A brood comb

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Archive for November 6th, 2007

True Blue

Posted by Tanas Gjorgoski on November 6, 2007

Tye in his paper The puzzle of true blue presents to us the following puzzle:

Munsell chips of minimally different color are presented to John and Jane in standard conditions of visual observation. Both John and Jane have non-defective color vision, as measured by color tests.

Asked to pick-out a ‘pure-blue chip’, a chip that is blue, and is not tinged with any other color, John picks out Munsell chip 527. Jane, on other hand sees that chip as slightly greenish blue.

We are now presented with the following possibilities about John’s and Jane’s color experiences of the chip:

    (a) The color of the chip is both as it looks to John, and as it looks to Jane.
    (b) The color of the chip is as it looks to John, but not as it looks to Jane. (or other way around)
    (c) The color of the chip is neither as it looks to John, nor as it looks to Jane.

The puzzle is that none of those answers, on the face of it, seems plausible. Answer (a) is problematic, as it would mean that the chip is both true blue and blue tinged with green at same time. Answer (b) is problematic, as it is hard to see what would be the reason (positivist’ or metaphysical) to count John’s perception as “normal”, and not that of Jane. Answer (c) is problematic, as it would seem to require that nothing can be pure blue (or pure red, or pure green).

Attempts for solution of this puzzle range over views that nothing we see is really colored (something like Locke’s primary/secondary properties distinction), that we can in fact make sense of the idea that one of those perceivers is normal one, or view (like Tye’s) that the issue is one of precision. In that answer neither Jane nor John have been “designed” (by evolution) to get the color exactly right, but to pick out colors on course-grained level.

—–

I want here to give an alternative solution to the puzzle, by picking out the choice (a). That is, I think that the color of the chip is (or can be) both as it looks to John, and as it looks to Jane.

First, it should be noted that it is not logically problematic that both A and B can be predicated to something, as long as A and B are not in contradiction. For example, there is nothing problematic in saying that something is both oval and green. So, the problem for the choice (a), is that the predicates ‘pure blue’ and ‘slightly greenish blue’ are apparently contradictory.

The proposal would be that objects have colors, but that we are seeing just an aspect of these colors due to the limits of our perception. John and Jane then when looking at the same color chip, are seeing different aspects of the color.

To make an analogy, it would be similar to a situation where we have a point on a plane, but we are limited to one dimensional projections. Usually such point, will be characterized by its projection on the x axis, in which we say that we get the x coordinate, and its projection on the y axis – y coordinate. But x and y axes are just one possible pair that covers the whole space – we can also imagine coordinate system rotated in the relation to that original one, with x’ and y’ axes. Given that there is nothing about the plane which gives primacy to certain coordinate system, there will be no reason to prefer the first over the second pair of axes.

So, staying with the analogy, we can use the following metaphor: the objects’ colors are two-dimensional (this has nothing to do with a usual categorizing of color along dimensions of hue, saturation and brightness, actually we are talking about hue solely here), but our perceptual systems are picking out just the coordinates in relation to a single axis (which axis would represent the linear space of all hues we can pick out). However relatively to this two-dimensional color space, there are infinity of possible hue axes, and there is no reason to give primacy to one over another. Applied to John’s/Jane’s case, it would look like this:

When John and Jane are looking at the same Munsell 527 chip, they are seeing two different aspects of the chip’s full-color. John is reporting true blue, and Jane is reporting slightly greenish blue. However John has never actually seen that ‘greenish blue’ that Jane sees, nor has Jane seen this ‘true blue’ color that John sees. So, even neither of them has better color sight than the other, the situation is not a contradiction. The property of John’s ‘true blue’ not to be tinged by any other color is a truth about this specific aspect of the color which John is picking out. The property of Jane’s aspect not to be true blue, is also truth about that specific aspect that Jane is picking out with her color vision. In such way, there is nothing problematic in the same Munsell chip being both John’s true blue, and Jane’s slightly greenish blue.

Even those aspects are different, if the hue-axes are not rotated much one to another, they will mostly overlap, and if we ignore those special cases, Jane and John will agree on the colors, especially as concepts like ‘blue’ cover not just a single coordinate, but a range of values.

Note:Of course this is a simplest aspect possible (projection from space to line), but the actual aspects that we pick out might not be so simple. For example we might pick out not one, but three aspects (relating to green, blue and red), which we would be able to relate easily to the known facts about eye, cones/pigments and functioning of opponent neurons. I just wanted to present how if we see the color that we see as an aspect of the richer color, it gives us a general way to solve the ‘true blue’ puzzle, while staying on color-realism side.

UPDATE: I first heard of the issue on Wo’s weblog, where Wo gave similar proposition with the one in this post.

Posted in Colors, Perception, Philosophy | 11 Comments »