Philosoft

As far as I can tell, you've only made a case that we can't have knowledge (justified true belief) of brain-in-a-vat-ism. It's possible that BIVism can be True, independent of our knowledge.

John Page

Athroporockism!

gumb

can it? (I just want to say first that your post has really got me thinking about this). wouldn't that mean you were an externalist? i.e. you think that truth values obtain independently of any particular mind?

I'm not sure, but I am someone who is suspicious of the idea of an absolute 'true world' external to the subject's perspective. given that, how can something be true, if I am entirely causally disassociated from it?

monkey mind

Maybe I'm missing something here. Why couldn't we have thoughts about it?

gumb

putnam adopts a causal theory of reference as one of his premises. he argues, convincingly, that in order to refer to something, you have to be causally related to it somehow.

if you really were a 'brain in a vat' then your thoughts about 'brains in vats' would refer not to your own brain and the vat which it was contained in, but to 'computer simulated brains' and 'computer simulated vats' (like in the matrix).

as your real brain, and the real vat which contained it, would be inacessible to you, you couldn't refer to those things. If you can't refer to them, then how can you think about them?

more specifically how can you think thoughts which can be then attributed as truth/knowledge.

(like you could think 'unicorns are herbivores', but not ever think you have grounds to know it/it be true )

Philosoft

I suppose I am an externalist, but I would say that it is [capital T]Truth that exists outside the mind.
Well, to take your example, even if we can justifiably believe that this world is not objectively real, we can't conclude BiVism without additional information, but we can conclude there is "something else at work." Proving BiVism would require a means of observing the vat and testing all potential falsifications. I don't really know how to go beyond that.

monkey mind

Ohhh okay. I think I understand now. You could think about abstract brains in vats, but you couldn't KNOW the vat that your brain is in because you couldn't sense it. If you don't know what kind of vat your brain is in then how can you know anything? Am I on track here? It makes sense

One problem I can think of is that we're assuming that our five senses provide us with information that is true, but how could we ever know this for sure? We can even think of cases where our sense lie to us, such as hallucinations.

Pyrrho

The idea that "in order to refer to something, you have to be causally related to it somehow" seems extremely problematic. Being causally connected to something in no way entails the belief that it is causally connected to that something. Nor can we say that having the belief that something is causally connected to something entails that that first something is causally connected to that second something. So, how can you be sure that you know what you are referring to, if one has to be causally connected to it?

Let us imagine a brain in a vat. Let us consider what that brain might be thinking. It's "world" that it perceives would be "imaginary" (well, it would be a computer program, but it would not be "real" in the sense that most people believe things are real). The person in the vat would probably not suppose that its world was merely a computer program (assuming that the program were well written).

Of course, the example is imaginary (or so everyone seems to believe), but its purpose is to show that one cannot know that what people typically believe as a result of their senses. Indeed, with the computer generated world, if the brain was put in it at birth, could involve any rules of physics that the computer programmer can imagine, or any other kinds of changes that the computer programmer can imagine. Perhaps, you are a brain in a vat, and your species is really a bunch of lizard-like things (only with 27 legs!), and the programmer thought it would be funny to make you believe you were a mammal with four limbs. Perhaps traveling faster than the speed of light is no problem at all, and the computer programmer thought it would be funny to put such an arbitrary restriction in your 'world'.

The function of the thought experiment of imagining yourself as a brain in a vat is precisely the same as the function of Descartes' "evil genius" in his Meditations on First Philosophy, though the brain in the vat is less extreme, and therefore easier for people to imagine (today, anyway).

In short, what I am suggesting is this: IF Putnam is right "that in order to refer to something, you have to be causally related to it somehow" (and I am by no means saying that he is right about this), then you have no way of knowing what you are referring to when you refer to something, unless, perhaps, you are only referring to your own sensations and thoughts.

Putnam's objection to the idea that one is a brain in a vat completely vanishes when one considers the possibility of someone else being a brain in a vat. He is just playing games with words.

And, of course, all of the above is forgetting about David Hume's analysis of causation. Bringing that to bear on this would only give Putnam more problems.

John Page

Pyrrho:

I agree on the surface of it. Do you think it helps to express the situation as "in order to perceive and therefore later to refer to something, you have to be causally related to it somehow"? The mechanism of perception is thus the causal agent/relation in how we come to know something etc.

Cheers, John

sophie

Any ideas of what a casual mental connection may be?