David R. Hilbert

Our question is: how do things look to the color-blind? But what does that mean? Who are the “color-blind”? Approximately 7% of males and fewer than 1% of females (of European descent1) have some form of inherited defect of color vision, and as a result are unable to discriminate some colored stimuli that most of us can tell apart. (‘Color defective’ is an alternative term that is often used; we will continue to speak with the vulgar.) Color vision defects constitute a spectrum of disorders with varying degrees and types of departure from normal human color vision. One form of color vision defect is dichromacy: by mixing together only two lights, the dichromat can match any light, unlike normal trichromatic humans who need to mix three. The most common form of dichromacy (afflicting about 2% of males) is red-green color blindness, or red-green dichromacy, which itself comes in two varieties. A red-green dichromat will not be able to distinguish some pairs of stimuli that respectively appear red and green to those with normal color vision. For simplicity we will concentrate almost exclusively on red-green color blindness.2 In a philosophical context our question is liable to be taken two ways. First, it can be straightforwardly taken as a question about visible properties of external objects like..

When we open our eyes, the world seems full of colored opaque objects, light sources, and transparent volumes. One historically popular view, _eliminativism_, is that the world is not in this respect as it appears to be: nothing has any color. Color _realism_, the denial of eliminativism, comes in three mutually exclusive varieties, which may be taken to exhaust the space of plausible realist theories. Acccording to _dispositionalism_, colors are _psychological_ dispositions: dispositions to produce certain kinds of visual experiences. According to both _primitivism_ and _physicalism_, colors are not psychological dispositions; they differ in that primitivism says that no reductive analysis of the colors is possible, whereas physicalism says that they are physical properties. This paper is a defense of physicalism about color

We can start with a definition. “[C]olour constancy is the constancy of the perceived colours of surfaces under changes in the intensity and spectral composition of the illumination.” (Foster et al. 1997) Given the definition we can now ask a question: Does human color vision exhibit color constancy?1 The answer to the question depends in part on how we interpret it. If the question is understood as asking whether human color vision displays constancy for every possible scene across every possible illumination then the answer is no.2 If the question is understood as asking whether human color vision displays some degree of constancy for some scenes across some range of illuminants then the answer is yes. The more interesting questions involve characterizing the degree of constancy human vision displays, the types of scenes and ranges of illuminants for which approximate constancy can be achieved and the..

Erster Teil Die übliche Auffassung von der Mathematik und ihre Widerlegung.- 1 Die Rolle von Anschauung und Erfahrung.- 2 Die Rolle der Voraussetzungen.- 3 Die Nichtuntrüglichkeit des mathematischen Schliessens.- Zweiter Teil Die landläufige Auffassung von der Physik und ihre Berichtigung.- 4 Physikalische Begriffsbildungen.- 5 Die Gesetze der Physik und ewige Naturgesetze.- 6 Die Beziehung zwischen Theorie und Experiment.- Dritter Teil Fragen philosophischen Charakters.- 7 Physikalische Gesetzlichkeit und Kausalität.- 8 Naturgeschehen und Wahrscheinlichkeit.- 9 Die Rolle von idealen Gebilden.

Color has often been supposed to be a subjective property: a property which has its correct analysis in terms of phenomenological aspects of human experience. The most influential form of subjectivism with respect to color has been the dispositional analysis of Locke and Newton. On this view the color of an object is analyzed in terms of its disposition to produce certain kinds of experiences. ;In contrast with subjectivism an objectivist analysis of color takes color to be a property objects possess in themselves, independently of the character of human perceptual experience. I defend a form of objectivism that identifies color with a physical property of surfaces: their spectral reflectance. This particular form of objectivism with respect to color is shown to be superior to dispositional analyses in doing justice to both the facts of color perception and our common sense intuitions about color. ;Two important features of human color vision are shown to be better accounted for by this form of objectivism than by its rivals. First, the existence of color constancy points to the identification of color with a property of objects such as spectral reflectance rather than with any property of light. Second, the existence of variation in color perception among normal human observers is much more easily accounted for by a objectivist analysis than by a dispositional one. This sort of variation points to the existence of differences of color that are imperceivable by a normal observer in normal circumstances: a fact that conflicts with the main features of dispositional accounts. ;The realization that perception and language give us access to kinds of colors and not to individual determinate colors allows for an account of color perception and language that is consistent with the identification of color with surface spectral reflectance. Color perceptions and color terms convey information about anthropocentric yet objective kinds of reflectances. ;The identification of color with surface spectral reflectance can be defended against the main arguments in favor of subjectivism and preserves most of our pre-analytic beliefs about color.

One of the traditional problems of philosophy is the nature of the connection between perceptual experience and empirical knowledge. That there is an intimate connection between the two is rarely doubted. Three case studies of visual deficits due to brain damage are used to motivate the claim that perceptual experience is neither necessary nor sufficient for perceptual knowledge. Acceptance of this claim leaves a mystery as to the epistemic role, if any, of perceptual experience. It is argued that one function of perceptual experience is to provide information about the sources of beliefs, both as to which perceptual modality and within a given modality. This information is useful in assessing the reliability of perceptual beliefs.

In Colour for Architecture, published in 1976, the editors, Tom Porter and Byron Mikellides, explain that their book was “produced out of an awareness that colour, as a basic and vital force, is lacking from the built environment and that our knowledge of it is isolated and limited.”1 Lack of urban color was then especially salient in Britain—where the book was published—which had just begun to recoil at the Brutalist legacy of angular stained gray concrete strewn across the postwar landscape. Perhaps because the most urgent need was to inject some hue into this architectural dystopia, one of the main innovations illustrated in the book involves nothing more than cans of paint. Dull unfinished concrete façades, the interior of a subway station, a cement works, and so on, are shown enlivened by fields of bright color.

Color-vision defects constitute a spectrum of disorders with varying degrees and types of departure from normal human color vision. One form of color-vision defect is dichromacy; by mixing together only two lights, the dichromat can match any light, unlike normal trichromatic humans, who need to mix three. In a philosophical context, our titular question may be taken in two ways. First, it can be taken at face value as a question about visible properties of external objects, and second, it may be interpreted as the more intangible question of “what it’s like” to be color-blind.

1. The “puzzle” Physical objects are coloured: roses are red, violets are blue, and so forth. In particular, physical objects have fine-grained shades of colour: a certain chip, we can suppose, is true blue (unique, or pure blue). The following sort of scenario is commonplace. The chip looks true blue to John; in the same (ordinary) viewing conditions it looks (slightly) greenish-blue to Jane. Both John and Jane are “normal” perceivers. Now, nothing can be both true blue and greenish-blue; since the chip is true blue, it is not greenish-blue. Hence Jane, unlike John, is misperceiving the chip. Generalizing, the conclusion is that there is widespread misperception of fine-grained shades. According to Tye (2006), and Cohen, Hardin, and McLaughlin (2006), the previous paragraph amounts to a paradox: an apparently unacceptable conclusion has been drawn from apparently acceptable premises via apparently acceptable reasoning. (See also Hawthorne and Kovakovich 2006, 180-1.) Tye swallows the conclusion, aided by a dose of evolutionary speculation. Hardin (1988), on the other hand, rejects the first premise, and denies that physical objects are coloured. Cohen (2004) and McLaughlin (2003) claim that both Jane and John have the colour of the chip right. Our opening paragraph concealed a crucial parameter. In fact, the chip looks greenish-blue-relative-to- circumstances-C to Jane, and true-blue-relative-to-circumstances-C* to John, and the chip has both these relativized colours.1 All this ingenious philosophizing would be in vain, of course, if the conclusion of the opening paragraph were not puzzling or problematic. So, why is it supposed to be? According to Tye, the conclusion is puzzling because John and Jane are both “normal perceivers” (xx). He seems to think that it is (prima facie) plausible to assume..

Philosophers have devoted a great deal of discussion to the question of whether an inverted spectrum thought experiment refutes functionalism. (For a review of the inverted spectrum and its many philosophical applications, see Byrne, 2004.) If Ho?man is correct the matter can be swiftly and conclusively settled, without appeal to any empirical data about color vision (or anything else). Assuming only that color experiences and functional relations can be mathematically represented, a simple mathematical result.

A sensible quality is a perceptible property, a property that physical objects (or events) perceptually appear to have. Thus smells, tastes, colors and shapes are sensible qualities. An egg, for example, may smell rotten, taste sour, and look cream and round.1,2 The sensible qualities are not a miscellanous jumble—they form complex structures. Crimson, magenta, and chartreuse are not merely three different shades of color: the first two are more similar than either is to the third. Familiar color spaces or color solids capture, to a greater or lesser extent, these relations between the colors. The same goes for sensible qualities perceived in other modalities: middle C, high C, and D are not merely three different notes, and the taste of lemons, oranges, and sugar cubes are not merely three different tastes. How can this structure of appearance be explained? One idea is that sensible qualities are of two sorts: basic and derived. The basic sensible qualities are the building blocks from which the derived sensible qualities can be..

Perception and thought are often, although not exclusively, concerned with information about the world. In the case of perceiving though, unlike thinking, it is widely believed that there is an additional element involved, a subjective feeling or, as it is often put, something that it is like to be perceiving. Qualia are these characteristic feelings that accompany perceiving. One motivation for the idea that we experience qualia is that there is a clear difference between seeing a red tomato and thinking that a tomato is red and that the difference has to do with some extra element present in the case of seeing that is absent in the case of thinking. Philosophical attempts to understand qualia and their place in the world have played a central role in recent debates about the nature of mind and its place in the world. Before getting to those debates, we will take a more detailed look at the distinction between the content of perceptual experiences,what they tell us about the world, and their qualitative or phenomenal character, what it is like to experience them.