Melinda Campbell, Ph.D.

2. The Color of Reality: Ontological Perspectives on Mind-World Relations or “Saving the Phenomena” Melinda Campbell, Ph.D.

3. The Phenomenal World Why is the sky blue? Are rainbows real?

4. Motivations for Philosophical Research on Color • Longstanding debate that deals with significant metaphysical and epistemological issues: • What do things having the same color have in common? • Are colors properties of external objects or of internal experiences? • Both scientists and philosophers face puzzles about color; skepticism about basic perceptual beliefs is troubling. • Knowledge about the nature of color bears on the nature of consciousness: even though science has no adequate explanation of experiential properties or subjective, qualitative phenomena, color perception is perhaps the best understood aspect of mental life from a scientific standpoint. • Philosophical problems about color can be seen as analogous to other problems, such as the existence of free will, or the ontology of ethical-value properties, and meaning properties.

5. How many colors are there in the visible spectrum?

6. white light refracted through a prism is dispersed into colored light

7. Wavelengths of the Visible Spectrum

20. Can you name these colors?

21. Can you name these colors?

22. Can you name these colors?

34. Trichromatic/Normal Dichromatic/Protanopia Same objects, same illumination, same lightwave-reflectance distributions: Different colors?

35. Some Commonsense Beliefs & Intuitions about Color • Colors are simple, observable, relatively stable features of the external world that exist independently of being perceived. • Opaque and translucent physical objects, natural elements, and composite natural formations or substances all have some color. • Colors are fully revealed in standard cases of color experience—we need only to look at something (in proper illumination) to know what color it is (Johnston’s “Revelation” and “Availability”). • Things that are colored remain colored in the dark, in poor or obscure viewing conditions, and when unperceived. • Color properties are distinct from, and are the causes of, color appearances or color experience—I see red because I’m looking at a red object/surface. • Perceptual experience is “transparent”: Color qualities seem to belong to the objects being perceived, not to experiences, brain states or visual fields. • Dreams, illusions, and hallucinations are not colored in the same sense that everyday objects are colored.

36. Being Blue Cobalt: A paradigm instance of blue

37. Some Scientific Claims about Color • “Color is energy”: Color phenomena are the result of interactions of light and physical matter (i.e., electromagnetic wave energy and electrons), together with properties of perceivers’ visual systems. • Color is not a property of objects per se; color is constructed by the brain and visual system, i.e., neural processing of differential lightwave stimuli. • There are three distinct attributes of color: (1) hue, (2) saturation/ purity/chroma, and (3) lightness/brightness, and these values together determine color identity. • Color vision may be understood as a way of using wavelength discrimination in the construction of visual representations. • The colors that we see are completely dependent on the sensitivity ranges of genetically coded photo-pigments in the cones of the retina. • (Infinitely) many different combinations of light wavelengths (e.g., distinct spectral power distributions) can produce the same color appearance. • Many different types of microphysically constituted surfaces may have the same spectral reflectance profile. • Color constancy: Colors generally maintain the same appearance despite changes in (broadband) illumination.

38. Opponent Theory of Color Vision • Light hits the retinal photoreceptors; information about color and about intensity of light is then sorted into three "channels." • Channels = axon pathways from retinal ganglion cells, which receive all cone information, to the brain. • Two color/wavelength channels; one intensity/brightness channel. • One of the two color channels responds to long-wave or to medium-wave light: Certain ganglion cells will fire signals if stimulated by long-wave light (messages sent by L cones) and will decrease firing if they get signals from M cones; other ganglion cells do the opposite. • In the other channel, ganglion cells work similarly, being excited or inhibited by differential inputs from the L, M, and S cones. • The "intensity channel" also works in a similar manner: the sum of L, M, and S cone input results in different ganglion cells detecting black, white, or shades of gray.

39. retinal structures, visual pathways, visual cortex light phenomenal qualia (mental "sense data") spectral reflectances surface microphysical particles Where is the color of the apple?

40. Some Philosophical Claims about Color • COLOR REALISM: • Color Primitivism: Ordinary perception gives us a complete and satisfactory account of what color is. Like shapes, colors are sui generis, non-reductive, objective properties. • Color physicalism – Colors are identical to the microphysical properties of surfaces and volumes or the spectral power distributions of light emissions. • DISPOSITIONALISM: • Objective dispositionalism: Colors are the spectral-reflectance (or emission) capacities of objects and light sources. • Subjective dispositionalism (Response-dispositionalism): Colors are the mind-dependent “powers” of objects to cause color experience. • COLOR ANTI-REALISM: • Color eliminativism – External, visible objects are not colored; color is instantiated only in subjective color experience. • Non-intentional Color Eliminativism – the “Qualia” view. • Intentional Color Eliminativism – the Representationalist view. • COLOR COMPATIBILISM: • Subjective Realism – Color is instantiated in color appearances, which are to be conceived as spatio-temporal events involving both subjective and objective components.

41. Desiderata for a Theory of Color A satisfactory theory of color should: • Cohere with the findings of empirical research in color science and augment the scientific study of color. • Provide a means for adequately and accurately individuating colors and identifying criteria for determining color categories. • Explain the relation between color and experience of color. Explain why and how creatures have color experience. • Explain certain essential features of color: structural qualities such as color similarity and color matching (blue is more similar to purple than to yellow), and being “binary” or “unitary” in color (there are yellowish reds, but no greenish reds). • Account for epistemic access (knowledge by acquaintance): The color of something can be known just by seeing it; colors are revealed simply through unaided visual perception.

42. Color Realism: Color Physicalism • Colors are a particular subset of subatomic structural properties of physical matter (the “Australian view” – Armstrong, Smart, Lewis, Jackson). • Different kinds of matter, consisting of different energy states and electron configurations, will interact with light in different ways. • Colors, conceived as surface micro-structural properties, cause different perceptual responses (color appearances). Ideally, we should find some objective, scientifically significant, property shared by all instances of the same color. • Color-experiential states, or color appearances, are identified with certain brain processes or neurophysiological states caused by visual perception of physical colors. • Since many different physical configurations can be the ground of the same spectral reflectance capacity, color properties are, strictly speaking, highly disjunctive and idiosyncratic sets of determinate physical states.

43. scarlet red rose red magenta violet Spectral Reflectance Curves

44. Objections to Color Physicalism • If colors can exist without minds, then the phenomenal nature of color experience remains unexplained (the “hard problem” remains untouched): • Nothing about brain processes or neurophysiological states, whether characterized as physical or functional states, seems to imply that they are identical with the purely qualitative aspects of color experience: How can neural excitations be red, blue, or green? • Why does light of one frequency look this way (bright green), of another frequency, that way (pale violet)? Why does EM energy of 400-700 nanometers have a visual appearance at all? • Against disjunctivist conception of color: • Causal overdetermination: both the microphysical properties that are the disjuncts and the disjunction are the cause of a color appearance. • Explanatorily vacuous—we must appeal to the nature of subjective experience to determine the member of each disjunctive set that is identified as a determinate color; there is no way of objectively determining which physical properties are which color.

45. What Mary Doesn’t Know • In “Epiphenomenal Qualia,” Frank Jackson tells the story of a future scientist, Mary, who is kept prisoner in a black-and-white environment. She knows all the physical facts about color, but has never experienced color herself. • Does Mary come to know a new fact (one she did not previously know) when she is allowed to see a red apple? If so, then the physical facts are not all the facts. • Does she gain factual knowledge (“knowledge that”), or just new abilities (“knowledge-how”: abilities to imagine, recognize, remember)? • Physicalist response: She gains a new way (a phenomenal concept) of cognizing a fact she already knew.

46. Objective Dispositionalism • Colors are the properties of objects that account for their looking, for example, red, green, blue, etc. • Colors are really instantiated in the physical world in the form of dispositions of objects to appear colored—things of the same color share dispositions to cause the same type of color appearance. • Multiple-realizability thesis: A single, determinate color disposition may have a variety of microphysical bases or categorical grounds. • These objective dispositions may be identified with the “way an object changes the incident light,” resulting in a particular surface spectral-reflectance profile. • This physical structure or quantity of energy has a disposition to reflect/refract/emit light in particular ways that have characteristic effects on color perceivers.

47. Subjective Dispositionalism (or “Response Dispositionalism”) • Colors are ideas of secondary qualities of objects; they are not to be found in the world external to the mind (Democritus, Galileo, Descartes, Newton, Locke). [Locke: “For when White, Red, and Yellow, are all comprehended under the Genus of name Colour, it signifies no more, but such Ideas as are produced in the Mind only by the Sight…” (Essay, Bk. III, Ch. Iv, sec. 16).] • Object O is F (some color) iff O tends to bring about (phenomenal state1) ψ in (perceiver) P in (conditions) C. • O is red just in case O has the disposition to elicit a “red response” in P. • The color of something is ontologically dependent on the type of response it elicits or produces in the perceiver. • Colors are subjective, or extrinsic, properties of objects. Objects are colored only insofar as they are capable of producing color experience. 1This may be conceived as an intentional response or as a private, subjective experiential qualitative mental state/event.

48. Objections to Dispositionalism • Dispositions are not the causes of color experience; rather, the physical bases or grounds of the disposition cause the manifestations of the disposition. • The property of having a property to cause certain experiences is not itself a cause of experience. • If dispositions = colors, then • Colors are not the cause of color experience. • Since we do not see dispositions, we do not see colors. • Both of these consequences are untenable. • Color experience does not represent objects as having dispositions—it represents objects as being/having a determinate color.

49. Objections to Dispositionalism – cont. • The ontology of dispositions is itself in need of a satisfactory account. Saying that colors are dispositions to appear colored (being red =def being disposed to look red) is not much of an explanation; it flirts with circularity as in the case of explaining why something can put you to sleep by appealing to its virtus dormitiva. Response dispositionalism leads to the undesirable result of establishing two ontologically distinct types of color properties: • (1) phenomenal colors (or color qualia), conceived as “non-real” (apparent, illusory) phenomenal objects of perceivers’ experiential states; • (2) scientific, “real” colors, which are dispositions of objects (or surfaces) to elicit such experiences in perceivers. • Occam’s Razor demands that we narrow the field.

50. Motivations for Color Anti-Realism • Color science has shown that essential features of colors can be explained only by appeal to the internal organization and structure of the perceiving apparatus; color categories (division of a continuous physical range into discrete segments) and various relations mapped out in color space are solely the product of visual/neural mechanisms and processes. • Colors exhibit characteristic structural properties • Hue-similarity or hue-matching • Unitary vs. binary natures: Why are there no reddish greens or bluish yellows? • The exact color of something is revealed through perception alone (in normal conditions) [epistemic availability, revelation]. • Microstructural properties of material substances, light-reflectance/emission ratios [SPDs], or dispositions reducible to such properties, do not match up to these essential features of colors. • Since there is no acceptable physical or otherwise objectively determined candidate to identify with colors, color realism must be false.