The illusion of qualia : why the sky is not blue

A recent online discussion did its usual thing of degenerating into philosophy about qualia and suchlike, so I want to record some of the main points that seem important to me. In particular, it felt like there was an attempt to define colour to be something explicitly and exclusively materialistic, e.g. blueness is a certain wavelength range of a photon, which I think is absolutely impossible. This has similar vibes to an earlier discussion in which colours were outright claimed to not be qualia at all, which felt really bizarre, so even if I misinterpreted something, this post should still have some value. I will try to set forth why colours are indeed qualia, and why we may meaningfully speak of objective and subjective reality despite only ever having direct access to the subjective version.

Here is how the colour situation seems to me.

Objects reflect or emit photons depending on their material properties. The photons are received by my eye and then my befuddled, beer-addled brain does its best to form an image out of them.

This corresponds to stuff that occurs “out there”. In this regard we do have some limited form of knowledge of the external world. We can only know it through perception, which is erroneous and always incomplete, but rarely wholly flawed. Repeat observation under different circumstances lets us establish things with arbitrarily high confidence (I would even argue for a kind of true certainty, but that can of worms can be left safely closed).

What this means is that I can establish that there is something out there that causes blueness in here. Under the same circumstances, the sky will always look blue. Does this mean that I can say that the sky itself, therefore, is blue ?

No.

Well… maybe. Sort-of. Not really.

That is, we can say, “the sky is blue” as a convenient shorthand. I don’t need to stipulate the exact functionality of the eye or the precise meteorological conditions. We all know that what I really mean is under typical conditions with typical human eyes I will see a colour corresponding closely to other objects that are prone to inducing a similar experience (albeit themselves sometimes under different conditions, but with the experience itself being qualitatively similar). So as a shorthand there is no problem with saying “the sky is blue”; indeed, it would be monstrously stupid not to use this in everyday speech.

But strictly speaking, blueness itself, in my opinion, is very much “in here” and never to be found “out there” at all. If I never experienced anything but the light from sodium lamps, my whole colour experience would be profoundly, utterly different. I would have no way to know that there could be such a thing as “blueness”. Knowledge that photons could have wavelengths unfamiliar to me would not help me imagine blueness any more than I can presently imagine the colour of 21cm radio waves. I would know that experiencing other colours might be possible, but absolutely no knowledge whatsoever of the experience itself. Mary is trapped in her room forever…

(Leaving aside the minor detail that since we can perceive colours without photons present at all, e.g. phosphene vision by tactile stimulation, so perhaps some level of blueness is always present in the noise.)

And even photons purely of the specified wavelength are of no help here in defining colour : not, at any rate, the qualia of colour. True, if we receive nothing but those photons and we all have similar eyes and brains we should all experience much the same thing, but that does not mean the photon itself is blue. It only means that induces the same qualitative experience given our similarities. It doesn’t cause blueness in other animals - or the severely colour-blind - any more than the 21 cm waves cause colour to be induced in me.

Likewise the famous "no red pixels" illusion : I do not think it is correct to say that the strawberries appear to be relatively red, they appear actually to be red to me. Hence photons can only be said to induce colour, not to have colour in and of themselves. Colour is not something they have independently of being observed. It makes no difference at all if one person perceives red while another sees green, the photons themselves will have the same energy and wavelength.

To further emphasise the point : if we take only a small section of the image, we will see blue, whereas if we see the whole image, we see red strawberries on a blue background even though the wavelength being received from the original section has not changed. Hence colour is not wavelength. The same wavelengths are capable of inducing different colours in different situations.

This means there is no such thing as absolute, objective colour. Certainly blueness is something I do indeed perceive, though. A multitude of objects are capable of inducing blueness in a plethora of conditions, but there is no need except (importantly !) convenience to say that the objects themselves are blue. The properties of the photons are “out there” are invariant, the experience of colour is entirely internal and subject to a host of both external and internal influences. It is only that conditions (both internal and external) are so frequently similar that we feel we can say that blueness is a property of the objects themselves. Aliens living on the Planet of the Sodium Lamps* would not see this at all, and there is no reason my claim on reality should be greater than theirs.

* Worst Doctor Who episode ever.

Hence, it does not really matter if my blue is the same as your blue. Blueness is something the brain ascribes, not something that is found externally. Someone not perceiving blue when others do is in no way “wrong” or “mistaken”, in the way they would be if they measured the wavelength incorrectly. They just have a different, equally valid perspective.

At least that’s my opinion anyway : we can surely say “objects are blue” when analysing scientific properties, because we all understand the contextual convention, but we would be extremely foolish when we go beyond this and start discussing the nature of reality. 

This is how I try to square the common-sense notion that "bananas are yellow" with the more rigorous examinations that show that colour is a purely internal, photon-independent phenomenon. It depends on the context in which we speak : in everyday life we all implicitly assume common viewing conditions, but this does not apply when we're discussing things at a much more fundamental level. We can legitimately say that objects "have" colour... but the meaning of this statement is categorically different from the subjective experience of colour itself, which is an internal matter we can never communicate to anyone.

As also pointed out, dictionary definitions are no help without common experience. Once you've experienced blueness, you can define it in relation to those conditions that induce it - but knowledge of the wavelength range of a photon still tells you nothing about the experience of it. Yet that definition may very well still be extremely useful : knowing I need photons of a certain wavelength range for an experiment, I can set things up completely independently and don't need reference to my own prior internal experience at all. So saying that a wavelength range corresponds to a certain colour has genuine value. 

This, then, is the sense by which I mean we can speak of objective and subjective reality. Strictly speaking, the number I read off an instrument is experienced subjectively, but if I give you that number to reproduce a "blue" photon, you can do so. In contrast if I just tell you I saw something blue, and you have never seen something blue before, I have told you absolutely nothing; you have no way at all to recreate what I experienced. The objective and subjective clearly are qualitatively different.

To sum up : photons induce an internal subjective experience of colour, depending on their own wavelength, our viewing apparatus (our eyes and brain), and, crucially, the surrounding context of other photons. We can say that objects have colour in that they reflect a certain fraction of photons of a certain wavelength range, but this is not at all the same as subjective experience : seeing red is different than knowing the numerical values of the corresponding photons. Indeed, if we define colour purely as a wavelength range, when we objectively measure the strawberry image, we will find the entire image is blue - which it clearly isn't !

Colours, then, are indeed qualia, in a particular definition : they are subjective experience and nothing else. Our brains may well be assigning completely different experiential qualities to different wavelengths in different situations (certainly wavelength does not uniquely define the experience); we have no idea if my red is the same as your red. But colour could also be said to "be" wavelength... but this is in a categorically different sense to that of actual perceived colour. It is not unreasonable to use these two radically different definitions, but the context needs to be rigorously understood. The former is crucial for certain philosophy discussions; the latter infinitely more useful for scientific analysis.

In short, the titular claim that the sky is not blue is correct, but if I don't specify the context, I can rightly expected to be viewed as mad. 

(We need not even approach the kettle of fish that is astronomical colour, which is something else again.)