Hilary Putnam had many achievements in the field of philosophy. Here's some context about his concept of "brain in a vat"[1], in his 1981 book, "Reason, Truth and History".
The brain-in-a-vat concept was famously used in the The Matrix films.[2]
A summary from Philosophy Index: "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." [1][3]
Does he take for granted that the mind == the brain? Because that seems philosophically tenuous to me.
> For the body-mind interface, if any, is far from simple. Certainly the mind is not the only factor that organizes, unites or directs the body. The body manifests perfection at its conception, and in the days thereafter when it is still a microscopic embryo that could hardly be said to possess a mind its
developing blood and immune system also react directly and independently to throw off poisons or diseases without any knowledge or known mental influence.
-- Guy Murchie, The Seven Mysteries of Life
We were all doing "intelligent" things well before we had brains...
For me at least, Murchie's book was a revelation. I was ignorant of the possibilities he discusses of "movement without muscles, sight without eyes, hearing without ears, smelling without a nose, thirst quenching without drinking, eating without a mouth, digestion without a stomach or excretion, reproduction without sex, thinking without a brain and life without rest, sleep or death."
I don't now feel we are in the position to be drawing philosophical lines around what is the mind, the self, etc, when so much is still unknown.
OK, I'll bite. What moves "without muscles"? Single-celled organisms do, for sure. But the actin-myosin ratchet is a key part of the eukaryotic cytoskeleton that handles movement. The bacterial machinery is more distantly related, but still analogous. Even viruses use analogous machinery.
Greg Egan's Orthogonal trilogy features some amazing single celled organisms :)
> Below the world of worms and burrowing snails we may consider microscopic creatures like the ameba, who oozes along by pushing out lobes or ruffles of his single cell protoplasm and just flowing into them. His locomotion system (often called "ruffling") was only recently elucidated. It works in each lobe something like an advancing jet of jelly that spreads like the crown of a fountain at its forward end, turning outward in all directions, then back in the form of a surrounding cuff that condenses into a sleeve stiff enough to grip the ground until, turning once more in the rear, it liquefies and pours inward through the center. Biologists used to think that a muscle-like squeezing of the sleeve's protoplasm at the hind end pushed the jelly forward like toothpaste out of its tube, but newer evidence strongly indicates that it is the continuous contraction of the jelly at the forward "fountain zone" (where it turns and stiffens) that literally pulls the central stream steadily ahead. So the consensus of opinion now is that the ameba advances somewhat as does an oriental king, by having his carpet swiftly unrolled before him as he walks, then as nimbly rerolled behind for further unrolling ahead.
> Another method of microbe locomotion, up to several hundred times faster but still slow in human terms, is that of flagella or bacilli with tails. Some of them propel themselves by a recently discovered swivel motion, each flagellum lash rotating freely about its axis like the rigid propeller of a small airplane, generally pulling from the front end and changing course by reversing the direction of rotation. So far as I know, this is the only true wheel motion produced by nature before man invented the wheel about 3500 B.C. and it is powered by the equivalent of a reversible microscopic engine, something technological man has not learned how to make even today.
> A different system again is that adopted by ciliates, common in mud and ponds, whose bodies are covered with thousands of rapidly waving hairs called cilia. Up to 20 times a second each cilium (one thousandth of an inch long) makes its stroke, much like a human swimmer's arm action, first reaching gently forward edgewise for minimum resistance, then sweeping rigidly backward broadside for maximum resistance, the beats coordinated in beautiful rhythmic waves of succession, like pistons in an engine or stalks of wheat blowing in the wind. Even some visible animals use ciliated drive, notably two kinds of comb jellyfish the sizes of a gooseberry and a walnut, and often called respectively the "sea gooseberry" and "sea walnut," each of which has eight longitudinal belts of cilia (coordinated by a special balance organ) that steer and propel it like a spherical Caterpillar tractor.
Good question. As far as the thought experiment itself, it's really just a modern phrasing of Descartes' thought experiment. I have no idea if Putnam was even the first to mention a BIV.[0]
The real novelty is Putnam's response, based on the causal theory of reference or content externalism or something like it (I'm fuzzy on this point). I hope I can do it justice from memory.
He argues that because the brain in a vat has never had the appropriate sort of causal contact with external objects, its thoughts don't refer to them. So the brain has whatever brain states go on in me when I think "the sky is blue", but it has never seen the sky, and so its mental states don't refer to the sky. They refer to something else. Probably some disjunctive property of however the apparatus stimulates the brain's nerves (it's really hard to say what this is). It turns out then, that the brain is not falsely believing/failing to know the facts that we might think about by thinking "the sky is blue", it's accurately representing some other kinds of facts. So that type of scepticism is self-undermining, because it attributes thoughts to the BIV that it couldn't possibly have.
I should add that it seems to me that while this argument is tremendously creative, it belongs to a whole strand of philosophy from the 80s that seems to have died out. There's a decent chance you'll read some Putnam, but AFAIK people aren't publishing much on his BIV argument (though people use the example of a brain in a vat sometimes).
[0] Arguably, Descartes posited that the deceiver could deceive you about anything, including logical relations, while the BIV case just involves people giving you misleading sensations, so that's one conceivable difference in the discussions, but that's not a point that I ever saw anyone discuss in detail. It matters for Descartes scholarship, but that's all.
One difference is <s>Putnam concludes you can't tell whether life is an illusion or not</s>, whereas Descartes concludes you can and also god exists. Setupwise it's essentially the same.
EDIT: I got Putnam wrong. There is still the theistic difference though.
The brain-in-a-vat concept was famously used in the The Matrix films.[2]
A summary from Philosophy Index: "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." [1][3]
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Links: [1] http://www.philosophy-index.com/putnam/brain-vat/ [2] http://consc.net/papers/matrix.html [3] https://philosophy.as.uky.edu/sites/default/files/Brains%20i...