Friday, November 22, 2013

Are We Just a Brain in a Jar?

After all these philosophical ponderings about the validity of the existence of a brain in a jar, science answers philosophy by bringing contemplation in to scientific fact. Transferring a human brain into a brain in a jar is now possible, at least in demonstrative parts of simplistic nature. Careful what you ask for, or in this case, think about, because it just might come true...

The “Brain in a Vat” thought experiment is an update to RenĂ© Descartes’ evil demon problem. Hilary Putnam is credited with this update. The example supposes that a mad scientist has removed your brain, and placed it into a vat of liquid to keep it alive and active. The scientist has also connected your brain to a powerful computer, which sends neurological signals to the brain in the way the brain normally receives them. Thus, the computer is able to send your brain data to fool you into believing that you are still walking around in your body.

The brain-in-a-vat thought experiment is generally used to ask the question: how do you know that you are not a brain in a vat? The question mirrors an early one from Descartes, which asks how you are to know that there is not an evil demon feeding false information to your senses. The essential conclusion is that, from the perspective of the brain itself, it is impossible to tell whether it is a brain in a vat or a brain in a skull.

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 based on an idea, common to many science fiction stories, that a mad scientist, machine, or other entity 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 brain in a vat arguement
The Brain in a Vat thought-experiment is most commonly used to illustrate global or Cartesian skepticism. You are told to imagine the possibility that at this very moment you are actually a brain hooked up to a sophisticated computer program that can perfectly simulate experiences of the outside world. Here is the skeptical argument. If you cannot now be sure that you are not a brain in a vat, then you cannot rule out the possibility that all of your beliefs about the external world are false. Or, to put it in terms of knowledge claims, we can construct the following skeptical argument. Let “P” stand for any belief or claim about the external world, say, that snow is white.
If I know that P, then I know that I am not a brain in a vat
I do not know that I am not a brain in a vat
Thus, I do not know that P.

Skepticism and Content Externalism
The Cartesian skeptic puts forward various logically possible skeptical hypotheses for our consideration, such as that you are now merely dreaming that you are reading an encyclopedia entry. The more radical Evil Genius hypothesis is this: you inhabit a world consisting of just you and a God-like Evil Genius bent on deceiving you. In the Evil Genius world, nothing physical exists, and all of your experiences are directly caused by the Evil Genius. So your experiences, which represent there to be an external world of physical objects (including your body), give rise to systematically mistaken beliefs about your world (such as that you are now sitting at a computer). (For an overview of the problem of external world skepticism, see Greco 2007.) Some philosophers would deny that the Evil Genius hypothesis is genuinely logically possible. Materialists who hold that the mind is a complex physical system deny that it is possible for there to be an Evil Genius world, since, on their view, your mind could not possibly exist in a matterless world. Accordingly, a modern skeptic will have us consider an updated skeptical hypothesis that is consistent with materialism. Consider the hypothesis that you are a disembodied brain floating in a vat of nutrient fluids. This brain is connected to a supercomputer whose program produces electrical impulses that stimulate the brain in just the way that normal brains are stimulated as a result of perceiving external objects in the normal way. (The movie ‘The Matrix’ depicts embodied brains which are so stimulated, while their bodies float in a vats.) If you are a brain in a vat, then you have experiences that are qualitatively indistinguishable from those of a normal perceiver. If you come to believe, on the basis of your computer-induced experiences, that you are looking at at tree, then you are sadly mistaken.

Brain in a Vat by John Pollock (PDF) - Philosophical Doubts 

Hawking is a Brain in a Vat
The generally accepted form of wishing someone a happy birthday is to sing to the lucky person. Or perhaps buy him or her a gift. A less accepted form is to compare the birthday person to Darth Vader and suggest he or she is merely a "brain in a vat." Still, Helene Mialet, a UC Berkeley anthropologist of science, chose the path slightly less trodden. Writing in Wired, she offered that perhaps Hawking should be referred to as Obi-Wan refers to Darth Vader: "More machine than man." She went on to suggest that the eminent physicist's beautiful mind is made beautiful only with large amounts of external assistance: He is delegated across numerous other bodies: technicians, students, assistants, and of course, machines. Hawking's "genius," far from being the product of his mind alone, is in fact profoundly located, material, and collective in nature.

Putnam on Brain in a Vat
Putnam’s argument is based on a couple of claims about words, pictures or mental images, and even thoughts or intentions link to things. Negatively, resemblance is not sufficient (nor is it necessary) for reference / aboutness / intentionality. Positively, one needs to do some further work and Putnam suggests standing in the right sort of causal relation. Using this background, the argument runs as follows:

Words/thoughts can only refer to things that stand in the right sort of causal relation to them. So ‘vats’ stand either for real vats or vats-in-the-image (ie computer generated). If we are not brains in a vat, then the “we are brains in a vat” refers to real vats and is false. If we are brains in a vat then “we are brains in a vat” refers to vats-in-the-image and is false. So “we are brains in a vat” is never true, is always false.
Putnam himself summarises his argument thus:

It follows that if their ‘possible world’ is really the actual one, and we are really the brains in a vat, then what we now mean by ‘we are brains in a vat’ is that we are brains in a vat in the image or something of that kind (if we mean anything at all). But part of the hypothesis that we are brains in a vat is that we aren’t brains in a vat in the image (i.e. what we are ‘hallucinating’ isn’t that we are brains in a vat). So, if we are brains in a vat, then the sentence ‘We are brains in a vat’ says something false (if it says anything). In short, if we are brains in a vat, then ‘We are brains in a vat’ is false. So it is (necessarily) false. [Putnam 1981]