I'm leaving for a week in the backwoods, so it will be more like next week before I reply, as there are many things here to correct.

One thing I did notice immediately, however, is that you have not yet given a clear and coherent explanation of what you mean when you use 'identifiable' / 'identified by', even though you use the term in a new premise. If you could do that, it would be helpful - for one thing, no-one should accept any premise containing the term, without there being a clear understanding of what it means.

I see that you still have no clear idea what my argument is, largely, it seems, as a result of your attempts to paraphrase it into something that you can dispute. I will reply with a lot more detail, but as I am off on a trip to the backwoods, that probably will not be until sometime next week.

 
firstly. let me say that I have come to agree with you that I should say something about what physicalists assume about color vision, though it will not - and need not - be a complete explanation of how it works. I will say more on that below, in replying to your second post of this series.

Your claim that "the only acceptable premise to add to an argument that is presented as a complete argument is a premise that is hidden" only applies if it is being claimed that the resulting argument is effectively the same as the original. Any modification to an argument can be seen as creating a new one, and one can use any premises in a new one. In this case, I am creating a new argument, for the conclusion that at time t1, Mary already knows everything that could otherwise be learned from seeing a red thing for the first time.

This argument has several features of interest. Firstly, it contradicts your premise 7, and as such, it stands as a counter-argument: This argument and yours cannot both be valid and sound. So how could you show that this new one is either invalid or unsound?

This is another of its interesting points: except for one premise and two deductions, it is taken directly from your argument. If you could show that those parts are invalid or unsound, that would apply equally to your argument.

That leaves you with a few options. You could show it to be invalid by showing that lemma 5.1 (everything that anyone could know about color vision is discursively learnable) or conclusion 7.1 (at time t1, Mary already knows everything that could otherwise be learned from seeing a red thing for the first time) do not follow from the premises, but so far, you have not.

Your only other option is to show that the new premise (everything that anyone could know about color vision is physically-encodable) is unsound. You cannot simply say that your argument shows this to be so, as then your argument would be circular: "your argument against my argument fails, because my argument shows that your premise does not hold!" You could simply deny, without offering any additional argument, that my premise is false, but now we get to the third interesting point: this premise is the antithesis of your conclusion[1]. Therefore, you would be begging the question if you just did that. What else is there? That is the question I have been asking.

This is unlike your proof-of-God example, where the reply technically is a counter-argument, but not a useful one, as it does nothing more than deny the conclusion. While the only new premise I have introduced does that, I use several additional premises to show that your argument is not valid as it stands. 


 
Let's follow Douglas Hofstadter's advice, and 'twiddle the knobs' on your tree-ring example.

When your subject discovers the tree trunk, no knowledge about its age can be learned discursively. It only becomes so once your subject has processed it, together with additional information that cannot be derived from the trunk. Note that a person who did not know the origin of tree rings would not form the proposition that the tree had survived 70 seasons of growth, and would not be able to communicate this fact (unless it was learned another way, which would be beside the point.) 

Before any of that happens, the rings have to be perceived, which requires a modulated reflection of the light falling on it, stimulation of the viewer's receptor cells, and neural processing of the resulting signals.

Some of the physical changes in the neural system will be persistent, at least if the viewer has any memory at all of seeing the trunk. Let's call the physical state resulting from these changes due to perceiving the tree rings P (note that the physical state P is unique to each individual, as they have physically different brains simply as a result of not being made from the same atoms.). A physicalist can reasonably propose that P is essential to the subject knowing what it is like to perceive the rings.

Getting to the discursively-learnable proposition that "this tree has survived 70 seasons of growth" requires additional processing, which, for the first time, requires linguistic abilities, which are known to be located in a different region of the brain than visual processing. This will result in some additional state changes within the viewer's brain, and we can call the physical state resulting from these changes L. Note that the person who does not know the cause of tree rings does not form the proposition, and does not enter her version of state L, yet presumably does know what it is like to see the rings. Consequently, we can conclude that knowing this discursively-learnable knowledge is not necessary for knowing what it is like to see the rings.

(As it happens, one of Churchland's arguments for non-propositional qualia is that many animals lacking linguistic abilities can be shown to perceive, remember and compare colors (including to memories of colors), all without contemplating any propositions whatsoever.) 

Regardless of how many ways this discursively-learnable information is the same as that encoded in the trunk's state, it is not identical to the latter information in at least three ways: 1) it is encoded as a physical state in the observer's brain, not a physical state of the trunk; 2) unlike the information in the trunk, it is the information content of someone's knowledge; 3) the trunk can be destroyed, while the observer continues to know something about its age when it fell.

Now let's introduce Mary, who knows all of completed physics. She has not seen the trunk, but has been given a complete physical description of it (there is no doubt that the physical description is communicable, and, in fact, it would be part of her complete knowledge of physics, which she has learned discursively.) From this description, she could deduce that the trunk has 70 rings, and, with the additional knowledge about the origin of tree rings (which is also part of her complete physical knowledge), she could achieve physical state L by deducing the discursively-learnable proposition that the tree has survived 70 seasons of growth.

Let's assume she can also deduce what her state P would be if she had seen the tree trunk, and give a description of it. In synthesising that description, she undergoes a third set of state changes, to state D, encoding (among other things) the propositions comprising the description of the state P. That state is not P itself.

To get to state P from this description of state P, Mary would need to target the specific neurons and synapses involved in P, and produce in them specific state changes. This would require a degree of connectedness and influence that certainly is not necessarily so, and has never been demonstrated to science (can you do it?) We cannot even just get the state of specific synapses, let alone change them.

And if we think that her total knowledge would give her this ability, then, per Dennett, she could get from D to P and would know what seeing the trunk is like - this is one of the horns of Jackson's dilemma again. In fact, all she would have to do would be to just modify the state of the first layer of neurons that the optic nerve connects to, replicating the effect of seeing the trunk, and so come to know what it is like to see it without having done so.

I don't generally like computer analogies, but there is a very appropriate one here: if I have a secure operating system, it will have plenty of internal-use-only state, and you will be unable to write a program that an unprivileged user could use to modify that state, even if you know everything there is to know about that operating system.

If you have read Curchland's Reply to Jackson, you will recognize this as being very similar in spirit to what he wrote there, and as he said, physicalists do not have to provide a complete and completely accurate account of vision in order to show that, quite plausibly, there is an entirely physical explanation for Mary not learning everything from her studies, even though she has full knowledge of physics (which is not the same as having all physically-encoded knowledge.) So long as this goes unanswered, Jackson's argument fails to make its case.

If it is the case that many philosophers, including many physicalist ones, hold that all information content is identifiable by sets of propositions (what, precisely, does 'identifiable by' mean?) then that might explain the popularity of 'old knowledge seen in a new way' replies to Jackson, which seem to me to be wrestling with a problem that has a much simpler answer. So long as philosophers like the Curchlands and Dennett are unconvinced by this view, I am not convinced that I am overlooking something obvious - and if I am, it should be easy to show that I am doing so, without appealing to authority.



This is all covered above - in particular, see the bit about circularity.



Again, see the above. It seems to me that your metaphysical claim is merely avoiding pertinent issues raised by Churchland and others. Metaphysical arguments have to make their case, just like any other.

---------------------------------------------------

[1] I did not actually write "it is not the case that what Mary learns is not physically encodeable", but your  conclusion does not actually refute either physicalism, or Churchland's reply, if she doesn't learn anything about color vision at t1. The conclusion you need here is something equivalent to what Jackson said, such as "at t1, Mary learns something that is not physically encodable." Of course, in your argument, you can get there directly by using premise 7, but I can also get to its antithesis directly from my conclusion that Mary does not learn anything at time t1.

There is nothing wrong with introducing a new premise into a discussion. If doing so were wrong, then we should reject your introduction, in your latest argument, of several premises that you had not raised in previous posts. Furthermore, in this case, premise 0 (the only additional premise; all the rest are yours) is not just any premise, it is the antithesis of your conclusion.

Of course, you would not want to accept premise 0 in any argument, but that is beside the point, as the purpose of debate in the search for knowledge is to persuade third parties of certain things (and even if you were to claim that you are arguing only for yourself, it would then be inconsistent with that claim to object to anyone else adopting any premise; furthermore, you would be in great jeopardy of fooling yourself if you did not examine your argument as a skeptic would.) The point is that you cannot simply reject the skeptic's assumption of the antithesis of your argument without begging the question.

As for your objection that this goes beyond your initial limited claims against Churchland's reply to Jackson, it would be inconsistent for you to do what you are doing - trying repeatedly to find an argument that holds up - while insisting that I must stick with only my first presentation of Churchland's argument (if the latter rule were applied consistently, there would be no debate about anything!) It would also be a contradiction to say that your latest argument is on-topic, while attempts to refute it are off-topic.

Your final argument has not removed the Churchland-Crane charge of equivocation, at least until you deal with the argument in my other reply above.

You seem to be under the impression that I am implying that premise 7 must be false, but the point here is, instead, that if your argument, for the proposition that all knowledge having physically-encodable information content is discursively-learnable, holds, then what non- question-begging reply do you have to the claim that Mary could have learned everything beforehand? One does not have to deny 7 to see that this is a problem for your argument.

Saying that premise 7 is just an intuition is not a get-out-of-jail card, logically speaking, as it does nothing to fix this problem. Also (somewhat unintuitively, perhaps), the reasons why one might believe any premise are not germane to validity. 

Far from the physicalist being pushed into the corner of of rejecting the claim that Mary learns anything new, you are in the corner of having not yet given a non- question-begging reply to the problem of why Mary was unable to learn it before t1. That, of course, was in my original presentation of the Churchland/Crane reply to Jackson, so all the stuff about not addressing your original claim is beside the point, even if it were valid.

For reference, here is the counter-argument (points 1-7 copied from your original):

[0]: Everything that anyone could know about color vision is physically-encodable.  
[1]: All information content that is encodeable is expressable as a finite set of propositions.
[2]: Any finite set of propositions is discursively learnable.
[3]: From 1 and 2; all information content that is encodeable is discursively learnable.
[4]: Anything that is physically encodeable is information content that is encodeable.
[5]: From 3 and 4 anything that is physically encodeable is discursively learnable.
[5.1]: From 0 and 5, everything that anyone could know about color vision is discursively learnable.
[6]: At time t, Mary knows everything that is discursively learnable.
[7.1]: From 5.1 and 6, at time t1, Mary already knows everything that could otherwise be learned from seeing a red thing for the first time.

Which contradicts 
[7]: Mary gains new knowledge when at t1 she sees a red thing for the first time.

As noted above, this does not necessarily imply that 7 is false, just that not all of the above can hold together.

There is alternative way of looking at your argument, by introducing premise 0: Everything that anyone could know about color vision is physically-encodable.

If we also assume that the argument through point 6 is valid (I am not saying I do!), we can conclude that, contrary to our intuitions, by time t, Mary knows everything that anyone could know about color vision, and therefore premise 7 cannot be added to this argument without invalidating it.

Given that the conclusion being sought here, by yourself and Jackson, is the antithesis of premise 0, it would be begging the question to deny that premise.

 

The SEP is an excellent resource, and in section 2 we have a discussion showing that it is not straightforward to find an inverted spectrum scenario that is clearly behaviorally-invariant (and as we will see, my argument is not defeated by the existence of some scenarios that are.)
— A Raybould
You're confusing your opinion with your argument. The stuff in section 2 is a different argument than what you've presented... — InPitzotl

 
Indeed it is, and on the contrary, you seem to have overlooked (or, as you would put it, "are confused about") the relevance of this issue. It goes back to your attempt to claim that the possibility of behaviorally-invariant inverted spectra somehow invalidated my hypothesis, and I pointed out that mere possibility would not do; at the very least you would have to show actual prevalence. This section shows that, as a matter of fact, undetectable inverted spectra cases are sparse among all possibilities, and an explanation of why they are does not, of course, dispute the fact that they are. 

Furthermore...

some of the arguments in that section are in fact decent and relevant, but they do also presume things about color processing for which we really need more detail... Since these are L1 like properties, inverting the mappings from L1 to L2 colors may still carry these properties — InPitzotl

 
I see that you have no hesitation over needing more details when you wish to speculate on how things might be - but if you want to argue against my hypothesis with a speculation that is consistent with it, but which we would have no justification to believe if the mappings routinely differed between people as a first-order effect, then go ahead!
 
 

"Too vague" seems to have become your default response, but by itself, it is too... vague?
— A Raybould
It's not exactly a default response so much as it is prompted: — InPitzotl

 
On the contrary, as I pointed out in several cases, you have attempted to manufacture that impression by quoting out of context. And so it is here, also; you did not quote the rest of my response here, but only part of it, and elsewhere. For the record, here it is:
 

Are there any non-vague metrics of vagueness, and more-or-less objective thresholds? The falsifiability criterion of science provides one (despite not being directed specifically at vagueness alone), and it is an appropriate one here: Vague claims (such as of vagueness exceeding some unspecified threshold) are not falsifiable.
 
What I am saying here could be falsified; a (not-yet-achieved) causal model of how the human brain produces a mind would reveal whether, to a first-order approximation, most humans are undergoing the same physical functions when they experience color. That's good enough for a hypothesis. — A Raybould

 
 

A more parsimonious expectation, however, is that this multi-generational training has produced brains that function alike, to a first approximation. If they did not, how likely is it that they would have, so to speak, 'learned the lessons' imparted by evolution?
— A Raybould
...in relation to the topic at hand, this is indeed too vague. Your expectation is more parsimonious than what exactly? Function alike in what ways? What "learned lessons"? I'm perfectly happy to say that human brains evolved in human like ways, but that does not really imply same-experience unless you can connect the similarity of human evolution to the similarity of color experience, which I've yet to see. Other than that, it's yet another nature versus nurture debate. Truth is, both nature and nurture make brains, especially human brains. — InPitzotl

Raising questions about specific points, as you have done here, is much more to-the-point than vague claims of vagueness, and I have no problem with answering them. The "learned lessons" are evolutionary adaptations. My expectation is more parsimonious than the hypothesis that first-order differences, between individuals, in their high-level functional responses to color stimuli, are pervasive. It is more parsimonious because the latter has a problem with ensuring that, of all the possible ways that a child might differ from its parents, only the ways that are behaviorally-close seem to arise. As for nature vs. nurture, nurture is not going to 'correct' a child into thinking that her tongue is red if her experiential correlates to how she sees her tongue maps close to those of grass and cucumbers, and distant from those of tomatoes, pimentos, and the setting sun. 

My point is based on empirical fact: if variation is routinely producing children that have markedly different functional responses to color stimuli than their parents, then how come we only very rarely see those variations that do not result in observable differences?
— A Raybould
Because, for example, predators aren't examining your brain with fMRI to see if you represent redness on this spot or that spot or using this average frequency of pulses or that frequency? The important thing from a fitness perspective is that you run away, hide, or fight the predator appropriately. — InPitzotl

 
This is a non-sequitur. There will, in general, be behaviorally-observable consequences if human brains routinely have first-order differences in their functional responses to color stimuli, unless, mysteriously, this variation can only occur in the relatively few ways that are behaviorally inconsequential.
 
 

The alternative is so lacking in plausibility that I will not bother to reply until specific arguments for it are presented.
— A Raybould
That's your choice, but in effect, given that you're the one claiming to be supporting a proposal that the experiential correlates have a fitness advantage, not answering the question absolutely equates to not addressing the very thing your proposal is supposed to be about. If your proposal is about a tie between fitness and particular experiential correlates of color, it is backed if and only if you can demonstrate what it is about... i.e., tie fitness to experiential correlates of color. This is what I mean by relevance [my emphasis.] — InPitzotl

 
Again, some relevant context is missing:

I do not think it is very speculative to say that our mental abilities are strong determinants of fitness (unless, of course, one thinks our experiences are epiphenomenal.)
— A Raybould
 
In what way?
— InPitzotl
 
The alternative is so lacking in plausibility that I will not bother to reply until specific arguments for it are presented. Extraordinary claims require extraordinary evidence. — A Raybould

  
The premise that, in general, brain function is adaptive, is just one premise in my hypothesis. If you want to hang your case on refuting that particular premise, I rest my case!
  
Oh, you're not taking a position on the issue? Well, then I am not putting anything at risk by not responding until it is more than just creationists who are making that claim.
  
As for the italicised statement, this is an inaccurate paraphrase of my position, and therefore not germane. The evolutionary issue is just one point in an argument that involves ontogeny, the mechanism of inheritance, and the scope of variation: it is that if variation routinely produced first-order differences between offspring and their parents, adaptation would not occur.
 
 

For physicalists, where there is no physical difference, there is no difference simpliciter.
— A Raybould
Sure. So let's focus on the correlates, since that's where the difference would be.
And what are those correlates?
— A Raybould
I don't know, but I think that's the key question. In terms of L1 colors, there are reasonable explanations of development that are works in progress but involve self organization; these generally produce opponent color processes. Example:
https://www.frontiersin.org/articles/10.3389/fncir.2014.00016/full
This itself requires a bit more study. In terms of color perception in the brain, as I said before, we know there are multiple places of analysis. But there's also the possibility of potential signal space (such as these toy models of potential Poisson rates)... and since the signals potentially start this way there may be transference from these signal rates to positions, or not. But "qualia" may be more complex than many philosophers tend to treat it as well; e.g., there's such a thing as pain that doesn't hurt, suggesting that qualia aren't necessarily singular in the first place. This might be explained as pain in practice actually having separable pieces that typically are co-associated but not essentially so, and the same could possibly be true of color. What we're looking at developmentally for different-experience would be any sort of theory that starts with this brain in a semi-random developmental state and just "settles into" the "nearest corners".  The entire question here (that has not yet actually been addressed) is how many "corners" are there, why are there that many, and how do the L1 colors map into them? Assuming opponency-sized "corners", a same-experience theory would postulate four to six of them, and some sort of specific developmental pathway whereby particular opponent signals latch into the specific four (or six) that they're supposed to map to.[my emphasis.] — InPitzotl

 
I will just note that this is no less vague than what I have been saying, but only to make a point about your mode of argumentation: what you have said here is perfectly reasonable speculation about how things might be, and it also satisfies the standard of falsifiability.
 
But more substantively, I admit that I am puzzled by why you would think the emphasized sentence would present a problem for my hypothesis - or if it does not, why you think it is relevant. Also, how might the developmental pathway distinguish between the latchings that are supposed to happen and those that are not? Are you  proposing that there could be pervasive first-order differences in how this occurs in most individuals? If not, at what point could these differences manifest themselves?
 
 

What I am saying here could be falsified
— A Raybould
...I'm fine with that, but "adequately justified" is more akin to what you're saying being verified. — InPitzotl

 
Talk about vagueness! I am not convinced that this makes it to the status of being a complete sentence, to the point where I cannot even guess what you mean here.
 
 

Argument and counter-argument are the principal methods of philosophy
— A Raybould
Yes, but counterarguments should not have to require an opposition taking a side to provide the counterarguments, and most certainly should not require the opposition to hold the countering view as an opinion... — InPitzotl

You are not required to take a side, but if anyone floats a putative problem for my hypothesis, then I am, of course, going to probe it regardless of who, if anyone, might hold it. It is not all about you.
 
 

Also, two people discussing a thing need not necessarily each pick a corner and box; it's entirely possible, and may even be more productive, for the two to simply walk hand in hand from corner to corner. — InPitzotl

 
Right at the start of this thread, and subsequently, I have said that we could simply agree to differ. Or we could consider the issue dispassionately, agreeing to differ on how plausible each argument is.
 
 

So, let's get back to tetrachromacy. Let's suppose we introduce a new gene in the human gene pool, call it OPN1MW3. OPN1MW3 expresses in people who have it by producing an M cone with spectral sensitivity shifted towards blue by the same amount (measured in frequency) that M shifts L spectral sensitivity towards blue; let's call this a N cone. This gene is an allele for the M on the X chromosome. So suppose we have: (a) Adam, who has L, M, and S cones; (b) Bill, who has L, N, and S cones; (c) Cindy, who has L, M, N, and S cones. So here are some questions. (a1) Is Adam likely to be a trichromat? (b1) Is Bill? (c1) Is Cindy more likely to be a tetrachromat or a trichromat?
 
(c1) is the interesting question... but regardless of its answer we still have followups. If the developmental process is such that Cindy's likely to become a tetrachromat, then there are questions about what exactly causes the L2 colors that Bill sees; your hypothesis suggests it's some built-in gene, but if self organization suffices to establish L2 colors this is questionable. But if Cindy is only a tetrachromat if she has some other specific gene, some BN (brain-gene-N analog; here, this is just a generic referent... it could be more than one gene), that pre-structures her brain, then we must also ask whether Bill can have that gene as well, or under what conditions precisely Bill sees what Cindy sees that Adam doesn't see.
 
Your hypothesis seems to require a "BM" gene of sorts. Okay, we have the human genome mapped out... so which gene is BM? — InPitzotl

 
Let me just point out here that if this name-the-gene standard of whatever-it-is-that-my-hypothesis-does-not-meet is applied consistently, then a good deal of evolutionary and general biological theory, including the fundamental one that life as we see it today is a result of natural selection, must be thrown out.

More substantively, it is completely unclear to me why my hypothesis requires a BM gene of any sort.
 
 

The point isn't to simply maintain some position with unreasonable standards though. The point is to require relevance. The thing being talked about here is the actual stuff happening between our ears in our soft pink squishy warm brains, that has to do with our subjective conscious experience of colors. Some discussion of and/or constraints on how that subjective experience's correlates develop is necessary to provide a theory of how much the subjective experience's correlates can vary. Without having that discussion or addressing what those constraints are, you're just plain not having the required conversation [my emphasis.] — InPitzotl

 
What I am proposing is precisely that there is a plausible constraint, from empirical facts about biological inheritance and ontogeny, on the degree to which the high-level functional correlates of visual experience can vary between individuals.
 
 

I am guessing that your emphasis on 'established' indicates that you were aware of this, but I had in mind cerebral and congenital achromatopsia and dyschromatopsia, color agnosia
— A Raybould
Achromatopsia and dyschromatopsia are the same modes of L1 level color deficiencies previously discussed (though there are acquired forms). Color agnosia as far as I'm aware is a defect of the ventral stream, which is particularly interesting for awareness of L2 colors at all (if not L2 modes of color at all). I would be interested in an L2 specific defect. — InPitzotl

 
Not that I know of.

I had regarded your focus on L2 as just a case of unnecessary specificity, but when I looked for something justifying this specificity, I did not find any use of L1/L2 terminology with regard to color perception and experience - perhaps you can provide some references, and explain the relevance of your specificity?

While your stated goal, apparently, is to show that the notion that our experiences are similar to a first approximation does not achieve hypothesis-hood
— A Raybould
I've no objection to same-experience as a hypothesis. My objection is claiming that the hypothesis is adequately justified prematurely. — InPitzotl

 
You have always been rather vague about what your objection is. We are in agreement, apparently, that it makes the grade as a falsifiable hypothesis. We are also in agreement, apparently, that it is at least several facts short of a theory. We disagree, apparently, on how plausible it is. On the key issue, however, of whether there is a plausible mechanism, for maintaining the observed first-order similarity between child and parent behavioral similarities, if it is the case that there is little commonality in the functional correlates of their visual experiences, neither of us are aware of one. You also still seem to be arguing against mistaken paraphrases of my argument. I feel that you have not yet made the case that a third party should summarily dismiss this hypothesis.
 
                                                                                                                                             
 
Nevertheless, while I disagree that what I have presented here is too vague to be considered, it could be less vague, especially as my responses to misunderstandings are scattered over several posts. I intend to set it out more precisely, addressing the misunderstandings that have surfaced in this discussion. In doing so, I might come to the conclusion that it is not very plausible, and I will say so if I do.

Therefore, I do not accept this premise, though I will accept this:
You make it sound as though what preceded this sentence was an argument against premise one of my argument, but it was not. All you do is point out a pretty obvious, iterative distinction between a state and its description. — jkg20

I am glad that this, at least, is obvious, but there is an implicit question here: suppose we have some system having information on account of being in physical state ψ. if the corresponding propositions you have in mind are not a description of that state, then what are they? It is far from obvious that such propositions must exist, whether as a consequence of Shannon's information theory or of anything else. As things stand, proposition 1 lacks any justification.

Against premise 4 you state:
I cannot accept this, either, as only a small amount of all physically-encodable information is the information content of knowledge.
But that does not speak to premise 4 at all, within which there is no mention of knowledge, it is a metaphysical, not epistemological premise. — jkg20

Premise 4 is "Anything that is physically encodeable is information content that is encodeable." Given the context, I took "information content" to mean the information content of knowledge. If it is not that, then what is it the content of?

↪A Raybould
(especially given the distinction you made between 'expressible' and 'can be stated' in your previous post.)
That is not the distinction I made. Please reread the post. — jkg20

I did, and I see that it can be read in the light of these being synonyms. I assume, therefore, that you have no objection to 'can be stated' being substituted for 'expressible' everywhere the latter is used in your latest argument?

The claim that Mary learns something from seeing colors is a premise of Jackson's argument, and yours too, if I am not mistaken.
You are mistaken. My argument that you are referring to contained the conditional premise that if one accepts that Mary gains knowledge, then there is an obligation to say something substantive about what she gains. Jackson's argument states that Mary gains knowledge. — jkg20

You say I am mistaken in saying that it is a premise of yours that Mary learns something from seeing colors, but your premise 7 is that "Mary gains new knowledge when at t1 she sees a red thing for the first time." Do you make a distinction between "learns something" and "gains new knowledge"? If so, what is it? Alternatively (or additionally), do you suppose that her new knowledge is not a consequence of seeing red - that these two events are just coincidental? I do not suppose you do, as this latter supposition would invalidate the argument, but I am at a loss for why you think I was mistaken.

Also, note that "new knowledge" is ambiguous here. It is new to Mary, but as Jackson goes to some length to point out, it is not new as in having just become true at t1, as, for his argument to succeed, it must have been a fact that Mary could have learned prior to t1, and one cannot learn non-true facts, as there are no such things. This is the point behind Jackson's insistence that what she learns is a fact that was already true about other people.

As for what you thought I was referring to, your "conditional premise that if one accepts that Mary gains knowledge, then there is an obligation to say something substantive about what she gains": I have said something substantive: either it is discursively-learnable, or it is not. As Jackson's argument fails in either case, a skeptic is under no logical obligation to choose one over the other.

If you think this is insufficient to meet the obligation, then it should be possible for you to show that there is a logical obligation to say more, by showing that the counter-argument is invalid without it. This you have not done.


Now, to your latest argument. There are quite a few claims that I could quibble over, but I will focus on the ones that are decisive.


1: All information content that is encodeable is expressable as a finite set of propositions.

To avoid equivocation later on, we have to be careful here over what it is about the information that is expressible as propositions (especially given the distinction you made between 'expressible' and 'can be stated' in your previous post.) The physical state encoding any specific case of physically-encoded information can be described (in the language of completed physics) but, to be clear, the description is not the state (the map is not the territory), and even though the description may itself be physically-encoded, the physical state in which that description is encoded is not the physical state which is described by that description - for example, the physical state being described can change without the physical state encoding the description changing. Therefore, I do not accept this premise, though I will accept this:

1': The physical states encoding all physically-encoded information can be described in a set of propositions. 


2: Any finite set of propositions is discursively learnable.

I will accept that; as this is a thought experiment, we can put aside the objection that Mary's ability to simply remember propositions is limited.


3: From 1 and 2; all information content that is encodeable is discursively learnable.

Once we substitute 1' for 1, it is clear that this does not follow; the most that one can deduce from 1' and 2 is this:

3': Any description (in the language of physics), of any physically-encoded information content (of someone's knowledge), is discursively-learnable.


4: Anything that is physically encodeable is information content that is encodeable. 

I cannot accept this, either, as only a small amount of all physically-encodable information is the information content of knowledge. For example, the angular momentum of some undiscovered exoplanet encodes some sort of information, but it is not the information content of anyone's knowledge. For a bit of physically-encoded information to be part of the information content of someone's knowledge, it must be encoded by a physical state within that person's brain. If Mary could have knowledge which had its information content encoded in someone else's brain, she would have telepathy, and there would be no justification for the belief that, before seeing colors herself, she could not know what it was like for other people to see colors (this is another manifestation of the dilemma faced by Jackson.)

From here on out (if not before), the deductions fall like a house of cards, and I can no longer even say "here's a valid deduction that is similar in spirit to yours."

In summary, this argument fails because it equivocates between two different things: on the one hand, knowledge of the physical state encoding the information content of some other item of knowledge, and on the other hand, that other item of knowledge itself.

↪A Raybould
 What (if anything) Mary learns from seeing colors is either discursively-learnable or it is not. We can consider these two cases separately.

OK, so this argument puts off the question of accepting whether or not Mary learns anything [my emphasis.] — jkg20

I am puzzled by this. The claim that Mary learns something from seeing colors is a premise of Jackson's argument, and yours too, if I am not mistaken. We only reach the two cases here if that premise holds up; if it does not, the argument has already failed.

I guess against this argument, the skeptic would have to push the investigation of the supposed distinction between knowledge being discursively learnable and knowledge being physically encodeable. — jkg20

It is not clear (at least, to me) to which argument you are referring, or what 'push the investigation' means. The meaning of 'discursively learnable' and 'physically encodable' seem to be straightforward, at least within the context of Jackson's argument:

Discursively-learnable: Knowledge that can be learned by discourse, which is to say linguistic communication [1].

Physically-encodable: Claude Shannon developed the canonical theory of information, in which information is present whenever things are arranged one way when they might be another, and any specific piece of information is encoded in such differences. Physically-encoded information is information that is actually encoded in physical states that might be otherwise - a coin that is heads-up when it might be tails-up, for example - and physically-encodable information is that which could be so encoded. I suppose that any information can be physically-encodable, precisely because the medium of encoding is immaterial (pun intended) to the information content.

So, a premise of the Churchland/Crane/whoever argument is that there is a distinction between knowledge that is discursively learnable and knowledge, the content of which is entirely encodeable in a physical medium. — jkg20

To be clear, the distinction is not one of mutual exclusion; in fact, if all information is physically-encodable, as I suggested above, then discursively-learnable knowledge is a subset of knowledge having physically-encodable information content. The distinction is that they are two different aspects of knowledge.

It seems odd to call this distinction a premise of the argument, as it is just a matter of defining two terms, and it is simply a fact that they have different definitions; furthermore, denying it would not seem to help Jackson's case.

Content is propositional. Even if one accepts the idea of non conceptual content, that is not to accept the idea that there is content that cannot be expressed in terms of propositions, it is just to accept that the person having the mental state with that content need not have the resources to state those propositions. — jkg20

This is a very big assertion, and the justification you offer here does not even begin to do the job. It is not just a possibility, but a fact, that some people have a pathology that prevents them from stating something they know; nevertheless, you cannot deduce that content is propositional from that - it is simply an invalid argument, one for possibility where one for necessity is necessary. As we shall see, it is also moot in this case.

So if all content is propositional, then not only is all discursively learnable knowledge physically encodeable, all physically encodeable knowledge is expressable as propositions and so is discursively learnable[my emphasis] — jkg20

The italicised conclusion does not follow, even if the conditional here were to be true, as, to be discursively-learnable, knowledge must be communicable. For one thing, note that, in what you said to justify saying that all content is propositional, you made the case that people might have propositional knowledge that they cannot state, which would seem to be an insurmountable impediment to it being communicated!

Furthermore, if this argument were valid, then it would apply to all knowledge, not just all physically-encodable knowledge (if there is a difference), and so all knowledge would be discursively-learnable, which is the other horn of the dilemma: In that case, what would have prevented Mary from learning it prior to her release?

the Crane/Churchland line seems to force the skeptic to a position in which they will have to defend the following modus tollens:

1 If some item of knowledge is physically encodeable, then it is discursively learnable

2 The item of knowledge Mary gains is not discursively learnable

_________________________

The item of knowledge Mary gains is not physically encodeable — jkg20

It is not clear to me that anyone has to defend this argument, but, as we have seen above, your current argument for premise 1 does not succeed, even on its own terms. 


[1] On writing this, it occurred to me that it might be disputed whether anything Mary deduces is discursively-learnable. I think it is, because the deduction process itself could be expressed in words and communicated. The issue is moot as far as Jackson's argument is concerned, however, as completed physics already includes everything that can be deduced from other facts - in fact, Jackson stresses this point in his papers, as his argument depends on it.

See section 3: https://plato.stanford.edu/entries/qualia-inverted/ — InPitzotl

The SEP is an excellent resource, and in section 2 we have a discussion showing that it is not straightforward to find an inverted spectrum scenario that is clearly behaviorally-invariant (and as we will see, my argument is not defeated by the existence of some scenarios that are.)


 "Too vague" seems to have become your default response,  but by itself, it is too... vague? Are there any non-vague metrics of vagueness, and more-or-less objective thresholds? The falsifiability criterion of science provides one (despite not being directed specifically at vagueness alone), and it is an appropriate one here: Vague claims (such as of vagueness exceeding some unspecified threshold) are not falsifiable.

What I am saying here could be falsified; a (not-yet-achieved) causal model of how the human brain produces a mind would reveal whether, to a first-order approximation, most humans are undergoing the same physical functions when they experience color. That's good enough for a hypothesis.

For physicalists, where there is no physical difference, there is no difference simpliciter. As I mentioned previously, dualists disagree, but so long as dualism is speculative, it is not enough to rule out my hypothesis: at most, I can restrict it by adding the premise of physicalism, which, despite all efforts, has not been ruled out. And while this is a side-issue, there is nothing more vague than dualists' concepts of the non-physical; there are no hypotheses about how the allegedly non-physical or extra-physical aspects of minds work. As someone who rejects all real and imagined vagueness, you presumably have no truck with dualism.


There are a number of  misunderstandings in your post:

More generally - and I think it covers all the points you have raised here - you are saying that there are cases where disparate experiences would have no observable behavioral effects, and I am saying that nevertheless, there are other cases in which they would
— A Raybould

I agree on that part, but I think you're confused. You specifically asked me for arguments to support that our color experiences were fundamentally different... I provided them [your ellipsis.] — InPitzotl

More specifically, I asked was what objection you had to my reply "not necessarily" to your question "If I experience red a different way than you experience red, wouldn't we still both call red things red?", and your replies only demonstrate possibility where, to be a reply that addresses the evolutionary question, arguments for necessity (or at least predominance) are necessary As far as I can tell, you never did finish the claim you had launched into with that original question.

You have attempted to dismiss this as my attempt to impute attitudes to researchers
— A Raybould

Not exactly... I've pointed out a situation where you're basically guessing researchers share your view and then appealing to the researchers having your view, which is basically an appeal to authority as a fallacy. — InPitzotl

...And it is a claim that you have already been corrected on, and, moreover, right in the part of the quoted sentence you cut out. The full quote is this:

You have attempted to dismiss this as my attempt to impute attitudes to researchers, but itis actually based on the empirical fact that these multiple-subject studies work, and that it is uncontroversial to generalize the results from the studies' subjects to the general population. — A Raybould

 

- no appeal to authority there.

The description here in terms of evolution sounds a bit Lamarckian. — InPitzotl

That puzzled me, but I see that I was not being clear here. I am not saying that a child inherits from its parents' adult minds, complete with what they have learned (that obviously does not happen.) I am only using a completely conventional concept of evolution, and it might help if I go through them one by one:

[1] The brain is predominantly a network of neurons, that has evolved in accordance with current evolutionary theory.
[2] Consequently, and just like any other organ. its architecture, and therefore its function, is not accidental; it is the end result of billions of natural-selection experiments.
[3] At each step of this process (i.e. each generation), the initial state of the organ, and the instructions for its development, are encoded into the genotype and then reconstituted from it.
[4] For evolution to work, there must be some variation between parents and their offspring, but if it is too large and commonplace (beyond second-order), then adaptation will not occur: either the offspring is not viable, or adaptation will be restarting anew with each generation. Empirically, it is not the case that only a few children in each generation have mental abilities (or any other trait) comparable to those of their parents.

If they did not, how likely is it that they would have, so to speak, 'learned the lessons' imparted by evolution?
— A Raybould

Too vague and hand wavy still. — InPitzotl

That might seem to be so, to someone unaware of what I wrote about it immediately afterwards. Once more we see the pattern of quoting out of context. 

As for the paragraph you followed this with, it is all addressed in the above list, which is just a selection of the relevant positions taken in conventional evolutionary theory, with regard to the evolution of any organ, not just the brain. If you like, I could go through how it does so sentence-by-sentence, but I think it would be unnecessary clutter to belabor each point in turn.

If a child's high-level brain function can vary markedly from that of its parents, how likely is it that it would nevertheless still be behaviourally similar enough that the child has approximately the same level of that part of its fitness that comes from its mental abilities?

We're not talking about high level brain functions here. We're talking about the experiential correlate of a color. — InPitzotl

And what are those correlates?

Alternatively, what sort of mechanism would be needed to conserve the external behaviour in the face of internal variation?
— A Raybould

Any isomorphic mechanism would do the trick. Instead of using high and low circuits for 1's and 0's, we could use magnets being in the same or different directions. It doesn't really matter, so long as a change is a change. Instead of encoding y as glucose in the solution we could encode it as maltodextrin. — InPitzotl

I think you are missing the point here. As we have seen, it is not the case that no matter how a child's "experiential correlates" of sensory input differ from those of her parents, it could not have any behavioral consequences. Given the empirical evidence that children and their parents do, to a first approximation, behave similarly with respect to their sensory stimulation (generally agreeing on the categorization of colors, for example (your example, as it happens)), then it seems that, whatever internal correlates they have to those stimuli, they are generally from the subset of possibilities that preserve this commonality of behavioral responses. The question then is, if childrens' internal correlates of stimuli are free to differ markedly from those of their parents, what genetic and ontological mechanism might there be to restrict the variation in the experiential correlates such that the behavioral commonality is preserved?

We cannot depend on evolution doing that, as evolution is itself dependent on the conservation of fitness traits from parent to offspring.
— A Raybould

Evolution is only selecting for fitness where it matters. If a variation does not affect fitness where it matters, evolution would not care about that variation. You're in effect just begging the question; you're assuming that the variations would have an effect on fitness and then arguing that evolution would select those out: — InPitzotl

Not at all - you are arguing against your misunderstanding of my argument. My point is based on empirical fact: if variation is routinely producing children that have markedly different functional responses to color stimuli than their parents, then how come we only very rarely see those variations that do not result in observable differences?

we can have various colors of our irises because the particular hue of their pigment does not strongly determine fitness and so is not strongly selected for.
— A Raybould

So green versus blue eyes don't seem to matter much to fitness. — InPitzotl

So we agree on something. Is it too much to think that we also agree that this lack of fitness is because the primary function of the iris' pigment is to block the transmission of light, and so what it reflects is not consequential?

I do not think it is very speculative to say that our mental abilities are strong determinants of fitness (unless, of course, one thinks our experiences are epiphenomenal.)
— A Raybould

In what way? — InPitzotl

The alternative is so lacking in plausibility that I will not bother to reply until specific arguments for it are presented. Extraordinary claims require extraordinary evidence.

So this is all speculative, but I wrote this earlier, and you said at the time that you accepted it:
— A Raybould

...not quite, but the disagreements are in the weeds (e.g. it's possible to formulate a theory before a hypothesis)... and not quite useful for this discussion. — InPitzotl

(By the way, I'm curious about what was, at some point, a theory but not a hypothesis.)

For reference, let's see what you are still not disagreeing with in any material way: "In scientific inquiry, theories are preceded by hypotheses. You don't have to believe them, just consider them. Of course, if there is contrary evidence rendering a hypothesis unviable, then it is summarily rejected and science moves on, but that does not seem to be the case here." I will have more to say on that below.

Furthermore, what are the counter-arguments, other than that it is speculative, which isn't a fatal flaw in a mere hypothesis?
— A Raybould

Counter-arguments fall back to debate mentality. What we're really interested in is the truth... — InPitzotl

Argument and counter-argument are the principal methods of philosophy, and are important in science; these are both generally regarded as attempts to discern the truth. What is not acceptable are various ploys often seen in other arenas of debate, such as the repeating of a claim after it has been refuted, as if it had not been, or quoting out of context.

...So the analysis to be done on a hypothesis is to explore the ways in which the hypothesis could reasonably fail. That's what I've been doing here. — InPitzotl

To the extent you have been on-point in that respect you have been helpful, and I thank you for that - but your work here is not complete.

but how are these flaws ["hasty generalization" and "personal incredulity"] manifest in this particular argument?— A Raybould

It's very simple... — InPitzotl

The last time you said that, you shortly afterwards backed away from the claims that followed... What you wrote here did not actually throw any light on what I am being incredulous of, which is fine if you are no longer making this claim.

To adequately justify this, you need to show how evolution is inconsistent with different-experience. — InPitzotl

As you have misunderstood the evolutionary argument, your judgement of its efficacy is suspect.

...The first argument you advanced failed very quickly with a sanity check; green-eyed people not being universal suggests that evolution doesn't always produce universal traits. — InPitzotl

As we have seen above, you did not follow that argument, and, as a consequence, replied with a non-sequitur.

you seem to beg the question by thinking backwards about it, something along the lines of "if different-experiences were had, there would be differences in fitness". I claim this is backwards because you're trying to start at evolutionary fitness and then conclude same-experience — InPitzotl

 As we have seen above, you did not follow my arguments, and, as a consequence, you are arguing against your own mistaken attempt to paraphrase my position. Furthermore, any scenario, in which the different-experience hypothesis has a difficulty explaining observations and the same-experience hypothesis does not, is an argument (or evidence, if it is an empirical fact) for the latter over the former.

The argument rather is that evolution is compatible with different-experience theory. — InPitzotl

I don't recall that argument being made - could you point me to where it was?

But the actual stated position I'm taking is a non-position [my emphasis.] — InPitzotl

While your stated position, being indefeasible (though trivially so) is a strong one to sustain during a debate, its usefulness in the search for knowledge is wholly dependent on other people looking for answers. 

As soon as a thesis is mooted, both it and its antithesis exist as hypotheses, regardless of your personal attitude to them. While your stated goal, apparently, is to show that the notion that our experiences are similar to a first approximation does not achieve hypothesis-hood, the closest option you have to that is to summarily dismiss it. There are several ways you could achieve that: You could show it to be incoherent or internally inconsistent, or you could show it to be ruled out by established facts. You could show that it is unfalsifiable. Failing any of these, you could, if you had an alternative view, argue that it is so much more plausible, than the alternative, then the latter is barely worth considering - but, absent that differential plausibility, implausible hypotheses cannot so easily be dismissed (plenty of previously implausible ideas have become theories.) By simply presenting ways in which new knowledge could defeat it, you are already treating it as a hypothesis, and will continue to do so up until the point where you achieve one of the above.


BTW, in reply to an earlier ETA:

So according to these established modes of color blindness (and tetrachromacy), they are in fact at the L1 level. — InPitzotl

I am guessing that your emphasis on 'established' indicates that you were aware of this, but I had in mind cerebral and congenital achromatopsia and dyschromatopsia, color agnosia, and any related pathologies.

 
I think we should reset this discussion, and start over. 

Firstly, let's get rid of the ambiguous phrase "physical knowledge", and replace it with "knowledge of physics", and similarly, replace "physical fact" with "fact about physics", "physical proposition" with "proposition about physics", etc. If we reach a point where this substitution does not express what we want to say, we will find an alternative, non-ambiguous substitution. In particular, if "physical information" comes up, we will use either "information about physics" or "information coded in physical form", according to which we mean.

Secondly, let's put aside what the skeptic believes. If you like, imagine the skeptic is someone who leans towards dualism but still doubts that your argument succeeds.

Thirdly, let's use Churchland's 'equivocation' objection as modified by Torin Alter and Tim Crane, which uses the concept of discursively-learnable knowledge. This simply means any knowledge that can be gained through reading, or by attending lectures, seminars, tutorials, etc., or watching or listening remotely - i.e., any knowledge that can be conveyed language backed up by illustrations and demonstrations (though not, of course, in this case, any visual that needs to be in color!). This looks very much like propositional or factual knowledge, but by tightening the argument by using  'discursively-learnable' instead, we can simply avoid getting mired in the question of whether the intellectualists are right in claiming that all knowledge is propositional: even if they were right in some sense, Churchland's rephrased objection is unaffected, as it does not rely on making any distinction between propositional and non-propositional knowledge.

In your definition (and Jackson's), all knowledge of physics is clearly discursively-learnable (even when one deduces a fact from others, the line of reasoning that led to the deduction could be written down and learned by others from those words, so it, too, would be discursively-learnable.)

What (if anything) Mary learns from seeing colors is either discursively-learnable or it is not. We can consider these two cases separately.

If it is not discursively-learnable, then physicalism is not challenged by Mary not learning it until she was released, as she could have learned all the discusively-learnable knowledge that could ever possibly be known, and still learn something more. It is irrelevant whether what she knows before being released is knowledge of physics or of something else.

Alternatively, if her new knowledge was discursively-learnable, then why could she not learn it from her studies? You cannot simply assert, without justifying the claim, that it was not knowledge of physics, and therefore ruled out by the premise, as that would be begging the question.

Whatever else you say about your argument, you must also address this issue if you want to claim that it avoids Churchland's charge of equivocation. Therefore, I urge you to confine your reply to anything that is germane to this particular issue, so that we do not get mired in side-issues.

 

This is how you originally engaged me:
It doesn't approach being a proof, but, IMHO, it is a plausible hypothesis. Per my earlier post, I would not propose that everyone's experience is the same in detail, but that for most people, there is a broad degree of functional equivalence.
— A Raybould
What arguments are there for the proposition that everyone experiences things fundamentally differently?
— A Raybould — InPitzotl

And in quoting me, you left off the very next line:

Or do the three of us just have different intuitions about how different they are? — A Raybould

Later on, I wrote:

Do you see what I'm getting at?
— InPitzotl

I think I do, and I think we are talking at cross-purposes. You are saying that these differences exist, and I am saying that they are second-order effects, modifying an underlying commonality. We could both be right! (Or wrong.) Alternatively, we could just agree to disagree in our opinions and wait for neuroscience to achieve a more fine-grained picture than fMRI and related technologies has delivered so far. — A Raybould

so it is not as if I am imputing straw-man arguments to you.

Also, obviously, we don't actually agree that our L2 colors are similar... otherwise, philosophers wouldn't brandish about terms like "inverted spectrum". — InPitzotl

Please explain how the conclusion follows from the premise.
— A Raybould

It's almost a direct translation. L2 colors are our experiences. An inverted spectrum philosophically is by definition an inversion of the experience of colors, ergo, it would be an inversion of the L1 color space mapping to the L2 colors. — InPitzotl

The only invocations of inverted qualia that I am aware of are in modal metaphysical arguments against functionalism. I may be mistaken, but I do not think that even a majority of the philosophers who invoke these arguments have much commitment to the proposition that such cases occur in the actual world, and the philosophers who do seem to be a minority of all philosophers.

More generally - and I think it covers all the points you have raised here - you are saying that there are cases where disparate experiences would have no observable behavioral effects, and I am saying that nevertheless, there are other cases in which they would (plus that I am of the opinion that commonality of experience, at a functional level and as a first-order effect, is a plausible hypothesis, for reasons that I will get into below.) Inverted spectrum scenarios are not the only way in which two people might differ in their experiences, and not all of those alternatives would result in  them agreeing over the categorization of colored objects.If you can invoke inverted spectra, surely I can invoke these others!

Of course, if you summarily rule out all scenarios, in which the two parties would not agree on color categories, as "incoherent gibberish", then of course they could differ over the full range of remaining possibilities and never disagree on the categorization of color!

Are you arguing that if the functional mappings are equivalent (say, in the sense that if the behaviors of ranking things into categories are the same), that this implies that the experiences are the same? — InPitzotl

This is an issue you raised, not me:

If I experience red a different way than you experience red, wouldn't we still both call red things red? — InPitzotl

And I replied with the response that I have not yet seen any reason to change, "not necessarily."  I'm not making a point here, I am merely answering your question. I assumed your question was the prelude to an argument on your part, but I do not believe we have seen the follow-on yet. And if you object to "not necessarily", are you not arguing for "necessarily?" What else is there?

As to what my position is:
It is my impression that the idea, that we cannot and could not tell if our experiences are the same, is the majority view, and it is one I used to hold, but I have come to think of it more likely than not that they are, up to the level of first-order effects. My reasons for suspecting this to be so are these:

Empirically, neurophysical studies using multiple subjects work - they produce quite specific results that can reasonably be taken as general, applying to the majority of the population. In study after study, some aspect of mental functionality is found to be expressed in the same small region of all the subjects' brains, so the evidence is that our brains are quite similar up to an architectural level, and at least to some functional level.

It would be a fair point to say that these studies have only gone so far in figuring out how brains work, though this strikes me as being like a 'God in the gaps' argument. It is at least plausible that this commonality will continue to hold as we advance our understanding of how brains make minds.

A dualist might say that it is possible for two people to be identical in every possible physical way, and still have different experiences (that's what inverted spectra arguments claim), but I am not a dualist and I doubt this is possible; I reckon that if we could acheive a complete, causal, physical model of the brain, we would find that's all there is, and that there isn't anything beyond that for experiences to differ over.  
 
You have attempted to dismiss this as my attempt to impute attitudes to researchers, but it is actually based on the empirical fact that these multiple-subject studies work, and that it is uncontroversial to generalize the results from the studies' subjects to the general population.

Secondly, the human brain is a network of neurons trained over hundreds of millions of years, and at each generation, the information accumulated by that training is squeezed into DNA and reconstituted. It is certainly possible that, while externally our minds function similarly in many ways, under the hood, each brain is working quite differently than any other. A more parsimonious expectation, however, is that this multi-generational training has produced brains that function alike, to a first approximation. If they did not, how likely is it that they would have, so to speak, 'learned the lessons' imparted by evolution? If a child's high-level brain function can vary markedly from that of its parents, how likely is it that it would nevertheless still be behaviourally similar enough that the child has approximately the same level of that part of its fitness that comes from its mental abilities? Alternatively, what sort of mechanism would be needed to conserve the external behaviour in the face of internal variation? We cannot depend on evolution doing that, as evolution is itself dependent on the conservation of fitness traits from parent to offspring.

As for your objection that we don't all have green eyes, here is where the point about evolutionary conservatism (selection results in tight constraints on variation in matters that are strong determinants of fitness) comes in: we can have various colors of our irises because the particular hue of their pigment does not strongly determine fitness and so is not strongly selected for. I do not think it is very speculative to say that our mental abilities are strong determinants of fitness (unless, of course, one thinks our experiences are epiphenomenal.)

To be fair, I have not made these arguments in this detail before, though they have all appeared in abbreviated form. One advantage of this discussion is that I have given the issue more thought.

So this is all speculative, but I wrote this earlier, and you said at the time that you accepted it:

In scientific inquiry, theories are preceded by hypotheses. You don't have to believe them, just consider them. Of course, if there is contrary evidence rendering a hypothesis unviable, then it is summarily rejected and science moves on, but that does not seem to be the case here. — A Raybould

Furthermore, what are the counter-arguments, other than that it is speculative, which isn't a fatal flaw in a mere hypothesis? You appear to have started into an argument based on us agreeing on color categories, but you do not appear to have finished it yet. Earlier, you wrote:

But the argument here is, at least IMO, trivially made. The arguments given for same-experience to me sound like classic textbook hasty generalization. It seems you're describing an approach that is particularly vulnerable to argument from personal incredulity, and is way too quick on the belief button for my tastes. — InPitzotl

OK, like my views, it is an opinion, but to me this looks like 'guilt by association': it seems, to you, like other arguments, ones that suffer from "hasty generalization" and "personal incredulity" - but how are these flaws manifest in this particular argument? What do you think I am being incredulous of?

Ha! this is just a long-winded way of attempting to hide that you are failing to refute what I have been saying: people generally agreeing on categories implies a degree of commonality in the mapping of sensory input to experience. We also have examples of second-order variance from this commonality, as demonstrated by various forms of color-blindness, which need not necessarily arise at L1.

At this point you are reduced to attempting to pin straw-man opinions on me, with some motte-and-baileying thrown in.

By the way, you may have missed some additional points that I added to my previous post after first submitting it.

There's an implied hypothesis that the mapping would be linear. — InPitzotl

That's my point about your argument - you are making assumptions - assumptions that say "our experiences have these similarities".

But in the end you still wind up at my position... that we simply need more study. — InPitzotl

Equally for your assumptions. You are being inconsistent. You are also "straw-manning" me in suggesting that I think otherwise.

ETA:

Also, obviously, we don't actually agree that our L2 colors are similar... otherwise, philosophers wouldn't brandish about terms like "inverted spectrum". — InPitzotl

Please explain how the conclusion follows from the premise.

I cannot imagine why you think I am confusing L1 and L2, but there is nothing to be gained by following that any further.
— A Raybould
It's because you keep talking about behavioral responses and disagreements on whether all people would agree that particular things are red if they simply have different L2 colors but share L1 colors. — InPitzotl

While you are about it, please explain how that follows, also.

Firstly, thanks for taking the time to put together a well-argued case.

I cannot imagine why you think I am confusing L1 and L2, but there is nothing to be gained by following that any further.

Last things first...

Would we not be able to take a different 3D slice of this 4D L2-color space and have a second trichromat have this as his L2 colors, and still have the property in both individuals of having each of their L2 colors vary continuously in correlation to the 3D L1 color spaces? — InPitzotl

Possible? Certainly. Likely? I was already of that opinion, based broadly on the sort of evidence and argument you are presenting here. Necessary? No; if we are going to suppose that everyones' experiences of color are different, without any constraint on how different they might be, then we cannot assume continuous variation, let alone any isomorphism between individuals, or even any stability within a single individual.

You had asked "If I experience red a different way than you experience red, wouldn't we still both call red things red?" and my reply was, and still is, "Not necessarily." The point here is that the assumption, that we would both agree about the redness of all (or most) things, is predicated on assumptions about our experiences being similar. I am not saying that these assumptions are unreasonable (quite the contrary, in fact; I am making the same assumptions in my own point of view); I am saying that these assumptions are being made.

And what are we basing those assumptions on? The observed behavior of people (including statements about their experiences) and what knowledge we have of the physics of visual perception! It seems we can make informed guesses, about how the experiences of different people are likely to be similar, from these sources.

Nevertheless, I think we can trim the range of issues to be covered.

I think I allowed myself to be misrepresented, since if you are saying that the two premises of my argument concerning what it would be to have complete physical knowledge are up for grabs as well, sure, I'll concede that. — jkg20

Personally, I don't think your concept of complete physical knowledge is incoherent, or inconsistent with respect to the way you define it (and the same goes for Jackson's); my point is that "physical knowledge" is an ambiguous phrase, and your definition is not the one that leads to a challenge to physicalism, should Mary learn something more on release.

As Crane points out, this is a thought experiment, so improbable things are allowed, and if you object to the impracticality of achieving this knowledge, you are simply not engaging with it.

If, on the other hand, a materialist monist says Mary now knows what it is like to see red, and that knowledge is physically encoded, then that means there is some set of propositions about Mary's physical state which describe what is encoded, and so expresses what it is she comes to know.[my emphasis.] — jkg20

This is a very common and deep-rooted misconception. It simply is not the case that knowing all the facts, about the physical state of one's brain when one has some particular knowledge, is the same as having one's brain in that state, and physicalists can reasonably propose that unless one's brain is in that state, one does not have that knowledge.

Of course, if that knowledge is not propositional/factual, then there is obviously no way that facts about that knowledge are that knowledge, but even if we limit ourselves to factual knowledge alone, propositions stating facts about something we know are not the propositions comprising that knowledge itself - but I do not think we need to consider the propositional case further, anyway:

This is moot, however, as, whatever else Mary's physical knowledge is, it must be something one can learn from books or lectures (Alter calls this 'discursively learnable.') The additional premise, then, becomes "after her release, Mary gains discursively learnable knowledge about color vision." This puts dualists on the horns of a dilemma: Unless what she learns on her release is discursively learnable, Churchland prevails, but if it is, then how come she did not learn it from her studies? It would be begging the question to just assert the premise that it must be nonphysical discursively-learnable knowledge. — A Raybould

But the arguments, Jackson's and mine, are based on the idea that Mary's knowledge is complete — jkg20

Jackson (and also you, I believe) are actually arguing that Mary's knowledge, at the time of her release, is incomplete - but any response along these lines is missing the point of my analogy. It is a simple fact that no-one (neither monists nor dualists of any type) have complete knowledge of how minds work (if any faction did, the issue would be settled.) Given this, then not only is it is inconsistent to rule out one side of the debate on account of its proponents' inability to give a full accounting of how minds work, it is doubly so to accept the view of side that claims to have proof, despite their not being able to give such an accounting, while rejecting the claim of those who merely say that it has not been proven, on the grounds that they cannot provide a full accounting. Until we can get agreement on what would constitute an acceptable response, there is no point in discussing the merits of any argument.

It would be really useful if, in your next reply, you could address this issue alone, as I am not going to re-state the counter-arguments to any other point you make, only to have them once again rejected for a bogus reason.

It is clear that before we can complete the discussion of your argument, we have to resolve the issue of what would count as an effective counterargument. I do not think I am misrepresenting you when I paraphrase your position as being that a physicalist must either reject the premise that Mary learns anything on first seeing colors, or must give a full (or almost complete) physical accounting of what she does learn.

This is simply not so. A physicalist can alternatively accept that Mary does learn something, but show that it is beside the point in one way or another, and one way to show that is to make a plausible case that there could be some explanation for why Mary had not learned it beforehand, that does not challenge physicalism - and that's what most of Jackson's opponents do seek to show.

This sort of thing is common in all fields of incomplete knowledge. For example, in astrophysics, the rates of rotation of galaxies seems inconsistent with what we know of gravity. There are at least two putative explanations: MOND (gravity works differently at long range) and dark matter (there's something we haven't seen yet adding to the galaxies' gravitational field.) Suppose someone says that the rotational data proves MOND. When a skeptic says that dark matter is an alternative possibility, simply saying "so prove me wrong" would not be a reasonable response from the first person, and demanding that the skeptic must say exactly what dark matter is would amount to that, and would be a clear case of burden-shifting. The rational response to the issue is to say that we have these hypotheses, and have not yet figured out what is going on. Jackson is not saying this about the mind; that is not even a point that needs arguing. In his initial paper, he literally claims to have proof of the falsity of physicalism (a position that he subsequently backed slightly down from, and then reversed entirely.) If you are merely saying that physicalists have not yet presented an explanation of the mind, then there are much easier ways to make that point, if you can find anyone who disputes it.

Let's look at it another way: one of your premises is that Mary knows enough to predict the future in every physical detail, but what, exactly, does she know? It would be inconsistent to consider a lack of a complete explanation to be an objection to the premises of responses, but not to your original premises.

This is not just my opinion; this is how philosophy (and science) works. This is what Churchland said: 

"The view sketched above is a live candidate for the correct story of sensory coding and
sensory recognition. But whether or not it is true, it is at least a logical possibility.
Accordingly, what we have sketched here is a consistent but entirely physical model (i.e.,
a model in which Jackson's conclusion is false) in which both of Jackson's premises are
true under the appropriate interpretation. They can hardly entail a conclusion, then, that
is inconsistent with physicalism. Their compossibility, on purely physicalist assumptions,
resides in the different character and the numerically different medium of representation
at issue in each of the two premises. Jackson's argument, to re-file the charge, equivocates
on 'knows about'."

This is far from the only thing I have to say about your previous reply, but I think we need to deal with this one first.

I'll back fill this with more detail for you some time later when I get time if you like. — InPitzotl

I eagerly await your explanation.

Is certainty an appropriate burden for some purpose here? — InPitzotl

Feel free to reply at the greatest confidence level you think can be justified.

I think it is sometimes called 'yellow' (if I am recalling that usage correctly) because it is a variant of the more common green opsin, with a spectral response shifted towards longer wavelengths.

If two people differ in their experience of a class of stimuli, is there any reason to be certain that they will be able to come to an agreement on how to categorize them? (Though it would be easier for them to do so if they were merely second-order differences.) We don't learn what 'red' means by memorizing a canonical chart of all the hues that are red. And there are behavioral differences: for one thing, tetrachromats behave differently than most of us in the tests that demonstrate their particular talent.

...if you accept that Mary gains anything epistemologically, you are obliged to give an account of what she gains — jkg20

The question of who bears the burden of proof (or accounting) is not always clear-cut, but in this case, I think Churchland's response, especially when put in terms of what is discursively learnable, puts the burden squarely in the dualists' court. I think this is most clear when we adopt Crane's third premise, again put in terms of what is discursively learnable: "After her release, Mary learns a discursively-learnable fact about color." A dualist could simply assert that this is so, but doing so would not put us under any logical obligation to accept it, especially as we could ask the dualist why, if it is discursively-learnable, Mary could not have learned it before her release. If she could have done so, then the premise that she must learn something new does not hold.

Also, as I have pointed out elsewhere, no dualist has ever given an account of what non-physical whatever-it-is Mary supposedly gains.

As it happens, however, I think physicalists can give a very straightforward account of why she could not learn, beforehand, whatever she learns from seeing colors. As you propose, Mary, knowing everything that could possibly be known about the physics of color perception, will be able to figure out what changes will occcur in the physical state of her brain as a consequence of any particular color-vision experience. According to the physicalist premise, these changes, and these changes alone, bring about Mary's new knowledge, so all she would have to do, while isolated, is to make those changes happen to her brain state, and she would then know, say, what it is like to see red (or whatever she would learn from the specific experience for which she has worked out what it will do to her brain.)

Knowing what those changes are, however, is not enough to make them happen. Our brains are simply not connected in such a way that we can address individual synapses and make specific changes to their state. Mary has all the knowledge she needs, but lacks the means to put it to use.

In this view, what she learns from seeing colors is physical knowledge in one sense: knowledge in which the information content is in physical form. It is not physical knowledge in the other sense of being a true proposition about the physical world (anything that is, she already knows.) The physical knowledge, of color vision, that Mary can learn while isolated, is limited to things of the latter form, so there is no problem for physicalism in Mary gaining physical knowledge in the former sense afterwards.

This is actually a contingent fact, as it is possible that, at some time in the future, we will develop the technology to make those targeted changes to our brains. With such a device, and Mary's physical knowledge, she could come to learn what color vision is like, without having experienced it (the experience of using such a device might be quite unusual, perhaps like the experiences of those people who must be conscious as brain surgery is performed on them.)

Update:
As far as I can tell, these objections work just as well as a response to your argument as to Jackson's. If I am not mistaken, the major difference between them is that you say that Mary's complete knowledge means that she can infallibly predict the future. This takes us into the murky waters of determinism and causality: if she can predict what she will know in the future, why can she not know it now? (Especially as, by premise, it is propositional.) It would be begging the question to say that she cannot do this because it is nonphysical knowledge.

Do you see what I'm getting at? — InPitzotl

I think I do, and I think we are talking at cross-purposes. You are saying that these differences exist, and I am saying that they are second-order effects, modifying an underlying commonality. We could both be right! (Or wrong.) Alternatively, we could just agree to disagree in our opinions and wait for neuroscience to achieve a more fine-grained picture than fMRI and related technologies has delivered so far.

BtW, I recall seeing some fairly convincing evidence (some variant of the Ishihara test), a few months ago, that a small percentage of women are functional tetrachromats, having two different yellow-detecting pigments, but I do not recall where I saw it.

If I experience red a different way than you experience red, wouldn't we still both call red things red? — InPitzotl

Not necessarily - it seems quite possible that, while we might agree that certain things are red, we might not agree on others. Of course, people do sometimes disagree over subtle distinctions in hue, but that is what I would call a second-order effect.

Even if we admit that one gains the ability to remember and compare colours, it is unclear how or whether this is a gain of knowledge of any sort. — Luke

If it is not knowledge, then Jackson's argument fails, because it depends on her gaining knowledge that is not in the set of "all the physical knowledge." More conventionally, it is regarded as a different sort of knowledge: knowing-how instead of knowing-that. As Jackson's concept of physical knowledge is of the knowing-that sort, physicalism is not challenged by her new knowledge not being part of it.

There is no equivocation in the argument I gave, which does not even end with the conclusion that physicalism is false [my emphasis] — jkg20

Well, if you haven't reached the conclusion that physicalism is false, then you have not completed your task of, as you put it, circumventing Churchland's attack [1]. Jackson makes no bones about the goal of his argument: it is to demonstrate that physicalism is false, and Churchland's response says that it fails to do so.

Churchland accepts the premise that Mary has all the knowledge that Jackson claims she has, and also that she learns something new after her release, but this presents no challenge to physicalism, because what she learns afterwards is not within the set of physical knowledge as defined by Jackson (and you), and physicalism neither depends on nor implies that it should be.

Churchland uses Jackson's equivocation over "knows about" to make this point: all the knowledge Mary gains from her studies must be propositional (she is being denied any opportunity to learn about color by any other means, such as experience), while it is entirely plausible that what she learns afterwards is not propositional. In the paper, which I urge you to read, he makes a biological argument for the plausibility of this new knowledge being non-propositional (one of the things he points out is that there are a great many species of animal having trichromatic vision, and for which, therefore, there is presumably something that is "what it is like" to see colors, but do not have language; presumably, they are not believing in propositions of any sort.)

Churchland also makes a point that people often get wrong: he is under no logical obligation to provide a complete and factually correct account of exactly what Mary would learn on her release. While that would be one way to refute Jackson, there are others, and showing that the argument is invalid is how Churchland does it here. As Jackson is claiming to have proven that physicalism is false, he has assumed the burden of showing that there is no way it could be true (to this, I would add the point that no dualist has ever given an explanation of how their alleged non-physical aspects of minds work.)

As Tiim Crane has pointed out, the issue of validity can be turned into an issue of soundness, by adding a further premise, such as "after her release, Mary gains propositional knowledge about color vision." Unsurprisingly, Jackson, who overlooked this issue, made no argument for it.

In retrospect, Churchland was not as tightly constraining as he could have been, and by calling Jackson's "all the physical knowledge" propositional, he encouraged some dualists to claim that Mary might learn something propositional on her release. As they have not been able to say what that is, despite the fact that there have been billions of people who are both language-capable and know what it is like to see colors, I doubt it.

This is moot, however, as, whatever else Mary's physical knowledge is, it must be something one can learn from books or lectures (Alter calls this 'discursively learnable.') The additional premise, then, becomes "after her release, Mary gains discursively learnable knowledge about color vision." This puts dualists on the horns of a dilemma: Unless what she learns on her release is discursively learnable, Churchland prevails, but if it is, then how come she did not learn it from her studies? It would be begging the question to just assert the premise that it must be nonphysical discursively-learnable knowledge.

Note that Jackson never equivocates in the sense of saying, in one place, that "learns about" means this, and in another place, that it means something contradictory to that: it is, instead, implicit in how he uses the phrase. He does essentially the same, or so I propose, with the phrase "physical knowledge." He (and you) define it esentially as "knowledge about physics", and if Mary learns something on her release, it cannot be physical knowledge, therefore physicalism is false. It is in the "therefore" that we have a false implicit premise, which is that, as this new knowledge is not knowledge of physics, physicalism must be false - but physicalism neither implies nor depends on all knowledge being knowledge of physics. The English phrase "physical knowledge" is ambiguous, as, in addition to this reading, it might also be read as "knowledge, where the information content is encoded in physical form", but Jackson's argument cannot just be restated to use that definition consistently, as one would be begging the question to assert that what she allegedly learns after her release is not in that category.


[1] Update: As soon as I posted, I realized that you probably meant that your argument went beyond proving that physicalism is false. Unless it succeeds at that, however (and I do not think it does), then anything else that follows is moot.

Purely by chance, I noticed that you added a postscript to your last-but-one post after I had replied to it, in which you offered some sort of response to my requests for clarification of something you had postulated. I'm prepared to put that down to concurrent editing, but there are some unusual aspects to that response.

For one thing, you say "I'm not too interested in fleshing out this theory since I don't particularly subscribe to it", which is rather an odd thing to say about something you had postulated only a few hours before as if it were a strong argument for your position. I will assume that you were not disenchanted with it at the time you first postulated it, as to put forward a view that you did not actually hold, without making that clear, would be quite deceptive, so it seems that you changed your mind during the time when I was probing its relevance. How long, I wonder, would you have left me under the impression that you still held that view?

You also added links to a video and a paper, and the latter, at least, does seem to have some relevance (Categorical encoding of color in the brain)

Here we have an experiment using functional MRI to study the responses of a number of subjects to sensory stimuli. This is a very common sort of experiment, yet If it were the case that everyone's responses to stimuli were more-or-less unique, such studies would fail to produce consistent results. Not only do they do so, but the whole tenor of the paper (and others like it) is infused with the tacit assumption that this commonality in function is a fact of how brains work - there is no hand-wringing over whether the subjects will be similar enough in their responses to justify the approach, and I would bet that the possibility that it would not be is rarely an issue in the funding of such experiments.

This, of course, is commonality at the level of abstraction probed by functional MRI, which does not prove that the commonality must hold at higher levels of functional abstraction, but it certainly does not suggest the contrary. You have already accepted that hypotheses do not have to meet the standards of evidence needed to be classed as theories, and that you don't have to believe them to consider them.

As for your examples of synesthesia and tetrachromacy, it is not unreasonable to consider them as second-order effects. I don't think many papers reporting this sort of work contain the caveat that their results cannot be extended to these cases.

Given the results of this experiment, perhaps you consider color categorization to be a counterexample to the hypothesis that most people's responses to stimuli are broadly similar?

The only thing that was to the point in your previous-to-last post was that you finally put up an argument (or, rather, the outline of one) in support of the position you have been taking: viz., your insistence that it is simply not plausible that sensory experience functions in a similar manner for most of us.

We just postulate that there's a large number of potential experiences and that the brain, while learning to see colors, simply picks any of these to bind to the interesting categories. — InPitzotl

It is not clear to me what you have in mind here, though it seems to be suggesting a chaotic process - but whether that is so may depend on what you have in mind when you say "a large number of potential experiences" (do you mean the totality of an individual's sensory inputs at any given time? Are emotional states included? Conscious thoughts?), on what basis you envision the picking to be decided, and how the categories are chosen for binding. At least until you explain these matters, it is not clear to me that you have a viable argument for your position.

At this point, my working hypothesis is that you do not have any plausible arguments for that proposition.
— A Raybould
Your working hypothesis doesn't work. — InPitzotl

All the evidence to that point (notably, the absence of any argument) supported it.Whether the situation has improved with your latest post remains to be seen.

But the argument here is, at least IMO, trivially made. The arguments given for same-experience to me sound like classic textbook hasty generalization. It seems you're describing an approach that is particularly vulnerable to argument from personal incredulity, and is way too quick on the belief button for my tastes. [my emphasis] — InPitzotl

That's not an argument, it is an opinion. Furthermore, it is an opinion of an argument, not an opinion about how minds work. You are as entitled to your opinions as the rest of us, but don't expect anyone to find anything like this, doubly removed as it is from being an argument for a substantive claim, to be persuasive.

Synesthesia demonstrates that there are different kinds of experiences to pick from, and that they can at least be useful in some people as category tags even cross-sensually. — InPitzotl

I am amused by the fact that your only substantive argument in this whole reply makes use of one that I first introduced to this discussion! Note that I was prepared to introduce a counterpoint to the position I favored, and that is because I am interested in getting to the truth, not in scoring points in some minor debate. Your question, "did you bother to try?" is best addressed to yourself.

We just postulate that there's a large number of potential experiences and that the brain, while learning to see colors, simply picks any of these to bind to the interesting categories. — InPitzotl

What does 'binding' mean? How are 'interesting' categories determined?

Furthermore, with "a large number of potential experiences" to pick from, unless the picking is done in some principled manner, one should expect that utter chaos would result, with people unable, for example, to agree even on what sorts of sensory perception there are. In practice, we find broad agreement, with only a few corner cases, such as the synesthesias that I mentioned, to hint of the potential chaos. How, in your theory, do you resolve this issue?

Essentially yes, but...

Firstly, we must recognize that people have been talking about colors for millenia, and, for the most part, doing so without having any theories about how the perception of color works (or, in some cases, demonstrably false ones).

As I mentioned elsewhere, language depends on a common vocabulary, and common vocabularies ultimately depend on shared experiences. We do not have direct access to what is going on in other peoples' brains, and not even to what is physically going on in our own. Nor can we directly sense the wavelength of the light we see or the energy of its photons. About the only shared experience of color comes from people looking at a given thing (say, a ripe tomato) and agreeing that a certain aspect of that experience should be given a name, such as 'red'.

For this to work, several conditions must be met, such as:

[1] Most people should agree that there is such an aspect to a tomato.
[2] Most people should agree on what else is red, such as blood or the embers of a fire.
[3] Most people should agree on things that are not red, such as the sky.
[4] Most people should agree that, nevertheless, the sky also has an aspect that is, in some useful sense, in the same category as the redness of a tomato.
[5] Peoples' color categories should be stable over time, barring any change in the thing being observed.

...and so on. Given that not everyone is able to join in this agreement, it seems that our being able to come to a broad agreement over these issues is a contingent fact, and that it is conceivable that this might not have been so.

This is where my database analogy comes in. It is completely implausible that most of our brains are identical at the neuron level, yet still we meet the conditions of the above list. In my opinion, we are like the ordinary users of the two databases, who can agree that their databases contain the same information, even though the two databases have almost no physical state in common. For the purposes of the ordinary users, who use the databases in performing tasks in the external world, the physical state is irrelevant. Only the system admins have any reason to be concerned with that state, and when we debate the nature of the mind, we are, as it were, logging on as administrators.

---

The takeaway from this is that almost nothing about how the mind works can be clarified or settled by arguing over the definition of the words we use to label our experiences, because those words were coined operationally, in ignorance of the underlying processes.

Let's cut to the chase, and start with one issue that seems to render everything else moot - your conclusion:

7. Given Lemma 3 and premise 6, what Mary gains [is] not knowledge of a physical fact. — jkg20

This seems to come back to what I said earlier about equivocation over the phrase "physical knowledge":

In Jackson's usage, he is referring to knowledge of physics, but physicalism does not imply or depend on all knowledge being about physics; what it does imply is that knowledge cannot be gained without there being physical change within the entity doing the learning. — A Raybould

I am unable to read your lemma 3 in any other light than you are making the same equivocation as Jackson here, and taking "physical knowledge" to be "knowledge of physics", as opposed to "knowledge which has its information content encoded in physical form." If this is not so, could you clarify your argument on this issue?


By the way, in 1927 Bertrand Russell penned a concise aphorism that captures what you are saying here (if I have not misunderstood you), and also the essence of Jackson's argument:

It is obvious that a man who can see knows things which a blind man cannot know; but a blind man can know the whole of physics. Thus the knowledge which other men have and he has not is not a part of physics.

As far as I know, Russell never regarded this as a refutation of materialism, and rightly so, as to mistake it for such would also require the same equivocation.

I think that most proponents of that view would say that she would be able to remember colors, compare colors, and even perform Hume's task of imagining an intermediate hue between two that she is seeing, before ever learning any names for them. It is mildly interesting to wonder if she would divide up the spectrum as we do (at which point, I must say that I have always regarded the distinction between indigo and violet as questionable!)

Thanks! I am surprised by the lack of attention that Churchland's paper gets, as, in my opinion, he has identified the fundamental flaw in Jackson's argument (Terence Horgan appears to be the first person to raise the issue of equivocation, but only in passing, and narrowly.) Even though Jackson himself has changed his mind on the issue, his argument is still debated (at least two English-language books were published on the issue last year!) but that debate seems to be mostly over the "old knowledge in a new guise" responses, which to me seem to be moot, given Churchland's straightforward rebuttal.

it is a plausible hypothesis.
— A Raybould
...and so is its null hypothesis. — InPitzotl

And often the null hypothesis is right! We seem to be agreed, then, that this hypothesis is both plausible and possibly correct.

What arguments are there for the proposition that everyone experiences things [fundamentally] differently?
— A Raybould
I could think of arguments, but that's irrelevant. — InPitzotl

Firstly, I see that the word 'fundamentally' is missing from my words without having been replaced by ellipsis. If you want to claim that everyones' experiences may be different in ways that we may not agree are fundamental, then we can go with the alternative that I proposed, and simply agree to differ.

At this point, my working hypothesis is that you do not have any plausible arguments for that proposition. Your next sentence reinforced that view, and your final paragraph did not lead me to change my mind.

The only argument necessary is that it's plausible — InPitzotl

Coincidentally, that's what I said about @Harry Hindu's point! - but plausibility itself does not come out of nothing; it needs an argument in support. A proposition without a justification states something that is conceivable, but not anything more.

What I have, instead, is a standard... an expectation that I have of a theory before I start doing silly things like believing it — InPitzotl

In scientific inquiry, theories are preceded by hypotheses. You don't have to believe them, just consider them. Of course, if there is contrary evidence rendering a hypothesis unviable, then it is summarily rejected and science moves on, but that does not seem to be the case here.

@Harry Hindu

... but to simply conclude that the color experiences are the same because we're all human sounds to me more like guesswork. — InPitzotl

It doesn't approach being a proof, but, IMHO, it is a plausible hypothesis. Per my earlier post, I would not propose that everyone's experience is the same in detail, but that for most people, there is a broad degree of functional equivalence. For example, I am not a synaesthete, and so will clearly experience some things differently than those who are. I suspect, however, that these differences are at the level of iris color or hair type: for one thing, evolution is very conservative about things that are important to fitness, and our minds, and the way they interact with our environment, seem to fall into that category. For another, there is empirical evidence in a broad agreement that certain experiences are pleasant/desirable and others are most definitely not.

What arguments are there for the proposition that everyone experiences things fundamentally differently? Or do the three of us just have different intuitions about how different they are?

There are some who disagree, but personally I agree that subjective knowledge is real. What makes it subjective, in my opinion, is that only I have the neural connections, to/within my own brain, needed for my mind to observe myself experiencing things and having emotions. No-one else has those connections, so they cannot know what it is like to be me in the way I can. As Dennett put it, "'Qualia' is an unfamiliar term for something that could not be more familiar to each of us: the ways things seem to us.”

The argument against Jackson is not that non-propositional knowledge is not knowledge, but that it is not the sort of knowledge that can be gained by studying (not 'discursively learnable', as Torin Alter puts it), so that Jackson's claim that Mary has all the physical knowledge is being challenged.

Conventional epistemology makes a distinction between propositional/knowing-that knowledge and various other forms, such as knowledge-how, (e.g. knowing how to ride a bicycle, which you don't learn from a book), and knowing a person or a place by acquaintance. For a while, the leading response to Jackson was the ability hypothesis, which claims that, on her release, Mary gained, not propositional knowledge, but certain abilities, such as how to recognize, recall and compare colors. These are generally considered to be examples of knowing-how, not knowing-that/propositional knowledge. These days, the favorite form of reply seems to be "old knowledge in a new guise": when Mary sees colors, she does not gain any new knowledge, but sees her existing knowledge of physics in a new way. To me, this seems both implausible and unnecessary, an attempt to explain away something that already has a straightforward explanation, so I am disinclined to describe it further.

If we define h-red to be the experience you have when you look at a red crayon, then this category would be completely useless... only Harry Hindu could relate to it. — InPitzotl

I think I can give an analogy which shows why this approach is not useful.

Suppose we have two different computers; say an ARM device running Linux and an Intel PC running Windows. Each has the same database on it (say, Postgres, though, because of the different architectures of the hardware, these will be different implementations of the same design.) In each case, the databases encrypt the data they store, though with different keys. Finally, suppose we store the same information in each of the databases, but we input it in a different order on each.

After this exercise, there will be almost nothing in common about the physical state of the two machines, and, as they do their work, there will be almost no commonality in the sequence of instructions they perform, yet, if there are no bugs, they will be perceived to function identically by their ordinary users. This commonality extends to various 'introspective' tools available to ordinary users, such as those that report the schema and the number of rows in each table. Absent any other clues, an ordinary user could not tell them apart.

System administrators, however, have additional tools at their disposal, which allow them to see how their machine works at a low level - they can see how the data is physically stored on the disks, and they can examine the programs and see how they do the work. The adminstrator of one machine will see it differently than does the administrator of the other see hers, but unless a person has administrator access to both machines, she will not be able to see for herself how the two differ.

In this analogy, our access to our own brains is like that of ordinary users, and we have no access to other peoples' brains other than what their ordinary users report to us. And no-one has yet achieved anything like administrative access to their own brains, let alone anyone else's.

It is probably not necessary for me to say what the point is here, but just for completeness, what matters is an abstract, emergent view of the physical state and function, and so long as, in each case, there is some mapping, not necessarily the same mapping, from this to the low-level state and function, physicalism is not disproved.

You will notice in many of the analyses of this 'thought-experiment' that it is simply taken for granted that states of being can be understood as brain states, but that in itself is simply an assumption. — Wayfarer

Jackson claims to have proven that physicalism is false, so physicalists can logically assume that physicalism is correct in any counter-argument - it is Jackson who has taken on the burden of proof in showing that this must be wrong. Dennett made this point in What RoboMary Knows:

"Before turning to the interesting bits, I must consider what many will view as a pressing objection:

"'Robots don’t have color experiences! Robots don’t have qualia. This scenario isn’t remotely on the same topic as the story of Mary the color scientist.'

"I suspect that many will want to endorse this objection, but they really must restrain themselves, on pain of begging the question most blatantly. Contemporary materialism–at least in my version of it–cheerfully endorses the assertion that we are robots of a sort–made of robots made of robots. Thinking in terms of robots is a useful exercise, since it removes the excuse that we don’t yet know enough about brains to say just what is going on that might be relevant, permitting a sort of woolly romanticism about the mysterious powers of brains to cloud our judgment. If materialism is true, it should be possible (“in principle!”) to build a material thing–call it a robot brain–that does what a brain does, and hence instantiates the same theory of experience that we do. Those who rule out my scenario as irrelevant from the outset are not arguing for the falsity of materialism; they are assuming it, and just illustrating that assumption in their version of the Mary story. That might be interesting as social anthropology, but is unlikely to shed any light on the science of consciousness."

Many of these kinds of arguments date back a few decades, when there was the confident belief that eventually science would develop to the point where you could directly 'see' a brain state. But when fMRI became a reality, there are still many major conceptual difficulties in doing precisely that (see this) — Wayfarer

Even with neural networks, it is pretty difficult to see how they perform their party tricks, despite us having complete access to their mechanisms, yet I do not think anyone is suggesting that they are non- or extra-physical. Anyone who hoped that fMRI, which gives a very much more coarse-grained view of what is happening than we have of neural nets, would solve the mind-body problem, was being unrealistically optimistic.

Jackson's use of the word "knew" needs to be clarified. — TheMadFool

This is actually the essence of Paul Churchland's response "Knowing Qualia: A Reply to Jackson", in which he shows that Jackson uses the term "knows about" in two different senses. The knowledge of physics that Mary has learned from her studies is entirely propositional (i.e. expressed in textbooks or lectures as a series of sentences that are distilled into propositions), while knowing "what it is like" is not propositional (if we could express it that way, then presumably Mary could have learned it before her release; Jackson is implicitly making hIs case on the reasonable assumption[1] that one cannot do this.)

In response, there have been suggestions that qualia are somehow propositional, as in phrases like "Seeing red has the phenomenal character R", but the people making such claims are never able to say what R is, so to say that I am skeptical of this claim is quite an understatement.

The inability to put qualia into words presents no challenge to physicalism. Language depends on a shared vocabulary, and a shared vocabulary ultimately depends on shared experience, but none of us can experience other peoples' sensory experiences directly, as we can our own, for a straightforward physical reason: our brains are not physically connected to theirs. The only reason we can talk of them at all is under the assumption that they are somewhat similar for other people, and there are many well-known cases where this is not exactly so (color blindness being just one example.)

Another way of putting the equivocation is in the ambiguity of the phrase "physical knowledge." In Jackson's usage, he is referring to knowledge of physics, but physicalism does not imply or depend on all knowledge being about physics; what it does imply is that knowledge cannot be gained without there being physical change within the entity doing the learning.

[1] Dennett disagrees that this is a reasonable assumption, on the grounds that this just assumes that knowing all the physics is much the same as knowing just a lot of it. Hence he calls Jackson's argument an intuition pump, and saying, as Jackson did, that it is "just obvious" that Mary will learn something on her release, is about as good an argument as saying that it is just obvious that the sun moves and the earth is stationary.

@Pantagruel
My go-to example for this sort of thing is the theory of evolution. It is one of the most powerful and influential scientific theories that we have ("Nothing in biology makes sense except in the light of evolution" - Theodosius Dobzhansky), and it is not reductionist, it is a systems theory.

Since Darwin developed his theory, we have learned a lot about the chemistry of life in general, and the mechanism of biological inheritance in particular. This has increased our understanding of evolution; for one thing, things that once had to be taken for granted (such as inheritance itself) now have a causal explanation.

This does not mean that the theory of evolution is redundant. On the contrary, a reductionist explanation, of how the current distribution of species on Earth came to be, is conceivable (though very much in principle), in the form of a vast catalog of every mutation along every line of descent of every organism alive today. Even if we had such a catalog, however, we would still, as Dobzhansky says, need a theory of evolution to make sense of it - the purely reductionist view is not wrong, it is just not useful on its own.

These days, there is little support for the notion that there is something about evolution that does not have a physical cause, along the lines described above, and the reason why reductionism is an issue in the philosophy of mind is because we wonder if the same could be said of the mind.

The origin of life is much more speculative than its evolution, but these days, the two camps on that matter simply ignore one another, for the most part. In many ways, the human mind has become the last refuge of vitalism, and science has not yet developed to the point where it can dislodge it.