Direct Realism and the Brain-in-a-Vat Argument
fakenous.net
fakenous.net
Except that drugs and blunt trauma have direct impact on our experience. So a BIV would need some additional poking and prodding to mimic what would happen to the simulated brain. What happened to BIV's who got simulated lobotomies, for example?
And if we posit that the simulation adjusts the actual brain in the vat accordingly then it becomes the general full-simulation argument, not BIV.
Modelling the BIV directly after the brains we know only serves as a justification in the thought-experiment that a BIV might reasonably exist.
But actually the BIV does not need to be of similar character or composition than the simulated brains that a BIV can observe in its observable simulated world. Even if a simulated lobotomy would be performed under simulated general anesthesia, there is no reason to assume that the BIV itself would be completely inert during that time, the consciousness might well be a compartment of the BIV with other compartments tracking e.g. changes in the simulated body.
This is not yet a full-simulation argument as the individuum itself is not yet part of the simulated universe, the simulation is still an external stimulus to the BIV system.
The important takeaway here is that in a fully simulated universe, the concept of an objective "reality" is still intact, and generalized to nested realities. With a BIV, the perceived reality is always required to be entirely subjective. If the stimulus machine of a BIV is turned off, the individuum is still intact (and probably still wondering what the hell happened as it's suddenly floating in unperceivable nothingness), if a full-simulation is turned off, all observers (except those in the "higher" reality) cease to exist immediately.
Maybe I'm not supposed to take the premise that human brains can exist as QCD-physical objects? In that case it seems more like the dualistic belief that a spirit or supernatural entity puppets the physical body around and interprets its interactions with the physical world. (Which runs into the same problem of dramatic effects physical changes to brains have)
So in the example of turning off the simulation and leaving the BIV running you either turn off the effects of receiving oxygen through the bloodstream in the same way choking or drowning produces, or you break the simulation of reality to artificially keep the BIV running despite conditions that would have stopped it if the simulated brain was removed from the simulated body accurately. How does disconnecting a BIV work, precisely, when e.g. homeostasis is enough to produce varying effects on conscious experience? Neurons get tired after firing and require nutrients to recharge. Those nutrients exist in the physical/simulated world and if they behaved even slightly differently the neural firing patterns would differ and the BIV and physical human brain would diverge. When the simulated nutrients go away does the BIV just pretend a baseline digestive, endocrine, cardiovascular, and lymphatic system still exist and fake everything? If so, then the BIV doesn't exist without regard to the turned-off simulation, it gets copy-pasted into a simplified simulation of whatever minimal physical apparatus would keep a physical human brain alive in a jar.
The thing is, though, there is no requirement for it to be accurate, it merely has to be fed simulated stimuli that are consistent enough that the mind of the BIV does not deduce the reality of its situation. For example, the simulation of banging one's head against a wall could be somewhat or even quite inaccurate without the BIV being able to tell that it is, even if it chooses to bang its simulated head against a simulated wall.
As an aside, there's a related thought experiment about gradually replacing the neurons in a person's brain with artificial neurons that behave identically. The question is "at what threshold is the brain a different person" and my answer is never. If the artificial neurons behave identically then the person doesn't change, but their substrate does. That would be a method to construct a BIV, but the artificial neurons would need to respond to their local biochemical environment in the same way as original neurons. It would certainly be possible to make these artificial neurons immune to physical shock or cosmic rays but this would change the internal experience of the person; they would stop being vulnerable to some forms of physical trauma, some drugs, and some physiological states. The person would notice the change of becoming a BIV, because their experience would be changing at the extremes where it matters that they are physically embedded in a dangerous environment. If the BIV was constructed "outside the simulation" with an artificial biochemical environment they would notice an even bigger shift in perception, e.g. caffeine and other drugs no longer working as expected.
What you are thinking of seems to me to be more like Bostrom's Simulation Hypothesis[1]. Chalmers, in his new book, "Reality+', argues that there's no way to be sure we are not simulations. I don't often agree with Chalmers, but I think he is right here, and, furthermore, the simulated universe does not have to be much like the world running it, it "merely" has to be self-consistent enough that any conscious entities in it cannot deduce that they are simulated.
Here's an entertaining short story on the topic: https://qntm.org/responsibility
[1] https://www.simulation-argument.com/
Bostrom was far from the first person to hypothesize it, but it got attention from him being a prominent philosopher who based a paper on it.
For the BIV to not know that it's connected to a simulation, the simulation must be physically accurate. To be physically accurate, the actual brain in the vat must be simulated as if it were embodied in the simulation so that the proper and accurate feedback can be presented to it through the interface that attaches it to the simulation. Completely ignoring the physical embodiment of brains leads to dualism. Laggy, incomplete, and inaccurate simulation will cause the brain to feel disconnected from what it thought was reality.
Contrast BIV with "a magic spell could make a person believe they are in the real world, but actually they are not." and see if there is any more or less explanatory power in the phrasing. Connecting a brain (how) to a simulation (of the world plus which parts of the brain?) so that it believes (how, why) that it is in the real world requires explaining the how and why and what without magic.
Contrast BIV with dreaming where it is often pretty easy to tell that we're in a dream, or when we can't tell consciously that we are in a dream it still feels different when we remember it later. Dreams that are very hard to tell from reality are very accurate is my claim.
Contrast BIV with the history of souls, spirits, and other supernatural explanations where over time we have determined that physical brains are what give rise to our conscious experience via a host of physical evidence and experimentation. That process of scientific discovery is precisely what would require perfectly accurate simulation of the real brain by a BIV+simulator otherwise science would reach the (correct) opposite conclusion that our BIV-experience happens outside of the physical world.
EDIT: and finally, if the simulation is accurate enough then the brain in the vat is extraneous. The conscience experience will (also) be happening within the simulated brain, where the feeling of being embodied in the world will be accurate. A BIV in this case is simply a physical duplication of another brain.
When you say an accurate simulation is indistinguishable from reality, we need to be careful about what we mean by 'reality' here. The reality here is that the BIV is a simulation, so unless the BIV knows this, its experiences are not reality.
> For the BIV to not know that it's connected to a simulation, the simulation must be physically accurate.
Why? It would be sufficient, but why would it be necessary? The BIV does not know what reality is like, and nor does it know what reality is like for those who put it in the vat. I imagine that its neural architecture has been shaped by evolution to preconfigure it to comprehend a world like ours, but we can tell that exact fidelity is not necessary because people with various congenital or neonatal sense-limiting pathologies still make very good sense of the world (Helen Keller is the go-to example.)
> If the simulation is accurate enough then the brain in the vat is extraneous.
For us, that is probably true, but there are philosophers and scientists who think there is something special about brains that makes them impossible to simulate, and so presumably would see a difference here.
So is the important part of the question whether reality is being modified by a man in the middle? You end up exactly where you are already, having to answer the same questions about where you are in Plato's cave, so unless you have evidence to think you're in a simulation, the simplest explanation is that there's no filter between you and reality except the limits of your senses and cognitive capacity.
This is the same argument about living in the matrix. You can't assume that the option of us not being brains in vats is available. You'd have to explain what a brain not in a vat would look like - something entirely made of computronium, in a configuration radically different than our hodgepodge evolved meat suits look like. It's more likely that we're simulated and tricked to think we have brains and bodies than for us to be physically different, and stuck in a Matrix all unaware.
I'll stick with the simplest explanation that satisfies all available evidence. We're all brains in bone vats riding around meat suits for adventure and exploration.