It is widely believed that some a priori necessary truths are not analytic in the sense of transformable by substitution of synonyms into logical truths. One much-cited example comes from the supposed incompatibility between colour predicates. The idea is that sentences like “Nothing is both blue all over (or uniformly or at a point) and also red” are not transformable into a logical truth in the same way as “Nothing is both a bachelor and married” because the requisite conceptual (...) link between “bachelor” and “not married” is absent between “blue” and “not red”. This paper examines whether colour exclusion may be more like the bachelor case than it initially appears. It transpires that the most promising line of thought is not, however, as has been argued at length in the literature, that “blue” in some more or less convoluted way manages to mean “not red”. Instead it is suggested that the requisite conceptual link may reside in the oft-ignored qualifications (“all over”, “uniformly”, etc.), without which there is no incompatibility in the first place. (shrink)

It is commonly held that Wittgenstein abandoned the Tractatus largely because of a problem concerning color incompatibility. My aim is to solve this problem on Wittgenstein’s behalf. First I introduce the central program of the Tractatus (§1) and the color incompatibility problem (§2). Then I solve the problem without abandoning any Tractarian ideas (§3), and show that given certain weak assumptions, the central program of the Tractatus can in fact be accomplished (§4). I conclude by distinguishing (...) my system of analysis from others and by explaining the historical underpinnings of my understanding of the nature of elementary propositions (§5). (shrink)

After Tractatus Logico-Philosophicus, Wittgenstein realized that elementary propositions may logically conflict with each other, due to the fact that the most elementary measurements may contradict each other. This led to the view that logic consists of various calculi. A calculus consists of measurement scales, each scale being a rule for the application of numbers. These scales determine logical relationships between elementary propositions by reason of arithmetical relations. Attempts to reject Wittgenstein's change in viewpoint, which ignore the relevance of measurement and (...) arithmetic, are remiss. In this light, I discuss Sarah Moss’s criticism of intermediate Wittgenstein. (shrink)

A traditional view is that all necessary truths are analytic. A frequent objection is that certain claims of color incompatibility – e.g., ‘Nothing is both red and green all over’ – are necessarily true but not analytic. I argue that this objection to the traditional view fails because such color incompatibility claims are either analytic or contingent.

Relationalism is a view popularized by Cohen according to which the colors are relational properties. Cohen’s view has the unintuitive consequence that the following propositions are false: (i) no object can be more than one determinate or determinable color all over at the same time; (ii) ordinary illusion cases occur whenever the color perceptually represented conflicts, according to (i) above, with the object’s real color; and (iii) the colors we perceive obey (i). I investigate Cohen’s attempt to (...) address these intuitive propositions with which his view struggles and find it to be incompatible with how he motivates his view. (shrink)

Este artigo trata do chamado “problema de incompatibilidade de cores”, enfrentado por Wittgenstein no Tractatus Logico-Philosophicus, em seus Manuscritos inéditos 105 e 106, e em seu único artigo publicado – “Some Remarks on Logical Forms” (SRLF). Nossa tarefa será dupla. Primeiro, pretendemos mostrar como e por que Wittgenstein ficou preso nesse dilema. Nossa segunda tarefa será muito mais específica.Tentaremos elucidar alguns detalhes sobre a impossibilidade de reduzir predicados de cor a unidades mais fundamentais de brilho, croma e intensidade. Nosso objetivo (...) é mostrar como e por que os números tiveram que ser introduzidos na estrutura interna das proposições elementares. Também queremos investigar como Wittgenstein tentou fazer isso através da ideia de um “esquema” e uma operação nãover-funcional. Pretendemos também apresentar algumas vantagens que Wittgenstein obteve ao usar uma notação de barra para sua construção dos “esquemas”.AbstractThis paper deals with the so-called “color incompatibility problem”, faced by Wittgenstein in the Tractatus Logico-Philosophicus, in his unpublished Manuscripts 105 and 106, and in his only published paper – “Some Remarks on Logical Forms” – (SRLF, for now on). Our task will be a twofold one. First, we aspire to show how and why Wittgenstein got stuck into that dilemma. Our second task will be much more specific. We will try to elucidate some details about the impossibility of reducing color predicates to more fundamental units of brightness, chroma, and intensity. We aim to show how and why numbers had to be introduced into the inner structure of elementary propositions. We also want to investigate how he tried to do that through the idea of a “scheme” and a non-truth functional operation. We aim also to present some advantages Wittgenstein gained from using a bar notation for his construal of the “schemes”. (shrink)

Are the following propositions true of the colors: No object can be more than one determinable or determinate color all over at the same time (Incompatibility); the colors of objects are mind-independent (Objectivism); and most human observers usually perceive the colors of objects veridically in typical conditions (Veridicality)? One reason to think not is that the empirical literature appears to support the proposition that there is mass perceptual disagreement about the colors of objects amongst human observers in typical (...) conditions (P-Disagreement). In this article, we defend Incompatibility, Objectivism, and Veridicality by calling into question whether the empirical literature really supports P-Disagreement. (shrink)

Abstract:Russell (in Principles of Mathematics) and Wittgenstein (in Tractatus Logico-Philosophicus) largely agree on the twin questions of why pairs of congruent objects cannot always be made to coincide and why surfaces can never be uniformly two colours at once. Both philosophers take space and colour to be mathematically representable, construe the relevant impossibilities as mathematical and hold that mathematical impossibility is at root logical. It is not by chance that Russell says nothing about the phenomena in his Introduction to the (...) Tractatus or surprising that Wittgenstein was unmoved by the objection that his account of colour incompatibility puts paid to his early philosophy. (shrink)

This article attempts to do two things. The first is to make it plausible that any adequate dispositional view of color will have to associate colors with complex functions from a wide range of normal circumstances to a wide range of (simultaneously) incompatible color appearances, so that there will be no uniquely veridical appearance of any given color. The second is to show that once this move is made, dispositionalism is in a position to provide interesting answers (...) to some of the most challenging objections that have been pressed against it. It explains why colors do not seem to come on when the lights come on, and why the right thing to say seems to be that the light causes the objects to reveal their colors. It explains why the content of visual experience need not be problematically circular. It eliminates the problem of intrapersonal variation in color appearance. And it even provides resources for dealing with the problem of interpersonal variation. It is true that in moving to the more complex view, the dispositionalist becomes subject to a new objection, which has been called the problem of unity. The paper offers a solution to this problem as well. (shrink)

In this paper I will discuss some interesting philosophical questions bound to color science, in its variant founded by Berlin and Kay’s linguistic and anthropological research. I will first refer to various criticisms, expressed by dissenting scientists. Further criticisms implied by a rather philosophical perspective will follow; a particular attention is paid to the question of synchronicity vs . diachronicity. The controversy about Berlin and Kay’s conception is paralleled by the development of Wittgenstein’s views on color that I (...) will sketch in short. Wittgenstein’s philosophy offers tools for illuminating the problem from yet another point of view. In the final part of the paper, I will try to point to the limits of the conception of basic color categories, but also to assess its relevance and possible philosophical contribution in terms of language games variety; especially with respect to the Color Incompatibility The orem and its implications. (shrink)

Intrapersonal variation due to color contrast effects has been used to argue against the following intuitive propositions about the colors: No object can be more than one determinable or determinate color of the same grade all over at the same time ; external objects are actually colored ; and the colors of objects are mind-independent. In this article, I provide a defense of Incompatibility, Realism, and Objectivism from intrapersonal variation arguments that rely on color contrast effects. (...) I provide a novel, ecumenical response to such arguments according to which typical variants are right, and which respects Incompatibility, Realism, and Objectivism, using the thesis that the colors of objects depend on the colors of objects in their surrounds. (shrink)

An important motivation for relational theories of color is that they resolve apparent conflicts about color: x can, without contradiction, be red relative to S1 and not red relative to S2. Alas, many philosophers claim that the view is incompatible with naive, phenomenally grounded introspection. However, when we presented normal adults with apparent conflicts about color (among other properties), we found that many were open to the relationalist's claim that apparently competing variants can simultaneously be correct. This (...) suggests that, philosophers' claims to the contrary notwithstanding, introspection does not supply authoritative and unambiguous reason to reject color relationalism. (shrink)

Studying colour vision across various species suggests that different species perceive different colours (the Disunity Hypothesis). It is plausible that all species’ color visual systems are, at least in principle, equally correct/veridical regarding colour (Ecumenicism). Assuming that colours are mind-independent features of material objects (Objectivism), it follows that objects simultaneously have different colours for different species (Pluralism). But are all these colours compatible with one another? Some have argued that they are on grounds that, while comparisons between colours are (...) possible within a given species’ colour space, they are not possible across the colour spaces of different species. Since colours from different spaces are not comparable, they cannot be incompatible. Hence, a given object can have a colour from as many colour spaces as needed to explain interspecies variations in colour perception. I argue that this reasoning is flawed in two ways. First, colour spaces that are non-comparable in pure or abstract reasoning, may nonetheless be comparable in applied contexts. Second, in our applied context – our world – evidence suggests that incompatibilities between colours from different species’ spaces are extremely likely when Colour Objectivism is presumed. But then the Pluralist solution to interspecies variation seems unavailable to the colour objectivist. (shrink)

In their article ‘In defense of incompatibility, objectivism, and veridicality about color’ P. Roberts and K. Schmidtke offer the results of an experiment supposed to show that if selection of colored samples representing unique hues for subjects has a greater inter-subject variability than identification of sample pairs with no perceptual difference between them the result provides support for the philosophical concept of color realism. On examining the results in detail, we find that, according to standard statistical methodology, (...) the relative magnitude of inter-subject variability in the matching experiment is for both tested colors larger than that in the naming experiment, thus invalidating their claims. In addition, we point out several serious shortcomings in the experiment. (shrink)

Humans have only finite discriminatory capacities. This simple fact seems to be incompatible with the existence of appearances. As many authors have noted, the hypothesis that appearances exist seems to be refuted by reductio: Let A, B, C be three uniformly coloured surfaces presented to a subject in optimal viewing conditions, such that A, B, and C resemble one another perfectly except with respect to their colours. Their colours differ slightly in the following way: the difference between A and B (...) and the difference between B and C are below the discrimination threshold, but the difference between A and C is above this threshold. According to an intuitive construal of what an appearance is, given that A and B appear (to the subject) identical in colour, A and B have the same (colour1) appearance P1; likewise, B and C have the same appearance P2. B's appearance is both P1 and P2. This seems to imply that P1=P2. But then, A and C also have the same appearance, which contradicts the hypothesis that A and C are discriminable. If A and C are discriminable with respect to their colour, they do not have the same appearance with respect to colour. The paradox arising from such a series of judgments of sameness or difference between pairs of coloured surfaces seems to belong to the class of sorites paradoxes. I will show that there is a way to construe colours and their appearances in a way that does not fall prey to the reduction just sketched. (shrink)

The polarity of light and dark in the treatment of the Newtonian spectrum and the inverse spectrum is studied further and the validity of heterogeneity of light and darkness in relation to Goethe’s views is examined. In order to clarify the reality of the “darkness rays”, theexperimentum crucisis re-evaluated. It is shown that the commonly accepted analysis contains assumptions in the choice of the spectrum and background, which mask the inherent dynamic of the spectrum. The relation between colour and wavelength (...) is re-examined with respect to the immutability and specific refrangibility of colour. It is then shown that both these properties are approximations that apply under the specific conditions that have later become standardized in spectroscopy, leading to a consensus regarding the relation of wavelength to colours of one particular spectrum. This consensus has resulted in the study of colour diverging into spectroscopy and colour physiology. As an alternative, the basis of the dichotomy postulated by Müller is studied, leading to the realization that the resolution of this dichotomy was begun by Goethe with the idea of turbidity. A further study shows that turbidity resolves the apparent incompatibility of light and dark. (shrink)

Objectivism and projectivism are standardly taken to be incompatible theories of color. Here we argue that this incompatibility is only apparent: objectivism and projectivism, properly articulated so as to deal with basic objections, are in fundamental agreement about the ontology of color and the phenomenology of color perception.

Data about perceptual variation motivate the ecumenicist view that distinct color representations are mutually compatible. On the other hand, data about agreement and disagreement motivate making distinct color representations mutually incompatible. Prima facie, these desiderata appear to conflict. I’ll lay out and assess two strategies for managing the conflict—color relationalism, and the self-locating property theory of color—with the aim of deciding how best to have your cake and eat it, too.

Data about perceptual variation motivate the ecumenicist view that distinct color representations are mutually compatible. On the other hand, data about agreement and disagreement motivate making distinct color representations mutually incompatible. Prima facie, these desiderata appear to conflict. I’ll lay out and assess two strategies for managing the conflict—color relationalism, and the self-locating property theory of color—with the aim of deciding how best to have your cake and eat it, too.

Drawing on remarks scattered through his writings, I argue that Leibniz has a highly distinctive and interesting theory of color. The central feature of the theory is the way in which it combines a nuanced subjectivism about color with a reductive approach of a sort usually associated with objectivist theories of color. After reconstructing Leibniz's theory and calling attention to some of its most notable attractions, I turn to the apparent incompatibility of its subjective and reductive (...) components. I argue that this apparent tension vanishes in light of his rejection of a widely accepted doctrine concerning the nature of bodies and their geometrical qualities. (shrink)

The One remains, the many change and pass;Heaven's light forever shines, Earth's shadows fly;Life, like a dome of many-coloured glass,Stains the white radiance of Eternity,Until Death tramples it to fragments.At its widest, ‘pluralism’ signifies simply the variety of life, the teeming multitude of forms and entities, the many different properties that living beings manifest. Life is not everywhere the same but impressively differentiated, and without it eternity would be all of a piece, uniform. That is enough for life to stain (...) the white radiance of eternity. But within the multiplicity of specifically human life there are not merely differences. There are tensions, oppositions, conflicts. In contemporary philosophical debate ‘pluralism’ then comes to signify one problematic aspect of this. Groups of people have perhaps always subscribed to very different values, and in consequence favoured very different forms of behaviour from one another, at least on a global scale. But the groups are no longer geographically separated: we live in distinct but overlapping cultures, and get in one another's way to a far greater extent than previously. Shelley's ordered image of the dome may then seem inappropriate, and it may seem unnecessary for death to trample it to fragments. Life is already fragmented, and the practical problem facing us as living creatures is to go beyond the fragments, to achieve at least a modus vivendi in the light of all our differences and incompatibilities even if not the orderliness and cohesion of a dome. Somehow, we have to live together. That is a practical problem which confronts us at every level, as members of families, neighbourhoods, departments, countries and increasingly simply as members of a world-wide human race. (shrink)

By 1929, after the full acknowledgment of the colour–exclusion problem, Wittgenstein had to admit that material incompatibilities presented in conceptual systems could not be reduced to formal tautologies and contradictions. Wittgenstein then, in his middle period, had to examine the kind of negation which, for instance, colour systems should render, which expose not just one but many or, in some cases, infinite inferentially articulated alternatives. Here, inspired by Brandom’s inferentialism, I explore the idea that Wittgenstein, in his middle period, advocated (...) a form of inferentialism based on the inferentially articulated content of propositions in Satzsysteme. At that time, Wittgenstein suggested that every sentence should be logically connected to many others. I call this feature inferential thickness. Therefore, I use Löf’s normative read of verificationism to explain Middle Wittgenstein’s holist solution to problems concerning the use of negation related to material incompatibilities and determination of propositional sense. I also investigate the distinction between contrariety and contradiction and some possible connections to a mandatory restriction of the principle of excluded middle in Satzsysteme. (shrink)

The paper aims at comparing Wittgenstein’s discussion of color exclusion in his to Johnson’s doctrine of determinable and determinate expounded in his. I first summarize Wittgenstein’s developments about the incompatibility of elementary propositions and about the logic of color statements. In the second part, I present and discuss Johnson’s doctrine in relation to Wittgenstein’s development. In a third conclusive moment, drawing on a early work of Prior, I argue that the distinction made by Wittgenstein and Johnson between (...) predication and determination should be looked at from a long term historical perspective. (shrink)

In 1929, Wittgenstein reconsidered the vexing color-Incompatibility problem: explaining how and why more than one color cannot be at a single time and place. He continued discussing the problem in 1930 and later. He offered solutions in the "tractatus", In 1929 and in 1930. Are the solutions the same? clearly not, Because the 1929 solution differs from his earlier one. However, I argue that the 1930 solution is substantially identical with that of 1929 and that the 1929-30 (...) solution is continuous with the "tractatus" as well as some later doctrines. Therefore 1929-30 marks a period of intellectual ferment rather than massive abandonment of his earlier views. (shrink)

This chapter focuses on the incompatibility of afterimage colors. Several quasilogical, semantic, and metaphysical questions having to do with incompatibility come up in color theory, and the problem is so complicated and fragile that it is argued here that, despite some marvelous work on the topic, the problem remains to be sorted out. Every naive subject who encounters afterimages without prejudice has agreed that they have color; this is mentioned here because it is the initial and (...) also the commonsense view. However, accepting that a physical account of color incompatibility is right for physical colors makes an account for the incompatibility of afterimage colors improbable. One can provide a physiological account based on opponent processes, but this will deliver only a contingent truth or a necessity relative only to a particular retinal structure and postretinal neural coding. (shrink)

From now on I will assume that it is possible in principle for there to be cases of spectrum inversion in which the invertees are equally good perceivers of the colors. What I want to show next is that while allowing this possibility is incompatible with standard representationalism, it requires acceptance of a different version of representationalism. Consider the standard way of describing a case of spectrum inversion. Returning to Jack and Jill, we say that red things look to Jack (...) the way green things look to Jill, blue things look to Jack the way yellow things look to Jill, and so on. Of course, we might also express this by saying that the phenomenal character of Jack’s experience of red things is like the phenomenal character of Jill’s experience of green things, and so on. Or by saying that “what it is like” for Jack to see red things is “what it is like” for Jill to see green things, and so on. But “phenomenal character” is philosophical jargon, and “what it is like” is on its way to being that. We need to be able cash these locutions in terms that we are sure we understand. And I think that the best way of doing that is in terms of how things look. Now the sense in which red things look different to Jack and Jill cannot be that they look to have different colors in the epistemic sense. We can suppose that both perceive red things as being red, and therefore that to both red things look red in the epistemic sense. Nor can it be the comparative sense – to each, we can suppose, red things look like standard red things under standard conditions. The remaining sense of “looks” is supposed to be the phenomenal sense. Now those who employ this notion typically speak of things as looking red, blue, yellow, etc., in the phenomenal sense. But if Jack and Jill are both accurate perceivers of the colors of things, it can’t be that the difference in how things look to them is a difference in what colors things look to them, even if “looks” is used in the phenomenal sense.. (shrink)

McDowell recently renounced the assumption that the content of any knowledgeable, perceptual judgement must be included in the content of the knowledge grounding experience. We argue that McDowell’s introduction of a new category of non-inferential, perceptual knowledge is incompatible with the main line of argument in favour of conceptualism as presented in Mind and World [McDowell, John. 1996. Mind and World. 2nd ed. Cambridge, MA: Harvard University Press]. We reconstruct the original line of argument and show that it rests on (...) the assumption that a specific model of justification, the Comparison Model, must apply to all cases of non-inferential, perceptual knowledge. We then show that the Comparison Model cannot be applied to McDowell’s new category of non-inferential, perceptual knowledge. As a consequence, McDowell is in need of an alternative model of justification and an alternative argument for conceptualism. We propose such an alternative model of justification based on McDowell’s reading of Sellars, but argue that the model only serves to make the need for an alternative motivation for conceptualism more urgent. (shrink)

Wittgenstein introduced his claim about colour incompatibility originally in the Tractatus Logico-Philosophicus , where he stated that there could be only one colour in one place and time. It is commonly believed that Wittgenstein abandoned his conception of logical atomism when he realized the consequences of this claim. The aim of this article is to provide an interpretation of the colour incompatibility claim in terms of Wittgenstein’s phenomenology. I will focus on two works of great significance for the (...) claim: Some Remarks on Logical Form and Philosophical Remarks . These two works were written between 1929 and 1930, which is the beginning of the “middle period” in Wittgenstein’s philosophy. I will focus not only on Wittgenstein’s formulation of the colour incompatibility claim, but also on how this claim was justified. The explanation of Wittgenstein’s justification of this claim will help to understand his phenomenology and theory of philosophical grammar. (shrink)

Some colors are compound colors, in the sense that they look complex: orange, violet, green..., by contrast to elemental colors like yellow or blue. In the chapter 3 of his Unterschungen zur Sinnespsychologie, Brentano purports to reconcile the claim that some colors are indeed intrinsically composed of others, with the claim that colors are impenetrable with respect to each other. His solution: phenomenal green is like a chessboard of blue and yellow squares. Only, such squares are so small that we (...) cannot discriminate between their location in perception. Consequently we get the impression of an homogeneous green extent. After having presented Brentano's solution, we argued that it is hardly compatible with Brentano's own conception of descriptive psychology, to the extent that it introduces in-existent objects (small yellow and blue squares), which cannot be perceived. We propose another solution to Brentano's puzzle, more in tune with his own assumptions, or so we argue. According to it, the yellow and the blue are in the green without being spatially in the green. A green extent has yellow and blue components, but these are not spatial components. This solution reconciles impenetrability (since the component colors are not localized) with the reality of compounds color. Besides, it has the advantage of taking the phenomenology of compounds colors, as Brentano's describes it, to the letter. Compound colors are what they seem: complex but not spatially complex. (shrink)

This paper discusses knowledge of opposites. In particular, attention is given to the linguistic notion of antonymy and how it represents oppositional relations that are commonly found in perception. The paper draws upon the long history of work on the formalisation of antonymy in linguistics and formal semantics, and also upon work on the perception of opposites in psychology, and an assessment is made of the main approaches. Treatments of these phenomena in linguistics and psychology posit that the principles of (...) minimal difference and invariance are centrally important. It will be suggested that the standard approach employing meaning postulates fails to capture the relevant notion of antonymy, in part because it is not informed by these principles, and in part due to a number of other problems with this kind of approach, many of which may be overcome by building in the central principles from the beginning. The paper also discusses the issue of whether we can know that opposites necessarily exclude each other and, if so, how. This issue is intertwined with what is known as the colour incompatibility problem that Wittgenstein wrangled with at various times during his life. The paper assesses various solutions to these problems including an approach that was first put forward by Jerrold J. Katz. The relation between this approach and the theory of determinables and determinates is also examined. A further development upon this approach is proposed and then applied to the case of the formalisation of antonymy. It is argued that this approach avoids the problems suffered by the main approaches discussed earlier in the paper. (shrink)

What sort of property did Locke take colors to be? He is sometimes portrayed as holding that colors are wholly subjective. More often he is thought to identify colors with dispositions—powers that bodies have to produce certain ideas in us. Many interpreters find two or more incompatible strands in his account of color, and so are led to distinguish an “official,” prevailing view from the conflicting remarks into which he occasionally lapses. Many who see him as officially holding that (...) colors are dispositions concede that some of his remarks imply that colors are in us rather than in objects. After raising some difficulties for these readings, I offer an alternative. I will argue that Locke takes colors to be relational, but not dispositional, properties of the objects around us. On his view, an object is red if and only if it is actually causing a certain sensation in some observer. (shrink)

There is a tension at the heart of Lucy Allaiss transcendental idealism. The problem arises from her use of two incompatible theories in contemporary philosophy - relationalism about perception, or naïve realism, and relationalism about colour, or more generally relationalism about any such perceptual property. The problem is that the former requires a more robust form of realism about the properties of the objects of perception than can be accommodated in the partially idealistic framework of the latter. On Allais’ interpretation, (...) Kant’s notorious attempt to balance realism and idealism remains unstable. (shrink)

Physicalism is incompatible with what is known as the possibility of zombies, that is, the possibility of a world physically like ours, but in which there are no conscious experiences. But it is compatible with what is known as the possibility of ghosts, that is, the possibility of a world which is physically like ours, but in which there are additional nonphysical entities. In this paper we argue that a revision to the traditional definition of physicalism designed to accommodate the (...) possibility of ghosts inadvertently accommodates what is known as the possibility of inverted spectra, that is, the possibility of a world which is physically like ours, but in which colour experience is inverted. This consequence is unwelcome, because it is widely agreed that the possibility of inverted spectra is incompatible with physicalism. We argue for a revised definition of physicalism which resolves this problem. We then use our definition to argue that physicalism is not compatible with what is known as the possibility of blockers, that is, the possibility of a world which is physically like ours, but in which additional nonphysical entities have prevented the existence of conscious experience. This undermines Stephan Leuenberger's attempt to defend physicalism from arguments which purport to establish the possibility of zombies. (shrink)

Cohen begins by defining ‘Color Physicalism’ so that the position is incompatible with Color Relationalism (unlike Byrne and Hilbert 2003, 7, and note 18). Physicalism, in any event, is something of a distraction, since Cohen’s argument from perceptual variation is directed against any view on which minor color misperception is common (Byrne and Hilbert 2004). A typical color primitivist, for example, is equally vulnerable to the argument. Suppose that normal human observers S1 and S2 are viewing (...) a chip C, as in Cohen’s example. C looks unique green to S1, and bluish green to S2. The problem, as Cohen has it, is to explain “what could (metaphysically) make it the case” that S1, say, and not S2, is perceiving C correctly. He purports to find the explanation “extremely hard to imagine”, and so concludes that both S1 and S2 are perceiving C correctly. (That is not the only option, of course: Hardin concludes that neither is perceiving the chip correctly.). (shrink)