Tuesday, November 18, 2008

Why we aren't brains in vats

Putnam argued that words derive their meanings from cause-and-effect relations to the world around us. And our use of words relies on the assumption that normal causal relations exist between out mental states and objects. If we are really vat-brains and such causal relations do not obtain, then in the sentence "we are brains in vats" the words don't really mean anything. Hence the sentence "we are brains in vats" can never be true.

12 comments:

Doctor Logic said...

Sounds reasonable to me.

Blue Devil Knight said...

If we are really vat-brains and such causal relations do not obtain, then in the sentence "we are brains in vats" the words don't really mean anything. Hence the sentence "we are brains in vats" can never be true.

Unless the world is sneaked in through the scientists, via all the details they have to put into their simulation of the world. If the simulation of the world in the computer (which is fed into the brain) has information about the world being modelled (which it would), then the brain could inherit such contents. It's like learning about who shot Kennedy through a newspaper rather than by perceiving the event itself.

Also, they could take an adult brain, which is pregnant with content because of its history of interactions with the real world, and then trigger these contentful representations via the simulation. Most of those thoughts would be false but they would still be thoughts with a certain content.

There are some that wouldn't be false such as 'I am a brain in a vat', or analytic truths about bachelors, or mathematical truths, or logical truths (to the extent that such things are true independently of experience). Of course, the 'I am a brain in a vat' would likely not be justified, so the person wouldn't really know it, but it would be true.

Anonymous said...

Hooray for the Causal Theory of Reference.

Ilíon said...

VR: "Putnam argued that words derive their meanings from cause-and-effect relations to the world around us. And our use of words relies on the assumption that normal causal relations exist between out mental states and objects. If we are really vat-brains and such causal relations do not obtain, then in the sentence "we are brains in vats" the words don't really mean anything. Hence the sentence "we are brains in vats" can never be true."

So, if a sentence is not and cannot be a sensible statement to the persons out of whose mouths the sentence comes, then the content (should that be pseudo-content?) of the sentence cannot be a statement and thus cannot be true? In any possible world? Should the sentence happen to emerge from the mouth(s) of the scientist(s) feeding stimuli to those brains, is the sentence still meaningless and therefore not possibly true?

Does the sentence become meaningful (and possibly true) if the scientists are able to say (of the brains-in-vats) "They are brains in vats?" What I mean is, since the scientists can, apparently, sensibly say "They are brains in vats," does it become sensible for the scientists of say of themselves, "We are brains in vats?" And, therefore, the scientists can never know whether they themselves are or are not brains in vats?

Is it also true that the sentences in a novel -- which are admittedly not-true -- are not statements? Are these sentences also meaningless, even though we all go about life acting as though we understand the sentences in the novels we choose to read?


VR: "... If we are really vat-brains and such causal relations do not obtain, then in the sentence "we are brains in vats" the words don't really mean anything. ... "

And yet, we all keep behaving as though the sentence has meaning and as though we know what that meaning is. How can this be, since the sentence is devoid of meaning? Are we all in on the con? Are we all pretending to understand the sentence, too embarrassed to admit to our fellows that we recognize no meaning in the sentence?

Joe said...

I agree with Illion and BDK’s good and creative points.

I think the question begging fallacy is way overused but, I wonder if the first sentence isn't to some extent begging the question: "Putnam argued that words derive their meanings from cause-and-effect relations to the world around us." Obviously if we are brains in vats this is unlikely to be true for us and our "words." (although as BDK said maybe the scientists do model their input from reality) I suppose it may not be question begging since she "argued" this. But we need to evaluate her argument for this proposition and how it would be the case if we were brains in vats.

Blue Devil Knight said...

Joe: Just for future reference, Hilary Putnam is a dude.

Victor Reppert said...

Hilary Rodham Putnam you mean?

Joe said...

:) Thank you. The name was familiar because I think I read something from him in college but I always assumed he was a she. Probably because of that first name.

Steve said...

I can't say I've ever found this sort of argument at all convincing.

Firstly, the argument relies on a causal theory of meaning which I'm far from convinced about.
Second, if we accept that theory, the conclusion to draw isn't "we aren't brains in vats" but "either (a) we have no idea what any of our thoughts refer to and/or mean or (b) we aren't brains in vats". The first seems perfectly coherent, though of course would, if true, become inexpressible in meaningful language. But the fact that in such a case we could not meaningfully describe our predicament just shows what a bad predicament it would be, not that it doesn't obtain.

Steve

Ilíon said...

That was my point, Steve.

Jim S. said...

Does Putnam's argument really require a causal theory of meaning? Can't we just say that if we were brains in vats, whatever connections that exist between our concepts and the realities to which they are supposed to refer no longer hold? As such, our concepts of "brains" and "vats" would have no connection, causal or otherwise, to any external reality, and so the idea is meaningless. I think you have to assume an externalist viewpoint for this argument to hold, but I don't see why the connection has to be an explicitly causal one. Am I missing something obvious?

Steve said...

Jim S,

For what it's worth, I agree with you. The argument can be rewritten to avoid the commitment to a causal theory of meaning. In essence it's a rewritten version of what we might call a "paradigm case" argument. Normally these arguments run as follows: we only know what "real" and "illusory" mean if we have met (and distinguished) examples of each, but if some scenario like being a brain in a vat obtains we haven't met examples of both kinds and don't know the meaning of each. But since we can make that distinction we can't be brains in vats. The causal theory of meaning merely helps explain why we'd have to have met examples of each type, but that requirement would hold on other theories of meaning too.

However, the doesn't mean that the argument escape the objections posed by Ilion and I.

Steve