gumb

hi, it's my first proper post, but I've been lurking for a while . . . i've got to say i'm impressed with the intelligent and informed discussions you got in here

anyway, what with all the hype about the new 'matix reloaded' film, I've been interested in the 'brain-in-a-vat' hypothesis, and notably smart-ass ways of refuting it.

putnam comes up with a what he considers a devastating refutation of the whole idea. as I understand him, he says that if I were a brain in a vat, and I were to consider the proposition:

"I'm a brain in a vat"

then because my experience is of an exclusively matrix induced nature, I would be referring to a 'matrix-induced-brain' and a 'matrix-induced-vat'.

that's fair enough, but then he says that because "meanings ain't just in the head" the statement is meaningless, or self-refuting- with the result I can't be a brain in a vat.

now I'm sure something has gone wrong somewhere, and it's got to be either my understanding of putnam, or some of the philosophical convictions putnam is considering (actually probably both )

suffice to say I'm confused. any help untangling the knot much appreciated

John Page

Hi gumb!

We're all brians in vats. All that remains is debate what kind of vat it is.

Cheers, John

gumb

alright john

what you said is just the attitude I have actually, I mean surely the meanings of the words we use can't determine what is and is not possible? surely it's the other way round?

putnam argues:

1. If I am a brain in a vat, then I cannot have the thought that I am a brain in a vat.

2. But I can have the thought that I am a brain in a vat.

3. Therefore, I am not a brain in a vat.

his logic does seem to show that �I am a brain-in-a-vat� is necessarily false, and obviously this will mean it cannot be possible that it is true!

this has really been bothering me the last few days? putnam is clearly wrong, but I can't seem to understand why! I mean what if I was a brain in a vat, and I never considered the thought "I am a brain in a vat"? surely then I would be a brain in a vat!!

but what if I suddenly had the thought "I am a brain in a vat", perhaps while I waiting for the train, would I suddenly cease to be a brain a vat, or would my entire life history change?

as will be evident, I'm very confused about this :boohoo:

John Page

This premise is false. One would need to define vat such that the human body could not fit that description.

gumb

again, my first instinct. the definition of vat is at fault. however the vat could be metal, or plastic, a human body, or whatever. all the problem presupposes is that whatever the vat 'is' it is part of a world which is inaccessible for our senses

so even if the vat was a human body, the problem is that it is located in a world which is different to the one we experience. like the 'power plants' on the matrix films the vat is not part of a world which is accessible to our sense-organs.

what ever the 'vat' itself is, I will only be able to refer to the vat IF i am not a brain in a vat, so the statement 'i am a brain in vat' is necessarily false, and therefore it is not possible I am a brain in a vat.

thus the matrix is logically impossible.

John Page

I'm having trouble with "located in a world that is different".

Cheers, John

gumb

sure, different was the wrong word to use. "inaccessible" is better. so I would say:

so even if the 'vat' was a human body, the problem is that it is located in a world which is inaccessible to our sense-organs. we can never experience the 'vat', furthur there is no possible causal chain leading from the 'vat' to our sense-field.

thus we cannot say "I am a brain in a vat", and have it be true, if we are a brain in a vat.

John Page

I think I understand now - but we can experience things in a number of ways so I'm still not sure I agree with your conclusion. How about mind-probes, mind-altering drugs, controlled experiments to determine the physical cause of subjective experience etc.

Cheers, John

gumb

thanks, explaining it properly has made it a lot clearer to me too.

I think I know what your getting at. are you suggesting that the whole 'brain-in-a-vat' idea might be suspect to begin with?

mind probes, hallucigens (which circulate chemically around the synapses and stuff), and perhaps certain experiments are all physically invasive to the 'real' brain, and as such would be impossible for a computer to simualte?

I don't know, I think perhaps the computer could simulate them, in the case of LSD or E or whatever, it could just administer an intovenous doses of said drug. perhaps something analagous in the case of certain experiments.

happily I'm not aware of what a mind probe involves

is this what you meant?

Mageth

Go kick a rock. Note that it kicks back.