Color, Relativism, and Realism

Color, Relativism, and RealismAuthor(s): John SpackmanSource: Philosophical Studies: An International Journal for Philosophy in the AnalyticTradition, Vol. 108, No. 3 (Apr., 2002), pp. 249-287Published by: SpringerStable URL: http://www.jstor.org/stable/4321255 .

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JOHN SPACKMAN

COLOR, RELATIVISM, AND REALISM

(Received 29 June 2001)

ABSTRACT. It is plausible to think that some animals perceive the world as colored differently from the way humans perceive it. I argue that the best way of accommodating this fact is to adopt perceiver-relativism, the view that color predicates express relations between objects and types of perceivers. Perceiver- relativism makes no claim as to the identity of color properties; it is compatible with both physicalism and dispositionalism. I argue however for a response- dependence version of it according to which an object counts as red (for a type of perceiver) iff it standardly looks red to normal perceivers (of that type). Finally, I develop a notion of minimal realism on which this account counts as realist despite its subjectivist elements, in that it is committed to the objectivity of truth.

Contemporary philosophical accounts of color are, by and large, anthropocentric.1 It is clear, given the findings of color science, that there are actual beings with systems of color discrimination quite different from our own, and clearly there are countless imaginable beings with different visual systems as well. But for the most part, recent accounts of color have not even considered whether this fact is relevant to an understanding of the nature of color. My aim here is to explore what I take to be one implication of this variation in color perception, namely a certain form of relativism concerning color. If one accepts that any given object might look one color to an organism with one type of perceptual system and a different color to another, the most sensible solution will be to view color predicates as relative to types of perceivers.2 Perceiver-relativism, in the sense I will argue for here, is the claim that color predicates such as 'is red', for instance, are properly viewed as relational predicates of the form 'is red for Ti', where Ti ranges over types of perceivers.3

I also want to address two further issues connected to perceiver- relativism. First, I will take at least one step toward giving an account of the relation expressed by color predicates by arguing for what I will call, following Mark Johnston, a response-dependence

Li Philosophical Studies 108: 249-287, 2002. ? 2002 Kluwer Academic Publishers. Printed in the Netherlands.



250 JOHN SPACKMAN

account of this relation. Such an account is one which accepts that there is a close logical connection between being red and evoking a particular response in perceivers: an object counts as red for Ti just in case it standardly looks red to specified members of Ti. Secondly, I will argue that although the account I am proposing might in some respects be called a subjectivist one, it can nonetheless legitimately claim to be a realist view of color. While on certain traditional views of realism it may seem that any account which accepts relativism and response-dependence will be forced into the eliminativist conclusion that colors are not properties of objects at all, in the final section I will sketch a minimal form of realism which, I will argue, is compatible with the view of color offered here.

Before defending these claims, I want to say a bit more about them. I will have more to say later about what the different types of perceiver involved in color relativism might be. Perhaps the most natural route is to equate them with different species, and to say that within each species there is a different standard of a "normal" perceiver. But it is not essential to my view how these types are determined. What is essential is that there be a multiplicity of actual or possible types of perceiver, and that color predicates be relative to these.

A response-dependence account of color, as I will use the notion here, is one which accepts as true a priori "color biconditionals" broadly of the form "x is red if and only if x would look red to S", where S is some perceiver or group of perceivers under some description.4 I will argue, in particular, that any account of the relation expressed by color predicates must accept a relativized version of response-dependence which adopts biconditionals of the form:

(B 1) x is red for Ti if and only if x would look red to normal perceivers of type Ti under standard conditions for Ti.5

In defending (B 1) I will be defending what might be called a nonrigidified version of response-dependence, in contrast with accounts which would adopt a form of the color biconditional rigidified on actual perceivers and conditions (e.g., "x is red if and only if x would look red to normal perceivers as they actually are under standard conditions as they actually are", or a relativized equivalent).

It will not be part of my purpose here to defend any particular theory concerning the identity of color properties; my aim



COLOR, RELATIVISM, AND REALISM 251

is rather to propose certain constraints - relativism and response- dependence - which any such theory must accept. In particular I will not try to decide the debate between physicalism, the view that colors are to be identified with one or another type of physical property, and dispositional theories, which identify colors with the dispositions of objects to present a certain color appearance to the perceiver.6 I take both relativism concerning color predicates and response-dependence concerning the colors to be compatible with physicalist as well as with dispositional theories of the identity of color properties.7 However, in arguing for a non-rigidified form of response-dependence, I will take issue with physicalist accounts which adopt a rigidified reading of descriptions of the causal relations underlying color perception, including the widely held view that such descriptions serve to fix the reference of color terms rather than contributing to their meaning.

Though I cannot pursue the matter here, I want at least to note the potential broader relevance of the claim that color relativism is compatible with a form of realism. What are effectively response- dependence accounts of secondary qualities have in recent years provided the basis for realist arguments concerning many other types of properties which seem subjective in a similar sort of way, among them notably moral and aesthetic properties.8 But it has sometimes been contended that there is an important disanalogy between secondary qualities and moral and aesthetic properties which would stand in the way of the extension of realism into those other domains, namely that moral and aesthetic judgments are deeply subject to disagreement in a way secondary quality judgments are held not to be.9 The account I will offer here suggests one direction a realist response to this objection might take. If relativism is compatible with a minimal realism in the domain of color, perhaps even if one concedes some form of relativism in ethics and aesthetics, this need not stand in the way of an analogous kind of realism in those areas.

1. COLOR RELATIVISM

In order to consider the case for color relativism, it will be helpful at the outset to review a few basic facts about the human visual



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system. The primary biological foundation for normal human color perception lies in the three types of cones in the human retina, each sensitive to a different range of wavelengths of light due to the presence of three types of photoreceptors. In that it is mediated by these three photoreceptor types, normal human color perception is said to be trichromatic. This fact explains in part why normal perceivers can match the appearance of any chromatic stimulus by mixing together in various proportions monochromatic light of only three types.'10 According to the widely accepted opponent theory of color vision, normal human perception of color is the product of the contribution of the cones' outputs to three color channels, an achromatic (black and white) channel, a red-green channel, and a yellow-blue channel.11 Some (unusual) humans are dichromats, in that they have two types of photoreceptors, and so can match any chromatic stimulus using only two monochromatic lights. Others are monochromats, lacking color vision other than shades of black and white altogether.

It is easily imaginable, however, that there might be organisms that had a different perception apparatus and hence perceived the world in terms of a different set of colors. It is certainly at least possible, for instance, that there might be organisms with more than three types of retinal cones, who might hence perceive the world in terms of a set of chromatic color oppositions richer than the red- green and blue-yellow channels we have developed. In fact, though, there is mounting evidence that at least some non-human animals actually have perceptual systems quite different from the human system, and so see the world as differently colored. Comparative studies of the physiology and the capacity for color discrimination behavior among various non-human animals and insects suggest that there is considerable variety in how different types of perceivers see the world as colored. Because of the difficulty of measuring color perception in non-human creatures, different studies of the same species have often yielded conflicting evidence, but some consensus has been achieved concerning at least some species.

While many species seem to be trichromatic in a way roughly similar to human beings - the great apes, for instance - trichromacy cannot be considered the norm. Many species have a more limited capacity for color perception. Both physiological and behavioral




studies agree that the various species of ground squirrels, to take one example, are probably dichromats.12 Like those abnormal humans who are dichromats, they have a spectral "neutral point" (in their case, around 505 nm) at which they cannot distinguish light of that wavelength from achromatic light. Physiological studies confirm this hypothesis by revealing only two types of photopigments in the retina, rather than the three found in normal humans. Some other species, such as cats and rats, have many fewer retinal cones than do human beings, and seem to have only a quite weak capacity for color discrimination, although it remains unclear whether the color vision they do have is trichromatic or dichromatic. It appears, however, that many other species have a broader capacity for color perception than do normal humans. Some species - for instance the honeybee, and many diurnal birds - are capable of discriminating ultraviolet or near ultraviolet wavelengths invisible to human beings. Studies have shown, for instance, that bees can discriminate between two flowers which look white to the human eye but which reflect ultraviolet wavelengths differently.13 And there is substantial evidence that a number of other species, including goldfish, pigeons, ducks, and hummingbirds are in fact tetrachromatic. 14

It seems natural to interpret the behavioral and physiological evidence concerning animal and insect visual systems as showing that at least some non-human animals see at least some objects as having different colors from the colors humans perceive them as having. There are several important caveats to be observed here. Firstly, given the evidence that some animals group spectral stimuli into hue categories in a quite different way from the way normal humans do, it should not be assumed that we can map the perceptual experience of other animals using our hue terms. 15 But it would not affect my argument even if we accepted that animals cannot perceive any of the same colors human beings do.16 All my case requires is that some animals perceive some colors or other. On my view this amounts to the requirement that we have reason to believe the qual- itative character of some animals' perception to be similar enough to ours that we would call it color perception. Second, David Hilbert has doubted whether, as is often assumed, the capacity to distinguish between lights of different wavelength independently of the relative intensity of those lights is a sufficient condition for having color



254 JOHN SPACKMAN

vision.17 An organism might, for instance, have two independent systems of receptors which lead it to respond differentially to lights of two different wavelengths without the outputs of those systems ever being combined. But since it is plausible, Hilbert suggests, that in order to perceive color an organism must be able to discriminate not only differences between stimuli but also some facts about the nature of those differences, it is reasonable to make it a condition of color vision that the outputs of the different relevant receptors must interact. Even if we accept Hilbert's proposal, however, it seems likely that there will be some organisms whose visual systems both meet his standard of complexity and lead them to see some objects as having colors other than those humans see them as having. And certainly it is possible that there should be organisms of this kind.

A more radical objection is raised by Michael Watkins, who argues that in fact few, if any, animals perceive colors at all.18 Watkins' primary ground for such a claim seems to be that if we say that some non-human animal veridically sees a given object as one color, while humans veridically see it as another, we will violate the intuitively plausible color incompatibility thesis. This is the thesis that no (homogeneously colored) object can simultaneously be two or more different colors (e.g. turquoise and lime-green) all over.19 But Watkins' problem is easily solved by relativizing color predicates to types of perceivers. The color incompatibility thesis as stated is indeed a plausible constraint on any non-relativistic account of the colors, but a relativized account must accept only a relativized version of the thesis, that no object can be simultaneously two different colors for the same type of perceiver. Once color predicates are relativized, there is clearly no contradiction in saying that a given object may be turquoise all over (for one type of animal) and lime-green all over (for another type) at the same time. A relativized account does indeed require some revision in our prereflective conception of the colors, but the necessary recon- ceptualization doesn't seem particularly counterintuitive - certainly less counterintuitive than denying that animals perceive colors at all.

If we do admit that at least some non-human organisms may see the world as differently colored from the way humans see it, it is difficult to avoid the relativist conclusion. Let's distinguish between two different ways color predicates might be relativized. The type




of relativization I am arguing for here is perceiver-relativity. A different type of relativization might be motivated by such familiar observations as that blood looks red to normal humans in daylight, but looks yellow or variegated to normal humans under a microscope. What we might call "condition-relativity", then, would view color predicates as relative to different perceptual conditions. Now it seems clear that any account of the colors which is wholly non- relativistic, if it is to abide by the color incompatibility thesis, must assign only one color to each homogeneously colored object. A condition-relativized theory of color will be able to assign a different color to each object for each different viewing condition, but it will still have to abide by a "condition-relativized" color incompatibility thesis, and so assign at most one color to each object for each viewing condition.

As we have seen, however, we have good reason to believe that there are animals that would perceive an object which normal humans see as red in standard viewing conditions - a Red Deli- cious apple, for instance - as some color other than red in the same conditions. In order to abide by their respective color incompatibility theses, both non-relativized theories of color and condition- relativized theories will be forced to choose one of the color appearances the apple presents to different types of perceiver in these conditions as representing its true color. Let's take as an example a non-relativized physicalist theory. Contemporary physicalist theories fall largely into two categories, which identify colors with types of either microphysical surface properties (MSP's) or surface spectral reflectances (SSR's) of objects, and SSR of an object being the proportion of incident light, for each wavelength of the spectrum, which it will reflect.20 Suppose then a non-relativized reflectance theory is considering a Red Delicious apple with a particular SSR (say SSR1) which is seen as red by normal humans in standard human conditions but as orange in those conditions by normal perceivers of another type. If it is to avoid violating the color incompatibility thesis, this theory will not be able to identify SSR1 as an instance of both red and orange; SSR1 will have to be an instance of only one color.21 Typically of course it will be assumed that it is an instance of red. But surely this is a quite arbitrary practice. The only way to identify it as an instance of



256 JOHN SPACKMAN

red and not of orange would be to held that the organisms that perceive it as orange are subject to a color illusion while humans are not. But what grounds are there for viewing all non-human organisms that perceive objects as having colors other than those humans perceive in them as subject to widespread color illusions? It might be suggested that we should assign colors to objects on the basis of how the objects are perceived by those organisms which can make the largest number of color discriminations, and that humans are those organisms. But in fact humans don't seem to be the best color discriminators. At any rate, it is surely implausible to convict all beings other than the best color discriminator of widespread color illusions. For the color vision of every type of organism, equally, is the product of adaptive mechanisms which allow it to success- fully interact with its environment. Rather than adopt some ad hoc conception in order to solve the problem of arbitrariness, then, the natural solution is to view color predicates as relative to types of perceivers. We can then accept that 'x is red for T1' may be true of any given object while 'x is red for T2' is simultaneously false of that object.

There are several ways in which one who accepts that different organisms see the world as differently colored might nonetheless try to avoid this relativist conclusion, but of the three most obvious such strategies, one is unsuccessful, and the others seem to me misguided. One might, firstly, argue that even if we concede, given the variation in color perception, that there is no non-arbitrary way of uniquely assigning colors to objects, there is still a way of holding that there is a single, non-relativized predicate 'is red'. Such a strategy might be suggested by the observation that on the perceiver- relativist view, the various properties of redness associated with 'is red for T1', 'is red for T2', and so on, all have something in common: that objects which have them look red to the perceivers in question. Should we not then say that there is in fact a single property of redness, namely that property which objects appear to have when they look red to perceivers of any type? This property might be identified in several ways, depending on one's favored account of 'looks red'.22 If one takes 'x looks red' to mean "x gives the visual appearance of being red", one might say that the property of redness, for all species, is that property which objects appear to




have when they present a certain visual appearance, namely that visual appearance which red things typically present, to any type of perceiver. Alternatively, if one takes 'x looks red' to mean "x causes red' sensations", one might say that the property of redness is that property of objects by virtue of which they cause red' sensations in any type of perceiver. The problem with either of these accounts is that once again, because they are non-relativistic, they run afoul of the color incompatibility thesis. Since these views decline to convict all non-human organisms of color illusions, according to them an object will count as red (tout court) as long as there is some type of perceiver to whom it normally looks red. A Red Delicious apple will, since it normally looks red to some type of perceiver, count as (non-relativistically) red; at the same time it will, if it regularly looks orange to another type of perceiver, be (non-relativistically) orange. This violation of the color incompatibility thesis is clearly unacceptable.

Another way one might seek to avoid perceiver-relativism, given the problem presented by color perception in non-human animals, is suggested by a recent article by Peter Ross.23 Ross identifies colors with disjunctive physical properties, and holds that the various elements of the causal relations underlying color perception are not aspects of the identify or constitutive nature of color properties, but rather aspects of varying perceptual access to the physical color properties themselves. While he does not discuss the variation in color experience in non-human animals, an account of this kind could naturally be extended to cover the causal relations underlying these variations as well. If such an account is to avoid relativizing color predicates, it must depend, as Ross' view does, on the notion that descriptions of the relevant causal relations do not give (in part) the meanings of color terms, but only fix their reference. I will argue in the following section, however, that there are strong reasons for rejecting this type of reference-fixing view.

A third strategy for avoiding perceiver-relativism in the face of cross-species variation in color perception would of course be to deny that colors are properties of objects at all. I will try to dispel the temptation to adopt such an eliminativist view in the final section.

It should be emphasized that the relativized view of color predicates I have proposed is not incompatible with physicalist accounts



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of the identity of color properties; the objection discussed above counted only against non-relativized physicalist theories. While perceiver-relativism has usually been associated with dispositional views of color, it should be clear that it could also be accommodated by either of the main contemporary types of physicalism. Even if it is right to view color predicates as relations between objects and types of perceivers, this does not rule out the possibility that these relations could in each case be realized by non-relational physical properties. Redness for humans, for instance, might be identified with a certain disjunction of types of MSP's or SSR's, while redness for another organism might be identified with a different disjunction of such properties. The MSP account of color offered recently by Frank Jackson and Robert Pargetter is one example of how such a relativized physicalism might look.24

If this is so, however - if viewing color predicates as relational does not preclude our viewing the colors as in a certain sense types of non-relational properties - one might wonder what the real important of perceiver-relativism is. If perceiver-relativism is true, what it shows is that even if the colors are ultimately to be identified with physical properties, there is nonetheless a level of discourse at which we must speak of them as relations to types of perceivers. If the physicalist is right, the physical properties associated with the human perception of red and green are to be identified not with red and green per se, but with red-for-humans and green-for- humans. Whereas traditional non-relativized forms of physicalism must identify each token MSP or SSR as an instance of at most one color, a relativized physicalism will have to allow that a token MSP or SSR could count as an instance of both red-for-humans and orange-for-another-type-of-perceiver.

2. RELATIVISM AND RESPONSE-DEPENDENCE

Perceiver-relativism pictures color predicates as relations between objects and types of perceivers. What is the nature of the relation they express? While I cannot here do justice to all of the issues concerning this relation, I do want to take one step toward clarifying it, by arguing that any correct account of the relation must at any rate be a response-dependence account, and in particular, must accept




color biconditionals of the form (B 1) noted above. Though this does not give us a full account of the nature of the relation expressed by 'is red for Ti', it does tell us at least that the occurrence of this relation in objects must necessarily coincide with those objects' standardly looking red to normal perceivers of type Ti.25

The central consideration in favor of the response-dependence view of color predicates I am proposing is that any account which rejects (B 1) will inevitably violate an important and plausible thesis concerning color which is arguably essential to our color concepts. This is the thesis that the colors are, to borrow a term from Mark Johnston, perceptually available in a way that differentiates them from properties traditionally viewed as primary qualities, such as being square or being platinum.26 The notion of perceptual availability I will employ here is slightly different from Johnston's. Johnston himself seeks to explicate perceptual availability in terms of the epistemic justification of beliefs about the colors of things. On his view, perceptual availability is the thesis that justified belief about the color of an object is available to any perceiver on the basis of perception of the object alone, or, more properly, on the basis of perception together with certain background beliefs which standardly inform perception, most importantly that the perceiver take herself to be a normal perceiver and perceptual conditions to be standard. The notion of perceptual availability I will use here is a slightly stronger one: to say that a property is perceptually available is to say that relevant perceivers can know that an object possesses it on the basis of perception alone (along with the relevant background beliefs). Note that what is claimed by the thesis that a property is perceptually available in this sense is not that knowledge of its identity or constituting nature is available on the basis of perception alone (plus the background beliefs), but only that knowledge that an object has that property is so available.27 What I want to argue in order to make my case for response-dependence is that the colors are, in contrast to primary qualities, perceptually available in this sense. For the sake of simplicity, let's set aside the relativity of color predicates for a bit until we have clarified the notion of perceptual availability.

Why should we think that the colors are perceptually available in this sense, while squareness for instance is not? Clearly there are at



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least primafacie objections to saying that the colors are perceptually available in my sense to all perceivers in all circumstances. It is true that the roles played by perceptual appearances and non-perceptual facts in our knowledge of these two kinds of properties do seem to differ in some way: while we often check physical measurements in order to verify perceptually-based claims about the squareness of surfaces, we only rarely (never, in the experience of most people) have recourse to physical facts about objects or perceivers before accepting perceptually-based claims about the colors of things. But certainly we cannot conclude from this that it is possible for reference to physical facts beyond those available to perception to overrule, falsify, perceptually-based claims about the squareness of things, while such facts can never overrule perceptually-based claims about the colors. Clearly it is also possible for physical facts about an object to show a perceptually-based judgement of its color to be wrong. On one commonsense conception of color, this will be possible in any case in which the perceiver deviates enough from normal color perception or perceptual conditions are non-standard.

If there are difficulties for the view that colors are perceptually available to all perceivers in all circumstances, however, perhaps it is possible to make a case for a more limited claim. One might concede that colors are not perceptually available to perceivers other than normal perceivers in standard conditions, but argue that they are still unlike primary qualities like squareness in being perceptually available at least to perceivers who do fit those norms. That is, one might argue that where a perceiver believes that an object is scarlet red solely on the basis of perception (along with the relevant background beliefs), it is true to say that this belief cannot be shown false by physical facts beyond those available to perception just in case the perceiver is normal and his perception occurred in standard conditions; whereas the same cannot be said of a perceptually-based belief that a surface is square. There is indeed a line of argument which might be thought to support such an account. According to this line of thought, while the squareness of surfaces is correlated with physical facts about those surfaces directly, physical facts about objects are correlated with those objects being scarlet red only indirectly, by reference to the color perception of some perceiver or perceivers under some circumstances. Which perceivers




and which circumstances? Different views might of course be taken on this question. But at any rate, on this view the color perception by reference to which physical facts are correlated with colors must be the perception of some perceiver taken to be normal, in some conditions taken to be standard. Since any object presents a welter of different color appearances to different perceivers in different perceptual conditions, any account which assigns colors to objects at all will have to do so on the basis of some specification of norms for both perceivers and perceptual conditions. This specification need not be the traditional one, according to which the normal perceiver represents a norm for an entire species and standard conditions are assumed to be by and large conditions of daylight. One might instead prefer some more relativized conception of either of these norms. One could, for instance, adopt a norm for perceptual conditions which would result in what I called above condition-relativism, so that each object has a different color for each condition in which it regularly presents a certain color appearance to the relevant perceivers. So too the norm for perceivers could be further relativized, beyond the species-based relativism I have spoken of here, to either subgroups within a species (human trichromats and dichromats, perhaps) or even to individuals.

But whether one adopts the traditional reading of these perceptual norms or some further relativization of them, according to the argument at hand reference to some such norms is, unlike in the case of squareness, the only possible basis for correlating physical facts with colors at all. And so, on this view, if a perceiver deemed normal forms the belief that an object is scarlet red solely on the basis of its looking scarlet red to her in conditions deemed standard, measurement of physical facts about the object or the perceiver could never contradict that judgement. The physical facts could only confirm the perceiver's belief. The colors will thus be perceptually available to normal perceivers in normal conditions (in the chosen sense), and only to such perceivers in such conditions. But - so the argument would go - the situation is quite different when it comes to our knowledge of the squareness of things. If a perceiver deemed normal formed the belief that a surface is square solely on the basis of perception of the surface in what are termed standard conditions for the perception of squareness, it would still



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be possible for measurement to show that belief to be false, for the surface might turn out to be only roughly square. On the present account the reason for this is that physical facts about surfaces give us a way of determining squareness which is quite independent of how square things look to any perceiver in any condition. Unlike colors, on this view, squareness is not perceptually available even to normal perceivers in standard conditions.

Now this story about the difference between our knowledge of colors and our knowledge of squareness is committed to a certain conception of the standards required for knowledge, a conception which has itself been widely questioned. In particular, it presupposes some version of what is sometimes called an invariantist account of knowledge, as opposed to a contextualist account. Contextu- alism, for present purposes, is the view that the truth-conditions for knowledge-attributing sentences with forms like "S knows that p" may vary, in terms of the epistemic standards S must meet in order to count as knowing, with the context of the utterance (that is, the context of the knowledge attribution); invariantism is the view that there is a single set of epistemic standards governing all such attributions of knowledge.28 The argument just reviewed differentiates colors and squareness by associating with them two quite different invariant standards of knowledge, centrally involving normal perception in standard conditions in the one case, and measurement of lengths and angles in the other. The contextualist would question the universality of such standards, and this might lead him to question as well whether the colors and squareness are really so different as regards their perceptual availability.

The contextualist's strategy, in general, is to argue that in actual practice our standards for the attribution of knowledge are often considerably lower than the invariantist makes out. He will grant that we do sometimes appeal to the higher standards emphasized by the invariantist for knowledge of the colors and the squareness of things. But he will suggest that in most everyday contexts, we in fact treat perception by itself (with the relevant background beliefs) as a sufficient basis for attributing both kinds of knowledge. There are many cases in which we would at least say people know the colors of things perceptually without explicitly requiring that they be normal perceivers in standard conditions in any sense of those




terms. We standardly assume, barring any serious disagreements in color judgements, that perceivers know the colors of the objects around them. Similarly, we often treat perceivers as knowing that a surface is square even if they do not know its exact measurements and angles. If a friend casually picked out his new picture from among some round pictures by calling it "the square one", it would be bizarre to query his description even if the picture didn't look exactly square. The contextualist urges that we have no reason not to take such practices at face value. A contextualist might thus argue that in fact we should regard the colors and squareness as being at least roughly on a par in terms of their perceptual availability: in most everyday circumstances, both are perceptually available to any perceiver who takes himself to be a normal perceiver operating in standard conditions.

Fortunately, for the present purpose of supporting the response- dependence of the colors, we need not decide between contextualism and invariantism concerning knowledge of the kinds in question. For there is in fact a way of formulating the claim that the colors are perceptually available which both approaches could accept, while also denying that squareness is perceptually available in the corresponding sense. Notice that even the contextualist will have to accept something like the invariantist's point in a limited way. Even if the contextualist insists that there are some contexts - those govemed by lower epistemic standards - in which the colors and squareness are roughly on a par as regards their perceptual availability, he will not be able to maintain that this is so in contexts with higher epistemic standards. The invariantist argument sketched above seems at least to suggest that the higher standards relevant to the two kinds of property are quite different. What kinds of higher standards for knowledge of the colors of things are relevant in cases in which we do impose them, as for instance when I reject a friend's advice about the color coordination of my clothes after discovering that he is red-green color blind or that he saw my clothes in strange lighting conditions? As the invariantist suggests, what the higher standards imposed in such cases require is that we assign colors to objects on the basis of the some specification of norms for color perception. And indeed, these perceptual norms, however they are chosen, appear to be the only higher epistemic standards relevant



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to this type of knowledge. The higher standards we at least sometimes impose for knowledge that a surface is square require that the surface have the right physical dimensions and angles, but there is no corresponding physical property independent of color appearances which plays a role in higher standards for knowledge of the colors of things. The contextualist will thus have to acknowledge that at least in these higher-standard contexts, there is a contrast between the colors and squareness: the colors will be perceptually available to normal perceives in standard conditions (in the specified sense), while this will not be true of squareness.

This partial convergence between the invariantist and the contextualist positions in fact suggests a way of formulating the claim concerning perceptual availability which both theories could accept as true of the colors but not of squareness. In expressing this claim, and in the subsequent discussion of response-dependence, I will adopt the traditional notions of the normal perceiver and standard conditions, rather some further relativization of the norms for color perception. This interpretation is not however essential to my argument.29 The claim in question is neither the thesis that the colors are perceptually available to all perceivers who take themselves to be normal and conditions to be standard, nor the invariantist thesis that the colors are perceptually available only to actually normal perceivers in actually standard conditions, but simply the claim that they are perceptually available to actually normal perceivers in actually standard conditions. About whether the colors are perceptually available to non-normal perceivers in non-standard conditions, the claim remains non-committal. Using scarlet red as an example, this claim, which we might call normal perceptually availability, might be expressed a bit more carefully as follows:

(NPA) Where S is a normal perceiver who believes that an object O is scarlet red, and S's belief is based only on perception of 0 in standard conditions for the perception of color together with S's background beliefs that she is a normal perceiver and that she perceived 0 in standard conditions, knowledge-attributing sentences like "S knows that 0 is scarlet red" are true in all contexts of knowledge attribution.




Whether one is an invariantist or a contextualist regarding the standards for knowledge, it should be acceptable that NPA is true of the colors, while the corresponding claim about primary qualities like squareness is false. Since the invariantist holds that the colors are perceptually available only to normal perceivers in standard conditions while squareness is never perceptually available, he will clearly accept that the colors are perceptually available to normal perceivers in standard conditions, while squareness is not. And as we have seen, the contextualist will have to accept that in higher- standard contexts the colors are perceptually available to normal perceivers in standard conditions, while squareness is not. Since he also holds that in contexts with lower standards both kinds of property are perceptually available to all perceivers with the right background beliefs, he will have to accept that colors are perceptually available to normal perceivers in standard conditions in all epistemic contexts, while this cannot be said of squareness.

I have up until now ignored the relativity of color predicates, but we can easily formulate a relativized version of normal perceptual availability (RNPA). The upshot of RNPA would be that, like the other colors, scarlet-red-for-Ti is normally perceptually available for Ti in that a normal perceiver of type Ti can know that any given object 0 is scarlet red for Ti solely on the basis of perception of 0 in standard conditions together with the relevant background beliefs.30 I take this extensions of NPA to cover all types of color perceivers to be a plausible one, because I take normal perceptual availability in its relativized form to be essential to our concepts of the colors. To my mind, it is hard to see why any property that was not normally perceptually available to the relevant perceivers should count as a color in our usual sense of the term. Such a property would be such that normal perceivers of the relevant type in standard conditions could not tell just by looking whether a given object had it or not, and in this sense it would be quite unlike scarlet redness (for humans), turquoise (for humans), and all the other colors. In being essential to our notion of color in this way RNPA is, I think, unusual among the intuitive theses about color which play a central role in defining that notion.31 It would be possible for an account to revise or reject many of these theses - for instance, the notion that the colors are causally responsible for color perception - and still



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be an account of the colors. But once we give up normal perceptual availability or something like it, we seem to lose our grip on the property in question being a color at all. I take RNPA, then, to express a necessary truth. The thesis should hold for any perceiver of color of any type at all, assuming that what they perceive are colors in our ordinary sense of the term.

Let's return to the broader goal of this section. If it is indeed necessary that the colors are normally perceptually available, in the relativized sense, how does this fact support the claim that they are also response-dependent? We should not be overhasty in drawing conclusions from RNPA. Several recent articles have rightly emphasized that perceptual availability by itself (in any of its formulations) does not constitute an obstacle to physicalism concerning color.32 But we can nonetheless find in RNPA support for a more limited restriction on theories of color, namely the relativized version of response-dependence captured by (B 1). This type of response-dependence, it will be recalled, accepts as true a priori biconditionals of the form:

(B 1) x is red for Ti if and only if x would look red to normal perceivers of type Ti (NP-Ti) under standard conditions for type Ti (SC-Ti).

The problem for views that reject this type of response-dependence is that if we deny either side of this biconditional, it would follow that some possible colors are not normally perceptually available. If, first, we deny "if x would look red to NP-Ti under SC-Ti, then x is red for Ti", then there will be possible objects which would look red to NP-Ti under SC-Ti but are not red for Ti. Suppose, for instance, that in particular red delicious apples standardly look red to normal members of a particular type of perceiver TI, but are not red for T1. If that it is the case, though, the colors of the apples for T1 will not be normally perceptually available to members of T1. For the fact that the apples standardly look red to normal perceivers of T1 (together with the relevant background beliefs) will not by itself be a sufficient basis for those perceivers to know the color of the apples for T1, since the apples are not in fact red for T1.

The same result follows if we reject the other side of the biconditional. If we deny "if x is red for Ti, then x would look red to NP-Ti under SC-Ti", then there will be possible objects which are




red for Ti, but which would not look red to NP-Ti under SC-Ti. Suppose, for instance, that in particular red delicious apples are red for some group T1, but standardly look orange to NP-T1. Again, if this were so, the colors of these apples for T1, would not be normally perceptually available to members of T1. The fact that the apples standardly look orange to normal perceivers of T1 (together with the relevant background beliefs) will not by itself be sufficient for them to know the apples' real color for T1, since the apples are not orange for T1. The point is that, given the structure of our everyday color concepts, we ordinarily believe that there are no facts beyond those available to normal perception in standard conditions which determine whether any given object is red. But rejecting either side of (B 1) presupposes that there must be such facts.

As noted at the outset, (B 1) expresses a form of the color biconditional which is not rigidified on actual perceivers and conditions. The reason for this is that the necessity of (relativized) normal perceptual availability gives us a strong motivation for avoiding the temptation to treat 'red' as analogous to natural kind terms by viewing redness as rigidly designated by descriptions such as "the property responsible for objects' looking red to actual normal perceivers in actual standard conditions".33 Among the accounts which adopt this rigidified view of descriptions of the causal relations underlying color perception are reference-fixing accounts, which as noted earlier treat these descriptions as fixing the reference of color terms rather than partially giving their meaning. I would thus argue that RNPA presents a serious obstacle to such accounts. The difficulty is that any account that views color predicates as rigidified on actual perceivers and conditions in this way will entail that there are some possible colors which are not normally perceptually available. This is true even of the type of rigidified account which seems most likely to avoid the problem, one which affirms response-dependence (in the guise of a rigidified color biconditional rather than (B 1)). Consider a rigidified color biconditional in its perceiver-relativized form. While I know of no attempt to adopt a rigidified form of the color biconditional within a relativized account of color, and indeed accepting relativism may undercut some of the motivation for such a view, we can certainly imagine such a biconditional:



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(B2) x is red for Ti if and only if x would look red to normal perceivers of type Ti as they actually are in standard conditions for that type as they actually are.

If we accepted this rigidified form of the biconditional, it would indeed then follow that all actual colors are normally perceptually available to the relevant actual perceptual types. But there would nonetheless still be possible colors which were not normally perceptually available to the relevant possible perceivers. Consider, for instance, a possible world in which the spectral sensitivity of the shortwave cone type in normal human beings had extended into the ultraviolet region, say down to 300 nm rather than 400 nm as is actually the case. And suppose, further, that normal human beings could then distinguish between the apparent colors in daylight of two flowers both of which actually look white to us in daylight, but which reflect ultraviolet frequencies differently. The proponent of (B2), the rigidified version of the biconditional, would have to say that the two flowers are the same color not only for actual human beings but for the spectrum-shifted human beings as well. But if this were the case, the colors of the flowers would not be normally perceptually available for the spectrum-shifted humans. The fact that the flowers looked different in color to normal perceivers of that group in standard conditions would not (together with background beliefs) suffice for those perceivers to know that the flowers were different in color, since according to the proponent of (B2) they would not be different in color. The only way to ensure that all possible colors will be normally perceptually available to the relevant perceivers is thus to accept the nonrigidified form of the relativized color biconditional (B 1).

There have, of course, been a variety of objections to accepting any response-dependence view of the colors, rigidified or not. One of the most theoretically informed of these, raised by David Hilbert in his defense of a reflectance theory of colors, concerns the ability of any response-dependence account to deal with the phenomenon of metamerism.34 Two surfaces which have different SSR's may be indistinguishable in color to normal perceivers under a certain illumination, and any such surfaces are known as metamers with respect to that illumination. It is also the case, however, that any two metameric objects will look different in color to normal observers




under some illumination. Suppose, then, that two metameric objects O1 and 02 look the same in color to just those perceivers identified by response-dependence as normal, in precisely those conditions it identifies as standard. In this case, Hilbert points out, the response- dependence theorist will have to say that in fact O1 and 02 are the same in color, and that in illuminations in which they look different in color, perceivers are subject to a color-difference illusion. The odd thing about this though, according to Hilbert, is that in the case of the "revealing" illuminations observers will perceive a real physical difference in the SSR's of the two objects by means of a visual illusion of color difference. Hilbert thus opts instead for an account which identifies colors with SSR's and so treats each distinct SSR as a distinct color, so that O1 and 02 will in fact differ in color.

Of course, as Hilbert recognizes, this very fine-grained way of individuating colors has its own counterintuitive consequences. There will, if his view is right, be many cases of differences in color which normal perceivers cannot perceive in ordinary conditions - that is, differences in color between objects which are ordinarily invisible, and only rarely if ever seen. This consequence he regards not so much as a revision as an extension of our ordinary conception of the colors, and he thus views it as preferable to the consequences of response-dependence.35 But is it really preferable? When considered in the right light, the consequences of response- dependence are not as puzzling as Hilbert makes out. After all, what is meant by Hilbert's charge that response-dependence entails that there would be real physical differences which are perceivable by means of a visual illusion? The claim is not that these differences would be perceivable by means of some malfunction of the visual system, which would indeed be puzzling. In fact, there is nothing puzzling or mysterious about the response-dependence theorist's explanation of how the physical difference between G1 and 02 iS

detected. She can allow that this physical difference is registered by a real difference in the (standardly caused) visual experiences. of the two objects in the revealing illuminations, but still insist that this visual difference does not represent a real difference in the colors of those objects. Indeed the only sense in which it might be true to say that response-dependence must view this physical difference as detectable by a visual illusion is that it is committed to a method of



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color attribution which regards the visual experiences of O1 and 02 in non-standard conditions as giving false representations of their real color. There is nothing especially odd or problematic about this view of color attribution in itself - in fact it is a commonplace feature of our everyday use of color terms. If two shirts look white in daylight, but because of their different SSR's appear different in color under blue light, we will in everyday circumstances say they are the same color, even though their different appearance in blue light registers a real physical difference. On the other hand, Hilbert's more fine-grained method of color attribution seems not merely an extension but a fairly serious misrepresentation of our everyday color concepts. To say there are many colors normal perceivers rarely if ever perceive is to revise our color concepts so far that we might begin to wonder whether we were talking about the colors in our usual sense at all, as opposed to something we already have a good name for, i.e. reflectances.36

3. A MINIMAL REALISM

For a variety of reasons, it might be hard to see how the relativized response-dependence account of color for which I have been arguing could be compatible with color realism. Perceiver- relativism makes the colors of objects dependent on the mental constitution of different organisms, and response-dependence makes them dependent in particular on how the objects in question look to different organisms. So on certain traditional conceptions of realism, which require that if any fact is to be considered real it must obtain independently of the constitutions of subjects, this view of color will have a hard time counting as realist. In this final section however I want to develop the foundations for a form of realism - what I'll call minimal realism - according to which the present account does qualify as realist. My strategy will be to support the idea that the proposed account should count as realist by responding to two possible objections to color realism, the first from relativism, the second from response-dependence.

Perhaps the most obvious source of the objection that relativism itself is an obstacle to realism is the notion that relativist views do not supply enough regularity to ground realism. The worry is that




unless it is possible to specify the real color of any given object from among the various colors it may appear to have in different viewing conditions and to different subjects, it will be pointless to view colors as properties of objects at all. C.L. Hardin, for instance, has argued for an eliminativist view of color on the grounds that any realist account must be able to specify the standard conditions in which an object is seen as having its real color, and yet there is no single correct way of doing so.37 The perceived color of an object is a function of many variables, including the spectral composition and intensity of the incident light, the orientation of the object in relation to the viewer, the color of the surround, and so on, and Hardin points out that color science does not rely on a single notion of standard conditions, but allows that there are many, depending on one's purposes. A similar point applies, on Hardin's view, for the possibility of specifying a "normal observer" among human beings. There is a significant variation in the chromatic response curves of different individual human perceivers, and Hardin argues that any specification of a normal observer from among this variety must be purely conventional.38

Despite Hardin's objections, though, variations of the kind in question could I think be adequately accommodated by a perceiver- relativized account in either of two ways. First, the traditional notions of the normal observer and standard conditions do not seem to me so arbitrary as Hardin makes out. It is arguable that these traditional notions offer the most faithful account - albeit still a fairly rough one - of the everyday practices of color attribution associated with our color concepts, and if what we are looking for in an account of the colors is an account which is faithful to these concepts, this purpose should thus provide a non-arbitrary means of specifying notions of a human normal observer and standard conditions for humans. This specification may be somewhat rough, but that roughness may simply be a characteristic of our ordinary color concepts. For instance, an object which reflects only light from the red and green areas of the spectrum will look yellow in sunlight, but black in yellow light. Nonetheless there is a clear sense in which it would be right to call it a yellow object and not a black one - namely, that sense which reflects our day to day purposes in using color terms. Very often, though not in all cases, it seems right to



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view the standard conditions implicit in our everyday application of color terms as conditions of daylight, since we commonly take an object into the daylight to see what color it "really" is. In a similar way, I take there to be at least a rough notion of a "normal (human) observer" implicit in our everyday use of color terms. It is natural to view this norm as corresponding roughly to a median chromatic response curve for human perceivers, though whether this is exactly so would be a matter for empirical inquiry.39

There are of course those who find accounts of color premised on the traditional notions of the normal perceiver and standard conditions problematic, but for them another solution to the problem posed by Hardin is equally viable, namely some further relativization of the norms for color perception of the kind mentioned earlier. If one chose to adopt condition-relativism and/or a relativization of the norm for perceivers to either subgroups within a species or individuals, one could accept Hardin's point that there is no unique way of specifying which perceptual experience captures an object's real color and still remain a realist by saying that objects have all the colors which the chosen perceptions regularly represent them as having. There are indeed arguments for such a relativized construal of perceptual norms which are not unpersuasive, and nothing in my argument for realism here depends on adopting the traditional interpretation.

Of course, what lies behind Hardin's objection is the worry that the variation in the apparent colors of objects is so wide that a relativist solution of this kind will not provide enough regularity to ground color realism. But the worry is misplaced. We cannot, of course, say that every color an object appears to have really belongs to it. It seems clearly to be a condition of color realism that perceptions of and judgments about the color of objects be capable of being wrong, and this requires a substantial amount of regularity in the colors objects are perceived to have. But this requirement of regularity does not imply that objects can have only one real color. As long as a given object is perceived to have a certain color under certain conditions by a certain observer with a good deal of regularity, it will make sense to speak of that observer's judgments as potentially wrong. And both the traditional views of the norms for color perception and more radical relativizations of those norms




would clearly still allow for enough regularity, as long as relativization was not taken too far. Even if, for instance, one held that blood is a certain shade of yellow for a particular individual when seen through a microscope from a certain angle in light of a certain spectral composition, it would still be possible for that person to wrongly see blood in those conditions as orangish on some occasion.

Let's turn to the putative problem for color realism caused by response-dependence. Can any account which views the colors of objects as dependent on how those objects look to perceivers really count as a realist account of colors? While the compatibility of realism and response-dependence has sometimes been suggested,40 I want to respond in particular to the worry that no response- dependence account could ever count as a "full-blooded" form of realism. Advocates of a "response-dependent" form of realism have pointed out that the kind of realism to which a response-dependence account of any given type of property can aspire must differ to some degree from what has often been meant by realism.41 Realism has traditionally been associated with one or another of a wide variety of notions of mind-independence. Among these a prom- inent one is what we might call the ontological characterization of mind-independence. Historically, ontological mind-independence was often expressed as the view that in order to be considered real, objects and properties must exist independently of the mind.42 A bit more perspicuously, it might be stated as the view that the facts viewed realistically should obtain independently of contingent facts about the constitution of knowing subjects. In the case of color, on this account of realism, the realist is one who holds that facts such as Red Delicious apples are red obtain independently of facts about human subjectivity. What "independently" means, for this kind of account, is of course a matter of dispute. It will be adequate for our purposes to say that on this view the realist holds that facts concerning the constitutions of human subjects should not be part of the truth-conditions of sentences expressing the facts in question. Obviously if this form of mind-independence were a condition of realism, no response-dependence account of color, including a relativized one, could count as realist. If an object is red for human beings just in case it regularly looks red to normal human perceivers, it will be a condition of red delicious apples being red for humans



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that humans have a sensibility such that the apples will look red to them.

Nonetheless, I would suggest that there is a form of realism with which response-dependence accounts are compatible, and which satisfies our intuitive requirements on what a realist account of the colors should look like. To see what this is, it will be helpful to distinguish between realism and anti-realism in the sense I have in mind, on the one hand, and objectivism, intersubjectivism, and subjectivism, on the other.43 As I will use the terms, objectivism, intersubjectivism, and subjectivism are forms of cognitivism - they accept that claims in the domain in question are capable of being literally true and false - which are differentiated by their differing accounts of the truth-conditions for those claims. A subjectivist account of claims in any domain is one which regards the truth- conditions of those claims as making essential reference to the capacities or constitutions of any individual organisms; an intersubjectivist account is one which regards these truth-conditions as making essential reference to the normal capacities or constitutions of any group of beings; and an objectivist account is one which views the truth-conditions as independent of the capacities or constitutions of any individual or group.

With these distinctions in mind, we can describe the ontological conception of mind-independence as holding that in order to be a realist about the claims in any domain, one must be an objectivist about those claims. Ontological mind-independence interprets the kind of mind-independence required for realism, that is, as objectivism in the above sense. The reason a perceiver-relativized account of colors cannot count as realist, on this view, is that it will be either intersubjectivist or subjectivist, depending on how it defines the types of perceiver to which color predicates are relative. Contrary to the claims of ontological mind-independence, however, I don't think realism concerning color requires objectivism in this sense. Realism in the sense I am suggesting here, minimal realism, is compatible with any of the views just mentioned. Not only an objectivist, but a subjectivist or an intersubjectivist as well, might be a minimal realist. Objectivism, and intersubjectivism, and subjectivism are characterizations of the content of the truth-conditions of claims. But according to minimal realism, whether the truth-conditions of a




claim refer to a subject or subjects is irrelevant to whether one can be a realist about that claim. This form of realism rejects any restric- tions on the contents of the truth-conditions of claims to be viewed realistically, and in particular does not require that such claims must have objectivist truth-conditions. Minimal realism places only two central requirements - what might be considered two alternative requirements of mind-independence - on any account if it is to count as realism concerning some claim. First, the claim must be viewed as capable of being true or false; it must be possible for the claim to be wrong. Second, the account must treat the truth predicate itself, as it applies to the claim in question, as objective, in the sense that the truth predicate is not itself relative to the different subjective constitutions of different beings. A relativized conception of truth, in this sense, would be one that left open the possibility that a given claim could be true for one type of perceiver, and false for another. It is notoriously hard to make sense of what such a conception of truth could amount to - in brief, because it seems hard to see why the conjunction of any two or more "relative truths" should not itself just amount to an overarching non-relative truth.44 The requirement enforced by minimal realism is thus in effect that the truth-conditions for any claim 's' must be broadly of the form "s is true iff p", and not of the form "s is true for members of Ti iff p", where Ti varies over types of organisms. If this requirement is satis- fied for some claim, we can be realists about that claim regardless of whether the truth-conditions for that claim refer to subjects or not.

It is not part of my aim here to consider the viability of this kind of minimal realism in domains other than that of color, but I do take it to be a form of realism open to the relativized response- dependence account of color I have proposed. This view does represent claims about color as being relative to types of perceivers, and so represents the truth-conditions of such claims as including references to types of perceivers. But it does not represent the truth or falsity of these claims as itself relative to types of perceivers. It does not, that is, represent the truth-conditions of such claims as being of the form

'x is scarlet red' is true for members of Ti if and only if x would look scarlet red to normal members of Ti in standard conditions for Ti



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but rather as being of the form

'x is scarlet red for Ti' is true if and only if x would look scarlet red to normal members of Ti in standard conditions for Ti.

A perceiver-relativized account of color predicates is thus not committed to relativism concerning truth at all; it can treat truth as a quite objective matter. On such a view, a given object may count as scarlet red for perceivers of type T1, and as not scarlet red but (say) maroon for perceivers of type T2; but that it is scarlet red for members of T1 and that it is maroon for members of T2 are objective facts which members of both T1 and T2 can readily agree on. Another way of putting the matter is that while the proposed view represents the distribution of colors in the world as dependent on different subjective constitutions, it represents the fact that objects are colored as they are for different types of beings as obtaining independently of any particular subjective constitution.45

I have so far only said what minimal realism is, and suggested that it is open to a relativized response-dependence account of color to espouse it. Why, though, should minimal realism count as realism at all? Can an account which drops the requirement of objectivism concerning truth-conditions imposed by ontological mind-independence satisfy our intuitive demands on what realism should be like? What the minimal realist suggests is that when we reflect on what should be required for realism, it is hard to find any grounds for including objectivism concerning truth-conditions among those requirements. What we can find grounds for are the minimal realist's two requirements, as noted above, neither of which entails objectivism about truth-conditions. Surely the most central requirement for realism concerning any type of claim is simply that there be some facts there for individual perceptions and judgements of that type to get right or wrong. But all that is required in order for a particular perception or judgement to be capable of getting a fact wrong is that the fact in question obtain independently of the particular perception or judgement. Such a requirement places no restriction on the content of the truth-conditions of statements of the fact in question, and in particular on whether they refer to subjects. It is quite possible, for instance, for the fact that a given apple is red (for humans) to be independent of any particular judgement about




it so that each judgement about it is capable of being wrong, while at the same time the apple's being red (for humans) depends in a general way on facts about human sensibility, in that it is part of the truth-conditions of 'that apple is red (for humans)' that humans be capable of seeing apples as red. If this is so, then what should be relevant to realism about the fact that a given object is red for humans, is not whether this fact would obtain even if humans did not regularly see that object as red, but only whether the object counts as red for humans independently of particular perceptions of it and judgements about it. And in fact, the account I have offered shows that facts about the colors do obtain independently of particular judgements and perceptions. This is shown by the fact that, even on a relativized construal of perceptual norms, there is substantial regularity in organisms' judgements and perceptions of the colors of objects. In addition to this requirement for realism, the minimal realist adds the requirement of the objectivity of the truth predicate itself: if it were the case that the rightness of a claim itself depended on the constitution of the subject that grasps it, there would be an important sense in which the fact putatively captured by that claim was not there independently of the subject. But like the first requirement, this second requirement does not prevent the truth-conditions of the claim in question from referring essentially to subjects.

One way of appreciating the merits of this conception of what realism concerning color should amount to is to consider some of the consequences of the approach offered by ontological mind- independence. It has sometimes been noted that making it a condition of realism that the facts is question obtain independently of facts about the mind precludes the possibility of realism about mental states themselves.46 But more broadly, as the case of color makes clear, imposing such a condition makes it impossible to recog- nize subjective points of view and all that pertains to them as real features of the natural world, along with objectively characterizable facts. If it is right to view color predicates as expressing relations between objects and types of perceivers, and to view these relations as response-dependent, the requirement of ontological mind- independence makes it impossible to view such relations as real features of the world. If we view it as desirable to regard subjects and their relations as just as much constituents of the natural world



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as objectively characterizable features, then, we will be hobbled by the traditional formulation of realism. And why should we not so regard them? That human subjects normally have a certain type of perceptual system, and that they see Red Delicious apples as red and the sky as blue, are just as much regular features of the world as that water is H20 and that Red Delicious apples have certain microphysical surface properties - and just as mind-independent as well, in the sense that like the fact that water is H20, these facts about human beings obtain independently of any subjective point of view.47

NOTES

1 Among the few works to consider at length the implications of the perception of non-human animals for theories of color are Evan Thompson's Colour Vision, David Hilbert's "What Is Color Vision?", and M. Watkins' "Do Animals See Colors? An Anthropocentrist's Guide to Animals, the Color Blind, and Far Away Places". Of these however only Thompson accepts a version of the conclusion I will argue for here, that color predicates should be viewed as relative to different types of perceivers. 2 For the sake of simplicity, I will restrict myself in what follows to a consideration of the colors of opaque objects, leaving aside questions concerning colored light sources and transparent and translucent objects. 3 Relational accounts of the colors have also been proposed, for a variety of reasons, by E. W. Averill, "The Relational Nature of Color", and Thompson, Colour vision. Colin McGinn also suggests the relativity of color to different types of perceivers in The Subjective View: Secondary Qualities and Indexical Thoughts, though in his more recent "Another Look at Color" he repudiates his earlier dispositional theory of color. 4 This formulation is intended to be quite broad, so as to allow the perceivers in question to be specified as individuals or as any group, with or without clauses for normal perceivers and standard conditions. I take the notion of response- dependence I am working with here to correspond fairly closely to the notion which Mark Johnston describes in "Dispositional Theories of Value", pp. 144- 146, though Johnston's version is not explicitly relativized. But I will not be arguing for the specific type of response-dependence account of color which Johnston advocates in "How to Speak of the Colors", what he calls a "response- dispositional" view. Among those who have rejected any logical tie between being red and looking red are D.M. Armstrong, "Smart and the Secondary Qualities"; A. Byrne and D.R. Hilbert, "Colors and Reflectances"; D.R. Hilbert, Color and Color Perception; and J. Broackes, "The Autonomy of Color". S Note that I will not try to decide here the complex issues surrounding the




analysis of 'looks red'. All of the claims I will make here are compatible with either of the two main competing accounts of this expression. On what might be called a representationalist account, 'x looks red' means "x gives the visual appearance of being red". (See for instance John McDowell, "Values and Secondary Qualities".) On a sensationalist account, 'x looks red' means "x causes red' sensations", where red' sensations are explicated as intrinsic, non-intentional properties of the visual field along the lines of Christopher Peacocke's view. (Peacocke, "Color Concepts and Color Experiences") Nothing I will say in what follows presupposes either of these accounts. 6 Physicalist accounts of color have been defended by, among others, J.J.C. Smart, "On Some Criticisms of a Physicalist Theory of Colors"; Armstrong, "Smart and the Secondary Qualities"; F. Jackson and R. Pargetter, "An Object- ivist's Guide to Subjectivism About Color"; and Hilbert, Color and Color Perception. Dispositional accounts have been offered by Johnston, "How to Speak of the Colors"; Peacocke, "Colour Concepts and Colour Experience"; McGinn, The Subjective View; and McDowell, "Values and Secondary Qualities". 7 Part of my aim in turning away from this debate concerning the identity of colors and focusing instead on the issue of response-dependence is to suggest that although the boundary between subjectivism and objectivism about color has traditionally been drawn by means of the distinction between dispositionalism and physicalism, it may be that the distinction between response-dependence and response-independence provides a more fruitful way of marking this boundary. (For a similar suggestion, see Alex Byrne and David Hilbert, "Introduction" to Readings on Color, Vol. 1, p. xxiii.) In recent years physicalism about color has shown itself, in its capacity to accommodate both relativism and response-dependence, to be a highly malleable doctrine. According to traditional conceptions which equate subjectivism about color with dispositionalism, and objectivism with physicalism, a physicalist theory which accepts response- dependence will still count as objectivist. But it is arguable that any theory which can satisfy the constraint of response-dependence should count as a subjectivist account in a sense that perhaps runs deeper than the traditional sense. A response- dependence physicalism will in important respects be closer to dispositionalism than to traditional versions of physicalism which reject any logical tie between being red and looking red. For like dispositionalism and unlike traditional forms of physicalism, a response-dependence physicalism will hold that how a given object looks to the relevant perceivers is a decisive criterion for determining its color. 8 See for instance, McDowell, "Values and Secondary Qualities", and "Aesthetic Value, Objectivity, and the Fabric of the World"; Philip Pettit, "Realism and Response-Dependence"; and Mark Johnston, "Dispositional Theories of Value", and "Objectivity Refigured: Pragmatism Without Verificationism". 9 Arguments against moral realism based on considerations of disagreement have, notably, been offered by John Mackie, in his Ethics: Inventing Right and Wrong, Chapter 1; and by Jonathan Lear, in "Ethics, Mathematics, and



280 JOHN SPACKMAN

Relativism". For a similar form of argument in the aesthetic sphere, see Alan Goldman, "Realism About Aesthetic Properties". 10 For an account of normal human trichromacy, as well as various abnormalities in human color perception, see G. H. Jacobs, Comparative Color Vision, pp. 23- 32. l 1 On theories of color opponency, see C.L. Hardin, Color for Philosophers, pp. 26-36, and Evan Thompson, Color Vision, pp. 56-65. 12 For a wide-ranging study of variations in color perception in different species, including the cases of ground squirrels, cats, and rats cited below, see Jacobs, Comparative Color Vision, pp. 97-158. On the variation in retinal photopigments in different species, see J.N. Lythgoe and J.C. Partridge, "Visual Pigments and the Acquisition of Visual Information". On the different forms of trichromacy present in primates, see J. D. Mollon, " 'Tho' She Kneel'd in that Place Where They Grew .. .': The Uses and Origins of Primate Color Vision". 13 For a discussion of the variation in the range of spectral sensitivity in different animals, see Thompson, Color Vision, pp. 145 ff. For a discussion of color perception in honeybees and other insects, see Georgii A. Mazokhin-Porshynakov, Insect Vision, pp. 145-192 and 255-274. 14 For a review of these studies, see Thompson, Color Vision, pp. 141-160. 15 See Thompson, Color Vision, pp. 150-151. 16 In what follows I will speak of animals perceiving "human" colors such as blue and green, but I do this only for the sake of simplicity, and do not mean to prejudice the answer to this question. 17 Hilbert, "What Is Color Vision?" 18 Watkins, "Do Animals See Colors?" 19 Watkins, op. cit., pp. 193-194. To allow for objects whose color is not uniform, the color incompatibility thesis might be stated as the thesis that no homogeneously colored object, or homogeneously colored part of an object, can simultaneously be two different colors all over. The color incompatibility thesis is of course not intended to deny that an object may simultaneously count, for instance, as turquoise and as a shade of blue. 20 One example of a microphysical property account is that given by Frank Jackson and Robert Pargetter in "An Objectivist's Guide to Subjectivism About Color". A reflectance theory is offered in Byrne and Hilbert, "Colors and Reflectances", and is more fully defended by David Hilbert in Color and Color Perception. 21 It will not help, I think, to claim that non-human organisms can never see any of the colors which humans see, and that there is no conflict in saying that SSR1 is both an instance of red and an instance of C1, where Cl is a particular color perceived by another type of organism. Firstly it seems presumptuous to stipulate in advance that no non-human organisms can see any of the colors humans can see. But more importantly, in order for there to be no violation of the color incompatibility thesis in the statement that the Red Delicious apple is both red and C1, C1 would have to be not only a different color from the human colors, but quite different in kind from what we call colors, for to say that an object is (all




over) both red and any other human color at all violates the color incompatibility thesis. It might thus be questionable whether Cl deserved to be called a color at all. 22 See note 5 above for these two accounts. 23 See P.W. Ross, "The Relativity of Color". 24 Jackson and Pargetter, "An Objectivist's Guide to Subjectivism About Color". Jackson and Pargetter offer an account of the meaning of 'red' which is relativized in such a way as to yield the schema "Redness for S in C at t is the property which causes (or would cause) objects to look red to S in C at t", where S is some person, C stands for the circumstances of perception, and t for the time of the perception. They nonetheless argue that we should view the properties which realize this schema in objects as microphysical surface properties of those objects. While their account is not explicitly intended to accommodate different types of perceivers, it could easily be modified to do so. 25 It is important to notice that the truth of response-dependence does not entail that the relation of being red for Ti consists in standardly looking red to normal perceives of Ti. Broadly speaking, the different views of the identify of this relation can be divided into what we might call subjective-relational and objective-relational accounts, and response-dependence in the sense for which I am arguing here is compatible with both of these views. Objective-relational views are those which treat the identity conditions of the relation as being specifiable independently of how objects look to the relevant types of perceivers, while subjective-relational views treat them as being specifiable only by reference to such visual appearances. One type of subjective-relational account might view the relation expressed by 'is red for Ti' as simply the relation of being disposed to standardly look red to normal perceivers of type Ti. Perhaps the most plausible objective-relational account would be one which viewed this relation as the relation of being disposed under standard conditions to cause a certain kind of stimulation in the perceptual system of normal organisms of type Ti, where this stimulation is identified purely by reference to objectively describable facts such as the psychophysical and physiological characteristics of the perceptual system. It is open to the objective-relational theorist to accept response-dependence, by conceding that the objective facts which for him constitute the relation of being red for Ti necessarily coincide with the objects in question standardly looking red to normal perceivers of Ti, while still holding that the nature of this relation can be fully specified by reference to those objective facts independently of the visual appearances. (I take the account of the identity of color properties offered by Gilbert Harman in "Explaining Objective Color in Terms of Subjective Reactions" to be along these lines.) 26 See Mark Johnston, "How to Speak About the Colors", pp. 138, 149-155. I thank an anonymous reviewer for Philosophical Studies for raising questions about how the notion of perceptual availability can be used to distinguish between primary and secondary qualities. 27 See note 31 below for more on this point. 28 Though the terms derive from Peter Unger, the formulations I use here of



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the notions of invariantism and contextualism are adapted from Keith DeRose, "Contextualism and Knowledge Attribution". I here follow DeRose's limitation of the term "contextualism" to views which take the truth-conditions of sentences attributing knowledge to vary according to the context of the attributor, and not merely according to the context of the knowing subject. There are, of course, a great variety of ways of formulating something like a contextualist view of knowledge, and my argument for the perceptual availability of the colors does not depend on the details of the formulation I use here. 29 I will discuss these two interpretations of the norms for color perception further in the final section. 30 In parallel to NPA, RNPA might be stated as follows: Where S is a normal perceiver of type Ti who believes that an object 0 is scarlet red for Ti, and S's belief is based only on perception of 0 in standard conditions for the perception of color by members of Ti together with S's background beliefs that she is a normal perceiver and that she perceived 0 in standard conditions, knowledge-attributing sentences like "S knows that 0 is scarlet red for Ti" are true in all contexts of knowledge attribution. (It may beg some questions about the individuation of beliefs to speak of perceivers of type Ti believing that 0 is scarlet red for Ti, as opposed to believing simply that 0 is scarlet red. Alternatively, a relativist account could adopt the latter method of formulating these beliefs and stipulate that the content of such beliefs needs to be revised in accord with the relational view of color predicates.) 31 My view on this matter thus differs from Jonston's, since he views all of the beliefs associated with our color concepts, even those which lie close to their "core" like perceptual availability (in his sense), as revisable. (See "How to Speak of the Colors".) 32 See P. Boghossian and J.D. Velleman, "Physicalist Theories of Color", pp. 108-109, and also P.W. Ross, "The Appearance and Nature of Color", pp. 230- 232. These arguments were originally aimed at something more akin to Johnston's notion of perceptual availability, but they apply to normal perceptual availability as well. One might be tempted to think normal perceptual availability is incompatible with physicalism on the basis of an argument such as the following (again setting aside relativism): If normal perceptual availability is true, a normal perceiver can know that an object is scarlet red solely on the basis of perception of it in standard conditions; but if scarlet red is identical to a physical property, and one can't know what physical properties an object has simply by looking at it, a normal perceiver will have to investigate the physical nature of an object in order to know it is scarlet red; so if perceptual availability is true, physicalism is false. Such an argument, however, misconstrues what normal perceptual availability claims. It does not say that the normal perceiver can know the identity or constitutive nature of scarlet redness on the basis of standard perception alone. It says only that the normal perceiver can know that a given object is scarlet red on that basis. It is thus quite possible to accept normal perceptual availability and still be a physicalist, since it is possible to acknowledge that we can know which color




an object is from perception alone, apart from physical inquiry, without being able to know the identity or constitutive nature of that color from perception alone. 33 Among those who have advocated reading such descriptions as rigidified on actual perceivers and conditions are S. Kripke, Naming and Necessity, p. 140, note 71; M. Davies and L. Humberstone, "Two Notions of Necessity"; and D.M. Armstrong, "Smart and the Secondary Qualities", p. 39. The rigidified reading has been questioned by Jackson and Pargetter, "An Objectivist's Guide to Subject- ivism About Color", p. 78, and more tentatively by Johnston, "How to Speak of the Colors", pp. 155, 159-160. 34 Hilbert, Color and Color Perception, 81-91. Though Hilbert's argument is directed explicitly against dispositionalism, it would apply to any theory of color according to which there is a logical connection between color properties and color appearances. 35 Hilbert, Color and Color Perception, p. 99. 36 Another type of objection to the view that the colors are response-dependent is worth noting briefly because of its commonness. This type of objection proceeds from alleged counterexamples to the color biconditional. Justin Broackes, for instance, offers an example which supposes that there might be killer yellow objects which kill anyone who looks at them and so are never seen as yellow, even though we know (presumably from the findings of color science) that in fact they are yellow (Broackes, "The Autonomy of Color", pp. 203-205). The natural reply to this example for the response-dependence theorist will be to say that the objects in question would look yellow if their color could be seen. Broackes however views this as an empty response, for he views it at tantamount to maintaining the bioconditional:

(B3) x is yellow iff if only a normal observer y could see what color x is, then y would see x to be yellow.

And this biconditional he views as true but trivial, since an analogous statement could be made about any property, including properties which are clearly not secondary, like being platinum (e.g., "x is platinum iff if only a normal observer could see what kind of substance x is, then he would see x to be platinum"). This objection however seems clearly to trade on the ambiguity of the word 'see' as meaning both "perceive visually" and "know". Clearly the response-dependence theorist means 'see' in the former sense rather than the latter, and thus a clearer way of rendering his claim than (B3) might be:

(B4) x is yellow iff if x presented its standard visual appearance to a normal observer y, then x would look yellow to y.

Clearly no analogous claim could be made concerning platinum. "Standard visual appearance" should here be taken as meaning "standardly caused visual appearance". Mark Johnston has observed that in all our talk about the colors of things there is an implicit reference to the standard causal processes which mediate color perception - in the case of humans, the transmission of light from objects to the eye, and so on - and that the real problem with examples like the killer yellow



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object example is that they bypass this standard causal path. (See Johnston, "How to Speak of the Colors", pp. 143-147.) This causal condition could easily be incorporated into the relativized color biconditional (B 1) by stipulating that some such condition be included in "standard conditions". 37 Hardin, Color for Philosophers, pp. 67-76. 38 Hardin, op. cit., pp. 76-82. 39 It is worth noting that at least one notion of the "normal perceiver" which is widely used as a standard for color-matching in business and industry, the CIE 1931 definition of the standard observer, represents roughly a median human chromatic response as derived from experimental data. See Judd and Wyszecki, Color in Business, Science, and Industry, and for further discussion, Hilbert, Color and Color Perception, pp. 94-95. 40 See for instance McDowell, "Values and Secondary Qualities", Philip Pettit, "Realism and Response-dependence", and Johnson, "Objectivity Refigured". 41 Mark Johnson, for instance, speaks for this reason of the realism he supports in some areas as "qualified realism", in contrast to a notion of "metaphysical realism". See Johnson, "Objectivity Refigured", and also "Dispositional Theories of Value". Philip Pettit urges a similar sort of restriction on realist claims based on response-dependence in "Realism and Response-Dependence", pp. 618-621. 42 In Kant's formulation, for instance, the (transcendental) realist is one who views "outer appearances (their reality being taken as granted) as things-in- themselves, which exist independently of us and our sensibility". Critique of Pure Reason, A369. 43 I draw the idea for such a distinction, and the characterization of objectivism, intersubjectivism, and subjectivism, from Geoffrey Sayre-McCord. But my characterization of what is involved in realism and anti-realism differs substantially from his. See his "Introduction: The Many Moral Realisms". 44 For a fuller critique of the notion of relative truth along these lines, see Chris Swoyer, "True for". 45 I take the minimal realism I describe here to entail, but to be slightly stronger than, the notion of objectivity proposed by John McDowell in "Aesthetic Value, Objectivity, and the Fabric of the World", p. 16. According to this notion, a particular experience may be of an objective reality "if what the experience is an experience of is independent of the experience itself', even if this is not true of the totality of experiences of that kind. 46 See for instance Sayre-McCord, "Introduction: The Many Moral Realisms", pp. 5-6. 47 I am very grateful to Nicholas Wolterstorff, Michael Della Rocca, and Carol Rovane for their helpful comments on earlier drafts of this paper. I especially want to thank Marion Wells for her insightful suggestions concerning earlier drafts, and for many fruitful discussions of these issues.




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Department of Philosophy Middlebury College Middlebury, VT 05753, USA E-mail: jspackma@ middlebury.edu



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Color, Relativism, and Realism