perhaps the answer to this takes a realism vs. idealism aspect.

Under the umbrella of realism- red must represent some state of external reality that when manifesting visually becomes “red.” Perhaps this means photon wavelength, or perhaps some other external means we’ve yet to understand. Then red simply exists as a verbal pointer to that specific external state (whatever it may be) that is experienced as red.

Under the umbrella of idealism- this entire question loses its significance. Perhaps reality is solipsistic? Perhaps red is frequency of mind-thought experiencing itself as “red” and we don’t have to worry about subjective discrepancies of whatever “red” is because there’s only one objective/subjective reality? Could go a billion ways with that umbrella. In that sense, red is only an experience whichever direction you want to take it. Asking what the true nature of red is loses all meaning

red must represent some state of external reality that when manifesting visually becomes “red.” — Mp202020

Well, that's not right, either, it seems. The red of a sunset is very different to the red of a sports car, or the red of a sore eye.

Indeed, the presumption is that there is something that all red things have in common - but why should that be so? We seem to use the word "red" for a range of different things. And why shouldn't a word be used in this way?

So red need not be "a verbal pointer to that specific external state (whatever it may be) that is experienced as red"...

And we've already agreed that red cannot be only an experience...

But if red refers to the experience, then when you say “red” it refers to your experience, but when I say it it refers to my experience. If we are going to be talking about the same thing then we need something that we both have access to. — Banno

If "red" is just in your mind, when you ask for a red pen, how is it that the person you are asking hands you what you want? — Banno

I can ask someone to recommend a funny movie, and they can deliver, but I don't think it makes much sense to treat being funny as some mind-independent property of movies.

So the reasoning behind your question appears to be a non sequitur.

I agree, “red” can mean many things, there are many different shades upon the light frequency that would all be considered “red” but have a distinct difference, thus their different “shade” of red.

At a certain point on the spectrum, red starts to become orange looking. It becomes more and more orange, eventually becoming a shade of “orange” rather than a shade of “red.” What draws that line?

Interesting question, but it doesn’t necessarily address my direct point. Any color, not matter the shade, how can we know it’s experience is as shared as the cause of its experience?

If you can be assured there is radiation, why can't you be sure there's red? — Hanover

This question is a little confusing. It's like asking "if you can be assured there is heat, why can't you be sure there's pain?"

I can be sure that there's red and that there's pain, but given our scientific understanding of physics and biology and psychology, it seems to be that red and pain are properties of minds, not properties of pens and fire.

The issue isn't over whether or not these properties exist, but over where in the world these properties exist. At least when it comes to colour, some appear to be locating them in the wrong place.

The reason a quality like “color” doesn't extend beyond the object is because it is a quality of the object, not the mind. The changes in color within objects and the differences between them are due to changes in the objects themselves, like when a banana turns green to yellow as the chlorophyll breaks down. — NOS4A2

When the structure of some object changes the wavelength of the light it reflects changes, and when the wavelength of the light changes the colour we see changes, because the colour we see is determined (at least in part) by the wavelength of the light that stimulates the eyes.

It doesn't then follow from this that colours are properties of these objects.

I can be sure that there's red and that there's pain, but given our scientific understanding of physics and biology and psychology, it seems to be that red and pain are properties of minds, not properties of pens and fire.

The issue isn't over whether or not these properties exist, but over where in the world these properties exist. At least when it comes to colour, some appear to be locating them in the wrong place. — Michael

But doesn't this just raise the age old problem associated with Locke's primary and secondary properties distintiction? You've identified pain and color as secondary qualities not inherent in the object itself and have suggested there are primary properties independent of the observer that exist in the object.

If we know that the blueness of the chair is only in my head, what is an example of a property of the chair that is in the chair itself even if my head (or nobody's head) never existed?

what is an example of a property of the chair that is in the chair itself even if my head (or nobody's head) never existed? — Hanover

The existence of its atoms and their propensity to reflect light at certain wavelengths.

The sorts of things described by the Standard Model are mind-independent. Other things like smells and tastes and colours and pain are mental phenomena, produced by brain activity in response to bodily stimulation.

Wavelengths travel beyond the objects but the color never does. If the color is determined in part by the wavelength, how is it that if light bounces off an object at a certain wave length, we do not see the color anywhere outside of the object?

Wavelengths travel beyond the objects but the color never does. If the color is determined in part by the wavelength, how is it that if light bounces off an object at a certain wave length, we do not see the color anywhere outside of the object? — NOS4A2

Your question is misguided. Light stimulates our eyes, signals are sent to our brain, and the brain produces a visual percept with such qualities as shape and colour and depth. Our minds and conscious experiences don't literally extend beyond the body to encompass distal objects.

At a certain point on the spectrum, red starts to become orange looking. It becomes more and more orange, eventually becoming a shade of “orange” rather than a shade of “red.” What draws that line? — Mp202020

We do, don't we? I agree with you that it's ok that "red" refers to a range of frequencies (that might vary per setting.). But when it starts changing to reddish orange, or purple (bluish red) or burnt sienna (reddish brown), these terms come from shared human experience, right?

Your question is misguided. Light stimulates our eyes, signals are sent to our brain, and the brain produces a visual percept with such qualities as shape and colour and depth. Our minds and conscious experiences don't literally extend beyond the body to encompass distal objects.

Then how come the color of the percept isn’t outside the object if the light is outside the object?

Then how come the color of the percept isn’t outside the object if the light is outside the object? — NOS4A2

Your question makes no sense. Colour is a property of visual percepts and visual percepts exist inside my head. So what does "the colour of the percept isn't outside the object" even mean?

No such thing exists in your head. I can take a picture of any object and it will undoubtedly show that it is outside your head, and this includes all colored objects except your brain.

No such thing exists in your head. — NOS4A2

It does.

I can take a picture of any object and it will undoubtedly show that it is outside your head — NOS4A2

I don't know what this means. But digital cameras work by measuring the energy of the light that strikes its sensors, using this to determine which of the pixels to turn on and at what intensity. Our brains probably work in the same sort of way, but with neurons in the visual cortex in lieu of phosphors on a screen.

We’ve examined many brains and discovered no such thing.

I don't know what this means. But digital cameras work by measuring the energy of the light that strikes its sensors and uses that to determine which of the red, green, and blue pixels to turn on and at what intensity. Our brains probably work mostly the same way, but with neurons in the visual cortex in lieu of phosphors

It means that if you see a banana, you’re not seeing one in your head. I can record you looking at a banana, the location of both your head and the banana, and discern that nothing about the banana is in your head.

It means that if you see a banana, you’re not seeing one in your head. I can record you looking at a banana, the location of both your head and the banana, and discern that nothing about the banana is in your head. — NOS4A2

I'm not saying that the banana is in my head. I'm saying that colours are in my head. They are a property of the visual percepts that are produced by activity in the visual cortex.

We’ve examined many brains and discovered no such thing. — NOS4A2

Sure we have. It's how we make sense of synesthesia, dreams, hallucinations, variations in colour perception, and so on. Visual phenomenology is distinct from distal objects and proximal stimuli. The second and third are often the causal explanation for the first, but that's all there is to it. Yours is the mistaken, naive view that projects the properties of the first onto the second.

I'm not saying that the banana is in my head. I'm saying that colours are in my head. They are a property of the visual percepts that are produced by activity in the visual cortex.

We’ve never found any of those, either. Rather, it appears to be a property of the object.

Sure we have. It's how we make sense of synesthesia, dreams, hallucinations, variations in colour perception, and so on. Visual phenomenology is distinct from distal objects and proximal stimuli. The second and third are often the causal explanation for the first, but that's all there is to it. Yours is the mistaken, naive view that projects the properties of the first onto the second.

I do accept the naive view. But no, we haven’t found any percepts or phenomenon as you describe them in the head, and we’ve looked. Therefor, phenomenology doesn’t deal with reality.

Rather, it appears to be a property of the object. — NOS4A2

A colour is a quality of the object, not a property.

Some people describe the colour of the dress in this photo as black and blue, others as white and gold. They can be looking at the exact same photo on the exact same screen, their eyes reacting to the exact same wavelength of light. And yet they see different colours. This is explained by differences in the way their visual cortex behaves in response to optical stimulation.



And then manual stimulation of the appropriate areas of the visual cortex can cause people to see (coloured) things.

What more are you looking for?

Colours are secondary qualities of the objects. If the banana is yellow or green, it doesn’t influence its properties or how affects me when I eat it.

No doubt the image of dress appears different to different people. It first appeared to me black and blue when I first looked at it, now it is a light blue and goldy-brown. This indeed suggests a difference in the workings of the body.

But we know the medium also has something to do with it, as we know the actual dress is blue and black. As reported, everyone who saw a difference in color on the screen saw no such difference upon seeing it in real life. For example, we’re not actually looking at a dress, but a digital image as it appears on a backlit screen. If you place the image in a program, choose a spot, and get the color value, that never changes.

So while I can’t explain it in terms of naive realism, if it is strictly limited to artificial conditions, I don’t think it suggests phenomenology.

So while I can’t explain it in terms of naive realism, if it is strictly limited to artificial conditions, I don’t think it suggests phenomenology. — NOS4A2

But it's the same distal object and same proximal stimulus, yet a different colour experience. So how does that not suggest phenomenology? Any differences in colour experience must be explained by differences in the body or brain.

See also neuronal basis of perception:

In particular a stimulus can be perceptually suppressed for seconds or even minutes at a time: the image is projected into one of the observer's eyes but is invisible, not seen. In this manner the neural mechanisms that respond to the subjective percept rather than the physical stimulus can be isolated, permitting visual consciousness to be tracked in the brain.

...

In spite of the constant visual stimulus, observers consciously see the horizontal grating alternate every few seconds with the vertical one.

...

A number of fMRI experiments ... demonstrate quite conclusively that activity in the upper stages of the ventral pathway ... follow the percept and not the retinal stimulus.

It seems to me that the science is incredibly clear. Conscious experience is in the head. It is usually caused by and covariant with some external stimulus, but they are nonetheless distinct. There really is no place to deny it.

Even if you want to say that colours are also properties of mind-independent things, you simply cannot deny that they are (also) properties of mental phenomena. It is the only way to make sense of dreams, hallucinations, synesthesia, and variations in colour perception – all of which are real.

But it's the same distal object and same proximal stimulus, yet a different colour experience. So how does that not suggest phenomenology? Any differences in colour experience must be explained by differences in the body.

The distal object is a backlit screen, capable of shooting light in all sorts of different directions, or stopping light, sometimes through liquid crystal, etc. it seems to me such conditions can illicit different experiences. The dress itself did not illicit a different experience, as everyone saw it was blue and black upon viewing off the screen. This seems to me to suggest the conditions had much to do with it.

Even if you want to say that colours are also properties of mind-independent things, you simply cannot deny that they are (also) properties of mental phenomena. It is the only way to make sense of dreams, hallucinations, and variations in colour perception – all of which are real.

I can deny that they are properties of mental phenomena because mental phenomena do not exist. Again, nothing of the sort has ever been found, and until they have, it needs to be explained in terms of things that are actually there.

Subjective accounts of states of affairs are limited by the fact that one cannot be aware of what is actually occurring behind his own eyes, or in the brain, at any given moment, so treating them as accurate assessments of the biology seems to me absurd.

The distal object is a backlit screen, capable of shooting light in all sorts of different directions, or stopping light, sometimes through liquid crystal, etc. it seems to me such conditions can illicit different experiences. The dress itself did not illicit a different experience, as everyone saw it was blue and black upon viewing off the screen. This seems to me to suggest the conditions had much to do with it. — NOS4A2

And those conditions are the same for everyone; yet we have different colour experiences. So the point stands, and your comments here are irrelevant.

I can deny that they are properties of mental phenomena because mental phenomena do not exist. Again, nothing of the sort has ever been found, and until they have, it needs to be explained in terms of things that are actually there.

Subjective accounts of states of affairs are limited by the fact that one cannot be aware of what is actually occurring behind his own eyes, or in the brain, at any given moment, so treating them as accurate assessments of the biology seems to me absurd. — NOS4A2

We have evidence of neural correlates of consciousness. We have evidence of visual perception caused by direct neural stimulation.

None of what I am saying requires substance or property dualism. I am not saying that mental phenomena is non-physical. I am only saying that colour is a property of conscious experience and that conscious experience does not extend beyond the brain. This is perfectly consistent with conscious experience being reducible to neural activity.

Again, this is the only way to make sense of dreams, hallucinations, synesthesia, and differences in colour perception – all of which are real.

And those conditions are the same for everyone; yet we have different colour experiences. So the point stands, and your comments here are irrelevant.

And it doesn’t happen under different conditions. That something novel occurs in one set of conditions doesn’t mean it applies to all. So using this one example while dismissing the rest is tantamount to pseudoscience.

We have evidence of neural correlates of self-reported visual perception. We have evidence of visual perception caused by direct neural stimulation.

None of what I am saying requires substance or property dualism. I am not saying that mental phenomena is non-physical. I am only saying that colour is a property of mental phenomena and that mental phenomena do not extend beyond the brain. This is perfectly consistent with mental phenomena being reducible to neural activity.

Again, this is the only way to make sense of dreams, hallucinations, synesthesia, and differences in colour perception – all of which are real.

We hallucinate and dream, sure, but these are biological acts, not things worthy of their own noun phrase upon which we can ascribe properties. Properties are properties of things, not actions. The body is real, while what the body does is merely an account of what the body is doing from this time and that.

In order to reduce mental phenomena to neural activity, one has to describe the neural activity, the objects involved in it, and then one can list their properties, and I suspect we’ll find no property called “color” among them unless it’s the color of those objects. White and gold or blue and black, for example, is unlikely to be the measurable properties of these objects in the brain.

Again, this is the only way to make sense of dreams, hallucinations, synesthesia, and differences in colour perception – all of which are real. — Michael

Do you really believe that the only way to make sense of dreams, hallucinations, etc is to posit mental phenomena. Definitely science does not need to posit such things, they can go on investigating "real" things like brains, neurons, cells, etc. Some people do not report out dreams, most people do not have hallucinations, have synesthesia, or problems judging and reporting out colors. Would you actually commit your self to say that if a human being did not experience dreams, hallucinations, synesthesia, or problems with color discernment they have no mental phenomena, or this is evidence they have no mental phenomena, or I do not need to posit mental phenol phenomena for this type of human being (or are you willing to change the definition of such a being as a "zombie"). I am interested in see how you carry out the implications of "the only way to make sense" comment.

And it doesn’t happen under different conditions. That something novel occurs in one set of conditions doesn’t mean it applies to all. So using this one example while dismissing the rest is tantamount to pseudoscience. — NOS4A2

If the same distal object and proximal stimulus is responsible for different colour experiences then the colours experienced in this case are not properties of the distal object or proximal stimulus.

The fact that in other scenarios we have the same colour experiences neither a) refutes the above nor b) entails that the colours experienced in these other scenarios are properties of the distal object or proximal stimulus.

And as for less “artificial” scenarios, there is empirical evidence of sex differences in colour perception.

We hallucinate and dream, sure, but these are biological acts, not things worthy of their own noun phrase upon which we can ascribe properties. Properties are properties of things, not actions. The body is real, while what the body does is merely an account of what the body is doing from this time and that. — NOS4A2

I dream and hallucinate in colour. The colours I dream and hallucinate are properties of my dreams and hallucinations. Waking experiences are of the exact same kind - neural activity in the visual cortex - differing only in their cause and intensity.

White and gold or blue and black, for example, is unlikely to be the measurable properties of these objects in the brain. — NOS4A2

There are neural correlates of self-reported colour percepts. This is how neuroscientists are able to intentionally stimulate particular colour experiences in test subjects - they know which areas of the brain to excite to have the subject see red.

Do you really believe that the only way to make sense of dreams, hallucinations, etc is to posit mental phenomena. — Richard B

Yes. We don’t explain them by positing the direct acquaintance of some distal object. I don’t dream about dragons because my eyes are open and I’m looking at a dragon in my bedroom; I dream about dragons because my visual cortex is active when I sleep.

To put it another way, if I imagine a world full of beings who do not dream, hallucinate, etc, I do not need to posit mental phenomena for these being.