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Commentary on P. W. Ross: The Location Problem for Color Subjectivism
Consciousness and Cognition 10, 133–139 (2001) doi:10.1006/ccog.2000.0483, available online at http://www.idealibrary.com on
Commentary on P. W. Ross: The Location Problem for Color Subjectivism Zolta´n Jakab Institute of Interdisciplinary Studies, Carleton University, Ottawa, Ontario, K1S 5B6, Canada E-mail: [email protected]
In the present target article, Peter W. Ross argues that no version of subjectivism about color is tenable because none of these views can account for color perception. In this commentary I argue that though Ross’s analysis raises very interesting problems for subjectivism, the argument he offers threatens his favored view of color as well. This is so because Ross’s argument—if it is correct—works against internalism about color experience, not just against subjectivism about color. First let me quickly recapitulate those parts of Ross’s argument that I subsequently criticize. Ross’s strategy is to show that no version of subjectivism can offer a noncontroversial account of color perception. This means that subjectivism about color is probably wrong. Ross identifies three versions of subjectivism, sense-datum subjectivism, adverbialist subjectivism, and the virtual color proposal, and thinks that these versions exhaust the options available to the subjectivist. The first two of these versions view the visual field as an array of sense impressions; the third construes it as an array of represented objects and properties. Ross focuses on the adverbial theory and the virtual color proposal saying that scientifically motivated subjectivists reject sense data. Then he attempts to drive both these proposals into the following impasse. On subjectivism, colors are mental states or events, and we perceive colors as spatially located (i.e., located on external objects). However, it is unclear how we can experience mental events as spatially located. Ross seems to take it for granted, with McGilvray (1994, pp. 226–227), that there is something like a hopeless puzzle here, to which no plausible solution can be found. In evaluating adverbialist subjectivism, Ross argues that it faces certain difficulties in solving the binding problem. One may attempt to overcome these difficulties by appealing to a mixed notion of the visual field on which it is an array of represented physical objects and sensory qualities (i.e., accounting for color in terms of mental events and for objects and locations as entities in the external environment, represented ). This leaves us with the problem mentioned above: Sensed colors are mental events, but how can we experience mental events as spatially located? As Ross argues, the virtual color proposal cannot add anything new to the latter, mixed notion Commentary on P. W. Ross (2001). The location problem for color subjectivism. Consciousness and Cognition, 10(1), 42–58. Address correspondence and reprint requests to Zolta´n Jakab, Institute of Interdisciplinary Studies, 2218 Dunton tower, 1125 Colonel by Drive, Ottawa, Ontario, K1S 5B6, Canada. 133 1053-8100/01 $35.00
Copyright 2001 by Academic Press All rights of reproduction in any form reserved.
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of the visual field; therefore it collapses into the adverbialist account and faces the very same problem. According to the virtual color proposal, virtual colors that we perceive objects as having, ubiquitously and erroneously, derive from the qualitative aspect of color experience. But color experience with its qualitative aspect simply is a range of mental events, experienced as spatially located—once again, we arrive at the same problem. It should be obvious that a key element in the author’s argument is the idea of experiencing mental events as spatially located—therefore this is the one I focus on. First off, I’m not sure that this idea is unintelligible, nor do I think that facing it should deter us from certain philosophical views of color. However, in what follows my aim is not to provide a solution to this problem. Rather, the point I wish to make is that if the assumption of experiencing mental events as spatially located is a problematic one, then the view of color embraced by Ross, namely disjunctive physicalism, is in big trouble as well. This is because, perhaps surprisingly, disjunctive physicalism, just like subjectivism, is bound to conclude that we experience mental events as spatially located. In other words, it seems to me that the author falls into his own trap. Let us see how this unfortunate result unfolds. As we have seen, Ross favors a disjunctive physicalist view of color. However, his account of this view is not very abundant, which suggests that he relies on other authors who support it (e.g., Smart, 1975; Armstrong, 1987). What he explicitly says is that colors are disjunctive physical properties and that certain neural processes give us access to these colors. Furthermore, his distinction between sensed colors and the neural processes themselves corresponds to Hardin’s distinction between sensed colors and sensory qualities (p. 56). The problem with this view is the following. It is not surprising that the eliminativist Hardin identifies color experiences with neural state or event types (Hardin, 1988, pp. 111–112). Saying that color experiences, including their phenomenal characters, are identical to neural states amounts to the claim that the phenomenal properties of color experiences supervene on internal constitution (i.e., internalism about color phenomenology). For Hardin this is no problem: He denies that external objects are colored and claims that color experience falsely represents objects as colored. But how about disjunctive physicalism? A sophisticated version of disjunctive physicalism is defended by Jackson and Pargetter (1997). These authors identify colors with the (physical) bases of dispositions to look colored (p. 70), and realize that colors, construed this way, are highly disjunctive physical properties (pp. 75–76). They do not speak explicitly about the nature and determinants of color experience, but it seems that they are prepared to accept internalism (they come closest to such a view on pp. 74–75,77). A perhaps even more sophisticated view that grew out of, among other things, Jackson’s and Pargetter’s disjunctive physicalism is J. Cohen’s color functionalism (Cohen, 2000). Very roughly, Cohen’s view is that colors are the properties that dispose their bearers to look colored, but these properties themselves are functional ones realized by the different physical bases. Cohen defends the view that phenomenal color experiences are identical to states of the nervous system. Regardless of whether we choose disjunctive physicalism or color functionalism, it is the bases themselves that are causally responsible for eliciting color experience (e.g., Jackson & Pargetter, 1997, pp. 68–69).
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Now, Ross does not offer an account of the nature of color experience. Some of his remarks suggest that he wishes to distinguish between the neural processes involved in color processing and the qualitative aspect of color experience.1 However, despite this effort, it seems that he has to buy into an internalist account of color experience. This is because (P1) any externalist view about color experience has to be able to maintain that object colors play some theoretically interesting role in determining the phenomenal character of color experiences. This is the very essence of externalism about representational content in general and phenomenal character in particular. According to representational externalism, content and phenomenal character do not supervene on internal constitution. However, (P2) disjunctive physicalism has no resource to support the claim that object colors (disjunctive physical properties) play any theoretically interesting role in determining the phenomenal character of color experience. Hence, (C) disjunctive physicalism cannot, in any plausible way, go externalist about color experience. Here is why (P2) obtains. Take, for instance, the set of objects that look to us, in normal circumstances, a particular, perceptually determinate shade of red (say, red16—red16 is a color experience type). Call this set R16. My point: There is no causally effective property that all and only members of R16 have. But then why do we perceive all these members as the same in color and distinct from objects with other colors? We perceive the members of R16 as having a distinctive common property—a property that all and only the members of R16 have. It is true that the heterogeneous color properties of R16 members have a distinctive common functional, or dispositional, core: Each and every one of them disposes its bearer to look red16. However, dispositional properties are not causally effective. Dispositions are merely functional descriptions, if–then statements describing what would happen in certain counterfactual circumstances. It is the bases of dispositions that are causally effective. Moreover, in terms of these bases, R16 is wildly hetergeneous, or disjunctive. In other words, the members of R16 do not constitute a natural kind, not even an anthropocentric one (Hilbert, 1987, pp. 13–15, 115, 119–120). Next, disjunctive physical properties do not enter into causal laws; they do not play causal roles—only their disjuncts do (Tye, 1995, p. 195; Jackson & Pargetter, 1997, 75).2 This prevents us 1
On p. 53 he writes: ‘‘By the term ‘sensed color’ I have simply meant the qualitative aspect of color experience without building into the meaning of this term that sensed colors are mental or physical.’’ 2 Tye simply asserts this in his 1995 book; so do Jackson and Pargetter. I present my own argument for this claim in Jakab (2000). Jonathan Cohen (personal communication) made the following objection to this contention. The primary intuition about color is that colors cause color experiences. Of course, this is a philosophically uninterpreted commonsense view. For instance, in ordinary discourse we do cite dispositions as causes. Now, even if philosophical argument shows that dispositional or functional properties cannot physically cause (only their physical implementations can), this still leaves us with the possibility that dispositional or functional properties can cause in some more derivative sense. To respect our prime intuition we can attribute to colors, as dispositional or functional properties, causation in such a derivative sense. My reply: Perhaps colors, on the dispositionalist view, are causes in some derivative sense; still, they are not ordinary physical causes. But if colors are not ordinary physical causes, then how can they influence, or participate in the determination of, color experience, that is, a natural phenomenon? Natural phenomena are shaped by physical causation. Hence causation in some abstract sense should be analyzed in terms of physical causation, if the aim is to understand how it influences natural physical phenomena. ‘‘Colors (as dispositions to elicit color experience) cause color experiences’’ is analyzed thus: colors are realized in the world by accidental physical bases, and it is these
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from attributing to colors, as disjunctive physical properties, any interesting role in determining the phenomenal character of color experience. That is, the question remains: How could utterly different physical properties play a constitutive role in one and the same color experience, i.e., how could they, despite their heterogeneity, make our visual experience of them phenomenally the same?3 Notice two contrasting cases. First, representationalism about color experience, and type physicalism about object color do have an account of how object colors determine the phenomenal character of color experience (see Tye, 1995; Byrne & Hilbert, 1997). Second, shapes are physical types, and D. Marr’s, I. Biederman’s or S. Kosslyn’s theories about visual perception (i.e., computational stories of how maplike, analog representations about spatial layouts are formed) give us a plausible idea of how shape properties play an important role in determining the subjective (i.e., visual) quality of shape appearances—what it is like to see a particular shape. Obviously, the correctness of type physicalism, hence representationalism, about color is an empirical issue. Type physicalists bite the bullet and claim that there indeed is some physical (surface) property common to all and only physical objects that look to us a particular color in normal circumstances (Hilbert, 1987, p. 111; Byrne & Hilbert, 1997, pp. 265–266; Tye, 1995, pp. 146–147; Matthen, 1988, pp. 24–25). I agree with the author’s tacit assumption that this view is wrong, i.e., colors, if taken to be causally effective physical properties, will turn out to be disjunctive ones, not natural kinds of any sort.4 To summarize, it seems arguable that shapes play an interesting role in determining the subjective quality of shape percepts. To the contrary, colors, on Ross’s view, can play no interesting role in determining the subjective quality, or phenomenal character, of color percepts. Hence disjunctive physicalism, just like eliminativism, prompts us to go internalist about color phenomenology. Objects with very different causally effective physical properties (e.g., R16 members) all elicit in us the same color experibases that physically cause the occurrence of color experience—when the color-dispositions manifest themselves. ‘‘Color (as surface reflectance) causes color experience’’ on the other hand, is analyzed thus: it is not reflectance (the disposition) but its manifestation (the physical event of reflecting light) that causes color experience to occur. A very important difference between these two construals of color (i.e., dispositionalism and the reflectance theory) is that on the former, the manifestation of the relevant dispositions is the occurrence of color experience, whereas on the latter, manifestation is an observerindependent process. 3 Ross seems to accept such a conclusion, when he says (p. 44): ‘‘The fact that for any determinate color, there are indefinitely many metamers, or physically distinct objects that look that color, demonstrates that the categories by which we classify colors as qualitatively identical or different, neither correspond with, nor are explained by, physical categories.’’ 4 However, I think the author is mistaken when he asserts in his note 15 that Tye (1995) proposes disjunctive physicalism. Tye proposes type physicalism about color, in D. Hilbert’s spirit (Hilbert, 1987, p. 111; Tye, 1995, pp. 146–147). He has to do so in order to get his representationist view of the phenomenal going and maintain that colors participate in the determination of the phenomenal character of color experience. To see that such a relation of determination is indeed part of Tye’s view, take a color property (e.g., surface reflectance S623). If this property is represented by the color–vision system then it will give rise to the perceptual content that S623 is present. This content, in turn, is the phenomenal character of the corresponding color experience. In other words, the color property determines the representational content, or what is the same, the phenomenal character, of the corresponding color experience.
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ence. The phenomenal character of this experience cannot plausibly be determined by the disjunctive physical properties of R16 members, hence we have to assume that it is fixed by factors within our skin. The neural state identity thesis provides us with such an internalist account. The experience red16 presents to us the members of R16 as having a common property—a property that characterizes all and only the members of this set. If this presentation is to be preserved as veridical, then we have to admit that all color experience reveals to us are dispositional (or functional) properties of objects—because in terms of dispositional or functional properties, members of R16 do indeed have a distinctive common property. If, however, we want to interpret color experience as giving access to causally effective physical properties of objects, then this access is, in a sense, systematically erroneous. For instance, the red16 experience suggests that all members of R16 have a distinctive common, causally effective physical property (i.e., one and the same physical property in each and every case of perceiving a red16-looking object that is causally responsible for eliciting one’s red16 experience)—but they do not.5,6 A related problem is the following. So far I have argued that color experiences are mental events, with their phenomenal character supervenient on, or detemined by, internal factors, not by colors themselves. Still, we perceive these phenomenal characters as properties of external objects—that is, as located on those objects, in physical space. This is how we can explain the fact that all members of R16 appear to us to have the same color. Here is a bit more detail. If (1) R16 members, regarding their (causally effective, physical) color properties, are heterogeneous, with no common distinctive core, and (2) our color states give us access to these color properties (as assumed by Ross), then why do we not perceive R16 members as different in color? I guess the author’s answer to this question would be that there is some mental processing of the heterogeneous color properties,7 and it is this processing, or ‘‘mental transformation’’ of the heterogeneous color properties, that gives rise to the same 5 It is important to understand in what sense color experience gives us veridical access to physical properties and in what sense it is misleading. As I argued, the experience of red16 presents to us certain physical objects as having a common distinctive physical property—a common causal antecedent of the normal perceptual occurrences of red16—but there is no such property. In this sense the access that red16 gives us to stimulus properties is misleading. However, consider the sense of ‘‘information’’ in mathematical information theory. On this approach, information is understood as a reduction of uncertainty (or elimination of possibilities). For instance, if we learn that, at time T, a run of experiment E (that has eight possible outcomes: O1–O8) yielded an outcome that is either O1 or O2 or O3, we gain information in terms of possibility elimination. In this sense of information, color experience gives us veridical access to causally effective stimulus properties: A normal perceptual occurrence of red16 (correctly) informs us that one of the members of the disjunctive set R16 is present. 6 To see how limited the access given by color experience to stimulus properties is, think of this. We do not need to engage in scientific inquiry in order to find out what the properties revealed to us in shape perception are. Perceiving shapes plus intellectual reflection are enough to form a conception of the essence of shapes (i.e., spatial distributions) that does not make reference to relations to perceivers or their experiences. However, we do need to resort to science in order to clarify what kind of physical properties reliably cause color sensations in us in normal circumstances. 7 See his page 47 where he distinguishes what he calls the direct realist theory of perception from the Gibsonian view.
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color appearance (i.e., red16) for all R16 members.8 However, this reply implies that the color appearance—the mental transform of the external color properties—is an observer-dependent property: It would not be instantiated—simply would not exist— in the absence of perceivers. Yet it is this appearance that we perceive all R16 members as having. Alternatively, Ross could reply that we simply cannot discriminate R16 members, and that is why they appear to us identical in color. However, the fact that we cannot perceptually discriminate the members of a stimulus set leaves open the question whether the members of this set in fact have a distinctive common, causally effective physical property (i.e., constitute some sort of a natural kind, at least a sloppy one).9 If they do not, then the percept that all members of the set give rise to does not correspond to, or indicate, any determinate physical property—it is entirely a mental construct. In sum, it seems to me that disjunctive physicalism runs into the same alleged obstacle as adverbialism and the virtual color proposal. This is because it is not specifically subjectivism about color, but, more generally, internalism about color experience that leads us to the conclusion that somehow we have to experience mental events as spatially located. Moreover, disjunctive physicalism leaves us no option other than to identify color experience—including its qualitative aspect—with mental events or processes. The two alternatives to internalism, namely identifying the qualitative aspect of color experience with either (1) the relevant physical stimulus property itself, as Dretske does (1995, Ch. 3), or (2) with representational content, as Tye does (1995, Ch. 5), are, for the reasons specified above, not available to the disjunctive physicalist. (It is interesting to consider the two different strategies adopted by these authors in order to avoid the theoretical problems arising from the disjunctivity of color stimuli.) Finally, I think internalism about color experience remains quite a cogent view, at least as long as the neatly elaborated philosophical machinery of color-experience externalism (Dretske, 1995; Tye, 1995; Byrne & Hilbert, 1997) rests on as vague and unconvincing empirical foundations as it currently does (see also Matthen, 1988, p. 25; Jakab, 2000). REFERENCES Armstrong, D. M. (1987). Smart and the secondary qualities. In A. Byrne & D. R. Hilbert (Eds.), Readings on color. Vol. 1: The philosophy of color, pp. 33–46. Cambridge, MA: MIT Press. Byrne, A., & Hilbert, D. R. (1997b). Colors and reflectances. In A. Byrne & D. R. Hilbert (Eds.), Readings on color. Vol. 1: The philosophy of color, pp. 263–288. Cambridge, MA: MIT Press. Cohen, J. (2000). Color properties and color perception: A functionalist account. Ph.D. thesis, Rutgers University, New Brunswick, NJ. Dretske, F. (1995). Naturalizing the mind. Cambridge, MA: MIT Press. Hardin, C. L. (1988). Color for philosophers: Unweaving the rainbow. Indianapolis, IN: Hackett.
8 For the sake of simplicity I ignore an important issue about disjunctive physicalism and color functionalism, namely the relativization of colors (Jackson & Pargetter, 1997, p. 72; Cohen, 2000, Ch. 1). 9 It is precisely Hilbert’s analogy between length and reflectance type (integrated triplets of reflectances, Hilbert, 1987, pp. 103–106, 111) that does not hold, if type-physicalism about color is wrong.
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Hilbert, D. R. (1987). Color and color perception: A study in anthropocentric realism. Center for the Study of Language and Information, Stanford University. Jackson, F., & Pargetter, R. (1997). An objectivist’s guide to subjectivism about color. In A. Byrne & D. R. Hilbert (Eds.), Readings on Color. Vol. 1: The philosophy of Color, pp. 67–79. Cambridge, MA: MIT Press. Jakab, Z. (2000). Color physicalism and representational theories of the phenomenal mind: How do they fare in light of philosophical analysis and experimental data? Draft of Ph.D. thesis, Carleton University. Matthen, M. (1988). Biological functions and perceptual content. Journal of Philosophy, 85(1), 5–27. McGilvray, J. A. (1994). Constant colors in the head. Synthese, 100, 197–239. Smart, J. J. C. (1975). On some criticisms of a physicalist theory of colors. In A. Byrne & D. R. Hilbert (Eds.), Readings on Color. Vol. 1: The philosophy of color, pp. 1–10. Cambridge, MA: MIT Press. Tye, M. (1995). Ten problems of consciousness. Cambridge, MA: MIT Press.
Commentary on P. W. Ross: The Location Problem for Color Subjectivism Zolta´n Jakab Institute of Interdisciplinary Studies, Carleton University, Ottawa, Ontario, K1S 5B6, Canada E-mail: [email protected]
In the present target article, Peter W. Ross argues that no version of subjectivism about color is tenable because none of these views can account for color perception. In this commentary I argue that though Ross’s analysis raises very interesting problems for subjectivism, the argument he offers threatens his favored view of color as well. This is so because Ross’s argument—if it is correct—works against internalism about color experience, not just against subjectivism about color. First let me quickly recapitulate those parts of Ross’s argument that I subsequently criticize. Ross’s strategy is to show that no version of subjectivism can offer a noncontroversial account of color perception. This means that subjectivism about color is probably wrong. Ross identifies three versions of subjectivism, sense-datum subjectivism, adverbialist subjectivism, and the virtual color proposal, and thinks that these versions exhaust the options available to the subjectivist. The first two of these versions view the visual field as an array of sense impressions; the third construes it as an array of represented objects and properties. Ross focuses on the adverbial theory and the virtual color proposal saying that scientifically motivated subjectivists reject sense data. Then he attempts to drive both these proposals into the following impasse. On subjectivism, colors are mental states or events, and we perceive colors as spatially located (i.e., located on external objects). However, it is unclear how we can experience mental events as spatially located. Ross seems to take it for granted, with McGilvray (1994, pp. 226–227), that there is something like a hopeless puzzle here, to which no plausible solution can be found. In evaluating adverbialist subjectivism, Ross argues that it faces certain difficulties in solving the binding problem. One may attempt to overcome these difficulties by appealing to a mixed notion of the visual field on which it is an array of represented physical objects and sensory qualities (i.e., accounting for color in terms of mental events and for objects and locations as entities in the external environment, represented ). This leaves us with the problem mentioned above: Sensed colors are mental events, but how can we experience mental events as spatially located? As Ross argues, the virtual color proposal cannot add anything new to the latter, mixed notion Commentary on P. W. Ross (2001). The location problem for color subjectivism. Consciousness and Cognition, 10(1), 42–58. Address correspondence and reprint requests to Zolta´n Jakab, Institute of Interdisciplinary Studies, 2218 Dunton tower, 1125 Colonel by Drive, Ottawa, Ontario, K1S 5B6, Canada. 133 1053-8100/01 $35.00
Copyright 2001 by Academic Press All rights of reproduction in any form reserved.
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of the visual field; therefore it collapses into the adverbialist account and faces the very same problem. According to the virtual color proposal, virtual colors that we perceive objects as having, ubiquitously and erroneously, derive from the qualitative aspect of color experience. But color experience with its qualitative aspect simply is a range of mental events, experienced as spatially located—once again, we arrive at the same problem. It should be obvious that a key element in the author’s argument is the idea of experiencing mental events as spatially located—therefore this is the one I focus on. First off, I’m not sure that this idea is unintelligible, nor do I think that facing it should deter us from certain philosophical views of color. However, in what follows my aim is not to provide a solution to this problem. Rather, the point I wish to make is that if the assumption of experiencing mental events as spatially located is a problematic one, then the view of color embraced by Ross, namely disjunctive physicalism, is in big trouble as well. This is because, perhaps surprisingly, disjunctive physicalism, just like subjectivism, is bound to conclude that we experience mental events as spatially located. In other words, it seems to me that the author falls into his own trap. Let us see how this unfortunate result unfolds. As we have seen, Ross favors a disjunctive physicalist view of color. However, his account of this view is not very abundant, which suggests that he relies on other authors who support it (e.g., Smart, 1975; Armstrong, 1987). What he explicitly says is that colors are disjunctive physical properties and that certain neural processes give us access to these colors. Furthermore, his distinction between sensed colors and the neural processes themselves corresponds to Hardin’s distinction between sensed colors and sensory qualities (p. 56). The problem with this view is the following. It is not surprising that the eliminativist Hardin identifies color experiences with neural state or event types (Hardin, 1988, pp. 111–112). Saying that color experiences, including their phenomenal characters, are identical to neural states amounts to the claim that the phenomenal properties of color experiences supervene on internal constitution (i.e., internalism about color phenomenology). For Hardin this is no problem: He denies that external objects are colored and claims that color experience falsely represents objects as colored. But how about disjunctive physicalism? A sophisticated version of disjunctive physicalism is defended by Jackson and Pargetter (1997). These authors identify colors with the (physical) bases of dispositions to look colored (p. 70), and realize that colors, construed this way, are highly disjunctive physical properties (pp. 75–76). They do not speak explicitly about the nature and determinants of color experience, but it seems that they are prepared to accept internalism (they come closest to such a view on pp. 74–75,77). A perhaps even more sophisticated view that grew out of, among other things, Jackson’s and Pargetter’s disjunctive physicalism is J. Cohen’s color functionalism (Cohen, 2000). Very roughly, Cohen’s view is that colors are the properties that dispose their bearers to look colored, but these properties themselves are functional ones realized by the different physical bases. Cohen defends the view that phenomenal color experiences are identical to states of the nervous system. Regardless of whether we choose disjunctive physicalism or color functionalism, it is the bases themselves that are causally responsible for eliciting color experience (e.g., Jackson & Pargetter, 1997, pp. 68–69).
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Now, Ross does not offer an account of the nature of color experience. Some of his remarks suggest that he wishes to distinguish between the neural processes involved in color processing and the qualitative aspect of color experience.1 However, despite this effort, it seems that he has to buy into an internalist account of color experience. This is because (P1) any externalist view about color experience has to be able to maintain that object colors play some theoretically interesting role in determining the phenomenal character of color experiences. This is the very essence of externalism about representational content in general and phenomenal character in particular. According to representational externalism, content and phenomenal character do not supervene on internal constitution. However, (P2) disjunctive physicalism has no resource to support the claim that object colors (disjunctive physical properties) play any theoretically interesting role in determining the phenomenal character of color experience. Hence, (C) disjunctive physicalism cannot, in any plausible way, go externalist about color experience. Here is why (P2) obtains. Take, for instance, the set of objects that look to us, in normal circumstances, a particular, perceptually determinate shade of red (say, red16—red16 is a color experience type). Call this set R16. My point: There is no causally effective property that all and only members of R16 have. But then why do we perceive all these members as the same in color and distinct from objects with other colors? We perceive the members of R16 as having a distinctive common property—a property that all and only the members of R16 have. It is true that the heterogeneous color properties of R16 members have a distinctive common functional, or dispositional, core: Each and every one of them disposes its bearer to look red16. However, dispositional properties are not causally effective. Dispositions are merely functional descriptions, if–then statements describing what would happen in certain counterfactual circumstances. It is the bases of dispositions that are causally effective. Moreover, in terms of these bases, R16 is wildly hetergeneous, or disjunctive. In other words, the members of R16 do not constitute a natural kind, not even an anthropocentric one (Hilbert, 1987, pp. 13–15, 115, 119–120). Next, disjunctive physical properties do not enter into causal laws; they do not play causal roles—only their disjuncts do (Tye, 1995, p. 195; Jackson & Pargetter, 1997, 75).2 This prevents us 1
On p. 53 he writes: ‘‘By the term ‘sensed color’ I have simply meant the qualitative aspect of color experience without building into the meaning of this term that sensed colors are mental or physical.’’ 2 Tye simply asserts this in his 1995 book; so do Jackson and Pargetter. I present my own argument for this claim in Jakab (2000). Jonathan Cohen (personal communication) made the following objection to this contention. The primary intuition about color is that colors cause color experiences. Of course, this is a philosophically uninterpreted commonsense view. For instance, in ordinary discourse we do cite dispositions as causes. Now, even if philosophical argument shows that dispositional or functional properties cannot physically cause (only their physical implementations can), this still leaves us with the possibility that dispositional or functional properties can cause in some more derivative sense. To respect our prime intuition we can attribute to colors, as dispositional or functional properties, causation in such a derivative sense. My reply: Perhaps colors, on the dispositionalist view, are causes in some derivative sense; still, they are not ordinary physical causes. But if colors are not ordinary physical causes, then how can they influence, or participate in the determination of, color experience, that is, a natural phenomenon? Natural phenomena are shaped by physical causation. Hence causation in some abstract sense should be analyzed in terms of physical causation, if the aim is to understand how it influences natural physical phenomena. ‘‘Colors (as dispositions to elicit color experience) cause color experiences’’ is analyzed thus: colors are realized in the world by accidental physical bases, and it is these
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from attributing to colors, as disjunctive physical properties, any interesting role in determining the phenomenal character of color experience. That is, the question remains: How could utterly different physical properties play a constitutive role in one and the same color experience, i.e., how could they, despite their heterogeneity, make our visual experience of them phenomenally the same?3 Notice two contrasting cases. First, representationalism about color experience, and type physicalism about object color do have an account of how object colors determine the phenomenal character of color experience (see Tye, 1995; Byrne & Hilbert, 1997). Second, shapes are physical types, and D. Marr’s, I. Biederman’s or S. Kosslyn’s theories about visual perception (i.e., computational stories of how maplike, analog representations about spatial layouts are formed) give us a plausible idea of how shape properties play an important role in determining the subjective (i.e., visual) quality of shape appearances—what it is like to see a particular shape. Obviously, the correctness of type physicalism, hence representationalism, about color is an empirical issue. Type physicalists bite the bullet and claim that there indeed is some physical (surface) property common to all and only physical objects that look to us a particular color in normal circumstances (Hilbert, 1987, p. 111; Byrne & Hilbert, 1997, pp. 265–266; Tye, 1995, pp. 146–147; Matthen, 1988, pp. 24–25). I agree with the author’s tacit assumption that this view is wrong, i.e., colors, if taken to be causally effective physical properties, will turn out to be disjunctive ones, not natural kinds of any sort.4 To summarize, it seems arguable that shapes play an interesting role in determining the subjective quality of shape percepts. To the contrary, colors, on Ross’s view, can play no interesting role in determining the subjective quality, or phenomenal character, of color percepts. Hence disjunctive physicalism, just like eliminativism, prompts us to go internalist about color phenomenology. Objects with very different causally effective physical properties (e.g., R16 members) all elicit in us the same color experibases that physically cause the occurrence of color experience—when the color-dispositions manifest themselves. ‘‘Color (as surface reflectance) causes color experience’’ on the other hand, is analyzed thus: it is not reflectance (the disposition) but its manifestation (the physical event of reflecting light) that causes color experience to occur. A very important difference between these two construals of color (i.e., dispositionalism and the reflectance theory) is that on the former, the manifestation of the relevant dispositions is the occurrence of color experience, whereas on the latter, manifestation is an observerindependent process. 3 Ross seems to accept such a conclusion, when he says (p. 44): ‘‘The fact that for any determinate color, there are indefinitely many metamers, or physically distinct objects that look that color, demonstrates that the categories by which we classify colors as qualitatively identical or different, neither correspond with, nor are explained by, physical categories.’’ 4 However, I think the author is mistaken when he asserts in his note 15 that Tye (1995) proposes disjunctive physicalism. Tye proposes type physicalism about color, in D. Hilbert’s spirit (Hilbert, 1987, p. 111; Tye, 1995, pp. 146–147). He has to do so in order to get his representationist view of the phenomenal going and maintain that colors participate in the determination of the phenomenal character of color experience. To see that such a relation of determination is indeed part of Tye’s view, take a color property (e.g., surface reflectance S623). If this property is represented by the color–vision system then it will give rise to the perceptual content that S623 is present. This content, in turn, is the phenomenal character of the corresponding color experience. In other words, the color property determines the representational content, or what is the same, the phenomenal character, of the corresponding color experience.
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ence. The phenomenal character of this experience cannot plausibly be determined by the disjunctive physical properties of R16 members, hence we have to assume that it is fixed by factors within our skin. The neural state identity thesis provides us with such an internalist account. The experience red16 presents to us the members of R16 as having a common property—a property that characterizes all and only the members of this set. If this presentation is to be preserved as veridical, then we have to admit that all color experience reveals to us are dispositional (or functional) properties of objects—because in terms of dispositional or functional properties, members of R16 do indeed have a distinctive common property. If, however, we want to interpret color experience as giving access to causally effective physical properties of objects, then this access is, in a sense, systematically erroneous. For instance, the red16 experience suggests that all members of R16 have a distinctive common, causally effective physical property (i.e., one and the same physical property in each and every case of perceiving a red16-looking object that is causally responsible for eliciting one’s red16 experience)—but they do not.5,6 A related problem is the following. So far I have argued that color experiences are mental events, with their phenomenal character supervenient on, or detemined by, internal factors, not by colors themselves. Still, we perceive these phenomenal characters as properties of external objects—that is, as located on those objects, in physical space. This is how we can explain the fact that all members of R16 appear to us to have the same color. Here is a bit more detail. If (1) R16 members, regarding their (causally effective, physical) color properties, are heterogeneous, with no common distinctive core, and (2) our color states give us access to these color properties (as assumed by Ross), then why do we not perceive R16 members as different in color? I guess the author’s answer to this question would be that there is some mental processing of the heterogeneous color properties,7 and it is this processing, or ‘‘mental transformation’’ of the heterogeneous color properties, that gives rise to the same 5 It is important to understand in what sense color experience gives us veridical access to physical properties and in what sense it is misleading. As I argued, the experience of red16 presents to us certain physical objects as having a common distinctive physical property—a common causal antecedent of the normal perceptual occurrences of red16—but there is no such property. In this sense the access that red16 gives us to stimulus properties is misleading. However, consider the sense of ‘‘information’’ in mathematical information theory. On this approach, information is understood as a reduction of uncertainty (or elimination of possibilities). For instance, if we learn that, at time T, a run of experiment E (that has eight possible outcomes: O1–O8) yielded an outcome that is either O1 or O2 or O3, we gain information in terms of possibility elimination. In this sense of information, color experience gives us veridical access to causally effective stimulus properties: A normal perceptual occurrence of red16 (correctly) informs us that one of the members of the disjunctive set R16 is present. 6 To see how limited the access given by color experience to stimulus properties is, think of this. We do not need to engage in scientific inquiry in order to find out what the properties revealed to us in shape perception are. Perceiving shapes plus intellectual reflection are enough to form a conception of the essence of shapes (i.e., spatial distributions) that does not make reference to relations to perceivers or their experiences. However, we do need to resort to science in order to clarify what kind of physical properties reliably cause color sensations in us in normal circumstances. 7 See his page 47 where he distinguishes what he calls the direct realist theory of perception from the Gibsonian view.
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color appearance (i.e., red16) for all R16 members.8 However, this reply implies that the color appearance—the mental transform of the external color properties—is an observer-dependent property: It would not be instantiated—simply would not exist— in the absence of perceivers. Yet it is this appearance that we perceive all R16 members as having. Alternatively, Ross could reply that we simply cannot discriminate R16 members, and that is why they appear to us identical in color. However, the fact that we cannot perceptually discriminate the members of a stimulus set leaves open the question whether the members of this set in fact have a distinctive common, causally effective physical property (i.e., constitute some sort of a natural kind, at least a sloppy one).9 If they do not, then the percept that all members of the set give rise to does not correspond to, or indicate, any determinate physical property—it is entirely a mental construct. In sum, it seems to me that disjunctive physicalism runs into the same alleged obstacle as adverbialism and the virtual color proposal. This is because it is not specifically subjectivism about color, but, more generally, internalism about color experience that leads us to the conclusion that somehow we have to experience mental events as spatially located. Moreover, disjunctive physicalism leaves us no option other than to identify color experience—including its qualitative aspect—with mental events or processes. The two alternatives to internalism, namely identifying the qualitative aspect of color experience with either (1) the relevant physical stimulus property itself, as Dretske does (1995, Ch. 3), or (2) with representational content, as Tye does (1995, Ch. 5), are, for the reasons specified above, not available to the disjunctive physicalist. (It is interesting to consider the two different strategies adopted by these authors in order to avoid the theoretical problems arising from the disjunctivity of color stimuli.) Finally, I think internalism about color experience remains quite a cogent view, at least as long as the neatly elaborated philosophical machinery of color-experience externalism (Dretske, 1995; Tye, 1995; Byrne & Hilbert, 1997) rests on as vague and unconvincing empirical foundations as it currently does (see also Matthen, 1988, p. 25; Jakab, 2000). REFERENCES Armstrong, D. M. (1987). Smart and the secondary qualities. In A. Byrne & D. R. Hilbert (Eds.), Readings on color. Vol. 1: The philosophy of color, pp. 33–46. Cambridge, MA: MIT Press. Byrne, A., & Hilbert, D. R. (1997b). Colors and reflectances. In A. Byrne & D. R. Hilbert (Eds.), Readings on color. Vol. 1: The philosophy of color, pp. 263–288. Cambridge, MA: MIT Press. Cohen, J. (2000). Color properties and color perception: A functionalist account. Ph.D. thesis, Rutgers University, New Brunswick, NJ. Dretske, F. (1995). Naturalizing the mind. Cambridge, MA: MIT Press. Hardin, C. L. (1988). Color for philosophers: Unweaving the rainbow. Indianapolis, IN: Hackett.
8 For the sake of simplicity I ignore an important issue about disjunctive physicalism and color functionalism, namely the relativization of colors (Jackson & Pargetter, 1997, p. 72; Cohen, 2000, Ch. 1). 9 It is precisely Hilbert’s analogy between length and reflectance type (integrated triplets of reflectances, Hilbert, 1987, pp. 103–106, 111) that does not hold, if type-physicalism about color is wrong.
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Hilbert, D. R. (1987). Color and color perception: A study in anthropocentric realism. Center for the Study of Language and Information, Stanford University. Jackson, F., & Pargetter, R. (1997). An objectivist’s guide to subjectivism about color. In A. Byrne & D. R. Hilbert (Eds.), Readings on Color. Vol. 1: The philosophy of Color, pp. 67–79. Cambridge, MA: MIT Press. Jakab, Z. (2000). Color physicalism and representational theories of the phenomenal mind: How do they fare in light of philosophical analysis and experimental data? Draft of Ph.D. thesis, Carleton University. Matthen, M. (1988). Biological functions and perceptual content. Journal of Philosophy, 85(1), 5–27. McGilvray, J. A. (1994). Constant colors in the head. Synthese, 100, 197–239. Smart, J. J. C. (1975). On some criticisms of a physicalist theory of colors. In A. Byrne & D. R. Hilbert (Eds.), Readings on Color. Vol. 1: The philosophy of color, pp. 1–10. Cambridge, MA: MIT Press. Tye, M. (1995). Ten problems of consciousness. Cambridge, MA: MIT Press.