Topics Color

Question 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.

Accepted:
October 14, 2010

Comments

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.