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Notes on "The Evidence of the Senses"


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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

This outstanding work is less available every year without access to a major library, so I recapitulate its theses here.

Published in 1986 but originally written in the 70's in the form of Kelley's doctoral dissertation, it predates and is irrelevant to later disputes.

Major acknowledgements in order of appearance are Ayn Rand, Leonard Peikoff, Allan Gotthelf, Fred Miller, Harry Binswanger, Aaron Ben Zeev, Roger Donway, Richard Rorty.

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Chapter 1 Primacy of Existence

I. Three basic positions

Realism: direct perception of an independent reality

Representationalism: indirect perception of an independent reality

Idealism: no perception of an independent reality, we see a screen, a dream

II. Three basic perspectives

External: perception is a physical response to an environment by sense organs

Internal: perception is experience of discriminated objects and their structures and relationships

Hierarchical: perception integrates sensational forms of awareness, yet perceptions are integrated into concepts

III. Integration of the 3 basic perspectives into a coherent view is accomplished by selecting a basic position

IV. Basic Positions lie on an axis Primacy of Existence - Primacy of Consciousness

Primacy of Existence - realism in empiricism. G.E. Moore, Russell

Primacy of Consciousness - idealism. Kant

Representationalism lies in the middle between realism and idealism, combining elements of both

Primacy issue is usually implicit and assumed, not stated up front

Descartes Representationalism

I. Metaphysical dualism

mind is a substance or entity distinct and independent of matter. metaphysical parity and equality in status

mind is consciousness

matter is extension

II. Epistemological implications

If consciousness is an intrinsic attribute of a substance this is automatically a denial that consciousness is relational, a denial that consciousness is awareness of some object outside of consciousness

Primacy of consciousness is adopted without confronting the issue squarely

III. Descartes "Cogito Ergo Sum" begs the question

Consciousness aware first of itself presumes a metaphysical dualism, a mind radically independent of reality for its contents

IV. Descartes idea of "ideas"

Ideas are both states of consciousness and objects of consciousness

Consciousness of an idea establishes no relation of consciousness to existence

'Projection analogy' mode of consciousness as projected light/object of consciousness as the image which is a cross section of the light

V. Descartes skepticism

Descartes skepticism follows because there is no necessary relation between any idea and the external world

Descartes 'evil demon' that could deceive us by putting ideas in our heads (or even all ideas) appears in the First Meditation but assumes that ideas are nonrelational to the external world, more question begging

VI. Descartes' contradiction

Descartes begins with metaphysical parity between existence and consciousness, denying primacy to either

He affirms there is a reality and truth is correspondence

He affirms ideas are independent of reality, and reality is dispensable

But the two primacy principles do not mix

If we are aware only of ideas then the external world must be inferred

But ideas are independent of the external world so there is no basis in necessity to make an inference, all conclusions are non sequitors

Therefore goodbye to the external world, primacy of consciousness and idealism win

(Descartes cheats and invokes God to establish correspondence)

Kant's Idealism

I. Origins in Locke's Representationalism

Mind is tabula rasa at birth, reality inscribes ideas upon it

Locke accepts that mind is a substance and ideas as both states and objects of consciousness

Locke's empiricism is combined with Descartes Representationalism, contradictions abound

II. Berkeley and Hume vs. Locke

Attack on the correspondence theory of truth. What kind of relation is 'correspondence'?

A. Similarity - but we would have to step outside our minds to compare ideas and objects

Berkeley on similarity - the idea of a ruler is not a foot long, similarity is metaphysically impossible

B. Causality - again we have to step outside of our minds to check the causality and validity of our ideas

Hume's skepticism was the result of retaining the correspondence theory of truth as a standard while insisting consciousness was a thing in itself independent of reality and to which no relations from reality could be established.

III. Kant's Idealism

A. Kant attacked skepticism (to save religion) by discarding the correspondence theory of truth or any relations to reality

Kant maintains Descartes metaphysical dualism

....phenomenal world - the appearances we see

....noumenal world - things in themselves, unknowable in principle

Noumenal world is irrelevant to epistemology, truth, justification

Kant's single legitimate philosophical innovation was insisting consciousness had an identity

Kant uses the fact that consciousness has an identity to disqualify it from mirroring or conforming to reality. All we know are appearances and appearances are in us i.e. subjective.

B. Reason

Descartes hoped intellect and reason could pierce the "veil of perception"

Hume showed the attempt always failed.

Kant showed the attempt must fail.

C. Kant's theory of truth

a coherence or self-consistency standard

The identity of consciousness is a structure of categories which exists a priori to encountering the noumenal world ("a manifold of unrelated sensations").

Space, time, substance, causality are categories that exist only in the mentally organized world of appearances and form no basis for drawing conclusions about things in themselves.

Kantian objectivity is universal agreement among subjects, intersubjectivity.

Consciousness creates its own contents and judges them by internal standards.

This is a consistent commitment to primacy of consciousness.

D. Kant is self-refuting

Kant's principle that the identity of consciousness distorts knowledge applies to self-knowledge. Consciousness 'in itself' is noumenal, our theories about it are phenomenal, there is no way to relate the two.

Primacy of Existence

I. Primacy vs. Primacy Points of dispute in understanding the subject-object relation

A. awareness is nonconstitutive vs. awareness is constitutive

B. truth as correspondence vs. truth as coherence

C. consciousness as noncreative vs. consciousness creates its own contents

D. awareness is essentially outward looking vs. self-awareness is an axiomatic prior certainty

II. Primacy of Existence cannot be proven

A. Proof cannot begin by premising facts external to consciousness because that begs the question

B. Proof cannot begin by premising facts about consciousness as that contradicts the thesis that facts external to consciousness must be known first before awareness of awareness is possible

C. There are no other kinds of premises

D. Primacy of Existence cannot be a conclusion

E. "P of E" is self-evident not arbitrary or an act of faith

F. "P of E" is axiomatic because existence is implicit in any and all instances of awareness, any attempt to deny it affirms it

G. The third person external perspective when used to explain consciousness is implicitly a primacy of existence perspective.

III. Causality and Consciousness

"We can make sense of the idea of explaining experience only by stepping outside of it (and taking with us the category of causality)." - Kelley

"Experience requires a mechanism to explain it only if one makes the assumption, not warranted by experience itself, that experience must have emerged from a manifold of unrelated sensations" - Kelley paraphrasing Richard Rorty

A. In the internal first person perspective consciousness does not perceive the causality of consciousness. Perceive a tree not a mechanism of vision. The means of perception and the means of conception both function below awareness.

B. In the external third person perspective an object in a perceptual field sets in motion a causal sequence culminating in awareness of the object.

C. Philosophers have resisted causality reaching consciousness by insisting on one or more of the following:

(1) consciousness is not an existent so not causal

(2) consciousness is identical with the causal, i.e. behaviorism or determinism which denies or ignores consciousness

(3) causality ends where consciousness begins - we perceive the end of a causal chain - a type of representationalism

D. The False Demand for Diaphanousness

Philosophers have assumed or demanded that the invisibilty and diaphanousness of the means of perception in the first person perpective should carry over to the third person perspective.

Epistemologists have assumed how consciousness must function then treat as a an open question whether it can live up to the model.

Realist nonconstitutive consciousness becomes an Idealist demand for a diaphanous consciousness with no means of consciousness.

Language issues. "mirror of nature", reflection, "veil of perception" etc.

Two arguments consciousness is creative and Realism false:

possibility of error - Descartes - a demand for infallibility

demand for diaphanousness - consciousness has identity therefore perception can't work

E. Historical failures in Realism

"If consciousness has an identity of its own, it cannot grasp the identities of things external."

Idealists affirm the antecedent, therefore the consequent.

Realists have denied the consequent, therefore the antecedent.

Realist denials that consciousness has identity:

(1) absurd denials of perceptual relativity - The New Realist movement, Holt 1912

(2) insistence that classificatory hierarchies are metaphysical hierarchies - i.e. varieties of intrinsicism

F. Ayn Rand's Objectivism as a successful Realism

Rand insists consciousness has identity and explicitly rejects the diaphanous model of perception

Objects and the means of perception together are a perceptual form, but this form is not an inner object of awareness it is a means of perception, not an object an action.

The object of the action of awareness is thus the thing itself.

Rand coherently integrates the three basic perspectives

(1) Internal perspective is our primary and only direct means of knowledge about consciousness. Consciousness is not creative from that perspective.

(2) External perspective studies the operation of the senses as features of the external world. The determinate response of the senses confirms the noncreative nature of consciousness.

(3) Hierarchically, we must know about the things in the world before inferring about our means of perceiving them.

ex. We must know railroad tracks do not really converge in the distance before wondering about why it appears that they do

ex. We must know the stick is not bent before wondering why it appears to be bent when partly submerged in water.

Therefore by hierarchy no claim that consciousness can create its own contents is possible, the claim itself depends upon a prior grasp of the external world to be intelligible (and implicitly the 3rd person perspective).

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I hear Objectivists state that by attempting to deny the three axioms, one is unintentionally affirming them; namely, they cannot be disproven.

Can anyone provide information as to why this is so? For example, if one denies the primacy of existence, how is he implicitly confirming the axiom?

Edited by Nicko0301
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I hear Objectivists state that by attempting to deny the three axioms, one is unintentionally affirming them; namely, they cannot be disproven.

Can anyone provide information as to why this is so? For example, if one denies the primacy of existence, how is he implicitly confirming the axiom?

By speaking.

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Can anyone provide information as to why this is so? For example, if one denies the primacy of existence, how is he implicitly confirming the axiom?

I wouldn't say 'affirming' so much as 'implicitly relying upon'. For example, if one denies the primacy of existence, one is saying that it is contradicted by the facts. But what are facts? Aspects of reality, i.e. things that exist.

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All arguements against the axioms are self refuting and also validates them. How can you put forth an arguement against existence? And with what tools would you argue it with? Logic? Logic is based on reality, and states that A=A. You cant simulatneously persue logical argumentation while denying the priciples that is is derived from. The reason that the axioms can not be 'unproven' is because what is proof without an independent reality in which the proofs relate. How do you prove consciousness? By means of unconsciousness? How do you even tell the difference between the proved and unproved without admitting identity? Asking one to prove existence, consciousness and identity literally translates to "Prove that proof is proveable." George Smith wrote eloquently:

"Like all skeptics, you seem to think that you can assume as true the very thing you are trying to disprove, and you attempt to skirt this problem by stipulating that you are diong so for practical purposes becasue we make these assumptions in everyday life. You claim that, as a philosopher, you have discovered reasons to doubt the validity of sense perception. My point is this: regardless of whether you call your use of language 'practical' or whatever, by attempting to communicate you commit yourself to a certain philsophic context-namely, the context that makes communication possible. Once you are working within this context, it is completly irrational to turn around and declare that the foundation of that context are rationally unfounded. If the premise that our senses give us accurate knowledge of reality has no basis in reason, then any arguement that occurs within that context has no basis in reason either-which includes your arguement." - Atheism: C.A.G.

Dr. Peikoff showed how the idea behind denial in this context is disagreement. However, for the sake of the arguement, he postulates to the denier that there is no such thing as disagreement, everyone believes the same thing. When the skeptic replies that this is obsurd and that he disagrees with many different people. The question is, by starting off on the assumtion that there is no reality and therefore no subject matter, what is there to disagree about? Nothing exists. Or maybe we are both right at the same time. No?

You can not speak unequivically about consciousness without the primacy of existence. To talk about non-conscoiusness in terms of consciousness. is a blatant contradiction. To deny or assent to anything is to conclude, therefore your implicitly acting on the assupmtion that your awareness is valid and that your are conscious. There is no I or mind without it. You can't use it in the attempt to deny it. Simple logical fallacy when the conclusion denies the premises. The same goes for all Objectivist axioms.

Hope this helps

Edited by LogicsSon
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All arguements against the axioms are self refuting and also validates them. How can you put forth an arguement against existence? And with what tools would you argue it with? Logic? Logic is based on reality, and states that A=A. You cant simulatneously persue logical argumentation while denying the priciples that is is derived from. The reason that the axioms can not be 'unproven' is because what is proof without an independent reality in which the proofs relate. How do you prove consciousness? By means of unconsciousness? How do you even tell the difference between the proved and unproved without admitting identity? Asking one to prove existence, consciousness and identity literally translates to "Prove that proof is proveable." George Smith wrote eloquently:

"Like all skeptics, you seem to think that you can assume as true the very thing you are trying to disprove, and you attempt to skirt this problem by stipulating that you are diong so for practical purposes becasue we make these assumptions in everyday life. You claim that, as a philosopher, you have discovered reasons to doubt the validity of sense perception. My point is this: regardless of whether you call your use of language 'practical' or whatever, by attempting to communicate you commit yourself to a certain philsophic context-namely, the context that makes communication possible. Once you are working within this context, it is completly irrational to turn around and declare that the foundation of that context are rationally unfounded. If the premise that our senses give us accurate knowledge of reality has no basis in reason, then any arguement that occurs within that context has no basis in reason either-which includes your arguement." - Atheism: C.A.G.

Dr. Peikoff showed how the idea behind denial in this context is disagreement. However, for the sake of the arguement, he postulates to the denier that there is no such thing as disagreement, everyone believes the same thing. When the skeptic replies that this is obsurd and that he disagrees with many different people. The question is, by starting off on the assumtion that there is no reality and therefore no subject matter, what is there to disagree about? Nothing exists. Or maybe we are both right at the same time. No?

You can not speak unequivically about consciousness without the primacy of existence. To talk about non-conscoiusness in terms of consciousness. is a blatant contradiction. To deny or assent to anything is to conclude, therefore your implicitly acting on the assupmtion that your awareness is valid and that your are conscious. There is no I or mind without it. You can't use it in the attempt to deny it. Simple logical fallacy when the conclusion denies the premises. The same goes for all Objectivist axioms.

Hope this helps

Thank you very much for illuminating this subject for me. I unfortunately have been tainted by the influence of Skepticism (it's an old habit). That is why I am so attracted to Objectivism: because it is the only rational philosophic system I have encountered that assuages my sometimes baseless skepticism. I owe a great deal to Miss Rand in this regard. I have yet to read only Atlas Shrugged, The Fountainhead, The Virtue of Selfishness, and For the New Intellectual; so I do not possess a grasp of the more subtle aspects of Objectivism (namely, concept formation).

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are not reproduced here.

Chapter 2 Sensation and Perception

This chapter is about the the two theories of the relationship between sensation and perception.

I. Description of Perception and Sensation

A. Perception is of entities, entities in an extended sense. We perceive objects, but also shadows and smoke, sounds and smells. The percept stands out as a unit apart from its background. "Figure-ground" effect in vision, a similar effect applies recognizing sounds.

{Lexicon entry on entity} {This thread contains a discussion about why anyone would ever complicate the simple idea of an entity with primary and extended senses.}

B. Perception is also simultaneously of an attribute in a particular degree. Identities are grasped by means of their identities.

C. Discriminating objects requires a great deal of integration.

visual discrimination - integration of all the contours of the shape.

tactile discrimination - integration of all the positions, pressures and textures of the fingers

integration over time - perceiving a melody or a motion, discriminating a weight by lifting it, shifting it from hand to hand

integration between modalities - hear a noise, turn to see the source, reach out to grasp it.

D. Sensation is unintegrated awareness of an attribute apart from and without awareness of an entity.

E. True sensations are rare - examples hard to find

sensory damage or atrophy ex: the chaotic field presented to the blind when sight is surgically restored

severely impoverished stimuli ex: flashes or points of light, points of pressure on the skin, tones of single frequency

F. Sensations are more primitive forms of awareness than perceptions

G. Merely isolating an attribute of a perceived object by selective attention does not produce a sensation.

H. Sensations are momentary experiences.

J. Sensations-Perceptions describe a continuum, a color patch has a border, a smell is comparatively more like a sensation than is a visual object.

II. The Theory of Direct Perception ("the theses to be defended")

A. Perception is the normal mode of experience

B. Sensations are unusual, almost never experienced

C. Common cause: Both result from same sensory system

D. Relativity: A stimulus can result in a percept in one person and a sensation in another

E. Unitary product, a percept is not composed of sensations as real constituents

F. Direct: Perceptual awareness gives entities directly because perceptual integration is physiological, not conscious association, inference, hypotheses, calculation or computation

III. Sensationalism

A. Sensations are direct Only sensations of individual qualities are given

B. Percepts are derived from sensations and composed of them

C. Perceptual derivation is cognitive, logical, interpretive, or computational i.e. by or within consciousness

D. Developmental claim: infants deal with sensations then learn to perceive and automatize, hiding from us the process of perceiving

The developmental claim never came from examining infants, it was the result of a prior commitment to sensationalism.

Ex. the automatization claim could just as easily be replaced with another developmental claim, a physiological maturation takes place

Ex. infants can track with their eyes virtually from birth

Ex. learning to perceive is incrementally improving discrimination, not discovering fruitful combinations of sensation

Three Versions of Sensationalism

I. Sensations as Simple Ideas

A. Locke and Hume relying on the Representationalist model distinguished between simple and complex ideas.

Simple ideas - ideas of individual qualities are the given

Complex ideas - ideas produced by compounding simple ideas

B. Kant followed the script by having a "manifold of sensations" vs. the forms of perception and the categories

C. Locke's argument and its difficulties

1. Ideas are representational, have relationships to each other due to their content

2. Sensory ideas are caused by external objects and are given

3. Simple ideas are given and their content is not analyzable into further parts

4. Concludes sensory ideas are simple because they are given; but this does not follow

5. His examples are consistent with the unstated conclusion ideas of individual qualities are simple in the sense of given because they are simple in the sense of unanalyzable; this is equivocation

6. Speculation: there may have been an unnamed principle at work

Scientific reductionism may have inspired the principle that the mind can only analyze what it had already synthesized. Kant wrote it down:

"For where the understanding has not previously combined, it cannot dissolve, since only as having been combined by the understanding can anything that allows of analysis be given to the faculty of representation."

Sensationalism applies this principle, but the principle is unproven. By a proper appeal to hierarchy, a reason for rejecting sensationalism would be a reason for rejecting the principle. The distinction between simple and complex ideas fails to be a basis for sensationalism without this principle to relate them.

II. Sensations as Appearances

A. Hume and the empiricists, and modern sense-data theorists claim perceptual appearance can be analyzed as a series of sensations

B. Argument for: "the two perspectives" argument

1. There are perceptual constancies, the grasp of an entity's underlying constant size, shape, color even as point of view and illumination changes.

2. There are appearances, the projections of color patches onto a 2-dimensional field. "Reductive focus" There, size does vary with distance, round things are ellipses when viewed at an angle, color changes with illumination etc...

3. The constancies are inferred from the appearances.

C. Refutation:

1. Both perspectives are valid, both seem equally direct, experiments show people can shift between them at will

2. The hierarchy relation from appearances to constancies evaporates under scrutiny:

a) it is simply asserted

B) it does not apply to touch, where there are not two perspectives on the object

c) reductive focus is learned after the normal focus; babies see depth and objects not projected features; experiments with Indians and Africans show reductive focus is more common in the West so it is learned, and most people have difficulty drawing in perspective without specific training.

III. Sensations as Receptor Functions

A. Generally: Certain features of the object cannot be given because they are not present in the stimulus.

B. Argument for:

1) Locke: "The idea we have of external objects and their grandeur being still proportioned to the bigness of the area, on the bottom of our eyes, that is affected by the rays which paint the image there."

2) Berkeley: "... distance, itself and immediately, cannot be seen. For distance being a line directed end-wise to the eye, it projects only one point in the fund of the eye, which point remains invariably the same, whether the line be longer or shorter."

3) Helmholtz:

Sensory receptor cells transform the energy impinging on them into nerve impulses. But there are no cells that respond to shape, size or texture.

Sensations are defined as correlates of receptor responses, and perception then is inference or information processing on this source material.

A percept is a conclusion, "... we really have here the same kind of mental operation as that involved in conclusions usually recognized as such."

Example: the 'lightness' constancy whereby coal is still perceived as black in full sunlight, and paper as white in dim illumination, but the coal may be reflecting more light than the paper.

Helmholtz claims the nervous system takes into account general illumination levels and solves the reflectance equation for the perceived object.

C. Refutations:

1) Helmholtz does the math on depth perception, previously explained as retinal disparity. He calculates the disparity at the point of focus would have to be 20-30 times greater than it is to perceive a minimum double image. The required sensation does not exist.

2) Perceptual inferences are automatic and irreversible, unlike conscious inferences. Being informed about an illusion does not dispel the illusion.

3) Perceivers usually do not have the knowledge required for a perception. Geometric optics is required to solve for distance in the stereoscopic vision problem, but everyone has depth perception without schooling.

4) Interpreting sensations "in light of past experiences" leads to a regress problem solved by invoking some innate knowledge. Helmholtz rejected nativism in general but found himself forced to admit the Kantian category of causality as an a priori certainty. Innate knowledge was rejected in chapter 1.

Detection vs. Computation

The facts of physiology, the retinal image, receptor function cells, & neural mechanisms are established by experiment. Interpretations and judgments of what is given and what is inferred rest on philosophical premises.

I. Two markers of inference as historically assumed

A. If what is discriminated could not possibly be present to a perceiver.

B. If discrimination had been learned it must involve inference.

II. Learning indicates nothing

Interpretation - moving from sign to significate without necessity (memory, empathy, etc..)

Interpretation can be learned ex. intentions of other drivers from car motion and signals, psychological states from facial expressions, meaning from words.

Learned perceptual discrimination is based on a perceived attribute. If the attribute is perceived directly in any degree an improved discrimination is also direct.

The learning marker adds nothing, the inference or interpretation issue depends upon A. "If what is discriminated could not possibly be present to a perceiver."

III. Directness

A. There must be something in the stimulus specific to the attribute discriminated. The physical process of perception must preserve the specificity of what is discriminated.

B. There is no reason to limit a relevant stimulus feature to what an individual receptor might respond to.

C. A direct mode of awareness cannot mean unmediated by any causal process, that would be the diaphanous demand.

D. The opposite of a direct mode of awareness cannot mean acausal, but volitional as opposed to deterministic, of consciousness opposed to the unconscious.

E. No discovery about the causal, deterministic, unconscious processes of perception can transform direct perception to indirect perception.

F. James J. Gibson

Energy at a single point on a receptor surface varies simply with wavelength and intensity. energy across an array is very rich with information, filled with similarities, differences, patterns.

"A great many properties of the array are lawfully or regularly variant with change of observation point, and this means that in each case a property defined by the law is invariant."

ex. Distance -

False version - "line directed end-wise to the eye"

Real version - A surface stretching from near to far projects onto the retina top to bottom. A constant surface texture projects more densely the further away it is. The invariant property of texture is perceived to vary regularly with perceived distance.

We do not perceive invariants 'in themselves' we perceive objects.

IV. Three sources of assumptions that sensory stimuli underspecify the objects we think we perceive.

A. Kantian model explained by Helmholtz

1) the Kantian model of consciousness demands a diaphanous form of awareness

2) label receptor cells as 'passive' then label all neural processing that comes after individual receptor cell responses as 'active', then equivocate this with consciousness 'actively' constituting its own contents.

B. Representationalist assumptions

1) Perception understood as reproduction in miniature so that the final product, an idea, can resemble the object. Of course the retinal image is 2D and does not resemble the object in important ways, hence the assumption that the brain 'fixes up' the image.

2) There are cases of impoverished stimuli where the perceptual apparatus does seem to fill in the gaps, but assuming that happens in the normal case is equivalent to asserting all stimuli are impoverished. Refuted by the considerations of chapter 1.

C. Computational analogy

1) Physiological processes are regarded as information flows that are transformed, integrated, processed, stored. Analogy is made to the computer.

2) An analogy cannot be taken literally. Computers are artifacts, neurons have no programmers. Bits in a computer truly are representational, their meanings are assigned by programmers. Neural states are not descriptions of anything.

"If we perceive X by means of Y, we must really only be perceiving Y and inferring X." But this is diaphonousness again.

Some computational theorists raise the question of how the general problem of consciousness arises out of physiology. That is a genuine problem but treating perceptual awareness as conclusions of premises merely pushes back the real question by one layer in the wrong direction, how are the premises then assigned meaning and content?

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

I should have put this in the first post, but better late than never.

Table of Contents

Ch. 1 Primacy of Existence pp. 7-43

Explains the implicit and usually merely assumed metaphysical basis of Idealism, Representationalism, and Realism.

Ch. 2 Sensation and Perception pp. 44-80

The relationship of sensation and perception is explained. The theses of Direct Perception is defended against the alternative of Sensationalism, the doctrine that sensations are the given and perceptions are reconstructions of reality.

Ch. 3 Sensory Qualities pp. 81-120

Considers the distinction between an external object and its appearance. Color, Form-Object, and Primary-Secondary Quality distinctions are discussed.

Ch. 4 Representationalism pp. 121-142

The Representationalist pattern of argument in full is laid bare to better recognize the multiple forms in which it appears and influences theories of perception.

Ch. 5 The Nature of Perception pp. 143-174

Perception is defined as "the direct awareness of discriminated entities by means of patterns of energy absorption by sense receptors." Each element of the definition is explained and defended.

Ch. 6 Foundations and Nebulas pp. 177-207

Realist perception provides non-propositional, non-inferential justification of knowledge.

Ch. 7 Perceptual Judgments pp. 208-257

Distinguishing the conceptual identification of what is perceived from the percept.

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  • 3 weeks later...

Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are not reproduced here.

Chapter 3 Sensory Qualities

Perception and appearance are two perspectives on the subject-object relation, perception from the subject's perspective and appearance from the object's perspective. The twin problems are that appearances can vary when the object does not, and perceptions can vary when the object does not.

Perceptual relativity has been a central problem. Appearance has been turned into a separate object of awareness, blocking direct (as in diaphanous) knowledge of the external world and constituting a "veil of perception".

Perceptual relativity is real. Contrary to A. J. Ayer it is not mere linguistic confusion, it is not delusive when a distant object appears smaller than it really is. The philosophical interpretation of the fact of perceptual relativity by the diaphanous standard causes word choices such as 'delusive' to describe appearances.

'Appears' (and 'looks', 'sounds' etc.) can sometimes refer to an inclination to believe or judge some proposition about the object.

Some philosophers have asserted that appearances are always and only inclinations to believe propositions, simply evading the actual phenomenon in order to also avoid the representationalism of sense-data and the veil of perception. Evasion is not reasonable.

Other philosophers have claimed all awareness is conceptual, and that perception must be analyzed in propositional terms. This is dealt with in Ch. 6.

Form and Object

I. Perceptual Relativity

A. Appearance is the joint product of the object and the means of perception. But a percept is a unity, it is not possible to distinguish between the two causes because there are not two things in the field of awareness, the thing itself and its' appearance.

B. Reductive focus on appearance can isolate alternate relations:

Similarity when objects are not: distant tree & a thumb at arm's length

Difference when objects are not: distant perspectives on the same object, walking around a box

Similarity perceived as differences: two white papers, one in sunlight and one in shade

Knowledge of the objects must come first, only then can we notice other factors that cause perceptual relativity.

II. Perceptual Form

Definition of Perceptual Form - "those aspects of the way an object appears which are determined by he manner in which our senses respond to the object in the particular conditions at hand."

The form will refer to the relative aspects of appearance. The concept of perceptual form was originated by Ayn Rand.

A. First person perspective on Perceptual Form

Some relationships among objects are, in virtue of their shapes, variable while others are not. Do not say "shape is a form". Do not reify form.

B. Third person perspective on Perceptual Form

Some forms are due to the nature of our perceptual physiology. This is a deeper relativity, it cannot be noticed 'from the inside', it requires a causal, scientific study of perception.

C. Perceptual Forms are not experienced in isolation

1) Selective attention isolates forms, and the different forms have a unity among them due to the object perceived.

2) Constancy phenomena are due to the unity among the transformations in appearances, themselves due to invariants in the stimulus array as per J.J. Gibson. There is not a shifting and arbitrary haze of appearances floating between the subject and object but a regularity.

D. Perceptual Illusion

Constancy mechanisms function properly within a range of conditions called 'normal'. Abnormal conditions cause normally invariant aspects of form to vary.

A straight stick perceived to be bent when half in water is perceived as straight but in an unusual form. (Only a straight stick would appear bent at that particular angle.)

E. Form is not subjective in the sense of arbitrary

1) Form is not 'in the mind'. We perceive objects not appearances, and it is the objects the define the difference between 'out' and 'in'.

2) Forms are relational, and relational features do not have locations in one of the related objects. Mass is intrinsic, but the relation weight is not.

3) Privacy of appearances or the 'privileged access' problem arises from the subject constituting the perceptual system producing an appearance. In order for a perceptual form to be perceived by an external observer it would have to be reified as a separate perceivable thing, creating a form of a form. But the thing does not exist, therefore it does not exist in a place and is not a mental object.

F. Form is not an object

Rejecting diaphanous perception necessitates perceptual relativity, the product of a non-diaphanous means of perception. Form is an aspect of the means therefore not a separate object of perception.

G. The same object and same attributes can be perceived in different forms

- A straight stick in air and half in water

- The 'common sensibles' - size can be perceived by sight and by touch.

- No form is more or less right or valid than another.

- Perceivers with different sense organs might form different concepts based on different perceived sets of similarities and differences but they would perceive the same objective world and form the same scientific abstractions.


I. Facts of Color

A. Physiological and Physics facts

1) Light is the stimulus for color vision. Light is altered by the surface reflectance properties of opaque objects.

White is high reflectance at all wavelengths.

Black is low reflectance at all wavelengths.

Colors are due to a mixture of reflectance properties at different wavelengths.

2) Reflectance properties are due to the atomic structure of materials, in particular their electron arrangements.

3) The retina has three light sensitive pigments which are segregated into 'cones'. Each pigment absorbs some light at all wavelengths and each has a different wavelength where absorption is maximum. Each wavelength impinging upon the retina creates a three-part response from the cones. The three-part response from a single wavelength stimulus can be indistinguishable from a properly proportioned mixture of three different wavelengths.

4) Neurological output of the cones is input to an 'opponent process'. There is a 'rest' level of neurological activity which is then increased or decreased by the input.

White-black opponent system receives input from all 3 types of cones, all changing the output the same way.

Red-green opponent system receives input from 2 types of cones, one increasing and one decreasing neural activity.

Blue-yellow opponent system receives input from 2 types of cones, reusing the long wavelength cone type, one increasing and one decreasing neural activity.

All colors are a mixture of 6 primary colors red, yellow, green, blue, white, black.

Test subjects agree well on the wavelengths of the pure hues: blue 465 nm, green 505 nm, yellow 575 nm.

Nothing about these hues is special, 505 nm is unique because the blue-yellow system has a response zero there.

5) Reflectance properties are not colors. Colors do not exist in objects apart from perceivers, there are no intrinsic colors.

6) There is no property in objects that correlates with every experience of a certain color. Reflection, refraction and diffraction are jointly disjunctive in material properties, and any single wavelength has a set of three other wavelengths that duplicate its appearance.

7) Color is a relational property not located in the mind or the object.

B. Psychological facts of color, the perspective of consciousness

1) The Optical Society of America names 5 modes of color vision:

film color - light from a pinhole in an opaque screen which varies in color and brightness with the concealed scene. No entity or surface is perceived, most like a sensation.

illuminant color - color of a light source

illumination color - color of scattered environmental light

volume color - color of a transparent or translucent object

surface color - color of an object's surface. This is the color constancy. It is the result of illumination and contrast adaptations, and locating an object in 3-dimensional space having a slant, shape, texture, distance. Color and depth vision are aspects of a single integrated awareness of objects.

2) Color is experienced as external.

3) Color is located at the place of what the subject discriminates; even film color has at least a direction.

II. Philosophy of Color

A. Contradiction

The diaphanous model of perception can only interpret the physical and psychological facts of color as contradictory, compelling one to pick a side.

Naive realism says we perceive objects independent of consciousness and denies perceptual relativity. Favors psychological facts over the physical facts.

Kantian subjectivism expects perceptual distortion so favors the physical facts over the psychological facts.

(Kantians are frustrated naive realists retreating to inner representations which can be perceived diaphanously.)

B. Non-Contradiction

1) Physicists and perceivers do not contradict on whether color is relational or non-relational because they do not speak to the same issue.

A scientist has nothing to say about the awareness of color as experienced in consciousness, he can't get there to examine it.

A perceiver has nothing to say about the process of perceiving, he can't escape from behind his own senses to perceive his means of perceiving. Color as a 'proper sensible' has only one way of being perceived, so no comparison with alternate means of perception is possible.

2) Sense-data theory is often introduced by insisting that when we see red then there must be an actual red particular having red as an intrinsic attribute. Sense-data theorists justify this claim with an ostensive appeal, to direct inspection of experience. But whether color is relational or intrinsic is not perceived by the subject and is not even perceivable by the subject. This ostensive appeal is invalid.

3) The objection "One cannot notice a relational property without noticing the relation upon which it rests" is not true in general. It is true for relations such as "to the left of" but not for weight or color.

C. Integration

In surface color vision the object's atomic structure causes a set of reflectance properties that the visual system responds to and discriminates. How an object appears is partly determined by the visual system, but it is the object that appears. Reflectance properties are perceived as colors of the object because there is no perceiving the means of perception. The subject's locating of color at the object is both inevitable and correctly placed, for it is the reflectance properties that are discriminated while the means of perception are impossible to discriminate.

We do not see colorless atoms, and some have counted that as a problem. They deny we see atomic structure as color, on the grounds of simple inspection that atomic structure does not look like color. But there is no 'right way' for something to look abstracted away from a specific means of perception, the only basis for that assertion is diaphanousness.

D. Color as Perceptual Form

The variable aspects of experienced color are perceptual forms. Examples: illumination changes, dark adaptation, etc.

Color itself, the color qualia, are also perceptual forms even though the relativity there is hidden from direct inspection.

Forms are not in the mind, and color is not in the mind.

Forms are not separate objects of awareness, and color is not a separate object of awareness.

Forms are relative, and color is relative. Examples: synthesia, some forms color blindness that apparently result from atypical opponent system connections,

Primary and Secondary Qualities

Locke distinguished primary and secondary qualities. There is a basis for the distinction but not the traditional one.

I. Definitions

Quality is an intrinsic attribute of an external thing.

Qualia are the forms in which qualities are perceived.

Primary quality - shape, size, position, motion, number

Secondary quality - reflectance properties (color), kinetic energy of molecules (warmth/coolness), etc.

Quantitative dimensions in the appearance of primary qualities are perceptual forms.

Quantitative dimensions and the qualia themselves in the appearance of secondary qualities are perceptual forms. Secondary qualities have a greater degree of perceptual relativity compared to primary qualities.

II. Problems

A. Locke claimed ideas of primary qualities resembled the attributes they corresponded to while secondary qualities did not.

The presupposes representationalism with ideas as inner objects that can be similar to external objects.

This presupposes diaphanousness in assuming some perspective exists where shape similarity between ideas and objects can be confirmed.

This does not cope well with common sensibles. If shape as seen and shape as felt are each similar to the object, why are they not similar to each other?

B. Primary-secondary quality distinction does not parallel the perception-sensation distinction because of:

Touch does not fit well. Sensations are momentary but tactile qualia - hard, slippery, cold - all require some integration over time

Sensations are not integrated, and so are not attributable to an external entity. Qualias require external objects with corresponding qualities.

III. Macroscopic-Microscopic

Primary-secondary quality distinction is really a macroscopic-microscopic distinction.

Macro qualities are borders, edges, structures across a stimulus array, etc. They are discrete and apply to a whole entity. Squares are not square all through, a large object is not large in every part.

Micro qualities are reflectance, molecular motion, molecular structure, etc. They are continuous, they exist across an extent large enough to be perceived but no particular extent and they exist throughout.

Both kinds of qualities are necessary in the perception of any object.

Primary and secondary differ in degree of relativity but not in degree of veridicality.

Conceptually the primary qualities are easy to abstract because they are common sensibles. Concepts of secondary qualities require scientific theories to grasp in abstraction away from their qualia.

The concept of perceptual form is compatible with any degree of perceptual relativity. Should scientific discoveries reveal that extension and position are not primaries but the results of some underlying energy phenomenon, then the entire perceptual experience of a spatial world would be a perceptual form. Space would still be just as real as color, and not illusory.

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Should scientific discoveries reveal that extension and position are not primaries but the results of some underlying energy phenomenon, then the entire perceptual experience of a spatial world would be a perceptual form. Space would still be just as real as color, and not illusory.

One of these days Im gonna have the time to address this idea in a manner that im satisfied with.....

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are not reproduced here.

{ My own added comments are in these curly brakets. }

Chapter 4 Representationalism

Descartes' metaphysical dualism has the epistemological consequence of separating awareness from the object of awareness. There are inner objects and outer objects, and they may be related but the relation cannot be admitted to be essential. The representationalist model of perception will be identified and argued against here.

The Representationalist Model

Two representational theories of perception will be considered to find central features common to both.

I. Sense-data Theory

We are directly (diaphanously) aware only of internal objects which are sense-data.

Sense-data can occur without physical objects as causes.

Perception occurs when a) there is awareness of the sense-data and B) the sense-data are caused by external objects.

Perception is within a genus which also includes imagination, dreams, hallucinations.

Sense-data theory is an object analysis due to its postulated internal objects.

II. Adverbial Theory

Sensory qualities are not qualities of internal objects but ways in which external objects appear.

There is no red intrinsically, only "appearing redly". (Hence 'adverbial')

From the subject's perspective "appearing redly" can also occur with no object present. This is described as "the subject is appeared to redly".

Adverbial theory is an act analysis, representationalism without an inner object.

III. Commonalities

Both are actually theories of experience not perception, due to asserting the similarity of experience with and without an external object present.

Both would agree we perceive the object when it is causally responsible for the experience of perceiving.

Both describe experience as a state of the subject.

Both have the same concept of state, a non-relational description that can occur in the absence of any object.

All contents of experience (shapes colors smells etc.) are contained within the state of the subject.

IV. Cartesian Contradiction

Regarding modes of consciousness as non-relational, as states, creates the problem of explaining the content of experiential state. Consciousness itself must in some way be red, bitter, square when those things are perceived. But yet consciousness is its own realm, it cannot be any of these things. Cartesian ideas are introduced which have dual natures as both modes of consciousness (awareness, sensing) and as representational (they can be red, bitter, square). This only reformulates the problem, it does not solve it. It is a contradiction for consciousness to both be and not be relational, and it is still a contradiction for an idea to both be and not be relational.

Sense-data theory avoids describing consciousness as red, bitter, or square by saying ideas —inner objects— are those things. But then how they are mental phenomenon at all? As objects, do sense-data have backsides, and width? Do they exist in space? The same space physical objects do? Do sense-data exist when not perceived? {These are not rhetorical questions, philosophers have taken various positions on these issues. }

Adverbial theory denies there are objects, insisting that the identities of acts of awareness are red, bitter or square. This admits consciousness itself becoming red, bitter or square. The explanation that "tasting bitter" is actually a genus/species rather than a subject/attribute relation is no good, the quality that distinguishes the species (bitterness vs. sweetness) must be an attribute of that species, so awareness of the species is still consciousness of the attribute.

V. Central Features of Representationalism

A. The state analysis

The assumption that the state of the perceiver contains within it the entirety of an experience. This follows from the assertion that any perceptual experience can occur in the absence of the object.

B. The non-cognitive relation

The difference between perception and other experiences is a non-cognitive relation between the experience and the external object. It is an extra, unnecessary factor which is non-cognitive because the experience would be the same were the relation to be absent. Two kinds of non-cognitive relations specified are causality and similarity. Non-cognitive causality notes that awareness of a cup is the result of a long causal chain including the cup manufacturer, the light bulb, the receptor cells of the eye, all of which are external. Non-cognitive causality does not explain why it is the cup that is perceived, just one step in the middle of the sequence. Non-cognitive similarity does not explain why we are only aware of particulars, and not all instances of identically manufactured cups.

Realism has no question about the relation between experience and the external object, that relation is awareness.

Realism has no difficulty explaining how the qualitative contents of experience are contained in consciousness, because those contents are reality and are not contained at all.

Arguments for Representationalism

I. Perceptual Relativity

Hume from the Inquiry: "The table which we see seems to diminish as we move further from it; but the real table, which exists independent of us, suffers no alteration. It was, therefore, nothing but its image which was present to the mind."


1) The object of immediate awareness in perception varies.

2) The external object does not vary.

3) Therefore the external object is not the object of immediate awareness in perception.


Premise 1) begs the entire question of how perceptual relativity comes about by its very vocabulary. In reifying an object of immediate awareness separate from the external object it invokes the whole representational model and the "conclusion" is a foregone conclusion.

Awareness is relational, even considered as a state it is outward directed and only takes its meaning from something not already within the subject. Perceptual relativity reveals no distinction between the external object and object of awareness.

Given objects and conditions, it is the conditions that cause variable appearances.

a. Form is distinct from awareness in the same way the object is distinct from awareness, both form and object are "out there".

b. Because form is relational it is not a state of one opposed to the other.

II. Time Lag


The causal sequence in perception takes time to occur. In the interval the object perceived could change or even be destroyed.

Therefore, the perception is a representation of what was.


There is equivocation in moving from the subject's timeframe where awareness is always in the present to the object's timeframe. It is acausal and diaphanous to demand that in a valid perception the time lags inherent in causality be circumvented.

The realist claim that the objects of perception exist is not a claim that they exist now. Veridicality can exist without simultaneity. Perception is like memory and other historical knowledge in this respect.

Bonus Metaphysical Excursion:

Time does not consist in mathematical instants. The present is understood in terms of the interval during which perceptual integration takes place.

{ Perception always occurs in the present and the time lag is a part of all perceptual forms. Time lag is relational but not perceived as such by the subject without a scientific, conceptual level investigation. Perceptual relativity does not make perception impossible.} { Braketted text is a straight forward application of what has gone before but is not in the book.}

III. Double Images

The argument:

A pencil held before can be made to appear in double image by pressing against the side of one eye with a finger. There is one pencil but two images, two representations of the pencil. Since the double images are representations, then the normal in-focus image is also a representation.


There are two eyes, each capable of producing a percept. Both percepts are valid and are of the same real external object. The two visual percepts are normally integrated together by the focusing action, but in principle are no more a proof of representationalism than are the two percepts given by the left eye in vision and the right hand by touch. A single percept is a perceptual form and so are two (or more).

IV. Hallucinations

A. Hallucinations vs. Illusions:

a. Illusions are perceptions in unusual circumstances.

b. Hallucinations are not perceptions, there is no reason to believe hallucination has anything to teach about perception. Only a prior commitment to the representationalist model leads to the insistence that hallucination can teach about perception.

B. The Argument:

1) If percepts were different from hallucinated objects, then there would be a qualitative difference in the experience.

2) There is no such qualitative difference.

3) Therefore, a percept has the same status as a hallucinated object.

4) A hallucinated object has the status of an image.

5) Therefore a percept has the status of an image.

C. Refutation:

Others have exhaustively criticized this argument. See Austin, Sense and Sensibilia, ch. V and Hirst, Problems of Perception, pp 37-45. In Summary:

Premise 1) is an assertion offered without justification.

Premise 2) is supported only by testimony of subjects having hallucinated, but the extreme malfunction of the mental faculties involved also renders judgments unreliable.

The argument begs the question. Assume for now the acceptance of 1) and 2) and the the intermediate conclusion 3). 4) is supported by common sense, but common sense also supports an alternate premise

4) "A percept has the status of an external object." Alternate 4) would lead to the conclusion

5) "A hallucinated object has the status of an external object."

The given 4) and alternate 4) are equally justified, only a prior commitment to representationalism dictates the preference.

D. Hallucinations as evidentiary:

Hallucinations are favored devices because they act as evidence for the state analysis premise, the premise that what is experienced must be contained entirely within the experiential state of the perceiver, and that an external object is superfluous. But are they? What are hallucinations?

E. What hallucinations are:

Percepts can be remembered. The object remembered is similar to the object perceived, but the experience of remembering and perceiving is dissimilar.

Imagination can create objects and entire scenes in a quasi-perceptual way. Imagination is not limited to objects as wholes, it recombines parts and attributes, colors and textures. Again the similarity is in the remembered elements while the experience is dissimilar to perception.

Memory and imagination can both be eidetic, extremely vivid. Hallucinations apparently can too. But the experiential state is still not identical to perception, it is a special form of perceptual memory and imagination where the similarity still lies in the objects and attributes not in the mode of experiencing them. Hallucination is the capacity for recalling and rearranging perceptual experiences set in motion by a cause that also prevents one from experiencing them as recalled or made-up.

F. "Imagining what a hallucination is like":

Resorting to this eliminates the value of using hallucinations as evidence. If the desired state is simply imagined, that is an assertion not an argument. And imagination is not perception.

V. Brain in a Vat, Virtual Reality, The Matrix™©, Avatar™©

{ None of these sexed up terms were in existence when the book was written. Kelley merely refers to "the device" and the argument is named "The Causal Argument" It is all the same, for all these arguments trace back to Descartes' evil demon originally. }

The Causal Argument:

Consider perception as a one way causal sequence of: object > receptors > cortex > percept.

The same perceptual experience will result so long as the last intraneural stages occur.

Postulate a device that can create the same proximate neural stimulus as an object, or a world of objects.

1) It cannot be argued that the resulting percept is radically nonperceptual—this is not a hallucination.

2) The things perceived within the device are not real, they are only simulated.

3) Therefore no percept can be trusted as real, all perception is an inner theater.


*Minor refinement — Perception is not one way, it also depends on moving, orienting, focusing, eye saccades , etc. The device must also be connected to motor neurons to simulate interaction so that the subject can explore the simulated world.

True, the subject's experiences would not be similar to what is perceived, the device and its stimuli. But representationalism is still false, percepts are never regarded as objects compared to external objects in terms of similarity and dissimilarity. Even in the normal case percepts are not similar to objects.

Perception is awareness of external objects, but realism makes no assumptions about how that works. If the simulation is as complete as postulated, there would be perception of the simulated world but it would be a perceptually relative form of perceiving the deeper reality of the memory states of the device. It does not follow that the subject's experience would be internal and unreal. What is perceived depends in part on what is there to be perceived and its interaction with our senses.

The above assumes the device stays on for a long enough time to permit exploration. If the device were rapidly switched off and on it would be difficult to predict if the subject would perceive anything at all or only a stream of sensations. The sensory systems have a finite capability to process stimuli, evolved to suit the typical ranges of a past environment.

IV. Notes on the repeating patterns of the arguments

We are offered a normal and a hypothetical case, and a premise that the normal and hypothetical percept have the same status.

Then because the hypothetical case does not involve direct perception we are invited to conclude the normal case is not direct perception either.

This can always be inverted: The normal case does involve direct perception so we can conclude from the "equal status" premise the hypothetical is also direct perception.

The symmetry of the argument exposes the bias of the advocate when one selection is made.

All the arguments require prior premises for interpretation of phenomenon. There are no local arguments to prove or disprove representationalism or realism. {The primacy of existence principle is axiomatic and is the ultimate basis of resolving the conflict.}

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are (mostly) not reproduced here.

{ My own added comments are in these curly brakets. }

Chapter 5 The Nature of Perception

The Definition of Perception


Perception is a type of awareness.

Other types of awareness are introspection (awareness of the mind) and interoception (awareness of the body). Dreams, imagination, and hallucination rely upon the perceptual system and memory and so are derivative phenomenon.

II. Differentia

There are two, means and objects.

A. Means

Perception is direct, automatic and produced by a causal sequence.

Conception is voluntary and produces indirect awareness by inference, reason and concept formation.

B. Objects

1. Scope

Perception is always limited in range to those objects present to the senses.

Conception can refer to objects not present and not perceivable.

2. Entities

Perception gives awareness of entities as concrete particulars.

Conception gives awareness of abstractions of entities.

Sensation does not give awareness of entities.

III. Definition

Perception is the direct awareness of discriminated entities by means of patterns of energy absorption by sense receptors.

(footnoted attribution: This definition is based on Robert Efron's, but substitutes 'entities' where he used 'existents'. The reference to Efron is "What is Perception?" Boston Studies in the Philosophy of Science, IV (1966-68), 147.)

The Means of Perception

Each of the elements of the definition is in turn discussed in relation to the means.

I. Energy absorption

Energy absorption must be in the definition because the range of what can be perceived is limited both by the sense receptors' ability to respond and the object's ability to create or structure an array of energy at the sense receptors. This is the crucial relationship in perception considered as a causal sequence.

II. Patterns

An undifferentiated array of energy containing no gradients would not be distinguishable from no stimulation at all. This is true for sensation as well as perception. Perception is the detection of the existence of certain patterns in the proximate stimulus. James J. Gibson first started isolating stimulus variables. D. H. Hubel and T. N. Wiesel discovered "receptive fields" of cells in the visual pathways that fired in response to the presence of certain patterns. (See "Brain Mechanisms of Vision," Scientific American, September 1979, 150-62.)

III. Discrimination

1) Perceptual forms: The concept of a perceptual form is incorporated into the definition indirectly. A specific means of perception entails perception occurs in a specific form. What is discriminated is causally dependent upon response of the perceptual system involved. Psycho-physics establishes relationships between the distance and orientation of an object and its perceived shape, wavelength and hue, frequency and pitch, intensity and loudness.

2) Perceptual specificity: Perception has a finite precision. Two objects that differ by less than the differential threshold are indistinguishable. In optimal conditions the differential threshold for color is 4 nanometers of wavelength. Smaller differential thresholds are more specific, and lead to greater perceptual specificity. Specificity is limited for every stimulus feature, changes with conditions and varies along the range of the attribute.

IV. Direct Awareness

Directness distinguishes perceptual from conceptual awareness of objects. The epistemological function of the concept of directness is to locate the given. The given is the basis of knowledge.

A. Directness is not Hierarchical - Logic is conceptual. The conclusion of an inference is indirect because it depends on prior knowledge. The content of a conclusion is necessarily determined by the argument's premises. {Indirect invokes logical hierarchy.} Perception is direct because it does not depend upon prior concepts, it is not logical but physiological. {What is direct is not logically hierarchical.}

B. Directness as Passivity - The empiricist tradition has identified the given with the passive element in experience. Consciousness has been understood as interpretive or constitutive, as active. Passive sensation has been contrasted with active perception. But consciousness is not constitutive, and attention is distinct as a cognitive process precisely because it does not interpret.

True, what can be perceived is not necessarily what will be perceived, the conscious activity of the perceiver is a factor. Degree of attention varies along a continuum from objects at the edge of the visual field to objects at the center, low steady background noises which are ignored to complex musical compositions attended to intently. Perception is also learned, as in wine tasting. A scientist and a layman may look at the same laboratory setup, and while being presented with the same visual field the scientist will perceive more. The scientist will perceive finer differences in shapes and colors, and will discriminate perceptual units where the layman will perceive only a jumble. But this applies to sensation as well, the constant stimulation of the skin by one's clothes is usually ignored thus clothing is not perceived or sensed. Attention and learned perceptual discrimination are both active, but neither are interpretive or constitutive and neither depend upon prior conceptual knowledge.

Passivity is the representationalist concept of directness as a diaphanous confrontation between mind and object with no causal connection, where the inner object is produced at the end of a causal chain. Diaphanousness must be rejected.

C. Directness as Certainty - "A subject is directly aware of a given object if he could not be mistaken in his beliefs about that object or in his belief he is aware of that object." The sense of 'could not be mistaken' employed here is Cartesian incorrigibility, a idea examined and refuted in the next chapter. A more local argument against directness as certainty is given here.

Direct perception means "X is red" or "We perceive X is red" is an infallible statement.

But if X refers to an external object then there is already perception occurring that gives us X and this adds nothing.

If X refers to an appearance then an analysis of appearances is necessary to complete the thesis. In realist theory appearance is the subject's perceptual form, but a form is a relationship not an object that can have properties such as red. Therefore this must be a representational sense-data theory of appearance as an intermediate inner object which can be red. But then for the statement "X is red" to be infallible, representational sense-data theory would have to be infallible. Representationalism is certainly not infallible, and directness as certainty does not follow.

Statements in the form "X is p" use words standing for volitionally formed concepts which cannot possibly be infallible (even when true).

The Objects of Perception

There can be questions of detail about what is the true object of perception. For example in perceiving a cool temperature by touch, is the real object of awareness the heat-energy level of the object, the rate at which heat conducts away from the skin, or the lowered energy state in the skin? The method for answering such questions follows that used for color, determine whether a subject can detect variations in an attribute while the others are held constant. This line of inquiry is about attributes and will not distinguish sensation from perception.

I. Discrimination of Entities is what distinguishes perception from sensation. Focus of attention can be on an attribute or the entity but we are aware of attributes, actions, and relationships as actions, attributes, and relationships of entities.

Perception is not a sequence of snapshots, each one a percept. Perception is an ongoing process of monitoring the environment and actively seeking stimulation.

Awareness of entities is not uniformly clear and discriminating, but modified by attention and limited by perceptual specificity.

II. Entities and Attributes - Hume's Question

We see a variety of qualities in a perceptual field and notice some of them go together. This lead's to Hume's question: "What binds the qualities together?" Nothing given perceptually binds them, so either:

1) We are guided by some past experience in what goes together. (Hume's answer) or

2) The perceiver imposes an organizing structure - a category - on the sensory manifold. (Kant's answer)

The question is invalid because it has the matter backward and does so because it assumes and employs the thesis of sensationalism. But we begin with the awareness of the whole apart from its background, then we isolate individual qualities. To selectively focus on an object and wonder why the shape and color go together, or the color and texture, is a highly conceptual perspective presupposing a great deal of prior knowledge. That perceived qualities go together is given. The real question is how does a mind come to separate them?

III. The Essence of Perceptual Discrimination is the idea of an entity.

An entity is the subject of its attributes, actions and relationships. The edge between figure and ground implies there is more to see and invites exploration. Sensations do not point beyond themselves.

An entity is the subject of change tracked over time. Motion is perceived as a single object changing its relative position, not a series of discrete states.

IV. Discriminating an Object vs. the Medium

1) Sound Do we hear the sounding object or the wavetrain? We can do either and both depending on the conditions and what is being discriminated.

Approaching footsteps are discriminated as events from a background of other noises, but events are actions of objects. A mere sound has a direction, approaching footsteps have a direction, distance, the distance is decreasing, different shoes make different sounds, the pace and gait can indicate the frame of mind of the person in the shoes.

A symphony is melodies and phrases discriminated as patterns in a wavetrain, but not considered as events, the actions of sets of lips and fingers of musicians. { If one is a musician that perspective is also available. }

2) Smell Odor is experienced as the presence of a certain quality, yet it can also be considered as a unit having an intensity, direction, distinct from other smells and changing over time, whose source is discerned by changing position. For humans the perceptual specificity of smell is low, it cannot be said that we discriminate the object that emits a smell by the smell. However, bloodhounds seem to experience scent as a physical trail with contours as clear as a bright white line.

3) Vision There are modes of color vision in which we see the light itself (film and illumination modes) and we normally see physical objects that reflect light.

4) Mirrors Objects in mirrors are discriminated as objects, the left-right reversal has no impact.

5) translucent frosted glass windows If distortion of appearance due to the glass is low enough that the contours of an object and a sense of depth at the edges is preserved then there is discrimination of objects through the glass. If all texture gradients and depth cues are eliminated then we see only the window itself with colors and shadows playing across its surface.

6) Television A borderline case. As in other representational objects (photographs, paintings, etc.), we perceive that object not what is represented. Like other instruments that extend perception (microscopes, etc.), television preserves the live causal chain that produces a sense of motion and of depth. However the two dimensional presentation evokes no sense of being able to explore so there is a certain passivity in the television experience.

Objections to the Realist Perception of Objects

Prefatory remark - on using language to describe what happens in perception.

In writing and philosophizing about perception many abstractions and words are used to describe what a perceiver does which a perceiver need not ever employ. Perceptual awareness is direct and nonconceptual but it cannot be communicated directly and nonconceptually. Constraints on writers should not be taken as constraints on perceivers.

Examples: "S perceives X" is taken to refer to direct perception while "S perceives that ..." is taken as propositional perception. "Hank perceives that the X-ray tube is in the lab" implies that Hank has available the concepts of 'x-ray tube' and 'lab' and actually used them to identify what he saw. The language used does not demonstrate that Hank would be blind to thing which is the X-ray tube or the room that is the lab if he did not have those concepts.

I. Prior concepts are necessary to perceive

The argument for this is essentially sensationalism. The given is that which is given passively. Only discrete qualities are given passively. The relation between the qualities is imposed by the perceiver. This was previously refuted, the feature of the argument highlighted here is Kant's contribution that the substance-attribute relation is a logical category, therefore awareness of substance-attribute relations must be conceptual, or a feature of our conceptual framework.

Refutation: On top of the previously refuted doctrine of sensationalism, it is simply assumed that the substance-attribute relation is not a feature of the objects themselves and cannot be directly perceived. Without that assumption there is no basis to conclude the relation is conceptual. The perception of things as things is given directly in the same way the perception of attributes is given.

Similar but different argument: "What counts as an entity in a given context depends on what we have in mind". When walking around the house, whether one sees one, four or hundreds of entities depends on whether one is counting houses, walls or bricks. Thus a perceiver cannot be said to have perceived an entity unless he has a concept of which the thing in question is an instance.

Refutation: This commits the language fallacy described in the prefatory remark. The house, the walls and the bricks are in fact all entities even though we do not treat them all as entities in the same act of attention. In regarding the wall, in perceiving it, there are internal divisions which are the brickwork. Attention does not create entities where none in fact are.

Attention does not inherently depend on a prior conceptual understanding of the things attended to. In certain teaching and learning situations one may receive a description of a thing and how to recognize it before being confronted with it, but this cannot be the general case { or nothing new could ever be discovered }. Denying this must depend on sensationalism in some form.

"How can the physical stimulation of sense-receptors give us the abstract metaphysical relation between entity and attribute, or between an entity and its changes?"

We do not perceive the abstract relation, we perceive concrete entities as unified natures. We notice similarities between perceived entities, and form concepts to identify the respects in which they are similar. There is no need for a glue to unite what we have ourselves separated. There is no actual separation between subject and its attribute, so there is no relation to be perceived. The subject-predicate structure in language reunites what was distinguished in thought and does not correspond to a perceived relationship which is given in addition to the subject and its attributes.

II. Perception of parts is somehow more direct than the perception of a whole

Perception of an entity does not require awareness of the whole entity, front and back, inside and out, through and through. Therefore we do not perceive entities directly. Two arguments have been advanced for this:

A. G. E. Moore "inkstand argument" - When one looks at an inkstand he is not aware of the inkstand itself as a three dimensional entity holding ink. At most one is aware of some entity or item corresponding to the facing surfaces. Soap bubbles seemed to give Moore pause. Moore did not state his reason but he apparently is holding that to see an object directly is to see all of it, there can be no sides or parts or aspects hidden from view.

Taken literally Moore is demanding omniscience, another appearance of the Cartesian quest for infallible knowledge. Another objection is that the object does not exist as Moore describes it, a two dimensional surface. A real surface is a three dimensional layer having an inside and backside and subject to the same problems for Moore as ascribed to the object. The two dimensional description is a special mental construct invented to fit the problem and leads to representationalism.

B. David Sanford's variation on Moore - A color expanse must be the primary object of vision because that color expanse could be present even when the entity is not, and we would be unable to distinguish the cases.

A color expanse is not an existing thing but an abstraction. A real object has a third dimension and therefore unperceived aspects. A color expanse is a special mental construct invented to fit the problem and leads to representationalism.

But suppose the argument is that a high quality hologram might be indistinguishable from the real object. So what? Two quite different things can look identical, and due to perceptual specificity they need only have a finite similarity. In this case one thing is a material object and the other is a light phenomena, a different kind of physical existent. Their indistinguishability is irrelevant to the directness of perception. { Judging they are identical could only happen after they were perceived. } What is directly perceived depends on what is there to be perceived.

C. Frank Jackson's variation - We are directly aware of some things, the facing surfaces of objects. We are not directly aware of the object as a whole because we perceive the object in virtue of the facing surface, and there could be a surface without an object. In other words, an object of direct perception is not perceived by means of something else.

A facing surface is seen because of the color expanse in the same way the whole object is seen because of the facing surface. The only difference in the two cases is that the whole entity includes parts not seen while the facing surface does not. This is same definition of directness as Moore's.

There is no asymmetry between awareness of the whole and awareness of the facing surface. It is true we see the object because we see the facing surfaces. But it is also true that we see the facing surfaces as we do because we discriminate the three dimensional object. Color constancy depends on seeing the surface as having a certain depth and slant. Perception of attributes is affected by perceptual context, and discrimination of entities is the essential structure of that context.

III. Anti-integration

These last arguments that only parts can be perceived directly are examples of denying the possibility of valid integration.

Human cognition has levels or stages, each formed from the material available at the preceding stage. Each new level of integration makes possible awareness of a new type of structure in reality that could not be grasped without it. Concepts are abstractions of patterns of similarities, where perception only gives similarities between particulars. Induction gives abstractions of patterns of action known as lawful behavior, without induction we only have separate particular acts and no law.

Integration of a new structure also alerts us to the possibility of new instances of facts that fit the new structure. Integration provides a goal for active inquiry, so we need not wait passively for reality to reveal itself.

Each form of integration goes beyond the evidence in a sense, if evidence is restricted solely to that of the previous level of cognition. There is a philosophical tradition of restricting evidence in exactly that way and denying integration. Hume argued causal laws are merely conjunctions of particular facts. Nominalists claim a concept is nothing but a tool of convenience to denote a set of particulars. It is claimed that such integrations do not and cannot give us knowledge of anything not known before, and no such integration could be justified.

Integration does occur, and it is justified by the existence of real structures in reality. Perception is the first such stage of integration. Since it is not done consciously perception is not integration of a prior mode of awareness. Perception is a neurological integration of sensory input which left unintegrated would result in sensations. The consequence at the conscious level is awareness of entities possessing qualitative identities.

Sensationalism is motivated by the denial of integration. The features that characterize perception are not given in any form at the level of sensations, and cannot be derived or deduced. Those features are given by the perceptual integration itself. The sensation of an isolated quality will not reveal that it is a quality of an entity, nor reveal that the entity has other qualities as well. Perception is a distinct mode of cognition, not a blend of sensations and concepts. Perception of entities reveals a real structure in which the qualities causing sensations exist, and the structure invites further exploration and expansion of awareness escaping the passivity of sensation.

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are (mostly) not reproduced here.

{ My own added comments are in these curly brakets. }

Chapter 6 Foundations and Nebulas

Knowledge has structure. Most knowledge is acquired and validated by inference from prior knowledge. Where does this prior knowledge come from? This chapter is about the foundationalist and coherence theories of the justification of knowledge and the realist theory of perception affects that debate.



Basic knowledge is necessary for any other kind of knowledge, for the truth of any inferential knowledge depends upon the truth of its premises.

Basic knowledge is possible. There are judgements justified without prior conceptual knowledge of other facts.

II. Coherence (Anti-Foundationalism)

Basic knowledge is not possible because justification can only occur within a vast network of background knowledge.

Basic knowledge is not necessary because the standard of justification is the coherence between a belief and its context.

As analogs of the two sides of this debates, we have "buildings, towers, or trees" vs. "nebulas, clouds, webs, or ships at sea".


The debate takes place at three levels.

A. If there is basic knowledge it is perceptual knowledge so the two sides must clash over perception.

B. Contextual and hierarchical perspectives on knowledge are both valid and do not contradict each other. Neither side can prove the other's appoach is wrong, but they try. Integrating them fully is beyond the scope of this work but a few things will be said.

C. There is a more fundamental conflict underlying the two positions on the relation between knowledge and existence. Foundationalism is consistent with "Cartesian empiricism" while cohence theory has an underlying "Linguistic Idealism".

Cartesian Empiricism and its Critics

What "Cartesian empiricism" refers to

an integration of Cartesian knowledge with an empiricist source.

acceptance of the prior certainty of consciousness

the premise that there is an indepent world that is the ultimate object and standard of truth.

Knowledge of the external world is based on prior knowledge of our own conscious states which can be known infallibly.

The conscious states in question are those involved in perceptual experience. (this is the empiricist element rejecting Descartes' doctrine of innate ideas)

Who is referred to?

Bertrand Russell, A. J. Ayers, C. I. Lewis, Roderick Chisolm.

There are difference among these thinkers but the common pattern is what is of interest here. The pattern is that perceptual judgment is the product of an inference and as an inference it requires justification.

Two theses and two motives

1. First Theses: The foundations of knowledge must be phenomenal i.e. about appearances, the are knowledge about an experiential state. The state of the subject is independent of an external object.

First motive: The representationalist theory of perception has been accepted by most empiricists.

2. Second Theses: The foundations of knowledge must be infallible in the sense of immune from any doubt, revision or qualification.

Second motive: This originates in the Cartesian desire to answer the skeptic.

The phenomenal theses

In representationalism, the given is only the experiential state itself. A Cartesian empiricist contends that the perceptual basis of knowledge is the conceptualization of the experiential content. There is no awareness of an external object until we have identified the experiential state as something which implies the presence of the external object. Russell is an exponent of the sense-data version of this, Chisolm of the adverbial version. The claim that appearance is prior to perceptual judgment presupposes the representationalist scheme of appearances.

The 'Asymmetry argument'

One can justifiably believe about appearances without being justified in a belief about external objects. BUT it is claimed,

A justified belief about an object necessarily entails justification of some belief about how that object appears.

THEREFORE, appearance is prior to judgment.


The argument assumes an adult perceiver with enough background knowledge and experience with the world to take care to note how something appears before he claims to know how it truly is. Appearances are not epistemologically prior because they rest upon this background knowledge.

Realistically the asymmetry runs in the reverse direction: one must have prior knowledge of the object before noting the appearance differs from that prior knowledge.

The infallibility theses:

The skeptic argues that because it is possible to err, any particular judgment may be in error therefore we can be certain of nothing. Descartes accepts the skeptic's criteria of certainty and so searches for knowledge which is infallible. Descartes thought the cogito statement was infallible (it is not) and the empiricists thought phenomenal knowledge was infallible.

In sensationalism appearances are 'sensory atoms' regarded as incorrigible, incorruptible, not relatable. Appearances are experiential states having no intrinsic relation to other states or an external object. A perceptual judgement merely registers the existence of the state and has no further implications requiring verification. Such a judgement is free from any danger of being corrected, revised, or qualified by later knowledge. As an isolated, incorrigible atom of knowledge it is outside of any context and so cannot possibly be contradicted. C. I. Lewis claimed his "expressive statements" could be verified completely and decisively because they implied nothing. (How a statement that implies nothing could serve in the role of a foundation of knowledge is a problem.)

Cartesian empiricism is in well-deserved disrepute. Deriving the existence of an external world as a conclusion without presupposing it in any way is doomed. The data do not support the conclusion. Cartesian empiricism is unnecessary as well. Rejecting representationalism and skepticism entirely wipes out any need or motive to assert the base of knowledge must be phenomenal or incorrigible.

Coherence Theory or Linguistic Idealism

What "Coherence Theory" is

Some have concluded that since the foundations of Cartesian empiricism are impossible, no foundations are needed at all.

Coherence can be described as a kind of epistemological idealism, holding our conceptual scheme has no support (and needs no support) from nonconceptual forms of knowledge.

Justification, evidence, truth are only issues within our conceptual scheme and cannot be questions raised about this scheme itself.

Knowledge is a social product, objectivity is coherence not correspondence.

Who is referred to?

Wittgenstein, Wilfrid Sellars, W. V. Quine, Rorty, others.

The Kantian model displaces the Cartesian model. What is Kantian about the philosophers listed is that they follow Kant's "Copernican revolution", the reinterpretation of objectivity.


Wittgenstein attacked metaphysical idealism and Cartesian dualism in favor of seeing man as a physical organism in a physical environment. Ideas, judgments, and conscious states were abandoned in favor of materialist behaviors - linguistic products such as utterances, assertions, statements. Yet this is still a form of Kantian epistemological idealism because the objects of knowledge are still in some sense constituted by the means employed in knowing them. The new sense is language dependence.

C. S. Pierce defining truth and reality

"The opinion which is fated to be ultimately agreed upon by all who investigate, is what we mean by the truth, and the object represented in this opinion is real ... Reality is independent, not necessarily of thought in general, but only of what you or I or any finite number of men may think about it ... But the reality of that which is real does depend on the real fact that investigation is destined to lead to a belief in it." C. S. Pierce Collected Papers (6 vols.; 1931-35) 5.407-408


Reference is inscrutable because we cannot describe what terms refer to without using those terms. We cannot step out from behind language and know reality diaphanously.

"Specifying the universe of a theory makes sense only relative to some background theory." Quine Ontological Relativity (1969) 54-55

This exactly parallels the idealist critique of representationalism, that we cannot know the real objects to which our ideas supposedly correspond but only the ideas.

Correspondence is held to be vacuous or unascertainable and thus nonepistemic because it occurs automatically "by definition" when the objects of knowledge are determined by our theories, and no selection from among competing theories occurs. A version of correspondence that makes it altogether independent of inquiry makes truth inaccessible. This applies to Hilary Putnam's "metaphysical realism" where "truth is supposed to be radically nonepistemic" and "Verified (in any operational sense) does not imply true ... even in the ideal limit." Hilary Putnam "Realism and Reason", Proceedings and Addresses of the American Philosophical Association, L (1977) 485.

What truth is, is "warranted ascertainability" (John Dewey) established by coherence with a network of other statements.

Quine: "Where it makes sense to apply 'true' is to a sentence couched in the terms of a given theory and seen from within the theory, complete with its posited reality." W. V. Quine Word and Object (1960) 24.


Idealism is the theory that consciousness creates or constitutes its own contents. Epistemological standards of objectivity reflect that as follows:

* materialistic metaphysics is combined with idealist epistemology by distinguishing causal and justificatory conditions for knowledge.

* knowledge causally depends upon the environment impinging upon our senses and the workings of our nervous system, producing as an effect a piece of linguistic behavior. The entire sequence falls into the province of natural science.

* Justification, meaning, truth are only questions that arise between minds when utterances are made within a social practice governed by rules.

An utterance is distinguished from other natural events only in that is a way of participating in the social practice. The truth of an utterance is determined by the rules of the practice, and the rules are not based on anything, they just are.

Richard Rorty's "epistemological behaviorism"

"Explaining rationality and epistemic authority by what society lets us say rather than the latter by the former, is the essence of what I shall call 'epistemological behaviorism'." Rorty Philosophy and the Mirror of Nature 174-178

Rules of justification which are social, mutable and pragmatic are unlike Kant's fixed categories but are nonetheless Kantian in assuming the primacy of consciousness.

Wilfred Sellars has gone furthest in applying the neo-idealist model to perceptual knowledge. The chain from external objects to perceptual statements is all causality and conditioning. He rejects A.J. Ayers' (a 'linguistic Cartesian') claim that there is a special justificatory relation between word and thing as circular, that to apply a word-thing rule of the type "red objects are to be called red" requires already knowing a thing is red, which is what was to be explained. Thus, all rules are of the 'word-thing' type. Sellars "Some Reflections on Word Games" Science, Perception and Reality 333

Wittgenstein "When we first begin to believe anything, what we believe is not a single proposition, it is a whole system of propositions. (Light dawns gradually over the whole.)" Wittgenstein On Certainty ed. G.E.M. Anscombe & von Wright (1969; rpr 1972) sec. 141

Problems in Linguistic Idealism

I. The theory makes an exception for itself. The claim that knowledge consists of conditioned responses is not itself offered as a conditioned response but as true in the sense of correspondence, the product of agents such as Wittgenstein, Sellars etc. who are free to weigh the merits of various theses and grasp truths overlooked by their opponents.

Quine argues that reference is inscrutable without doubting whether his theses is really about language. What it asserts is not compatible with the assertion of it.

II. The theory is not compatible with the knowledge used to explain and defend it.

Kant's theory depends upon the noumenal self performing certain actions, but the noumenal self was supposed to be unknowable.

In a similar relation linguistic idealism depends on a theory of human beings as objects of scientific knowledge to explain how truth and objects are dependent on our conceptual scheme, but it does not explain itself.

Linguistic idealists have claimed progress is possible, somehow. Although truth is relative to some conceptual scheme, nevertheless our conceptual scheme is prefereable to our predecessors, and our successor's will be preferable to our own. Sellars appeals to truth-as-picturing a basic singular (atomic) statement which is non-intentional. Evolutionary accounts of how beliefs, scientific theories or conceptual schemes are selected for survival value are another attempt. But if all truth is relative to prior knowledge then no form of realism is possible, no picturing statements or evolutionary theory can bridge the gap.

Linguistic idealism bases its success on criticisms of Cartesian empiricism, just as Kant defeated Hume. But both victors share the primacy of consciousness perspective of their opponents so they are not opposites but merely more consistent.

Propositional vs. Non-propositional justification

Propositional justification

It is typically assumed that justification occurs only at the level of propositional knowledge, that what justifies a judgment or assertion is another judgment or assertion according to the logic of propositions. Propositional justification is incompatible with any theory in which perception is a source of justification, such as the realist theory of perception presented in this book.

Propositional justification's effect on Cartesian Empiricism

1. It further supports the idea that knowledge is phenomenal at base.

Explicitly by Bruce Aune: Knowledge, Mind, and Nature (1967) 32

"If there is to be any fundamental basis of empirical knowledge--something by which the truth of ordinary claims is to be defended--this basis must be propositional in character: it must be the kind of thing that can have a place in an argument. ... If, accordingly, the true basis of knowledge is regarded as phenomenal, it can at best consist of propositions about immediate experience."

Perception plays a role in the justification of beliefs about the world by providing/causing beliefs about experience, from which knowledge about the world is inferred. This is the representationalist model.

Implicitly In expecting the answer to the question "How do you know?" to be a statement.

Chisolm Theory of Knowledge (1966) 97

"As we emphasized earlier, the appearance of a physical object—the way of being appeared to which the object as stimulus serves to cause—plays a fundamental role in the context of justification. If I ask myself Socratically what my justification is for thinking that it is a tree that I see, and if I continue my self-examination in the way we attempted to describe in Chapter 2, I will reach a point at which I will justify my claim about the tree by appeal to a proposition about the way in which I am appeared to."

2. It adds another motive for requiring the basis of knowledge to be infallible in the sense of incorrigible. Self-justifying beliefs must be somehow infallible so that the question of justifying the justification (in infinite regress) does not arise.

Carl Hempel "Some Theses on Empirical Certainty" Review of Metaphysics V (1952) 621 "... to describe the evidence in question would mean simply to repeat the experiential statement itself." This is what it means to be self-justifying. But what justifies a judgment and makes it valid is the method by which it is reached, not whether a conclusion happens to be true. The color of a chair does not justify my conclusion that it is red unless I *see* the chair and its color. By extension, a phenomenal judgment would be justified by a prior awareness of an experiential state. That prior awareness would entail a non-propositional form of justification, but is avoided by describing experiential states as "self-presenting" so that they guarantee their own conceptual identification.

The propositional theory that all cognition is linguistic has the implicit complementary idea that perception is noncognitive. Cartesian empiricists want the noninferential bases of knowledge to be justified by perception in some way, but not by perception itself which because it is not linguistic is classified as non-cognitive. Yet there remains an implicit assumption of an older contradictory idea that preception is cognitive, that it involves a preconceptual and diaphanous awareness of the effects of external objects on the senses. The result is the "Janus faced notion of experience" which is at the same time "... statements, capable of standing in logical relation to the rest of the structure, and parts ... of the extra-linguistic world." Anthony Quinton The Problem of Perception 1965, 503. Experience is taken to consist in noncognitive states, but these states lie at an especially permeable location on the border between our knowledge and the extra-linguistic world. Unlike other natural facts, the states present themselves, they describe themselves, they are their own descriptions.

Propositional justification's effect on Linguistic Idealism

Contemporary idealists reject the older idea altogether and accept as clear-cut articles of faith the theses that all cognition is linguistic and perception is noncognitive. For example, Sellar's statement of psychological nominalism:

"... all awareness of sorts, resemblences, facts, etc., in short all awareness of abstract entities—indeed, all awareness even of particulars—is a linguistic affair." Sellars "Empiricism and the Philosophy of Mind" 160. The case for this position has been made entirely in the negative form of attacks on the Cartesian idea of a diaphanous awareness underlying our statements, and rejection of the Cartesian inner theater. It is possible to reject the diaphanous model yet retain the idea that perception is a nonconceptual and cognitive form of awareness (see previous 5 chapters). The diaphanous and linguistic models of awareness are false alternatives, an

argument against one does not support the other.

Rorty argues that if we reject propositional justification and the diaphanous grasp of inner contents then the only sense that we can give to awareness is a discriminative response to stimuli. But this is a noncognitive capacity shared with computers, amoebas, photoelectric cells. What else could nonlinguistic awareness be? All causal relations are differential reactions, so in that sense perceptual awareness is a discriminative response to an object. Awareness has a distinctive nature that discriminates it from other effects of other causes, as described in Part I.

There is no independent case for the linguistic model of awareness, only the rejection of the competitor to which it is opposed in a false dichotomy. The Cartesian competitor had analysed knowledge into two components, the relation between an object and a mental representation of that object, and the direct awareness of the representation. Kant rejected the first element because the external object becomes unknowable and otiose as a standard of objectivity, objectivity can only be found in consistency with prior knowledge. Kant rejects the second element on the basis that the diaphanous relation between the representation and subject is not a real relation at all. Instead, awareness is synthesized out of the sensory manifold according to what prior knowledge makes possible. Synthetic awareness is in opposition to a "spectator" or "mental eye" view of awareness.

The modern analogue of Kant's "conscious relation to an object" is the intentional idiom used to describe cognitive phenomena—meaning, reference, truth. What makes a cognitive vehicle of or about something is the function it performs within a pattern of rule-bound behavior, especially verbal behavior. Awareness and knowledge is synthesized out of a background substratum of social practices and linguistic conventions. There could be no foundational level of awareness prior to or below the linguistic and judgmental because it could have no intentional features.

As both the modern version and Kant's version of idealism are reactions against the Cartesian model, neither have any argument against the realist theory of perception offered here. The 'spectator' viewpoint can be separated from the diaphanous model of awareness to which it has been joined. Neither is perception a synthetic product, or reducible to the occurence of representations with intentional content. Nor is perception a synthesis of sensations by means of concepts, subconscious inferences or hypotheses.

Perception is a real relation between subject and object, it is a thoroughly cognitive discrimination of entities and their attributes. Perception provides a mode of nonpropositional, noninferential justification.

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Notes on "The Evidence of the Senses: A Realist Theory of Perception" by David Kelley

These notes paraphrase the author's points and are not accurate quotes unless in quote tags.

Footnotes are (mostly) not reproduced here.

{ My own added comments are in these curly brakets. }

Chapter 7 Perceptual Judgments

Perceptual judgment is the conceptual identification of what is perceived. Recognizing a percept as belonging to a certain type is the only epistemological issue concerning perceptual judgment.

Distinguishing a percept from a perceptual judgment is impossible for a theory that holds judgment is precisely what distinguishes perception from sensation. In Representationalism experiential states are interpreted as signs of external objects, interpretation being judgment. In Sensationalism the awareness of a whole with invariant properties is constructed from fluctuating sense data, construction being judgment. In the Realist theory judgment occurs after perception.

Perceptual judgment is analyzed in terms of the two parts of the act: reference and predication. The linguistic expression of a perceptual judgment is a statement of the form "x is P". The questions that can be asked are: Why do we believe (predicate) "x is P" but not "x is R"? and Why do we believe (reference) "x is P" and not "y is P"?

Perception and Reference

For a judgment to be justified by perception, the person judging must perceptually discriminate the object he takes to be an instance of the concept predicated.

A camouflaged soldier may present facing surfaces to the field of view but if he is not isolated as a figure discriminated from the background there is no awareness of a particular and no judgment can be formed. Awareness of various patches of color only justifies judgments about those patches. When there is awareness of the soldier he is recognized as an object, an entity with 3 dimensionality.

Demonstrative reference

"That is a hawk" is a statement that can be made about different birds in different fields by different persons. What makes identical statements be about different things is not the conceptual content but the demonstrative reference to different birds. The reference of the word 'that' is determined by the speaker's perceptual focus. There can be no failure of correspondence between the object of perception and the object of belief in demonstrative reference.

Attributive reference

"The man with the martini is tall" A judgement made of whatever satisfies the description whether or not it is present to perceptual focus is an attributive judgment. Attributive propositions are not perceptual judgments.

Demonstrative and attributive reference can be present at the same time. When looking over the people in a room one forms the judgment "The man with the martini is tall". But if he actually has water in his glass, the reference is still to the man one is looking at (demonstrative) not a different man across the room (attributive). In this case there were two judgments "This man has a martini" and "This man is tall" and perception determines the referent of both. {Proper names and definite descriptors can both be used in either mode of reference, but if demonstrative reference is present then there is redundant reference and it (demonstrative mode) has priority; the referring expression can be mistaken without disrupting the reference. A referring expression cannot be determined to be mistaken unless we know which referent to compare it with. }

Conceptually guided perception

Discrimination is necessary for justification, but not for speculating about what predicates might be ascribed. In trying to make sense of an unfamiliar view or obscure scene a variety of theories may be tried out. Searching for a pencil on a cluttered desk is a perceptual exploration conceptually guided a criteria for what a pencil looks like. Trying to learn what a cornice is in architecture might require explicit guidance in picking out referents as examples. The conceptual content of the guidance does not constitute the object. There is no definite judgment "Here is a pencil" or "Here is a cornice" until the object has been discriminated perceptually. Perceptual discrimination has an epistemological priority over any judgment or judgment-to-be.

Degrees of discrimination

Perceptual discrimination is not unitary but admits of degrees. Different circumstances and different sense modalities provide awareness of different sorts of structures and there are borderline cases. The factors relevant in determining what (if anything) has been discriminated also determine what (if anything) the corresponding perceptual judgment is about. Cases considered:

Visual occlusion- To perceive a thing as a whole does not require perceiving the whole thing - front, back and inside. (see Ch. 5) A perceptual judgment need not require perceiving front, back and inside to be justified. A cat is partly hidden behind a chair. The edge is experienced as belonging to the chair and the cat as extending beyond the limit imposed by the obstruction.

Majority visual occlusion- A hunter sees a patch of brown amid the brush on a hillside and judges he sees a deer. Two possibilities are compatible with the principle advanced.

1) The brown patch lies behind the bushes so it is perceived to extend beyond the visible contours. An object of indefinite extent is discriminated, a deer.

2) This is not a perceptual judgment but an inference - that shade of brown is a color deer have but not bushes or earth - and so not a counterexample to the principle.

Hearing- Hearing does not discriminate entities in the sense of solid physical objects but events. Yet hearing still follows the principle because judgments about what is heard are given descriptively in the form "that sounds like ... the sound made by the banging of pipes in the walls" or "that sounds like ... the sound made by the banging of a gong." The sounds of music and speech are not described but named {for music instrument/key/note, for speech voice/word}

Touch and sight - What object is judgment about when one can see a tub of water and put a hand in it to feel it is warm? Touch only informs about the water in contact with the hand but the judgment is about all of the water in the tub because the water is seen in its entirety. In this example, sight picks out the object referenced and touch justifies the predicate; different sense modalities are integrated together.

Blind touching- Groping in a dark cave, your hand plunges into something wet and cold. The pool of water is not discriminated as a definite object, but the border between air and water is discriminated. The judgment about the water being wet and cold applies to an indefinite extent of water.

Qualities- Primary qualities apply to whole entities: a whole apple is round, not its parts. A justified perceptual judgment about a primary quality requires discrimination of the entity having that quality. Secondary or continuous qualities apply to parts as well as wholes. A justified perceptual judgment about a secondary quality requires discriminating what the judgment is about: a portion or patch that is red, something in peripheral vision moved.

Hallucinations and dreams- Dreaming is noncognitive, the subject is detached from perceptual contact with reality and not in control of his mental processes. Nothing that happens in a dream needs to be justified, no principles of justification apply.

Hallucinations occur because of inner causes that radically disrupt cognitive functioning. Again the loss of control over the ability to be rational, be objective and judge makes justification impossible.

Even if a hallucination could justify, it would be in virtue of its internal phenomenal similarity to an actual percept. But the reason a percept justifies is not because of its similarity to a hallucination. The asymmetry entails that if there is such a thing as hallucinatory justification it is hierarchically dependent on perceptual justification. {Attacks on perceptual justification from hallucinatory justification cannot avoid the stolen concept fallacy.}

Perception and Predication

What is the justification for stating "x is P" but not "x is R"? Which of an entities attributes must one perceive - and how must one perceive them - in order to justify the predicate of a proposition stating a perceptual judgment?


To recognize is to perceive a similarity, as a red object possesses the same quality as other red objects. But a red object will also be similar to shades of orange and purple at the borderlines with red, and similar to other objects in other respects.

Recognition involves:

1) isolation of a relevant dimension of similarity

2) a sense of what degree of similarity along that dimension is necessary

3) a capacity to ignore perceptible differences within the permitted range of similarity

A theory of universals is necessary to know what qualities must be discriminated in the object to make it an instance of the relevant concept of an attribute or type. That is beyond the scope of this book.

A theory of concepts is necessary to know how the dimensions of similarity are isolated and retained as concepts and then combined with percepts to produce recognition. That is also beyond the scope of this book.

A perceptual judgment is conceptual, and has a propositional form. But there are more primitive, nonconceptual types of recognition.

• Children can learn to recognize an object when it reappears after being hidden long before they begin to acquire language.

• Adults can recognize the shape of a blackberry bush even when unable to describe it in words or think of it determinately in its absence.

In the propositional expression of a perceptual judgment the predication involved is direct and immediate, not mediated by any criteria or implicit inference. The predication is experienced with the same sense of immediate familiarity that characterizes preconceptual awareness.

Foundationalists of the Cartesian Empiricist pattern often accept an implicit theory of recognition based on a criterial feature list. Recognition of the object as a kind follows the recognition of the features defining that kind (a counterpart to the epistemological priority of attributes over entities in sensationalism). No explanation is offered for how the features are recognized, so the same problem remains but pushed down one level. It has not even been acknowledged that the statement "This is red" does not directly express the seeing red, but the judging that this is red. It has not been acknowledged that even simple concepts such as "red" are abstractions and that we cannot literally see abstractions.

The attributes of a concept can be understood as automatically predicated of anything identified as an instance of a concept, or understood as arrived at separately and inferentially from the premise that a thing is an instance of a concept. There is no epistemological difference between these positions; both commit one to the truth of propositions about the attributes and any doubt about whether an attribute is actually present also equally undercuts the justification for the conceptual identification.

Two Views of Concepts

Construction theory - Concepts are constituted by their definitions. Statements expressing a meaning given by the definition are analytic. Statements identifying attributes not specified in the definition are synthetic (whether in universal or particular form).

[footnote- a representative construction theory is Lewis, Analysis of Knowledge and Valuation, Book II, 1946]

Discovery theory - Concepts are constituted by the kinds of things picked out, those things may have open-ended number of properties in common. A definition is given in terms of the most essential common properties, but what is most essential is subject to revision without changing the concept. No analytic-synthetic distinction can be made.

[footnote- a discovery theory is developed by Ayn Rand, Introduction to Objectivist Epistemology 1979. A discovery theory is also implicit in the views of Saul Kripke and Hilary Putnam on the semantics of natural kind terms. See Kripke, Naming and Necessity, 1980 and Stephen Schwatrz (ed.) Naming, Necessity and Natural Kinds, 1977 esp. "Introduction" p 13-41 and Putnam's "Is Semantics Possible?" and "Meaning and Reference", 102-118, 119-132.

On either theory of concepts there is some collection of facts attributed to each referent due to being an instance of the concept, and some of those facts will be imperceivable or not perceived in a particular case. How can a perceptual judgment committing one to facts not perceived be justified?

Construction theory will claim that identifying an object as an instance of a concept only predicates the defining features of the concept. If all defining features are observable then predicating that concept is justified conclusively by perception. This leads to a structural foundationalism where all knowledge rests on a foundation of predicates that are strictly perceptual.

Discovery theory denies there is a difference in status between defining and non-defining features, so a predication cannot be limited to only some of the features of a concept. No concept can be predicated without committing to facts not perceived. Whatever inductive evidence one has that kind K has property P must justify the judgment that this K has P. All adult perceptual judgments rest in part on prior inductive knowledge. Foundationalism can only be true in a temporal {emphasis added} or genetic sense, there was a first time K was perceived and subsequent knowledge builds on that original encounter.

There is a compatibility between the construction model and representationalism, and also between perceptual realism and the discovery model. Subsequent analysis of concepts of sensory qualities will be on the basis of the discovery model.

Concepts of Sensory Qualities

Do concepts of sensory qualities designate the intrinsic attributes or the forms in which we perceive them? The question poses a false dilemma. Discovery theory holds that concepts evolve over time by integrating new knowledge to them. The development of a single concept over time has three distinct stages:

Naive level - there is no knowledge of illusions or perceptual relativity, no appearances.

Commonsense level - takes into account perceptual relativity, the possibility of illusion and uses the idea of appearances

Scientific level - incorporates knowledge of causal mechanisms of perception, both on the side of the sensory apparatus and of the objects perceived.

At the naive level what is perceived is attribute-in-a-form, a unitary content experienced as wholly external. Only background knowledge permits isolating the relational aspects of the identity perceived, knowledge which is lacking at that level. A concept of a sensory quality formed at the naive level will not be a concept of the attribute as opposed to the form, nor will it be a concept of the form as opposed to the attribute. A naive perceiver implicitly takes anything which looks red to be red, but will later learn this is a mistake and will reclassify certain objects under a new concept of appearance formed for the purpose - "looks red." Under normal conditions what looks red is red, so there will be a continuity of the concept in picking out the same kinds of things.

Roderick Firth argues that a naive perceiver (a child) has an early form of the concept "looks red". He takes this to be a property which objects have independently of him but will later learn this is a mistake and will form the new concept "red" for the property that objects have independently of him. A second argument is that a child implicitly uses "looking red" as a criteria for predicating red, so the concept is really that of the criteria "looking red". [Firth, "Coherence, Certainty, and Epistemic Priority," Journal of Philosophy, LXI (1964) 547.]

Refutation: Given the mechanisms of color constancy, there are objects that an adult would call red that a child would not. Therefore the child's concept of "red" is not coextensive with the adult concept of "looks red".

The criteriological argument is of the form: we are aware of A by means of or in virtue of B, therefore we are directly aware of B not A. This is the Representationalist pattern that was rejected in deciding what we really perceive, it is no more valid in deciding what we conceive.

The commonsense level allows the attribute to be isolated. The scientific level allows quantitative judgments about qualia to be made ("that looks like a 600nm red").

Perceptual relativity as noted and understood at the commonsense level is important to perceptual judgment, but the deeper relativity discovered at the scientific level is not. Advancing from the naive to the commonsense level may require some reclassification of objects in terms of the concept, advancing from the commonsense level to the the scientific level will require none. Secondary qualities predicated on the basis of perception (red, warm, sweet) are concepts which do not distinguish the attribute from the form. Red, warm and sweet are forms jointly caused by microscopic structural and chemical properties of the objects perceived and the physiological means of perception. {Knowing that red light is electromagnetic radiation at 600nm wavelength does not make a difference in its appearance.}

Illusions and Perceptual Relativity

"Being F" vs. "Appearing F" can only be distinguished conceptually. Illusions are a conceptual phenomena, misclassifications based on real appearances.

3 facts jointly make illusions possible:

• Form varies with conditions.

• A concept of secondary quality is a concept of an external feature of objects, in respect of which they are similar independently of us.

• A concept of secondary quality is formed and predicated on the basis of similarities in the forms with which we perceive its instances.

For an illusion to occur one must perceive an attribute not in the usual form but another form in which one normally perceives a different attribute and for which one possesses a different concept. (An entirely novel appearance won't have a corresponding concept so no misclassification will occur thus no illusion.)

Only in relation to our concepts can we identify any form of perception as illusory. Abnormal conditions are those in which we perceive objects in illusory forms.

Definition of Normal Condition- any condition of perception within a range that allows discrimination of the similarity to other objects subsumed by the same concept.

One must perceive the object in a form which is normal for the perception of F objects (F a concept of a sensory quality).

One must take into account any evidence one has that the conditions of perception are abnormal.

The conceptual override - Using background knowledge of what F looks like in abnormal conditions to make a judgment makes that judgment an inference.

Justified error - An object which is Not-F may be perceived in the form and normal conditions for the perception of F. One can be perceptually justified in judging a Not-F is F.

Two concepts of justification:

• "Being in a position to know" is what justifies - meaning in contact with reality. Knowledge is the correct identification of things as they are independently of our beliefs. By this theory an hallucinator is not in a position to know what he asserts, and neither is the subject of an illusion.

• "Reasonableness" What justifies is what makes it reasonable to think so. Justification is normative, a standard of what ought to be cognitive conduct. But "ought implies can", a person cannot be held accountable to a standard impossible to apply in a given case. By this theory the subject of an illusion is reasonable in forming the judgment to which his experience prompts him, and so is the hallucinator.

Holding to either theory of justification in disregard of the other is another manifestation of issues discussed in Chapter 1. The first theory disregards the process of knowing {intrinsicism}, the second theory discards reality as the standard {subjectivism}. Objectively, a percept, even an illusory percept, arises from the interaction of object, senses and conditions. A subject takes an object to be F on the basis of similarities that are the real product of perceptual contact with reality. Hallucinations can be reasonably interpreted in certain ways, but there can be no perceptual justification without perceptual contact with reality. The subject of an illusion can be justified, an hallucinator cannot.

Does the third principle require positive knowledge that conditions are normal? - No. The healthy functioning of one's own nervous system cannot itself be verified on the perceptual level. Also, checking the verifiable conditions of perception involves further perceptual judgments, those judgments would need to be checked, etc. in an infinite regress.

One can assume conditions are normal in the absence of evidence to the contrary, but one must be alert to that evidence. Evidence of abnormal conditions may be perceived as external phenomena, revealed in the way that everything appears, or only known conceptually. The scope of the abnormality can be restricted to a single feature such as color, or all judgments altogether. The strength of the evidence of abnormality can vary so as to render judgments completely unjustified or merely probable.

Arguments for requiring positive evidence of normal conditions:

1) Skepticism - We cannot be certain of any conclusion unless we know our faculties are operating reliably. We cannot know our faculties are functioning reliably unless conditions are normal. Therefore we cannot be certain of any conclusion reached by perception until we know that conditions are normal.

Refutation: First premise can be supported only if there is a real possibility that our faculties might be operating in fundamental disconnection with reality and constituting their own contents; this was dismissed in Chapter 1.

The skeptic presupposes the knowledge that conditions can affect perception, knowledge which can only be gained through perception. The skeptic uses that knowledge while attempting to deny its source.It is impossible to misidentify an object as F unless one already possesses the concept F, but the concept could not have been formed unless conditions were sufficiently stable to perceive the referents of F.

2) Wilfrid Sellars - Claims the not only must conditions be normal the subject must know they are normal. [sellars, "Empiricism and the Philosophy of the Mind" in Science, Perception and Reality (1963) 147-148] This rests on his view of knowledge as propositional. Prelinguistic non-propositional justification precedes any reflective ability to explain and defend our perceptual judgments to others. (see Chapter 6)

Positive evidence of normal conditions is not required. If there is no evidence of abnormal conditions then a perceptual judgment is justified directly by perceptual awareness and does not require propositional knowledge of other facts.

The growth of a subject's knowledge through the commonsense into the scientific level makes one aware of more of the variables constituting normal conditions, so the constraint of the second principle will apply more often. There are no universal rules about what judgments are justified in what conditions that can hold for all knowers.

The Autonomy of Perception

Perception can be influenced by psychological factors - expectations, needs, interests, biases, preconceptions. Interest directs the amount attention and the choice of what to focus on. What contradicts expectations will get more attention. In general, purposes and background knowledge provide a context for perceiving. Psychological factors do not threaten the objectivity of a percept or judgment unless they alter the percept or cause one to make judgments not supported by perception. Non-objective thinking is possible across the spectrum of all cognitive activities because objectivity is not automatic. So long as subjective biases can be identified and overcome then objectivity is still possible and a virtue.

Are subjective biases causally determining in a way that makes objectivity impossible?

Short answer - No.

• The universal form of the claim "all objectivity is impossible" is itself impossible and cannot claim to be objective.

• Statistical evidence that more people are nonobjective under certain motivations does not establish nonobjectivity as inescapable.

• Objectivity in perception is easy to achieve compared to introspection or scientific analysis.

Long answer - various arguments in favor of "yes" are considered and refuted.

Philosophical arguments

Thomas Kuhn and H.R. Hanson have argued perception is "theory-laden" influenced by the the very theories that are supposed to be tested by perception.

A scientist familiar with an X-ray tube will notice more and different things about it than a layman, but the percept of the scientist does not go beyond that of the layman much less distort it. Scientific and conceptual knowledge in general can enable the extraction of more information from a given stimulus. Distortion can only be demonstrated when opposing theories lead to incompatible percepts for the same stimulus.

Hanson claims that Tycho Brahe will see the sun rising over the Earth while heliocentrist Johannes Kepler will see the horizon dropping below the unmoving sun. Hanson claims this is a perceptual difference bit this is not credible. Anyone with a little imagination can see both perspectives, and while we are all heliocentrists today it is still more common to see the sun rising. Anyone can see the walls moving past while walking down a hallway.

Paul Churchland advances an argument [Churchland, Scientific Realism and the Plasticity of the Mind, 1979 Chap. 2) that perceptual judgment is theory-laden. His extended analysis of our concepts for heat argues that the concepts contain and implicit commonsense theory about the nature of heat, a theory called into play whenever we recognize something is hot or cold but which goes beyond what is actually perceptible. His argument is convincing but poses no difficulty for the temporal foundationalism described earlier. Adult perceptual judgments do go beyond what is given due to background knowledge, but that background knowledge was itself discovered perceptually at an earlier time. This admits that at one time the cognitive content of our concepts of hot and cold was exhausted by what was perceptible but Churchland argues against that by a thought experiment.

An alien race can see hot and cold because their respond to infrared radiation. They see it in the form of sensations of black and white. They have no other color sensations or color vocabulary. Should we translate their words used for their sensations as hot and cold or white and black? Churchland argues correctly that the translation should be hot and cold. (It is correct because the meaning of a concept is what it picks out in the world, what it refers to.) Even perceivers who discriminate in radically different ways than our own senses do can possess the same concepts we do. But Churchland goes on to conclude that this is because the meaning of concepts is set semantically. By assuming perception is non-cognitive, and providing an example showing a concept referring to something beyond the bare sensation, he takes as proven the coherence theory of meaning as determined by the network of acceptable sentences that use the concept. (He follows the pattern of proving Linguistic Idealism by attacking Cartesian Empiricism in a false dichotomy.) But perception is cognitive as argued earlier, it is the direct awareness of external objects and their attributes and concepts of sensory qualities are about the intrinsic attributes of those objects. The argument does not address this view so proves nothing.

Psychological arguments

The experimental data will not bear the interpretation given them.

Motivational effects on perception Jerome Bruner and other proponents of the "New Look" approach tested the influence of motivation on perception.

Children aged 3-5 turned a crank and were rewarded with candy. The control group received the candy directly while the experimental group received a poker chip they could trade for candy. After a sufficiently long exposure to this little economy the children were asked to make size estimates of a poker chip by adjusting a variable standard until it looked the same size to them as the chip. Children in the experimental group set the standard larger than children in the control group. It is concluded that value placed on an object can affect its perceived size. [Lambert, Solomon, Watson, "Reinforcement and Extinction as Factors in Size Estimation," Journal of Experimental Psychology, XXXIX (1949) 640.]


• Such young children (often used in these experiments) are more likely to be influenced by need or desire than adults.

• The overestimation was 6 percent - statistically significant but not justifying the perjorative word distortion.

• Numerous perceptual mechanisms aid discrimination by sharpening contrasts, tuning out irrelevant stimuli, etc. An increase in apparent size of valued objects may be one of these mechanisms.

• The method used for size estimation is the best possible evidence in psycho-physics used to measure dimensions of the forms in which objects are perceived. This is the strongest possible evidence that the effect was on the percept itself not the perceptual judgment.

• The mechanism interfered with the cognitive task of making accurate size comparisons, but children are not as flexible as adults in shifting their mental sets for new tasks.

• Bruner's own retrospective judgment [see Bruner, "The Functions of Perceiving: New Look Retrospective," in Jeremy Anglin (ed.) Beyond the Information Given (1973) 116-120] is that the experiments failed to show regular distorting effects on perception which were predicted by the New Look theory. Motivational factors influenced the direction and degree of attention not the cognitive content of percepts.

Cognitive Effects on perception Bruner and others also studied how expectations, sets, and background knowledge influenced perception. Experiments showing that practice at a task makes one better at it are not a problem. What we are looking for is evidence that cognitive factors can give rise to judgments in conflict with the stimulus information.

Bruner and Postman showed subjects playing cards and were asked to identify them. Each card was shown for a progressively longer time from 10 to 1,000 milliseconds until it was identified correctly. Some trick cards were introduced that had the wrong color for their suit (a red 3 of clubs, a black 6 of hearts). Normal cards could be identified after an average exposure of 28 milliseconds, the trick cards required an average of 114 milliseconds. [bruner, Postman "On the Perception of Incongruity: A Paradigm," Journal of Personality, XVIII (1949)]

• The experiment is sometimes said to show that expectations can prevent us from seeing objects which violate our expectations, but the measured effect was on the perceptual judgment not the percept.

• A judgment which conflicts with background knowledge should require more evidence than a judgment conforming with background knowledge, and staring at a card longer is more evidence. Perceiving, thinking and judging extend over time.

• At the very briefest exposures the subjects showed dominance reactions: they just consistently went with the suit or the color and did not have time to reconcile two features.

• Given enough time the subjects were always able to correctly identify the cards.

• Just before recognition occurred many subjects experienced extreme confusion, the sense that something was wrong with the card, the background beliefs about cards, or their compromise hypotheses ("that's a six of clubs in a red light"). Such confusion is a typical response to anomalies, and often found in scientific discovery and other forms of creative thought.

This is all perfectly compatible with rationality.

There are two problems with these kinds of experiments. First, they usually fail to isolate the effects on perception and are actually about the perceptual judgment. Even the most hasty judgments are partly volitional so epistemological explanations are as valid as psychological explanations. Second, the stimuli are typically impoverished compared to the normal case, i.e. they are abnormal in the sense of the second and third principles of justified perceptual judgment given above. Judgments made in abnormal conditions where the abnormality is the impoverishment are often reached by supplementing the missing information. There is a crucial difference between supplementing and distorting.

To avoid those two problems what is sought is a clear case where cognitive factors clearly influence the judgment and not the percept and in which the stimulus is clearly adequate for normal perceptual judgments, yet the judgment conflicts with the stimulus. The only clear case (and most cited because it is the only evidence available) is the case of phoneme restoration.

Phoneme restoration is a class of auditory illusion in which a recorded spoken sentence is edited to replace one phoneme with a cough sound, but listeners report hearing the missing sound. The illusion continues even when fully informed listeners know what is on the tape. The significance is not the illusion, but that the subjects' syntactic or semantic grasp of the word or sentence influences what is heard.

Nothing quite like this happens in other perceptual domains, not even other sorts of auditory perception. Generalization about perception as a class is not justified when all the evidence comes from a single sub-class with highly distinctive features.

As biological systems the senses are adapted to discriminate and identify natural objects. Symbolic objects are adapted to the senses. A good symbol minimizes the perceptual resources needed to recognize it. A symbol with a rich identity as a physical unit invites exploration, inefficiently drawing attention away from the meaning it bears. An ideal symbol is as transparent as possible and has the fewest perceptible features that enable identification. Symbols bear meaning only in context, so it makes sense to use context in discriminating symbols especially when the physical signal is obscured or degraded. Trading off some autonomy for a gain in speed and transparency of meaning makes sense for symbols.

Conclusion: The perception of speech is a special case that does not generalize to perception as a class. Needs and values influence attention and background knowledge influences conceptual identification. Perception is autonomous in respect of its cognitive content and capable of providing independent and objective evidence for our beliefs. There exist unusual circumstances where objectivity is not child's play, such as during a crime where things happen fast and emotions may be running high and expectations are violently upset, but they dramatize by contrast the reliability of judgment in normal cases.

Epistemology with a Knowing Subject

Twentieth century epistemology has been studied abstractly in terms of theories of knowledge, inference structures, logical relations among concepts, and logical justification of knowledge. This has all only worked to the extent it has because propositions and concepts can be studied in abstraction apart from any particular subject possessing those abstractions. This approach does not work at all for perception where the cognitive content possessed by the subject cannot be abstracted apart from the language used to express it.

Acknowledging the subject permits regarding perception as cognitive and makes possible the three principles of justified perceptual judgment. Without a full theory of concepts we cannot specify the way in which concepts must be held in order for predication to be justified by perception but we do know the principle involved would not be another belief but a skill. Justification depends in part upon the exercise of an intellectual virtue, objectivity. Skills and virtues alike with the contents of nonpropositional awareness cannot be abstracted away from the subject and captured in a logic of propositions.

[susan Haack "Epistemology with a Knowing Subject," Review of Metaphysics, XXXII (1979) 309-336]

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According to Wikipedia

Sensualism (also called sensationalism or sensism[1]) is a philosophical doctrine of the theory of knowledge, according to which sensations and perception are the basic and most important form of true cognition. It may oppose abstract ideas. The basic principle of sensualism is "there is not anything in mind, which hasn't been in the sensations."

Sensationalism is covered most directly in chapter two. The section on "Anti-Integration" at the end of chapter five is another refutation.

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Just out of curiosity, would this comment be consistent with or fall under the theory-ladenness of perception that Kelley discusses in his book:


"Knowledge can't begin with perception because observation requires knowledge to be effective. What do you observe and what not? You have to think first to answer that question before you make useful, selective observations.There are vast numbers of things to observe, patterns to find, perspectives to consider, and so on. How is one to choose? Whatever the answer, that we need to start there, not with perception."

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