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Is it possible to imagine a color you've never seen before?--Noah L., age 10

Is it possible to imagine a color you've never seen before? --Noah L., age 10

It would not be right to raise a child in a very controlled environment where she is cut off from all that wonderful, colorful nature you get to experience every day. But we can think about such a child. So let's do this. Suppose this child is raised in such a very controlled environment where she can ever see only six basic colors: blue, white, black, red, yellow and violet. I think we would be able to explain to this child -- in fact, to any child -- that the color violet lies between red and blue, is really a mixture of red and blue. And I think we could then go farther and say that red and blue can also be mixed in different proportions, so that the mixture contains less blue and more red. In this way, I think we can get the child to imagine the color purple. So the answer to your question is yes, it is possible.

But it is possible only in those cases where the child knows colors that are close enough. You probably know from your experience in drawing that you can mix yellow, red and black to get brown. But I would be surprised if the child in our story could imagine brown with this instruction: imagine a mixture of black, red and yellow. Similarly, the color green can be produced by mixing yellow and blue, and again I think our little girl would not be able to imagine green from the instruction to imagine blue mixed with yellow. I am unsure about orange which, as you know, is a mixture of yellow and red. It would surely be harder for her to imagine than purple (where she already has another mixed color -- violet -- available to her). I am similarly unsure about turquois, which is a mixture of blue and green. Perhaps she would be able to imagine orange and turquois.

So the full answer is that which of the colors someone has never seen before she is able to imagine depends on the colors she has seen. New colors can be imagined if they are variations on, or combinations of, colors that one has seen before.

It would not be right to raise a child in a very controlled environment where she is cut off from all that wonderful, colorful nature you get to experience every day. But we can think about such a child. So let's do this. Suppose this child is raised in such a very controlled environment where she can ever see only six basic colors: blue, white, black, red, yellow and violet. I think we would be able to explain to this child -- in fact, to any child -- that the color violet lies between red and blue, is really a mixture of red and blue. And I think we could then go farther and say that red and blue can also be mixed in different proportions, so that the mixture contains less blue and more red. In this way, I think we can get the child to imagine the color purple. So the answer to your question is yes, it is possible. But it is possible only in those cases where the child knows colors that are close enough. You probably know from your experience in drawing that you can mix yellow, red and black to...

Is there an infinite number of colors?

Is there an infinite number of colors? It occurs to me that, given our neurophysiology, there is only a finite number of colors that any human can actually see (the same could surely be said for any animal whatsoever). In order to claim that there is an infinite number of colors, then, I think that you would have to be able to talk about colors which are only "in principle" perceptible--but it seems weird to talk about colors which no perceiver can actually perceive.

If you are talking about basic colors, then you are right: there are only finitely many of them, and to get beyond them one would then have to bring in "colors" beyond the visible spectrum, and this is indeed weird in the absence of beings that can actually perceive those "colors".

But here's an argument on the other side. Suppose we are willing to count as colors all the different shades on the visible spectrum -- between 360 and 750 nanometers, let's say. Suppose these are densely packed so that between any two wave lengths there's always another one. Then we'd have infinitely many different colors all of which we can actually perceive. (There's a serious questions about whether this account is consistent with the latest physics, but set this aside for a moment.)

Now you might object that two colors can be different only if (a) we are able to perceive both and (b) we are able to discern the difference between them. Our abilities of discernment are surely limited, and so there are not infinitely many distinct colors after all.

But there's a response to this objection. Suppose our discernment powers are limited so that we cannot distinguish colors when the wave lengths of the light hitting our retinas are less than 1 nanometer apart. (Take any other plausible number if you like, it does not matter.) Would it follow that we can only distinguish about 390 colors? No, because we are able to distinguish shades of color indirectly. For example, we may be able to distinguish light of wave length 444.44 from light of wave length 444.39 by the fact that we can directly distinguish the former but not the latter from light of wavelength 443.41. In principle, this method of indirect distinction might be carried on indefinitely (e.g. we may be able to distinguish light of wave length 444.4444444444440 from light of wave length 444.4444444444430 by the fact that we can directly distinguish the former but not the latter from light of wavelength 443.4444444444435). To be sure, you won't actually get very far with this in your life time. But this does not refute the hypothesis that there are infinitely many distinct and distinguishable shades of color.

If you are talking about basic colors, then you are right: there are only finitely many of them, and to get beyond them one would then have to bring in "colors" beyond the visible spectrum, and this is indeed weird in the absence of beings that can actually perceive those "colors". But here's an argument on the other side. Suppose we are willing to count as colors all the different shades on the visible spectrum -- between 360 and 750 nanometers, let's say. Suppose these are densely packed so that between any two wave lengths there's always another one. Then we'd have infinitely many different colors all of which we can actually perceive. (There's a serious questions about whether this account is consistent with the latest physics, but set this aside for a moment.) Now you might object that two colors can be different only if (a) we are able to perceive both and (b) we are able to discern the difference between them . Our abilities of discernment are surely limited, and so there are not...

It is legitimate to say that tomatoes instantiate the property red.

It is legitimate to say that tomatoes instantiate the property red. But is it also legitimate to say that tomatoes "cause" the instantiation of the property red? Thank you.

One might say that a person causes the property kind to be instantiated when she decides to perform a kind act: She causes there to be a kind act.

But we cannot really say anything like this about static objects. The stone does not cause heaviness to be instantiated, the relationship between stone and heaviness is too close for this. Something heavy comes into existence together with the stone. The stone does not cause its own existence, so it does not cause the instantiation of the property heavy.

Now a tomato is unlike a stone in that it changes (its color turns from green to red) and also unlike a person in that it does not make decisions about how to be. The latter discrepancy seems to me less significant when we are speaking about causality. Considering a tomato plant we can, I believe, say both that it causally produces fruits that eventually mature to the point where they are red (thus causes the property red to be instantiated) and also that it instantiates this property (when parts of it are ripe fruits). I feel less confident about saying this about a tomato that matures on your window sill. It instantiated green yesterday. It instantiates red today. But we would be inclined to say that processes in the tomato, not the tomato itself, (together with external factors such as warmth) caused the change in color. This inclination, however, may be a mere convention: Changes in persons and tomatoes can be caused by processes within them. And there seems to be no deeper reason why we should be prepared to say in the first case, but not in the second, that the change in X was caused by X.

One might say that a person causes the property kind to be instantiated when she decides to perform a kind act: She causes there to be a kind act. But we cannot really say anything like this about static objects. The stone does not cause heaviness to be instantiated, the relationship between stone and heaviness is too close for this. Something heavy comes into existence together with the stone. The stone does not cause its own existence, so it does not cause the instantiation of the property heavy. Now a tomato is unlike a stone in that it changes (its color turns from green to red) and also unlike a person in that it does not make decisions about how to be. The latter discrepancy seems to me less significant when we are speaking about causality. Considering a tomato plant we can, I believe, say both that it causally produces fruits that eventually mature to the point where they are red (thus causes the property red to be instantiated) and also that it instantiates this property ...