A key "culprit" is the Twin earth experiment. Some people already think "Internalism" versus "Externalism" is a non issue which adds to its problems. But alot of the premises in the experiment are dubious such as someone on Twin Earth having identical mental states despite the human body consisting of a lot of water (H20) which means Twin humans body would consist largley of XYZ making any identical states implausible. — Andrew4Handel

Agree, it is implausible, but still immaterial (pun intended) to the point of the experiment. So what if the twin Earth were antimatter? Now the chemistry is identical, and so are the mental states. The thought experiment now is valid, even after each side discovers the atomic structure of water.

Also I have mentioned a problem with counterfactuals so in this case, and others, the existence of these planets (or aliens) is highly unlikely or non existent.

It seems that the existence of a twin Earth (real water, not XYZ) is a certainty given that there is only a finite set of states of matter in a finite space (a Hubble Sphere for instance), and that space is infinite. Max Tegmark computed an upper limit to the distance to the nearest such twin, but elimination of unnatural states (aluminum cube planets, humans with memory of a different sky than what they see) puts the actual distance much closer.

Finally, what requirement is there for the plausibility of a thought-experiment if the implausible part does not interfere with the point? If there was no Prof Knut Nordby, would the Mary's Room thought-experiment be less valid? Such thought experiments seem the only way to explore subjectivity.

I don't see how mental states in two different people can be identical because they are in different minds, bodies and in different places. The point of the thought experiment is that XYZ is not H20 Therefore if you think brain states are mental states then because the brain contains H20 they can never be in identical brain states.

The premise of the thought experiment misrepresents language anyway. When people refer to water they are never referring to H20, as was pointed out most water contains much more than H20 so the referent of water is more vague and can refer to impure water in seas, lakes, streams and cups etc. There is no reason for language ever to refer directly and infallibly to essences.
The theory of H20 can be usurped so in which case language would never refer to anything (see changing models of atoms). I think language only refers to mental states, such as the appearance in consciousness of water, and not essences.

The Mary's room argument is plausible because nothing in it is impossible even if the conclusions or implications of the thought experiment are considered invalid. And people are born achromatic so there has always been the possibility of asking them about colour concepts. It was just convenient that Nordby existed and was an expert in the field so that he could prove that all current knowledge of colour science and perception did not get him close to knowing what red is like.

It is suspicious if in order to support a position you have to create a wild thought experiment invoking nothing that is immediately possible. Why can't a thought experiment for "externalism" just use our planet and our senses? The Prinz tentacles one is even more wild and confusing and I think invoking physics is pretenious because even phycists are uncertain about how to interpret phenomena so it is unlikely a philosopher without a physics background could invoke physics ideas validly.

Also, since we don't know what conscious states are assuming they are brain states that are identical to biochemical configurations is begging the question.

FWIW, I too find Twin Earth devoid of interest or significance.

Other examples like Prof Nordby are human experts on bat echo-location or other animal senses that we either don't have or have in enormously lower amounts, like a shark sense of smell or its ability to detect electric currents.

But while Mary's Room is interesting to imagine, it doesn't actually signify anything because in the end it just comes down to discussing what certain words mean - in this case 'know'. David Papineau has a nice resolution of it. He says that when Mary sees the tomato she doesn't acquire knowledge of a new fact but rather she has learned new skills, which are to remember what it was like to see something red, and to recognise when something is red. I think it was in a Philosophy Bites podcast that he explained this resolution.

I don't agree that the new skills type argument resolves the issue at all, personally. I don't think the physics theory of colour (wave length etc) and knowledge of the visual system amount to knowledge about colour experiences.

I think the argument is problematic because it seems to rely on the idea that scientific theories usurp experience. But scientific descriptions are only models of what might be behind experince. He makes the same mistake as Putnam in exagerating the scope of language.

I think the argument succeeds however in showing that there are features of experience that cannot be modelled. It undermines reductionism.

It puzzles me how little importance people place on consciousness when it is our only access to reality.

People's position on these thought experiments seems to be ideological in that they are prone to dislike a thought experiment that is opposing their position.

What concerns me though is why extravagant thought experiments get so much mileage. Swampman is another ludicrous one. I don't know any other field that would except these type of thought experiments.

I have my own thought experiment that is akin to Searles Chinese room idea but with no extravagant elements.

I ask people to imagine a box with a triangular and circular holes cut in the bottom. (Easy to make at home with a cardboard box) then you put round and triangular objects in the box, shake it and it sorts them into two piles of similar objects.
This is to show how a structure can look like it is performing an intelligent process (categorising for example) when it is clearly it has no cognitive states. A computer is just a far more elaborate version of this but with no need to invoke mental type states.

Now what would it benefit, to place this thought experiment in the Year 3000 and invoke aliens with two brains who have mastered time travel.

(Parfitt is one of the worse for these kind of excrutiatingly elaborate fantasies.)

https://en.wikipedia.org/wiki/Swampman

"Suppose Davidson goes hiking in the swamp and is struck and killed by a lightning bolt. At the same time, nearby in the swamp another lightning bolt spontaneously rearranges a bunch of molecules such that, entirely by coincidence, they take on exactly the same form that Davidson's body had at the moment of his untimely death."

What about entropy and the second law of thermodynamics?.....I mean come on

Some people simply have too much time on their hands. I would say, would that lightning struck all of them, but that would be both implausible and uncharitable.

"Suppose Davidson goes hiking in the swamp and is struck and killed by a lightning bolt. At the same time, nearby in the swamp another lightning bolt spontaneously rearranges a bunch of molecules such that, entirely by coincidence, they take on exactly the same form that Davidson's body had at the moment of his untimely death."

What about entropy and the second law of thermodynamics?.....I mean come on — Andrew4Handel

A thermal fluctuation is not out of the realm of possibility, at least from the point of view of classical thermodynamics (recall Boltzmann's Brain, for example). An updated version of this hypothetical involves a black hole emitting a fully-formed brain/human, and that too is supposed to be physically possible.

The thought experiment already concedes that the situation is extremely improbable. But why should it matter? Those who hold that there is a sharp, objective fact of the matter with regard to whatever question is being considered here (personal identity, mind, qualia) must accept any challenge, no matter how implausible. Plausibility is a red herring.

no matter how implausible. Plausibility is a red herring. — SophistiCat

I disagree.

I said something similar in my counterfactuals thread. The more implausible a scenario gets the further it is removed from reality and the original premises. It is one thing for all the molecules in a gas to go into the corner of a container but what Davidson proposes goes way beyond that because matter would have to get itself into states of improbability that are supposed to have taken a whole life time and billions of years to reach.

And there is also the impossibility of a mental state being reformed that was derived from personal experience. For example say my boss at work calls me an idiot and that creates a nuanced mental state in me, then that mental state is inextricably linked to that event and can't be identically copied just by recreating a brain state. It is not the equivalent of making a square template and copying it to create an almost identical square, because experiences are not identical to each other or don't have this simplistic "copyability" structure.

In the end it just seems unclear what this thought experiment is saying. LikeThe Twin earth experiment I think it fails to defend the identity-identical claim.

Things are only superficially identical even things that appear identical are in a different space and their atoms are unlikely to be identical. Identical twins can easily be told apart straight away by a dog using scent so there can be very easy routes to proving things that appear identical aren't. For something to be truly identical they would have to be atom by atom identical and in the same space and time.

For example say my boss at work calls me an idiot and that creates a nuanced mental state in me, then that mental state is inextricably linked to that event and can't be identically copied just by recreating a brain state. It is not the equivalent of making a square template and copying it to create an almost identical square, because experiences are not identical to each other or don't have this simplistic "copyability" structure. — Andrew4Handel

This strikes me as incorrect, though, of course, this is all just plausible speculation at this point. Perhaps some day we'll have super 3D printers which can print out identical copies of persons and can test some of these ideas in philosophy of mind, but til then, we are stuck in our armchairs.

I see no reason for supposing that, if you hold some particular memory or mental state, that an exact physical duplicate of yourself would not also have that memory (or a pseudomemory, if you like, the content of which exactly matches the content of your real memory) or realize the same mental state which you are realizing at the moment that your body is scanned for the copying process (such a scan would presumably have to be really, really fine-grained...).

Your argument seems to slip a bit when you move from saying that mental states cannot be identically realized in non-numerically identical minds because experiences are not identical to each other. But this seems to be a non-sequitur: even granting that experiences can't be identical to each other, it doesn't follow that mental states can't be identical to one another. I think you need something more for your argument to go through.

As to plausibility:
To scan a person exactly would violate Heisenberg's uncertainty principle. Matter can be (and has been) teleported, but not scanned for copying. On the other, the copy probably doesn't need to be exact to the quantum level. Any arrangement of molecules in the same places would suffice, so the molecular 3D printer at sufficient granularity to make an indistinguishable copy is not a violation of physics.

That said, everybody takes their own answers into the swampman story, so the thought experiment doesn't really illustrate anything. Arkady: You assume an exact physical copy would have all the memories, as do I, but somebody that argues for memory being part of immaterial state would disagree. So the thought experiment fails to resolve the issue for which it was posited.

That doesn't mean there is no use for thought-experiments. Some eventually suggest empirical tests, and others simply don't apply to humans, but do apply to other beings. What is it like to be cloned? Humans have no memory of it, and I can't ask the things that are. Our society and law is based heavily on the assumption that it cannot be done, or at least cannot be remembered. So I rely on thought experiments to work out the alternate rules, until I find consistent answers.

Things are only superficially identical even things that appear identical are in a different space and their atoms are unlikely to be identical. Identical twins can easily be told apart straight away by a dog using scent so there can be very easy routes to proving things that appear identical aren't. — Andrew4Handel

I don't think we really need dogs to tell apart identical twins: with one exception, I've never known a pair of identical twins which I've had much trouble telling apart.

For something to be truly identical they would have to be atom by atom identical and in the same space and time.

This is an interesting topic. In reading about Leibniz's identity of indiscernibles thesis, I recall coming across the thought experiment (be forewarned: it is rather implausible :D ) of spheres of identical dimensions (and every other feature) in a symmetrical universe. Let us assume the following account of logical identity: A and B are logically identical iff anything which can be predicated of A can be predicated of B and vice-versa.

Now, with the spheres in the symmetrical universe, there is nothing which can be predicated of one sphere (call it "A") which cannot be predicated of the other sphere (call it "B"), and vice-versa, and yet any putative observer would clearly (I think) see that there are 2 spheres. If there are 2 spheres, then A and B are not logically (i.e. numerically) identical, and yet that conclusion contradicts our starting premise which defines logical identity.

There is much literature on the identity of indiscernibiles, and I'm not suggesting that there is no possible way out of this thicket of confusion, but I use this example to point out that the notion of identity is far from straightforward. We should perhaps take care in speaking of what is "identical" (or not) to what.

Arkady: You assume an exact physical copy would have all the memories, as do I, but somebody that argues for memory being part of immaterial state would disagree. So the thought experiment fails to resolve the issue for which it was posited. — noAxioms

Is this true, though? A person may possibly believe that mental states, while themselves immaterial, nevertheless supervene on physical states (or are otherwise emergent from them). In that case, the physical duplicate would still possess the same mental states.

Perhaps a sort of thoroughgoing substance dualist might deny that there is any connection between the mental and the physical, but I don't see how that view can be plausibly maintained once we accept some basic metaphysical assumptions (e.g. that there are material bodies) and scientific observations (e.g. that memories are neurologically encoded in the brain in some fashion, by long-term potentiation or whatever the exact mechanism is, and mental states at the very least correlate in some fashion with the physical state of one's brain).

I disagree.

I said something similar in my counterfactuals thread. The more implausible a scenario gets the further it is removed from reality and the original premises. It is one thing for all the molecules in a gas to go into the corner of a container but what Davidson proposes goes way beyond that because matter would have to get itself into states of improbability that are supposed to have taken a whole life time and billions of years to reach. — Andrew4Handel

I don't understand the point you are trying to make. First, are you saying that the Swampman scenario is nomologically impossible, or just less probable than something else? Either way, the remove from reality may or may not matter, depending on the argument being made; you cannot just make this criticism in general. When using this thought experiment to probe certain crisp metaphysical stances on issues such as personhood, being improbable doesn't disqualify the scenario, though it may make it easier to bite the bullet.

And there is also the impossibility of a mental state being reformed that was derived from personal experience. For example say my boss at work calls me an idiot and that creates a nuanced mental state in me, then that mental state is inextricably linked to that event and can't be identically copied just by recreating a brain state. It is not the equivalent of making a square template and copying it to create an almost identical square, because experiences are not identical to each other or don't have this simplistic "copyability" structure.

In the end it just seems unclear what this thought experiment is saying. — Andrew4Handel

And that is why you should not offer your criticism without understanding the context in which it was proposed. The thought experiment doesn't say anything on its own - rather, it is reactions to it that matter. Your own reaction, which by the way is not unlike that of Davidson, who came up with the gedanken, reveals something about your metaphysical commitments. People with different commitments react to it differently. The experiment serves to highlight these differences.

Is this true, though? A person may possibly believe that mental states, while themselves immaterial, nevertheless supervene on physical states (or are otherwise emergent from them). In that case, the physical duplicate would still possess the same mental states. — Arkady

I think that anybody that expects to take their memories (and thus any sort of identity at all) into what they hope to be an afterlife cannot take a stance of memory supervening on physical states. Claims of OoB experiences rest on memory and sensory input operating independently of the physical apparatus of brain and sense organs. The world (thing in itself) is really how it appears experientially. Anyway, a person holding to such beliefs might suggest a fundamental difference between swampman and his original. The thought-experiment suggests no answer to the question.

Perhaps a sort of thoroughgoing substance dualist might deny that there is any connection between the mental and the physical, but I don't see how that view can be plausibly maintained once we accept some basic metaphysical assumptions (e.g. that there are material bodies) and scientific observations (e.g. that memories are neurologically encoded in the brain in some fashion, by long-term potentiation or whatever the exact mechanism is, and mental states at the very least correlate in some fashion with the physical state of one's brain).

I hear ya.

Now, with the spheres in the symmetrical universe, there is nothing which can be predicated of one sphere (call it "A") which cannot be predicated of the other sphere (call it "B"), and vice-versa, and yet any putative observer would clearly (I think) see that there are 2 spheres. If there are 2 spheres, then A and B are not logically (i.e. numerically) identical, and yet that conclusion contradicts our starting premise which defines logical identity. — Arkady

A putative observer introduces a point of reference, with respect to which some predicates will differ, e.g. left/right.

I think that anybody that expects to take their memories (and thus any sort of identity at all) into what they hope to be an afterlife cannot take a stance of memory supervening on physical states. Claims of OoB experiences rest on memory and sensory input operating independently of the physical apparatus of brain and sense organs. — noAxioms

Sure. I wasn't claiming that any and all people who reject that mental states are themselves physical or material can accept the supervenience thesis, I was just responding to this point of yours:

"You assume an exact physical copy would have all the memories, as do I, but somebody that argues for memory being part of immaterial state would disagree. So the thought experiment fails to resolve the issue for which it was posited."

My point is just that someone could hold that mental states are immaterial and still accept that a person's physical duplicate would hold identical mental states as that person. One doesn't preclude the other.

Furthermore, even if one accepts the existence of an afterlife or OOB (which I as yet see no evidence to accept), it doesn't necessarily follow that physical duplicates wouldn't also be mental duplicates. If one adheres to a type identity of mind, then yes, such a thesis is probably incompatible with believing that a given mental state (a particular memory, say) could be realized both by physical brains and by spiritual ectoplasm, or whatever souls are purported to be made of.

However, any theory of mind which allows for multiple realizability seems to be perfectly compatible with the notion that particular mental states tightly correlate with particular physical states (by supervenience, emergence, or whatever), and that said mental states could also be realized in another medium. Presumably, at least some proponents of strong AI are physicalists with regard to mental states, and yet don't maintain that mental states are inextricably bound to the 3 pounds of oatmeal in our heads: there are other types of stuff which can realize those mental states (including, perhaps, as I said, spiritual ectoplasm).

A putative observer introduces a point of reference, with respect to which some predicates will differ, e.g. left/right. — SophistiCat

I'm not sure the observer is actually necessary, though. We could talk about what would be the case in such a universe, even if no one were around to observe it.

However, I don't see that just any observer necessarily breaks the symmetry. One could appeal to a perfectly symmetrical observer, for instance, perhaps one who is himself spherical, and situated equidistant from each sphere.

Is this true, though? A person may possibly believe that mental states, while themselves immaterial, nevertheless supervene on physical states (or are otherwise emergent from them). In that case, the physical duplicate would still possess the same mental states.

Perhaps a sort of thoroughgoing substance dualist might deny that there is any connection between the mental and the physical, but I don't see how that view can be plausibly maintained once we accept some basic metaphysical assumptions (e.g. that there are material bodies) and scientific observations (e.g. that memories are neurologically encoded in the brain in some fashion, by long-term potentiation or whatever the exact mechanism is, and mental states at the very least correlate in some fashion with the physical state of one's brain). — Arkady

There are other reasons to deny identity of a duplicate - take Davidson's view of the Swampman, for instance. According to Davidson, who is an externalist, it is not enough for two creatures to be instantaneously identical: diachronic differences matter. A swampman may believe that he is Davidson. In fact, he cannot help believing that, since he is an exact physical duplicate of Davidson and his mental state supervenes on his physical state. And yet, unlike the late Davidson before him, Swampman's belief is false, because the truth-value of a belief is contingent on its causal history and Swampman's causal history has nothing in common with Davidson's.

I am not endorsing Davidson's view here - just pointing out how views on the same thought experiment can differ. And that is really the point of such thought experiments.

I just think that a physical duplicate would share the same mental states. I don't believe that the truth value of those mental states (insofar as the states have propositional content) would also be identical. Let us say that I believe that I went for a walk in the park yesterday, and that I did in fact go for such a walk. My belief is therefore true. If a physical duplicate of me was then conjured up by some means, he will also believe that he went for a walk in the park, and yet his belief is false (indeed, all of his memories would be false, I would think).

I'm not sure the observer is actually necessary, though. We could talk about what would be the case in such a universe, even if no one were around to observe it.

However, I don't see that just any observer necessarily breaks the symmetry. One could appeal to a perfectly symmetrical observer, for instance, perhaps one who is himself spherical, and situated equidistant from each sphere. — Arkady

Right, assume a spherical cow observer in vacuum :)

I think what this thought experiment shows is that Leibniz's construal of identity cannot work with a view from nowhere.

Right, assume a spherical cow observer in vacuum :) — SophistiCat

Mmm, spherical cow.

I think what this thought experiment shows is that Leibniz's construal of identity cannot work with a view from nowhere.

Yea, like I said, notions of "identity" may seem relatively straightforward at 30,000 feet, but tend to become rather muddled when examined closely.

That's how I understand Davidson's position as well. And the next logical step is to conclude that the copy is not the same person as the original (because predicates that were true of the original are false of the copy).

David Papineau has a nice resolution of it. He says that when Mary sees the tomato she doesn't acquire knowledge of a new fact but rather she has learned new skills, which are to remember what it was like to see something red, and to recognise when something is red. — andrewk

Being able to remember and recognize red sounds like knowledge. We do use "know" to mean experiential in addition to propositional knowledge.

Remembering and recognizing facts as well as forming propositions requires abilities as well.

A putative observer introduces a point of reference, with respect to which some predicates will differ, e.g. left/right. — SophistiCat

There seems to be no distinction between left and right. If there were, the universe would not be symmetrical. Hard to imagine that, but would there be some sort of inability to count the spheres without breaking the symmetry, and thus actually making two distinct spheres? The definition says they're one thing, and I cannot find a way to dispute that.

However, any theory of mind which allows for multiple realizability seems to be perfectly compatible with the notion that particular mental states tightly correlate with particular physical states (by supervenience, emergence, or whatever), and that said mental states could also be realized in another medium. — Arkady

I was thinking of the identity of those mental states. I feel like I have a persistent identity (being the same person I was a minute ago, despite a different physical state back then, and being the same person I was when I was 4, despite a nearly complete lack of the original matter of which I was then composed). So how am I not already swampman? What has happened in that thought-experiment that has not happened to me? All that's missing is an unverifiable causal connection between the one version of 'me' and the present state.

Being able to remember and recognize red sounds like knowledge. We do use know to mean experiential in addition to propositional knowledge. — Marchesk

I also found that solution to be thin. I did not gain knowledge that Atlanta is the capitol of Georgia, I just gained the skill of remembering it.

Here is an analogy to part of the problem.

Imagine I said to someone "I look just Like my brother" and the person wanted to know what "Like" meant. I could then point towards two sheep and explain how sheep A looked like sheep B.

I wouldn't need to say "Imagine a planet near Earth but without helium in it and then imagine a human like creature with two brains who couldn't speak....."

At what stage do you need to invoke these wild things. You would think they would be a last resort

I think an argument ad absurdum is a different matter. You might say "Utilitarianism leads to the conclusion that we should destroy all life" because this intends to show the extreme consequences of a position at its extreme not to argue that such a scenaio is possible.

That's how I understand Davidson's position as well. And the next logical step is to conclude that the copy is not the same person as the original (because predicates that were true of the original are false of the copy). — SophistiCat

I think this may speak to some of the confusions surrounding the notion of "identity" which I pointed out. Clearly, logical identity is more stringent than personal identity. I believe that two things A and B can be said to be logically identical iff whatever can be predicated of A can be predicated of B and vice-versa.

However, this is clearly too stringent a criterion for personal identity, which seems to be the relevant notion with regard to Swampman-style thought experiments (as far as I can tell). Persons psychologically and physically change a great deal throughout their lives, and yet they remain the same person. In the time it took me to type this post, I no doubt shed a few thousand or so skin cells, and thus am not now logically identical to the person I was when I began typing it, and yet I retain the same personhood or sense of self.

Being able to remember and recognize red sounds like knowledge. We do use "know" to mean experiential in addition to propositional knowledge. — Marchesk

Yes, it can work with that definition of knowledge, as well as with a more restrictive definition.

If we count ability to recognise and remember as knowledge, then Mary did not have complete knowledge of colour vision prior to leaving the room. So she acquires new knowledge when she sees the tomato.

If we do not count ability to recognise and remember as knowledge, then Mary did have complete knowledge of colour vision prior to leaving the room, and she does not acquire any new knowledge upon seeing the tomato, because the new thing is not knowledge.

Either way, Papineau's approach seems to resolve the dilemma.

I like the thought experiment because it makes us reflect harder on what we mean by 'knowledge' in a way that is different from the tired old debates about Justified True Belief.