (or its American remake, Vanilla Sky), and The Matrix (a clear reference to both Plato's Allegory of the Cave and the brain-in-a-vat theory, though in that case entire bodies were preserved, rather than just brains). A similar sense of indistinction between virtual reality and reality appears in eXistenZ, a David Cronenberg film.
• The idea of a person's brain or even more abstractly, consciousness, being removed from the body appears in some of Stanisław Lem's novels. A related topic, an artificial mind being fed artificial stimuli by its mad-scientist creator, also appears there.
• In an episode of Stargate SG-1 (The Gamekeeper) the team visits an alien planet where they are imprisoned inside capsules that cause them to experience a simulated world controlled by a "gamekeeper". When they discover what has happened, the gamekeeper causes them to experience leaving the capsules again so that they will think that they have left the artificial world. They then experience an artificial version of their own world nearly indistinguishable from reality, but are eventually able to determine that they are still inside the machines and escape.
• Motoko Kusanagi, the protagonist of Ghost in the Shell, is something similar to a brain in a vat. Her entire body is cybernetic except for her brain. She muses at several times that maybe she is just a computer program that believes it used to be human. In terms of the series, her ghost is artificial. The movie version opens with a sequence showing the creation of her cybernetic body, in which her brain is shown covered by an electronic shell.
• In "Cold Lazarus", a 1996 drama by Dennis Potter set in a 24th century Britain, a group of scientists revive the mind of a 20th century writer. As more of his thoughts and memories are unearthed, it becomes evident not only that his mind is conscious of its predicament, but also that he is attempting to communicate with the scientists, and is pleading to be allowed to die.

See also

• Dream argument
• Experience Machine
• Evil daemon
• Internalism and externalism
• Neurally controlled animat
• Simulated reality
• Skeptical hypothesis
• Solipsism
• Spock's Brain episode of Star Trek
• The Matrix (series)

References

External links

Wikimedia Commons has media related to: Category:Brain in a vat

• "Brains in a Vat" article by Tony Brueckner in the Stanford Encyclopedia of Philosophy
• Putnam's discussion of the "brain in a vat" in chapter one of Reason, Truth, and History
• 'Where am I?' by Daniel Dennett
• Thomas DeMarse, Karl Dockendorf, Adaptive flight control with living neuronal networks on microelectrode arrays
• Xydas, D.,Norcott, D., Warwick, K.,Whalley, B.,Nasuto, S.,Becerra, V.,Hammond, M.,Downes, J.and Marshall, S.,Architecture for Neuronal Cell Control of a Mobile Robot