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Turing machine applied to virtual reality

  1. Oct 22, 2006 #1
    How can one readily determine that the reality one experiences is real, not virtual - perhaps through Turing machine logic?
  2. jcsd
  3. Oct 23, 2006 #2
    If we are indeed in a vitual system then we'd be living under vitual rules and any logic of ours would be restricted under those rules and hence could not predict or speculate about 'outside' the system.
  4. Oct 24, 2006 #3


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    Hi Loren,
    I think you're refering to the "http://plato.stanford.edu/entries/brain-vat/" [Broken]" thought experiment in which one can't really 'know' if they're a brain in a vat or not. This assumes the virtual world is reproduced faithfully and exactly. It also assumes you've been removed from experiencing a real world (ie: by an evil scientist) and you've been placed into a virtual world, something along the lines of the movie "The Matrix".

    That second assumption makes a sharp distinction between what we generally consider a virtual world, and what Putnam suggests.
    I haven't read through all this yet, but it looks interesting. The situation Putnam has created seems to be applicable to religious versions of reality in which there is a god that creates everything, and thus we are no more 'real' than what that alleged god has imagined. I'll have to do some more reading on this topic later if you're interested in discussing.
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  5. Oct 24, 2006 #4

    How would BIV differ from "mind in a vat"? Does not the duality between scientist and brain, or god and mind assume a tangible horizon?

    Reminds me of a "Star Trek: Next Generation" episode where Riker as spy is captured and drugged into an alternate reality. He gradually realizes the flaws in this imposed illusion and escapes into the actual world.

    Pardon, I am a slow writer.
  6. Oct 25, 2006 #5

    Isn't our logic already restricted in that the actions that we take as a result of our logic always seems to be the "most sensible or common sense approach?" Granted, what is most sensible or common sense is not always what the "majority" think but on an individual basis we are already programmed to do the "most sensible or common sense" thing. Any thoughts?
  7. Oct 29, 2006 #6


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    Hi Loren,
    Not sure what you mean here. I think the term "brain" is preferred over "mind" when referring to a "brain in vat" (ie: as opposed to a "mind in vat") because we think of a brain as being a material thing which can be physically inside another material thing (vat) whereas a mind is not. A mind is had by the brain, or is supervenient on the physical 'brain' so the phrase "mind in a vat" doesn't make as much sense. It's not the vat that has a mind, it is the brain that has a mind.

    We might suggest a computer has a mind. We might say "mind in computer". And I think that makes a good paradigm to counter Putnam's "disjunctive argument". Putnam's argument basically goes like this. If one particular brain has never seen a real, green tree then that brain can't truly understand what a tree is. From the referenced article:
    In other words, if your reference to the tree is not based on actually seeing a tree, you can't have the same meaning as someone who has seen the tree. That's basically Putnam's argument against BIV's having the same experience as a brain that actually exists outside a vat.

    I think his argument fails because it assumes the BIV and the non-BIV are not actually identical. There are two key differences which are obvious when he talks about Martians having this experience without having seen a tree, but only a green blotch. 1. First, Martians have different physical brains, or we would at least make that assumption or we wouldn't use the term "Martian" to describe the organism seeing the tree. 2. Second, Putnam is suggesting they don't actually receive the same input, they receive input which is similar to a tree, but not a real tree. He calls it a blob of green paint. That's the second difference between the two concepts. From reading the article, it looks like the author, Tony Brueckner, also disagrees with Putnam for similar reasons.

    I think Brueckner hits the nail right off the bat and points out that if there are two identical (though he doesn't say identical) systems having identical inputs, then any mind which emerges in the brain should have identical experiences. Consider for a moment the computer mind paradigm. If we say a computer can have a mind, and that computer receives an input, during which it experiences something, and if we then note the change of states of the computer mind as being states 1 through n over time period dt, then any identical computer undergoing identical changes of state 1 through n over time period dt should also have identical experiences. I say this because we assume the mind is supervenient on the brain and thus there can be only one resulting experience from any given mechanism undergoing a series of state changes. This similarly applies to any material mechanism such as a biological brain. I don't see how it could be different (given the assumptions of mind being supervenient on the physical) for any other mechanism which is having a conscious experience.
  8. Oct 29, 2006 #7
    BIV reminds me of the state of a black hole, able to radiate randomly from its horizon, but not informationally. One black hole cannot communicate with another, or bilaterally with an outside observer. Here the black hole might represent a brain, the horizon a vat, as the inablity to radiate non-virtually characterizes the information paradox. It might be possible that a universe, like our own, of black holes with its own horizon can "play god" and as a relative white hole regain the lost quantum numbers.
  9. Dec 1, 2006 #8
    When it comes down to it, our existance, our brains, everything is made up of tiny particles which are made of tiny particles and so on until you get a 'particle' that is made of up just an electric charge. even our brains are just a hurricane of electrical activity, all of our senses our emotions, our thoughts are just the electricity in every synapse. so whats stopping our existance from being just an electrical storm in an empty void or complex software or a brain in a vat.
    if everything you percieve is just electrical activity in the brain, then wouldnt any input be considered 'reality'. whether its from an evil machine or the natural world, its all just imput. the only reason people find this troubling is because people have a natural drive for freedom, even when it comes down to simulated freedom the human instinct is to want more. we are parasites.

    its scary but if we were enslaved in a simulation, i think we have no right to say we dont deserve it.
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