I suppose you experience colors just like I do, but (when you think about it) you tell yourself that what naively seems to be a matter of seeing a yellow object is actually experiencing what it's like to have a perception tagged as yellow. But how does that translate, subjectively? When you see yellow, do you tell yourself you're seeing the tag? Do you just semi-visualize a bunch of neurons firing in a certain way?

We went over this issue a bit in the previous discussion. My response (following Drescher) was: "To experience [yellow] is to feel your cognitive architecture assigning a label to sensory data."

As I elaborated:

... the phenomenal experience of blue is what it is like to be a program that has classified incoming data as being a certain kind of light, under the constraint of having to coherently represent all of its other data (other colors, other visual qualities, other senses, other combined extrapolations from multiple senses, etc) but with limited comparison abilities.

The point being: I can't give a complete answer now, but I can tell you what the solution will look like. It will involve describing how a cognitive architecture works, then looking at the distinctions it has to make, then looking at what constraints these distinctions operate under (e.g. color being orthogonal to sound [unless you have synaesthesia], etc.), then identifying what parts of the process can access each other.

Out of all of that, only certain data representations are possible, and one of these (perhaps, hopefully, the only one) is the one with the same qualities as our perception of color. You know you're at the solution, when you say, Aha! If I had to express what information I receive, under all those constraints, that is what qualities it would need to have.

To that, you replied:

But I still do not see where the color is. ...

Though you object to the comparison, this is the same kind of error as demanding that there be a fundamental "chess thing" in Deep Blue. There is no fundamental color, just as there is no fundamental chess. There is only a regularity the system follows, compressible by reference to the concept of color or chess.

I suppose you experience colors just like I do, but (when you think about it) you tell yourself that what naively seems to be a matter of seeing a yellow object is actually experiencing what it's like to have a perception tagged as yellow.

I am intrigued by your wording, here. I suppose I experience colors just like you do, but - when I think about it - I tell myself that what is, in fact seeing a yellow object is, in fact the same thing as experiencing what it's like to have a perception tagged as yellow. I believe these descriptions to be equivalent in the same sense that "breaking of hydrogen bonds between dihydrogen monoxide molecules, leading to those molecules traveling in near-independent trajectories outside the crystalline structure" is equivalent to "ice sublimating".

But we part ways on the meaning of that. Apparently you think that even my hallucination isn't really yellow. Instead, there's some neural thing happening which has been tagged as yellow - whatever that means.

The relevant part of the optical cortex which fires on yellow objects has fired; the rest of your brain behaves as if there were a yellow banana out in front of it. "Tagging" seemed like the best high level term for it. A collection of stimuli are being collected together as an atomic thing. There's a neural thing happening, and part of that neural thing is normally caused by yellow things in the visual field.

The most obvious point where it has subjective import is when things change[1]. I probably experience colours as you do; when I introspect on colour, or time, I cannot find good cause to distinguish it from "visualising" an infinite set or a function. The only apparent different is that reality isn't under concious control. I don't assume that the naive ontology that is presented to me is a true ontology.

[1] There are a pair of coloured mugs (blue and purple) that I can't distinguish in my peripheral vision, for example. When I see one in my peripheral vision, it is coloured (blue, say); when I look at it directly, there is a period in which it is both blue and purple, as best I can describe, before definitively becoming purple. Head MRI's do this too.

Edit: The problem is that there isn't an easy way to introspect on the processes leading to perceptions; they are presented ex nihilo. As best I can tell, there's no good distinguisher of my senses from "experiencing what it's like to have a perception tagged as yellow"

Here is a full quote that makes clear in exactly what sense he doesn't believe in qualia:

So when we look one last time at our original characterization of qualia, as ineffable, intrinsic, private, directly apprehensible properties of experience, we find that there is nothing to fill the bill. In their place are relatively or practically ineffable public properties we can refer to indirectly via reference to our private property-detectors — private only in the sense of idiosyncratic. And insofar as we wish to cling to our subjective authority about the occurrence within us of states of certain types or with certain properties, we can have some authority — not infallibility or incorrigibility, but something better than sheer guessing — but only if we restrict ourselves to relational, extrinsic properties like the power of certain internal states of ours to provoke acts of apparent re-identification. So contrary to what seems obvious at first blush, there simply are no qualia at all.

Originally in Quining Qualia, 1988, by Dennett, and quoted on Multiple-Drafts Model.

The Taboo of Subjectivity is a book by B. Alan Wallace. It appears that Dennett wrote a review for that work, but I couldn't find it online. Are you referring to that review, or to something else?

Belatedly:

• I think the reference on p. 28 is pointing out that the brain doesn't turn purple (and a purple brain wouldn't help anyway, as there are no eyes in the brain to see the purple). The remainder of the page is extending the example to further elaborate the problem of subjective experience.

• I cannot find the reference to qualia quoted in The Taboo of Subjectivity at all - p. 74 is before Dennett even defines qualia, and p. 374 does not have those exact words - only the conclusion of a thought experiment illuminating his rejection of the concept.

Thanks for the page number - I'll see if I can find it in my copy when I get home.

So, subjective color does not exist, but references to color do exist.

The references to red together definitely form a physical network in my brain, right? I have a list of 10,000 things in my memory that are vividly red, some more vivid than others, and they're all potentially connected under this label 'red'. When that entire network is stimulated (say, by my seeing something red or imagining what "red" is), might I not also give that a label? I could call the stimulation of the entire network the "essence of red" or "redness" and have a subjective feeling about it.

I'm certain this particular theory about what "redness" occurs frequently. My question is, what's missing in this explanation from the dualist point of view? Why can't the subjective experience of red just be the whole network of red associations being simultaneously excited as an entity?

Above you wrote

Some people are at the stage of saying, color is a neural classification and I don't see any further problem.

So I guess I'm just asking, what's the further problem? (If you've already answered, would you please link to it?)

What are in those ellipses? In what you quote, I see that he's denying that it's "a private, ineffable something-or-other in your mind's eye". From what else I've read of Dennett, I'm sure that he has a problem with the "private" and "ineffable" part. Is it so clear that he has a problem with the "component of experience" part?