Chalmers Against Skepticism
Philosopher David Chalmers has a solution to the problem of external world skepticism. The short version: You can know that you have hands even if you ARE a brain in a vat!
1. The Matrix as Metaphysics: Imagine that you are living 1,000 years ago. You look at some water and form the belief,
Now, centuries later, scientists will discover that this substance is composed of H2O. You didn’t know that you were looking at some H2O, but does it matter? No. It just doesn’t seem like ignorance about the underlying, fundamental structure or nature of something undermines this sort of knowledge. In fact, you might have even held MISTAKEN beliefs about the underlying structure—for instance, you might have said that water is composed of tiny corpuscles that are perfectly round (that’s what makes it so fluid!). But, being mistaken about this fact doesn’t undermine your knowledge that
Imagine that you ARE a brain in a vat. You look at your digitally-rendered “hands” and form the belief, . It is very tempting to think that you lack knowledge in this case. Your belief is simply mistaken. You do not have hands.
But, Chalmers argues that, even if you are a brain in a vat, you DO have hands. If you look down, and see and feel hands, then you have them! They might be composed of earth/air/fire/water, or atoms, or superstrings, or zeroes and ones. Ultimately, that doesn’t matter. You don’t need to know anything about their underlying fundamental structure in order to know that you have them—just like you don’t need to know anything about H2O in order to know that water exists.
So, ultimately, the Matrix Hypothesis is not a skeptical hypothesis, but rather a metaphysical one about reality, its fundamental structure, and our relation to it.
2. Three Non-Skeptical Hypotheses: Chalmers notes that his proposal is really just the combination of three hypotheses, none of which are skeptical:
The Creation Hypothesis: There exists some creator of our reality which is in some sense “outside” of this reality.
This is not a skeptical hypothesis. It is much like the belief in God, and we would not say that theists are external-world skeptics. Alternatively, many physicists speculate that our entire universe is just one among many, or that ours is entirely inside of some black hole that exists in “the next universe up”.
The Computational Hypothesis: Reality, at its most fundamental level, is ultimately composed of bits (of information; i.e., zeroes and ones).
This is not a skeptical hypothesis. There are many competing views about the fundamental structure of reality, and the leading view is equally bizarre. Physicists tell us that everything is ultimately composed of vibrating strings—whatever those are; and that seemingly solid objects like tables and trees are really mostly empty space, not solid at all! If this is not a skeptical hypothesis, then neither is Chalmers’ hypothesis.
The Mind-Body Hypothesis: Our minds are located outside of this reality— that is, outside of this space-time continuum—but interact with things in this space-time. Consider: If I am a brain in a vat, then my brain is elsewhere, unobservable, imperceivable, and not a part of this reality. And yet, it interacts with this reality by having conscious experiences.
This is not a skeptical hypothesis either. Most of the people who have ever existed have held this view. For, it is much like the view that our mind is located in an immaterial soul. Much like God, souls are typically thought to be outside of space-time, yet interact with it. (Phil. & Technology students: More on this later.)
Conclusion: If none of its components result in skepticism about the external world, then the combination doesn’t either. So, even if we ARE brains in vats, we should not endorse skepticism about the external world!
3. Objections: Most readers will probably still have these lingering worries:
(a) It seems like the following are all FALSE when uttered by a brain in a vat:
I am outside in the sun I am in Tucson I have hair
Reply: Chalmers believes that our terms refer to whatever it is that we’re referring to when we point to them. If I look in a mirror and see hair, then my term ‘hair’ refers to THAT stuff, whatever it is. If I visit Tucson, then my term ‘Tucson’ refers to THAT place, whatever it is. It just turns out that someone living in a simulation has terms that refer to what we might call “virtual hair” or “virtual Tucson” and so on. Sure, if we are looking in from OUTSIDE a simulation at some beings who are INSIDE of one, they will seem mistaken. For then, OUR term ‘hair’ would refer to physical hair rather than virtual hair. But, that is only because OUR terms would refer differently than theirs. Simply put: In a physical world, real hands are made of atoms (or strings, or whatever). In a simulation, real hands are made of bits.
(b) How about this one? I have friends
Reply: It is possible that you have friends, even if you are in a simulation. If either (a) there are other envatted brains in the simulation along with you, or (b) your friends are purely computational, but nevertheless conscious artificial intelligences, then your friends are real. Now, we can’t be SURE of this, but this is just the “problem of other minds”, which is a problem even for beings who are NOT in simulations.
(c) But, to believe in the external world is to believe in physical objects, not virtual objects. Simulation is not reality! So, if I believe that there are real things, and I turn out to be in a simulation, then I am wrong about almost everything!
Reply: Once again, Chalmers believes that you are NOT mistaken about most things. Hands and hair and tables and trees are all REAL in a simulation. Only, their fundamental structure is different than most people think. So, if you believe some abstract proposition like,
Now, if you insist something like, “By terms like ‘hands’, I am referring to physical objects that are definitely NOT composed of computational bits of information”, and you are in a simulation, then I suppose it turns out that you are wrong about a lot of things. But, do we really have pre-suppositions about the fundamental nature of reality built into our ordinary terms for physical objects? If so, then, when Plato believed he was drinking water, he was wrong (because he had built a mistaken assumption about its fundamental nature into the term—namely, that it was one of the four elements). But, that seems odd, right?
4. Conclusion: Chalmers puts it this way:
“I suggested before that it is not out of the question that we really are in a matrix. One might have thought that this is a worrying conclusion. But if I am right, it is not nearly as worrying as one might have thought. Even if we are in such a matrix, our world is no less real than we thought it was. It just has a surprising fundamental nature.”
[For a great synopsis of Chalmers’ solution, see Jennifer Nagel’s video here.]
[We can also explore whether we’d have knowledge in OTHER skeptical scenarios; e.g.: What if I grew up in the physical world, and was only envatted this morning? In that case, most of my beliefs about the present WOULD be false; though beliefs about my past would still be mostly true. What if I’m a BIV, but the universe only began to exist moments ago? Then, your beliefs about the present are mostly true; and about the past, mostly false.]