A lot depends on who "we" are. Suppose we are complete achromats, so that we only see "achromatic colours", greys, blacks and whites. Now it is clear enough that there is a colour "we" haven't seen. Red is an example, and so are all the other chromatic colours. Now what if "we" is the whole human race at all times. We can imagine that we take the set of all the colours that anyone has ever seen. Question: are there more? Wittgenstein is someone who takes a negative line on this. Are they colours that others might see which we do not? '. . . [W]e would still not be forced to recognize that they see colours that we do not see. There is, after all, no commonly accepted criterion for what is a colour, unless it is one of our colours' (Wittgenstein, Remarks on Colour I, 14). We do not use colour language just by pointing to colour samples and naming them. It takes more to be talking about colours than that (III, 58). The idea of little coloured patches of colour is not a "more fundamental" idea of...

Clearly what is dependent on the existence of mental processes is not therefore illusory. Unlike many things, the existence of mental processes is dependent on the existence of mental processes. It does not follow that mental processes are illusory. But I think it should be said that there is little or nothing that philosophers have provided that could help us to understand what it means to say that a colour, the colour pink, for example, exists, or exists only, in the mind, or outside of it, for that matter. The mantis shrimp has at least eight colour receptors - it can also perceive circularly polarized light and its direction of rotation! - but the poor old thing does not have an awful lot in the way of a mind. Mind you, it can deliver a punch (with one hand!) at 10,000 g, enough to boil the water in front of it.

Here is an answer I gave on February 10 2010. For your reductionist friend I would answer that the perception of black is positive - it is not a null perception, in some sense, but nor is it the perception of nothing, so that nothing (or Nothing, rather) looks black - presumably It doesn't look any colour. I also want to add that black is not in the spectrum, obviously, for what that is worth (nothing, actually) and that "black" and "dark" have different meanings. If you take a dimmer switch and gradually increase the light in a completely dark room, as the illumination goes up, the reds get redder, the greens greener, and amzaingly the blacks get blacker! What does this tell us? From Feb 10 2012 This is a fairly frequent concern. The correct answer is that there is a sense of "colours" in which black and white are not colours (they are not chromatic colours) and a sense in which they are colours (they are achromatic colours). So if we count the achromatic colours (black, white and grey) as...

In physics, if colour is associated with wavelength or frequency, then blue is at the shortwave or high frequency end of the spectrum and red at the longwave or low frequency end. Does this tell us anything about the psychology of colour? It was this perceived deficiency that caused Goethe to seek a formula for colour that did make the connection. Thus for him blue is darkness seen through an illuminated semitransparent medium. And yellow is light seen through a "thickened" or semi-transparent medium. This begins to explain why blue is as it is said a receding colour and red an advancing colour. What your question asks for is a connection between the physics and the phenomenology and emotional effects of colour. These were treated perhaps rather dismissively by Wittgenstein in Remarks on Colour , published in 1977.

You are absolutely right. Neither colour nor a colour is spatially extended, and a colour like pink is exactly not like a gas that fills up a volume or spreads itself, perhaps very very thinly, over a surface. That is a category mistake. Nor do colours have thicknesses. I am delighted to see a recognition of this important point, to which I have found very little attention paid in the literature on the philosophy of colour. Though I tried to get started sorting out the tricky logic of "pure" colours, as Wittgenstein calls them (to be contrasted not with impure colours but with things coloured the colours), in Chapter 7 of Colour: a Philosophical Introduction , published in 1987 and 1991, but that was only a beginning. Consider two patches of the same red, patch A surrounded by green and patch B surrounded by red. We can say that the colour of patch A is identical with the colour of patch B. But then as G.E. Moore pointed out (in his early paper on "Identity") it follows, or seems to,...

Colour relationalism tells us that colours are relations between perceivers and the objects that they perceive. (This gets a bit tricky of course if what they perceive is a colour, because then what they perceive is a relation between themselves and a relation between themselves and a colour, or rather, a relation between themselves and a relation between themselves and a relation between themselves and a colour.) "Colour phenomenology" doesn't mean an awful lot: just the (apparently) obvious facts about colour and classifications of things having to do with colour based on these facts. Phenomenology in this sense has seemed to oppose colour relationalism. We don't seem to see relations between ourselves and tomatoes when we see red tomatoes. What we see is a property flattened on to the surface of the tomato! So colour relationalists have to work a bit to square their view with the phenomenology. Without meaning to be rude, might I inquire whether this is an essay topic you have been set? Why are you...

In general, the fact that everyone agrees on something is not really enough to make it true. The fact that everyone believes that Brazil is the best team in the World Cup doesn't mean they will win the Cup, or be the best team. On the other hand, if I believe that Jennifer is my best girl, then she is my best girl. If we all thought that blue was the best colour, then it would be: "our best colour", so perhaps it could be said to be the best colour. So I think "the best" is used in two ways in your excellent question. (1) It just means "the best" by some external standard , goal-scoring perhaps, so that "Brazil is the best team" means that Brazil will win the Cup. (2) It means that blue is our best colour, the best colour of all of us, the one we all like the most, then it is the best colour - of all of us - though not in the first sense. I think perhaps it is a little difficult to know how to understand what the fact of being the best colour is. There is something good about each of...

Why should the redness of a red object not be a fact? We say of this tomato here, "Look, it's red." We know this proposition is true because we can see that the tomato is red, just as we know that the tomato is heavy - heavy for a tomato, anyway - because we can weigh it in our hand. The same thing applies to shape, supposing that we come to know the shape of something by visual inspection rather than by measurement. Now if our red object is viewed in green light, it turns black, because the light with colours at the middle of the spectrum, the green light, is complementary to the red light that the tomato "reflects", if we can say this. (In what way is a tomato not like a mirror?) The red tomato "absorbs" the green light. I think that your question goes deeper, however. This redness of the tomato might be thought not to be a physical fact, if you believe those philosophers who are impressed by the existence of an "explanatory gap", as it has come to be called, between physical and phenomenal...

"Opposite" is not in this connection a very well-defined word. "Complementary" is more precise, but then we should inquire: physical additive complementary, i.e. such as to cancel the test colour in light superposition and produce neutral or white; physical subtractive complementary, i.e. such as to cancel the test colour in pigment mixing and produce neutral or black; psychologically complementary - it is unclear what this would mean, but it could have to do with the placing of the test in a colour space based on the psychologycal "unitary" hues, i.e. those that do not look as though they contain a "trace" of any other hue in the space. There are some interesting studies of brown, and one of them (I think) is my own, in Jonathan Westphal, Colour: A Philosophical Introduction, Blackwell, Oxford, 1991 - the chapter on "Brown". Are we allowed to sound our own trumpets on this website? I'm not sure, but anyway this might get you started. The thing to remember is that brown surfaces have roughly the same...

This is a fairly frequent concern. The correct answer is that there is a sense of "colours" in which black and white are not colours (they are not chromatic colours) and a sense in which they are colours (they are achromatic colours). So if we count the achromatic colours (black, white and grey) as colours, then black and white are colours. (Brown is an interesting case, as it is a colour which is partially achromatic.) In the same way, we can ask whether zero and infinity are numbers. Usually they are treated as numbers, and they have their own mathematical symbols. We can manipulate them in calculations and so forth. But in another sense "zero" denotes the absence of a number, and so does the symbol for an infinite number. Q: "How many chickens were there in the kitchen?" A: "A number." Q: "What is the number?" A: "Zero"! Aristotle's view was that the smallest number is two, as one of something is not a number of somethings. "There were a number of people there." How many?" "One." In...