18 lines
6.8 KiB
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18 lines
6.8 KiB
Plaintext
Quiddity has a qualia all its own
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<p>I changed my mind about a significant philosophical issue today, and in the process parted ways with a thinker I’ve been a serious fan of for a couple of decades now. The issue is raised by a thought experiment, of which I was previously unaware, called <a href="http://en.wikipedia.org/wiki/Mary's_room">Mary’s Room</a>. The simplest way of getting involved the dispute is to ask “How can I know that my experience of (say) the color ‘red’ is the same as yours? Is it even possible to have such knowledge?”</p>
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<p><span id="more-1192"></span></p>
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<p>The deeper question this gets at is whether physicalist theories of mind are sufficient; read the Wikipedia article linked above for the argument, I won’t rehash it here. Until a few hours ago I would have, somewhat reluctantly, agreed with Daniel Dennett’s position that Mary doesn’t learn anything when she steps into the world of color. I’ve long been a fan of Dennett’s bracing, unapologetic physicalism; I’ve especially enjoyed his witty takedowns of <a href="http://en.wikipedia.org/wiki/New_Mysterianism">mysterian</a> positions in the philosophy of mind. </p>
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<p>My reluctance would have stemmed only from this: whether or not Mary actually learned anything when she first saw the color red, it seems certain to me that Mary would <em>feel</em> she had learned something. Dennett argues that with complete knowledge of the physics of light, the range of red wavelengths, the history and significance of the color “red” to other human beings, Mary wouldn’t know anything about the world that she hadn’t known before. </p>
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<p>Under an operationalist, fallibilist account of “truth” – which I think is the only sane one – it’s at first hard to see how to argue with Dennet’s position. The Mary’s Room experiment conveys the assumption that Mary knows so much about “red” by indirection that she can make predictions about events involving “red” as accurately as anyone else. So if Mary says “Wow!” upon first actually seeing the color red, what does the “Wow!” mean? </p>
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<p>Dennet insists that Mary’s “Wow!” is meaningless – he seems to think he has to maintain that in order to defend physicalism against the mysterians. This is where I now part company with him. It certainly means something <em>to Mary</em>. Any theory of mind that can’t support questions about that meaning <em>to Mary</em> is dangerously impoverished – Mary won’t buy it, for starters, and why should she? Dennett thinks he’s robustly defending physicalism, but I think he’s surrendering the high ground to the mysterians.</p>
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<p>The Wikipedia article offers an alternative answer based on some experimental work by two cognitive scientists working with a color-blind synesthete. I think the Ramachandran-Hubbard answer (Mary will have blindsight about color distinctions) is as mistaken as Dennett’s, because Mary (by hypothesis) is not color-blind. But they did provide me with a vital clue.</p>
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<p>The human brain actually includes two semi-separated signal-processing pathways for vision. One is luminance-oriented and good at picking up fine details: it “sees” in black and white, but very sharply. The other is good at color distinctions but poor at processing shape details. The take from these two pathways is integrated at a late stage in processing, a fact on which depend several classic “optical illusions” and the continuing niche appeal of black-and-white photography in a world of cheap color film. </p>
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<p>Ramachandran-Hubbard’s color-blind synesthete is in the extremely odd position that he can have activations of his color-vision pathway from two different sources (his retina and the abnormal synesthesia pathways) which give him disjoint sets of color qualia. Ack! There! I’ve said it: the dread word <a href="http://en.wikipedia.org/wiki/Qualia">“qualia”</a>, which in Dennett’s universe no self-respecting physicalist is supposed to utter without firmly insisting that it is meaningless! </p>
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<p>Have I, too, surrendered to the mysterians? No. In fact, not.</p>
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<p>Here is my physicalist account of Mary’s “Wow!” What she learns is <em>what it feels like to have the color-processing pathways of her brain light up</em>. This is an objective fact about her subjectivity; with a sufficiently good MRI we could actually see the difference in patterns of occipital-lobe activity. And that will probably be a world-changing experience for Mary, fully worthy of a “Wow!”, even if we concede the Mary’s-Room premise that she has not learned anything about the world outside her own skull.</p>
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<p>To see this, imagine being a precocious, prepubescent scientist who knows (objectively) everything all other human have reported about sex. Now the hormonal switch flips, and you <em>feel</em> it…and nothing is the same, is it?</p>
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<p>What I’m really arguing here is that Dennett, and thinkers like him, are stuck hard enough in a theoretical set of distinctions about “objective” vs. “subjective” to have ignored an important part of the phenomenology. One’s own mental life – or, to put it physicalist terms, one’s perception of one’s own brain states – is part of the phenomenal field just as genuinely as Husserl’s copper ashtray is.</p>
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<p>I’m proposing that, contra Dennett, there is a sense of the word “qualia” that is meaningful in physicalist terms. A “quale” (singular form) is a brain state with the following properties: (a) like the abnormal activation of a colorblind synesthete’s color pathways in the occipital lobe, or like the first-ever feeling of sexual desire, it is in principle an objectively measurable event with detectable correlates in brain and body, and (b) it’s incommunicable. </p>
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<p>That is, I can learn to anticipate the phenomenal experience I will have when I look at something you have previously told me is “red”, but <em>I can’t tell you what that experience is</em>. Arguably, <em>all</em> brain states are incommunicable in that sense – but that’s actually part of my point; language and art and mathematics and music and so forth are all, in important ways, too narrow to shove our phenomenology through. </p>
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<p>The last laugh goes to Alfred Korzybski: the map is not the territory, the word is not the thing defined. We can communicate linguistic and para-linguistic maps, but not the phenomenological territory – the qualia – from which we abstracted them.</p>
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