Objects of Perception

Objects of perception are the entities we attend to when we perceive
the world. Perception lies at the root of all our empirical knowledge.
We may have acquired much of what we know about the world through
testimony, but originally such knowledge relies on the world having
been perceived by others or ourselves using our five senses: sight,
hearing, touch, taste, and smell. Perception, then, is of great
epistemological importance. Also, a philosopher's account of
perception is intimately related to his or her conception of the mind,
so this article focuses on issues in both epistemology and the
philosophy of mind. The fundamental question we shall consider
concerns the objects of perception: what is it we attend to when we
perceive the world? We begin with five different answers to the
question, "On what does my attention focus when I look at the yellow
coffee cup in front of me?"

1. Direct Realism

Perceptual realism is the common sense view that tables, chairs and
cups of coffee exist independently of perceivers. Direct realists also
claim that it is with such objects that we directly engage. The
objects of perception include such familiar items as paper clips, suns
and olive oil tins. It is these things themselves that we see, smell,
touch, taste and listen to. There are, however, two versions of direct
realism: naïve direct realism and scientific direct realism. They
differ in the properties they claim the objects of perception possess
when they are not being perceived. Naïve realism claims that such
objects continue to have all the properties that we usually perceive
them to have, properties such as yellowness, warmth, and mass.
Scientific realism, however, claims that some of the properties an
object is perceived as having are dependent on the perceiver, and that
unperceived objects should not be conceived as retaining them. Such a
stance has a long history:

By convention sweet and by convention bitter, by convention hot,
by convention cold, by convention colour; in reality atoms and void.
[Democritus, c. 460-370 BCE, quoted by Sextus Empiricus in Barnes,
1987, pp. 252-253.]

Scientific direct realism is often discussed in terms of Locke's
distinction between primary and secondary qualities. The Primary
qualities of an object are those whose existence is independent of the
existence of a perceiver. Locke's inventory of primary qualities
included shape, size, position, number, motion-or-rest and solidity,
and science claims to be completing this inventory by positing such
properties as charge, spin and mass. The secondary qualities of
objects, however, are those properties that do depend on the existence
of a perceiver. They can either be seen as properties that are not
actually possessed by the objects themselves, or, as dispositional
properties, properties that objects only have when considered in
relation to their perceivers. On the former interpretation, the cup
itself is not yellow, but the physical composition of its surface, and
the particular way this surface reflects light rays into our eyes,
causes in us the experience of seeing yellow. And, on the latter
interpretation, for an object to be yellow is for it to be disposed to
produce experiences of yellow in perceivers. Locke is usually seen as
being committed to this latter type of account:

Such qualities which in truth are nothing in the objects
themselves, but powers to produce various sensations in us by their
primary qualities. [Locke, 1690, 2.8.10]

The secondary qualities, then, comprise such properties as color,
smell and felt texture.

We have seen that for the naïve realist, objects that are not actually
being perceived continue to have all the properties we normally
perceive them as having. For the scientific realist, however, only
some of the properties we perceive continue to be possessed by objects
when there are no perceivers around, these being their primary
qualities.

The distinction between primary and secondary qualities is
controversial in various ways, but that need not concern us here. What
we should be clear on, however, is that the key feature of both naïve
and scientific direct realism is that we directly attend to objects
whose existence is independent of perceivers, objects that are out
there in the world. The following section questions this whole
approach.
2. Indirect Realism

The indirect realist agrees that the coffee cup exists independently
of me. However, through perception I do not directly engage with this
cup; there is a perceptual intermediary that comes between it and me.
Ordinarily I see myself via an image in a mirror, or a football match
via an image on the TV screen. The indirect realist claim is that all
perception is mediated in something like this way. When looking at an
everyday object it is not that object that we directly see, but
rather, a perceptual intermediary. This intermediary has been given
various names, depending on the particular version of indirect realism
in question, including "sense datum, " "sensum," "idea,"
"sensibilium," "percept" and "appearance." We shall use the term
"sense datum" and the plural "sense data." Sense data are mental
objects that possess the properties that we take the objects in the
world to have. They are usually considered to have two rather than
three dimensions. For the indirect realist, then, the coffee cup on my
desk causes in my mind the presence of a two-dimensional yellow sense
datum, and it is this object that I directly perceive. Consequently, I
only indirectly perceive the coffee cup, that is, I can be said to
perceive it in virtue of the awareness I have of the sense data that
it has caused in my mind. These latter entities, then, must be
perceived with some kind of inner analog of vision. We shall first
look at some weak arguments for this stance. After dismissing these we
shall turn to the Argument From Illusion. This is a highly influential
argument that many see as persuasive. In addition to supporting
indirect realism, the other three theories of
perception—phenomenalism, intentionalism and disjunctivism can be seen
as responses to it.

As well as looking at my coffee cup, I can look out of my window and
see the stars in the night sky. However, it is a fact (one that can
amaze on first discovery) that the star at which I am currently
looking may have ceased to exist. The pinpoint of light that I see has
taken years to reach me, and in that time the star may have turned
supernova. How can I, then, be directly attending to that star when it
is no longer there? What must be happening is that the light rays that
originated from that star have caused in me the presence of a
perceptual intermediary, an intermediary that is still present in my
mind, and thus, an intermediary to which I can still attend.

This argument can be applied not just to far distant objects, but to
everything we perceive. Light also takes time to travel from the cup
to my eyes. Therefore, I am now perceiving the cup as it was a
fraction of a millisecond ago. The steam I see rising from it is
actually further from the cup than it now appears to me. So again, it
cannot be the steam that I directly see since I am not seeing it in
the state that it is now in. It must, therefore, be a perceptual
intermediary that I perceive.

This, however, is not a persuasive line of argument. One should reject
the assumption that the object of perception has to exist at the
moment we become perceptually aware of that object. Perception is a
causally mediated process, and causation takes time. Because of this,
at the time when perceptual processing is complete, the properties of
perceived objects may be distinct from those possessed by the object
at the time when their causal engagement with our perceptual apparatus
began. As said, in extreme cases the objects of perception may no
longer exist at the moment when the causal process of perception is
complete. One should, therefore, accept that all the events we
perceive are to some extent in the past.

The fact that perception is a complex causal process motivates some to
offer another weak argument for the indirect realist position. There
are many neurophysiological features and physiological entities such
as retinal images that are involved in perception. Some conclude that
I do not directly see the cup; I see it via such entities, and the
indirect realist should take these to be his perceptual
intermediaries. The correct response here is to agree (as one must)
that such physiological items are indeed intermediaries in the process
of perception. They are, however, intermediaries in a different sense.
The indirect realist claims that we perceive his intermediaries — we
attend to them — just as we do to our image in the mirror. His
intermediaries are perceptually accessible. This, however, is plainly
not true of the physiological components of the perceptual process.
They are not, therefore, perceptual intermediaries in the correct
sense. They are simply part of the causal mechanism that enables us to
perceptually engage with objects, both those around us, and those in
the far distance. So far, then, we do not have any reason to give up
direct realism. Many, however, have seen the following argument as
providing such a reason.
a. The Argument from Illusion

Illusions occur when the world is not how we perceive it to be. When a
stick is partially submerged in water, it looks bent when in fact it
is straight. From most angles plates look oval rather than round. (We
still, of course, believe that the plate is circular and that the
stick is straight because of what we know about perspective and
refraction; but these objects can still look bent and elliptical if we
resist interpreting what we see with respect to such knowledge.) As
well as being prey to illusions, we can also have hallucinations in
which there is nothing actually there to perceive at all. It is both
of these phenomena that are seen to drive the following key argument
for indirect realism.

I'll partly submerge a pencil in my glass of water (the one that is
next to my yellow coffee cup). The pencil appears bent. There is,
then, a bent shape in my visual field. I know, however, that the
pencil is not really bent. (Or, if this were a case of hallucination
rather than illusion, there would not be a pencil there at all.) The
bent shape of which I am aware, therefore, cannot be the real pencil
in the world. Perhaps, then, it is a physical object on the surface of
my cornea, or one floating inside my eyeball (it is possible to see
such objects). Empirical evidence, however, has shown that there are
no such objects that correlate with our perceptual experiences. So, if
the bent shape is not a physical object, it must be something mental.
As we have seen, these mental items have been coined "sense data", and
it must be these that we attend to in cases of illusion and
hallucination.

Let us now turn to the veridical case. Cases of veridical perception
are qualitatively identical to those of illusion or hallucination, and
so there must be something in common between the normal case and these
non-veridical ones. (This is a key assumption to which we shall
return.) The conclusion we should draw, then, is that the common
factor between the veridical and the non-veridical cases of perception
is the presence of a sense datum. Therefore, in cases of veridical
perception it is also sense data with which we perceptually engage.
According to the orthodox interpretation, Locke can be seen as holding
such a theory: "The mind…perceives nothing but its own ideas" [Locke,
1690, 4.4.3]. (Ideas, of course, being mental components akin to sense
data.) And, this kind of theory has continued to have a distinguished
following, its adherents include Bertrand Russell, Alfred J. Ayer and
Frank Jackson (the latter, however, has recently abandoned this view).

There are various problems with this argument and we shall look at
some of these in the following section. However, whether or not the
argument is successful, there is no doubt that it has been highly
influential. The theories of perception covered in the rest of this
article are in part driven by the argument from illusion.
Phenomenalism (section 3) accepts the existence of sense data, but
denies that they play the role of perceptual intermediaries between
the world and us. There is no world on the other side of our sense
data; or, we should conceive of the material world as a construction
of our sense data. Intentionalism (section 4) agrees that there is
indeed something in common between the veridical and the non-veridical
cases. However, this common factor should not be seen as an object,
but rather, as intentional content. And finally, disjunctivism
(section 5) undercuts the argument from illusion by rejecting the
assumption that there must be something in common between the
veridical and non-veridical cases. We will discuss these theories
below, but first we shall consider the problems with the very idea of
sense data, and with the argument from illusion itself.
b. Problems for Indirect Realism
i. Dualism

Many see a problem with respect to the metaphysics of sense data.
Sense data are seen as inner objects, objects that among other things
are colored. Such entities, however, are incompatible with a
materialist view of the mind. When I look at the coffee cup there is
not a material candidate for the yellow object at which I am looking.
Crudely: there is nothing in the brain that is yellow. Sense data,
then, do not seem to be acceptable on a materialist account of the
mind, and thus, the yellow object that I am now perceiving must be
located not in the material world but in the immaterial mind. Indirect
realism is committed to a dualist picture within which there is an
ontology of non-physical objects alongside that of the physical. There
are, however, two major difficulties with dualism. These difficulties
are outlined below.

The first and greatest problem for the dualist concerns explaining the
interaction between mind and body. Remember, the indirect realist
accepts that there is a world independent of our experience, and, in
veridical cases of perception it is this world that somehow causes
sense data to be manifest in our minds. How, though, can causal
interactions with the world bring about the existence of such
non-physical items, and how can such items be involved in causing
physical actions, as they appear to be? If I have a desire for
caffeine, then my perception of the coffee cup causes me to reach out
for that cup. A non-physical sense datum causes the physical movement
of my arm. Such causal relations seem to be counter to the laws of
physics. The physical view of nature aims to be complete and closed:
for every physical event there is a physical cause. Here, though, the
cause of my reaching out for the cup is in part non-physical, and
thus, the closure of physics is threatened. The only way to maintain
both physical closure and the causal efficacy of the mental is to
claim that there is overdetermination, i.e. that my reaching for the
cup has two causes, one involving sense data, and one involving purely
physical phenomena, either of which is in itself sufficient to bring
about that action. This line, however, is difficult to accept since
according to such an account my perception of the cup is incidental to
my action: I would have reached for the cup even if I was not
consciously aware that it was there. There are, then, problems in
reconciling a non-physical conception of sense data with certain
widely held views concerning causation.

A dualistically conceived mind appears to be paradoxical in the same
way as fictional ghosts are: ghosts can pass through walls, yet they
do not fall through the floor; they can wield axes yet swords pass
straight through them. Similarly, the mind is conceived as both
distinct from the physical world, and also causally efficacious within
it, and it is not clear how the mind can coherently possess both
features. Descartes himself admitted that he was stumped by the
problem of how to account for the interaction between physical
entities and the mental realm:

It does not seem to me that the human mind is capable of
conceiving quite distinctly and at the same time both the distinction
between mind and body, and their union; because to do so, it is
necessary to conceive them as a single thing, and at the same time to
conceive them as two things, which is self-contradictory. [Descartes,
1970, 142]

A second problem associated with the non-physical nature of sense data
is that concerning their spatial location. Our perception presents
objects as lying in spatial relations with respect to each other.
According to the indirect realist, the objects of perception are sense
data, and thus, our perceptual experience presents one sense datum as
being in front of another, and that green one to the left of that red
one: "The relative positions of physical objects in physical space
must more or less correspond to the relative positions of sense data
in our private spaces" [Russell, 1912, p. 15]. But how can this be so?
On the Cartesian conception of dualism, the non-physical does not have
spatial dimensions, and so how can one component of this realm be seen
as in front of another? And, how can such non-physical entities be
describable in the spatial way we describe physical bodies? How can a
non-physical sense datum be round or square? The non-physical nature
of sense data seems to threaten the coherence of an indirect realist
description of sensory experience. We can say that we see the round
green object as just to the left of the square red one if we are
talking about spatially located objects in the world, but not if we
are talking about non-physical mental items, items for which the idea
of spatial location has no application.
ii. Adverbialism

Some see the argument from illusion as begging the question. It is
simply assumed, without argument, that in the non-veridical case I am
aware of some thing that has the property that the stick appears to me
to have. It is assumed that some object must be bent. One can,
however, reject this assumption: I only seem to see a bent pencil;
there is nothing there in the world or in my mind that is actually
bent. Only if you already countenance such entities as sense data will
you take the step from something appears F to you to there is an
object that really is F. Such an objection to indirect realism is
forwarded by adverbialists. We can illustrate their claim by turning
to other everyday linguistic constructions, examples in which such
ontological assumptions are not made. "David Beckham has a beautiful
free kick" does not imply that he is the possessor of a certain kind
of object — a kick — something that he could perhaps give away or sell
in the way that he can his beautiful car. Rather, we take this to mean
that he takes free kicks beautifully. When one gives a mean-eye, one
looks meanly at somebody else; one does not offer them an actual eye
of some kind. Similarly, then, when one perceives yellow one is
sensing in a yellow manner, or yellowly. Our perception should be
described in terms of adverbial modifications of the various verbs
characteristic of perception, rather than in terms of objects to which
our perceptual acts are directed. As I sip my drink, I see brownly and
smell bitterly; I do not attend to brown and bitter objects, the inner
analogues of the properties of the cheap coffee below my nose. As
Wittgenstein often took great pains to point out, many philosophical
problems are simply the result of grammatical confusion, or, as Lowe
puts it, "an inconvenient legacy of Indo-European languages" [Lowe,
1995, p. 45]. In describing our perceptual experiences we are not
describing the visual and olfactory properties of mental items; but
rather, we are talking about the manner in which we experience the
external world. Thus, if one can give an account of what it is to
experience in a brown and bitter manner, then one can account for
perception without relying upon sense data. This, we shall see below,
the intentionalist and the disjunctivist attempt to do.
iii. The Veil of Perception

Indirect realism invokes the veil of perception. All we actually
perceive is the veil that covers the world, a veil that consists of
our sense data. What, then, justifies our belief that there is a world
beyond that veil? In drawing the focus of our perception away from the
world and onto inner items, we are threatened by wholesale skepticism.
Since we can only directly perceive our sense data, all our beliefs
about the external world beyond may be false. There may not actually
be any coffee cups or olive oil tins in the world, merely sense data
in my mind. However, for this to be a strong objection to indirect
realism, it would have to be the case that direct realism was in a
better position with respect to skepticism, but it is not clear that
this is so. The direct realist does not claim that his perceptions are
immune to error, simply that when one correctly perceives the world,
one does so directly and not via an intermediary. Thus, things may not
always be the way that they appear to be, and therefore, there is
(arguably) room for the sceptic to question one-by-one the veracity of
all our perceptual beliefs.
3. Phenomenalism

Some have embraced the skepticism suggested by indirect realism and
accepted the anti-realist position that there is no world independent
of the perceiver. Two strategies that take this line are idealism and
phenomenalism. Berkeley (1710) is an idealist. For him, physical
objects consist in collections of ideas or, what have later come to be
called, "sense data." It is only objects conceived of in this way of
which we can have knowledge. Sense data, however, cannot exist if they
are not being perceived, and so, 'physical' objects conceived of in
this way are also dependent on perceivers. For Berkeley, therefore,
the universe simply consists in minds and the sense data that they
perceive. There is only immaterial substance.

A consequence of such an account would seem to be that when we do not
perceive the world it does not exist; there are gaps in the existence
of objects. Berkeley, however, attempts to avoid this conclusion by
claiming that God "fills the gaps." God perceives the objects that are
not perceived by us, and thus, sustains their existence; an existence,
though, that subsists merely in the realm of ideas or sense data.

[A]ll the furniture of the earth….have not any subsistence without
a mind…their being is to be perceived or known,….consequently, so long
as they are not actually perceived by me or do not exist in my mind or
that of any other created spirit, they must either have no existence
at all or else subsist in the mind of some external spirit…. it being
perfectly unintelligible….to attribute to any single part of them an
existence independent of a spirit. [Berkeley, 1710, part 1, para. 6]

Such a position is of course highly problematic, but perhaps
surprisingly, some of its idealistic elements were widely adopted in
the early twentieth century by a group of philosophers called
'phenomenalists.'

Idealists conceive of the world in terms of our actual experiences
(and, for Berkeley, those of God). Phenomenalists hold a related
position: for them, propositions about the physical world should be
seen as propositions about our possible experiences. Or, as Mill
(1867) claims, material objects are nothing but "permanent
possibilities of sensation." Phenomenalism is classically taken as a
conceptual thesis: statements about physical objects have the same
meaning as statements describing our sense data.

The meaning of any statement which refers to a material thing may
be fully conveyed in statements which refer solely to sense-data or
the sensible appearance of things. [Chisholm, 1948, p. 152. Note,
however, that this is not Chisholm's own view]

Phenomenalism, therefore, avoids the problem of gaps in a distinct
way. Physical objects can exist unperceived since there is the
continued possibility of experience. To say that the paper clip is in
my drawer is to say that I would see it on opening that drawer. The
world, then, is described in terms of our current sense data, and in
terms of conditionals that detail which sense data we would encounter
in counterfactual and future situations. We must, however, be careful
to note the crucial difference between the realist and anti-realist
readings of such conditionals. Realism, be it direct or indirect, has
an account of why such a conditional holds: I will have the experience
of perceiving a paper clip since there exists independent of my mind a
real paper clip in the drawer. Phenomenalists, however, do not ground
their conditionals in this way since there is no world independent of
our (possible) experiences. To say that the paper clip is in my
drawer, is simply to say that the flux of sense data characteristic of
the experience of opening a drawer will be followed by the experience
of perceiving the silvery-colored sense data that constitutes a
perception of a paper clip. There is no mention here of an independent
world; such conditionals are only described in terms of the content of
one's experiences.

To make the phenomenalist claim clear, it is useful to look at the
distinction between dispositional and categorical properties.
Conditionals can be used to describe dispositional properties such as
solubility: that lump of sugar is soluble since it will dissolve if I
put it in my cup of coffee. Dispositional properties, however, usually
have a categorical grounding. Sugar is soluble because of its chemical
structure. The conditionals of the phenomenalist, however, should be
taken as describing dispositions that do not have such a grounding.
The regularities in our experience that they pick out do not have a
categorical basis, unlike the psychological regularities of the
realist that are grounded in our engagement with the existent external
world. The experiential regularities of the phenomenalist are brute;
nothing further can be said about why they hold.
a. Problems for Phenomenalism

For many, the idealistic nature of phenomenalism is unpalatable. A
consequence of phenomenalism would seem to be that if there were no
minds then there would be no world. This is so since 'physical'
objects are simply constructs of our (possible) experience. Let us
also consider the thoughts of others. I seem to be able to interpret
what you are thinking by considering your behavior, by watching your
actions and listening to your utterances. Your behavior, however, like
the rest of the material world, simply consists of my sense data and
the counterfactual relations of these mental items. Thus,
phenomenalism invokes a solipsistic picture in which it is my sense
data alone that constitute the world. A phenomenalist sitting here
reading this article from the screen must claim that the computer
monitor simply consists in the possibility of sensations that their
own physical body (also a part of the material world) also has this
nature, and that the people which can be seen in the street outside
are similarly constructs of the phenomenalist's own sense data.
Phenomenalism is a very radical stance to take.

Also, even for those who do not have qualms about adopting such an
idealistic and solipsistic stance, there are arguments which suggest
that phenomenalism cannot complete the project it sets itself. A key
argument against phenomenalism is the argument from perceptual
relativity. Chisholm (1948) argues that one cannot provide
translations of statements about physical objects in terms of
statements about sense data. For a phenomenalist, the statement that
there is an old green olive oil tin to my right means that the
experience of reaching to the right would, on encountering the jagged
rim, be followed by a sharp sensation; and that the sensation of
turning my head would be followed by the presence of green sense data
in my visual field. However, such fluxes of experience need not occur
in this way. With gloves on, I would not feel such a sharp sensation;
and, I may be color blind or the lights may be out and thus I may not
experience green sense data. The sensations I have depend on various
facts about me (the perceiver) and my environment. There are no
lawlike conditional statements that describe the relation between
sensations considered in isolation from physical aspects of the
perceiver and of the world.

To calculate the appearances with complete success, it is
necessary to know both the thing perceived and the (subjective and
objective) observation conditions, for it is the thing perceived and
the observation conditions working jointly which determine what is to
appear. [Chisholm, 1948, p. 513]

A phenomenalist cannot account for such observation conditions since
he is not permitted to talk of the physical states of the perceiver or
those of the environment. He can only talk of sense data and the
relations between them. Therefore, according to Chisholm, there are no
phenomenalist translations to be had, and thus, phenomenalism fails.
4. The Intentional Theory of Perception

The last two positions at which we shall look deny that sense data are
involved in perception. To do this they must find alternative
responses to the argument from illusion, and they must provide a story
that explains how we are in direct contact with the world.

Intentionalists emphasize parallels between perceptions and beliefs.
Beliefs represent the world: I now have a belief about the pencil tin
(the one that used to contain olive oil), and this belief represents
that particular part of the world as being green. Beliefs, then,
possess aboutness or what philosophers of mind call "intentionality."
Intentionality is considered to be an essential feature of the mind,
and it describes the property that certain mental states have of
representing — or, being about — certain aspects of the world. The
aspects of the world that a belief is about can be specified in terms
of its intentional content. The intentional content of my current
belief is that tin is green. The intentionalist claim is that
perceptions are also representational states (intentionalism is
sometimes called representationalism). I can, then, believe that that
tin is green, and I can also perceive that it is. You are about to
perceive that the first word of the next paragraph is "Let." Your
perception is intentional: it is about a word on the screen; and, its
content is that the next word is "Let."

Let us see how the intentionalist reacts to the argument from
illusion. The key claim will be that representational states can be in
error. I can have false beliefs: I can believe that my cup is full
when it is not; and I can have beliefs about non-existent entities: I
can believe that the Tooth Fairy visited me last night. Such beliefs
are analogous to the non-veridical perceptual cases of illusion and
hallucination. In both belief and perception, the world is represented
to be a certain way that it is not. And, crucially, the intentionalist
has an account of what such veridical and non-veridical cases have in
common: their intentional content. My perception has the
representational content, there is a bent pencil there, whether or not
there really is such a pencil in the world (I might have been duped
and an actual bent pencil placed in the glass). In the veridical case
this content correctly represents the world; in the non-veridical case
it does not. Intentionalists, therefore, agree with sense datum
theorists that there is an aspect of perception that is shared by the
veridical and the non-veridical cases. This shared component, however,
is not the presence of a perceptual object, but rather, that of a
certain intentional content. Therefore, both intentionalists and sense
datum theorists can be seen as providing representational accounts of
perception: intentional content and the sense data of the indirect
realist represent the state of the independent external world.
Intentionalists, however, have representation without an ontological
commitment to mental objects.

Intentionalism is driven by current themes in the philosophy of mind.
Many in that field are optimistic about providing a broadly
scientific, causal account of representation and intentionality. If
one could provide such an account then a naturalistically acceptable
theory of perception should be seen to drop out of this research. To
explain perception one does not have to posit non-physical sense data;
rather, one could simply use one's naturalistic account of intentional
content, since, according to intentionalists, the important features
of perception are captured by this notion.
a. Clarification of the Intentional Theory of Perception
i. Non-Conceptual Content

There is a debate concerning the nature of the representational
content relevant to perception. We are talking of content, so all are
agreed that such content is evaluable as correct or incorrect. The
question of whether the world is as it is represented to be is always
pertinent. The debate, however, concerns whether all such
representational content must be conceptually structured (see
McDowell, 1994, lecture 3); or, whether some of the representational
content involved in perception is non-conceptual (see Peacocke, 1992,
chapter 3). (A concept is a constituent of thought that is apt for
being the content of a judgment or a belief.) Two arguments that
suggest the existence of non-conceptual content are those concerning
the fine-grain of experience and the experience of animals.

It seems implausible that I have a distinct concept for every shade of
brown that I perceive in the pair of battered old corduroy trousers
that I am now wearing, or concepts corresponding to all the nuances of
my neighbor's distorted music that I am currently hearing through my
study wall. Our experience appears to be more finely grained than our
conceptual repertoire. If one is an intentionalist, then one could
invoke representational content that is not conceptual to account for
the richness of one's experience. Also, many are unwilling to ascribe
conceptual capacities to animals (at least if one goes far enough down
the phylogenetic ladder). However, those same people are often less
restrictive with their ascription of experiential properties. They
would like to allow animals to have experiences and perception without
a conceptual framework within which to structure them. If one is an
intentionalist, then non-conceptual content could also be invoked to
account for animal perception.
ii. Phenomenology

There are problems associated with accounting for the phenomenological
features of perception. My experience consists in more than simply
representing that the world is a certain way; it is also the case that
the way I acquire representations strikes my consciousness
distinctively. Right now there is a faint sound of a road drill
syncopating with the reverse warning beep of a supermarket delivery
truck; the yellow cup in front of me is slowly fading to brown as a
cloud passes overhead; and the smell of coffee is struggling to get
past my persistent cold and the pungency of my throat lozenges. All of
this is part of my perceptual experience, and for the intentionalist,
this experience consists in such representational content as, the
truck is emitting a beep, and, my throat lozenge is pungent. There is
also, however, something "it is like" to be having such
representations (see Nagel, 1974). Our experience has a
phenomenological dimension, a dimension that you are probably
currently imagining. The shrill beep goes right though me, and the
lozenge is so strong that although it pervades my consciousness, I
somehow also feel sharper, clearer, more finely tuned to the quality
of the air that I am breathing. The intentionalist, therefore, must
also account for these phenomenological properties of perception. I
shall look at two responses here, one that develops the intentionalist
line in order to account for these features of perception, and one
that takes such considerations to show that a pure intentionalist
account is untenable.

One route that the intentionalist could take is to identify the
phenomenological aspects of our experience with the representational.
Naturalistically minded philosophers attempt to provide a causal
account that explains how our mental states, experiences and
perceptions have the intentional content that they do. One could,
then, claim that the causal processes that ground intentional content
also have a phenomenological aspect. It is the very same state that
has both representational content and phenomenological features.

There are, however, problems associated with such a claim. Some see an
unbridgeable gap between physical and phenomenological phenomena (see
Levine, 1983). Any account couched in terms of the broadly physical
properties of the brain cannot hope to capture the conscious,
phenomenological dimension of thought and perception.

[There is] the feeling of an unbridgeable gulf between
consciousness and brain process…This idea of a difference in kind is
accompanied by slight giddiness. (Wittgenstein, 1953, § 412)

Others, however, see this explanatory gap as illusory (see Tye, 2002).
Here, though, is not the place to pursue this debate.

The second broad response to the phenomenology of experience is to
claim that representational properties alone cannot account for
perception, and thus, one should reject the intentionalist project. If
one is to account for what it is like to perceive the world, then one
also requires sensational properties (properties distinct from those
relevant to representation). Peacocke (1988) supports this line. He
suggests examples in which there are aspects of our experience that
have the same representational content, yet which differ in their
phenomenological character. He therefore claims that representational
content alone cannot account for phenomenology. Ahead of you on the
motorway are two trucks, one just ahead and one near the horizon. You
represent them as being of the same size and as moving at the same
speed. There is, however, a sense in which the nearer one seems bigger
to you — it takes up more of your visual field — and, it moves across
your visual field at a faster rate. These features of your experience,
then, are not captured in terms of representational content.
Peacocke's claim, therefore, is that "concepts of sensation are
indispensable to the description of the nature of any experience"
[Peacocke, 1983, p. 4].

Advocates of Peacocke's line often favor the existence of qualia
(singular: quale). These are seen (by some) as the
non-representational, phenomenological properties of experience. One
must, however, be very careful when reading the literature concerning
qualia since the term is sometimes used in other ways. Others see it
as merely referring to the phenomenological aspects of our experience
(whether or not these can be captured in representational terms). In
this sense, qualia are uncontroversial; they merely commit one to the
claim that our experience is conscious. Others, notably Dennett (1991,
chapter 12), take qualia to be essentially private, and our knowledge
of them to be incorrigible. Conceived thus, he denies that there are
such entities.

We have, then, been considering whether the phenomenological aspects
of perception can be integrated into an intentionalist account. In
summary, one can either identify these phenomenological features with
the causal processes that are constitutive of the representational
content of perception, or one can take such features to demand that an
account of perception must include properties other than those that
are representational.
5. Disjunctive Accounts of Perception

Finally we have a rather different approach. Disjunctivism denies the
key assumption that there must be something in common between
veridical and non-veridical cases of perception, an assumption that is
accepted by all the positions above, and an assumption that drives the
argument from illusion. For the disjunctivist, these cases certainly
seem to be the same, but they are, however, distinct. This is because
in veridical perception the world is presented to us. The world is not
just represented as being a certain way, as for the intentionalist;
but rather, the world partly constitutes one's perceptual state. Thus,
one's perceptual state when hallucinating is entirely distinct from
one's perceptual state when actually attending to the world. To be in
the state that I am in when I veridically perceive a green tin, there
really has to be something there that is green. This, remember, is
also one of the commitments of the sense datum theorist; but for the
disjunctivist, the green item is in the world, it is not an internal
mental object.

This position is called "disjunctivism" because when I seem to see a
green tin, I am either perceiving a green tin or it is as if there is
a green tin in front of me (a disjunction of perceptual states). I am
not in a perceptual state that is common to both types of experience.

Of facts to the effect that things seem thus and so to one, we
might say, some are cases of things being thus and so within the reach
of one's subjective access to the external world, whereas others are
mere appearances. [McDowell, 1986, p. 241]

Disjunctivism can avoid the argument from illusion since it does not
accept that veridical and non-veridical perceptual states are in any
way the same (they only seem to be). We do not, therefore, have to
posit a common factor, either in the form of a sense datum, or an
intentional content. There is, then, a key difference between the
strategies of the intentionalist and the disjunctivist:
intentionalists answer the argument from illusion by claiming that
veridical and non-veridical perceptions have a type of
representational state in common, whereas disjunctivists undercut the
argument by claiming that there is no need to posit such a common
factor.

Proponents of disjunctivism see their position as upholding certain
common sense assumptions about the nature of perception. It is claimed
that both sense datum theorists and intentionalists do not account for
the idea that it is the qualities of the tin in front of me of which I
am directly conscious. This is because for the former it is the
qualities of a mental sense datum that are the focus of my
consciousness; and for both, the content of one's experience could be
just the same even if there was not a tin there and one was
hallucinating. Such accounts, then, do not capture the intuition that
the nature of my current experience is constituted by my consciousness
of the properties of the tin at which I am looking.

However, in any particular case the disjunctivist must accept that he
cannot tell which disjunct holds. When prey to illusion or
hallucination, it can seem to you as if you are really perceiving the
actual state of the world, and thus, it seems to you that you are in
the same perceptual state that you would be in if the world was really
how you perceive it to be. A consequence of disjunctivism, then, is
that one can be not only deluded about the state of the world, but
also about the state of one's own mind. When one is unknowingly prey
to illusion or hallucination, one is in fact in an entirely distinct
perceptual state from the state that one takes oneself to be in. This
is an anti-Cartesian position since:

In a fully Cartesian picture, the inner life takes place in an
autonomous realm, transparent to the introspective awareness of its
subject. [McDowell, 1986, p.236]

[The mind is] a realm of reality in which samenesses and
differences are exhaustively determined by how things seem to the
subject, and hence which are knowable through and through by
exercising one's capacity to know how things seem to one. [Ibid.
P.249]

a. Disjunctivism and Cognitive Externalism

A consequence of disjunctivism is that two physically identical brains
can be in distinct perceptual states. Imagine there is a demon or a
very clever scientist who uses his supernatural powers or hi-tech
wizardry to simultaneously remove the green tin from existence, while
stimulating my brain in the way that it would have continued to be
stimulated if the green tin had remained there on my desk. If this
were so, experientially everything would appear to me to be the same
as it is now, and, ex hypothesi, the flux of my brain states would
also be the same as that which is currently occurring as I now look at
the tin. According to the disjunctivist, however, such demonic
intervention will induce in me an entirely distinct perceptual state,
that of a hallucinatory rather than a veridical perception. Many
cannot accept this consequence of disjunctivism. They claim that the
mind must supervene on the brain, i.e. that if the physical states of
two brains are identical, then so too must be the thoughts,
experiences, and perceptions manifest in those brains.

However, the disjunctivist conclusion can be embraced by those who
accept cognitive externalism. For such externalists, the world plays a
constitutive role in determining the content of our mental states:
"Cognitive space incorporates the relevant portion of the 'external'
world" [McDowell, 1986, p. 258]. The contents of the brain alone do
not determine the nature of our thoughts and experiences. There is,
however, some notion of supervenience maintained in that the mind
supervenes on the brain together with its causal links to the
environment: if there are two identical brains causally connected to
the same features of their environment, then the mental states
manifest in those brains must also be identical.

Various arguments have been forwarded for this externalist position;
most notable is Putnam's Twin Earth thought experiment (1975). We can
imagine two physically identical characters, Oscar and Toscar; Oscar
lives here and Toscar lives on Twin Earth, a superficially identical
planet over the other side of the universe. Oscar and Toscar are
molecule for molecule alike, right down to the structure of their
brains; and, they both have beliefs about the clear stuff that lies in
puddles and rains from the sky. On Twin Earth, however, this clear
refreshing liquid is in fact XYZ and not H20. Toscar, then, is
thinking about different stuff to Oscar, and therefore, the thoughts
of Oscar and Toscar have different content, even though we have
specified that everything inside their heads is the same. The
externalist stance can be summarized thus: "Thought content ain't in
the head" (to hijack Putnam's phrase). Disjunctivists hold a parallel
claim: since it is the state of the world that determines the content
of one's perceptual state, hallucinations have nothing perceptually in
common with veridical perceptions even though all could be the same
inside one's head. Therefore, one must accept such externalist
thinking if one is to take on the disjunctivist position.

We have, then, come to the end of our survey and we have found that
perception is the focus of rich philosophical debate. We have seen
that it is the point at which the philosophy of mind, epistemology and
metaphysics meet. Therefore, one's account of the objects of
perception will be characteristic, not only of one's views on how we
acquire knowledge about the world, but also, of one's philosophical
perspective on such wider issues as those concerning the constitution
of the mind, the constitution of the world, and crucially, how the
former engages with the latter.
6. References and Further Reading

* Barnes, J., Early Greek Philosophy, Penguin, London, 1987.
* Dennett, D., Consciousness Explained, Little, Brown and Company,
New York, 1991.
* Descartes, R., Descartes: Philosophical Letters, Trans. / ed. A.
Kenny, Clarendon Press, Oxford, 1970. Levine, J., "Materialism and
Qualia: The Explanatory Gap" in Pacific Philosophical Quarterly, 64,
pp. 354-361, 1983.
* Locke, J., An Essay Concerning Human Understanding, ed. P. H.
Nidditch, 1975, Clarendon Press, Oxford, 1690.
* Lowe, E. J., Locke on Human Understanding, Routledge, London, 1995.
* McDowell, J., "Singular Thought and the Extent of Inner Space"
in Mind, Knowledge and Reality (1998) Harvard University Press,
Cambridge, Mass., pp. 228-259, 1986.
* McDowell, J., Mind and World, Harvard University Press,
Cambridge, Mass., 1994.
* Nagel, T., "What it is like to be a Bat" in Philosophical
Review, 83, pp. 435-56, 1974.
* Peacocke, C., Sense and Content, Oxford University Press, Oxford, 1983.
* Peacocke, C., A Study of Concepts, MIT Press, Cambridge, Mass., 1992.
* Putnam, H., "The Meaning of Meaning" in Philosophical Papers,
Volume 2, Cambridge University Press, Cambridge, 1975.
* Tye, M., Consciousness, Color, and Content, A Bradford Book, MIT
Press, Cambridge, Mass., 2002.
* Wittgenstein, L., Philosophical Investigations, tr. G. E. M.
Anscombe, Blackwell, Oxford, 1953.

Suggestions for Further Reading

For indirect realism see:

* Ayer, A. J., The Foundations of Empirical Knowledge, MacMillan,
London, 1947.
* Russell, B., The Problems of Philosophy, Oxford University
Press, Oxford, 1912.
* Grice, H. P., "The Causal Theory of Perception" in Proceedings
of the Aristotelian Society, Supplementary Volume, 35, pp. 121-52,
1961.
* Jackson, F., Perception: A Representative Theory, Cambridge
University Press, Cambridge, 1977.

For phenomenalism see:

* Mill, J., An Examination of Sir William Hamilton's Philosophy,
Longmans Green, London, 1867.
* Berkeley, G., A Treatise Concerning the Principles of Human
Knowledge, in Berkeley: Philosophical Works, ed. M. R. Ayers (1975)
Dent, London, 1710.
* Chisholm, R., "The Problem of Empiricism" in Journal of
Philosophy, 45, pp. 512-517, 1948.

For intentionalism see:

* Tye, M., Ten Problems of Consciousness, A Bradford Book, MIT
Press, Cambridge, Mass., 1995.
* Armstrong, D. M., Perception and the Physical World, Routledge
and Kegan Paul, London, 1961.

For disjunctivism see:

* Hinton, J. M., Experiences, Clarendon Press, Oxford, 1973.
* McDowell, J., 'Criteria, Defeasibility and Knowledge' in Mind,
Knowledge and Reality (1998) Harvard University Press, Cambridge,
Mass., 1982.