This appears blue. This appears yellow. And this appears green. Those of us with normal color vision can probably agree. But that doesn’t change the fact that color is an illusion. Color, as we know it, does not exist in the outside world, beyond us, like gravity or protons do. Instead, color is created inside our heads. Our brains convert a certain range of the electromagnetic spectrum into color. I can measure the wavelength of radiation but I can’t measure or observe the experience of a color inside your mind. So, how do I know that when you and I look at a strawberry, and, in my brain, this perception occurs, which I call “red,” that, in your brain, a perception of green doesn’t occur, which you have, of course, also learned to call red We both call it red. We communicate effectively and walk away, never knowing just how different each of our internal experiences really was.

Of course, we already know that not everybody sees color in exactly the same way. One example would be color blindness. But we can diagnose and discuss these differences because people with the conditions fail to see things that most of us can. Conceivably though, there could be ways of seeing that we use that cause colors to look different in different people’s minds, without altering their performances on any tests we could come up with. Of course, if that were the case, wouldn’t some people think other colors look better than others? Or that some colors were more complimentary of others? Well, yeah, but doesn’t that already happen? This matters because it shows how fundamentally, in terms of our perceptions, we are all alone in our minds.

Philosophers call these ineffable, raw feelings “Qualia.” And our inability to connect physical phenomenon to these raw feelings, our inability to explain and share our own internal qualia is known as the “Explanatory Gap.” This gap is confronted when describing color to someone who’s been blind their entire life.

Tommy Edison has never been able to see. He has a YouTube channel where he describes what being blind is like. It’s an amazing channel. In one video he talks about colors and how strange and foreign of a concept it seems to him. Sighted people try to explain, for instance, that red is “hot,” and blue is “cold.” But to someone who has never seen a single color, that just seems weird. And, as he explains, it has never caused him to finally see a color.

Some philosophers, like Daniel Dennett, argue that qualia may be private and ineffable simply because of a failure of our own language, not because they are necessarily always going to be impossible to share. There may be an alien race that communicates in a language that causes colors to appear in your brain without your retina having to be involved at all. Or without you having to have ever needed to actually see the color yourself. Perhaps, even in English, he says, given millions and billions of words used in just the right way, it may be possible to adequately describe a color such that a blind person could see it for the first time. Or you could figure out that, once-and-for-all, yes or no, in fact, you and your friend do not see the same red.
But for now, it remains the case that we have no way of knowing if my red is the same as your red. Maybe one day our language will allow us to share and find out, or maybe it never will. I know it’s frustrating to not have an answer, but the mere fact that you guys can ask me about my internal experiences, and the mere fact that I can ask my friends and we can all collectively wonder at the concept of qualia is quite incredible, and also quite human.

Credits: Michael Stevens: Producer/Host of Vsauce1