4 ms·

I don't understand how the thought experiment isn't simply begging the question. It states in its premises that (A) Mary already has all physical knowledge and

by fenomas 12y ago

I don't understand how the thought experiment isn't simply begging the question. It states in its premises that (A) Mary already has all physical knowledge and (B) she later gains new knowledge. If the conclusion (that not all knowledge is physical) wasn't true, the premises could not be consistent. Am I missing something obvious? Why should we accept that the conclusion is true, rather than discarding one of the premises?

tjradcliffe 12y ago
Philosophers typically assume certain "fixed points" in arguments that they then refuse to budge from under any circumstances. It is a mental dysfunction, a kind of inbuilt rigidity of mind, that is peculiar to the breed. For example, there is an actual argument in the philosophy of science that is based on the supposition that there is a substance that is "identical to water in every respect" but "is not H2O but rather XYZ". Philosophers take this "argument" quite seriously, and get rather testy when you point out that the premise is a contradiction: if something has "all the properties of water", then that must include properties under electrolysis, and under electrolysis water decomposes to 2H and O, not X, Y and Z (whatever those might be). If you say this to a philosopher they will reply, "Yes, but what if it doesn't?" as if that was a coherent statement. So the answer to your question is, "Because if we allowed ourselves to discard one of the premises we'd have a much harder time motivating this whole ridiculous discussion, and since our livelihood depends on such ridiculous discussions, we're not about to let that happen!"
- Rangi42 12y ago
  Without disputing your main point about how philosophers typically behave, I want to clarify the is-water-H2O argument. As I understand it, it's making a point about how we use language: people have been using the word "water" to refer to various puddles, lakes, oceans, beverages, etc for a long time before electrolysis was discovered. We know now that all those instances have being-H2O in common, but it's not a necessary property for the word "water" to apply: if some other chemical fulfilled the everyday requirements for water (being clear, wet, thirst-quenching, etc) without being H2O, it would be "water," and if a particular variation of H2O doesn't fulfill those requirements (^2H2O, heavy water, is poisonous) then it's not water. See "Water is Not H2O" (Michael Weisberg, 2003). http://www.phil.upenn.edu/~weisberg/papers/waterfinal.pdf http://www.phil.upenn.edu/~weisberg/papers/waterfinal.pdf
  - mannykannot 12y ago
    I have a suspicion that many philosophical arguments, probably including the knowledge argument, are ultimately about language use - in this case, words and phrases like 'knowledge', 'physical' and 'physical knowledge'. Is this what Wittgenstein was going on about?
- raincom 12y ago
  Yes, philosophers have such arguements: Water on some alternative universe without H2O structure vs water on our earth with H2O structure. Even here, the issues are related to metaphysics, not so much about chemistry:) There is a jump from empirical world (the world we are in) to possible worlds. Here is the article: Is water necessarily identical to H2O, by David Barnett http://spot.colorado.edu/~barnetdb/my_papers/Barnett_Water.pdf http://spot.colorado.edu/~barnetdb/my_papers/Barnett_Water.p...
- fenomas 12y ago
  > "Because if we allowed ourselves to discard one of the premises we'd have a much harder time motivating this whole ridiculous discussion, and since our livelihood depends on such ridiculous discussions, we're not about to let that happen!" So saith the Amalgamated Union of Philosophers, Sages, Luminaries, and Other Professional Thinking Persons, eh?
tunesmith 12y ago
This seems to be more about a limitation of language than a problem with the logic. Using "knowledge" in both premises looks clumsy. But looking at it purely conceptually, where Mary would intellectually understand the complete theory in the B&W room, and then gain new experiential insight when leaving the room, it seems to at least prove that experiential knowledge is inherently different than theoretical knowledge. That's more what confuses me about the structure of this argument, though - I would take the experiential insight to be more "physical". So I still don't understand what they mean by physicalism.
- meric 12y ago
  If Mary only knows about colours "intellectually" then she might be a SHRDLU for colour, knowing the calculations of blocks symbolically but not knowing blocks and gravity, having never experienced it. http://hci.stanford.edu/winograd/shrdlu/ http://hci.stanford.edu/winograd/shrdlu/
jordonwii 12y ago
That's exactly the point - she has all physical information. If you could show that some piece of information fits the definition of "physical information", then it's assumed that Mary has it, and someone defending the knowledge argument would have to agree. The point is that even IF you give Mary all that information, she's still missing some information. Then, that information must not be physical information. More to the point, there's a difference between the points you presented: In (A), you say Mary has all _physical_ knowledge (Jackson uses the word information, but the difference is unimportant). In (B), you note that she gets new _knowledge_. It follows that this knowledge must be non-physical, since we assumed that she had all physical knowledge, and yet, she didn't have this new knowledge.
- thaumaturgy 12y ago
  But this looks identical to the "immovable object vs. unstoppable object" paradox. It presupposes something that doesn't actually exist. Experience is information. It doesn't make sense to imagine a situation in which she has all the information about a thing, except experience. Either she has all of the information about it, or she doesn't.
  - jordonwii 12y ago
    Let's take the claim "experience is information" to be true (I've yet to find a reasonable definition of "information", so I agree). Jackson's point here is specifically to show that there are at least two kinds of information: physical information, and information that is not physical. Bearing that in mind, what do you mean by: > "Either she has all of the information about it, or she doesn't."
    - thaumaturgy 12y ago
      What I mean is that all information is physical information -- I'm rejecting outright his starting premise, because no amount of research on wavelengths or poetry will excite the exact same neurons in your brain that are excited by actually seeing a color. I suppose that my objection falls under 4.2 in http://plato.stanford.edu/entries/qualia-knowledge/ http://plato.stanford.edu/entries/qualia-knowledge/, specifically, metaphysical physicalism: "there are no non-physical individuals, properties or relations and no non-physical facts". What would be a good example of non-physical information?
sooheon 12y ago
If Mary is never allowed to actually see the colour of objects in her room, she is being deprived of a physical fact regarding colour vision, and premise 1 doesn't stand. Put another way, how is Mary's later epiphany to be induced in her but by physical means? She must physically experience (photons in eyeballs) colour.

by fenomas 12y ago

tjradcliffe 12y ago

Philosophers typically assume certain "fixed points" in arguments that they then refuse to budge from under any circumstances. It is a mental dysfunction, a kind of inbuilt rigidity of mind, that is peculiar to the breed. For example, there is an actual argument in the philosophy of science that is based on the supposition that there is a substance that is "identical to water in every respect" but "is not H2O but rather XYZ". Philosophers take this "argument" quite seriously, and get rather testy when you point out that the premise is a contradiction: if something has "all the properties of water", then that must include properties under electrolysis, and under electrolysis water decomposes to 2H and O, not X, Y and Z (whatever those might be). If you say this to a philosopher they will reply, "Yes, but what if it doesn't?" as if that was a coherent statement. So the answer to your question is, "Because if we allowed ourselves to discard one of the premises we'd have a much harder time motivating this whole ridiculous discussion, and since our livelihood depends on such ridiculous discussions, we're not about to let that happen!"

Rangi42 12y ago
Without disputing your main point about how philosophers typically behave, I want to clarify the is-water-H2O argument. As I understand it, it's making a point about how we use language: people have been using the word "water" to refer to various puddles, lakes, oceans, beverages, etc for a long time before electrolysis was discovered. We know now that all those instances have being-H2O in common, but it's not a necessary property for the word "water" to apply: if some other chemical fulfilled the everyday requirements for water (being clear, wet, thirst-quenching, etc) without being H2O, it would be "water," and if a particular variation of H2O doesn't fulfill those requirements (^2H2O, heavy water, is poisonous) then it's not water. See "Water is Not H2O" (Michael Weisberg, 2003). http://www.phil.upenn.edu/~weisberg/papers/waterfinal.pdf http://www.phil.upenn.edu/~weisberg/papers/waterfinal.pdf
- mannykannot 12y ago
  I have a suspicion that many philosophical arguments, probably including the knowledge argument, are ultimately about language use - in this case, words and phrases like 'knowledge', 'physical' and 'physical knowledge'. Is this what Wittgenstein was going on about?
raincom 12y ago
Yes, philosophers have such arguements: Water on some alternative universe without H2O structure vs water on our earth with H2O structure. Even here, the issues are related to metaphysics, not so much about chemistry:) There is a jump from empirical world (the world we are in) to possible worlds. Here is the article: Is water necessarily identical to H2O, by David Barnett http://spot.colorado.edu/~barnetdb/my_papers/Barnett_Water.pdf http://spot.colorado.edu/~barnetdb/my_papers/Barnett_Water.p...
fenomas 12y ago
> "Because if we allowed ourselves to discard one of the premises we'd have a much harder time motivating this whole ridiculous discussion, and since our livelihood depends on such ridiculous discussions, we're not about to let that happen!" So saith the Amalgamated Union of Philosophers, Sages, Luminaries, and Other Professional Thinking Persons, eh?

tunesmith 12y ago

This seems to be more about a limitation of language than a problem with the logic. Using "knowledge" in both premises looks clumsy. But looking at it purely conceptually, where Mary would intellectually understand the complete theory in the B&W room, and then gain new experiential insight when leaving the room, it seems to at least prove that experiential knowledge is inherently different than theoretical knowledge. That's more what confuses me about the structure of this argument, though - I would take the experiential insight to be more "physical". So I still don't understand what they mean by physicalism.

meric 12y ago
If Mary only knows about colours "intellectually" then she might be a SHRDLU for colour, knowing the calculations of blocks symbolically but not knowing blocks and gravity, having never experienced it. http://hci.stanford.edu/winograd/shrdlu/ http://hci.stanford.edu/winograd/shrdlu/

jordonwii 12y ago

That's exactly the point - she has all physical information. If you could show that some piece of information fits the definition of "physical information", then it's assumed that Mary has it, and someone defending the knowledge argument would have to agree. The point is that even IF you give Mary all that information, she's still missing some information. Then, that information must not be physical information. More to the point, there's a difference between the points you presented: In (A), you say Mary has all _physical_ knowledge (Jackson uses the word information, but the difference is unimportant). In (B), you note that she gets new _knowledge_. It follows that this knowledge must be non-physical, since we assumed that she had all physical knowledge, and yet, she didn't have this new knowledge.

thaumaturgy 12y ago
But this looks identical to the "immovable object vs. unstoppable object" paradox. It presupposes something that doesn't actually exist. Experience is information. It doesn't make sense to imagine a situation in which she has all the information about a thing, except experience. Either she has all of the information about it, or she doesn't.
- jordonwii 12y ago
  Let's take the claim "experience is information" to be true (I've yet to find a reasonable definition of "information", so I agree). Jackson's point here is specifically to show that there are at least two kinds of information: physical information, and information that is not physical. Bearing that in mind, what do you mean by: > "Either she has all of the information about it, or she doesn't."
  - thaumaturgy 12y ago
    What I mean is that all information is physical information -- I'm rejecting outright his starting premise, because no amount of research on wavelengths or poetry will excite the exact same neurons in your brain that are excited by actually seeing a color. I suppose that my objection falls under 4.2 in http://plato.stanford.edu/entries/qualia-knowledge/ http://plato.stanford.edu/entries/qualia-knowledge/, specifically, metaphysical physicalism: "there are no non-physical individuals, properties or relations and no non-physical facts". What would be a good example of non-physical information?

sooheon 12y ago

If Mary is never allowed to actually see the colour of objects in her room, she is being deprived of a physical fact regarding colour vision, and premise 1 doesn't stand. Put another way, how is Mary's later epiphany to be induced in her but by physical means? She must physically experience (photons in eyeballs) colour.