And when we keep all factors equal except a single factor, and varying it and it alone brings about the crucial change which the other factors don’t, that is the cause, yes? When the green wavelengths appear only when I switch the light on, I don’t see how it’s innaccurate to say you’re seeing light.
And having admitted that there’s no difference between calling what you see green and answering green when I ask you what you see, then if what you see is light, you are calling the light green, yes?
Then which of the two statements “I see green” and “green is a label” are you retracting, because their combination yields “I see the label green”?
You said “I suppose I could start calling experiences of that nature ‘red’”. Again, if you could clarify that it would be helpful.
You said it was a preference. Are preferences definitive? For example, can I say that physicalism is definitive just because I favour it?
Light. If I rotate the prism, I get to a point at which you suddenly stop calling the light green and start calling it something else: how do you justify this, and how is it different from when I stop calling something conscious and start calling it something else?
I don’t see how it’s a problem, given our understanding of how the glial cells in the retina function. I am telling you the explanation of our experience and consciousness in terms of the real world.
Light having a wavelength of 550 nm is green light, and green is a colour. So trees reflect green light (even when there’s nobody around), just as their vibrations are transferred to the air as longitudinal vibrations which propagate when they fall (even when there’s nobody around).
Then how do you explain the processing going on in your visual cortex - surely that’s an identification process? If I cut it out, could you still identify shapes and colours?
I don’t understand this statement, nor how it is different from “nobody knows how much the philosopher’s stone weighs”.
Again, I’m not talking about the optic nerve, chiasm and tract, whose finite length cannot be traversed instantly. I’m asking you waht you mean by “culmination”. Can you provide a little more than a single sentence on the subject?
Well, unless you’re falling prey to antiscientific dualism and saying that cognitive science cannot explain consciousness, I’ll call it a phenomenon to be explained. Calling it a “mystery” is IMO just accepting defeat without admitting it. Of course, you could have just said “I don’t know” in the first place.
Which is also explained by reference to an additional cognitive module or process (ie. “shadow-ignoring”).
What’s your guess?
No it doesn’t, like I already said, unless you’re trying to fight a strawman who hasn’t turned up yet (ie. the physicalist who says the only way to see green is by 520-570nm wavelengths being incident on the retina). You might have a long wait for your adversary, because no physicalist I know of takes such a position. Most, including me, say that wavelength explains colour, even in the cases where eg.complementary wavelengths are present.
Colour is an artifact of human perception, but we don’t manufacture it out of thin air, we (or rather, our bodies) attribute colour as a set of labels referring to measurable physical diferences in electromagnetic wavelengths.
Those differences in wavelength are tangibly real and cause different things to happen, regardless of whether we are around to label them as colours.
This is the statement which I, and I assume II Gyan II and other-wise, disagree with.
“Green” is not a property of the light. “Having a wavelength of 550 nm” is such a property, but “green” isn’t. We can say “Light of wavelength 550 nm usually causes us to see green when we look at it”, or even “Light of this wavelength will usually be described as ‘green’”, but not that it is green. The wavelength is not the colour, any more than the temperature of a body is its (subjective) “hotness”. That’s not to say that colour and wavelength aren’t very closely associated, but we can’t identify one with the other.
Depends what you mean by “artifact”! I would argue that the qualia of colour is a built-in mechanism of human perception, whereas the term “artifact” suggests to me that it’s in some way arbitrary or illusionary. It is a “label”, but a label at the hardware level of our brains, way before conciousness or language gets involved.
There’s a kind of synaesthasia where some people can see fine black-and-white patterns as coloured. V. Ramachandran documents a test for this in Phantoms of the Brain, whereby a fine black-and-white patterned shape is embedded within a similar black-and-white patterned background. A person with normal vision takes several seconds to identify the shape. A person with this kind of synaesthasia can identify the shapes instantly, because they see them as big red crosses or stars or triangles within the black-and-white background.
In the synaesthasia case, the percieved colour is certainly an artifact of human perception. The qualia of “redness” is being mis-assigned by their visual processing hardware. But the qualia of “redness” does have a real, physical aspect seperate from our consciousness - it is built into our visual processing hardware, part of the arrangement of matter in our heads.
What you “see” is not what’s arriving on your retinas. You have slightly different images arriving on each retina, with a blind spot on each one, and those images will be moving around as you move your eyeballs. Instead, what you “see” is a model generated by your visual processing hardware, and it plays fill-in-the-blanks with your blind spots, compensates for eye motion, assigns colour qualia to different wavelengths, interprets shapes and shadows as convex or concave, guesstimates the sizes and distances of things, triangulates for close-up depth perception, etc. Your percieved visual field is stuffed with non-linguistic labels and interpretations that are so seamless, you’re normally not aware of them.
The visual processing hardware can be fooled, of course. It will assume faces are always convex, so you can trick it with a rotating hollow mask. Does that mean that convexity or concavity are artifacts? With a funky false-perspective room, you make it see people as giants or midgets. Does that mean that size is an artifact? It depends on your point of view. Visually percieved “convexity” or “size” or “colour” are interpretations of optical information. If you regard such interpretations as artifacts, so be it.
Dunno; if we were not around to proclaim it, there would not be such units as nanometres either; ‘green’ is just a less precise way of labelling a measurement, but the measuring and the labelling are human inventions either way.
Again, I think my position would be more obvious if we use brown rather than green.
Take a look at the “cross” illusion again. The particular combination of pixels (and therefore wavelengths) in the left-hand image causes us to see brown. An identical combination of pixels in the right-hand image causes us to see orange. We must therefore either conclude that “orange” and “brown” are identical (in which case, we shouldn’t visit a greengrocer’s unsupervised), or that colour can’t be identified with wavelength.
What colour is light of wavelength 550 nm, then? What answer would you give in the prism experiment which ensures that the only variable is the wavelength?
When doesn’t that wavelength cause us to see green when we look at it? (Note that this is a different question to “when do we see green when looking at other wavelengths?”, as in the pink flashes I explained earlier).
Which is why I say wavelength explains colour, leaving the physicalism of colour unimpeached. (Frankly, I don’t know whoGyan was arguing with in the first place.)
I say that light of wavelength 550 nm is green. What do you call it?
I would agree with this, too. I’m not a great supporter of the idea of qualia in general (quale singular, incidentally) - it seems to me to introduce an unnecessary step between neurological activity and consciousness, and my old mate Bill tells us not to do that - but do you agree that “redness” doesn’t exist outside the visual processing system? That the first place we can meaningfully start discussing “redness” is the retina, not the light itself?
I’m not synaesthetic myself, so I can’t speak from personal experience, but I think it’s fair to say that the colours experienced by a synaesthete (if that’s the right word) are still genuine colours, even if they’re not caused by anything external to the viewer.
I think we’re getting into some tricky distinctions of language here! In one sense I agree, but in another sense, I can buy a “red” rear light for my bike and know what I’m getting, how it will look, how it will be seen etc. We use the same word “red” for the quale (cheers!) of “red” and as an adjective for light and/or pigments that generate that quale. Maybe we need even more words, in addition to “quale”?
Thinking about it some more, I suggest that this is the basis of the differences in opinion here. Go too far down the qualia route and you end up with solipsism - everything is qualia and you can’t prove there’s anything else! On the other hand, it becomes hard to discuss consciousness and perception without invoking qualia.
In the end, I think there’s a sufficiently strong correlation between the universe and the models generated by our visual processing hardware for us to assign adjectives to entities in the universe based on the qualia they induce. So yes, I’ll buy a red flashlight unseen, happy in the knowledge that it’ll leave my night vision intact.
A pure monochromatic light of 550 nm above a certain intensity is green. Every single photon of 550 nm light isn’t necessarily green, or any other colour.
On the prism experiment, I wouldn’t say there’s a sharp transition, certainly not between green and blue. (There may be a sharp transition between green and yellow, I’ve not tried it myself). I agree that the prism experiment shows that wavelength does have a great influence on colour - nobody denies this. But my position is that it’s not the only influence on colour.
Consider a car on a rolling road. Will it take off? Er… I mean, in that situation, if everything else is held constant, the speed of the wheels will depend entirely on the position of the accelerator. But while actually driving, although the position of the accelerator will have a great influence on the speed of the wheels, it’s not the only factor that determines it.
I’d still like you to consider (but not necessarily answer) the question - “How holy is light of wavelength 550 nm?”. I would say that this is the same type of question as the one you asked; if it isn’t, why not? (Remember that we can locate our feelings of “holiness” in one particular part of the brain. ).
I’m afraid I don’t know enough about the physiology of vision to answer this question. I’d guess that it doesn’t cause us to see green when it’s of a very low intensity, for one thing. And, of course, when it’s combined with light of other wavelengths to produce a secondary colour.
I think that sticking to primary colours obscures the discussion a little. Doesn’t the fact that there’s a distinction between primary and secondary colours demonstrate that we can’t isolate colour from the mechanics of visual perception? Or are the primary colours somehow “real”, while the secondary ones are “artifacts”? How would you go about identifying a primary colour without information about visual perception?
The argument is that “explains” doesn’t mean “completely explains”. If we do ever come up with a completely physical explanation of consciousness, then we’ll also have an explanation of colour. But I would say that we can’t have an explanation of colour which doesn’t address consciousness, which is restricted to wavelength and the physiology of the eye.
I usually call it green - there may be situations where I don’t. My point was that you appear to be saying (and, if you’re not, I apologise), that we can reduce colour to wavelength, that we can discuss colour without discussing psychology (not physiology).
And I think we can. My explanation of seeing green in the pink flashing lights still ultimately reduced to wavelengths and glial cells. The explanation of seeing one check darker than the other still reduces to wavelength configuration (ie. shape and shadow identification).
My position is that psychology is ultimately physiology, just as a computer game is ultimately electronic activity.
Good one! Thing is, there’s a sufficiently strong overlap between the visual processes of different people that if I ask someone to pick me out a green light from the shop, I have a good chance of getting what is to me a green light. That’s why assigning the property “green” to light can be valid. But if I ask someone else to get me a “holy-as-a-bishop” light, I may get a “holy-as-a-pope” light, or a light with no holiness at all. The pathways that assign the quale “green” to light are not nearly as arbitrary as those that give the experience of “holiness”.
Hmm. If we encounter some alien physicists, we can ask them “What’s the wavelength of the light produced by the transition between the 6s7s and 6s6p levels of the mercury atom?”, and they’ll come back with an answer that’s the same as 546 nm in our units. If we ask them “What colour is that light?”, we have absolutely no guarantee that they’ll come back with an answer that’s the same as “green”.
It’s not unreasonable (IMO) to assume that any aliens capable of communicating with us will understand the concept of “length”. It is unreasonable to assume they’ll understand the concept of “colour”, and almost impossible to assume they’ll have the same concept of “colour” that we do.
Not when the same effect (green) can occur when your light isn’t present. As usual, I’ve already said that attempts can be made to analyze an experienced event by (arbitrarily) breaking down the experience into (arbitrary) components. Under one such break-down, one of the components of the experience is referred to as “light”. In that context “light” certainly becomes a necessary causal factor. But I see no justification for the stronger claim that light is the only causal factor.
If what I see is light? For the umpteenth +1 time, I do not see “light”, I see “green”; and yes, I can, and sometimes do, call the light green, but my doing so is a matter of commonplace convenience, not accuracy (the same way I say “the sun is setting”). This is tiresome.
Once again, you take my words, deftly excise them from their original context, then ask questions about something I’ve never said. This is very tiresome.
In its original context, the sentence “I suppose I could start calling experiences of that nature ‘red’”, clearly refers to the sentences immediately preceding it. Read those sentences and you’ll get your clarification.
Wow. This time you didn’t just take me out of context, you actually edited my post to do so. The original post was “Of course it is, unless you take my answer out of context yet again.”.
Sorry, but I asked first: How do you justify bringing a continuum into my experience?
Sentient, what’s going on? It looks for all the world like you’re furiously building strawmen and semantic carousels from my posts instead of tackling their content. If you truly wish to understand my point of view in order to see where we diverge, you’ll have to take that view as it stands, not re-interpret through your own viewpoint. Why are you (seemingly) trying to chase me into some sort of semantic contradiction? If there is an underlying purpose for doing so, please tell me what it is and we can debate it straight-up.
(Upon preview, I see that Tevildo’s viewpoints are virtually identical to my own. If you care to continue our portion of the debate, please feel free to do so. However, if we’ve reached an impasse (not to mention that you’re starting to get dogpiled), I’ll bow out and just monitor your exchange with Tevildo, contributing only if necessary.)
I would change ‘the real world’ to ‘other experiences’.
This fallacy is called ‘begging the question’
I don’t. As long as it happens, I’m cool with it.
I wasn’t brought up in the Western culture, so I’m not familiar with this reference.
Right now I’m seeing a monitor surface with rich visual details. Presumably, even after passing through the LGN, it still takes non-zero time to initiate the cascade in the occipital cortex. That delay gives rise to my use of ‘culmination’.
I didn’t prefix ‘mystery’ with ‘eternal’, so drop the strawman.
The specifics are besides the point, just that wavelength alone explains squat.
“Light” !== “Pure monochromatic light above a certain intensity”. Hope that clears it up.
So would you say that the “colours” perceived by a synaesthete are not actually colours? That when a sound (say) produces a particular neural effect that in the non-synaesthete is produced by light, the synaesthete is wrong to say “the sound is green?”
nods * - I don’t intend to attack this position, just the isolation of visual phenomena to purely visual physiology. I appreciate that you may regard the division of neural physiology as a whole into “visual” and “cognitive” as being arbitary - if so, I don’t think I have any reason to disagree with you. You may continue to disagree with me, of course.
Yes, I agree that there are areas of our consciousness in which most people exhibit great similarity, and areas where we don’t. My point is that “colour” and “holiness” are merely different examples of such areas, and “colour” is not something that exists in and of itself, outside consciousness.
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