sophie

Any ideas of what a casual mental connection may be?

I thought I was a superior alien trapped in an Earth body, so what is wrong with that...

John Page

An idea, of course.

Bill

It is my understanding that the causal connection that Putnam referred to was normally supplied by "reliable" sensory inputs (if the sensory inputs were not reliable, then causation would be lacking; at least, I believe that is the argument....).

BiVtism (or more formally, Solipsism) is normally associated with the assertion that no external source of information is "reliable" (or, no senses even exist, in the extreme case) and, consequently, no logical proof can possibly get beyond Des Carte's cogito, ergo sum assertion. To get beyond BiVtism, some source of information that has at least some predictable degree of reliability must be presumed. This is the faith that every human must essentially have: that our built-in sensory inputs (sight, hearing, touch, taste, etc.) have at least some predictable degree of reliability. Once we take that assertion on faith, we can proceed to disprove BiVtism through the use of Ockham's Razor (which, by the way, can also be used to justify taking our sensory inputs on faith as having some predictable degree of reliability). After all, on a purely probabilistic analysis, it seems far more likely that the state of affairs reported to be true by my own sensory inputs is, in fact, at least close to what is actually the case than it would seem that I am actually a brain-in-a-vat and that all of my sensory inputs are actually forged by forces or entities unknown (who have also provided both the vat and my brain as well).

The very fact that one exists and perceives change argues strongly for the existence of other forces and/or entities which have caused both my own existence and my perception(s) of change. If any such forces and/or entities do exist, then I am immediately left to wonder at my causal relationship with those selfsame forces and/or entities (a la Putnam). Eventually, I feel compelled to conclude that the case where I am what I perceive myself to be is far more likely than the case where I am a brain-in-a-vat, thus justifying my faith in the essential correctness of my own sensory inputs (justifying, but never completely proving; this is an important limit!).

At least, "that's my story and I'm sticking to it!"

== Bill

gumb

hi phyrro, hi bill.

i've been wondering about how useful causal theories of reference are too. I mean what if (I'm sure I picked this idea up from what one of you two said ) I WAS a brain in a vat, but the programmer had tricked me into beleiving in a strange idea call 'causality', and in the real world there was no such thing! I think that sort of argument would be enough to show putnam was wrong straight away? I'm not sure.


what's interested me about this problem from the start though, is the use that putnam makes of the notion of necessity to make his case. I wonder if he is too committed to 'modal realism' along the lines of what David Lewis preaches?

here's what I mean.

Putnam argues that it is logically impossible for the statement 'I am a brain in a vat' to be true, for the reasons given above, I.e if I wasn't a BiV it would be false, if I was I wouldn't be able to state the proposition with the correct referent. . .

ok, given that, this is the part that interests me. He argues given the fact ( ) that he has deduced 'I am a BiV is necessarily false', he can move to the corrallary (is that the right word?) that 'It is not possible that I am a BiV'. the step seems a merely logical (analytic ) one, but he then uses this result as a refutation of the sort of cartesian skeptiscism that bill was talking about.

I find this deeply problematic. how does he manage to jump from a what phyrro called 'playing games with words' to a conclusion about what is in fact the case, and indeed a refutation of skeptisism?


I don't know if anyone else has any thoughts on this.

John Page

If this were the case, then I would say that the programmer could not have caused you to believe by trick or other artifice to believe in causality because there is no such thing.

Cheers, John

Pyrrho

If that is the case, then the application of this idea to the "Brain in a Vat" hypothesis is simply begging the question. The whole point of the brain in a vat thought experiment is to suggest that we have no reason to believe that our senses are reliable. Nor can one come up with any probability on such matters, simply because we must be able to rely on our senses in order to use any sensory data to make probabilistic assessments. We don't see any brains in vats, so some might think that in our experience, it is unlikely for a person to be a brain in a vat, but that is completely worthless as it depends on the reliability of our senses to supply the premises, and that is not something that can be assumed in this context. The whole issue is whether or not we can rely on our senses, so we cannot assume that in order to prove it. Certainly, IF we can rely on our senses, then we can rely on our senses, but such a tautology tells us absolutely nothing about whether or not we can, in fact, rely on our senses.

So, as I indicated previously, he has given us no reason to believe anything about the source of our sensory inputs. If Putnam has been represented fairly by gumb, then Putnam is playing with words, not supplying any reason to believe that one can rely on one's senses.

gumb

doesn't this depend upon your notion of truth? and surely truth is the critical notion, as putnam claims to have proved that "I am a brain in a vat" cannot be true.

putnam seems to adopt a sort of coherence theory of truth. truth for putnam is epistemic, so it is based on warrented beleifs. although he might not think that the "most warrented" set of beliefs held on may 27th 2003 represents absolute truth, he thinks that truth can never consist in anything more than than a set of "warrented beleifs".

this would explain why he thinks that showing "I am a brain in a vat" to be a logical, necessary truth makes it a valid refutation of cartesian skeptisism. no process of epistemic justification can unbound his langauge game, and for putnam the 'best' possible epistemic justification is truth. therefore his is right, we cannot in fact be BIV.

if you take a different viuew of truth however, and say that truth (or Truth as philosoft put it) is something which is not radically epistemic in nature, but external to processes of cognition, then putnam's claim to have refuted skeptism becomes exactly what you called it - a clever word game and not one iota more.


I have an exam about this on wednesday so any inconsitencies you might spot will be gratefully received


thank you all who have replied :notworthy

Pyrrho

With the "Brain in a Vat" thought experiment, the literal description is unimportant; it is merely to get one to consider whether or not one can trust one's senses. So even if Putnam were right that one could not literally be a brain in a vat, it would be beside the point. The important aspect is whether or not we can have any reason at all to trust our senses.

Now, if Putnam believes that all of our talk is essentially about our sensations, and not an "external reality", then I have no particular quarrel with him (other than being overly obscure in his discourse). But, if he claims that we are "warranted" (whatever that means) in forming the belief that our senses are caused by external objects (as most people believe), then I don't think he has presented anything to support this. And I don't think any purely linguistic analysis ever could.

As for a coherence theory of truth, what, precisely, do you mean? How is the belief that one is hooked up to a computer, providing it with inputs and reacting to its outputs, any less coherent than the idea that you are sitting in front of a computer screen as you read this? (Think of both of those with the appropriate accompanying beliefs.)


Now, if he rejected the whole discussion as being metaphysical BS, and said that talk of an "external reality" was nonsensical from the start, I wouldn't have a problem with that, either. But he seems to not do that at all, because he would then be saying that the brain in a vat hypothesis was nonsensical (as any talk of an "external reality" would be nonsensical) rather than necessarily false as he seems to be saying (judging the matter from what you have presented).

If I have understood you correctly, all that he has been saying is that you could not be a brain in a vat, because your idea of "brain" and "vat" would not be appropriately connected with what you would be, and therefore you would be talking about something other than what you were. He seems to be presupposing a kind of metaphysical realism in which one knows that one's concept of "brain" and "vat" are connected to "external objects" in some way. Which is really just presupposing that one's senses are an accurate representation of reality in order to prove that one could not be a brain in a vat. It is playing a linguistic game in order to hide the fact that he is committing the fallacy known as "begging the question."

Again, the whole point of the thought experiment is to say that our senses may not 'represent' reality at all.


If you use anything that I have stated on your test, I expect you to refer to me by name and give credit where credit is due. You may refer to me as "that great philosopher Pyrrho who posts at Internet Infidels".

acronos

I must be missing something simple, because this makes no sense to me. What about red dragons and blue elves? I have considered their existence, however I have never sensed or experienced one before. You might say, you’ve seen pictures. What about the first person who ever drew or thought of a dragon, had he seen pictures? I personally don’t believe dragons exist in our world. If I can imagine something that I have never experience that doesn’t exist, how much more so should I be able to imagine something that I can’t experience yet does exist?

John Page

I think the cause of the experience is at the heart of the matter. Interesting.... now I'm trying to imagine something I can't experience (or recall the memory of having experienced).