BIV was meant to undermine realism
Hilary Putnam devised the thought experiment to show that metaphysical realism was incoherent, not that we could actually be BIVs.
According to Putnam, metaphysical realism commits you to the following two things:
1. The possibility of radical skepticism
2. Semantic externalism
With one, it's possible that the actual reality of the world is that we're envatted brains being fed fake sensory impressions about the world. Two is based on the claim that metaphysical realists are committed to the correspondence theory of truth, where propositions refer to mind-independent states of fairs in the world. Another way of putting this is that meaning is in the world, not the head of the speaker.
The incoherence of holding both is as follows. A BIV says the following proposition:
"I'm a brain in a vat."
But according to semantic externalism, a BIV would actually be referring to the fake sensory impressions it's being fed of brains and vats and not the mind-independent brain in a vat. Therefore, the proposition is necessarily false. A BIV cannot truthfully say it's a BIV!
However, number one means that it could be a BIV. This leads to incoherence. I thought it was interesting that was Putnam's intent, but everyone who hears about brains in vats likes to argue whether we could actually be envatted.
Putnam was arguing for anti-realism with the BIV thought experiment, and other arguments he made, such as the model-theoretic argument.
According to Putnam, metaphysical realism commits you to the following two things:
1. The possibility of radical skepticism
2. Semantic externalism
With one, it's possible that the actual reality of the world is that we're envatted brains being fed fake sensory impressions about the world. Two is based on the claim that metaphysical realists are committed to the correspondence theory of truth, where propositions refer to mind-independent states of fairs in the world. Another way of putting this is that meaning is in the world, not the head of the speaker.
The incoherence of holding both is as follows. A BIV says the following proposition:
"I'm a brain in a vat."
But according to semantic externalism, a BIV would actually be referring to the fake sensory impressions it's being fed of brains and vats and not the mind-independent brain in a vat. Therefore, the proposition is necessarily false. A BIV cannot truthfully say it's a BIV!
However, number one means that it could be a BIV. This leads to incoherence. I thought it was interesting that was Putnam's intent, but everyone who hears about brains in vats likes to argue whether we could actually be envatted.
Putnam was arguing for anti-realism with the BIV thought experiment, and other arguments he made, such as the model-theoretic argument.
Comments (114)
I suppose if you could show that we can't be brains in a vat even if metaphysical realism is the case then you can argue that realism doesn't entail radical skepticism, and so refute Putnam's argument.
But, yes, from what I've seen people argue on here, there does seem to be a misunderstanding of Putnam's intention. He's not saying that we could be brains in a vat; he's saying that we can't be, and so therefore metaphysical realism is false.
Maybe so, but t's hard to see how metaphysical realism doesn't entail the possibility of some form of radical skepticism, even though I am a realist.
Even if BIVs aren't tenable, a Matrix, Star Trek holodeck or Boltzmann Brain scenario might be. You'd have to show that such a simulation isn't physically possible, and everything I've read leads me to believe that it is possible to compute a convingly realistic world. And if you're born into that world, you wouldn't know what was unrealistic anyway (relative to the actual physical world).
One possible answer to the Fermi Paradox is that advanced aliens are feeding us a simulated universe that looks empty. In that case, we'd only be wrong about the wider universe, not matters inside the solar system (extra solar light would be simulated to fool us).
I don't think even that would work, as it could be that the "real" world operates according to different physical laws, and the ones we're familiar with are only the laws of our simulation.
Like maybe in the real world P=NP, but not our simulation?
But it seems like if you could show that it's impossible to construct a simulation in our world, then the basis for the simulation argument is undermined (because what do you mean by our world being simulated?). However, that sounds related to Putnam's argument against being able to make a radically skeptical realist assertion.
I believe the hypothesis trades on logical possibility, not physical possibility.
I suppose the best you could show is that if a simulation is impossible in our world then our world can't be a like-for-like simulation.
Right, but it the hypothesis also needs to make sense. So you could argue that realists cannot coherently say our world is a simulation if building such a simulation in our world is impossible, because we have no way to refer to the states of affairs of the real world in which in our simulation lives.
Sure, but making sense doesn't depend on obeying physical laws. The notion of defying gravity à la Superman is coherent, even if not able to be done.
If the simulation was computed with floating point arithmetic, circles would be square-able through straightedge and compass, all numbers would be computable, irrational numbers would eventually having a repeating pattern of digits in their decimal representations and so on. Simulated universe => Computable universe => this. Not this => not computable universe => not simulated universe. One's modus ponens is another's tollens.*
The first objection would be that 'numbers are not in an analogous category to physical objects in the simulated universe' - but why would it matter? They would have to be represented with adequate precision to stop the squaring of the circle - which is infinite precision - and is a constraint placed on the physical operations we are capable of doing with compass and straightedge by their innate, 'virtual', properties. We don't live in the kind of universe where a circle is square-able with compass and straight edge - so we don't live in a simulation with finite precision.
Considering that the computer would have to be infinitely large (physically, not purely mathematically) to store every digit of Pi - to set it to the true value we have in this universe - I think we can rule out that we live in an infinitely large computer, too. So we don't live in a finitary or infinte computer simulation. Eliminate the disjunction and break free in either case (P or not-P is hard to dodge).
Can you spell out why it wouldn't work for the brain-in-a-vat one? I really don't care about the demon.
No, it needs to be high enough to fool human technology and math. That's why some people have speculated that physics might be able to show we're in a simulation.
So the idea is replace all experiences with exactly equivalent substitutes which come solely from stimulating the brain?
Presumably this is automated to be real time. I can't conceive of a way of doing this, nor do I think it's possible. All that changes is that we are no longer software, but we are being stimulated by software in a manner which produces equivalent lives; in other words, it's a more convoluted way of doing exactly the same thing.
It's more that the 'simulated universe' must have square-able circles in it. This isn't a perceptual property, it's a relational property of circles, squares and the transcendental nature of Pi.
Actually, I don't understand this. Assuming we live in the real world, how is it that we determine the digits of Pi? Don't we have some computer running the relevant calculations? So far it hasn't provided a repeating pattern of digits. Why can't a simulated computer run the same calculations?
The human technology is part of the simulation, too. I'm not sure what you mean about fooling the math.
Well, the brain isn't very fast compared to computers. It takes a quarter of a second or so to think a thought or recognize an object. Responding to a startling sound is much faster (50 milliseconds), but it's still slow compared to computers which can operate on nanosecond time frames.
The fact that we can compute PI to huge numbers of places means the simulation has to be able to do that. And that we can devise physics experiments that can measure the amount of time it takes light to cross the length of an atom means the simulation has to be able to accommodate that.
That requires way, way more compute power than fooling the naked eye.
It isn't a matter of producing the correct digits. Pi is a computable number. It's this property, it is a real consequence of the fact that Pi is transcendental. It literally puts a constraint on what is possible using a compass and straightedge.
The speed we think and act probably puts some bounds on their informational content. But the speed alone tells us nothing about how hard it would be to simulate human experience, or to provide real-time equivalent stimulations to a brain (assuming the brain can indeed be stimulated to produce these things without sensorimotor constraints and the nervous system at large... which is unlikely).
So why is that a problem? The simulation runs the same program that we run to calculate the value of Pi.
Quoting Marchesk
The simulation only needs to simulate what we see. What we see is the device and its human-readable output.
Quoting fdrake
I don't understand why this would be a problem for the simulation. If our computers can calculate Pi without ever repeating digits then the simulation can calculate Pi without ever repeating digits.
The computer needs to be able to compute the result of any experiment we might think to devise in a convincing fashion. That goes way beyond simply fooling the human visual system.
That might be so for BIVs, but it won't be so for holodecks, since holodecks feed our sensory organs instead of our brains. Imagine the ST universe where a whole civilization lives inside a large holodeck. And that leads to another possible answer to the Fermi Paradox.
All advanced civilizations end up inside simulations, because they're far more appealing than exploring space.
The computer could produce an arbitrarily accurate approximation of Pi, given sufficient computing time. The computer would not have infinite memory however - that makes it inconceivable, it would have infinite size -, and it requires infinite memory to store all of Pi. Our reality doesn't have an arbitrarily accurate approximation of Pi - this would be a rational number, a fraction - it has Pi in all its delicious transcendental infinite glory. And because Pi is transcendental, people in the real world cannot square a circle. The latter being a physical process.
A finitely sized computer could only store finitely many digits of Pi. This would make Pi rational, so the circle would be square-able; it isn't, so we're not in one of those.
I literally can't imagine what that would be like in any coherent way. I suppose these arguments aren't very good at convincing the unimaginative.
Have you watched any of The Next Generation or Voyager? It's not uncommon for some of the crew to spin up a holodeck program that's as sensory rich as the real world, and there be a malfunction where they're trapped in the program and can't exit.
In one, a simulated character who had become aware made a simulation of the entire ship to fool the crew members into thinking they had exited the holodeck.
I've watched NGE and Deep Space Nine. I still can't imagine a holodeck the size of the universe.
Wiki has a decent article on it..
If you ran a planet-sized holodeck, would we be able to know it wasn't actually the size of the universe? We could think we were sending a probe off into deep space, and it's just the program making it look that way. Even in a room-sized holodeck, they're somehow able to move around quite a bit as if they weren't constrained to a room.
It would only need to be the size of your immediate surroundings.
It would need to be able to generate any set of surroundings. This goes beyond being a procedurally generated universe, as it would have to generate this one.
It wouldn't have to generate the whole universe, though. It would only have to generate the things that you will actually see.
But it does have to potentially generate anything you or anyone could actually see, hear, etc.
It isn't a perceptual difference. It's akin to a law of nature.
Argument goes as follows:
Assume (A) we are in a simulation, then consider the following argument:
(1)Pi is transcendental.
(2) Transcendental numbers require an infinite amount of information to specify fully.
(3) If a transcendental number is not specified fully, it is approximated. (2)
(4) Approximations to transcendental numbers have terminating or repeating decimal expansions. (this is the definition of an approximation)
(5) Approximations to transcendental numbers are rational. (4)
(6) If Pi were rational, we could square the circle.
Supporting (6) from the Wiki page:
(7) The computer running the simulation would have infinite memory if Pi were transcendental. (2)
(8) Computer memory must have non-zero size.
(9) The computer running the simulation would be infinitely large to contain infinite memory. (7, 8)
(10) The computer could not be infinitely large.
(11) The computer must use a finite approximation of Pi. (10,5)
(12) We could square the circle (6,11)
(13) We cannot square the circle.
Now we gotta follow the contradiction back:
(12) is false, so (11) is false since (6) has been proved independently, so (10) is false since (5) has been proved independently. So either the computer is infinitely large, or (8) is false, if (8) is false then either Pi is equal to an approximation (5) and then (1 or 2) is false. We know (1) and (2) and (5) are true, so either (A) is false or the computer is infinitely large.
The computer isn't infinitely large, so (A) is false.
So whether or not we can square a circle isn't open to empirical investigation? Then how do we determine that we can't?
Did you read the Wiki page on squaring the circle?
I think the argument is that in order for the simulation to make a circle non-squarable when we try to square it, it would have to compute the transcendental number PI, or we would be able to accomplish the task.
This is what it means to be unable to square a circle: it is impossible to construct a square with exactly the same area as a given circle using only a ruler and compass. The 'impossibility' isn't something which is derived from perceiving squares, circles or generalising from how they look. The impossibility is derived through the way ('drawing using a ruler and compass' 'circles' 'squares', 'pi' and 'transcendental') relate to each-other as a mathematical composite; the first of which is something which can be done in a universe whenever those concepts make sense. The theorem states that there is no procedure - real, constructible - to make a square with exactly the same area as a given circle using only a ruler and compass.
Is it really that confusing to think that concepts (compass+straightedge construction and Pi being a transcendental number) relating to an activity can demarcate what is possible (the circle cannot be squared) within that activity? I think this is a pretty commonplace occurrence, and isn't confined to a-priori constructions either:
A rock could not become alive. (synthetic a-priori, probably)
A state in which no votes are ever cast could not be called democratic. (analytic)
A bachelor cannot currently be married. (analytic)
Radon is not chemically reactive at standard temperature and pressure [IE, no radon dioxide] (synthetic,empirical).
And they can repeat and use all the same equations that we do, so that can't be used either.
So, there are two Pis. Let's call our Pi x and a simulated Pi y. Let's also assume that y is equal to the first 3 decimal places of x. IE y=3.141
y is an approximation of x. This means that the decimal expansion of y stops at some point. Since the decimal expansion stops at some point, y is a fraction. In this case, y=3141/1000.
Now, that means* there can't be a proof that y is a transcendental number. IE, it cannot be shown that y is a solution to some polynomial equation with integer coefficients. This means there couldn't be any expression like:
(z-a1)(z-a2)(z-a3)...(z-aN) = 0
which has Pi as one of the solutions. A familiar polynomial might be z^2 - 1, others are z^3+2z+z, z^n + 3 where n is an arbitrary member of {0,1,2,3,...}. That kind of thing. x can't be a solution to one of those.
But y can. In fact, y is, 3141z - 1000 has y as a root (set it equal to 0 and solve it). This means y is not transcendental, since it is a root of a polynomial with integer coefficients. More generally, if y is a fraction a/b, then bz-a has y as a root. Thus, every approximation of y will not be transcendental.
If we are in a simulation, then y isn't equal to x, since the simulation can't be of infinite size (no infinite memory, infinite memory required to specify Pi exactly). But the reality has to be quite similar to the one with y=x, so y would be an approximation of x. And we're in the situation I described above.
This gives us a means of distinguishing simulated and non-simulated universes while we're in them. A sufficient condition for not being in a simulated universe is: there is a proof that Pi is transcendental. In our universe, there is such a proof.
I appreciate the attempt to frame the proof as being equivalent to some bundle of sense data, but it really isn't a bundle of sense data or a representational artifact. It's a fact, in our universe Pi is transcendental. The 'sense-data' of the proof isn't equivalent to the proof as a demonstration of a fact.
So proof isn't just a bundle of sense data, it's a demonstration that something is true about our universe. If 'pi being transcendental' isn't sufficient for this, surely 'no one can square a circle using a straightedge and compass' is, since it's well within the bounds of a simulation to allow people to play about with axiomatic systems in mathematics and for them to draw with compass and straightedge.
If you want to frame it in terms of visual sense data, it's still possible: in a simulated universe, no one could see a valid proof of Pi is transcendental. And conversely someone could see a construction in the simulated universe that allows squaring the circle. This still allows discrimination between simulated and non-simulated universes based off of the incapacity for anyone in a simulated universe to see a valid proof that Pi is transcendental, since such a proof couldn't exist*.
*unless the axioms of geometry were inconsistent, which they aren't.
Why are we assuming this? What I don't understand is why the person in the simulated universe can't use the same proof that we use (the Lindemann–Weierstrass theorem?) to show that Pi is a transcendental number. Is a simulation incapable of performing the mathematical steps that make up this proof?
Quoting fdrake
So they won't be able to read Lindemann's proof? That seems an untenable claim.
It isn't that they wouldn't be able to read the proof. The strings could be arranged on the page in the same manner. It's just that that proof would no longer be valid since its result is false! So they wouldn't be seeing a valid proof.
Let's put it this way:
In the simulated universe, the area of a circle is yR^2, in our universe, the area of a circle is xR^2. They literally have different values for Pi since the value of Pi for our universe would have to be stored in a finite computer. In the simulated universe, y=a/b and so there is a counter example to the proof: bz-a has y as a root. So the proof is either valid and proves a false result, or it is invalid. We know it's not the former, so it's the latter. Therefore no one in a simulated universe could (modal, necessarily not) see a valid proof that Pi is transcendental. So, no one in a simulated universe could see the squaring of a circle (modal, necessarily not). Conversely, someone in a simulated universe could (modal, possible) see the squaring of a circle.
* Unless there is some empirical difference between simulated circles and real circles.
In our thoughts and mathematical operations, proofs: the whole ideational system of mathematics must be something the simulating computer does. This means it must devote a finite amount of computational resources - memory and processing - to doing any particular part of our mathematics.
When an algorithm is used to compute Pi, it will converge towards the value of Pi in the simulated universe. When a circle is thought, its area will be equal to its universe's Pi times the radius squared. This simulated Pi cannot be our Pi, since our Pi requires an infinite amount of memory to store. Moreover, the simulated Pi will be a fraction. Rest of argument goes from there.
It doesn't need to "store" Pi. That's the bit that doesn't make sense. It only needs to draw a circle, which computers are quite capable of doing. We then measure it and make use of mathematical axioms, always coming to the conclusion that Pi is transcendental. The simulated person will do the same. Therefore this cannot be used to show that we're not in a simulated world.
It's the computer's ability to draw a square which has the same area as a given circle using compass and straight edge which is the problem in the first place. Anyway, how would the computer deal with Pi? There's one correct number for each digit, computer has to be able to access all of them for Pi to work. as it does in our reality. How can it do this without committing the whole of Pi to memory?
So there will be an observable difference between a simulated circle and square and a real circle and square?
Modality man. Modality. The computer COULD do it, 'our' computer COULDN'T.
But I suppose if you were to measure circle diameters and circumferences, you would observe a different value for Pi than the one we get. Edit: with sufficient measurement precision, anyway.
I'm pretty sure that computers can draw better circles than we can with pen and paper, which is presumably how we first calculated an estimated value of Pi?
I don't see the relevance of this. The computer could have a value for Pi so accurate that its error is below the Plank length for a circle with the diameter of the observable universe and there would still be no valid proof that it is transcendental - since it would be an approximation.
How would the computer deal with Pi without committing it to memory? It needs to know whether any digit is correct or not. See no way around it.
Just as a piece of paper doesn't need to store a value of Pi; it just needs to have a circle drawn on it.
I really don't understand how this is relevant. Why do you think the ability to draw a circle in general is relevant to the computer's capacity to square a circle? The computer would be able to draw a very special square for lots of circles such that the square has the same area as the given circle.
Such a computer could not be simulating our universe. Our circles cannot be squared.
You said this:
Quoting fdrake
So you're saying that if I were to draw a circle with a circumference of 100cm and a computer were to draw a circle with a circumference of 100cm then the two circles would have a different diameter?
Yes. Since they have different values for Pi.
My hand doesn't have any value for Pi. It just draws a circle.
Reality does. It's Pi here, it's an approximation of Pi in simulated universes with finite memory. We could go round in circles playing the 'frame what the other person is saying as incorrect but do nothing to address their arguments' game, but I'd rather not.
How would a computer get around needing a specific value for Pi? How would a computer get around needing to know whether a digit is correct or incorrect? Without committing the whole thing to memory, in either case. Or, why is this an irrelevant or misguided question? Why doesn't the computer need a value for Pi when it would have circles with circumferences and diameters like ours? Ones which would presumably have a constant ratio.
So I fail to see how there is necessarily an empirical difference between circles and squares drawn in the real world and circles and squares drawn in a simulation. Thus this "squaring a circle" defence can't help us show that we're not in a simulation.
Assume someone has drawn a circle in the real world, and there's a circle in the simulated world. Both have the same diameter. Do they have the same circumference? No, because Pi is different in each context. They're both circles, but they have a different circumference.
Can you please explain why you think drawn circles in the simulated reality and the real one somehow undermine what I'm saying? And also why this eschews the computer's responsibility to have a value for Pi? The algorithmically drawn circle in the computer will still have an implicit Pi in it. To the extent that raster circles are real circles anyway.
Why would you suppose reality has a value for pi? There are no perfect circles in reality, just approximations of them, like the rim of my coffee cup. There is a Planck length limit to how precise an actual circle can be. But pi can be calculated to as many decimal places as desired (within physical limits) without requiring an actual circle (e.g. 4*(1-1/3+1/5-1/7+1/9-...)).
Whatever you want to call it -real, ideal, virtual, a platonic object, other things-, our mathematics has a specific value of Pi. A computer simulating our mathematical capabilities would also have to simulate their associated ideational structures, irrelevant of their ontological status in the final analysis. It may be that Pi isn't 'real' in the same sense as the ideal circles (and other things) it concerns; nevertheless it must be simulated.
We do have a mathematical value for PI which is irrational and cannot be computed (in full). A circle's definition is determined by the full value of PI, mathematically speaking.
I think fdrake is arguing that the simulation would have to compute us coming up with irrational numbers and other things which aren't computable, such as transfinite numbers. Or the halting problem.
The issue I have is that the maths we use to show that Pi is irrational is the same maths that a simulated person can use to show that Pi is irrational. Given the same axioms and definitions, whatever deductively follows in the real world will deductively follow in a simulated world.
At the end of Carl Sagan's Contact book, a human computer finds a binary representation of a circle inside PI created by aliens who shaped our universe in a way such that PI would have that value so that any sufficiently advanced race who evolved could find out they were inside a created universe.
I always wondered how the value of PI could be modified by the shape of space, but Sagan put that in his story. If it can, then that might have bearing on the value of PI computed inside a simulation.
I always thought PI had to be the same value regardless, but it seems some disagree with this.
Just pointing out that Sagan though the exact value of PI could be determined by the shape of space one exists in. It's not exactly the same, but it goes to the notion that PI's value might be calculated to be different depending on the world one lives in.
The value of pi is defined as the ratio of a circle's circumference to its diameter. That is sufficient to construct actual circles that approach the ideal circle or to approximately calculate pi.
The computer simulation can have the same mathematical definition of a circle and pi as us. But in both cases they are mathematical idealizations and can only be actualized approximately.
Quoting Marchesk
I would put it the other way around. The meaning of pi is based on the definition of a circle (e.g., a round plane figure whose boundary (the circumference) consists of points equidistant from a fixed point (the centre)).
Quoting Marchesk
Yes. But as long as they are understood to be idealizations and not actualized, then I don't see the problem. As an analogy, we have a concept of infinity. It doesn't follow that the universe is necessarily infinite. Similarly for the simulation.
You don't think it would be a problem for the simulation computing our coming up with those idealizations?
Here's an interesting question. Could a simulation learn about the halting problem?
It doesn't have to, the real people that are being fed the simulation will do that (assuming BIV or matrix-style simulation). They will observe their simulated surroundings and develop language and logic accordingly.
All the computer simulation has to do is simulate what is real (e.g., coffee cups with approximately-circular rims). The people in the simulation will come up with the ideas.
Quoting Marchesk
I don't know, but the people in the simulation could which is sufficient. It's just a question of logic. No infinite storage or time is required to understand it.
I agree. Talking about drawing circles is a bit of a red herring. What matters is whether someone could square a circle in the simulation.
I think that's a difference between BIV and the daemon. The daemon has a malicious streak and doesn't even grant us the capacity to think or feel as normal. Being a BIV does, that's what makes it interesting. Regardless, though, there are proofs that Pi is transcendental - do you think that these are fabricated memories or we're forced into believing them?
Merely pointing out that were we a BiV, then we could have fabricated memories implanted. It could even be algorithmic -- anytime someone squares a circle, then erase said memory and replace it with the impression that they proved that Pi is transcendental.
Conditional: brain in vats and memory editing. Should be believed? Nah. Kind of thing people can get therapy for.
Maybe the evil demon created us as BIVs 5 minutes ago with false memories of a past. But the evil demon itself is a simulation, so he has to trick us into thinking we know about transcendental numbers.
It's a daemon's power fantasies playing out in a holodeck in which he creates BIVs impregnated with the idea that they're all in the Matrix.
It amuses me that it's OK to entertain the possibility and the concurrent belief that entertaining the possibility destroys all knowledge, but it's not OK to sincerely believe it.
It's the possibility of radical error which gives reason for doubt, and based on that doubt out goes knowledge of the external world. (at least, so goes a way of putting the argument)
That's a lot more words to say the same thing. It's a more plausible delusion to think that a mad scientist has made us into a brain in a vat than one of those unsophisticated, backwards medieval demons is tricking all our perceptions and memories using the thoroughly irrational and unscientific black magic.
It's more an issue of palate than reason. The skeptical challenge remains the same in both scenarios.
So the skeptic claims that we can't know about the external world because it's possible to doubt it?
That's a really high standard for knowledge. There are rare psychological cases were someone comes to believe their family has been replaced by imposters. And how can you be certain that doppelgangers didn't replace the people you know while you were asleep last night?
On the skeptic's standard for knowledge, I can't know the people I claim to know.
More or less. Obviously there's more than one way to put the skeptical challenge -- and there are more types of skepticism than radical skepticism of the sort associated with Descartes -- but that's the gist of the argument
Quoting Marchesk
I think that's the best way of going about addressing the skeptic, personally. The fault lies in what counts as knowledge, and secondarily how the skeptic divides between how we evaluate internal vs. external worlds.
But even adopting the (rather commonplace, if often criticized) distinction between internal and external, if we examine what counts as knowledge and rework our thoughts on what counts as knowledge, then we undermine the skeptic.
Usually, in the process, though, we also have a weaker form of knowledge. (not that I have a problem with that, but it's a worthwhile realization I came to while thinking through the skeptical problem)
If it wasn't part of the established tradition of philosophy, it would be given the credit it's worth: nothing. No one seriously entertains the idea, the entire premise of this and like ideas are if this is believed; how do we 'access' truth? If this is possible, what can be justified?
'The skeptic' is a bogeyman in philosophy discussions, nothing more.
Sure. The radical skeptic at least. It's more or less a thought experiment. It seems to me that you believe that undermines the thought experiment, though. I don't know why you'd think that. I don't think the thought experiment lies on the authority of tradition. I think it actually makes headway because it plays on common intuitions.
Also, I'm not sure no one entertains the idea. Descartes entertained such doubts, at least, even if it was justified as methodical rather than actual.
Well, there is Nick Bostrom's simulation argument. Sounds like he and quite a few others took it somewhat seriously.
You had Elon Musk asking physicists to find a way out of the simulation! Maybe they told him to shoot a Tesla into space. That would break the simulation for sure.
Allowing the skeptic their innocent imaginings is already giving them enough rope to hang you. We do have knowledge; so the skeptic is wrong in any case. It's probably true that what makes demon-like scenarios so enduring is that they play on the intuition that doubt is set against knowledge. They also invite their reader to imagine knowledge devoid of the contexts it arises in, so it's not surprising knowledge seems unattainable in this light: the deck is stacked.
But it's also true that dealing with the skeptic is something every student taking an introductory epistemology module, or someone with an interest in philosophy reading an introductory text, will be acquainted with. At least Cartesian skepticism. Without that context, it's madness to believe it; and deferred madness - to the hypothetical everyman 'the skeptic'- to give it much weight.
In a parallel universe where Cartesian skepticism was never developed, someone who turns up here writing: "I have a proof that knowledge is impossible, what if there is a demon tricking all our intuitions and knowledge and all we know is the demon's machinations? How can we truly know anything now? The only answer is God.' would have their thread scoured from the forum almost as quickly as an objectivist Holocaust denier.
Nick Bostrom's simulation argument isn't seeking to undermine all claims to knowledge, though. We have to know stuff about the universe and be able to assess probabilities of events for it to get going. Something 'the skeptic' could easily disallow.
I'd say that the same would happen in the universe we actually inhabit.
If memory serves, actually, that did happen with several supposed radical skeptics on this forum :D. (or perhaps the last iteration?)
Quoting fdrake
That the skeptic is wrong isn't the interesting part of the thought experiment, I'd say. Aren't many philosophers wrong, after all? But they can still be of philosophical interest to read. Here what's interesting is why the radical skeptic is wrong -- where is the error? -- and also, supposing these conditions of skepticism, is there some way to persuade the skeptic?
I don't disagree with this. As I said to Marchsk, I think that looking at the meaning of knowledge is what's fruitful. And the fact that the skeptical scenario plays off of intuitions is also what's fruitful -- because those commonly held intuitions are fallible and often mistaken.
Do you think Descartes was mad?
I don't think entertaining doubt, even of the radical sort, is madness -- whether it be a Great Philosopher, or someone before Descartes who had similar thoughts.
You may not find skeptical doubts persuasive, but that doesn't seem enough to make a charge of madness against said doubt. Especially as Descartes lays out his arguments -- obviously there was no tradition of Descartes prior to Descartes, but madness isn't what I'd say is where his thinking comes from.
I remember it happening too. Is why I brought it up.
The most interesting part of the thought experiment is that it's ok for 'the skeptic' to do but not for anyone real. Why on earth would we need to persuade the skeptic away from their infantile delusions and performative contradictions? The deck is stacked in their favour, they will destroy all knowledge (hypothetically) if you let them.
The skeptic isn't a real person, no one acts as if knowledge is impossible, no one thinks that way either. The skeptic is a philosophical construct aligned with the mere possibilities of erroneous justification, and the mere possibilities of error in every belief. We should stop giving into this alternate personality every student of philosophy can adopt, salivating in response to improbable, unjustifiable fear of error which implicates all of reality in a personal conspiracy against them.
Attempting to find necessary and sufficient conditions for knowledge outside of the contexts knowledge arises in is a pointless exercise. If the examination of intuitions is the goal and sole reason to entertain 'the skeptic', why not look at how people come to knowledge in the real world? Believing in the utility of skeptic thought experiments actually has real consequences for epistemology: for one, the skeptic (and the JTB enterprise it is coupled with) are entirely concerned with propositional knowledge. Secondly, they don't allow any incorporation of learning skills or learning facts to resultant knowledge-how and knowledge-that. And for three-the skeptical hypothesis is indifferent to how beliefs and competences form networks that allow people to act skilfully in the real world.
Far from analysing how people actually obtain knowledge; the corner of philosophical discourse devoted to the skeptic isn't even examining the conditions of possibility for knowledge - it's far too constrained for that. Dealing solely with propositions, hypothetical justifications and the mere possibility of error in belief.
It is even an impoverished form of skepticism, the pyrrhonists at least espoused skepticism for a practical reason, and prescribe ataraxia as an appropriate response to the real lack of 'ultimate justifications'. What is the character of someone who really believes in Cartesian skepticism? They are paralytically obsessed with the impossibility of knowledge while constantly embodying its use.
It isn't madness if you're currently doing philosophy, it's absolutely madness if you allow skeptical hypotheticals to effect you in any other way. Cartesian skepticism only makes sense on the background of propositional knowledge and obsession with sufficient justification's adequacy for truth.
Of course he wasn't mad, he quickly dismissed his skeptical hypothesis.
Sure it is. Which is why it's an interesting puzzle to ponder. I wouldn't say need is the basis for wondering about persuasion. I would say we don't need to do philosophy, even, for that matter. Rather than necessity I think the motivation is one of curiosity.
Quoting fdrake
I don't feel like I'm giving into anything. I feel like I have responses to the skeptical scenario. As I read you, at least, it seems that you do as well. But there aren't any factual -- at least, empirical -- grounds for refuting the skeptical scenario, based on exactly what that scenario entails; that the world as we experience it appears identical, yet is actually different. (Another distinction which one could attack the skeptical scenario on)
Quoting fdrake
I don't think that the skeptical scenario is goal-bound. Philosophy isn't exactly goal-bounded, either. Being able to think through why you disagree with the skeptic is fruitful, though, in that it is a good exercise.
Also, oftentimes when we approach a question by looking at examples -- as often as I really do use this method -- the examples are overdetermined by our intuitions. So having thought puzzles to ply at those intuitions are useful to philosophical exercise.
Quoting fdrake
I don't disagree that the skeptical scenario has real consequences for one's epistemology. But I don't think dismissal is the exact right response, either. While we have no need to address the skeptic, while we can investigate knowledge otherwise I would also say that one is not devoted to JTB forms of knowledge just by way of responding to the skeptical scenario. Like, at all.
I mean, while I think examining what we believe knowledge to consist of is the best response to the skeptic, that doesn't mean we have to believe that knowledge is purely propositional. Why would it?
I don't think the skeptical scenario is foundational to epistemology -- which is maybe what you're against -- but I also don't see a reason to be dismissive of it. It seems to me that formulating a reasonable response, of whatever sort, is the proper philosophical route.
Quoting fdrake
Well, if they actually follow Descartes then whatever character follows from dualism I suppose :D . Surely the only people who espouse the Cartesian scenario as something which "destroys" knowledge are students of philosophy, and worth engaging for pedagogical purposes only. While that may be the case, I don't think it makes sense to just dismiss the scenario. There are reasonable responses to it.
I suppose what I would say is a reasonable response to Descartes (for surely not everyone who reads Descartes also then goes "all the way" while forgetting the solution) for a student would be to ponder it, not to claim that we have no knowledge. To wonder how, not to adopt the method as actual and forget the solution. Or, as I think most do, passing over isn't all bad. But it does strike me as being a-philosophical.
I do like the Pyrrhonists.
Some other things about skepticism, though: Often times, when someone expresses skepticism on particular things, or on some categories, incredulity is the gut reaction you face. So, say, with God. Or moral facts. Or propositions. In some way I look at the skeptical scenario as a way of thinking through any skeptical problem, at its "limit".
@StreetlightX (for shared interest in Laruelle)
Holding or studying JTB is neither necessary nor sufficient for responding to skepticism, the point I'm making is that skeptical scenarios are close conceptually to accounts of propositional knowledge, especially necessary/sufficient conditions for it. Propositions are the target of justifications, justifications are undermined through skeptical scenarios (can say the same about Gettier cases). You can vary what counts as an adequate justification, and in doing so attack the skeptic: eg. fallibilist justification sweeps the rug from under their feet, foundationalist justification under the guise of hinge propositions attempts to do the same; but it's still the same highly constrained and a-historical account of knowledge that makes sense as something for the skeptic to attack. Can radical doubts be formulated in the same way against, say, knowing how to ride a bike? Specifically, sufficient conditions for knowing how to ride a bike are competences - which don't always have propositional equivalents.
Conceptual/contextual baggage of radical skeptical inquiry destroys the context in which knowledge arises, taking it to a bizarre intellectual limit in which paranoid delusions become respectable avenues of thought, lived life is condensed into a logical network of linked propositions; engaged with merely through assent and disbelief, and anything within the bounds of possibility masquerades as justified belief.
Then what's the point in pretending to be the skeptic? Do we really carry a copy of a rebuttal for every skeptical scenario to allow knowledge to take place?
Maybe it's a non-philosophical approach to skepticism. The skeptic and propositional knowledge are inseparably joined through the unilateral need for philosophically rigorous dismissal of the skeptic; the philosopher is pretending to be the skeptic through interlocution and the distinction between them dissolves in the process; only to be re-contextualised as an imagined enemy. The enemy only makes sense in the context of the theatre of skeptical arguments.
Seeing it as a philosopher's dramatisation of an imagined struggle - when reason reconciles itself with paranoid delusion - takes the sting out of it, no?
It's a good question. I think it may depend upon whether or not you'd consider riding a bike in the vat is the same as riding a bike outside of the vat. I wouldn't change the scenario (especially since I consider the radical scenario pretty much the same, rationally, just with different dressings). I just wonder if we could count these as competences or not.
Quoting fdrake
Wouldn't any a priori investigation do the same?
Also, doesn't any investigation bring along conceptual or contextual baggage? There are, after all, only so many words to use. And philosophy has a long history.
Quoting fdrake
Well, I don't think there is a point. And of course you don't carry a copy of a rebuttal for every skeptical scenario just to allow knowledge to take place. Simply by changing the definition of knowledge you're already talking about something elsewise from the skeptic.
I think many, if not all, philosophical puzzles are like this. There is no point to them -- they are fully and completely useless. But engaging in them is a good exercise of the intellect, and formulating responses are the same. And often what is useful is what comes out of such inquiries -- but the inquiries aren't bounded by the terms of use or purpose.
To give other examples, what is the point of of formulating the question of the meaning of being such that it becomes meaningful again? What is the point to formulating a general theory of justice? What's the point of understanding knowledge historically, as opposed to a-historically?
I think points, purposes, reasons, and so forth are found after the fact. Which is why philosophy is, paradoxically, uselessly useful. (at least, philosophy of this sort)
But as for points that I see -- it's a good exercise in a priori reasoning. It pries at commonly held intuitions by working off of them and coming to absurd conclusions. It's relatively straightforward and easy to communicate. It generates novel solutions to the problem of skepticism which are interesting unto themselves. In a way it is a propaedeutic to philosophy -- else you might have people claiming they are certain of this that or the other when they are only provisionally so. It also serves as a class example for all sorts of skeptical problems, and working through it rationally helps one to let go of the gut reaction to balk at what is, on its face, unreasonable.
Quoting fdrake
Heh. I can see it doing so for some people. I suppose it would have to sting in the first place, though. :D I don't feel that sting as much precisely because I'm not a skeptic, and have formulated thoughts and responses to the scenario that were sufficient for myself.
And, on a rational level at least -- though belief in skeptical actualities probably doesn't take place at a rational level, that I'll grant -- it seems to me that whether the skeptical scenario is presented as a drama or no that the puzzle remains the same.
Quoting Moliere
It's funny that you're using 'you' and 'I' there to refer to precisely the same person; yourself viewed as the modifier of skeptical scenarios (the skeptic); which implicates yourself as the impersonal arbiter of philosophical sense; and then yourself viewed as a practician of philosophy with specific opinions on skepticism and its relation to its opposites.
That's the bizarre conceptual (decisional) form of radical philosophical skepticism in motion. The disavowal of the skeptic takes a positive form in terms of the impersonalisation of their (your) claims, which retroactively constitutes the philosophical manoeuvres the skeptic will make and has already made. A negative form accompanies in terms of the presupposed repudiation of their (the skeptic's) claims which, it is posited, has already happened - as logically required for further engagement with the role (and its problems). The skeptic is a philosophising person disavowing their own methods of interlocution and the consequences their borderline schizophrenic beliefs should have on themselves.
More later.
It only makes sense if 'you' is an every-person. Why would whether Cartesian skepticism works the same for know-how as know-that turn on my analysis of it? It doesn't. In case it isn't clear, I don't mean that you personally are borderline schizophrenic, I mean that the way 'the skeptic' functions in discourse gives off that vibe for the reasons I stated.
Every analysis has contextual baggage, what matters for the analysis in the long run is whether that baggage is enlightening or occlusive for its subject matter. Constraining knowledge to knowledge that through the lens of radical skepticism sheds no light on what knowledge is for humans. If philosophy is the process of conceptual window-cleaning, this is spraying de-icer on the walls.
The levelling of lived life to a network of propositions, entailments and mere possibilities which operates in every radical skeptical hypothesis is so destructive to actually learning about the function of knowledge (what it does, how it works, why it can come to be) that learning, know-how, any 'externalities' such as biology, pedagogy and psychology of knowledge are deemed irrelevant. All that matters is the fact that X and our belief that X and that never the twain shall meet.
The skeptic can never be answered sufficiently because purely by assuming their role for the purposes of discourse - presumably learning about knowledge - any strategy of undermining them can be dismissed without reason - the mere logical possibility of incorrectness. We may as well lay everything humans have found out about anything, including the rest of philosophy, down at the skeptic's wrathful altar and hope not to meet their eyes. Even though their eyes are always, really, our own.
Then it's odd to give sufficient enough power to a skeptical hypothesis as to sophisticatedly entertain paranoid delusional fantasies to the tune of literally the whole of reality being out to get you. The only things you get out of skeptical inquiries are the philosophical equivalent of getting off on a technicality in court or the destruction of all knowledge.
Of course, attempting to treat the skeptic as a threat is something the discursive role of 'the skeptic' doesn't allow, it is to be ironically entertained then disavowed when venturing out of its native philosophical context. In ecological terms, radical skepticism is a sink bog - carcasses of dead ideas, no entry without real danger, no escape on its terms.
I think you're misreading me as a quietist, this isn't my intention. I'm interested in 'the skeptic' as a discursive role here. Hence all the references to the character of the skeptic and describing how the transformation between 'normal philosopher' and 'skeptic' is inherent in 'the skeptic' (and hence radical skepticism) as a philosophical construct. Still doing philosophy here.
It seems you agree that the only escape is to ironically disavow the judgemental whispers of our angry God.
Does it matter?
If all we have to go on are the manifestations of what we sense and the conclusions we draw from them then this is our reality. It is our reality regardless of whether it is directly lived or simulated somehow. I think the only real question is why it appears as it does. We see the sun rise we learn the earth moves and similarly for everything we know about the world. I think the suggestion that there is a hidden reality somehow behind what we experience, is similar to positing BIV.
Quoting fdrake
Cool. I think that helps me to understand more of where you're coming from.
Quoting fdrake
I don't really view responses to the skeptical scenario as one of escape. If the skeptic is wrong then there is nothing to escape from, after all. There are only a handful of inconsistent beliefs based on intuitions of interiority and exteriority, certainty and doubt, reality and appearance, and knowledge and opinion. I tried to line these all up in the same way to show how these four intuitions are structured along a similar axis -- interiority, certainty, reality, and knowledge on one side with exteriority, doubt, appearance, and opinion on the other. There may be others but these are the four intuitions that come to mind at the moment that the skeptical scenario plays off of. We know ourselves with more certainty than the external world. We have a "more imediate" connection to our interiority while we are distanced from and judge exteriority. I, at least, am real -- for I am a thinking thing, and in the moment of thinking "I am" I cannot doubt such a proposition.
In addition, we desire certainty. So the possibility of error plays off of this desire for certainty, stability, and control.
In some ways I view all of these intuitions as traps of thought which apply elsewhere. So I view the skeptical scenario not just as a play -- though I think your characterization has merit for understanding the discursive function of the skeptic, for sure -- but as a tool which takes commonly held intuitions and brings them to conclusions so absurd that they are not acceptable. (for most, at least) It's more a method of bringing someone to a reflexive position towards their own intuitions -- though, granted, it seems that we have seen examples of it doing the complete opposite, where someone doubles down on those intuitions and "bites the bullet" -- but I don't think that's the usual route, just the one you see because it's far more expressive and ridiculous.
It seems to me that by changing our intuitions and questioning our initial beliefs about knowledge that the skeptical scenario is avoided before it gets off the ground. But if we have such intuitions about knowledge, etc., then the skeptical scenario's philosophical point is that it puts those very intuitions into question.
So you view the skeptic as a kind of philosophical barometer for bullshit? If a position allows radical skeptical arguments to be applied to it - or are a result of that position - you think 'this is bullshit' and move on?
This actually ties into ancient skepticism, in a way. Ancient skeptics would use arguments in a medical capacity -- the goal was to help a student attain the appropriate attitude towards various philosophical theories, one where you neither assent nor deny their truth.
In that sense of an argument being judged for its medical usage -- or perhaps hygienic or pedagogical? Since I don't think the radical scenario is one that's needed for a cure, like the ancient skeptics, but does help one achieve a certain appropriate attitude -- I'd say that the skeptical scenario is a sort of hurdle which, once overcome, has a person thinking more clearly. The set of intuitions I listed are common enough, and often incorrect, that it makes sense to help guide someone interested in a philosophical view of things to be able to suspend said intuitions. Or, at the very least where that's not possible, be aware of them as unexamined beliefs held.
The majority of people who read Descartes do not end up "biting the bullet". Now they may just pass over it as a non-problem, which isn't exactly my goal either, but they at least don't fall all the way down the rabbits hole. I suppose there is an empirical element to this -- what are the common reactions to the radical skeptic scenario? How do people actually respond?
But ideally, from my view, overcoming the hurdle allows one to put to rest erroneous beliefs and unexamined intuitions which commonly structure our thought regardless -- and hence would rear its ugly head in examining other philosophical problems.
EDIT: Also, I think it a worthwhile part of any philosophical education to teach the skill of questioning and suspending your own priors. The skeptical scenario, being ridiculous and unacceptable, is a sort of hammer which, I hope at least, helps one recognize that ability to examine your own beliefs.
I don't know if skeptical hypotheses as a treatment for pernicious intuitions actually pans out. The thread title is literally "BIV was meant undermine realism' by attacking semantic externalism. I find it more likely that skeptical hypotheses are co-morbid with faulty intuitions. Externalism being the thesis that internal linguistic stuff is related to external linguistic stuff, internalism being the thesis that this is false in some way.
If it's true that semantic externalism allows its believers to wrestle themselves out of the vat, or the vat undermines semantic externalism, it still implicates the kind of treatment as compatible with the disease - they meet as contraries in the same context of presuppositions.
And there is definitely something to what you're saying -- that solutions are (often) co-morbid with pernicious intuitions. I tried to read the paper that the OP was referencing, but I couldn't find one that talked explicitly about anti-realism -- only the argument about how a BiV could not refer to itself within the BiV due to semantic externalism. But there's that dichotomy again -- internal/external -- which, being a solution, certainly lends support to what you're saying here.
Hrm hrm hrm. Not sure if I have much else to say. But thanks for sticking with the conversation. It's been interesting (not to cut things off -- by all means feel free to continue. I just wanted to give a faster reply, and I think I've run out of thoughts)
Had the same feeling, think we've covered everything interesting. :)
"Well, one day in 1917 I was standing on the deck of my ship looking back at the wake—it was all white because of the bubbles—and I began wondering idly how many bubbles there were back there. Millions, obviously. I’d learned at school that in order to make a sphere, which is what a bubble is, you employ pi, and I’d also learned that pi is an irrational number. To how many places, I wondered, did frustrated nature factor pi? And I reached the decision right at that moment that nature didn’t use pi. I said to myself, ‘I think nature has a different system, and it must be some sort of arithmetical-geometrical coördinate system, because nature has all kinds of models." Buckminster-Fuller.
I don't think nature uses Pi either, except as part of our constructions. There's something in Pi being part of a bridge between our constructions and nature.
Edit: it's a long article, I've skim-read and it seemed quite good.