Transcript The Color of Reality

The Color of Reality:
Ontological Perspectives on
Mind-World Relations
or
“Saving the Phenomena”
Melinda Campbell, Ph.D.
The Phenomenal World
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.
Wavelengths of the Visible Spectrum
Same objects, same illumination, same lightwavereflectance distributions: Different colors?
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.
Being Blue
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.
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.
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 minddependent “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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
The Objection from Metamers
An infinite number of distinct spectral power distributions can produce
exactly the same color appearance; hence if color is identified with physical
surface properties or light emissions, then the phenomenal content of color
experience would not be a reliable indicator of which color was causing
that color experience. Two things that appeared to be exactly the same
shade of green might be different colors.
The Objection from
Structural Properties
Colors have essential structural properties relating to hue similarities and
differences, their being binary or unitary hues, and other dimensional
features of psychological “color space” (a system of qualitative relations):
Red is more similar to magenta than to green. However, this feature has no
correlate in the physical attributes of colored objects or in the light they
reflect or emit. Magenta is binary; it is both reddish and bluish. This is not
evident in the physical correlate of magenta objects or surfaces.
Mary Redux: Blind Mary, the “Color Zombie”
• Imagine Blind Mary in a “Chinese
Room” for color.
• She is equipped with a spectrometer
and an array of color samples.
• Mary’s color matching and coloridentification abilities are the same as
that of a normal color perceiver.
• Mary has no color experience, but
there is no functional difference
between Mary and “normals.”
• Does Mary perceive color?
• The color objectivist must say yes;
however, intuition tells us no.
The Illusion/Error Theory of Color
It is granted on all sides that physical objects absorb, reflect, emit,
refract, and disperse light in a variety of ways.
Mechanisms in the eye and brain respond differentially to light of
various wavelengths. In humans, the three types of photo-pigments
in the retinal cones differ in their maximal sensitivity to light
frequencies.
“Colored objects are illusions, but not unfounded illusions.” Color
experience can be reduced to chromatic perceptual [neural] states,
but colors are not part of, or properties of any part of, the objective,
physical world (C.L. Hardin).
Understanding of these two sets of phenomena is sufficient to
explain the nature of color properties: an achromatic world is seen
as colored through the medium of chromatic visual experience.
The Illusion Theory of Color – cont.
The absorption pattern in the cones then causes patterns of excitation
and inhibition in the opponent channels further along in the visual
pathway, eventually resulting in neurophysiological states that
underlie (are?) color experiences, or phenomenal states.
On this account neither the light illuminating the object, the
object/surface itself, nor the retinal/brain state is in fact colored.
Colors are illusions; regularly occurring, scientifically explicable
phenomena. Objects only appear to be colored as a result of
projecting the phenomenal quality onto the object or surface that
plays a role in generating the visual response.
Non-Intentionalist Eliminativism
Sense-Data or “Qualia Theories”: The phenomenal character of
color experience (orange, red, etc.) is distinct from representational
content—this claim is motivated by “Twin Earth” or “Inverted
Spectrum” arguments.
We are acquainted with the intrinsic, subjective quality of our
sensory or experiential states, and this cannot be clearly identified
with any particular physical property of the object or of the neural
state objectively conceived.
The redness I see when looking at a tomato is, strictly speaking, a
property of my experiential state—of my visual field—not of the
tomato or of the light reflected from it.
On this view, the color properties of the visual field [qualia] are
projected onto external objects, but qualia are non-intentional, since
there is no feature of the external world they could represent. Color
experience is thus subject to massive error. We see the world as it is
not.
Intentionalist Eliminativism
Colors are features of representational mental states; a mental state
with the phenomenal character of, say, looking bright orange,
represents some feature or aspect of the perceived environment
that is not itself bright orange. The red, orange, and yellow colors
found in fruits and vegetables is an indicator of the presence of
beta carotene. Lycopene, also a carotenoid, contributes to the
characteristic red color seen in tomatoes. The color appearance
represents the presence of other properties, which are not colors.
The phenomenal character of the color experience (orange, red,
etc.) represents the presence of a particular SPD, or for that matter,
the microphysical substance that characteristically absorbs and
reflects light that results in that SPD. Nothing in or about the carrot
is orange, but it looks orange to us, so we project this quality onto
the object, and use it as a reliable way to recognize and locate a
useful food.
Objections to Eliminativist/Error Theories
Counterintuitive – radical departure from relatively unshakeable
commonsense beliefs. Any theory which convicts normal
perceptual experience of massive, systematic error is for that
reason hard to accept.
It is unclear why a variety of animal species would have evolved
to misperceive their environment; if there are no colors, of what
use is a visual system that creates false images? Makes color
metaphysically mysterious.
Error theory is the result of adopting an “act-object” theory of
perception—a kind of psychological atomism--which leads to a
confused picture of how perception works by focusing almost
exclusively on internal cognitive processes and ignoring the
importance of environmental factors. Perception is more properly
conceived in terms of system dynamics, i.e., complex feedback
systems.
Enactive Color Perception: Mind-World Integration
& the Reality of Subjective Experience
Color Compatibilism: A Relationalist View
Both sides of the color debate are correct in much of what they say
about color, but ultimately, we should side with the realists.
As a goal-directed action occurring in real time, color perception is a
way of transmitting information about objects and events of interest
or benefit to organisms engaging with their environment.
Colors are features of relations between subjects of experience and
the objective causes of that experience. Color is a way of seeing—a
mode of presentation of microphysical structures that interact with
light, which in turn signal the presence nutrients, useful materials,
mates and their states of fitness, illumination conditions, etc.
Seeing in color is a type of action or event—an appearance-event-through which the organism increases its chances for adaptive
success within its ecological niche. Strictly speaking, color is a
feature of this event.
Color is Subjective and Objective
Appearance-events are the instantiation of interactive relations
between perceivers and environmental conditions and situations.
Color appearances, as spatiotemporal events, are part of the real, physical
world. Appearance-events are comprised of both objective and subjective
components (environment + perceptual system):
Physical objects with reflective surfaces or light-emitting objects
(objective)
Illumination sources (sun, incandescent lights, candles, etc.) (objective)
Perceivers equipped with appropriate neurophysiological response
mechanisms (objective)
Conscious, qualitative states having color content (subjective)
In the case of color, the medium both is the message and carries the
message:
Color experience makes important features and environmental facts
salient and discriminable to the perceiver.
The phenomenal character of color experience is constrained by
biologically determined features of the perceiver as well as distal features
of the ecologically relevant external world.
Colors Are Not “In the Head”
Color experience should be understood in terms of enactive
structures—the organism’s bodily mechanisms and the physical
world in which they arise.
In order to develop a kind of “subjective realism,” we will adopt an
“embodied cognition theory” of perception, which “favors a
relational analysis that views the organism, the action it performs,
and the environment in which it performs it as inextricably linked.”
Cognition involves not only the body and sensorimotor capacities of
an organism, but also its environment: the development and precise
nature of cognition depends on all of these interacting parts.
Underlying the compatibilist view is the idea that the mind is not
entirely “in the head”: Following Gibson’s ecological theory of
direct, or active, perception, perception is an ongoing process
involving a cognitive system (the organism) that interactively
engages with its environment.
Color is a Mode of Presentation
The brain is not simply a mirror in which images or
representations of the world are displayed for some
“internal observer.” Rather, brain processes, in tune with
environmental signals and patterns, function as
representations of their causal stimuli, although strictly
speaking, they are presentations.
Colors, as appearance features, are constructed through
a series of brain processes that function to categorize
“physically disparate stimuli into perceptual equivalence
classes” (Thompson, 1995). Thus color constancy is an
adaptation contributing to our environmental fitness.
Color discourse can ambiguously refer to phenomenal
states or to physical properties of objects. In most cases,
the ambiguity is resolved by context.
Can both perceivers be right about the color of O?
If colors are relational properties, then “O is green” really
means “O is green for subject S in conditions C.”
A Problem for Color Relationalism
• For the relationalist, color ascriptions are fundamentally relational: An appearance is
necessarily and appearance of something (some object)—to a subject.
• But, if the color of a thing simply is the color it appears to be, how can anyone ever
go wrong about color judgments or ascriptions? Veridical perception depends on the
possibility of perceptual error (Cohen, 2005).
• What are the criteria for correctly perceiving the color of an object?
– Conditions of both perceiver & environment are standard.
– Perceivers can go wrong by assuming conditions are standard when they are
not.
• Error in color perception is related to the goal-directed nature of the perceptual act.
What about the possibility of “spectrum-inversion”?
What does violet/yellow/green/blue look like?
Can I ever see colors the way you see them?
Can we ever determine if there is a difference between us?
An Analogy to Colors: Meanings
As in the case of color, similar ontological worries arise about
meanings or intentional properties:
• It is evident that things (symbols, pictures, actions, speech acts,
words, etc.) have meanings. The meaning, sense, or intentionality of
human thought and behavior is of great significance to us; the
essence of human endeavor is in our creating and attributing
meaning to the world and the things in it.
• Meanings are not in any obvious way physical properties; they seem
to exist, but where or how?
• If meanings are “in the head,” are they in some sense identical with
some neural or brain state? Just as in the case of color-experiential
states, where nothing in the neural hardware or brain chemistry
itself seems to be colored, nothing about a brain state that is a
conferring or understanding of meaning itself reveals its intentional
contents.
Modes of Presentation: Meanings / Colors
Meanings:
Conceptual connection between
ψm  Фm , and πm instantiates
ψm
so that ψm / πm comes to stand for
or represent Фm
[where ψm is a mental image,
memory, etc., πm is a neural
state, and Фm is some physical
mark or object ].
Color Appearances:
Perceptual connection between ψc
 Фc , and πc instantiates ψc
so that ψc / πc comes to stand for or
represent Фc
[where ψc is a qualitative character,
πc is a neural state, and Фc is
some physical surface or light
reflectance/emission ratio].
We attribute meaning to Фm , and
color to Фc . Because meanings
are relative to intentional agents,
ascriptions of meaning to objects
should be understood
relationally, just as in the case of
color ascriptions.
Modes of Presentation:
Pictures/Colors
• Physical objects (neurophysical states)
–
–
–
–
Ink marks on paper
Paint on canvas,
Photographs
Liquid crystal displays
• Representational Media (appearances*)
– Words, linguistic and numeric symbols
– Pictures, portraits
– Images, arrays of colored shapes
• Intentional object (matter/energy/reflectances)
– Causally linked to representation/picture
– Correlated with representation/picture
*Colors are features of appearances—a way that brains
(nervous systems) construct displays of representational
data.
A painting or light display is a picture or image of Descartes (the
intentional object) insofar as it is causally linked to the man
himself, or to something that looks like Descartes.