For those of you who were not alive in the 1980's, Crystal Pepsi was a failed gimmick where Pepsi Co. created a soda that tasted like Pepsi, but had no color. It is the best metaphor that I could find to talk about Reductive Physicalist theory, despite the fact that it shows my advanced age. I will come back to why this is the perfect metaphor in a bit, but first we need to learn about about Reductive Physicalist Theory.
This particular school grew out of an intense desire to stay in the realm of reality but still reject Subjective Relational theory. For the sake of brevity, I'm not going to bring up the whole "What is Reality" question, so lets just assume that there is a reality and that we and the color we are talking about are in it. In order to stay in reality the Reductive Physicalist turned to science to guide the way.
The Reductive Physicalist approaches color in terms of the surface qualities that are specific without relying upon experiences. So where the Subjective Relationalist would say "The apple looks green in this light" the Reductive Physicalist would say that "The surface spectral reflectance of the apple is green."
What they are attempting to measure is the amount of light the surface is reflecting. These reflections (surface spectral reflectances or SSRs for short) are presented in purely scientific terms, and makes distinctions that the naked eye cannot see. It is important to note that while SSRs can be a color, a color cannot be an SSR. Red, for example, is a spectrum of SSRs that we could say belong in a family together, but are NOT in anyway actually connected since their SSRs are not the same. In this theory two colors may look identical but they may not be the same if they have different SSRs. The Reductive Physicalist calls this phenomenon meta-meters. Let's take a look at an example of this phenomenon:
While the blue shades appear fairly constant in direct sunlight, under different lighting conditions there is a color shift taking place that shows us that the SSRs of each of these shades is in fact different. This phenomenon is how the Reductive Theorist attempts to deal with the problem of the "standard viewer" because it doesn't matter who the viewer is, we are talking about the science of light waves and nothing else. Even if someone is red/green color blind, it will not matter. Because it is not about what we perceive but about what science tells us is there.
There are some problems with this particular approach. Since this theory relies so heavily upon science, lets start with the scientific issue first. Measuring the SSRs only really works for objects that are opaque. Anything that is transparent or liquid (even the more opaque liquids such as milk) and light sources themselves are very difficult to measure. This is because they either have no surface to speak of OR the surface shifts. It is possible to have a cup of soda, for example, that has multiple SSRs depending on what part of the "surface" you choose to do your light reading. Which leaves us with a difficult problem: we can see that our soda has color, but if we have no unified SSR to identify, then we have no way of understanding the color. Which means it is impossible for us to duplicate, discuss or even name the color in any meaningful way.
Leaving aside the science of how we measure color in transparent verses opaque objects, many people reject this approach because it relies upon data that cannot be seen with the naked eye and is contrary to our experience. While a reductive color theorist would say it is a small price to pay for removing the "standard viewer" what they've really done is simply dress the problem up in a really fancy scientific hat. We still have an issue of standard viewing conditions, we're just now talking about them in terms standard measuring conditions. But again, we are forced to ask the question, who decides what and how do we measure the SSRs.
There is also the issue of color relationships; we have an intuition that orange is closer to red than purple. This is based off of both our practical experience seeing the colors together and also from learned knowledge. We also understand the difference between what are called "unique" hues and what are called "binary" hues (colors created through the mixing of two unique colors.) And from these two pieces of information we can extrapolate how to create orange through the mixing of two unique hues, namely yellow and red. But if the Reductive Physicalist is to be believed there is no way that we could KNOW that orange is closer to yellow than purple--let alone mix orange. How could we if we cannot see the SSRs?
Anyone who has done any sort of art or even snapped a quick photo with Instagram can attest to the fact that the color experience changes based upon physical phenomenon; the surrounding objects, the color of the light, how light or dark it is and the light (or device) that said art is viewed in. Are we to measure separate SSRs for an object in all these different permutations? And which is the true SSR? And how is this even remotely close to what our real life experience is like? It is so utterly foreign to our every day experience, it is very difficult to accept this approach. It seems utterly crippling to approach color in this way.
It is here that I return to my initial reference to Crystal Pepsi. People rejected it because they didn't think it felt like real soda. In fact, the majority of people complained that it tasted "wrong" much to the consternation of scientists who argued that on paper it was the same soda, minus the colorant--which was flavorless. But the experience of seeing is a powerful one and the truth is that when folks didn't see the expected color, the taste became different to them in a real way that defied the scientific. It is this same problem that we face in Reductive Physicalist theory for color. It is difficult to accept of a color theory that claims to be based upon physicality but rejects the physical experience that we ourselves are having.
What do you think? Would you be able to accept a scientific explanation of color that was contrary to your physical experience?