Brain In A Vat & Leibniz's Identity & Indiscernibility
Brain in a vat
Identity & Indiscernibility
I'm confident every knows about the brain-in-a-vat scenario.
Leibniz's take on identity and indiscernibility is as follows:
1. Indiscernibility of Identicals: If x is identical to y then whatever is true of x is also true of y
2. Identity of Indiscernibles: If whatever is true of x is also true of y then x is identical to y
Note 1: As far as Leibniz is concerned if x is "identical" to y then x and y are the exact same thing; mathematically speaking, there's only one thing and not two.
Note 2: There seems to be no issue about 1. Indiscernibility of Identicals but some debate on 2. Identity of Indiscernibles which is what I wish to discuss.
That out of the way, consider the fact that life as a brain in a vat is indiscernible from life as an actual human being. If so, it follows, from 2. identity of indiscernibles, that life as a brain in a vat is identical to life as an actual human being in the sense that they're the exact same thing.
In short, things that are indiscernible from our perspective may not be actually identical i.e. could be vastly different from another perspective.
What do you make of that?
Identity & Indiscernibility
I'm confident every knows about the brain-in-a-vat scenario.
Leibniz's take on identity and indiscernibility is as follows:
1. Indiscernibility of Identicals: If x is identical to y then whatever is true of x is also true of y
2. Identity of Indiscernibles: If whatever is true of x is also true of y then x is identical to y
Note 1: As far as Leibniz is concerned if x is "identical" to y then x and y are the exact same thing; mathematically speaking, there's only one thing and not two.
Note 2: There seems to be no issue about 1. Indiscernibility of Identicals but some debate on 2. Identity of Indiscernibles which is what I wish to discuss.
That out of the way, consider the fact that life as a brain in a vat is indiscernible from life as an actual human being. If so, it follows, from 2. identity of indiscernibles, that life as a brain in a vat is identical to life as an actual human being in the sense that they're the exact same thing.
In short, things that are indiscernible from our perspective may not be actually identical i.e. could be vastly different from another perspective.
What do you make of that?
Comments (33)
So being a brain in a vat is in principle discernible from being a real normal person, so they are not in fact identical.
Unless you describe life as an actual human being as being a brain in the vat, then the two are not the same thing. We generally describe life as an actual human being as something other than being a brain in a vat, so we do not have this problem. It's only a problem if you think that life as a human being is nothing other than being a brain in a vat.
Firstly, this world and this life we're living are such that we can't discern whether we're actual human beings or brains in vats. Call the experience of this world X.
A you correctly pointed out, to know whether we're brains in vats (or actual human beings) we need information.
There are two things to consider:
1. The gateway for information necessary to know we're brains in vats is our senses
2. Our senses are totally unreliable (can be manipulated) to discern our true status. After all isn't this precisely why we're unable to distinguish whether we're brains in vats or actual human beings?
Ergo, we can never know, for sure, that we're actually brains in vats.
I'm curoious though. What would the information that could help us know we're brains in vats look like?
Quoting Metaphysician Undercover
Can you tell the difference between being a brain in a vat and an actual human being from our vantage point?
The fact that you or I, both of us, or a whole bunch of people, cannot discern one thing from another thing, does not necessitate the conclusion that the two are indiscernible. Being indiscernible, which means that it is impossible to discern, is not relative to the human capacity for discerning.
A figure could appear out of thin air and tell you so, and demonstrate anything else you might want to see as evidence... like say, a feed from outside the vat, showing your brain being prodded or whatever, and the corresponding changes in your perception of reality.
But more generally speaking, if there is any way for the world outside the vat to influence our perceptions in the vat, we have some way of getting information from outside the vat. And if the things we do in the vat have any influence on the world outside the vat, then we can do something in here to provoke responses out there that then have some effect on us in here.
The exact nature of what those interactions across the vat boundaries look like depends on how exact the vat is set up, which is one of the things we would want to figured out by trying to provoke reactions out there. If so far nothing we do in here provokes any reactions out there that have observable consequences in here, then so far as we can tell we are not brains in vats. But if we are brains in vats, then in principle some things we do in here will have some consequences out there, some of which in turn will have some consequences in here, though which we could eventually tell.
That's a contradiction. I think you need to give another look at the issue.
Quoting Pfhorrest
That is known - we're a brain in a vat
What's crucial is that we can't rely on our senses. So, no amount of information through them will ever be sufficient to let us know anything about our status as brains in vats or actual human beings.
That’s begging the question.
The brain in a vat scenario tries to establish THAT we can’t rely on our senses. My rebuttal to it proceeds from the assumption that we can.
:chin: The brain in a vat thought experiment is to show that reality could be a simulation based on the fact that our senses are unreliable. I think you've got it backwards.
Huh? The fact that I cannot discern the difference between two things, does not necessitate the conclusion that the difference is indiscernible.
Do you recognize the difference between "I cannot do X", and "X cannot be done"?
Pretty sure you’ve got it backwards here. It’s an update on the Evil Demon: both are trying to show that the senses are unreliable because they could be being fed false input, in a magical illusion or virtual reality.
I’m saying that we could in principle discern that we were being deceiving, eventually. These far-fetched scenarios just make that much harder.
You're mistaken. Read the links. Descartes conclusion isn't that our senses are fallible but that reality could be an illusion (from senses beimg fallible) To show our senses are fallible we'd have to use hallucinations or the like as evidence.
Quoting Metaphysician Undercover
As I mentioned earlier, all information flows into our brains/minds through our senses. Our senses being fallible, it's impossible to know whether what we see as discernible differences are actually differences. Presumably all beings are functionally similar to us.We cannot discern X implies that X cannot be done.
I have, and also, I've studied this professionally for years, including a term entirely about Descartes.
Descartes is trying to show that we can doubt the things our senses show us, and thus that what we think we know about reality might not be so. To show this he gives a lot of examples and hypotheticals about the senses being deceived, including ultimately the Evil Genius scenario in which all of the senses have always been fed entirely false information. The Brain in a Vat is an updated version of that same latter scenario. Its thesis is that we can't trust what our senses tell us about reality, because someone could be feeding our senses completely false information all the time.
I'm saying, translated back to the Evil Genius version of it for clarity here: maybe we can't directly tell anything about the external world, if there is one, but we can tell something about the Evil Genius himself, based on how he reacts (in the form of the false experiences he sends us) to things we do; and if there is a world that Evil Genius is in, like if he is actually a scientist experimenting on our brain in his vat, we can in principle tell something about it through his reactions to it. Or more generally, on how that external world affects our brains, even being in the vat as they are, especially in response to things we do, even being brains in vats as we are. Because if there is absolutely no communication between our brains and the world outside the vat, no signals at all being sent between them, then we are completely causally isolated from each other, and in effect are not in the same universe at all. If we are not thus isolated -- like, if people in the outside world could poke our brains with sticks, or shoot them with lasers, or see them because light can bounce back and forth -- then there is some channel of communication between the brain and the world outside the vat, that in principle can somehow be exploited to tell information about that world. The vat just makes it a lot harder than it otherwise would be if we had normal eyes etc.
But hey, we can now watch objects that emit and reflect no light at all (black holes) that are hidden forever beyond a veil of primordial glow from the big bang (the CMB), so far away from us that we will never be able to send a signal back to them, thanks to gravitational wave detectors. And there are tricks to get information off of computers in sealed rooms that aren't connected to any network, or to use software to induce physical failures in hardware at the quantum level and so enable software exploits to break hardware security. If there is any possibility of interaction between two systems, somehow it is possible to send and receive information between them.
Firstly, we can't deny the fact that it's impossible (for us, according to you) to tell whether we're brains in vats or actual human beings. This is because there's what I call the middle man, our sensory apparatus that can be manipulated, perhaps by electrically stimulating it, to give us experiences of things without the things actually existing - basically, what we think is reality could be simply a simulation. If so, we being brains in vats enters into the realm of possibility.
Given this, we must realize that anything that has been touched by the middle man is unreliable. The problem, as I see it, is that there's no way of getting rid of the middle man - there's no way for us to directly sense beyond what the middle man let's us sense.
Analogous to a person locked up in a room with the only access to the world outside being a single monitor on a desk, we're utterly helpless. Being so, no amount of information, since it has to pass through the (corrupt) middle man will ever be sufficient for us to infer the true status of our existence as brains in vats or not.
One thing I want to run by you for your inspection is this: is it plausible to say that, if and when the experimenters provide us, brains in vats, information that'll let us know that we are brains in vats, this could be an actual human being suffering from hallucinations?
This is incorrect, because a being with superior capacities might be able to do X. One cannot conclude from one's own inability to do something, that it is impossible to do that something. "You can't do it" represents your relation with the object. "I can't do it" represents my relation with the object. "We can't do it" represents our relation with the object. "It can't be done" represents the object in an absolute way, in relation to everything else.
[math] \forall x \forall y: \forall P (K(P(x)) \leftrightarrow K(P(y))) \rightarrow x=y [/math] where [math]K[/math] is the knowledge operator.
There is a property P that readily distinguishes vat-world and not-vat-world, namely whether that entity is part of a simulation of a brain in the vat or not. The ability to know whether something is or is not a simulation is different from whether that something is a simulation. If you want to feed that kind of claim into the identity of indiscernibles, you'd need to establish:
[math]\forall P \forall x \forall y (K(P(x)) \leftrightarrow K(P(y))) \leftrightarrow (P(x) \leftrightarrow P(y))[/math]
which has [math]K(P(x)) \leftrightarrow P(x)[/math] as a consequence - and you end up with both infallibilism and that all truths are known, both theorems of that assumption. Not a good situation.
Yes, I get what you mean - "a being with superior capacities" could discern what to us, all of us, is indiscernible.
Firstly, what would the structure of such a being look like? If it's structure resembles ours, specifically if it too depends on some sensory apparatus to interact with what it thinks is reality, then it's back to square one - it can't draw any definitive conclusions from what its sensory apparatus feeds it. Basically, it can't discern its own status as an independent, external observer privy to information we're not.
Secondly, for the above reason it must be that if we can't discern then it can't be discerned, assuming what was said in the previous paragraph.
This is not relevant. Leibniz does not qualify "indiscernible" with "to us", or with reference to any other type of being with specific capacities for discerning. So we must acknowledge that "indiscernible" was being used without any such qualification, and therefore interpret it in an absolute sense, as it was used.
Not relevant :chin: ? Then why is it relevant to Descartes' demon and brain in a vat thought experiments? You'd have to say that these thought experiments are completely meaningless if the sensory apparatus that conveys info/data is, as you say, "not relevant". In fact the sensory apparatus, that it can be manipulated, is the cornerstone of these arguments/thought experiments.
This might be the cornerstone of Descartes argument, but not Leibniz' principle. The identity of indiscernibles is a logical principle, not dependent on sensory apparatus. You are just conflating two distinct things in an incorrect way.
I'm applying Leibniz to Descartes. There's nothing wrong with that, right?
Imagine a being discerns whether we're brains in vats or actual humans. Imagine also that this being is built like us and has a sensory apparatus that feeds it the information required to tell what we actually are. However, since this being too could be a brain in a vat for the same reason it's possible that we are or, if not, it could be an actual human being experiencing a complex hallucination.
The premise of your proposal is wrong. The brain in a vat scenario implies necessarily a 'person' who constructed the brain in a vat. This 'person' would discern the difference. So it is impossible that the two are indiscernible.
Ok. There's this person, call him X, who you say can discern whether we are brains in vats or actual human beings. However, it's still possible that X is one of us, a brain in a vat being fed false information or an actual human being having a hallucinatory episode.
I agree. I think @Pfhorrest made that amply clear and even @Metaphysician Undercover's thoughts align with this sentiment.
However, Descartes' and Gilbert Harman's (brain-in-vats) argument turns on precisely the [I]"ability to know"[/i] the difference between the two worlds. Of course there's a discernible difference between being brains in vats and actual humam beings, it's self-explanatory, but the problem is that we can't know the difference.
Except we can, in principle; it’s just very very hard to get at that information.
I don't think we can for the reason that there must exist, as @Metaphysician Undercover posited, a being, call it X, that gets its hands on the information that can help it make the distinction but if X is anything like us the information must pass through a set-up of sensory apparatuses and then we're back to square one - this being could be just another one of us being fed false information of it could be an actual human being suffering from hallucinations.
Say, for example, that a human figure with apparent omnipotence appears to you out of thin air, tells you you’ve been a brain in a vat experiment, but the experiment is over now and they’re going to put your brain in a clone body, and let you join the real world. After discussing the whole thing at length you have a discontinuity in your experience and wake up in a different body in a different world. You live in the world for decades, a long fruitful life, but your clone body ages, and as you are on your death bed you are offered a chance to upload into a virtual reality that your brain in a vat experiment helped enable. You agree, and wake up in a beautiful world, in a young perfect body, and you can do stuff like fly and shoot fireballs from your hands with VR magic. You can also communicate with people’s in the world you’ve been experiencing for decades, and those people confirm that you are an uploaded mind in VR now. You continue living like that for thousands of years, keeping up on the news in the outside world too while you live in your virtual paradise.
What is more likely, which are you going to believe — that that experience is reflective of actual reality, and you really were a brain in a vat, or that you just had a millennia-long uninterrupted hallucination, or that there never was any reality to begin with, or something?
That's sweeping the problem under the rug. You haven't dealt with the problem but decided to ignore it.
Quoting Pfhorrest
Firstly, I don't think we can pin down a probability on which is more likely. I maybe wrong though and would like to hear your arguments if you have any. The heart of the issue is we're not certain which of the two scenarios is true.
No, I’ve concluded (like many before me) that it’s not a problem. “You don’t have good enough reason to think that” cannot be good enough reason to think otherwise, otherwise we end up in absurdity, forever rejecting everything, which is a great way to guarantee you never form correct beliefs. Critical rationalism is the only rational alternative.
No, the brain in the vat premise implies that this is not possible. For us to be brains in vats, it is implied that someone created this situation. It is impossible that the person who created it was just hallucinating or else there would not be us, as brains in vats. You can understand this situation with dreams. It is possible that I am in a dream right now, but it is impossible that I am in someone else's dream.
Quoting TheMadFool
It's not a matter of this person getting hands on the information, it's a matter of this person necessarily all ready knowing the difference (having the information) as prerequisite for the brain in vat scenario, being the intentional creator of the conditions. So you need to ask whether it's possible for the brain in vat scenario to exist without a creator. But the description, as brain in vat, implies that there is a creator. You could go to some other description, like "simulation hypothesis", but that also implies a creator.
I think it would be very difficult to come up with a compatible theory, which did not require a creator to create the proposed scenario. And if your scenario requires a creator, the creator has the necessary information. Also take notice that this information need not pass through sensory apparatus. When we create something, the idea for that thing, the plan, exists prior to the physical existence of that thing. So the creator dreams up the idea, figures out how to put the plan into action, and then does so, without ever having sensed the thing which is being created. An omniscient being (one which cannot be mistaken) can set up a time delayed scenario, leave the scene, and have all the information to know about what is going on in that scenario without ever sensing it.
I'm not saying that just because there's no good reason to think X it's ok to think Y or not X. All I'm saying is there's no good reason to think X.
Consider the following three scenarios:
1. I'm the evil genius, call me X, who's got everybody as brains in vats in my lab. I visit my lab everyday and make sure everything's functioning smoothly - the nutrient bath and the supercomputer generating the simulation are at the top of my list of priorities.
2. I'm not the evil genius, X, but actually a brain in a vat being fed false information that I am X.
3. I'm an actual human being hallucinating the whole thing (that I'm X).
All the data that goes into letting me know which of the three scenarios above is true comes through my senses and my senses (like everybody's senses) as we already know, can't be trusted. Ergo, I can't know if I'm the evil genius X or an actual human hallucinating that I'm X or a brain in a vat being fed a simulation that I'm X.
Basically, these three scenarios are indiscernible and this'll be true no matter what you do to wriggle out of the situation.
No they are not the same, by the very fact that they are described with three very distinct descriptions. If you cannot see the difference between these three distinct descriptions, I'm tired of explaining it to you.
Yes, I agree and I admitted to that fact - the 3 scenarios do differ but the problem and point is they can't be discerned as so. There's a difference, yes, but this difference is not knowable.