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> 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

> 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.
- naasking 4y ago
  > But if the premises of the thought experiment give her the ability to give herself that knowledge beforehand, that undermines the conclusion. No it doesn't, it's called the Knowledge Argument because the knowledge of redness purportedly does not deductively follow from the knowledge of any amount of physical facts. It requires non-deductive steps, like surgery and brain stimulation in this case. You might as well say that Mary could construct a red LED and gain the knowledge of redness that way, because that too is a physical process. That's obviously out of bounds, and surgery is the same type of invalid move. Edit: > 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. Under dualism, physical processes are correlated with non-physical qualia, so triggering the physical process in a roundabout way is not a valid move here. The question being tested is whether knowledge of redness follows from knowledge of all other physical facts, not whether knowledge of redness follows from triggering a physical process because we already know that does.
  - pdonis 4y ago
    > the knowledge of redness purportedly does not deductively follow from the knowledge of any amount of physical facts. Which is just a bare assertion, not an argument. Nothing in the premises of Jackson's thought experiment entails this or requires it. To a physicalist, knowledge of redness is knowledge of a physical fact, so this statement is simply false. > surgery is the same type of invalid move If you're hung up on the word "surgery", then eliminate it: it's just as possible that Mary could simply imagine, based on her complete knowledge of all physical facts, what it would be like for her to see red, without having to do any surgery at all. You might say this is implausible, but so is the premise that Mary has complete knowledge of all physical facts. But that's the premise of the thought experiment. > Under dualism Jackson's thought experiment does not prove that dualism must be true. Nor can you assume that dualism is true as a premise, since that is just a circular argument. A physicalist, like me, simply does not think dualism is true, and it is no argument against that to show what would be the case if dualism were true. You need to argue, from premises that don't already contain dualism, that dualism must be true. Jackson didn't do that. Nor do any of the other arguments described in the article, including the Knowledge Argument.

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.

naasking 4y ago
> But if the premises of the thought experiment give her the ability to give herself that knowledge beforehand, that undermines the conclusion. No it doesn't, it's called the Knowledge Argument because the knowledge of redness purportedly does not deductively follow from the knowledge of any amount of physical facts. It requires non-deductive steps, like surgery and brain stimulation in this case. You might as well say that Mary could construct a red LED and gain the knowledge of redness that way, because that too is a physical process. That's obviously out of bounds, and surgery is the same type of invalid move. Edit: > 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. Under dualism, physical processes are correlated with non-physical qualia, so triggering the physical process in a roundabout way is not a valid move here. The question being tested is whether knowledge of redness follows from knowledge of all other physical facts, not whether knowledge of redness follows from triggering a physical process because we already know that does.
- pdonis 4y ago
  > the knowledge of redness purportedly does not deductively follow from the knowledge of any amount of physical facts. Which is just a bare assertion, not an argument. Nothing in the premises of Jackson's thought experiment entails this or requires it. To a physicalist, knowledge of redness is knowledge of a physical fact, so this statement is simply false. > surgery is the same type of invalid move If you're hung up on the word "surgery", then eliminate it: it's just as possible that Mary could simply imagine, based on her complete knowledge of all physical facts, what it would be like for her to see red, without having to do any surgery at all. You might say this is implausible, but so is the premise that Mary has complete knowledge of all physical facts. But that's the premise of the thought experiment. > Under dualism Jackson's thought experiment does not prove that dualism must be true. Nor can you assume that dualism is true as a premise, since that is just a circular argument. A physicalist, like me, simply does not think dualism is true, and it is no argument against that to show what would be the case if dualism were true. You need to argue, from premises that don't already contain dualism, that dualism must be true. Jackson didn't do that. Nor do any of the other arguments described in the article, including the Knowledge Argument.