The Impossibility of Skepticism

I hope I will be forgiven for abusing the term “skepticism” here — for what I have in mind is not a perfectly innocuous “claims require evidence” epistemic prudence, but rather Cartesian skepticism.

According to the Cartesian skeptic, one can be perfectly certain about one’s own mental contents and yet also be in total doubt about what really corresponds to those mental contents. Hence she needs an argument that will justify her belief that there is any external reality at all, and that at least some of her mental contents can correspond to it.

There are many responses to Cartesian skepticism, and here I want to pick up on one strand in the pragmatist tradition that, on my view, cuts deepest into what is wrong with Cartesian skepticism.

I think that one cannot talk, in any intelligible sense, about justification in the first place without also committing oneself to a belief in other minds with whom one shares a world. (Not that I like that way of putting it — “a belief in other minds” is a much too intellectualistic interpretation of the myriad ways in which we experience the sentience of nonhuman animals and the sentience-and-sapience of other human animals.)

I say this because justification is itself a social practice — and one that we ourselves are taught how to participate in. (In the contemporary jargon, I’m a social externalist about justification.) For what is justification? It is a normative assessment of the evidence and reasons for one’s claims. But that normative assessment necessarily involves other rational beings like ourselves.

Think of it this way (taking an example from Wittgenstein): suppose I’m waiting for a train, and I want to know if it will be on time. I could look up the schedule. But suppose further that instead of doing so, I imagine the schedule: I look up the time in my imagination. Why isn’t that the same thing as looking up the actual schedule?

The answer is that there’s no constraint on how I imagine the schedule. It could be whatever I want — or subconsciously desire — it to be. But without constraints, there are no norms or rules at all.

Justification is much the same: it is a normative assessment of evidence and reasoning according to rules or norms, and there are no private norms. (Though Wittgenstein doesn’t put it this way, he might say that the very idea of a “private norm” is a category mistake — a category mistake on which Cartesian skepticism and several hundred years of subsequent philosophy have depended.)

So whereas the Cartesian skeptic thinks that we need to justify our belief in the world and in other minds, I think that this makes no sense at all. We cannot justify our belief in other minds and in the world because there is no such thing as justification at all in the first place without also accepting (what is indeed a manifest reality to everyone who is not a schizophrenic or on a bad acid trip) that there are other sentient-and-sapient beings other than oneself with whom one shares a world.

.A further point to make (and the subject of my current article-in-progress) is that justification and truth require both sentience and sapience.

The clue I’m following is Davidson’s triangulation argument: suppose there are two creatures who are each responding sensorily to some object in a shared environment. How is an onlooker supposed to know which object they are both responding to?  If both creatures can compare its own responses with the responses of the other creature, then each can determine whether or not they are cognizing the same object.

The point here is that two (or more) sentient creatures — intentional beings that can successfully navigate their environments — can each have a grasp of objectivity if and only if each creature can

(1) represent the similarities and differences between its own embodied perspective and an embodied perspective occupied by another creature and

(2) be motivated to minimize discrepancies and eliminate incompatibilities between its own action-guiding representations and its action-guiding representations of the other creature’s action-guiding representations, and in the process

(3) attain the metacognitive awareness whereby it can take its own embodied perspective as an embodied perspective, and thereby be aware that how it subjectively takes things to be is not (necessarily) how things really are.

This process is facilitated by a shared language that allows each creature to monitor how each is representing the other’s representations and revise its own representations when incompatibility between representations is discovered. The function of norms — of discourse and of conduct — is to motivate each creature to revise its representations when incompatibilities are discovered.

One important implication of this argument is that sentient creatures cannot distinguish between their own subjective orientation on things and how things really are. They lack an awareness of objectivity and an awareness of their own subjectivity. By contrast, sapient creatures are aware of both objectivity — how things really are, as distinct from how they are taken to be — and subjectivity — how things are taken to be, as distinct from how they really are.

This line of thought also explains why I have been adamant that objectivity does not require absoluteness: sapient creatures can be aware of the difference between how things are and how they are taken to be, and thus be aware that they might have false beliefs, even though no sapient creature can transcend the biological constraints of its form of sentience.

532 Replies to “The Impossibility of Skepticism”

  1. Kantian Naturalist Kantian Naturalist
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    says:

    Neil Rickert: Yet, quite obviously, this “cutting edge” philosophy of mind is not cutting it.

    And you know this how? Do you know enough about contemporary philosophy of cognitive science to explain how it is deficient?

    Science describes things in terms of a few basic concepts such as mass, length, time.

    Somehow, people are failing to see that mass, length and time are all human artifacts.They are not something to be found in the world. They are to be invented. Except that perhaps a completely different conceptualization might be invented instead.

    This all sounds quite badly confused. It is true that scientific theories are conceptual frameworks, with both constitutive rules and supplementary rules about how to apply those concepts in measurements. But it’s not true that scientists and philosophers are confusing those frameworks with reality. (Well, possibly some scientists are. Usually the ones who have foolish things to say about philosophy.)

    In any event, it’s not at clear how keeping clear the distinction between conceptual frameworks and empirical phenomena would improve the prospects for cognitive science and philosophy of mind.

  2. Kantian Naturalist Kantian Naturalist
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    BruceS: I meant that the neural processing which we share with BIVs is compatible with any scientifically acceptable higher level description of perception as well as with the philosophical analyses of perception that I am aware of.

    Sure, in a “just add magic” sort of way.

    Suppose one takes a fully trained-up mature human brain, with all of its trillions of connections that embed decades of immersion in varied, complex, and highly structured social and physical environments, and then magically transpose that synaptic network onto a blank brain grown in a lab. (Magic is required for growing a brain all by itself, too.)

    Suppose we then attach data channels to the optic nerves, auditory nerves, and other sensory nerves. And suppose — just add magic! — that the data being supplied in that way was sufficiently similar to the complexity of information that our sensory receptors are constantly extracting from the play of energies across their surfaces.

    A brain in a vat would then, of course, perceive perfectly well — because we added magic to our description of the case.

    I don’t think that just adding magic is a respectable way of doing philosophy.

  3. newton
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    says:

    walto: but it’s also not clear what the hell you’re talking about in the first place, which I guess shouldn’t be that much of a surprise, but still.

    Just imagine if he didn’t like you ,fifth.

  4. GlenDavidson
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    says:

    Kantian Naturalist: So my corrected position is that Cartesian skepticism is not really conceivable, not that it is logically impossible.

    That does sound a lot better. I don’t know if it’s really not conceivable in any sense, but it doesn’t seem that anyone consistently acts like it’s the truth.

    Glen Davidson

  5. walto walto
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    says:

    Well said, kN.

  6. fifthmonarchyman
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    says:

    newton: Just imagine if he didn’t like you ,fifth.

    😉

  7. walto walto
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    newton: Just imagine if he didn’t like you ,fifth.

    I do like the guy–but he can be incredibly [whirrr…sproink…click hiss] annoying– with a capital double N).

  8. Kantian Naturalist Kantian Naturalist
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    says:

    GlenDavidson: That does sound a lot better. I don’t know if it’s really not conceivable in any sense, but it doesn’t seem that anyone consistently acts like it’s the truth.

    A follow-up thought, about what it takes for something to be “conceivable”.

    Peirce’s famous pragmatic maxim goes, “Consider what effects, that might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.”

    I think the position of the Cartesian skeptic is not conceivable in this Peircean way. (As Peirce himself pointed out.) For the differences in any possible practical bearings between the skeptic and the naive realist turn out to be utterly null and void.

    There just might be a subtle difference between two figures or voices we can imagine here. The Cartesian pragmatist is someone who finds the Cartesian skeptic fully intelligible and is willing to say that for all she knows, maybe she is being deceived by a malign genie. But, she adds, there’s no way to really know one way or the other, so it can’t matter. The Peircean pragmatist, by contrast, is someone who doesn’t even find the Cartesian skeptic intelligible in the first place.

    It’s a subtle distinction, but maybe one worth making.

  9. GlenDavidson
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    says:

    Kantian Naturalist: Sure, in a “just add magic” sort of way.

    Or maybe in a “just add highly advanced technology” sort of way.

    Suppose one takes a fully trained-up mature human brain, with all of its trillions of connections that embed decades of immersion in varied, complex, and highly structured social and physical environments, and then magically transpose that synaptic network onto a blank brain grown in a lab. (Magic is required for growing a brain all by itself, too.)

    Why wouldn’t you just take the mature brain, hook it up, and put it in the vat?

    Suppose we then attach data channels to the optic nerves, auditory nerves, and other sensory nerves. And suppose — just add magic! — that the data being supplied in that way was sufficiently similar to the complexity of information that our sensory receptors are constantly extracting from the play of energies across their surfaces.

    Is it beyond possibility that in the future that could be done? But really, this is a matter of logical possibilities, not even a “in the future it may be possible” scenario. I mean, I doubt that many think Descartes’ demon is anything but magic, however we might very well consider the possibility, because we don’t know what the ultimate limits happen to be–and more importantly, the real question is how we know that what we perceive is “real,” not really how a brain in a vat might think it’s part of a body that’s romping through the daisies. That can be left to the gods or techno-wizards, or zombies, for all that I know.

    A brain in a vat would then, of course, perceive perfectly well — because we added magic to our description of the case.

    The actual issue is, what if you somehow did match the inputs and outputs of the brain so well that the brain could not tell that it isn’t “reality”? Maybe even more to the point, the brain is sort of in a “vat” and simply communicating beyond itself via nerves, chemical signals, etc.

    I don’t think that just adding magic is a respectable way of doing philosophy.

    It’s, you know, a thought experiment. Allowed in philosophy, I think.

    Glen Davidson

  10. fifthmonarchyman
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    says:

    walto: The second, which is consistent with pretty much every view of perception I’ve ever heard of has been disagreed with by Neil, but not me–and I’m not sure where KN is on it.

    So just to be clear you agree that our perceptions can’t give us sufficient warrant to insure we have reliable cognitive contact with objective reality.

    and at the same time you have agreed that God could reveal objective reality to us if he chooses to.

    Yet you have explained why in the last 400 posts to me it is a false dichotomy to place those two scenarios in opposition.

    Is it correct that that is your claim?

    walto: but it’s also not clear what the hell you’re talking about in the first place

    I’m talking about your claim that I presented a false dichotomy and that you had explained this in the last 400 posts to me.

    peace

  11. walto walto
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    GlenDavidson: Why wouldn’t you just take the mature brain, hook it up, and put it in the vat?

    FWIW, that’s not consistent with the Putnam thought experiment.

  12. GlenDavidson
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    says:

    walto: FWIW, that’s not consistent with the Putnam thought experiment.

    One thing I don’t like about philosophy: Its heavy dependence on authorities.

    Glen Davidson

  13. fifthmonarchyman
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    walto: I do like the guy–but he can be incredibly [whirrr…sproink…click hiss] annoying– with a capital double N).

    I assure you don’t intend to annoy.

    I do intend to try and understand how you attempt to make things work in your worldview.

    And if I’m lucky I’d like to discover one that is actually consistent and can also justify beliefs with out God.

    peace

  14. walto walto
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    says:

    fifthmonarchyman: So just to be clear you agree that our perception can’t give us sufficient warrant to insure we have reliable cognitive contact with objective reality.

    OMG, how many times do I have to repeat this? If “insure” suggests certainty, then no.

    fifthmonarchyman: and at the same time you have agree that God could reveal objective reality to us if he chooses to.

    When did I agree to that? First I have to know what “reveal” means. Does IT entail certainty? If so I’m not sure that’s possible, actually. But I haven’t really thought about it. It seems like an angels on pins questions since I don’t think anyone actually IS certain about things. Knowledge does not entail certainty, as I’ve explained over 300 times now.

    fifthmonarchyman: Yet you have explained why in the last 400 posts to me it is a false dichotomy to place those two scenarios in opposition.

    What two scenarios? What the hell are you talking about?

    fifthmonarchyman: I’m talking about your claim that I presented a false dichotomy and that you had explained this in the last 400 posts to me.

    When I said you had posted a false dichotomy it was when you DID post a false dichotomy. When I asked what the hell you were talking about, it was when (like now), I have no idea what the hell you’re talking about.

  15. walto walto
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    GlenDavidson: One thing I don’t like about philosophy:Its heavy dependence on authorities.

    Glen Davidson

    He was trying to determine whether the words “vat” and “brain” could mean exactly what they do in a world where there had never been any causal connection between vats and our usage. He wasn’t (and I’m not) claiming that other thought experiments might not also be interesting. But putting a mature brain in a vat wouldn’t allow him to consider what he was actually writing about.

  16. GlenDavidson
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    walto: He was trying to determine whether the words “vat” and “brain” could mean exactly what they do in a world where there had never been any causal connection between vats and our usage.He wasn’t (and I’m not) claiming that other thought experiments might not also be interesting.But putting a mature brain in a vat wouldn’t allow him to consider what he was actually writing about.

    Well, that explains why KN was going in the direction, at least, and thanks for the info.

    Maybe it matters to Bruce, but it wasn’t clear to me that it should for what was being discuessed. Anyway, it’s for him to say if it does or doesn’t.

    Glen Davidson

  17. fifthmonarchyman
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    says:

    walto: OMG, how many times do I have to repeat this? If “insure” suggests certainty, then no.

    I guess as many times as it takes you to understand that certainty has nothing to do with it.

    Let me rephrase

    Do our perceptions make it more likely than not that we have cognitive contact with objective reality?

    walto: What two scenarios? What the hell are you talking about?

    Oh I get it now, you direct my to reread your last 400 comments but you can’t be troubled to read the very comment that you were supposedly responding to

    let me quote myself to make it easy for you

    quote:

    It seems to me that there are only two alternatives God chooses to reveal objective reality to me or I have no reliable cognitive contact with objective reality.

    end quote:

    walto: When I said you had posted a false dichotomy it was when you DID post a false dichotomy.

    Yet you don’t even know what the dichotomy was.
    that’s interesting

    peace

  18. Neil Rickert
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    says:

    Kantian Naturalist: In any event, it’s not at clear how keeping clear the distinction between conceptual frameworks and empirical phenomena would improve the prospects for cognitive science and philosophy of mind.

    The difference is that the organism has to invent a suitable conceptual framework. It cannot merely be a computer using data according to an existing framework. So this completely changes the kind of problem that the organism has to solve.

  19. keiths keiths
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    says:

    KN,

    Suppose we then attach data channels to the optic nerves, auditory nerves, and other sensory nerves. And suppose — just add magic! — that the data being supplied in that way was sufficiently similar to the complexity of information that our sensory receptors are constantly extracting from the play of energies across their surfaces.

    A brain in a vat would then, of course, perceive perfectly well — because we added magic to our description of the case.

    You just conceived of it, which ought to settle the question of conceivability.

  20. keiths keiths
    Ignored
    says:

    Also, your invocation of “magic” is premature. Remember, if we are brains in vats, then our only contact with the real world is through the illusory reality that is being created for us. We see the illusion, not the reality behind it.

    If you know nothing of the real world, how can you decide what is and isn’t “magic” in that world?

  21. keiths keiths
    Ignored
    says:

    KN:

    A follow-up thought, about what it takes for something to be “conceivable”.

    Peirce’s famous pragmatic maxim goes, “Consider what effects, that might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.”

    I think the position of the Cartesian skeptic is not conceivable in this Peircean way. (As Peirce himself pointed out.)

    By Peirce’s definition it is conceivable, just not distinct from the non-skeptical position.

    For the differences in any possible practical bearings between the skeptic and the naive realist turn out to be utterly null and void.

    Which is exactly the point the Cartesian skeptic is making.*

    Cartesian skepticism is both conceivable (including in the Peircean sense) and logically possible.

    *But keep in mind that there might be telltale imperfections in the illusion that could clue us into our Cartesian situation. It isn’t necessarily true that Cartesian skepticism and naive realism have the same entailments, though they might.

  22. Flint
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    says:

    keiths:
    Also, your invocation of “magic” is premature.Remember, if we are brains in vats, then our only contact with the real world is through the illusory reality that is being created for us.We see the illusion, not the reality behind it.

    If you know nothing of the real world, how can you decide what is and isn’t “magic” in that world?

    I understood him to be saying that this brain-in-a-vat scenario he laid out requires technology so advanced it’s indistinguishable from magic.

  23. keiths keiths
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    says:

    Flint:

    I understood him to be saying that this brain-in-a-vat scenario he laid out requires technology so advanced it’s indistinguishable from magic.

    Such technology is conceivable, which would defeat his purpose.

  24. walto walto
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    says:

    The view that words would mean exactly the same thing in a BIV world is “internalist”: it puts meanings in the head. Putnam’s theory was externalist. He held, e.g., that “water” in our world means something different from “twater” in a twin world that is exactly the same except that the stuff there that is, on the surface, indistinguishable from our water (is clear, drinkable, required for life, etc.) Twin world scientists discover that twater is made not of H2O, but (e.g.) XYZ. On the externalist view, then, what seems “internally” to be the meaning of a word might not actually be its meaning, and the term “water” in a world with twater wouldn’t refer at all. Similarly, Putnam claimed, “vat” wouldn’t refer to vats if we were (and had always been) BIVs.

  25. GlenDavidson
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    says:

    Kantian Naturalist: A follow-up thought, about what it takes for something to be “conceivable”.

    I’d note right away that “conceivable” takes on a meaning for Peirce that is not the typical meaning of “conceivable.” I use “conceivable” to mean that one can play with the notion, to see what might become of it, indeed, to see whether or not it does have some practical entailments.

    Peirce’s famous pragmatic maxim goes, “Consider what effects, that might conceivably have practical bearings, we conceive the object of our conception to have. Then, our conception of these effects is the whole of our conception of the object.”

    Yes, but that sort of makes the point of some of the criticisms of pragmatism/pragmaticism (in the realm of science his pragmatic maxim could cut out empirically meaningless distinctions, I should think). We don’t think just in terms of practical effects, furthermore, we often do not know the practical effects until we’ve actually explored the various “possibilities.”

    I think the position of the Cartesian skeptic is not conceivable in this Peircean way. (As Peirce himself pointed out.) For the differences in any possible practical bearings between the skeptic and the naive realist turn out to be utterly null and void.

    I’m not sure if that’s true, but it’s hard to know because I don’t think anyone is really a Cartesian skeptic in effect, and at least I know of none. Couldn’t there be illusions within the overall illusion, illusions that the naive realist might miss?

    But again, back to the limits of pragmatism, aren’t neuroscience and psychology more or less involved with matters brought up by the Cartesian skeptic? I’m not saying that a person has to bring up Cartesian skepticism to discuss how we know things, just that issues like the capacity to be utterly wrong about “reality” (in mental illnesses and hallucinatory episodes of various kinds) are affected by our lack of immediate perception of reality. Peirce’s pragmatic maxim is fine for saying in science something like “a distinction without a difference (in outcome) is worthless” (a judgment that may well be true for the time, but not necessarily in the future), but it seems to ignore how we play with concepts and how such thinking may result in better understanding of how humans perceive and understand in a functional manner as well as in a dysfunctional manner.

    I think the pragmatic maxim is just a bit naive when it comes to the work of conceptualization, especially in complex matters. It would also seem to have the problem of asking which is the default. Maybe I should just adopt the skeptic’s viewpoint, if it makes no difference in outcome anyway. Why should the “realist” position be favored? Also, how would we know if it makes no difference–at least by the measure of practical results–unless we explore the issue? Maybe we’ve been ignoring the message that the spinners of “reality” gave to us, just because we’ve been so sure that it was reality that we didn’t bother to consider that someone might be telling us something (it could be an inadvertent “message,” as well).

    There just might be a subtle difference between two figures or voices we can imagine here. The Cartesian pragmatist is someone who finds the Cartesian skeptic fully intelligible and is willing to say that for all she knows, maybe she is being deceived by a malign genie. But, she adds, there’s no way to really know one way or the other, so it can’t matter. The Peircean pragmatist, by contrast, is someone who doesn’t even find the Cartesian skeptic intelligible in the first place.

    Then I would be sad for the Peircean pragmatist. It is intelligible, and I do think that it probably introduces a number of people in a simple manner to some of the issues involved in psychology and in neuroscience.

    It’s a subtle distinction, but maybe one worth making.

    Yes, because even though I think it’s not a very practical suggestion for thinking through problems of perception and knowing, it does at least bring up the important point that eventually it has to make a difference in observable results for us to rightly conclude that the distinction definitely matters (beyond intellectualization, at least). However, just because it does not yield immediate practical results neither means that it cannot do so in some future time, nor that it is worthless as a subject for intellectual exercise.

    Glen Davidson

  26. Flint
    Ignored
    says:

    keiths:
    Flint:

    Such technology is conceivable, which would defeat his purpose.

    So is faster than light drive. A basic staple of science fiction.

  27. keiths keiths
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    says:

    Flint,

    It sounds like you agree with me that the brain-in-vat scenario is both logically possible and conceivable, contrary to KN’s claims.

  28. keiths keiths
    Ignored
    says:

    walto,

    On the externalist view, then, what seems “internally” to be the meaning of a word might not actually be its meaning, and the term “water” in a world with twater wouldn’t refer at all. Similarly, Putnam claimed, “vat” wouldn’t refer to vats if we were (and had always been) BIVs.

    I don’t buy Putnam’s full argument, but in any case I think it’s tangential..

    The fundamental issue in this thread isn’t whether it’s possible or conceivable that we are brains in vats, but rather whether Cartesian skepticism is possible and (now that KN has withdrawn his original claim) whether it is conceivable.

    Brains in vats are just one way in which a Cartesian scenario could be realized, where by “a Cartesian scenario” I mean a set of circumstances in which the flow of information is manipulated to create a completely illusory reality for us.

  29. BruceS
    Ignored
    says:

    Kantian Naturalist: Sure, in a “just add magic” sort of way.

    I don’t think that just adding magic is a respectable way of doing philosophy.

    Well, that post of mine seems to have struck a nerve, so to speak.

    In fact, Putnam pushes the magic even further. He says at one point:

    “Perhaps there is no evil scientist, perhaps (though this is absurd) the universe just happens to consist of automatic machinery tending a vat full of brains and nervous systems.”

    KN, if you think the whole scenario is not worth considering by serious philosophers, why mention it as a target for your arguments from pragmatism against global skepticism?

    ETA: As I mentioned in my original comment , my point was not to disparage your argument, but to question whether it applied to BIVs, since there was an objective (outside the brain/neural system) reality in the BIV scenario.

    Of course, “brains”, “vats”, “sensing” and so on all have different reference for the BIVs in the scenario.

  30. BruceS
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    says:

    fifthmonarchyman:

    and this one from Bruce

    quote:
    I meant that the neural processing which we share with BIVs is compatible with any scientifically acceptable higher level description of perception as well as with the philosophical analyses of perception that I am aware of.
    end quote:

    peace

    Thanks for the S/O, although I have no idea what you are getting on about in using it. But any publicity is good publicity.

  31. BruceS
    Ignored
    says:

    walto:
    The view that words would mean exactly the same thing in a BIV world is “internalist”: it puts meanings in the head. Putnam’s theory was externalist.

    I am sure you have seen the Anderson paper on what is real in IR which among other things covers how the BIV argument fits into Putnam’s attack on Metaphysical Realism during his IR phase.

    AFAIK he never changed his mind about the points Anderson says he is making about MR, aside from backing away from version of a verificationist approach to truth.

    Is that your understanding?

  32. walto walto
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    says:

    BruceS: I am sure you have seen the Anderson paper on what is real in IR which among other things covers how the BIV argument fits into Putnam’s attack on Metaphysical Realism during his IR phase.

    AFAIK he never changed his mind about the points Anderson says he is making about MR, aside from backing away from version of a verificationist approach to truth.

    Is that your understanding?

    Yes I’ve read that Anderson paper. I wouldn’t want to opine on Putnam’s final take on anything though. He was, let’s say, mercurial. Please let me know how you like his perception book when it shows up in your library!

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