4 ms·

> when Mary sees a red apple for the first time, some optical/neural pathways get excited that weren't before Not necessarily. By hypothesis, Mary has complete

by pdonis 4y ago

> when Mary sees a red apple for the first time, some optical/neural pathways get excited that weren't before Not necessarily. By hypothesis, Mary has complete knowledge of all the physical facts. That includes the knowledge of how to cause her optical/neural pathways to be excited in the particular way that corresponds to "seeing red" even without the corresponding external stimuli being present. So she could have caused herself to see red. (We might describe this in more conventional language as Mary imagining seeing red, and her complete knowledge of all physical facts giving her powers of imagination far in excess of those of ordinary humans.)

the_af 4y ago
> That includes the knowledge of how to cause her optical/neural pathways to be excited in the particular way that corresponds to "seeing red" even without the corresponding external stimuli being present. Having knowledge and actually doing it are trivially different things (try sex: knowledge of sex and doing the deed are vastly different things). Now, if she exercises her knowledge by stimulating her optic nerves, that's the same as seeing the apple. But that's not just "reading about it", it's a physical act of doing!
- pdonis 4y ago
  > Having knowledge and actually doing it are trivially different things This is a circular argument. You are arguing that Mary does not know what it is like to see red by assuming that she does not know what it is like to see red. > if she exercises her knowledge by stimulating her optic nerves Which, since she has complete knowledge of all physical facts, she can do. The thought experiment does not say she "reads about" color vision. It says she has complete knowledge of all physical facts. The article referenced here does not do a good job of describing Jackson's actual thought experiment, but Jackson's actual thought experiment is based on the (extremely strong and unrealistic) premise I have just stated. It has to be, because any weaker premise cannot possibly ground a conclusion that Mary learns something non-physical when she sees the apple. Just saying that Mary knows everything that can be learned by reading about things is not enough; there are many physical facts that cannot be learned by reading.
  - the_af 4y ago
    It's not circular reasoning: it's a rejection of the premise which I can easily dispute: knowing everything there is to know about sex without actually practicing it is not the same as having sex. If someone subjected a brain in a vat with electrical stimulation to make it believe it's having sex (with phantom body parts it doesn't actually possess), then that is indistinguishable from actual sex -- but note how the postulation of the actual Mary experiment steers clear of actually asserting this, and instead claims she "learns the physical properties" of seeing colors. I realize Jackson is a professor and I'm not, and that this is a well known thought experiment, but I deem it so obviously invalid -- or rather, based on false premises -- that it's not worth considering. Of course I'm basing my opinion on TFA, but reading Wikipedia's summary I see other philosophers have poked holes on this experiment and even agree with me the premises are false. P.S. defining "knowing everything there is to know" the same as "physically experiencing" is circular reasoning, and I definitely disagree with this premise.
    - pdonis 4y ago
      > knowing everything there is to know about sex without actually practicing it is not the same as having sex. Your premise only seems plausible as you state it because you are not actually considering the implications of knowing everything there is to know about sex. But knowing everything there is to know about sex includes knowing what it is like to have sex. So the real premise you should be stating is that it is not possible to know everything there is to know about sex if you have not actually had sex. And, as you appear to realize, making the appropriate adjustment in how the premise of Jackson's Mary thought experiment is interpreted makes it obvious that the argument is invalid--and I agree that it is.
      - the_af 4y ago
        Ah, thanks for the explanation. Yes, reading this answer and also your more elaborate reply to another commenter, I think I agree.
naasking 4y ago
> That includes the knowledge of how to cause her optical/neural pathways to be excited in the particular way that corresponds to "seeing red" even without the corresponding external stimuli being present. Yes, Mary would have the knowledge of how to perform surgery on herself to stimulate her brain or optic nerves in the right way to generate the necessary experience. I don't think that's within bounds of the thought experiment though. The thought experiment is testing our intuition about whether third-party objective facts, as found in science, can suffice to describe even subjective experiences like redness. If you need to actually stimulate the experience to gain that understanding, then that either proves that third-party objective facts are not sufficient, or it proves that such experiences are not knowledge. That's one standard response: knowledge and ability are not equivalent. Someone who had their legs amputated ostensibly knows how to walk but lacks the ability to do so. In principle, no amount of knowledge by itself will make you walk, but knowledge can give you back the ability to walk, ie. a gene therapy with stem cells to grow back limbs, prosthetics, etc. So the idea is that experiencing redness is not knowledge but an ability you acquire by exposure to colours: https://en.wikipedia.org/wiki/Knowledge_argument#Ability_hypothesis https://en.wikipedia.org/wiki/Knowledge_argument#Ability_hyp...
- pdonis 4y ago
  > I don't think that's within bounds of the thought experiment though. Why not? The point of the thought experiment is supposed to be to prove that Mary learns something she didn't know before when she sees the apple. But if the premises of the thought experiment give her the ability to give herself that knowledge beforehand, that undermines the conclusion. > The thought experiment is testing our intuition about whether third-party objective facts, as found in science, can suffice to describe even subjective experiences like redness. No, it's not. It's claiming to prove that subjective experience cannot be physical, i.e., that physicalism is false. It is making use of a common intuition that subjective experiences are fundamentally different from "third-party objective facts" (Dennett calls it an "intuition pump" for this reason), but that is not a proof of anything, it's just a circular argument, assuming what it purports to prove. > If you need to actually stimulate the experience to gain that understanding, then that either proves that third-party objective facts are not sufficient, or it proves that such experiences are not knowledge. Neither one of these refutes physicalism, however, since the process of giving yourself the required stimulus based on your knowledge is a physical process--at least, there is nothing in the premises of the thought experiment that rules that out.
the_af 4y ago
I absolutely have a problem with considering "imagining" (especially something you've never experienced before) the same as "experiencing". I'm sorry, but giving Mary such superpowers completely invalidates the experiment for me. It sounds too much of the old Maths joke: "let's consider a spherical cow."
- pdonis 4y ago
  > giving Mary such superpowers completely invalidates the experiment for me This complaint should be addressed, not to me, but to Jackson, whose premise for the thought experiment gives Mary such "superpowers". I agree that such a premise is completely unrealistic and invalidates the thought experiment. Unfortunately many philosophers do not appear to have gotten the memo.

by pdonis 4y ago

the_af 4y ago

> That includes the knowledge of how to cause her optical/neural pathways to be excited in the particular way that corresponds to "seeing red" even without the corresponding external stimuli being present. Having knowledge and actually doing it are trivially different things (try sex: knowledge of sex and doing the deed are vastly different things). Now, if she exercises her knowledge by stimulating her optic nerves, that's the same as seeing the apple. But that's not just "reading about it", it's a physical act of doing!

pdonis 4y ago
> Having knowledge and actually doing it are trivially different things This is a circular argument. You are arguing that Mary does not know what it is like to see red by assuming that she does not know what it is like to see red. > if she exercises her knowledge by stimulating her optic nerves Which, since she has complete knowledge of all physical facts, she can do. The thought experiment does not say she "reads about" color vision. It says she has complete knowledge of all physical facts. The article referenced here does not do a good job of describing Jackson's actual thought experiment, but Jackson's actual thought experiment is based on the (extremely strong and unrealistic) premise I have just stated. It has to be, because any weaker premise cannot possibly ground a conclusion that Mary learns something non-physical when she sees the apple. Just saying that Mary knows everything that can be learned by reading about things is not enough; there are many physical facts that cannot be learned by reading.
- the_af 4y ago
  It's not circular reasoning: it's a rejection of the premise which I can easily dispute: knowing everything there is to know about sex without actually practicing it is not the same as having sex. If someone subjected a brain in a vat with electrical stimulation to make it believe it's having sex (with phantom body parts it doesn't actually possess), then that is indistinguishable from actual sex -- but note how the postulation of the actual Mary experiment steers clear of actually asserting this, and instead claims she "learns the physical properties" of seeing colors. I realize Jackson is a professor and I'm not, and that this is a well known thought experiment, but I deem it so obviously invalid -- or rather, based on false premises -- that it's not worth considering. Of course I'm basing my opinion on TFA, but reading Wikipedia's summary I see other philosophers have poked holes on this experiment and even agree with me the premises are false. P.S. defining "knowing everything there is to know" the same as "physically experiencing" is circular reasoning, and I definitely disagree with this premise.
  - pdonis 4y ago
    > knowing everything there is to know about sex without actually practicing it is not the same as having sex. Your premise only seems plausible as you state it because you are not actually considering the implications of knowing everything there is to know about sex. But knowing everything there is to know about sex includes knowing what it is like to have sex. So the real premise you should be stating is that it is not possible to know everything there is to know about sex if you have not actually had sex. And, as you appear to realize, making the appropriate adjustment in how the premise of Jackson's Mary thought experiment is interpreted makes it obvious that the argument is invalid--and I agree that it is.
    - the_af 4y ago
      Ah, thanks for the explanation. Yes, reading this answer and also your more elaborate reply to another commenter, I think I agree.

naasking 4y ago

> That includes the knowledge of how to cause her optical/neural pathways to be excited in the particular way that corresponds to "seeing red" even without the corresponding external stimuli being present. Yes, Mary would have the knowledge of how to perform surgery on herself to stimulate her brain or optic nerves in the right way to generate the necessary experience. I don't think that's within bounds of the thought experiment though. The thought experiment is testing our intuition about whether third-party objective facts, as found in science, can suffice to describe even subjective experiences like redness. If you need to actually stimulate the experience to gain that understanding, then that either proves that third-party objective facts are not sufficient, or it proves that such experiences are not knowledge. That's one standard response: knowledge and ability are not equivalent. Someone who had their legs amputated ostensibly knows how to walk but lacks the ability to do so. In principle, no amount of knowledge by itself will make you walk, but knowledge can give you back the ability to walk, ie. a gene therapy with stem cells to grow back limbs, prosthetics, etc. So the idea is that experiencing redness is not knowledge but an ability you acquire by exposure to colours: https://en.wikipedia.org/wiki/Knowledge_argument#Ability_hypothesis https://en.wikipedia.org/wiki/Knowledge_argument#Ability_hyp...

pdonis 4y ago
> I don't think that's within bounds of the thought experiment though. Why not? The point of the thought experiment is supposed to be to prove that Mary learns something she didn't know before when she sees the apple. But if the premises of the thought experiment give her the ability to give herself that knowledge beforehand, that undermines the conclusion. > The thought experiment is testing our intuition about whether third-party objective facts, as found in science, can suffice to describe even subjective experiences like redness. No, it's not. It's claiming to prove that subjective experience cannot be physical, i.e., that physicalism is false. It is making use of a common intuition that subjective experiences are fundamentally different from "third-party objective facts" (Dennett calls it an "intuition pump" for this reason), but that is not a proof of anything, it's just a circular argument, assuming what it purports to prove. > If you need to actually stimulate the experience to gain that understanding, then that either proves that third-party objective facts are not sufficient, or it proves that such experiences are not knowledge. Neither one of these refutes physicalism, however, since the process of giving yourself the required stimulus based on your knowledge is a physical process--at least, there is nothing in the premises of the thought experiment that rules that out.

the_af 4y ago

I absolutely have a problem with considering "imagining" (especially something you've never experienced before) the same as "experiencing". I'm sorry, but giving Mary such superpowers completely invalidates the experiment for me. It sounds too much of the old Maths joke: "let's consider a spherical cow."

pdonis 4y ago
> giving Mary such superpowers completely invalidates the experiment for me This complaint should be addressed, not to me, but to Jackson, whose premise for the thought experiment gives Mary such "superpowers". I agree that such a premise is completely unrealistic and invalidates the thought experiment. Unfortunately many philosophers do not appear to have gotten the memo.