The first question comes from +Terrill Welch:
When and how did it get decided that black and white were not colours? (This comes from Rilke's observation that Cezanne used white and black as colours and that this seemed to be something new.) -- +Terrill Welch
Black and white in language (and in our mind's eye)
Rilke is talking about in this letter, "Black Marble Clock", 1869-1871, dominated and structured by a black thing (the clock) and a white thing (the cloth). The essential quality of the painting for Rilke is that "black and white /.../ behave perfectly colorlike next to the other colors, their equal in every way, as if long acclimatized" (it's the letter dated October 14, 1907 -- if you want to read the whole passage yourself).
And this is, in a sense, exactly as we see black and white "in real life", just as any other colour. In other words, black and white are definitely colours from the point of view of (what is sometimes referred to as) the naive worldview encoded in human languages. This deeply embedded worldview doesn't change as easily and quickly as scientific theories of light and colour (more about it below), and defies any "decisions" and discoveries. Roses can still be white or red; jeans can be blue or black; soot is black, snow is white, grass is green, whatever we might have learned about optics or about human vision. In these contexts, we speak of (and think of) white and black as colours, just like red, blue or green. Not only do we speak of them, we actually see them. But it's only because our brains are so good at correcting for "white balance" and identifying constant, "local" colour of things. In other words, we see them, but not so much with our eyes as with our minds, fitting the world our eyes perceive into the conceptual system(s) built into our languages.*
Black and white in optics: light, darkness, wavelengths
hue, while "normal" colours do).
Isaac Newton was instrumental in understanding this phenomenon, when he discovered how a beam of white light splits into seven colours of the rainbow and then merges back into white again. This must have happened somewhere in the late sixties of the seventeenth century (the results of Newton's experiments were published in 1672). As illustrated by Rembrandt's painting above ("Two old men disputing") though, painters seem to have known all this intuitively much earlier (the painting is dated c. 1628). His dark backgrounds are created by layers of thin glazes of complementary colours, designed to reflect as little as physically possible, i.e. to absorb all light. His whites are thick and often strikingly pure, designed to reflect back whatever light they get.
It seems to me that if Rilke were to compare these paintings, he would have said that Rembrandt doesn't use black as colour: black is but a background, a nearly absolute darkness, a painterly version of "black hole" as it were, not a black "thing": a device to construct the painting, not to depict the colour of a thing. It's a bit more complicated with white, I think: it can be said that Rembrandt uses white "as a colour" (we "see" the old man's clothes and beard as "white" (just as we would have seen them as "white" in real life), and yet Rembrandt's whites look whiter and brighter than real "white things" (except maybe a carpet of fresh snow on a sunny day, but certainly not a man's clothes in a barely lit room). They are, in a sense, "absolute", ideal whites, the lightest lights, which seem almost to emit light in the painting (rather than merely reflect it). Not so in Cezanne's still life, where the white cloth is (more realistically) not really white (pun intended).
Black and white in the eye (photoreceptor cells)Interestingly, the eye has different "subsystems" for processing "light" and "hue" (rods and cons): it switches to the B & W (or rather: dark vs. light) vision when there isn't enough light (that's why we are taught to squint to get more accurate value judgements when we paint, artificially reducing the amount of light that reaches our retina and activating our B & W vision). Which means that, even from the biological point of view, there is a clear distinction between black and white vs. colours "proper".
this painting on the left, "The magpie", 1869), but this information is normally discarded by the brain as non-essential. The snow isn't really "white" for the eye itself, even if it is for the mind.
There are, presumably, good evolutionary reasons for our brains' behaviour: it is essential to identify local colour to recognize an object quickly, and the subtleties of light and hues fall victim to this need. Indeed, it won't do to be unable to recognize a hungry tiger quickly enough just because the colour of its fur is changed by the sunset; and it's also useful to recognize snow as snow, rather than as a variety of differently coloured substances depending on the time of the day and the weather. But insofar as it is not a matter of survival, this strategy robs us from perceiving all the beauty, the rich variety of the surrounding world.
This, I believe, is the core of Claude Monet's quest (and to a lesser extent, of the Impressionist movement in general). An impressionists painter's job is to "suspend" the mind's tendency towards simplification and idealization of visual input, to "catch" more of the colour information the eye registers and "show" this richness to others. So, for Monet, there are no such colours as "white" and "black"; indeed, there are actually no "black" and "white" in nature at all. He is interested in the non-whiteness of the white, the real colour variety of what we usually call "whites". That's why Cezanne (reportedly) said: "Monet is just an eye, but what an eye".
Black and white: real vs. ideal, material vs. spiritual, form vs. substanceTo sum up, not only black and white aren't colours in the material, real world our eyes perceive, but there are no black and white in nature at all: a light source is never an ideal mixture of all wavelengths (that is, it's always shifted towards some colour) and any surface we see absorbs some light (hence, it's never absolutely white) and reflects some light (hence, never absolutely black); and our eyes diligently register variations of hues everywhere, most of which are never perceived by our minds: they "see" things as white or black just as easily as they see them as red or green.
Earlier, I described this distance between the eye and the mind as an evolutionary strategy of simplification, but there is an alternative school of thought, which runs, in various forms, through the whole history of our civilization: our minds can grasp spiritual (even divine) idea(l)s, even if they are represented in nature only imperfectly. The whiteness of snow is, then, not just a simplification necessary for material survival, but a sign of our ability to live in the world of ideas, our connection with the Divine, our ability to see the real, non-material beauty, the Platonic ideas, the spiritual substance of things (of which we see only superficial forms "in real life"). An artist's job, then, is not to suspend idealization, but to strengthen the mind's connection to the ideal (this, by the way, is the essence of Wassily Kandinsky's critique of Impressionism).
Cezanne's quest in painting was, I believe, to find a path to synthesis between the eye and the mind, between the richness of visual reality and the mind's quest for ideals, between (as it were) Rembrandt's absolute, whitest whites and Monet non-white, colourful whites. And this, I believe, is what Rilke responded to so strongly and eloquently.
* As an aside, there are languages where the basic colour vocabulary splits the whole range into just two words: one stands for black and everything dark & cool; the other, for white and everything warm & light. This doesn't mean that the speakers don't distinguish more colours, but other terms are "secondary", non-essential (like, say, "mauve" or "olive" in English). Go back to text