## 1. Our Ordinary Conception of Perceptual Experience



A.D. Smith claims that what most authors have in mind in talking about
the Problem of Perception is the "question of whether we can
ever directly perceive the physical world", where "the
physical world" is understood in a realist way: as having
"an existence that is not in any way dependent upon its being...
perceived or thought about" (2002: 1). The arguments at the
heart of the Problem of Perception challenge this *direct
realist* perspective on perceptual experience. But since this
perspective is embedded within our *ordinary conception* of
perceptual experience, the problem gets to the heart of our ordinary
ways of thinking.



So, what is our ordinary conception of perceptual experience? And how
does it embed a direct realist perspective?


### 1.1 Starting Points



We conceive of perceptual experiences as occurrences with phenomenal
character. The phenomenal character of an experience is what it is
like for a subject to undergo it (Nagel (1974)). Our ordinary
conception of perceptual experience emerges from first-personal
reflection on its character, rather than from scientific
investigation; it is a conception of experience from a "purely
phenomenological point of view" (Broad 1952: 3-4). We'll
present this conception by outlining what phenomenological reflection
suggests first about the *objects*
 (SS1.2),
 *structure*
 (SS1.3),
 and *character* (SS1.5)
 of experience, and then about the relation between veridical,
illusory, and hallucinatory experiences, and in particular whether
these cases form a *common kind*
 (SS1.6).



Let's begin with P.F. Strawson's idea that "mature
sensible experience (in general) presents itself as, in Kantian
phrase, an immediate consciousness of the existence of things outside
us" (1979: 97), and similarly McDowell's idea that
perceptual experience appears to be an "openness to the
world" (1994: 111), conceived of as openness to mind-independent
reality (1994: 25-26).



These ideas reflect the basic phenomenological observation that
perceptual experiences have objects, and more specifically direct
objects: objects that are simply perceived or experienced, but not in
virtue of the perception or experience of distinct, more
"immediate", objects.



Various authors appeal to a notion of directness in outlining our
ordinary conception of perceptual experience, and the Problem of
Perception. A dissenting voice is Austin (1962), and for recent
critical discussion see Martin (2017). For further discussion of how
to understand notions of direct and indirect perception, see Jackson
(1977), Snowdon (1992), Foster (2000), Smith (2002), and Martin
(2005).



This starting point gives rise to the following questions (cf. Martin
1998: 176):


1. The Objects Question: what is the nature of the direct
*objects* of experience?
2. The Structure Question: in what sense are experiences *directly
of* their objects?



Let's turn to the answers to these questions suggested by
Strawson and McDowell's remarks (for a more critical stance on
these remarks see Mackie (2020)).


### 1.2 Ordinary Objects



Strawson begins his argument by asking how someone might typically
respond to a request for a description of their current visual
experience. He says that it is natural to give the following kind of
answer: "I see the red light of the setting sun filtering
through the black and thickly clustered branches of the elms; I see
the dappled deer grazing in groups on the vivid green
grass..." (1979: 97). There are two ideas implicit in this
answer. First, the description talks about objects which are things
distinct from experience. Second, the description is
"rich", describing the nature of the experience not merely
in terms of simple shapes and colours; but in terms of the familiar
things we encounter in the "lived world" in all their
complexity (see also Heidegger (1977: 156)).



So, we can highlight the following answer to the Objects Question:


* **Ordinary Objects**: perceptual experiences are
directly of *ordinary mind-independent objects*.



There are three things to clarify about this. First, it incorporates
realism in that it appeals to the notion of a mind-independent object
of experience: one that doesn't depend for its existence upon
experience. Second, it concerns familiar or ordinary objects, things
that we admit as part of common-sense ontology. Third, "object
of experience" is understood broadly to encompass perceptible
entities in mind-independent reality including ordinary material
objects, but also features and other entities (e.g., events,
quantities of stuff). When we talk of "ordinary objects",
"the world" etc, we take this as shorthand for: familiar
or ordinary mind-independent perceptible entities.



Some writers have defended a thesis known as the transparency of
experience (see Harman (1990); Speaks (2009); Tye (1992, 1995, 2000);
Thau (2002); and for critical discussions, Martin (2002a), Smith
(2008), Stoljar (2004) and Soteriou (2013)).
**Transparency** is normally defined as the thesis that
introspecting what it is like for a subject to have an experience does
not reveal awareness of experiences themselves, but only of their
mind-independent objects. There are two claims here: (i) introspection
reveals the mind-independent objects of experience, and (ii)
introspection does not reveal any features of anything else.



**Transparency** is similar to **Ordinary
Objects**. The latter claim does involve something like (i).
But it does not involve (ii). And it is not obvious that (ii) is part
of our ordinary conception of perceptual experience. After all, we
readily admit that an ordinary scene (e.g., a snow-covered churchyard)
can look very different when one removes one's glasses:
one's visual experience then becomes blurred. But this
phenomenal difference does not seem to derive from any apparent
difference in the objects of experience. Rather, it seems to be a
difference in the way in which those objects are experienced. (See Tye
(2000) and Gow (2019) for different responses. For further discussion,
see Crane (2000), Smith (2008), Allen (2013), and French (2014). For a
different challenge to (ii) and its ilk see Richardson (2010) and
Soteriou (2013: Chapter 5), and French (2018)).


### 1.3 Presentation



What, then, about the Structure Question? Strawson speaks of the
manner in which we directly experience objects as a matter of
"immediate consciousness", and McDowell talks of our
"openness" to objects. Other notions commonly invoked here
include the idea that we are directly "acquainted" with
objects, we directly "apprehend" them, they are
"given" to us, or directly "present to the
mind". What these notions all aim to capture is the intuitive
idea that perceptual experience of an object involves a special
intimate perceptual relation to an object, a relation which
differentiates perceptual experiences from non-perceptual states of
mind which are similarly directed on the world (e.g., non-sensory,
non-perceptual thoughts).



One function of this relation is to make objects present in such a way
that they can shape or mould the character of one's experience.
In virtue of this, perceptions of the world are unlike
(non-perceptual) thoughts about the world: they are constrained by the
objects actually given. One's perception of a snow-covered
churchyard is responsive to how the churchyard is now, as one is
perceiving it. But one's (non-perceptual) thought need not be:
in the middle of winter, one can imagine the churchyard as it is in
spring, and one can think of it in all sorts of ways which are not the
ways it presently is.



In what follows we will use the notion of perceptual presentation to
capture this perceptual relation. We can thus highlight the following
answer to the structure question: 


* **Presentation**: perceptual experiences are direct
*perceptual presentations* of their objects.



In what follows, we use "direct presentation" for
short.


### 1.4 Direct Realism



Putting the pieces together, our ordinary conception of perceptual
experience involves:


* **Direct Realist Presentation**: perceptual
experiences are *direct perceptual presentations of ordinary
objects*.



If direct perceptual presentation of an ordinary object is a way of
directly perceiving it, then this gives us:


* **Direct Realism**: we can directly perceive ordinary
objects.


### 1.5 The Character of Experience



We can now shed light on the phenomenal character of perceptual
experience. Consider, then, the following question:


3. The Character Question: what determines the phenomenal character
of experience?



We began with the basic phenomenological observation that perceptual
experiences are directly of things. A similarly basic observation is
that what it is like for us to experience is at least partly a matter
of such things appearing certain ways to us. When we reflect upon what
determines what it is like to have an experience, we naturally begin
with what is presented to us, and how it is presented. This is why it
is so natural for Strawson to describe his experience in terms of what
he perceives, and for Martin to say that "our awareness of what
an experience is like is inextricably bound up with knowledge of what
is presented to one in having such experience" (1998: 173).



Further, when we reflect upon what determines what it is like for us
to experience, we naturally begin with the ordinary objects that are
presented to us, and how they are presented or appear. This is why it
is so natural for Strawson to describe his experience in terms of such
objects, and why many find (at least component (i) of) Transparency
intuitive.



So, we can highlight the following answer to the Character
Question:


* **Direct Realist Character:** the phenomenal
character of experience is determined, at least partly, by *the
direct presentation of ordinary objects.*


### 1.6 The Common Kind Claim



Perceptual experiences are not just veridical experiences: there are
illusions and hallucinations too. What does phenomenological
reflection say about how these cases relate to each other? More
specifically:


4. The Common Kind Question: are veridical, illusory, and
hallucinatory experiences fundamentally the same, do they form of a
*common kind*?



In the context of the Problem of Perception, these cases are usually
distinguished as follows: a veridical experience is an experience in
which an ordinary object is perceived, and where the object appears as
it is; an illusory experience is an experience in which an ordinary
object is perceived, and where the object appears other than it is; a
hallucination is an experience which seems to the subject exactly like
a veridical perception of an ordinary object but where there is no
such perceived or presented object. (For illusions and hallucinations
which don't fit these forms, see Johnston (2011), and Batty and
Macpherson (2016)).



Clearly, there are differences between these categories, but from a
phenomenological point of view, these experiences seem the same in at
least this sense: for any veridical perception of an ordinary object,
we can imagine a corresponding illusion or hallucination which cannot
be told apart or distinguished, by introspection, from the veridical
perception. This suggests the following answer to the Common Kind
Question:


* **Common Kind Claim:** veridical, illusory, and
hallucinatory experiences (as) of an F are fundamentally the same;
they form a *common kind*.



Thus, a veridical, illusory, and hallucinatory experience, all alike
in being experiences (as) of a churchyard covered in white snow, are
not merely superficially similar, they are fundamentally the same:
these experiences have the same nature, fundamentally the same kind of
experiential event is occurring in each case. Any differences between
them are external to their nature as experiences (e.g., to do with how
they are caused).


## 2. The Problem of Perception



The Problem of Perception is that if illusions and hallucinations are
possible, then perceptual experience, as we ordinarily understand it,
is impossible. The Problem is animated by two central arguments: the
argument from illusion (SS2.1) and the argument from hallucination
(SS2.2). (A similar problem arises with reference to other
perceptual phenomena such as perspectival variation or conflicting
appearances: see Burnyeat (1979) and the entry on sense-data). For
some classic readings on these arguments, see Moore (1905, 1910);
Russell (1912); Price (1932); Broad (1965); and Ayer (1940), see
Swartz (1965) for a good collection of readings. And for more recent
expositions see Snowdon (1992), Valberg (1992), Robinson (1994:
Chapter 2), Smith (2002: Chapters 1 and 7), Martin (2006), Fish (2009:
Chapter 2), Brewer (2011: Chapter 1) and Pautz (2021).



The two central arguments have a similar structure which we can
capture as follows:


1. In an illusory/hallucinatory experience, a subject is not directly
presented with an ordinary object.
2. The same account of experience must apply to veridical experiences
as applies to illusory/hallucinatory experiences.



Therefore,


3. Subjects are never directly presented with ordinary objects.



(C) contradicts Direct Realist Presentation, and thus our ordinary
conception of perceptual experience. And since Direct Realism seems to
follow from Direct Realist Presentation, the argument challenges
Direct Realism too (for more on this see
 SS3.2.6).



Representing the arguments in this basic form enables us to highlight
their two major movements; what Paul Snowdon calls the base case, and
the spreading step (1992, 2005). In the base case a conclusion about
just illusory/hallucinatory experiences is sought: (A). In the
spreading step, (B), this result is generalised so as to get (C). This
generalising move works on these background assumptions: (a1) that (B)
yields the claim that one is not directly presented with ordinary
objects in veridical experiences (given (A)), and (a2) if one is not
directly presented with such objects in even veridical experiences,
one never is.



We'll look at more complex versions of the argument shortly. As
we'll see, the main burden on the arguer from illusion is in
supporting the relevant version of (A), whereas the main burden on the
arguer from hallucination is in defending the relevant version of
(B).



Now, the argument here is purely negative. But many philosophers have
moved from this to the further conclusion that since we are always
directly presented with something in perceptual experience, what we
are presented with is a "non-ordinary" object (see
 SS3.1.2).


### 2.1 The Argument from Illusion



Applying the above structure, the argument from illusion is:


1. In illusory experiences, we are not directly presented with
ordinary objects.
2. The same account of experience must apply to veridical experiences
as applies to illusory experiences.



Therefore,


3. We are never directly presented with ordinary objects.



Moving beyond the simple formulation, the argument is typically
presented as involving these steps, for an arbitrary subject S:


1. In an illusion, it seems to S that something has a sensible
quality, F, which the ordinary object supposedly being perceived does
not have.
2. When it seems to S that something has a sensible quality, F, then
there is something directly presented to S which does have this
quality.
3. Since the ordinary object in question is, by hypothesis, not-F,
then it follows that in an illusion, S is not directly presented with
the ordinary object supposedly being perceived.
4. The same account of experience must apply to both veridical and
illusory experiences.



Therefore, 


5. In veridical experience, S is not directly presented with the
ordinary object supposedly being perceived.
6. If S is not directly presented with the ordinary object supposedly
being perceived in veridical experience, S is never directly presented
with an ordinary object.



Therefore,


7. We are never directly presented with ordinary objects.



The most controversial premise here is premise (ii). The others
reflect intuitive ways of thinking about perceptual experience, or
plausible assumptions. This is clear enough with (i) and (iv). Premise
(i) articulates the operative conception of illusions. An example to
illustrate is a case where a white wall looks yellow to you, in
peculiar lighting (Smith (2002: 25)). And premise (vi) reflects the
intuitive idea that if we aren't directly presented with the
ordinary objects we seem to perceive in veridical experiences, then we
aren't directly presented with ordinary objects at all. For it
would be implausible to relinquish the idea that we are directly
presented with the ordinary objects we seem to perceive in veridical
experience, yet maintain that we can still somehow else be directly
presented with ordinary objects, e.g., with the idea that
hallucinations are direct presentations of ordinary objects, or with
the idea that veridical experiences are direct presentations of
ordinary objects just not those we seem to perceive.



But what about (iv)? On one way of interpreting this, it reflects the
**Common Kind Claim** applied to veridical experiences
and illusions. Furthermore, various authors hold that (iv) is
supported by the continuity between veridical experiences and illusory
experience (Price (1932: 32), Ayer (1940: 8-9), Broad (1952: 9),
Robinson (1994: 57), Smith (2002: 26-28): the fact that they may form
a "continuous series" in which they "shade into one
another" (Ayer (1940: 8-9)). This, it is held, supports the idea
that experiential differences between illusions and veridical
perceptions are differences of "degree and not of kind"
(Ayer (1940: 8)).



Premise (ii) is a version of what Robinson calls the Phenomenal
Principle:



> 
> 
> If there sensibly appears to a subject to be something which possesses
> a particular sensible quality then there is something of which the
> subject is aware which does possess that sensible quality (1994: 32).
> 
> 
> 
> 



C.D. Broad motivates this principle on explanatory grounds. In cases
of perceptual experience things appear some ways rather than others to
us. We need to explain this. Why does the penny look elliptical to you
as opposed to some other shape? One answer is that there is something
directly presented to you which is in fact elliptical. Thus, as Broad
says "If, in fact, nothing elliptical is before my mind, it is
very hard to understand why the penny should seem elliptical rather
than of any other shape." (1923: 240). Other philosophers have
simply taken the principle to be obvious. H.H. Price, for example,
says that "When I say 'this table appears brown to
me' it is quite plain that I am acquainted with an actual
instance of brownness" (1932: 63).



So much for the argument's main premises. How is it supposed to
work? Here we find the suggestion that it hinges on an application of
Leibniz's Law of the Indiscernibility of Identicals (Robinson
(1994: 32); Smith (2002: 25)). The point is that (i) and (ii) tell us
that in an illusory experience you are directly presented with an F
thing, but the ordinary object supposedly being perceived is not F,
thus the F thing and the ordinary object are not identical, by
Leibniz's Law. On these grounds, the conclusion of the base case
is supposed to follow. And then the ultimate conclusion of the
argument can be derived from its further premises.



But as French and Walters (2018) argue, this is invalid. (i), (ii) and
Leibniz's Law entail that in an illusory experience you are
directly presented with an F thing which is non-identical to the
ordinary object supposedly being perceived. However, this
doesn't entail that in the illusion you are not directly
presented with the ordinary object. You might be directly presented
with the ordinary object as well as the F thing. We should be careful
to distinguish not being directly presented with the ordinary object
from being directly presented with something which is not the ordinary
object (e.g., between not being directly presented with the white
wall, and being directly presented with something that is not the
white wall, e.g., a yellow entity). The argument is invalid in
conflating these two ideas.



One option for fixing the argument is to introduce what French and
Walters call the **Exclusion Assumption** (cf., Snowdon
(1992: 74)): If in an illusion of an ordinary object as F, a subject
is directly presented with an F thing non-identical to the ordinary
object, then they are not also directly presented with the ordinary
object. 



This assumption bridges the gap between the conclusion actually
achieved: namely, in an illusory experience S is directly presented
with an F thing non-identical to the ordinary object, and the desired
conclusion (iii). But whether this assumption is defensible remains to
be seen. We leave this and the issue of validity aside and consider
responses from different theories of experience below.


### 2.2 The Argument From Hallucination



The argument from hallucination relies on the possibility of
hallucinations as understood above. Such hallucinations are not like
real drug-induced hallucinations or hallucinations suffered by those
with certain mental disorders. They are rather supposed to be merely
possible events. For example, suppose you are now having a veridical
perception of a snow-covered churchyard. The assumption that
hallucinations are possible means that you could have an experience
which is subjectively indistinguishable--that is,
indistinguishable by you, "from the inside"--from a
veridical perception of a snow-covered churchyard, but where there is
in fact no churchyard presented or there to be perceived. The claim
that such hallucinations are possible is widely accepted but not
indisputable (see Austin (1962) and Masrour (2020)). For more on
hallucinations, see Macpherson and Platchias (2013).



The argument from hallucination runs as follows:


1. In hallucinatory experiences, we are not directly presented with
ordinary objects
2. The same account of experience must apply to veridical experiences
as applies to hallucinatory experiences.



Therefore,


3. We are never directly presented with ordinary objects.



Unlike with the argument from illusion, the base case doesn't
rely on the **Phenomenal Principle:** (A) simply falls
out of what hallucinations are supposed to be.



The spreading step can be interpreted in terms of the **Common
Kind Claim**, applied to veridical experiences and
hallucinations. Accepting (B) understood in this way puts a constraint
on what can be said about the nature of veridical experience: whatever
can be said had better be able to apply to hallucinations too. The
argument is that, given (A), this then rules out an account of
veridical experiences as direct presentations of ordinary objects. But
then (C) follows (given that if we are not directly presented with
ordinary objects in veridical experience, we never are).



With the argument understood in this way, we can see the power of the
Problem of Perception. (A) is intuitive, and (B) is part of our
ordinary conception of perceptual experience, yet what follows, (C),
contradicts another aspect of our ordinary conception (**Direct
Realist Presentation**). Thus, the very intelligibility of our
ordinary conception of perceptual experience is threatened.



Now it might be argued that the **Common Kind Claim**
applied to veridical perceptions and hallucinations is not as
plausible as it is when applied to veridical perceptions and
illusions. For veridical and illusory experiences are more naturally
grouped together anyway, unlike veridical perceptions and
hallucinations. For, at least before we encounter the argument from
illusion, veridical perceptions and illusions are both naturally
thought of as direct presentations of ordinary objects (it's
just that in illusory cases the presented objects appear other than
they are). However, as noted above, from a *phenomenological*
point of view, hallucinations too seem as though they are direct
presentations of ordinary objects: *from the subject's
perspective* a hallucination as of an F cannot be distinguished
from a veridical experience of an F. This is why it seems so plausible
to think of them as fundamentally the same.



Even so, the **Common Kind Claim** applied to veridical
perceptions and hallucinations is controversial, and rejecting it is
central to the *disjunctivist* response to the Problem of
Perception that we will consider later
 (SS3.4).


## 3. Theories of Experience



A number of philosophical theories of experience have emerged as
responses to the Problem of Perception, or in relation to such
responses. Here we consider the sense-datum theory
 (SS3.1),
 adverbialism
 (SS3.2),
 intentionalism
 (SS3.3),
 and naive realist disjunctivism
 (SS3.4).
 In this exposition we do not consider much the possibility of hybrid
views. The way these positions relate to the Problem of Perception is
mapped most clearly in Martin (1995, 1998, 2000).



We present these theories as operating on two levels. On Level 1, they
tell us about the nature of experience. With the exception of
adverbialism (for reasons that will emerge shortly), this can be
investigated by considering the stance of each theory on the nature of
the objects of experience, and the structure of our experience of
objects. On Level 2, they tell us how what is said at the first level
bears on the explanation of the character of experience. We also
consider how each theory addresses the common kind question.



In what follows, we'll work with the example of a visual
experience of a snow-covered churchyard. To simplify, we will discuss
the character of this experience in terms of one aspect of it: things
looking white to a subject. The question at Level 1 is: what is the
nature of such an experience? Does it involve the direct presentation
of objects, or not? If so, what sorts of objects? If not, how are we
to understand the nature of this experience? The question at Level 2
is: what is it about the nature of this experience that explains why
things look any way at all to someone, and why they look,
specifically, white?


### 3.1 The Sense-Datum Theory


#### 3.1.1 The Sense-Datum Theory in Outline



What does the sense-datum theorist say at Level 1? On this theory,
whenever a subject has a sensory experience, there is something which
is presented to them. This relational conception of experience is
sometimes called an "act-object" conception, since it
posits a distinction between the mental act of being presented with
something, and the object presented. More precisely, the sense-datum
theorist holds that an experience in which something appears F to S,
where F is a sensible quality (e.g., whiteness), consists in S being
directly presented with something which actually is F (e.g. a white
thing). They thus endorse the aforementioned **Phenomenal
Principle**. The sense-datum theorist calls these objects of
perception "sense-data".



Understood in this way, a sense-datum is just *whatever* it is
that you are directly presented with that instantiates the sensible
qualities which characterise the character of your experience. This
involves no further claim about the *nature* of sense-data,
though as we'll see shortly, sense-datum theorists do go on to
make further claims about the nature of sense-data.



What about Level 2? With respect to our example, the sense-datum
theorist claims that things appearing any way at all to you consists
in the fact that you are directly presented with a sense-datum, and
things appearing white to you consists in the fact that you are
directly presented with a white sense-datum. The character of your
experience is explained by an actual instance of whiteness manifesting
itself in experience.



The sense-datum theorist endorses the **Common Kind
Claim**. So, a veridical experience in which something appears
white to you consists in your being directly presented with a white
sense-datum; but so do corresponding illusory and hallucinatory
experiences. These experiences have the same nature.


#### 3.1.2 The Sense-Datum Theory and the Problem of Perception



The sense-datum theorist endorses the following negative claim:


1. We are never directly presented with ordinary objects.



They accept this on the basis of the arguments from illusion and
hallucination. However, the intended contrast with Direct Realist
Presentation usually involves a stronger claim:


2. We are only ever directly presented with *sense-data*,
which are non-ordinary objects.



This involves a positive claim about what we *are* directly
presented with, given that we are never directly presented with
ordinary objects. And it embeds a claim about the nature of sense-data
that goes beyond that outlined above: now sense-data are understood as
*non-ordinary* objects.



Sense-datum theorists divide over exactly how to understand sense-data
insofar as they are non-ordinary. Some early sense-datum theorists
(such as Moore) initially took sense-data to be mind-independent, but
peculiar non-physical objects. Later theorists treat sense-data as
mind-dependent entities (Robinson (1994)). This is how the theory
tends to be understood in literature from second half of the 20th
century on. 



Sense-datum theorists have developed more positive Problem of
Perception style reasoning to support these additional ideas. For
instance, Macpherson (2013: 12-13) outlines a more complicated version
of the argument from hallucination than that above which concludes
that "All perceptual experience, hallucinatory and
non-hallucinatory, involves awareness of a mind-dependent, nonphysical
object--a sense-datum". And some sense-datum theorists have
attempted to support non-ordinary sense-data outside of the context of
the Problem of Perception (see Jackson (1977) and Lowe (1992)).



From now on when we speak of "sense-data" we will mean
non-ordinary sense-data, and when we speak of the "sense-datum
theory" we have in mind a theory that endorses not just (1) but
(2).


#### 3.1.3 The Sense-Datum Theory and Our Ordinary Conception of Perceptual Experience



The sense-datum theorist agrees with some aspects of our ordinary
conception of perceptual experience. They endorse the **Common
Kind Claim**. They also endorse **Presentation**
- the idea that the direct objects of experience are
perceptually presented to us. It's just that they don't
agree that the direct objects of experience are ordinary objects
- they are non-ordinary sense-data. They thus reject
**Ordinary Objects**, and hence **Direct Realist
Presentation**, and **Direct Realist
Character**.


#### 3.1.4 The Sense-Datum Theory and Perception of the World



Is the sense-datum theory a theory on which we completely lose contact
with the world, a theory on which we cannot perceive the world?



Though it is possible for a sense-datum theorist to accept this, a
more popular position has been one on which we still have some form of
perception of the world, just not direct perception. That is, the
sense-datum theorist can say that we indirectly perceive ordinary
objects: we perceive them by being directly presented with sense-data.
A sense-datum theorist who says this is known as an indirect realist
or representative realist (see the entry on
 epistemological problems of perception).
 The task for such a sense-datum theorist is to spell out how the
direct presentation of sense-data can lead to indirect perception of
ordinary objects. This is something early sense-datum theorists
pursued by asking how sense-data are related to ordinary objects. A
theorist who denies that we perceive mind-independent objects at all,
directly or indirectly, but only sense-data construed as mental
entities, is known as a phenomenalist or an idealist (see Foster
(2000), see Crane and Farkas (2004: Section 2) for an introduction to
the subject; and the entry on
 idealism).


#### 3.1.5 Objections to the Sense-Datum Theory



The sense-datum theory was widely rejected in the second half of the
20th century, though it still had its occasional champions (e.g.,
Jackson (1977), O'Shaughnessy (2000, 2003), Lowe (1992),
Robinson (1994), Foster (2000)). A number of objections have been made
to the theory. Some of these are objections specifically to the
indirect realist version: for example, the claim that the theory gives
rise to an unacceptable "veil of perception" between mind
and world. The idea is that sense-data "interpose"
themselves between perceivers and ordinary objects, and therefore
problematise our perceptual, cognitive, and epistemic access to the
world. In response, the indirect realist can say that sense-data are
the medium by which we perceive ordinary objects, and no more create a
"veil of perception" than the fact that we use words to
talk about things creates a "veil of words" between us and
what we talk about. (For recent discussion see Silins (2011)).



A common objection is to attack the **Phenomenal
Principle** (see Barnes (1944-5); Anscombe (1965)). The
objection is that the **Phenomenal Principle** is
fallacious. It is not built into the meaning of "something
appears F to one" that "one is directly presented with an
F thing". Defenders of the sense-datum theory can respond that
the Phenomenal Principle is not supposed to be a purely*logical* inference; it is not supposed to be true simply because
of the logical form or semantic structure of "appears" and
similar locutions. Rather, it is true because of specific
phenomenological facts about perceptual experience. But this just
means that theorists who reject the Phenomenal Principle are not
disagreeing about whether the Phenomenal Principle involves a fallacy
or about some semantic issue, but rather about the nature of
experience itself.



Another influential objection to sense-data comes from the prevailing
naturalism of contemporary philosophy. Naturalism (or physicalism)
says that the world is entirely physical in its nature: everything
there is supervenes on the physical, and is governed by physical law.
Many sense-datum theorists are committed to the claim that
non-ordinary sense-data are mind-dependent: objects whose existence
depends on the existence of states of mind. Is this consistent with
naturalism? If so, the challenge is to explain how an object can be
brought into existence by the existence of an experience, and how this
is supposed to be governed by physical law.



Many contemporary sense-datum theorists, however, will not be moved by
this challenge, since they are happy to accept the rejection of
naturalism as a consequence of their theory (Robinson (1994), Foster
(2000)). On the other hand, one might think that there is no conflict
here with naturalism, as long as experiences themselves are part of
the natural order. But if sense-data are non-ordinary in being
mind-independent but *non-physical*, then it is much less clear
how naturalism can be maintained (cf., what Martin (2004, 2006) calls
"experiential naturalism" which serves as a constraint on
theories of experience and rules out some but not all forms of the
sense-datum theory).



For other objections to the sense-datum theory, including the worry
that it must admit "indeterminate" sense-data (e.g., on
the basis of seeing a speckled hen, which appears to have a number of
speckles but no definite number), see the entry on
 sense-data.


### 3.2 Adverbialism


#### 3.2.1 Adverbialism in Outline



Part of the point of adverbialism, as defended by Ducasse (1942) and
Chisholm (1957) is to do justice to the phenomenology of experience
whilst avoiding the dubious metaphysical commitments of the
sense-datum theory. The only entities which the adverbialist needs to
acknowledge are subjects of experience, experiences themselves, and
ways these experiences are modified. Let us explain.



At Level 1, the adverbialist rejects the **Phenomenal Principle**and the whole idea that experience consists in being directly
presented with perceptible entities. For the adverbialist, when
someone has an experience of something white, something like whiteness
is instantiated, but in the experience itself, not a presented thing.
This is not to say that the experience is white, but rather that the
experience is *modified in a certain way*, the way we can call
"perceiving whitely". The canonical descriptions of
perceptual experiences, then, employ adverbial modifications of the
perceptual verbs: instead of describing an experience as
someone's "visually sensing a white sphere", the
theory says that they are "visually sensing whitely and
spherely". This is why this theory is called the
"adverbial theory"; but it is important to emphasize that
it is more a theory about the nature of experience itself than it is a
semantic analysis of sentences describing experience.



It is also intended as a theory of the character of experience (Level
2). The adverbialist claims that things appearing white to you
consists in you *sensing whitely*. It is because you are
sensing in *some way* that explains why things appear a certain
way to you at all, and it is the fact that you are sensing
*whitely* that explains why things appear *white* to
you, rather than some other way. The character of your experience is
explained by the specific "white" way in which your
experience is modified.



The adverbialist endorses the **Common Kind Claim**. So,
a veridical experience in which something appears white to you,
consists in you sensing whitely, but so do corresponding illusory and
hallucinatory experiences: these experiences have the same nature.


#### 3.2.2 Adverbialism and Qualia



When used in a broad way, "qualia" picks out whatever
qualities a state of mind has which constitute the state of
mind's having the phenomenal character it has. In this broad
sense, any phenomenally conscious state of mind has qualia. (This is
the way the term is used in, e.g., Chalmers (1996)). Used in a narrow
way, however, qualia are non-intentional, intrinsic properties of
experience: properties which have no intentional or representational
aspects whatsoever. To use Gilbert Harman's apt metaphor, qualia
in this sense are "mental paint" properties (1990). Harman
rejects mental paint, but the idea of experience as involving mental
paint is defended by Block (2004)).



It is relatively uncontroversial to say that there are qualia in the
broad sense. It can be misleading, however, to use the term in this
way, since it can give rise to the illusion that the existence of
qualia is a substantial philosophical thesis when in fact it is
something which will be accepted by anyone who believes in phenomenal
character. (Hence Dennett's (1991) denial of qualia can seem
bewildering if "qualia" is taken in the broad sense). It
is controversial to say that there are qualia in the narrow sense,
though, and those who have asserted their existence have therefore
provided arguments and thought-experiments to defend this assertion
(see Block (1997), Peacocke (1983: Chapter 1), Shoemaker (1990)). In
what follows, "qualia" will be used exclusively in the
narrow sense.



As noted, adverbialism is committed to the view that experiencing
something white, for example, involves your experience being modified
in a certain way: experiencing whitely. A natural way to understand
this is in terms of the idea that the experience is an event, and the
modification of it is a property of that event. Since this property is
both intrinsic (as opposed to relational or representational) and
phenomenal then this way of understanding adverbialism is committed to
the existence of qualia.


#### 3.2.3 Objections to Adverbialism



An important objection to adverbialism is the "Many Property
Problem" proposed by Frank Jackson (1975). Consider someone who
senses a brown square and a green triangle simultaneously. The
adverbialist will characterize this state of mind as "sensing
brownly and squarely and greenly and triangularly". But how can
they distinguish the state of mind they are describing in this way
from that of sensing a brown triangle and a green square? The
characterization fits that state of mind equally well. Obviously, what
is wanted is a description according to which the brownness
"goes with" the squareness, and the greenness "goes
with" the triangularity. But how is the adverbialist to do this
without introducing objects of experience--the things which are
brown and green respectively--or a visual field with a spatial
structure? The challenge is whether the adverbialist can properly
account for the spatial structure and complexity in what is given in
visual experience. See Tye (1984), Breckenridge (2018: Chapter 10),
and D'Ambrosio (2019) for adverbialist responses to this
challenge. For a helpful overview, see Fish (2010: Chapter 3).



A further challenge is that adverbialism is "incapable of doing
justice to the most obvious and indeed essential phenomenological fact
about perceptual consciousness... namely... its
object-directness" (Butchvarov (1980: 272)). Recall here the
basic phenomenological observation we began with: perceptual
experiences are directly of things.



As we've seen, at Level 1, the adverbialist denies that
perceptual experiences are direct presentations of objects. And at
Level 2, in explaining character, the adverbialist assigns no role to
the direct presentation of things, just ways of sensing. But then if
it is an aspect of the phenomenology of experience that our
experiences have direct objects, then it is not clear that the
adverbialist has the resources to capture this. For the adverbialist,
to capture your experience of a snow-covered churchyard we invoke
seeing whitely not seeing a white *thin*g. How, then, can we
explain why *phenomenologically*, your experience is directly
of a white thing - or even why it seems to be object-directed in
this way? Butchvarov's charge is that the adverbialist
doesn't have the resources to answer these questions. (See
D'Ambrosio (2019) for a recent adverbialist attempt to capture
something like object-directness).


#### 3.2.4 Adverbialism and the Problem of Perception



The argument from illusion relies on the **Phenomenal
Principle**. In rejecting this, the adverbialist thus rejects
the argument. But what about the argument from hallucination? This
does not rely on the Phenomenal Principle. The adverbialist accepts
(A). And they also accept (B) in the form of the **Common Kind
Claim**. (C) follows (given assumptions (a1) and (a2)). For
this reason, the adverbialist must reject **Direct Realist
Presentation**. So, like the sense-datum theorist, the
adverbialist must admit that we are never directly presented with
ordinary objects, not even in veridical experience.


#### 3.2.5 Adverbialism and our Ordinary Conception of Perceptual Experience



Like the sense-datum theorist, though the adverbialist accepts some of
our ordinary conception of perceptual experience (the **Common
Kind Claim**), they reject other aspects of it. The argument
from hallucination forces them to reject **Direct Realist
Presentation** (and therefore **Direct Realist
Character**). Underlying this is the adverbialist's
rejection of **Presentation**, and arguably
**Ordinary Objects** too. They reject
**Presentation** in denying that experiences have a
relational structure. And given our discussion of Butchvarov's
challenge, it seems as though they must reject (or at least
don't have the resources to accept) **Ordinary
Objects**. For it is unclear how they can validate the
phenomenological claim that experiences are of objects, let alone
directly of ordinary objects.



So, even though adverbialism arises as a response to the sense-datum
theory, given its almost wholesale rejection of our ordinary
conception of perceptual experience, it is unclear how much of an
improvement the approach is in the broader dialectic of the Problem of
Perception.


#### 3.2.6 Adverbialism and Perception of the World



One response to this is that we should not suppose that the only way
to articulate direct realism is through the claim we've labelled
**Direct Realist Presentation**. There is another way to
articulate it which, it might be suggested, enables the adverbialist
to account for direct perception of the world. Consider, then:


* **Direct Realist Presentation**: perceptual
experiences are direct perceptual presentations of ordinary
objects.



This entails **Direct Realism** - that we can
directly perceive ordinary objects - on the assumption that
being directly perceptually presented with an ordinary object is a way
of directly perceiving it. On this way of thinking, direct perception
of an ordinary object is built into perceptual experience itself.
However, one might reject this claim about experience (as
adverbialists do), and still hold that we can have direct perception
of an ordinary object. How?



Instead of thinking of direct perception of the world as built
*into* experience, we can think of direct perception of the
world as built *out of* experience together with the
satisfaction of other conditions. This idea is usually developed
through a *causal theory of perception* (Grice 1961): where
perception of an object is analysed in terms of (i) experience of an
ordinary object (conceived as something which is not sufficient for
perception), and (ii) the satisfaction of a causal condition which
requires that the experience be caused by the object (in a non-deviant
way). This is a causal theory of *direct* perception on the
assumption that the account doesn't involve any perceptual
intermediaries.



The adverbialist might suggest that they can embrace this: by
combining their theory of *experience* with a causal analysis
of direct perception. Thus, they can hold that when you have an
experience of a snow-covered churchyard, if this experience is
appropriately caused by an ordinary white thing (e.g., some snow),
this is what directly perceiving such an object amounts to (given that
no perceptual intermediaries are involved).



However, whether the adverbialist is entitled to this way of making
sense of direct perceptual contact with the world hinges on whether
they can make sense of the idea of an experience *of an ordinary
object*. But as we have seen in considering Butchvarov's
challenge, it is unclear whether the adverbialist can do this. It is
thus unclear whether the adverbialist can really make sense of clause
(i).



In response, the adverbialist might offer a causal analysis of
experiences being of objects. They might thus attempt to fall back on
the idea that an experience in which you sense whitely is an
experience "of" a white thing insofar as it is causally
related to a white thing (or, insofar as it is of a type, instances of
which are typically caused by white things). However, as Butchvarov
argues, the fact that "x is causally related to S's
sensing in a certain way can no more reasonably be described as
S's being conscious of [i.e. having a conscious experience of] x
than the fact that the presence of carbon monoxide in the air is
causally related to S's having a headache can be described as
S's being conscious of [having a conscious experience of] carbon
monoxide" (1980: 273).



Even if the adverbialist *is* able to sustain such a causal
form of direct realism, it is very different from the phenomenological
form of direct realism embedded in our ordinary conception of
perceptual experience. It is thus unlikely to satisfy a direct realist
sensitive to the phenomenological concerns which give rise to our
ordinary conception of perceptual experience.


### 3.3 Intentionalism


#### 3.3.1 Intentionalism in Outline



The intentionalist holds that we directly experience ordinary objects.
The distinguishing feature of the view is a specific conception of the
manner in which experiences are directly of ordinary objects: here the
intentionalist appeals to intentionality conceived of as a form of
mental representation (hence it is also sometimes called the
representationalist theory of experience).
"Intentionality" is a term with its origins in scholastic
philosophy (see Crane (1998b)), but its current use derives from
Brentano (1874), who introduced the term "intentional
inexistence" for the "mind's direction upon its
objects". Intentional inexistence, or intentionality, is
sometimes explained as the "aboutness" of mental states
(see the entries on
 Franz Brentano,
 representational theories of consciousness and
 intentionality).



At Level 1, then, the intentionalist holds that to experience a
snow-covered churchyard is to *directly perceptually represent*
such an object (i.e. to represent such an object but not in virtue of
representing another more "immediate" object). At Level 2,
this is put to work in explaining phenomenal character. In relation to
our example, why is this a case of things appearing any way at all to
you, and why is it a case of things appearing white to you? Here the
intentionalist appeals to the experience's directly representing
things in a certain way, and specifically to experience's
directly representing whiteness in the environment, to account for
this. The character of your experience is explained by the specific
way in which your experience directly represents the world.



Critics of intentionalism have argued that it does not adequately
distinguish perceptual experience from other forms of intentionality,
and therefore does not manage to capture what is distinctive about
experience (Robinson (1994: 164)). One objection of this kind is that
the aforementioned intentionalist explanation of character is
inadequate. The worry is that believing that something is the case,
for example, or hoping that something is the case, are both forms of
mental representation, but neither state of mind has any
"feel" or phenomenal character to call its own. (Words or
images may come to mind when mentally representing something in this
way, but it is not obvious that these are essential to the states of
mind themselves.) So, the challenge is that if there is nothing about
representation as such which explains the character of an experience,
how is experience supposed to be distinguished from mere thought?



There are a number of ways an intentionalist can respond. One is
simply to take it as a basic fact about perceptual intentionality that
it has phenomenal character (see Kriegel (2013)). After all, even
those who believe in qualia have to accept that some states of mind
have qualia and some do not, and that at some point the distinction
between mental states which are phenomenally conscious, and those
which are not, just has to be accepted as a brute fact. Another
response is to say that in order to fully explain the phenomenal
character of perceptual experience, we need to treat experience as
involving non-intentional qualia as well as intentionality (see
Peacocke (1983: Chapter 1); Shoemaker (1996); Block (1997)). There is,
accordingly, a dispute between these intentionalists who accept qualia
(like Block and Shoemaker) and those who don't (like Harman
(1990) or Tye (1992)). (For more on this see the entries on
 qualia
 and
 inverted qualia.
 Additional readings are: Block (2005) (2010), Egan (2006), Hilbert
and Kalderon (2000), Marcus (2006), Shoemaker (1990), Speaks (2015),
Spener (2003), and Tye (2000)).



Intentionalists endorse the **Common Kind Claim**. So, a
veridical experience of churchyard covered in white snow, consists in
direct representation of such a scene, but so do corresponding
illusory and hallucinatory experiences: these experiences have the
same nature.



Like adverbialists, the intentionalist has no need to postulate
non-ordinary perceptible entities in the cases of illusion and
hallucination. It is not generally true that when a representation
represents something (as being F), there has to actually be something
(which is F). Thus, for the intentionalist, experience is
representational in a way that contrasts with it being
relational/presentational. Experience does not genuinely have an
act-object structure. This is in keeping with a standard tradition in
the theory of intentionality which treats it as non-relational (the
tradition derives from Husserl (1900/1901); for discussion see Zahavi
(2003: 13-27). So, for the intentionalist, since it is not of
the essence of experience or its character that it is relational, it
is not of its essence that it is a relation to a sense-datum.


#### 3.3.2 Sources of Intentionalism



Some of the most influential (at least partial) intentional theories
are Anscombe (1965), Armstrong (1968), Pitcher (1970), Peacocke
(1983), Harman (1990), Tye (1992, 1995), Dretske (1995), Lycan (1996);
for more recent accounts, see Byrne (2001), Siegel (2010), Pautz
(2010) and the entry on
 the contents of perception.



Within analytic philosophy, intentionalism is a generalisation of an
idea presented by G.E.M. Anscombe (1965), and the "belief
theories" of D.M. Armstrong (1968) and George Pitcher (1970).
(Within the phenomenological tradition intentionality and perception
had always been discussed together: see the entry on
 phenomenology.)
 Anscombe had drawn attention to the fact that perceptual verbs
satisfy the tests for non-extensionality or intensionality (see the
entry on
 intensional transitive verbs).
 For example, just as 'Vladimir is thinking about Pegasus'
is an intensional context, so 'Vladimir has an experience as of
a pink elephant in the room' is an intensional context. In
neither case can we infer that there exists something Vladimir is
thinking about, or that there is exists something he is experiencing.
This is the typical manifestation of intensionality. Anscombe regarded
the error of sense-datum and naive realist theories as the failure to
recognise this intensionality. (Her own example was the alleged
intensionality of 'see', but this is controversial.)



Armstrong and Pitcher argued that perception is a form of belief.
(More precisely, they argued that it is the acquisition of a belief,
since an acquisition is a conscious event, as perceiving is; rather
than a state or condition, as belief is.) Belief is an intentional
state in the sense that it represents the world to be a certain way,
and the way it represents the world to be is said to be its
intentional content. Perception, it was argued, is similarly a
representation of the world, and the way it represents the world to be
is likewise its intentional content. The fact that someone can have a
perceptual experience of something as F, without there being any thing
which is F was taken as a reason for saying that perception is just a
form of belief-acquisition.



Certain cases put pressure on this. For instance, consider the famous
Muller-Lyer illusion in which two lines of equal length look
unequal. You can experience this even if you know (and therefore
believe) that the lines are the same length. If perception were simply
the acquisition of belief, then this would be a case of explicitly
contradictory beliefs: you believe that the lines are the same length
and that they are different lengths. But this is surely not the right
way to describe this situation. (Armstrong recognized this, and
re-described perception as a "potential belief"; this
marks a significant retreat from the original claim).



The belief theory (and related theories, like the judgement theory of
Craig (1976)) is a specific version of the intentional theory. But it
is not the most widely accepted version (though see Gluer (2009)
for a recent defence; and Byrne (forthcoming)). Intentionalism is,
however, not committed to the view that perceptual experience is
belief; experience can be a *sui generis* kind of intentional
state or event (Martin (1993)).


#### 3.3.3 The Intentional Content of Perceptual Experience



Intentionalists hold that what is in common between veridical
experiences and indistinguishable hallucinations/illusions is their
*intentional content*: roughly speaking, how the world is
represented as being by the experiences. Many intentionalists hold
that the sameness of phenomenal character in perception and
hallucination/illusion is exhausted or constituted by this sameness in
content (see Tye (2000), Byrne (2001)). But this latter claim is not
essential to intentionalism (see the discussion of intentionalism and
qualia above). What is essential is that the intentional content of
perception explains (whether wholly or partly) its phenomenal
character.



The intentional content of perceptual experience is sometimes called
"perceptual content" (see the entry on
 the contents of perception).
 What is perceptual content? A standard approach to intentionality
treats all intentional states as propositional attitudes: states which
are ascribed by sentences of the form "S \_\_\_ that p" where
'S' is to be replaced by a term for a subject,
'p' with a sentence, and the '\_\_\_' with a
psychological verb. The distinguishing feature of the propositional
attitudes is that their content--how they represent the world to
be--is something which is assessable as true or false. Hence the
canonical form of ascriptions of perceptual experiences is: "S
perceives/experiences that p". Perceptual experience, on this
kind of intentionalist view, is a propositional attitude (see Byrne
(2001), Siegel (2010)).



But intentionalism is not committed to the view that experience is a
propositional attitude. For one thing, it is controversial whether all
intentional states are propositional attitudes (see Crane (2001:
Chapter 4)). Among the intentional phenomena there are relations like
love and hate which do not have propositional content; and there are
also non-relational states expressed by the so-called
"intensional transitive" verbs like seek, fear, expect
(see the entry on
 intensional transitive verbs).
 All these states of mind have contents which are not, on the face of
it, assessable as true or false. If I am seeking a bottle of
inexpensive Burgundy, what I am seeking--the intentional content
of my seeking, or the intentional object under a certain mode of
presentation--is not something true or false. Some argue that
these intentional relations and intentional transitives are analysable
or reducible to propositional formulations (see Larson (2003) for an
attempt to defend this view of intensional transitives; and Sainsbury
(2010) for a less radical defence). But the matter is controversial;
and it is especially controversial where experience is concerned. For
we have many ways of talking about experience which do not
characterize its content in propositional terms: for example,
"Vladimir sees a snail on the grass", or "Vladimir
is watching a snail on the grass" can be distinguished from the
propositional formulation "Vladimir sees that there is a snail
on the grass" (for discussion of watching, see Crowther
2009).



There are those who follow Dretske (1969) in claiming that these
semantical distinctions express an important distinction between
"epistemic" and "non-epistemic" seeing.
However, the view that perceptual content is non-propositional is not
the same as the view that it is "non-epistemic" in
Dretske's sense. For ascriptions of non-epistemic seeing are
intended to be fully extensional in their object positions, but not
all non-propositional descriptions of perception need be (for example,
some have argued that "Macbeth saw a dagger before him"
does not entail "there is a dagger which Macbeth saw": cf.
Anscombe (1965)). The question of whether perceptual experience has a
propositional content is far from being settled, even for those who
think it has intentional content (see McDowell (2008); Crane
(2009)).



Another debate about the content of perceptual experience is whether
it is object-dependent, or object-independent (see Soteriou (2000) and
Schellenberg (2018: Part II); and for a more general discussion, see
Chalmers (2006)). An object-dependent content is a content which
concerns a particular object, and is such that it cannot be the
content of a state of mind unless that object exists (McDowell (1987)
and Brewer (1999)). An object-independent content is one whose ability
to be the content of any intentional state is not dependent on the
existence of any particular object (Davies (1992) and McGinn
(1989)).



The intentionalist holds that the content that is common to veridical
experiences and subjectively indistinguishable hallucinations is
object-independent: since such hallucinations occur in the absence of
objects for such content to depend upon. However, as Martin (2002b)
argues, drawing on (Burge 1991), the intentionalist can still appeal
to the idea that *particular* veridical experiences have
particular object-dependent contents in addition to the
object-independent contents they share with subjectively
indistinguishable hallucinations.



The objects of intentional states are sometimes called
"intentional objects" (Crane (2001: Chapter 1)). What are
the intentional objects of perceptual experience, according to
intentionalists? In the case of veridical perception, the answer is
simple: ordinary objects like the churchyard, the snow etc. But what
should be said about the hallucinatory case? Since this case is by
definition one in which there is no ordinary object being perceived,
how can we even talk about something being an "object of
experience" here? As noted above, intentionalists say that
experiences are representations; and one can represent what does not
exist (see Harman (1990), Tye (1992)). This is certainly true; but
isn't there any more to be said? For how does a representation
of a non-existent churchyard differ from a representation of a
non-existent cat, say, when one of those is hallucinated? The states
seem to have different objects; but neither of these objects exist
(see the entry
 nonexistent-objects).



One proposal is that the objects of hallucinatory experience are the
properties which the hallucinated object is presented as having
(Johnston (2004)). Another answer is to say that these hallucinatory
states of mind have intentional objects which do not exist (Smith
(2002: Chapter 9)). Intentional objects in this sense are not supposed
to be entities or things of any kind. When we talk about perception
and its "objects" in this context, we mean the word in the
way it occurs in the phrase "object of thought" or
"object of attention" and not as it occurs in the phrase
"physical object". An intentional object is always an
object for a subject, and this is not a way of classifying things in
reality. An intentionalist need not be committed to intentional
objects in this sense; but if they are not, then they owe an account
of the content of hallucinatory experiences.



How does the content of perceptual experience differ from the content
of other intentional states? According to some intentionalists, one
main difference is that perception has "non-conceptual"
content. The basic idea is that experience involves a form of mental
representation which is in certain ways less sophisticated than the
representation involved in (say) belief. For example, having the
belief that the churchyard is covered in snow requires that you have
the concept of a churchyard. This is what it means to say that belief
has conceptual content: to have the belief with the content that a is
F requires that you possess the concept a and the concept F. So, to
say that experience has non-conceptual content is to say the
following: for you to have an experience with the content that a is F
does not require that you have the concept of a and the concept F. The
idea is that your perceptual experience can represent the world as
being a certain way--the "a is F" way--even if
you do not have the concepts that would be involved in believing that
a is F. (For a more detailed version of this definition, see Crane
(1998a) and Cussins (1990); for a different way of understanding the
idea of non-conceptual content, see Heck (2000) and Speaks (2005). The
idea of non-conceptual content derives from Evans (1982); there are
some similar ideas in Dretske (1981); see Gunther (2002) for a
collection of articles on this subject. Other support for
non-conceptual content can be found in Bermudez (1997);
Peacocke (1992); Crowther (2006); for opposition see Brewer (1999) and
McDowell (1994)).


#### 3.3.4 Intentionalism and the Problem of Perception



The intentionalist rejects the argument from illusion as it hinges on
the **Phenomenal Principle** which they reject. For the
intentionalist, an illusory experience in which you see a white wall
as yellow is not a case in which you are directly presented with a
yellow sense-datum, but a case in which a white wall is directly
represented as being yellow.



However, the intentionalist must accept the argument from
hallucination. They accept (A), and they also accept (B) in the form
of the **Common Kind Claim**. (C) follows (given (a1) and
(a2)). Thus, like sense-datum theorists and adverbialists,
intentionalists reject **Direct Realist Presentation**,
and admit that we are not ever directly presented with ordinary
objects, not even in veridical experience.


#### 3.3.5 Intentionalism and Perception of the World



In response to this, the intentionalist can suggest that although they
reject **Direct Realist Presentation**, they do not
reject **Direct Realism**. They can suggest that the
former is not the only way to understand the latter. As we saw above,
another way to understand **Direct Realism** is with a
causal understanding of direct perception.



As we noted above, it is unclear whether the *adverbialist* is
entitled to this, since it is unclear how the adverbialist can make
sense of the object-directedness of experience. But the intentionalist
doesn't face this problem. The object-directedness of experience
is at the heart of their approach. Even though intentionalism denies
that experiences involve the direct presentation of ordinary objects,
it (a) respects and is motivated by the phenomenological observation
that experiences are directly of ordinary objects, and (b) offers an
alternative account of the manner in which experiences are directly of
ordinary objects. As we've seen, instead of presentation, the
intentionalist appeals to representation.



Thus, the intentionalist can maintain that when you see a snow-covered
churchyard for what it is you do *directly perceive* a
snow-covered churchyard. This is *not* because your experience
itself directly presents you with a snow-covered churchyard. It
doesn't. After all, your experience is of such a kind that it
could occur in a hallucination, where it wouldn't directly
present *any* ordinary object. It is rather because your
experience *directly perceptually represents* the presence of a
snow-covered churchyard and is non-deviantly caused by the churchyard
in question. This is what direct perception amounts to for the
intentionalist


#### 3.3.6 Intentionalism and our Ordinary Conception of Perceptual Experience



A concern about adverbialism that we raised above, from the
perspective of one who wants to uphold our ordinary conception of
perceptual experience, is that (a) it rejects our ordinary conception
of perceptual experience almost *wholesale*, and (b)
adverbialist causal direct realism, even if it could be made to work,
doesn't seem to compensate for that: it isn't sensitive
enough to the phenomenological concerns that motivate our ordinary
conception of perceptual experience. In contrast, intentionalism seems
to fare better on both scores. 



First, strictly speaking, the intentionalist must reject our ordinary
conception of perceptual experience. Even though they accept the
**Common Kind Claim**, they reject **Direct Realist
Presentation**. Underlying this is not rejection of
**Ordinary Objects** but of
**Presentation**. But even here, their rejection of
Presentation is not too radical. For intentionalists can say that
experiences are *quasi*-presentational. The appeal to
representation enables this. For when you directly perceptually
represent the snow-covered churchyard, it certainly seems to you as if
a churchyard is directly present to you, even if it is not (as you
are, say, hallucinating). As we noted above, it is not clear from the
resources the adverbialist offers how they can account for how it even
*seems* as if an object is present to you. How does perceiving
whitely make it seem as if a white thing is present to you?



Similarly, though strictly speaking the intentionalist must reject
**Direct Realist Character**, the departure from this is
not too radical. For instead, the intentionalist holds that the
character of experience is determined, at least partly, by the direct
perceptual representation of ordinary objects. It is not as if
ordinary objects and their apparent presence drops out of the picture
on the intentionalist account of phenomenal character. The account is
similar to **Direct Realist Character**, just stripped of
the genuine relationality.



Finally, the causal direct realist story that the intentionalist
offers is intelligible in the way that it arguably isn't for the
adverbialist. And although it invokes causal notions, this is not to
the exclusion of a core *phenomenological* understanding of
direct experience of an object, which the intentionalist accounts for
with the notion of direct perceptual representation. 



Intentionalism, then, is a **Direct Realist** theory
which upholds some of our ordinary conception of perceptual
experience, and insofar as it rejects aspects of our ordinary
conception, it does so in a non-radical way, sensitive to the
phenomenological concerns that motivate this conception in the first
place.


### 3.4 Naive Realist Disjunctivism


#### 3.4.1 Naive Realism in Outline



Consider the veridical experiences involved in cases where you
genuinely perceive objects as they actually are. At Level 1, naive
realists hold that such experiences are, at least in part, direct
presentations of ordinary objects. At Level 2, the naive realist holds
that things appear a certain way to you because you are directly
presented with aspects of the world, and - in the case we are
focusing on - things appear white to you, because you are
directly presented with some white snow. The character of your
experience is explained by an actual instance of whiteness manifesting
itself in experience.



Naive realists thus assign an important explanatory role to the world
itself in explaining the character of veridical experiences. But this
doesn't mean that they are committed to the idea that such
character is *fully* explained or exhausted by the presented
world. Naive realists admit that even holding fixed presented aspects
of the world there can be variation in the character of experience.
This is worked out in different (but compatible) ways by different
theorists. One approach is to note how variations in the
*perceiver* can make for variations in the character of
experience (Logue (2012a)). Another is to highlight a
*third-relatum* (of the relation of presentation) which
encapsulates various conditions of perception such as one's
spatiotemporal perspective and the operative perceptual modality,
where variation in such conditions can make for variation in
phenomenal character (Campbell (2009), Brewer (2011)). Finally, some
suggest that there can be variation in the *way* or
*manner* in which one is related to perceived objects which
makes a difference to phenomenal character (Soteriou (2013), Campbell
(2014), French and Phillips (2020)). For further discussion see French
(2018).



For the naive realist, insofar as experience and experiential
character is constituted by a direct perceptual relation to aspects of
the world, it is not constituted by the representation of such aspects
of the world. This is why many naive realists describe the relation at
the heart of their view as a *non-representational* relation.
This doesn't mean that experiences must lack intentional
content, but it means that (a) insofar as appeal is made to
presentation to explain character, no appeal is made to intentional
content for that purpose, and (b) what is fundamental to experience is
something which itself cannot be explained in terms of representing
the world: a primitive relation of presentation. (For further
discussion of naive realism as a non-representational view, see the
articles in Part Three of Brogaard (2014)).



The other theories we have considered all endorse the **Common
Kind Claim**. We've noted that naive realism applies to
the veridical experiences involved in genuine perception, but does it
apply more widely? Though naive realists may extend their approach to
illusions, they typically deny that it applies to hallucinations and
so reject the **Common Kind Claim**. Naive realists who
deny the **Common Kind Claim** are
*disjunctivists*. We call such a position *naive realist
disjunctivism*. Let's explore these ideas now.


#### 3.4.2 Naive Realism and the Problem of Perception



There are various different naive realist approaches to illusion (see
e.g., Fish (2009: Chapter 6), Brewer (2008, 2011: Chapter 5), Kalderon
(2011), Genone (2014), French and Phillips (2020)). When it comes to
the argument from illusion, the naive realist (like the
intentionalist) rejects the **Phenomenal Principle**. So
how does naive realism differ from intentionalism about illusions? In
two respects: first, naive realists can maintain that illusory
experiences are fundamentally *direct presentations* of the
world. Second, the naive realist can explain the character of such
illusory experiences without appeal to intentional content, but
instead by appealing to the direct presentation of ordinary objects.
Consider, for example, the approach developed by Brewer:



> 
> 
> visually relevant similarities are those that ground and explain the
> ways that the particular physical objects that we are acquainted with
> in perception look. That is to say, visually relevant similarities are
> similarities by the lights of visual processing of various kinds...
> very crudely, visually relevant similarities are identities in such
> things as the way in which light is reflected and transmitted from the
> objects in question, and the way in which the stimuli are handled by
> the visual system, given its evolutionary history and our shared
> training during development (2011: 103)... in a case of visual
> illusion in which a mind-independent physical object, o, looks F,
> although o is not actually F, o is the direct object of visual
> perception from a spatiotemporal point of view and in circumstances of
> perception relative to which o has visually relevant similarities with
> paradigm exemplars of F although it is not actually an instance of F
> (2011: 105).
> 
> 
> 



So though o may not itself be F, it can exist in certain conditions,
C, such that it has visually relevant similarities to paradigm F
things and in that sense it will objectively look F, or look like an F
thing--that is, it will itself have a property, a look or an
appearance, independently of anyone actually seeing it (see also
Martin (2010), Kalderon (2011), Antony (2011), and Genone (2014) on
objective looks). If o is then seen in C, o itself will look F to
*you* in perception. Brewer spells this all out in more detail,
and with various examples. One is seeing a white piece of chalk as
red. The chalk is seen in abnormal illumination conditions such that
the white piece of chalk itself looks like a paradigm red piece of
chalk--it has "visually relevant similarities with a
paradigm piece of chalk, of just that size and shape" (2011:
106). Given that it is seen in those conditions, it looks red to you,
even though it is not in fact red. Here, then, we have an account of
illusions in which we appeal to objects and the ways those objects
are, not the ways they are represented to be, in explaining
character.



What about the argument from hallucination? The naive realist thinks
that at least veridical experiences are direct presentations of
ordinary objects. They thus reject the conclusion (C) of the argument.
But typically, naive realists accept (A). They therefore block the
argument by rejecting the spreading step (B), understood in terms of
the **Common Kind Claim** applied to veridical and
hallucinatory experiences.



Such a naive realist reasons as follows: suppose that when you see a
snow-covered churchyard for what it is, you have an experience which
is in its nature a relation between you and ordinary objects. But a
subjectively indistinguishable hallucinatory experience does not have
such a nature. For such a hallucination could occur in the absence of
any relevant worldly items (e.g., in the lab of a scientist
manipulating your brain, in a world with no white things). Instead of
taking (B) and these facts about hallucination to ground the rejection
of naive realism, the naive realist instead rejects (B): even though
the hallucination as of a snow-covered churchyard is subjectively
indistinguishable from a veridical experience of such a scene, it is
not of the same fundamental kind. (For a more nuanced formulation of
the naive realist reasoning here, see Martin (2004), (2006). Raleigh
(2014) and Ali (2018) advocate a naive realist position which
keeps the **Common Kind Claim** but rejects (A) and hence
the understanding of hallucinations we are operating with here. See
also Masrour (2020) who argues that it is an open question whether
hallucinations are possible.).



In blocking the argument from hallucination in this way the naive
realist endorses *disjunctivism*. This theory was first
proposed by Hinton (1973) and was later developed by P.F. Snowdon
(1979, 1990), John McDowell (1982, 1987) and M.G.F. Martin (2002,
2004, 2006). Disjunctivism is not best construed as it is by one of
its proponents, as the view "that there is nothing literally in
common" in veridical perception and hallucination, "no
identical quality" (Putnam (1999: 152)). For both the veridical
perception of an F and a subjectively indistinguishable hallucination
of an F are experiences which are subjectively indistinguishable from
a veridical perception of an F. What disjunctivists deny is that what
*makes it true* that these two experiences are describable in
this way is the presence of the same fundamental kind of mental state.
Disjunctivists reject what J.M. Hinton calls "the doctrine of
the 'experience' as the common element in a given
perception" and an indistinguishable hallucination (Hinton
(1973: 71)). The most fundamental common description of both states,
then, is a merely disjunctive one: the experience is either a genuine
perception of an F or a mere hallucination as of an F. Hence the
theory's name.


#### 3.4.3 The Development of Naive Realist Disjunctivism



The disjunctivist rejects the **Common Kind Claim**.
Underlying this is a rejection of what Martin (2004, 2006) calls the
"common kind assumption", namely:


* **(CKA)** whatever fundamental kind of mental event
occurs when you veridically perceive, the very same kind of event
could occur were you undergoing a subjectively indistinguishable
hallucination.



But is the disjunctivist's rejection of **(CKA)**
plausible? The disjunctivist can note how the fact that a
hallucination is subjectively indistinguishable from a veridical
experience does not *entail* that they are of the same
fundamental kind, even if it does suggest this. 



However, some argue that even if such an appeal to subjective
indistinguishability is not enough to establish
**(CKA)**, it is nonetheless well supported by a
*causal argument* (Robinson (1985)). We can suppose that when
you see the snow-covered churchyard for what it is, there is some
proximal cause of this experience: the experience is preceded by a
certain sort of brain state B. But now we can imagine a situation in
which we bring about B thus producing an experience in you, yet where
B is not brought about through any interaction between you and a
snow-covered churchyard--e.g., in laboratory conditions. In this
scenario you have an hallucinatory experience as of a snow-covered
churchyard. It is plausible to suppose that these experiences are of
the very same kind given that they have the same proximal cause.



The point here is that **(CKA)** looks like a plausible
principle for *causally matching* veridical and hallucinatory
experiences - veridical and hallucinatory experiences with the
same proximal cause. This way of motivating **(CKA)**
appeals to a same-cause, same-effect principle:


* Causal Principle 1: an event e1 is of the same kind as an event e2
if event e1 is produced by the same kind of proximate causal condition
as e2 (Nudds 2009: 336).



Is this the end of the road for the naive realist disjunctivist, then?
Not quite, since as Martin argues, the naive realist should reject
this principle:



> 
> 
> On [the naive realist] conception of experience, when one is
> veridically perceiving the objects of perception are constituents of
> the experiential episode. The given event could not have occurred
> without these entities existing and being constituents of it; in turn,
> one could not have had such a kind of event without there being
> relevant candidate objects of perception to be apprehended. So, even
> if those objects are implicated in the causes of the experience, they
> also figure non-causally as essential constituents of it... Mere
> presence of a candidate object will not be sufficient for the
> perceiving of it, that is true, but its absence is sufficient for the
> non-occurrence of such an event. The connection here is [one] of a
> constitutive or essential condition of a kind of event. (2004:
> 56-57).
> 
> 
> 



Martin's point is that the naive realist may well admit the
possibility of veridical experiences and causally matching
hallucinations, but they will resist the idea that sameness of
proximal cause implies sameness of the kind of experience involved.
This is because there are *non-causal constitutive condition*s
for the occurrence of the veridical experience which are not satisfied
in the hallucinatory case.



However, Martin suggests that the arguer from hallucination can
develop their case against naive realism further. This development
involves an argument with two stages. First, a modified causal
argument: the *reverse causal argument*, and second the
*screening-off problem.* 



The modified causal argument involves a modified causal principle:


* Causal Principle 2: an event e1 is of the same kind K as an event
e2 if event e1 is produced by the same kind of proximate causal
condition as e2 in circumstances that do not differ in any non-causal
conditions necessary for the occurrence of an event of kind K (Nudds
2009: 337).



(Martin's own modified causal principle is more complicated than
this in allowing for indeterministic causation. We gloss over this
important complication here). Take N to be the fundamental kind which
characterizes a veridical experience of a snow-covered churchyard,
according to the naive realist. Does Causal Principle 2 allow us to
say that N is present in the causally matching hallucinatory case, as
**(CKA)** predicts? No. For the hallucination is produced
in circumstances that differ in non-causal conditions necessary for
the occurrence of N *given how the naive realist understands
N*: in the circumstances in which the hallucination occurs there
is no appropriate object of perception, but the presence of such an
object is necessary for the occurrence of N.



So how does Causal Principle 2 help the arguer from hallucination? We
have to run an argument in "the reverse direction, from what
must be true of cases of causally matching hallucinations, to what
must thereby be true of the veridical perceptions they match"
(Martin 2006: 368). That is, take a hallucination as of a snow-covered
churchyard h, and suppose that h is of some fundamental kind H. Now we
can apply Causal Principle 2 to show that H is present in a causally
matching *veridical* experience of a snow-covered churchyard,
v. For now v is produced by the same kind of proximal cause in
circumstances where there is no difference in the non-causal
conditions necessary for the occurrence of an event of kind H. This is
because all that is necessary for an occurrence of H is some brain
condition, which is present in the circumstances in which v is brought
about. This reverse causal argument does not show that v is not of
fundamental kind N. What it does show, however, is that whatever
fundamental kind is present in a hallucinatory case will also be
present in a causally matching veridical case. So even if v is
fundamentally N it is also H. That is, we have the Reverse Common Kind
Assumption:


* **(RCKA)** Whatever fundamental kind of event occurs
when you hallucinate, the very same kind of event also occurs in a
causally matching veridical experience.



But now we run into the *screening-off problem*. There is
something it is like for you to have an hallucinatory experience as of
a snow-covered churchyard, and the experience seems to relate you to a
snow-covered churchyard. This fact about the hallucinatory experience
is grounded in its being of kind H. But now if an experience of that
kind is present in the veridical case, it is difficult to see how what
the naive realist says is fundamental to that case, N, is doing
anything by way of explaining what it is like for a subject to have
the experience. The presence of H in the veridical case seems to make
N explanatorily redundant, or "screen off" N's
explanatory role, contra the ambitions of naive realism. (For more
detailed expositions of this two-stage argument see Martin (2004),
Byrne and Logue, (2008), Hellie (2013) and Soteriou (2014: Chapter
6)).



The most widely discussed naive realist response to this argument is
that of Martin (2004, 2006). Though there are now a range of different
naive realist responses available, some of which integrate critical
discussion of Martin's own approach (see Allen (2015), Logue
(2012b, 2013), Fish (2009: Chapter 4), Hellie (2013), Moran (2019),
Sethi (2020)).



Martin argues that the screening-off stage of the argument is only
problematic if we accept a positive, non-derivative account of
causally matching hallucinations. On such an account, hallucinations
have a positive nature which doesn't derive from that of
veridical perception: a nature that can be specified independently of
any reference to veridical perception. For instance, hallucinations
are direct presentations of sense-data, or representations of ordinary
objects. Instead, Martin suggests, the disjunctivist should conceive
of causally matching hallucinations in a purely negative epistemic
way: such a hallucination as of an F is a state of mind which is not
introspectively knowably not a veridical perception of an F. What
makes it the case that your hallucinatory experience is as of a
snow-covered churchyard, with a certain sort of phenomenal character,
is just that it is an occurrence which cannot be discriminated, by
introspection alone, from a veridical perception of a snow-covered
churchyard. The particular subjective perspective that a hallucinator
has in a causally matching hallucination as of a snow-covered
churchyard is explained just by the obtaining of this negative
epistemic condition, not by anything more positive such as a relation
to a white sense-datum or the representation of white snow (c.f.,
Dancy (1995: 425)). On such a view, causally matching hallucinations
are derivative: specifying their nature requires essential reference
to the basic case of veridical perception.



If we accept Martin's account of causally matching
hallucinations, then we can see how H can be present in both the
hallucinatory and the veridical case: since trivially a veridical
experience of a snow-covered churchyard is indiscriminable from a
veridical experience of a snow-covered churchyard. But what about
screening off? Does H have a nature which means that the presence of H
in the veridical case threatens the explanatory power of N? It
doesn't, Martin argues, since H's explanatory force is
derivative or dependent: it is parasitic on that of N. As Martin notes
with his own example:



> 
> 
> But if that is so [if H screens off the explanatory role of N], then
> the property of being a veridical perception of a tree [i.e. N] never
> has an explanatory role, since it is never instantiated without the
> property of being indiscriminable from such a perception being
> instantiated as well. But if the property of being a veridical
> perception lacks any explanatory role, then we can no longer show that
> being indiscriminable from a veridical perception has the explanatory
> properties which would screen off the property of being a veridical
> perception (2004: 69).
> 
> 
> 



Here, then, is a summary of this complex dialectic: the *argument
from hallucination* seems to disprove naive realism, but the naive
realist appeals to *disjunctivism* in response. However, the
*causal argument* puts pressure on disjunctivism, by supporting
the *common kind assumption*. In response, the naive realist
rejects the key principle of this argument (Causal Principle 1). But
then a two-stage argument consisting of the *reverse causal
argument* and the *screening-off problem* attempts to show
that: (1) the fundamental kind of experience present in hallucination
is also present in causally matching veridical experience, and (2)
this undermines the naive realist idea that the character of veridical
experience is shaped by the directly presented world. In response,
Martin accepts a form of naive realism which embraces disjunctivism
(in the form of the claim that causally matching veridical and
hallucinatory experiences are fundamentally different). But which also
accepts (as per the reverse causal argument) that there is a common
element across the cases, for the hallucinatory kind is present in
veridical cases too. But since he conceives of this common element in
a derivative, and purely negative epistemic way, he blocks the
argument at the second stage, rejecting screening off.



Naturally, then, much subsequent critical discussion has focused on
Martin's negative epistemic conception of hallucination. Further
discussion and development of Martin's approach is to be found
in Nudds (2009, 2013) and Soteriou (2014: Chapter 6). For criticism of
Martin's approach see Hawthorne and Kovakovich (2006), Farkas
(2006), Sturgeon (2008), Siegel (2004, 2008), and Robinson (2013). See
Burge (2005) for a general and polemical attack on disjunctivism. For
more on disjunctivism, see Haddock and Macpherson (eds.) (2008), Byrne
and Logue (eds.) (2009), Macpherson and Platchias (eds.) (2013) and
the entry on
 the disjunctive theory of perception.


#### 3.4.4 Naive Realist Disjunctivism and Our Ordinary Conception of Perceptual Experience



According to naive realist disjunctivists, at least veridical
experiences are directly of ordinary objects (**Ordinary
Objects**), and are direct presentations of their objects
(**Presentation**). Naive realist disjunctivists thus
maintain **Direct Realist Presentation**, and hence
**Direct Realism** for at least veridical experiences
- indeed they maintain **Direct Realism** without
the need for any appeal to a causal theory of direct perception.
Further, naive realist disjunctivists hold that the phenomenal
character of such experiences is determined, at least in part, by the
direct presentation of ordinary objects (**Direct Realist
Character**). The only aspect of our ordinary conception of
perceptual experience which naive realist disjunctivists reject
outright is the **Common Kind Claim**.


## 4. Conclusion



Sense-datum theorists and adverbialists depart substantially from our
ordinary conception of perceptual experience. Advocates of each view
will argue, in their different ways, that this is a consequence of
responding adequately to the Problem of Perception. 



Intentionalists and naive realist disjunctivists disagree, and argue,
in different ways, that we can respond to the Problem of Perception
without departing substantially from our ordinary conception of
perceptual experience: by maintaining **Direct Realism**
in some form, and maintaining or at least being sensitive to many of
the specific phenomenological components of our ordinary conception of
perceptual experience.
  

  

Whilst the debate between sense-datum theorists and adverbialists (and
between these and other theories) is not as prominent as it once was,
the debate between intentionalists and naive realist disjunctivists is
a significant ongoing debate in the philosophy of perception: a legacy
of the Problem of Perception that is arguably "the greatest
chasm" in the philosophy of perception (Crane (2006)). The
question, now, is not so much *whether* to be a direct realist,
but *how* to be one.