Are mind and body two different things, or one thing? Descartes, along with Eastern religions that view consciousness as immaterial, argue that mind and body belong to different realms, nonphysical and physical.
A big problem with this view, of course, is that it's obvious that mind and body are intimately connected. I think, "Type I think," and voila, that's what happens. If mind and body are different, how could an immaterial mind control the physical fingers that tap out letters on my keyboard?
And how is it that ingesting coffee, LSD, alcohol, or numerous other substances affects the mind, if the mind is immaterial? This is why dualism -- the notion that mind and body are different -- is rejected by almost all modern scientists.
In David Chalmers' new book, "Reality+: Virtual Worlds and the Problems of Philosophy, he addresses the mind-body problem in a chapter called "How do mind and body interact in a virtual world?" He says:
These days, Cartesian dualism is widely rejected. Most people think that our behavior is produced entirely by physical processes in the brain, and many think that the idea of interaction between physical and nonphysical processes makes no sense.
Agreed. But I enjoyed how Chalmers analyzed the two main types of simulations, pure and impure, to cast light on how dualism fares in a simulated reality.
As you can read below, in a pure simulation the mind of a being/person is simulated along with the physics that controls the simulated world. In other words, both mind and body, along with everything else in that world, is made of digital bits created by the simulation's designer.
This leaves no room for dualism, in the same way there's no room for dualism in our physical world, where mind almost certainly is the brain in action, and the brain is physical, like everything else.
But in an impure simulation, mind can be one thing, and body can be something else. This is the case with virtual reality headsets, which exist now. The virtual reality is a digital simulation, while the mind of the person wearing the headset is part of the everyday world. Hence, dualism.
Not a supernatural sort of dualism, but a dualism all the same. This allows Chalmers to say that dualism is indeed possible in an impure simulation. The passages below are from the end of the chapter, so they assume that the reader has been exposed to preceding arguments.
So if what follows seems confusing, don't be surprised. It's sort of confusing to me also, and I've read the entire chapter.
The arguments in this chapter can help us think clearly about the simulation hypothesis. We saw in chapter 2 that the hypothesis can be split into the pure simulation hypothesis, in which our cognitive system is part of the simulation, and the impure simulation hypothesis, in which it's not.
The traditional brain-in-a-vat scenario is an impure simulation, as is the situation in The Matrix. In this chapter we've mainly been focusing on impure simulations, in which the cognitive system and the physics of the virtual world are distinct.
If I accept the impure simulation hypothesis, I should accept the Cartesian dualist hypothesis that my cognitive system is nonphysical and interacting with physical systems. My mind is outside the physical space of my virtual world, and it interacts with my body, which is inside that space.
My physical world derives entirely from bits in a computer, but my mind is tied to the brain in a vat, which need not derive from bits at all.
Earlier, I argued that the simulation hypothesis leads to the it-from-bit creation hypothesis. Now we see that the impure simulation hypothesis leads to the Cartesian it-from-bit creation hypothesis: Physical systems derive from computational processes, put in place by a creator, and our cognitive systems are distinct from, and interact with, these physical systems.
In effect, the impure simulation idea is akin to combining the it-from-bit creation idea about the physical world with Cartesian dualism about the mind. By contrast, the pure simulation hypothesis leads to the non-Cartesian it-from-bit creation hypothesis. Our cognitive systems derive from physical systems, which derive from computations, which are themselves created.
I'm not suggesting that the impure simulation hypothesis is especially plausible. If you take the simulation hypothesis seriously because of the statistical argument that simulations will be common, this reasoning tends to support the pure simulation hypothesis. It will be easier to create pure simulations (just set up the simulated physics of a world and watch it go), and much harder to create impure simulations (in which you'll need separate minds to interact with the simulation).
If you need a biological brain for every impure simulation, this poses a hurdle that may limit the supply of impure simulations. As long as pure simulations can also support minds like ours, statistical reasoning suggests that it's more probable that we're in a pure simulation than an impure one.
Furthermore, insofar as we have reasonable evidence that physics forms a closed network in our world, this is evidence against the Cartesian hypothesis and against the impure simulation hypothesis, or at least against versions of these hypotheses in which the mind makes a difference in the physical world.
Still, simulation reasoning may give us reason to take Cartesian dualism more seriously than before. Cartesian dualism initially seems supernatural -- inconsistent with a naturalistic view of the world. Simulation reasoning shows us how Cartesian dualism might be entirely naturalistic, deriving from natural processes in an outer world.
Just as simulation reasoning gives us a naturalistic version of theism, it also gives us a naturalistic version of Cartesian dualism. It also helps us to overcome Princess Elisabeth's objection that a nonphysical system could not in principle interact with a physical system. The impure simulation hypothesis provides us with a model of how this interaction might work.
Is this simulation-based Cartesian dualism consistent with our scientific knowledge of the world? Where physics in concerned, the idea that physics forms a closed network is an attractive hypothesis, but it's certainly not demonstrated. Current physics suggests that there may be forces not yet discovered. It would be surprising to learn that outer-world processes occasionally affected inner-world physics inside computation-based human bodies, but it wouldn't be inconsistent with our evidence.
Where neuroscience is concerned, we know we have highly sophisticated brain processes that correlate closely with perception, thought, and action. There are versions of the impure simulation hypothesis that are consistent with all this. One somewhat extravagant version is the duplicate-brain hypothesis with a nonvirtual brain in the outer world duplicating and overriding the virtual brain in the inner world.
Less extravagant is a version in which a nonvirtual brain is connected to a semi-autonomous virtual brain, affecting it and controlling its behavior at key junctures. It's true that we have little in the way of direct evidence for this hypothesis, but we also have little evidence against it.
The impure simulation hypothesis suggests that Cartesian dualism is at least consistent with our scientific knowledge of the world. I'm not arguing that the impure simulation hypothesis is true, so I haven't provided an argument that Cartesian dualism is true. Still, simulation reasoning shows us a way in which Cartesian dualism could be true -- which is interesting in itself.