Question Is there any objective, scientific way to prove that we all see colours the same? I know it's one thing for two people to point at an object and agree on its colour, even the particular shade, but there's no way that I can tell whether or not the next person in line sees everything in shades of greys, or in negative. We can even study how light interacts with objects and enters our eyes, without truly knowing if one person would see everything the same if he suddenly were able to see though another's eyes. So, is there any proof that we all do see colours the same? Maybe even proof or evidence to the contrary? If that's so, I must say that you're all missing something great from where I can see.

Accepted:
October 28, 2008

Comments

This is a much discussed question, which often appears in the guise of the "inverted spectrum hypothesis": One might wonder whether some other person sees what you see as red the way you see green, etc. It turns out it can't be quite that simple, but one might nonetheless wonder whether we do all see colors the same way.

In fact, Ned Block has argued that there is some empirical evidence that we don't all see colors the same way. (See this paper.) It goes without saying that this is very controversial.

There are objective scientific tests which show that we don't all see colours the same, such as the Ishihara test for colour vision. Most people don't even see the same "colours" out of both eyes. For many people the left eye might see things more saturated than the right.

The question should also perhaps be refined a bit. Shouldn't it be formulated as whether we see things (objects, surfaces, volumes etc.) in the same colours? "Do we see colours the same?" as it stands seems to mean, "Do you see red as I see red?" But this presupposes that we are both seeing red, and then the question seems to ask whether we see it the same way, for example with the same degree of saturation or exactly as blue.