This appears blue, this appears green and this appears red.
Those of us with normal colour vision will probably agree, but that doesn’t change the fact that colour is an illusion.
Colour, as we know it does not exist in the outside world, beyond our perception, like gravity or protons. Instead, colour is created inside our heads. Our brains convert a certain range of the electromagnetic spectrum into “colour”. We can measure the wavelength of radiation, but we can’t measure or observe the “experience” of a colour inside your mind.
So, how do I know that when you and I look at a coloured object (e.g. tomato), and, in my brain this perception occurs, which I call “red”, but in your brain a perception like this 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 were.
Of course, we already know that not everybody sees colour in exactly the same way. One example would be “colour blindness”, however we are able to diagnose and discuss these differences because people with the condition fail to see things that most of us can, as proven by the famous “Ishihara colour test” – the circular dots with numbers inside.
However, there is currently no way to test or, in that matter, prove that colour perception is the same for everybody. This matters because it shows how fundamentally, in terms of our perceptions, we are all alone in our minds! In fact no matter how much we explain, we can never make another person experience or “feel” what we do.
Philosophers call these ineffable, raw feelings “qualia” and our inability to connect physical phenomenon to these raw feelings, or to explain and share our own internal qualia is known as the “Explanatory Gap.”
Some philosophers, like Daniel Dennett, argue that qualia may be private and indescribable simply because of a failure of our own language, not because they are necessarily always going to be impossible to share.
Maybe one day our language will allow us to share and find out, but for now it remains the case that we have no way of knowing if my red is the same as your red.
Outmane, Consultant, Leyton France