Brains (or Hands) in Vats

Tristan Haze over at Sprachlogik wrote this post about a particular argument relating to being a Brain in a Vat (BIV) a while ago. I started to write a comment on it this morning, but it got slightly too long, so here we are.

I have to agree that much ink has been spent on the following kind of argument:

1. If you’re a brain in a vat then you don’t have hands
2. You don’t know that you’re not a brain in a vat
3. Therefore you don’t know that you have hands

Haze argues that the there is good reason to not accept (1). Essentially, he claims, there is a sense in which if you were a BIV, that hand-talk still expresses a proposition. Despite what Putnam said, even if you were a BIV, ‘hands’ still means something.

I don’t really want to get into Putnam today, but as a defender of a kind-of causal theory of reference, I would agree for slightly different reasons. Meaning, for a word like ‘hands’ comes from the causal chain of use and it would not really matter if the chain were partly (or even entirely) in a simulated environment.

What I was interested in, and was happy to see that Haze acknowledged, was that knowing that her have hands says nothing either way about whether or not we are living in a simulation or not.

Since premise (1) isn’t unambiguously true, the modified argument ends up something like this:

1. If you’re a brain in a vat then you have hands in a different way than if you weren’t a brain in a vat.
2. You don’t know that you’re not a brain in a vat
3. Therefore you don’t know that you have ‘real’ hands or simulated hands that are, for all intents and purposes, indistinguishable from ‘real’ hands.

Is the conclusion worth worrying about? For everyday purposes, probably not, since the only doubt you have about your hands is unrelated to the everyday experience of your hands. Imagine  someone in a Matrix-style simulation, whose simulated body has no hands, while their real body still has them (even if, as in the movie, they don’t actually use them). Would this person be particularly comforted to be told that it’s OK because they ‘really’ have hands? I think not.

My conclusion indicates that I’ve assumed the simulation to be perfect in the sense that (unlike Neo’s experience of the Matrix) there is nothing in what we perceive  or experience that gives us reason to think that the world around us is not what it seems. For those not familiar with BIV and deceiving demon scenarios, this is normal – we would hardly worry about whether or not we were in a simulation if we could tell the difference between it and reality.

What is important to note is this: you can’t perceive your way out of a perfect simulation.  “But I have hands!” you cry, whilst gesturing dramatically. Yes, you perceive and experience your hands, but since the problem is trusting one’s perceptions, this doesn’t tell us much either way.

Can you reason your way out of the vat? I don’t have a definite opinion. But at this point, I suspect not.