## 1. Introduction




Disjunctivists and their opponents agree that veridical perceptions,
illusions and hallucinations have something in common, in so far as
they agree that such mental events should be grouped together as being
perceptual experiences. They also agree that there are differences to
be marked between them, hence the different labels for them. However,
they disagree when it comes to specifying what these commonalities and
differences consist in. What distinguishes the disjunctivist theory is
its rejection of a 'common kind claim'--the claim
that the conscious perceptual experiences that are involved in cases
of veridical perception, illusion and hallucination have the same
nature. If one accepts that the same kind of conscious experience
occurs in all three cases, then this imposes a constraint on the
account one can give of the kind of conscious event that occurs when one
veridically perceives the world. Disjunctivists deny that our
accounts of veridical perception should be constrained in this way. So
the disjunctivist view of perceptual experience can be regarded as a
negative thesis--the rejection of a common kind claim--that
is adopted in defence of a positive view of veridical perception.




Those who hold a disjunctive theory of perception do not deny that
it is possible to have a hallucination of an *F* that is subjectively
indistinguishible from a veridical perception of an *F*. That is, they do
not deny that it is possible for one to have a hallucination such that
one cannot tell through introspection alone that it is not a veridical
perception of an *F*. So associated with the disjunctivist's
metaphysical stance, namely the rejection of the common kind claim, is
an epistemological proposal that emphasises limitations on a
subject's capacity to tell what kind of experience she is
undergoing on the basis of introspection alone. For example, J.M.
Hinton, an early proponent of the disjunctive theory,
acknowledges that both a hallucination of an *F* and a veridical
perception of an *F* can appear, from the inside, to be a veridical
perception of an *F*. However, he holds that it is a mistake to assume
that this appearance is to be explained by the thesis that these
experiences share a common nature that is manifest to one when has the
experiences.




Hinton is generally credited with being the first to demarcate clearly
the disjunctivist stance, and the fact that the disjunctive theory of
perception is so named is due to his way of framing the view. Hinton
(1967 and 1973) argued that we should understand a statement about how
things sensorily appear to a subject to be equivalent to a disjunctive
statement that *either* one is veridically perceiving such and
such *or* one is suffering an illusion (or hallucination); and
such statements are not to be regarded as making a report about a
distinctive mental event or state that is common to these disjoint
situations. (For discussion of the historical significance of Hinton,
see Snowdon 2008). The disjunctive approach to perceptual experience
was later developed by Paul Snowdon (1980-81), John McDowell
(1982), and M.G.F. Martin (2002), among others.


## 2. Varieties of Disjunctivism




There are some significant differences between some of the views that
fall under the disjunctivist label. Disjunctivists are united in their
rejection of a common kind claim, and they generally adopt this stance
because they hold views about the nature of veridical perception that
they take to be inconsistent with it. However, not all disjunctivists
are in agreement over the account that should be given of veridical
perception, and not all disjunctivists are in agreement over the
question of the accounts that should be given of hallucinations and
illusions. The different disjunctivist proposals about illusion and
hallucination are discussed in section 5. This section focuses on some
of the main differences between the accounts that disjunctivists offer
of the relevant features that they claim veridical perceptions have,
and which they claim hallucinations lack.




The fact that there are some significant differences between some of
the views that fall under the disjunctivist label can introduce
complications when it comes to trying to formulate more precisely a
distinctively *disjunctivist* commitment that is common to all
of them. So first (in section 2.1) some further remarks are in order
concerning some of the different ways in which disjunctivism in
general has been formulated in the literature. When it comes to
assessing arguments that are presented as being either for or against
disjunctivism it is obviously going to be important to be sensitive to
the question of which formulation of disjunctivism is in play. Given
that many who adopt a disjunctivist position do so in defence of a
particular account of veridical perception, it will also be important
to assess which disjunctivist commitment, if any, is actually entailed
by their view of the nature of veridical perception.


### 2.1 Ways of Formulating Disjunctivism


#### 2.1.1 Fundamental Kind Disjunctivism




Disjunctivists maintain that veridical perceptions and hallucinations
are mental events (or states) of different kinds. However, we need
further clarification of what this claim amounts to, for there is an
understanding of this claim that it may be open to a non-disjunctivist
to accept as well. For example, the non-disjunctivist can accept that
the terms 'veridical perception' and
'hallucination' mark useful distinctions between
perceptual experiences that may, in certain contexts, be of
explanatory significance. So the non-disjunctivist may agree that
there is a sense in which veridical perceptions and hallucinations can
be thought of as perceptual experiences of different kinds. For
similar reasons the disjunctivist can agree that there is a sense in
which veridical perceptions and hallucinations can be thought of as
experiences of the same kind. For disjunctivists do not in general
deny that veridical perceptions and hallucinations can
have *anything* in common.




One formulation of disjunctivism invokes the notion of a
*fundamental* kind. (This formulation is principally due to
Martin, but see also Snowdon 2005a, p. 136. For discussion of this
formulation, see Logue 2013). According to this formulation, the
disjunctivist is committed to denying that veridical perceptions,
illusions and hallucinations are conscious events of the same
*fundamental* kind. The assumption here is that for mental
events, there is a most specific answer to the question, 'What is
it?' that tells us what *essentially* the mental event is,
and thereby specifies its *fundamental* kind. On this
formulation, the disjunctivist is committed to denying that whatever
fundamental kind of conscious event occurs when one is veridically
perceiving the world, that kind of event can occur whether or not one
is veridically perceiving. Let us call a view of this sort
*fundamental kind disjunctivism*.




While those who advocate this form of disjunctivism reject a common
kind claim, namely the claim that veridical perceptions and
hallucinations are mental events of the same *fundamental* kind,
they may allow that veridical perceptions and hallucinations have
something in common. So they may allow that there is a kind *K* that
veridical perceptions and hallucinations can both instantiate. However, what
they deny is that such a kind *K* is the *fundamental* kind of
conscious event occurring when a subject veridically perceives the
world.




Not all accept the metaphysical assumption that mental events (or
states) have a 'fundamental' kind. A disjunctive theory of
perception is often adopted in defence of a particular account of
veridical perception, such as naive realism, and Byrne and Logue
(2008) question whether any controversial claim about fundamental kinds
is needed in order to defend a naive realist view of veridical
perception. They suggest that one may hold a naive realist view
according to which mind-independent objects, such as tables and trees,
are constituents of the experience one has when one veridically
perceives the world, without being committed to a further claim about
what the *essence* of such episodes consists in. They also note
that naive realism is often motivated by phenomenological
considerations, and they question whether introspective reflection on
the phenomenology of the experience one has when one veridically
perceives the world puts one in a position to learn anything about the
*essence* of the experience one is having.


#### 2.1.2 The 'Distinct Mental Feature' Formulation




Those who reject the metaphysical assumption that mental events (or
states) have a 'fundamental' kind may instead formulate
their disjunctivist stance in terms of the claim that the differences
between the kind of mental event that occurs when one veridically
perceives the world and the kind of mental event that occurs when one
hallucinates are due to differences in *mental features* of
the events in question. The thought here is that the fact that there
is a respect in which two mental events (or states) are different may
not be due to the fact that they differ in some mental respect, and
while we might type mental events and states in a variety of different
ways, for a variety of different purposes, we can distinguish a way of
classifying such events and states that focuses solely on their mental
features. For example, although there may be a context in which it
suits our purposes to group together the beliefs of a subject that are
true, it is not generally thought that a belief's being true is a
mental feature of that state.




According to this alternative way of formulating disjunctivism, the
disjunctivist holds that veridical perceptions and hallucinations
differ mentally in some significant respect--i.e., there are
certain mental features that veridical perceptions have that
hallucinations cannot have. So the disjunctivist rejects the claim
that the differences between a case of veridical perception and a case
of hallucination can simply be due to differences in the extra-mental
states of affairs that obtain in those situations. Note, however, that
this formulation of the disjunctivist commitment leaves open the
possibility that veridical perceptions and hallucinations can have at
least *some* mental features in common. (See Logue 2012a, 2013,
and 2014.) There is a sense, then, in which it thereby leaves open the
possibility that there can be a common mental element to veridical
perception and hallucination.


#### 2.1.3 The 'No-Common-Mental-Element' Formulation




Byrne and Logue (2008) propose that the label '*metaphysical
disjunctivism*' be reserved for an account of perceptual
experience that commits to the claim there is
*no* common mental element to veridical perception and
hallucination. According to Byrne and Logue, those who deny that veridical
perceptions and hallucinations are mental events of the same
*fundamental* kind (see section 2.1) are not *thereby*
committed to '*metaphysical disjunctivism*', as
Byrne and Logue use this label. For as they point out, those who reject
the claim that veridical perceptions and hallucinations are mental
events of the same fundamental kind need not deny that there is a
common mental element to veridical perception and hallucination. So it
is worth bearing in mind the particular use to which Byrne and Logue
put the label 'metaphysical disjunctivism', as others would
naturally characterise fundamental kind disjunctivism as a metaphysical
disjunctivist thesis.




As we've seen, the issue of how precisely to formulate a
distinctively *disjunctivist* commitment is not
uncontroversial. For now we can at least say that the minimal
commitment of a view that can be labelled a disjunctivist theory of
perception is that veridical perceptions and hallucinations differ
mentally in some significant respect--i.e., there are certain
mental features that veridical perceptions have that hallucinations
cannot have. So we can mark some of the differences between views that
fall under the disjunctivist label by invoking the notion of
'disjunctivism about *X*', where *X* is the
relevant mental feature that it is claimed differs in cases of
veridical perception and hallucination. This procedure is adopted in
the following two sections. If the disjunctivist about *X*
makes the additional claim that the particular mental
feature, *X*, that is unique to the case of veridical
perception is essential to the fundamental kind of mental event it is,
then they will also be a fundamental kind disjunctivist. Furthermore,
if they deny that there is a common mental element to veridical
perception and hallucination they will satisfy the
'no-common-mental-element' formulation of disjunctivism.


### 2.2 Disjunctivism about Intentional Content




According to an intentionalist account of perceptual experience, our
perceptual experiences are mental events (or states) with intentional
contents that represent the world as being a certain way. The
disjunctivist who accepts this general approach to perceptual
experience may hold that a veridical perception has an intentional
content that a hallucination cannot have. For example this sort of
disjunctivist may hold that the intentional content of a veridical
perception is constitutively dependent on mind-independent objects,
while the intentional content of a hallucination is not.




One route to this view proceeds through the claims that a veridical
perception of the world is a perceptual state with an intentional
content containing demonstrative elements that refer to the
mind-independent items in the environment that are perceived, and that
truth-evaluable intentional contents with demonstrative elements that
successfully refer are object-dependent. On this view, a particular
experience *E* that is a veridical perception of a particular
mind-independent object *O* will have an intentional content
with a demonstrative element that successfully refers to *O*,
and a distinct particular experience *E*\* will have
an intentional content with the same veridicality conditions only if
its intentional content contains a demonstrative element that also
refers to *O*. If *E*\* is a hallucination it
will not have an intentional content with a demonstrative element that
successfully refers to *O*, so it will not have an intentional
content with the same veridicality conditions as *E*. Suppose
we now add the following assumption: If two experiences have
intentional contents which differ in their veridicality conditions,
then this is not just a respect in which these mental events differ,
it is also amounts to a difference in their mental kinds. We can now
derive the conclusion that veridical perceptions and hallucinations
are experiences of different mental kinds. This last assumption needs
to be made explicit, as it is not agreed upon by all (e.g., Burge
1993, 2005 and 2010). Note that acceptance of the assumption would
also commit one to the following claim: If *E*\* is a
veridical perception of numerically distinct object
*O*\*, then *E* and *E*\* are
to be regarded as experiences of different mental kinds even if
*O* and *O*\* are perceptually indiscernible
to the subject who perceives them. (For discussion of the status of
that assumption, see Mehta 2014, Gomes and French 2016, Mehta and
Garson 2016, and French and Gomes 2019).




Someone who holds this sort of view may claim that it is possible for
a veridical perception and a hallucination to have the same phenomenal
character. For they may claim that it is possible for experiences to
have the same phenomenal character despite the fact that they do not
have the same intentional content. According to the terminology that
Byrne and Logue adopt (see section 2.1.2) this would make the view
a *moderate* one. Someone adopting the moderate approach might
claim that hallucinations have an existentially quantified intentional
content and veridical perceptions also have a layer of content that is
existential. They might then hold that this layer of existential
content, which is present in experience whether or not one is
veridically perceiving the world, provides a common mental factor for
veridical and hallucinatory experiences.




Tye (2007) favours a different 'moderate' approach. He
holds that veridical perceptions have object-dependent singular
intentional contents that hallucinations cannot have, and he holds
that veridical perceptions and hallucinations can have the same
phenomenal character. However, he rejects the claim that there is a
layer of existential content that provides a common mental factor for
veridical and hallucinatory experiences. According to Tye, veridical
perceptions and hallucinations have intentional contents that
represent clusters of properties. In the case of veridical perception
the cluster of properties is represented within a content that is
singular and object-dependent, whereas in the case of hallucination
the cluster of properties is represented within a content that is
'gappy'. (See also Schellenberg 2010, 2013, and 2016.)
Tye's suggestion is that veridical perceptions and
hallucinations have contents with a common structure, and this
structure may be conceived as having a slot in it for an object. In
the case of veridical perception the slot is filled by the object
perceived, and in the case of hallucination the slot is empty, and
hence the content is 'gappy'. Tye claims that the
phenomenal character of a given visual experience is the cluster of
properties represented by that experience. And he claims that this is
why veridical perceptions and hallucinations can have the same
phenomenal character.


### 2.3 Disjunctivism about Phenomenal Character




Some disjunctivists claim that veridical perceptions have a phenomenal
character that hallucinations cannot possess. For example, according
to one version of naive realism (what we might call
'naive realism about phenomenal character'), when one
veridically perceives the world, the mind-independent items perceived,
such as tables and trees and the properties they manifest to one when
perceived, partly constitute one's conscious experience, and
hence determine its phenomenal character. This sort of naive
realist view is primarily motivated by phenomenological considerations.
The suggestion is that this view best articulates how sensory
experience seems to us to be through introspective reflection.
According to those who propose this form of naive realism one
cannot provide an adequate account of the phenomenal character of
veridical perception by simply appealing to the idea that such
experience has an intentional content that represents the world as
being a certain way, even if one holds that the intentional content in
question is object-dependent; nor can one provide an adequate account
of the phenomenal character of veridical perception by simply adding to
this the claim that experience possesses further non-representational
properties that it could possess independently of whether any
mind-independent objects are being perceived. The naive realist
about phenomenal character instead claims that the right account of the
phenomenal character of veridical perception should appeal to the idea
that such experience relates to the mind-independent items perceived in
a non-representational manner. (The motivations for this view are
discussed in section 3.3).




Since this naive realist account of phenomenal character cannot
be applied to hallucination, those who propose it are committed to the
claim that the kind of phenomenally conscious experience that occurs when
one veridically perceives the world does not occur when one is
hallucinating. These naive realists can accept that veridical
perceptions of numerically distinct objects can have the same
phenomenal character, but they deny that veridical perceptions and
hallucinations have the same phenomenal character. They must then say
that hallucinations that are subjectively indistinguishible from
veridical perceptions do not have the kind of phenomenal character that
introspective reflection suggests. Some disjunctivists allow that some
hallucinations that are subjectively indistinguishible from veridical
perceptions have no phenomenal character (e.g., Fish 2008 and 2009; and
see also Sturgeon 2006 and 2008), but this is not a commitment of all
disjunctivists about phenomenal character. (For further discussion, see
section 5.1)


### 2.4 Epistemological Disjunctivism




Some disjunctivist views are primarily motivated by epistemological
considerations, rather than phenomenological ones. According to one
approach what is fundamental to the nature of a veridical perception is
the fact that it belongs to an epistemically distinguished class of
perceptual experiences. Those advocating this form of disjunctivism
place emphasis on the idea that when one veridically perceives the
world one has a distinctive form of epistemic contact with the
mind-independent world, and one's experience provides one with
grounds for making knowledgeable perceptual judgements about the
mind-independent world that would be lacking if one were merely
hallucinating. On this view it is a mistake to assume that the
epistemic grounds that a veridical perception can provide one with for
making judgements about the world are no better than the epistemic
grounds that are available to one when one has a subjectively
indistinguishible hallucination. Moreover, according to this view, the
epistemic difference between a veridical perception and a subjectively
indistinguishible hallucination is not to be explained by simply citing
factors that are external to the subjective experiential state one is
in when one veridically perceives the world. Rather, the epistemic
difference is due to the fact that the kind of subjective experiential
state one is in when one veridically perceives the world is not the
same as the kind of subjective experiential state one is in when one
has a subjectively indistinguishible hallucination.




Byrne and Logue (2008) and Snowdon (2005a) argue that that this sort
of epistemologically motivated view need not preclude the idea that it
is possible to identify a perceptual state that is common to veridical
perception and hallucination. The suggestion is that one can accept the
claim that there is an epistemically distinguished category of
experiential state that can only obtain when one veridically perceives
the world, and yet one can consistently maintain that it is also
possible to identify a kind of perceptual state, of which some positive
account can be given, which can obtain whether one is veridically
perceiving the world, or merely having a subjectively indistinguishible
hallucination. One can therefore be an epistemological disjunctivist
without accepting metaphysical disjunctivism. However, note that if one
holds that the epistemological feature that is present in the case of
veridical perception and lacking in the case of hallucination is
fundamental to the kind of mental state it is, then this would make one
a *fundamental kind disjunctivist* (see section 2.1.1).




John McDowell is an epistemological disjunctivist and some have
suggested that the view he espouses does not commit him to
metaphysical disjunctivism. (For discussion of this claim see Snowdon
2005a, Byrne and Logue 2008, and Haddock and McPherson 2008b). Millar
(2007 and 2008) explicitly endorses the claim that we should accept a
form of epistemological disjunctivism about perceptual knowledge
without being committed to metaphysical disjunctivism. (For more
general discussion of epistemological disjunctivism, see Pritchard
2012, and see also the papers collected in Doyle, Milburn and
Pritchard 2019).


## 3. Arguments for Disjunctivism


### 3.1 An Argument for Disjunctivism as the Default View




When J.M. Hinton first introduced discussion of the disjunctive view
of experience his primary concern was to identify and undermine what
he took to be a substantive assumption in much philosophical
theorising about perception. His target was the assumption that
veridical perception and subjectively indistinguishible hallucination
have the same intrinsic nature. In particular, his target was the
assumption that the fact that a hallucination can be subjectively
indistinguishible from a veridical perception is to be explained by
the thesis that these experiences share a common nature that is
manifest to one when has the experiences. Hinton does not try to prove
directly that this 'common element' assumption is
false. Instead, he tries to argue that it is unwarranted, and that his
alternative, disjunctivist approach to perceptual experience should be
our default view. M.G.F. Martin has also argued that the disjunctive
account of experience should be our default view. Martin's
argument to this effect is discussed in section 3.3. This section
focuses on Hinton's version of the argument.




Hinton (1967 and 1973) develops his disjunctivist view by focusing on
the kinds of reports we make about an experience we are undergoing
when we are remaining neutral on the question of whether that
experience is a veridical perception, an illusion, or a
hallucination. For example, when making a report about one's
experience in this neutral way one might say 'I seem to see
an *F*', which can be true whether or not one is actually
seeing an *F*, or one might make a claim about what appears to
one to be the case. Hinton thinks that those who accept the common
element assumption will hold that these 'Neutral Experience
Reports' are used to pick out the intrinsic properties of
one's experience, which are manifest to one simply in virtue of
having the experience, and which the experience could possess whether
or not one actually perceives anything. Hinton's alternative
proposal is that these Neutral Experience Reports are equivalent to
disjunctive statements of the form 'I see an *F*, or
I'm having that illusion'. Hinton labels such disjunctive
statements 'Perception-Illusion disjunctions'. Hinton
argues that in order to substantiate their common element assumption,
his opponents need to show that our Neutral Experience Reports are not
equivalent to these Perception-Illusion disjunctions, and he tries to
argue that this is a challenge that his opponents cannot meet.




The fact that Hinton chooses to focus on the *reports* we
make about our experiences, may be a reflection of the fact that his
primary concern is to question an assumption about those properties of
experience that we should be in a position to make reports about simply
in virtue of having the experience. ("You want a predicate whose
applicability to what is happening in or to me is made clear to me by
the very fact of that thing's happening", Hinton 1967,
224.) We might then understand Hinton as taking his opponent to be
committed to the claims that (a) perceptions and subjectively
indistinguishible hallucinations have such properties in common, (b) it
is the fact that perceptions and hallucinations have such properties in
common that explains their being subjectively indistinguishible, and
(c) these are the properties we are picking out when we make Neutral
Experience Reports. He may then be seen as trying to undermine the
assumption that (a) and (b) are correct by throwing into doubt our
entitlement to (c).




For Hinton, an important feature of his Perception-Illusion
Disjunctions is that they do not report what is happening to the
subject, as distinct from saying, non-committally, that one of a number
of things is happening. Hinton claims that these disjunctive claims do
not give a "definite answer" to the question 'what
happened to the subject?' or as he sometimes puts it, they do not
give the "what-it-is of the event" in question. This is why
Hinton thinks that substantiating the relevant common element
assumption requires showing that our Neutral Experience Reports are not
equivalent to his disjunctive statements. According to the thought
expressed in (c) above, our Neutral Experience Reports are committal in
a way that these disjunctive statements are not. So the idea here seems
to be that if our Neutral Experience Reports are equivalent to
Hinton's Perception-Illusion disjunctions, then assumption (c),
above, is thereby undermined.




One way of defending a common element view against this line of
argument might be to defend the claim that one can accept (a) and (b)
without being committed to (c). Alternatively one might object that an
adequate defence of (a) and (b) need not simply depend on establishing
(c) (see Snowdon 2008).




Furthermore, one might question what Hinton has in mind in his use
of the term 'equivalent' when he says that his opponent
needs to show that our Neutral Experience Reports are not equivalent to
his Perception-Illusion disjunctions. For Hinton denies that he is
suggesting that his Perception-Illusion disjunctions provide us with a
*conceptual* analysis of our Neutral Experience
Reports. Snowdon (2008) suggests that the most obvious reading of
'equivalent' in this context is the following:
'*P*' is equivalent to '*Q*' if
and only if it is a priori that necessarily (*P* if and only
if *Q*). Snowdon then poses the following problem for
Hinton's argument. The fact that a statement is disjunctive does
not on its own mean that it cannot be equivalent, in the relevant
sense, to a non-disjunctive statement, which, as a consequence of
being non-disjunctive, may well count as saying what sort of thing is
happening. Snowdon offers a mathematical example in support of this
claim. '*X* wrote down a number which is either 2 or an
uneven prime number' is equivalent, in the relevant sense, to
'*X* wrote down a prime number'.




The problem this poses for Hinton is that it suggests that he may be
wrong to assume that his opponent needs to show that our Neutral
Experience Reports are not equivalent to his Perception-Illusion
disjunctions. For even if they were equivalent to the
Perception-Illusion disjunctions, this might not in itself show that
such reports don't pick out a common element to perception and
illusion / hallucination and give a definite answer to the question
'what is happening?'




Snowdon suggests that despite this, what Hinton does achieve, in his
various discussions of these issues, is to put pressure on the
assumption that there is anything in the use we make of our ordinary
Neutral Experience Reports that thereby commits us to the common
element view--i.e., the view that Hinton is attempting to target.
Suppose we accept that Hinton does achieve what Snowdon suggests.
Consistent with this, one might also hold that there is nothing in the
use we make of our ordinary Neutral Experience Reports that thereby
commits us to a denial of the common element view. One might think that
a denial of the common element view is at least as committal as its
affirmation, for it involves a substantive metaphysical claim about the
nature of perceptual experience. So why should we think that the burden
of proof lies with the common element theorists to establish
*their* view?




At points it looks as though Hinton thinks that an extra commitment
incurred by the common element theorist is an epistemic one. For
example, Hinton considers the following objection that might be raised
against his disjunctive approach: "If *A*-ing [i.e.,
seeing an *O*] and *B*-ing [i.e., having that illusion]
did not have a worn-on-the-sleeve property in common, how could you
take one for the other?" To which Hinton's reply is,
"Why should it just not seem that they had properties in common?
Seeing a flash of light and having the illusion seem, but only seem,
to have in common the property 'when *x* occurs a flash
of light occurs'" (1967, 225). The implication here seems
to be that Hinton is taking his opponent to be making a substantive
epistemic assumption--that our inability to discern through
introspection any differences between a hallucination and a perception
must ultimately be explained by our positive ability to discern
through introspection that they are events of the same kind. (For a
critique of this assumption, see also Putman 1999).


### 3.2 An Epistemological Argument




McDowell's disjunctive conception of perceptual experience is
primarily motivated by epistemological concerns. He appeals to a
disjunctive conception of perceptual experience in offering a proposal
as to how we should resist a "tempting" line of argument
that has an epistemological conclusion. The conclusion of the tempting
argument is that when one genuinely perceives the world, the epistemic
grounds one has for one's world-directed judgements can be no
better than those available to one when one hallucinates. (See McDowell
1982, 1987, 1994, 2008, 2010, and 2013. See Putnam 1999 for an endorsement of
McDowell's approach.)




The tempting line of argument that McDowell is concerned to resist
starts by proposing that since hallucinations can be subjectively
indistinguishible from genuine perceptions, the differences between
your genuine perceptions and your hallucinations must be external to
how things are with you subjectively. An epistemic claim is then made:
Matters external to how things are with you subjectively cannot
intelligibly contribute, even in part, to your epistemic standing on
some question. For such matters will be beyond your ken, and matters
beyond your ken cannot make any difference to your epistemic standing.
The conclusion that is then drawn is that when you genuinely perceive
the world your epistemic grounds for making world-directed perceptual
judgements are the same as, an hence no better than, those available to
you when you have a subjectively indistinguishible hallucination.




In responding to this line of argument, McDowell appeals to a
disjunctive conception of perceptual experience in order to block the
move from the claim that (i) hallucinations can be subjectively
indistinguishible from genuine perceptions, to the claim that (ii) the
differences between a genuine perception and a hallucination must be
"blankly external to one's subjectivity" (McDowell
1982). This is then supposed to provide us with a way of resisting the
argument's conclusion--i.e., the claim that the experiences
involved in genuine perception and hallucination do not differ in their
epistemic significance. According to the disjunctive conception of
experience that McDowell proposes, we can accept that what is common to
a genuine perception and a subjectively indistinguishible hallucination
is the fact that the subject's experience is such that it appears
to her that some environmental fact obtains. However, we should also
accept that an appearance that such-and-such is the case can be
*either* a mere appearance *or* the fact that
such-and-such is the case making itself perceptually manifest to
someone, and on McDowell's view, when a fact is made perceptually
manifest to one, the obtaining of the fact is not "blankly
external to one's subjectivity". So the obtaining of the
fact can contribute to one's epistemic standing.




A standard line of objection against McDowell's disjunctivist
proposal is that the epistemological considerations he invokes do not
adequately support the disjunctive account of experience that he
recommends. The general claim behind this line of objection is that an
adequate account of the epistemological role of perceptual experience
need not involve any appeal to disjunctivism. As there are many
different accounts of the epistemological role of perceptual
experience, there are many different forms that this line of objection
can take.




For instance, according to one widely held view, the perceptual
judgements one makes when one is having a perfect hallucination can be
justified and have the same justificatory status as the perceptual
judgements one makes when one genuinely perceives the world. According
to this view, there is a sense, then, in which the conclusion of the
tempting line of argument that McDowell considers is true: when you
genuinely perceive the world your epistemic grounds for making
world-directed perceptual judgements are the same as, an hence no
better than, those available to you when you have a subjectively
indistinguishible hallucination. However, those who accept this claim
may deny that this puts into jeopardy the common sense idea that when
we do succeed in perceiving the world we usually do acquire
non-inferential, world-directed, perceptual knowledge. For they may
claim the epistemic difference between a veridical perception and
hallucination is not to be explained by appealing to some difference in
the justificatory status of the judgements that such experiences give
rise to. The epistemic difference is, rather, to be explained by
appealing to the fact that when one perceives the world some further
conditions required for perceptual knowledge will usually be met.




Taking this line might be one way of resisting an epistemic
assumption made in the "tempting" line of argument that
McDowell considers, namely the assumption that matters external to how
things are with you subjectively cannot intelligibly contribute, even
in part, to your epistemic standing on some question. An alternative
way of resisting this epistemic assumption is to accept a view
according to which matters external to how things are with you
subjectively can contribute to the justificatory status of your
beliefs. (For an example of this approach to justification, see Goldman
1979).




According to another line of objection, one that is more sympathetic
to McDowell's general epistemological outlook, one can resist the
tempting line of argument in a way that closely parallels
McDowell's proposal, but without being committed to a disjunctive
view of appearances. Williamson (2000) proposes a view of this kind.
According to this view, when one genuinely perceives the world and sees
that such and such is the case, one is in a factive mental state of
knowing that such and such is the case. This factive mental state can
only obtain when one is veridically perceiving the world, and it cannot
obtain when one is hallucinating. Furthermore, this factive mental
state is not to be given a conjunctive analysis. It is not to be
regarded as being in a state that can be conjunctively analysed in
terms of having an experience that such and such is the case, plus some
further, extra-mental conditions that are 'blankly external to
one's subjectivity'. So the proponent of this view agrees
with McDowell that when one sees that such and such is the case one is
in a distinctive kind of mental state that cannot be conjunctively
analysed. However, the proponent of this view rejects McDowell's
claim that one should give a disjunctive account of appearances. For
accepting that one cannot give a conjunctive analysis of
*seeing* that such and such is case is compatible with saying
that its *appearing to one* that such and such is the case is a
mental state common to genuine perception and hallucination, where such
a state is not to be given a disjunctive characterisation. (For further
discussion of this line of objection, see section 4.3)




A further criticism that has been levelled against McDowell's
proposal is that his disjunctive account of experience fails to bring
with it the epistemic benefits that he advertises it as having.
McDowell has suggested that in showing how the disjunctive account he
recommends allows us to resist the tempting line of argument that he
considers, he has shown us how to "remove a prop" upon
which a certain line of sceptical argument depends. (In particular,
see McDowell 2008). Against McDowell, Wright (2002, 2008) argues that
disjunctivism provides us with nothing to address mainstream
perceptual scepticism. Wright claims that the traditional Cartesian
sceptical argument does not rely on the impossibility of direct
perceptual acquaintance with the world. It allows that you may be
having a perceptual experience that involves a fact in the world
making itself perceptual manifest to you. What it attempts to
undermine is the idea that anything other than agnosticism as to
whether or not you are perceiving is warranted, even in this
situation. (See also Conee 2007, and Byrne 2014.)




In response to this criticism, McDowell has said that in accepting
his disjunctive account of experience we need not pretend to have an
argument that can prove that we are not being deceived using premises
we can affirm without begging the question against the sceptic. What
the disjunctive account does achieve, though, is to show we can resist
sceptical arguments that appeal to the "highest common
factor" conception of experience--that conception of
experience according to which genuine perceptions and subjectively
indistinguishible hallucinations do not differ in their epistemological
significance. For the disjunctive account of experience blocks the
inference from subjective indistinguishability to the highest common
factor conception. According to McDowell's diagnosis, the move
from subjective indistinguishability to the highest common factor
conception depends upon an illegitimate view of self-knowledge. (For a
similar proposal see Williamson 2000). And McDowell argues that this
illegitimate view of self-knowledge itself makes unintelligible a
characteristic of experience that the sceptical argument does not
usually question--that our perceptual experience at least
*purports* to reveal how things are in the objective world.




So an important element of McDowell's disjunctive approach is his
opposition to a certain view of self-knowledge. (See especially
McDowell 1987.) According to the view he opposes, although your
ability to tell how things are in the world by looking is fallible,
your ability to tell how things are with you subjectively is
infallible, in the following sense: the truth about how things are
with you subjectively is infallibly accessible to your capacity to
acquire knowledge on such matters.This picture of self-knowledge is
incompatible with the disjunctive account of experience that McDowell
recommends. According to that disjunctive account when you have an
experience, you can know, independently of whether you know that you
are hallucinating, that it appears to you that such and such is the
case. However, its appearing to you that a such and such is the case
can be either a situation in which a fact in the environment is being
made perceptually manifest to you, or a situation that involves a mere
appearance, and you cannot know which disjunct obtains independently
of knowing whether you are hallucinating. According to McDowell, when
a fact is made perceptually manifest to you, the obtaining of the fact
is not "blankly external to your subjectivity". The
resultant view is incompatible with the claim that *all* of the
truths about how things are with you subjectively are infallibly
accessible to you. For if all of the truths about things are with you
subjectively were infallibly accessible to you, your capacity to know
whether or not you were hallucinating would also be infallible.




For discussion of McDowell's disjunctivism, see Neta 2008,
Pritchard 2008, Sedivy 2008, Brogaard 2011 and Haddock 2011. For
further discussion of McDowell's disjunctivism and comparison
with Austin 1962, see Thau 2004, and for discussion of whether Austin
was a disjunctivist, see also Longworth 2014. For discussion of
epistemological disjunctivism in general, see Pritchard 2012, Sedivy
2019, French 2016 and 2019, Mitova 2019, Littlejohn 2019, Neta 2019,
and Haddock 2019.


### 3.3 A Phenomenological Argument




Martin argues for a naive realist account of the kind of
experience one has when one genuinely perceives the world. According to
this naive realist account, when one genuinely perceives the world
one is directly aware of mind-independent objects and their features.
Furthermore, according to this view, when one perceives the world, the
actual objects of perception, the external things such as trees, and
tables, which one can perceive, and the properties they manifest to one
when perceived, partly constitute one's conscious experience, and
hence determine its phenomenal character. (See Martin's
discussion of naive realism in his 1997, 1998, 2002, 2004, and
2006.) Since one is not aware of mind-independent objects and their
features when one hallucinates, the naive realist cannot offer the
same account of the phenomenal character of hallucinations. The
naive realist is committed, then, to the claim that the kind of
phenomenally conscious episode that occurs when one perceives the world
is not one that could be occurring were one hallucinating. So in order
to preserve his naive realist account of the phenomenal character
of genuine perceptions, Martin advocates a disjunctive account of
perceptual experience. According to Martin, genuine perceptions and
introspectively indiscriminible hallucinations are not mental events of
the same fundamental kind.




Martin's naive realist account of genuine perception is
motivated by phenomenological considerations. He argues that
naive realism best articulates how sensory experience seems to us
to be through introspective reflection. If introspective reflection
supports a naive realist account of the phenomenal character of
genuine perceptions, then presumably introspective reflection should
lend the same support to a naive realist account of the
phenomenal character of hallucinations that are introspectively
indiscriminible from genuine perceptions. Since the naive realist
account of phenomenal character cannot be applied to hallucinations,
the naive realist must then say that hallucinations that are
introspectively indiscriminible from genuine perceptions do not have
the phenomenal character that introspective reflection
suggests--they do not have the phenomenal character that they
introspectively seem to us to have. However, if Martin is right in his
claim that introspective reflection supports naive realism, then
if we reject naive realism, we will have to accept
that *all* perceptual experiences, whether genuine perceptions
or hallucinations, fail to have the phenomenal character that
introspective reflection suggests. (For a similar proposal, see also
Langsam 2017).




As Martin sees it, then, the dialectical position is this: the
disjunctivist naive realist allows that at least some of our
perceptual experiences really do have the phenomenal character that
they introspectively seem to have--namely the genuine
perceptions--whereas the opponent of naive realism needs to
deny that any of our perceptual experiences really do have the
phenomenal character that they introspectively seem to have. So Martin
advocates the disjunctivist naive realist view as the best error
theory concerning perceptual experience and the introspection of
experience.


 The claim that when one genuinely perceives the world one is
directly aware of mind-independent objects and their features is not
distinctive of the naive realist account. For example, someone
who holds an intentionalist account of experience can also accept this
claim. According to this view our perceptual experiences are mental
states with intentional contents that represent the world as being a
certain way, and when one has an experience with a veridical content,
in the right circumstances, one is directly aware of mind-independent
objects in one's environment. (Advocates of such intentionalist
accounts of experience include Searle (1983), Harman (1990), Tye
(1992, 1995, and 2000), Burge (1993 and 2010), Dretske (1995), Byrne
(2001), and Pautz (2010)). Many have argued that this sort of theory
can adequately accommodate the phenomenological aspects of experience
that a naive realist might point to--e.g., the apparent
presence to mind of mind-independent objects and their
features--without being committed to the idea that hallucinations
fail to have the phenomenal character that they introspectively seem
to have.




Martin (2002) compares and contrasts the intentionalist and naive
realist accounts of these phenomenological aspects of perceptual
experience and argues that introspective reflection on the nature of
sensory imagination--in particular, visualising-- gives us
reason to support the naive realist account over the
intentionalist one. Martin's argument for this claim has the following
structure: (i) He compares and contrasts the naive realist and
intentionalist accounts of certain aspects of the phenomenology of
perceptual experience--their transparency and immediacy. (ii) He
argues for a thesis about visualising--the 'dependency
thesis', which states that to visualise an *F* is to
imagine a visual experience of an *F*. (For an influential
discussion of this idea, see Williams 1973. For an endorsement of the
view, see Peacocke 1985 and Vendler 1984.) (iii) He argues that the
truth of the dependency thesis should lead the intentionalist and the
naive realist to make different predictions about the
phenomenology of visualising, given their different accounts of the
transparency and immediacy of perceptual experience. So, he claims,
the phenomenology of visualising can be regarded as a test of these
competing views. (iv) He argues that the phenomenology of our episodes
of visualising favours the naive realist account.




The particular phenomenological aspects of perceptual
experience--transparency and immediacy--that the naive
realist and the intentionalist try to accommodate in different ways,
are the following. *Transparency*: When one attends to what it
is like for one to have a visual experience it seems to one as though
one does so through attending to mind-independent objects in one's
environment and *their* features. *Immediacy*:
Furthermore, our perceptual experiences are non-neutral about the
actual presence of the mind-independent objects and features in our
environment they are directed upon. They appear to have a coercive
power and authority over our beliefs. Even if one believes that one is
hallucinating, the phenomenal immediacy of the experience--its
non-neutrality about the actual presence of mind-independent objects
and features in our environment--is not thereby extinguished.
Intentionalists can explain the transparency and immediacy of
perceptual experience in terms of the idea that (a) perceptual
experiences are mental states with intentional contents that represent
the mind-independent world as being a certain way (hence
transparency); and in terms of the idea that (b) such states play a
distinctive kind of functional role in our mental economy (hence
immediacy). This is not the account offered by the naive
realist. For the naive realist, one's experience relates to the
world in a non-representational manner. According to the naive
realist, the transparency and immediacy of genuine perceptions are
explained in terms of the idea that mind-independent objects and their
features are constituents of one's perceptual experience that
determine, at least in part, the phenomenal character of that
experience. The phenomenal transparency and immediacy of a
hallucination is explained derivatively--in terms of its being
introspectively indiscriminible from something it is not--a
mental event with the phenomenal character of a genuine
perception.




On the face of it, the intentionalist appears to be able to
accommodate adequately the transparency and immediacy of experience
without committing to the idea that hallucinations fail to have the
phenomenal character that introspective reflection suggests. This might
lead one to favour the intentionalist view. However, Martin argues that
reflecting on the phenomenology of visualising gives us reason to think
otherwise.




Martin argues that in order to capture adequately the respect in which
the phenomenology of visualising an *F* has some correspondence
with the phenomenology of having a visual experience of an *F*,
we should accept the dependency thesis--the thesis that to
visualise an *F* is to imagine a visual experience of
an *F*. He then argues that the truth of the dependency thesis
should lead the intentionalist and the naive realist to make
different predictions about the phenomenology of visualising. Martin
argues that if the dependency thesis is correct, then the
intentionalist should hold that when we visualise, we imagine a mental
state (i.e., a visual experience) that represents the world to be a
certain way and that has a distinctive kind of functional role. We
may, as part of our imaginative project, suppose that the imagined
situation contains the objects and features represented by the
imagined visual experience, but, argues Martin, the intentionalist
should predict that (a) when one visualises something, e.g., an apple,
the imagistic character of one's visualising should itself be neutral
with respect to whether or not one is imagining a scene that contains
an apple, and (b) something other than the putative object of
experience (i.e., the apple) should be available to introspection. The
representational properties of the experience one is imagining should
be revealed to one as such.




According to Martin, as the naive realist offers a rather
different account of the phenomenal transparency and immediacy of
visual experience, the naive realist should make rather different
predictions about the phenomenology of visualising. According to the
naive realist, a visual experience of an apple seems to its
subject to be *constitutively* dependent on the presence of the
apple. So given the truth of the dependency thesis, the naive
realist should predict that when one visualises an apple, the
imagistic character of one's visualising won't be neutral
with respect to whether or not one is imagining a scene that contains
an apple. It should be committal on the presence of an apple in the
imagined scene. Martin claims that the actual phenomenology of
visualising is more in keeping with what the naive realist
predicts. He argues that as introspective reflection best supports the
naive realist prediction, we can either deny naive realism
and hold that none of our perceptual experiences have the phenomenal
character that introspective reflections suggests, or we can accept a
naive realist account of genuine perceptions and hold that only
some of our perceptual experiences fail to have the phenomenal
character that introspective reflection suggests. This latter
position, according to Martin, is the least revisionary option.




One line of objection against Martin's argument targets the
dependency thesis. For example, Noordhof (2002) and Burge (2005)
question the plausibility of a claim that appears to be a commitment of
the dependency thesis: that in visualising an object one must be
imagining a perceptual experience of the object, despite the fact that
imagining the experience may have been no part of your imaginative
project. Some opponents of the dependency thesis have argued that the
correspondences between visual experience and visualising are to be
accounted for by the fact that there are similarities in the
representational contents of these episodes. (See Noordhof 2002 and
Currie and Ravenscroft 2002.)




An alternative response to the argument may be to accept the
dependency thesis, but to question whether introspective reflection
really does support the claim that the imagistic character of
visualising an apple is itself non-neutral with respect to whether the
imagined scene contains an apple. It might be held instead that the
phenomenology of an episode of visualising does not speak to such
matters independently of the question of what suppositions the subject
is making in engaging in his imaginative project (see Burge 2005).
Alternatively, one might raise a more general scepticism about the
reliability of appeals to introspection in supporting claims about the
real nature of perceptual experiences (see Spener 2003). Some may hold
that since we must allow that hallucinations do not have the sort of
phenomenal character that introspective reflection suggests, there is
little additional cost in allowing that veridical perceptions also
fail to have the phenomenal character that introspective reflection
suggests. (For critical discussion of Martin's argument, see
also Dorsch 2010.)


### 3.4 An Argument from Epistemic Modesty




According to Martin, properly understood, disjunctivism offers us an
epistemological perspective on how we should conceive of debates about
perceptual experience. Martin suggests that the key to the disjunctive
approach lies not in its appeal to paraphrasing claims about experience
in disjunctive form, but rather in its appeal to the epistemic notion
of *indiscriminability* in explicating the claims we make about
perceptual experience. (For detailed discussion of the notion of
discriminability, see Williamson 1990). Martin suggests that what is
distinctive of the disjunctive approach is the 'modesty' of
the claims it makes about what one can know about one's
perceptual experiences. In contrast, the alternatives to the
disjunctive approach are 'immodest' in their assumptions
about our epistemic powers. The alternatives to the disjunctive
approach that Martin appears to have in mind here are those versions of
the common element view that hold that (a) there are phenomenal
properties that are common to perceptions, illusions, and
hallucinations, and (b) the possession of such properties is both
necessary and sufficient for an event to be a conscious perceptual
experience.




Martin's argument for the claim that the alternatives to the
disjunctive approach incur greater epistemic burdens primarily focuses
on our understanding of the notion of a perfect hallucination.
Sceptical arguments often introduce talk of 'perfect
hallucinations'. On one understanding such talk is taken to
be introducing the notion of a conscious mental event that is not a
genuine perception but which is introspectively indiscriminible from a
genuine perception of the world. An assumption often
made is that such an experience would have the same phenomenal
properties as some possible genuine perception. But from the fact that
a conscious mental event is introspectively indiscriminible from a
genuine perception, does it follow that *must* have the same
phenomenal properties as a genuine perception?




Suppose we answer that this does not follow--i.e., we accept that
it may be possible, in principle, for there to occur a conscious
mental event that is introspectively indiscriminible from a genuine
perception, but which does not have the same phenomenal properties as
a genuine perception. Should we say that such events count as
perceptual experiences? If one denies that such mental events should
be regarded as perceptual experiences, then, Martin suggests, one owes
some kind of justification for this denial, for this stance on what is
required for a mental event to be a perceptual experience will seem,
from a common sense perspective, to be too restrictive. On the other
hand, if one holds that such mental events should be regarded as
perceptual experiences, then this suggests that our most inclusive
notion of what it is for something to be a perceptual experience is an
epistemic one--that of being introspectively indiscriminible from
a genuine perception--which does not involve the further
metaphysical assumption that perceptual experiences which aren't
genuine perceptions must have the same phenomenal properties as
genuine perceptions.




Now suppose instead that we say that if a conscious mental event is
introspectively indiscriminible from a genuine perception it has the
same phenomenal properties as a genuine perception. According to Martin
this would be to embrace a substantive epistemic principle. For in
adopting this stance one would be committed to the epistemic claim that
in the case of any conscious mental event that lacks the phenomenal
properties of a genuine perception, the fact that it lacks the relevant
phenomenal properties will be something that is knowable through
introspection. According to such a view, it is not just that the
phenomenal properties that determine an event as an experience are held
to be introspectively detectible and recognisible as such when present.
It must also be the case that the absence of such properties, when they
are absent, is equally detectible through introspection.




According to Martin, given that this approach to perceptual
experience needs to rely on this epistemic assumption, it carries more
theoretical burdens than does the more "modest"
disjunctivist approach. For when it comes to characterizing the notion
of perceptual experience in general, the disjunctive approach
emphasizes the *limits* of our powers of discrimination, rather
than appealing to a substantive condition that an event must meet to be
an experience, and in addition ascribing to us cognitive powers to
recognize the presence of this substantive condition. So, according to Martin, the
burden is really on the common element theorist, either to show that
the extra epistemic commitment is one we should accept, or
alternatively, to justify the claim that those conscious mental events
that are introspectively indiscriminible from genuine perceptions but
which lack the phenomenal properties of genuine perceptions should not
be regarded as a perceptual experiences. This argument does not purport
to show that the common element view is wrong, but rather to show that
the default position should be that of the disjunctivist.




Various objections have been raised against Martin's proposal.
Some object to Martin's suggestion that being subjectively
indiscriminible from a genuine perception is a sufficient condition
for being a perceptual experience. Siegel (2004 and 2008), Hawthorne
and Kovakovich (2006), Smith (2008), and Byrne and Logue (2008) push
this line of objection. In effect, such objectors may be seen as
attempting to meet one of Martin's challenges by offering reason
to think that our notion of perceptual experience is, after all, more
restrictive than the epistemically characterised one he proposes.
Siegel objects that a cognitively unsophisticated creature, such as a
dog, will be incapable of introspectively discriminating the
experiences they have. So we cannot appeal to the notion of subjective
indiscriminability in our account of what makes it the case that the
dog has a perceptual experience of an *F*. Byrne and Logue
(2008) and Smith (2008) object that even in the case of a cognitively
sophisticated subject we should not rule out the possibility of the
occurrence of a conscious mental event that is not a perceptual
experience, but which is subjectively indiscriminible from a veridical
perception. For example, it might be argued that we should deny that
episodes of perceptual imagining (e.g., visualising) are perceptual
experiences, and we should allow that it may be possible for an
episode of visualising to be subjectively indiscriminible from a
veridical perception. One might think that just such episodes occur
when one is dreaming. (For example, see Ichikawa 2009). Keith Allen
(2015), on the other hand, argues that hallucinations are degenerate
kinds of sensory imagination and that the view that hallucination is a
kind of sensory imagination represents a promising account of
hallucination from the perspective of a naive realist theory of
perception like naive realism.




If one does allow that conscious mental events of different kinds
(e.g., perceptual experiences and perceptual imaginings) can be
introspectively indiscriminible, then it seems that one's defence
of the claim that perfect hallucinations and genuine perceptions are
events of the same fundamental kind cannot simply appeal to the fact
that they are introspectively indiscriminible. One might, nonetheless,
think that there is introspective support for the claim that genuine
perceptions have phenomenal properties which are such that (i) an
event's possession of them is independent of the conditions of
perception, and (ii) an event's possession of them is sufficient
to account for the fact that the event is introspectively
indiscriminible from a genuine perception. One might then simply define
'perfect hallucinations' as those experiences that are not
genuine perceptions, but which have the same phenomenal properties as
genuine perceptions. (See section 3.3 for discussion of Martin's
positive argument for Naive Realism, which can be seen as an
attempt to challenge such claims.)




According to another line of objection, Martin is wrong to propose
that being introspectively indiscriminible from a genuine perception is
a necessary condition for being a conscious perceptual experience. For
although being introspectively indiscriminible from a genuine
perception may be a condition satisfied by all genuine perceptions and
*perfect* hallucinations had by subjects capable of making
introspective judgements about their perceptual experiences, it is not
a condition that need be satisfied by other perceptual
experiences. For instance, Siegel (2004) argues that experiences as of
impossible scenes--e.g., experiences as of certain Escher
scenes--do not satisfy this condition.




Siegel (2004) also suggests that, properly understood, the epistemic
burden incurred by the common element theorist is not so great after
all, as it leaves open the possibility that subjects may make all kinds
of mistakes about the kinds of experiences they are having. One's
view on whether or not the epistemic commitment that is being
attributed to the common element theorist by Martin is excessively
burdensome may depend, in part, on how one understands the notion of
introspective indiscriminability in play in his argument. This may also
affect how plausible one finds the claim that being introspectively
indiscriminible from a genuine perception is necessary and sufficient
for being a perceptual experience. Martin's views on these issues
are discussed further in section 5.1.


### 3.5 An Argument from Demonstrative Reference


 John Campbell (2002a, 2002b, 2005, 2011) has argued that there is
an important connection between the nature of the conscious perceptual
experience that occurs when we veridically perceive the world and our
ability to think demonstratively about the mind-independent objects
that we perceive. He argues that only a 'relational view of
experience' can adequately acknowledge the role of conscious
experience in making it possible for us to think demonstratively about
the categorical properties of the mind-independent objects we
perceive, and this relational view of experience commits him to a form
of disjunctivism about perception.




According to this relational view of experience, when you veridically
perceive the world the mind-independent objects and properties you
perceive are constituents of your conscious experience--the
qualitative character of the conscious experience you undergo is
constituted by the qualitative characters of the mind-independent
items you perceive. This kind of experience cannot occur when you
hallucinate--veridical perceptions and hallucinations are
experiences of different conscious kinds--hence the commitment to
disjunctivism. More precisely, according to the relational view of
experience that Campbell endorses, we are not to think of perceptual
consciousness of an object as a two-place relation between a person
and an object, but rather as a three-place relation between a person,
a *standpoint*, and an object. Campbell suggests that we need
to factor in the notion of a 'standpoint' as our
experience of objects is always in some sense partial. You always
experience an object from a standpoint, and you can experience one and
the same object from different standpoints. (For a similar proposal,
see Brewer 2011 and 2017a. For further discussion of this aspect of
naive realism, see French 2018 and Christy 2019).




Campbell argues that an adequate account of the nature of our
conscious experience of objects should accommodate the fact that such
conscious experience performs a significant explanatory role. According
to Campbell, such conscious experience provides us with knowledge of
what our perceptual demonstrative terms, like 'this' and
'that', refer to. Furthermore, according to Campbell, the
knowledge of the semantic value of the demonstrative that such
conscious experience provides us with, justifies and causes the pattern
of use we make of that demonstrative in our reasoning. The relevant
patterns of reasoning we engage in reflect our conception of the object
referred to as mind-independent. So, Campbell argues, our conscious
experience of objects has a role to play in explaining what provides us
with our conception of the objects of perception as mind-independent.
Campbell argues that it is only the relational view of experience that
can adequately acknowledge the way in which conscious experience plays
this explanatory role, so competing accounts of experience should be
rejected.




Note that the explanatory role that Campbell is suggesting that our
conscious experience of objects is supposed to play isn't simply that
of justifying, or providing warrant for, our beliefs and judgements
that employ perceptual demonstratives. His claim is rather that such
experience has a role to play in justifying the patterns of use we
make of the demonstrative in reasoning that we engage in--where
such reasoning reflects our grasp of the criteria of identity of the
object referred to, which in turn reflects our grasp of the object as
being mind-independent. According to Campbell, this pattern of use is
justified by appeal to the semantic value of the demonstrative. Our
conscious experience of the object to which the demonstrative refers
provides us with a form of knowledge of the semantic value of the
demonstrative, and thereby plays a role in justifying the use we make
of the demonstrative in our reasoning.




Campbell argues that one cannot adequately acknowledge the way in
which conscious experience plays this explanatory role if one holds a
view of experience according to which an experience is a mental state
or event with an intentional content that represents the world as
being a certain way. For such a view of experience at best presupposes
what is to be explained. It presupposes what is to be explained if the
content of such a representational state is conceptual, and it doesn't
have the resources to play the relevant explanatory role if its
representational content is non-conceptual. What's required, argues
Campbell, is a conception of experience as something less than
conceptual representation of the object of experience, but which
nonetheless has the resources to explain how experience of an object
can provide one with a form of knowledge of the semantic value of a
demonstrative that refers to it. Campbell argues that the only
adequate contender is the relational view, for according to the
relational view one's conscious experience in the veridical case
*acquaints* one with a mind-independent object and its
categorical properties. This confrontation with, this awareness
*of*, the mind-independent object referred to is what provides
one with the relevant form of knowledge of the semantic value of the
demonstrative that allows experience to play its explanatory role.




As Campbell himself points out, his argument presses very hard the
idea that experience of objects has this explanatory role to play. Some
issues of contention here are the following: (a) Whether an account of
the nature of conscious experience really does have a role to play when
it comes to an explanation of the fact that we have a conception of
objects in the world as mind-independent. (b) If the nature of
conscious experience does have such an explanatory role to play,
whether it is the one that Campbell identifies--i.e., that of
causing and justifying the use we make of demonstrative terms that
refer to the mind-independent objects we perceive. (c) Whether the
relational view of experience really does have the resources to play
the explanatory role that Campbell assigns to it. (For criticism of
Campbell's argument, see Burge 2005, Rey 2005, and Cassam 2011).


### 3.6 Further Motivations for Disjunctivism




This section briefly summarises some further considerations that
have been appealed to in motivating disjunctive accounts of perceptual
experience.




Some have argued that a genuine perception of the world is a
perceptual state with an intentional content containing demonstrative
elements that refer to the items perceived. (See Brewer 2000, Burge
1993, and Tye 2007, Scellenberg 2010, 2013, and 2016. For objections
to this idea see Davies 1992 and McGinn 1982.) Acceptance of this
view, together with two further assumptions, can lead to the
conclusion that the kind of experience that occurs when one perceives
the world isn't one that can occur when one hallucinates, which
in turn can motivate a disjunctive approach to perceptual experience
in general. The two further assumptions are the following. (a)
Truth-evaluable intentional contents with demonstrative elements that
successfully refer are object-dependent, and (b) experiences are of
the same mental kind only if they have the same truth-evaluable
contents. (The latter claim is endorsed by Evans 1981, 1982 and
McDowell 1984. For criticisms of this claim see Burge 1983, 1993,
2005, 2010, and Martin 2003).




Brewer advocated a view of this form in his book *Perception and
Reason*. In his more recent work on perceptual experience he has
proposed an alternative view of genuine perception, but which also
commits to disjunctivism about perceptual experience. (See Brewer
2004, 2006, 2008, 2011, 2017a, and 2017b.) In this work Brewer is
concerned to identify and defend the account of experience that he
thinks is most conducive to our common sense 'empirical
realist' world-view--the view that the tables, trees,
people and animals etc, that we sense, are as they are independently
of anyone's thought or experience of them. Brewer argues that
the 'Object View' of experience, which he contrasts with
the 'Content View', is the most promising such
account. According to this 'object view', perception is an
acquaintance with mind-independent empirical things whose basic
natures and perceptible qualities constitute what it is like to be
presented with them in this way. A similar line of empirical realist
line of thought can be found in Campbell's work. (For example,
see Campbell and Cassam 2014. For a related line of thought, see also
Logue 2012b). Campbell argues that only a naive realist account of the
phenomenal character of perception can accommodate an epistemic role
that conscious perception plays in grounding the concepts we possess
of mind-independent objects and the qualities we perceive. For
example, he argues that only a naive realist account of phenomenal
character can adequately capture the following two ideas: (i) The
phenomenal character of perception plays a crucial role in explaining
our distinctive conceptions of what our colour terms refer to, and
(ii) our colour terms refer to mind-independent qualities of
objects. (For discussion of Campbell's view, see Soteriou 2016,
Ch. 4. For objections to Campbell's arguments, see
Cassam's contribution to Campbell and Cassam 2014. For
objections to the view of colour defended by Campbell, see Pautz
forthcoming. For further discussion of this issue, see Kalderon 2011,
Allen 2016, and Beck 2019).




One significant recent source of motivation for disjunctivism (common
to the views proposed by Martin, Campbell and Brewer) is the
suggestion that we should moving away from representationalist
accounts of the way in which our minds are intentionally directed upon
the mind-independent world when we perceive it. Influential in this
regard is Charles Travis's work on perception. Travis (2004 and
2013), who cites Austin's *Sense and Sensibilia* as an
important influence, argues that perception is not
representational. He offers a critique of a representationalist view
that is committed to the following claims: (i) Experiences have
representational contents and can be true / false--veridical
/non-veridical; (ii) the representational content of an experience is
something that the subject can take at face value, and accept, or
decline; (iii) the experience having this content isn't a matter
of the subject taking / judging things to be a certain way; and (iv)
the way our experience represents things to be is something we can
appreciate and recognize. According to Travis's alternative view
of perception our senses confront us with what is there, they bring
our surroundings into view, but there is nothing in a perceptual
experience to make it count as having some one representational
content as opposed to countless others. In making out, or trying to
make out what it is that we are confronted with,
*we* may go wrong, and make false judgements, but when we are
misled in this way, this is not because our senses non-veridically
represent to us that the world is a certain way. On the assumption
that we are not confronted with the mind-independent world when we
hallucinate, this sort of view naturally leads to a disjunctivist view
of perceptual experience. (For discussion of these issues, see Raleigh
2013, Shahmoradi 2016, and Wilson 2018).


## 4. Objections to Disjunctivism




Some of the objections raised against disjunctive theories are
directed at the specific arguments proposed in support of different
versions of disjunctivism. For discussion of objections to the
arguments proposed by Hinton and McDowell, see sections 3.1, and 3.2;
and for objections to arguments proposed by Martin see sections 3.3
and 3.4. For objections to disjunctivist accounts of hallucination,
see section 5. Some arguments against certain versions of
disjunctivism are directed against what are taken to be some of the
metaphysical commitments of the naive realist account of veridical
perception. For example, Pautz (forthcoming) argues that naive realism
about veridical perception carries commitments about the metaphysical
status of observable qualities, such as colour, that are undermined by
empirical science. This section discusses arguments aimed at a more
general level, against the disjunctivist's denial that veridical
perceptions, illusions and hallucinations are mental events of the
same fundamental kind, and in favour of the view that there is common
element to veridical perception, illusion and hallucination.


### 4.1 The Explanatory Power of the Common Kind Claim




Sturgeon (1998) offers a number of reasons for thinking that our
default view should be the thesis that there is a common factor to
veridical perceptions, illusions and hallucinations--i.e., the
thesis that they all involve perceptual states of the same basic
kind--rather than the disjunctivist view.




Sturgeon points to a number of features that can be common to
veridical perceptions, illusions, and hallucinations. Among the
features he points to are the following: (i) veridical perceptions,
illusions and hallucinations can produce similar behavioural effects.
For example, in general, if it sensibly appears to you as though a
rock is flying towards you, you will duck, irrespective of whether the
experience you are having is a veridical perception, an illusion, or a
hallucination. (ii) If, on the basis of that experience, you believe
that a rock is flying towards you, and you act on that belief and
duck, there is a sense in which your belief and action are rational,
irrespective of whether that experience is a veridical perception, an
illusion, or a hallucination. (iii) If you have an experience as of a
rock flying towards you, you can know what it's like to see a rock
flying towards you, irrespective of whether that experience is a
veridical perception, an illusion, or a hallucination. (iv) Veridical
perceptions, illusions and hallucinations can be introspectively
indistinguishible.




Sturgeon suggests that the most obvious explanation of the fact that
these experiences share these features is the proposal they all involve
mental states of the same kind. So this should be our default view
until we are given reason to be persuaded otherwise.




The disjunctivist may try to explain the fact that illusions and
hallucinations can have the same kinds of behavioural effects as
veridical perceptions by simply appealing to the fact that such
experiences can be subjectively indistinguishible from veridical
perceptions. Since the difference between a hallucination and a
veridical perception may be something that a subject is unable to
detect through introspection, the hallucination will naturally give
rise to effects that are similar to those of the veridical perception.
The subject will respond to such a hallucination in the same kind of
way in which she would respond to a veridical perception. And there is a
sense in which this response can be regarded as rational.




However, the disjunctivist who denies that a hallucination can have
the same phenomenal character as a veridical perception will be put
under pressure to offer some positive explanation of the fact that a
hallucination can seem to have the same phenomenal character as a
veridical perception, and in particular, to offer some explanation of
how it is that a subject can come to know what it is like to have a
veridical perception of an *F* through simply having a
hallucination of an *F*, given that the hallucination does not
actually possess the what-it-is-like properties of the veridical
perception. As Hellie (2007) notes, while not *everything* is
the way it appears, there is a strong intuition that the phenomenal
domain is distinctive--if an experience appears to have a certain
phenomenal property, then it has that property as phenomenal
character. The tenability of the form of disjunctivism that denies
that veridical perceptions and hallucinations can have the same
phenomenal character will depend on whether this epistemic assumption
can plausibly be denied (see the discussion of this point in section
3.4), and whether the disjunctivist can make a satisfactory case for
thinking that veridical perceptions appear to have a phenomenal
character that hallucinations could not possess (see section 3.3).


### 4.2 The Causal Argument Against Disjunctivism




An influential argument against disjunctivism is the causal
argument, first proposed by Howard Robinson (see Robinson 1985 and
1994). The simplest version of the argument appeals to the following
two claims: (i) It is theoretically possible, by activating some brain
processes involved when a subject genuinely perceives the world, to
cause a hallucination subjectively indistinguishible from that
perception--a 'causally matching' hallucination.
(ii) It is necessary to give the same account of the experiences
involved in genuine perception and hallucination when they have the
same neural causes. So we should accept that the kind of
experience that occurs when a subject perceives the world is one the
subject could be having if she were hallucinating.




The general principle behind this second claim is 'same
proximate cause, same immediate effect'. It is likely that the
disjunctivist will simply reject this principle. The disjunctivist may
insist that in a case of genuine perception, even if the objects of
perception are distal causes of the subject's experience, they
are also figure non-causally as essential constituents of it. So the
occurrence of the relevant brain processes won't be sufficient to
produce the kind of mental event involved in perception, unless further
non-causal conditions necessary for the occurrence of that kind of
mental effect also obtain. At this point, the disjunctivist and her
opponent may simply disagree as to whether there are any psychological
effects that have significant non-causal constitutive conditions
attached. And this connects with familiar debates as to the tenability
of externalist views in the philosophy of mind. (For further discussion
of the causal argument see Langsam 1997, Snowdon 2005b, and Martin
2004).


### 4.3 Neither Conjunctivism Nor Disjunctivism




There is another version of the causal argument that can be used to
put pressure on the disjunctivist to accept that there is a common
element to veridical perception and causally matching hallucination.
(See Johnston 2004 and Martin 2004.) The proponent of this argument may
allow for the possibility that there are non-causal constitutive
conditions necessary for the occurrence of certain kinds of mental
events, where such constitutive conditions may include the presence in
the environment of appropriate candidate objects of perception.
So this version of the causal argument can accommodate the
disjunctivist's claim that there are significant non-causal
conditions necessary for the occurrence of the kind of experience that
occurs when one veridically perceives the world. What this version of
the causal argument relies upon is, rather, the claim that there are no
such significant non-causal conditions necessary for the occurrence of
the kind experience that occurs when one *hallucinates*. The
proponent of this modified causal argument claims that there are no
non-causal conditions necessary for the occurrence of the kind of
experience that occurs when one hallucinates that cannot also obtain
when one veridically perceives the world. So whatever kind of
experience occurs when you have a causally matching hallucination of an
*F* will also be produced when you have a veridical perception
of an *F*. So there is, after all, a common element to
veridical perception and causally matching hallucination.




Can the disjunctivist respond by saying that there is a non-causal
constitutive condition necessary for the kind experience that occurs
when one hallucinates--namely the *absence* of an
appropriate candidate object of perception in the subject's
environment? A problem with this response is that it relies on
characterising the kind of psychological effect involved in
hallucination in terms of what it is not, namely a veridical
perception, and it is plausible to demand that it should be possible to
provide some *positive* account of the kind of psychological
effect involved when one hallucinates.




This version of the causal argument does not rely on the general
principle 'same proximate cause, same immediate effect',
so a proponent of the argument may allow that there is a kind of
mental event that occurs when one perceives the world which
doesn't occur when one hallucinates. Moreover, a proponent of
the argument may also allow that there is an explanatory role to be
played by the kind of mental event that only occurs when one perceives
the world, which cannot be performed by appealing to the kind of
mental event that is common to perception and illusion, plus some
further non-mental conditions. (For this idea see Peacocke 1993 and
Williamson 2000). However, the argument does put pressure on the
disjunctivist to accept that there is a certain kind of mental event
common to perception and hallucination--one that we should be
able to give a positive, non-disjunctive account of. (See Burge 2005,
2010 and 2011 for arguments to the effect that a denial of this claim
is empirically untenable and incompatible with the methodology of
vision science.) It suggests that if one simply wants to claim that
genuine perceptions are mental events of a kind that cannot occur when
one hallucinates, one should not be concerned to argue for a
disjunctive account of perceptual experience. One's concern
should simply be to oppose a conjunctive account of genuine
perception. (For this line of criticism see Williamson 2000 and
Johnston 2004).




One may be able to accept that a veridical perception and a
hallucination differ mentally, while also accepting that they have a
common mental core. Mark Johnston offers an account of hallucination
along these lines. He proposes that there is a respect in which the
objects of hallucination and the objects of seeing are akin. According
to Johnston, the objects of a subject's hallucination are
complexes of sensible qualities and relations that are not instantiated
in the scene before him, whereas the objects of veridical perception
are spatio-temporal particulars instantiating such complexes. On this
view, there is, then, a common mental core to veridical perception and
hallucination. In both cases one is aware of a 'sensible
profile'--a complex of qualities and relations.




The disjunctivist is generally willing to concede that perceptions
and subjectively indistinguishible hallucinations have
*something* in common. So why should they not accept that what
is common to perception and hallucination is the occurrence of a
certain kind of mental event whose nature is one that we can give a
positive, non-disjunctive account of?


 Martin argues that the naive realist disjunctivist should
deny that it is possible to give a positive, non-derivative account of
the kind of phenomenal event that occurs when one hallucinates. (This
is to oppose the suggestion made in Dancy 1995. See Martin 1997, 2004
and 2006. For discussion see Nudds 2009.). For if the naive
realist does offer a positive, non-derivative account of the kind
phenomenal event that occurs when one hallucinates, and she also
accepts that this kind of event also occurs when one perceives the
world, then she will be under pressure to explain why the occurrence of
this kind of event doesn't screen off the explanatory role that she
assigns to her naive realist account of the phenomenal character
of genuine perception. (For critical discussion of this objection, see
Hellie 2013). Martin's response to the argument is to say that the
naive realist should affirm that in the case of a causally
matching hallucination, there is no more to the phenomenal character
of such an experience than that of being introspectively
indiscriminible from a certain genuine perception. In the case of the
causally matching hallucination its subjective character is exhausted
by its possession of the negative epistemic property--that of
being introspectively indiscriminible from a veridical perception.




It might now be objected that this disjunctivist response still
introduces a common element to veridical perception and causally
matching hallucination that screens off the explanatory role that the
naive realist assigns to her distinctive account of the
phenomenal character of veridical perception. Both a veridical
perception of an *F* and a causally matching hallucination
possess the negative epistemic property of being introspectively
indiscriminible from a veridical perception of an *F*. So why
doesn't this screen off any explanatory role that the naive
realist might assign to the phenomenal properties that she claims only
a veridical perception can possess? Martin's response is to
suggest that the property of being indiscriminible from an *F*
has an explanatory potential which is dependent on the explanatory
potential of *being* an *F*. So the property of
actually being a veridical perception, and having the phenomenal
properties that only a veridical perception can possess, can still be
regarded as having a crucial explanatory role to play.




However, this response still leaves the naive realist in the
position of having to deny that it is possible to provide a positive
account of the phenomenal character of a causally matching
hallucination. Many have argued that this claim is ultimately
untenable. So the modified causal argument can be seen as part of an
attempt to force the naive realist disjunctivist into an untenable
position with respect to causally matching hallucinations.


## 5. Disjunctivist Accounts of Hallucination and Illusion




This section is concerned with what disjunctivists say about the
following: the nature of the kind of mental event that occurs when one
hallucinates, the nature of the kind of mental event that occurs when
has a perceptual illusion, and what the differences between such events
might be.


### 5.1 Hallucination




Some disjunctivists say relatively little about the nature of
hallucination (e.g., McDowell, Campbell and Brewer). For example,
McDowell characterises hallucinatory experience as a "mere
appearance" that such and such is the case, which seems to leave
open whether a more positive account can potentially be given. Dancy
(1995) suggests that the disjunctivist should offer a more direct
characterization of the kind of experience that occurs when one
hallucinates, rather than simply characterising it solely by saying
that it is like what it is not. He suggests that in a fully explicit
version of the disjunctive theory hallucination would be characterised
in a direct, positive way.




The disjunctivist who allows that veridical perceptions and
hallucinations can have the same phenomenal character may take up this
suggestion. (See Logue 2012a and 2013.) This disjunctivist may be able
to provide some positive account of the phenomenal character that
veridical perception and hallucination can share, while allowing that
there are certain mental properties distinctive of veridical
perception (e.g., its possessing an object-dependent intentional
content.) However, for reasons explained in the previous section,
Martin argues that the disjunctivist who is a naive realist about
the phenomenal character of veridical perception (and so who holds
that veridical perceptions have phenomenal properties that
hallucinations cannot possess) should reject Dancy's
proposal. Martin commits to the claim that in the case of certain
hallucinations (i.e., those which have the same kind of proximate
cause as veridical perceptions), there is no more to their phenomenal
character than that of being introspectively indiscriminible from a
veridical perception.




This particular claim has drawn a great deal of criticism. Siegel
(2004) argues that Martin's account fails to accommodate the
different kinds of hallucinations that can be experienced by a creature
who lacks the conceptual capacities to make introspective judgements
about its experience. E.g., suppose a dog is having a hallucination. Due
to conceptual incapacities the dog is not in position to know that he
is not perceiving a tomato, so for the dog this experience is
introspectively indiscriminible from a perception of a tomato. However,
from this fact alone it does not follow that the dog is having a
hallucination of a tomato.




Siegel (2004) also argues that Martin's account fails to capture the
fact that our hallucinations are phenomenally conscious, for a state
that is not phenomenally conscious can satisfy the description of
being introspectively indiscriminible from a genuine
perception. Furthermore, she argues (in Siegel 2008) that Martin's
account cannot adequately explain certain effects of
hallucinations--i.e., what grounds one's positive knowledge of
the kind of experience one is and isn't having. Along related lines,
Sturgeon (1998) suggests that the disjunctivist who denies that it is
possible to provide a positive account of the phenomenal character of
a hallucination does not have the resources to explain adequately how
it is that having a hallucination of an *F* can provide one
with positive knowledge concerning what it is like to veridically
perceive an *F*. (See also Pautz 2010 and 2011.) Johnston
(2004) argues that the disjunctivist offers no satisfactory
explanation of the fact that hallucination can provide us with
original de re knowledge of quality (e.g., the fact that a
hallucination as of a red object can provide its subject with de re
knowledge of the quality of redness).




Martin (2006) attempts to defend his account of hallucination
against his critics, by (a) focusing on the issue of how we should
understand the notion of indiscriminability in play in his talk of
'introspective indiscriminability', and (b) focusing on the
question of the model of introspection we should adopt when our concern
is with the way in which we introspect our phenomenally conscious
mental states. Both aspects of Martin's defence of his view have
been contested.




Martin suggests that the notion of indiscriminability that the
disjunctivist should appeal to is an 'impersonal',
'objective' one. He compares the way in which we can talk
of objects being visible or invisible. He suggests that in certain
contexts, when we say that something is invisible, we may not be
talking about the way a given individual, or group of individuals, is
such that they cannot succeed in seeing the object. We may rather be
talking about what *vision* can and cannot discern. Furthermore,
in asking what vision can reveal to us, we can ask in terms of how
vision actually is, or ways in which vision *could* be. The most
extreme claim of invisibility would be concerned with the latter
notion. The suggestion seems to be that we should not think that such
'impersonal', 'objective' talk of invisibility
need be reducible to claims about what a given subject, group of
subjects, or ideal subject would or would not see. So similarly, we
should not take the impersonal, objective talk of introspective
indiscriminability as reducible to claims about what a given subject,
group of subjects, or ideal subject would or would not come to know
through introspection.




Martin notes an objection that this comparison with sight might give
rise to. When two objects are impersonally indiscriminible through
sight, we tend to think that the objects in question must share a
property--an appearance--that is detectible through
vision. The fact that two visible objects cannot be told apart by sight
suggests that there is something in common between them that sight does
detect. So we might also think that if two experiences are
introspectively indiscriminible, these experiences must share a
property--a phenomenal property--that introspection is
tracking. Martin's response to this objection is to reject a
model of introspection that he thinks lies behind it. Martin suggests
that in a case in which two objects are impersonally visually
indiscriminible, we are led to posit a common appearance the objects
share that vision can discern, because we think of sight as a mode of
coming to be aware of a realm independent of it. So, according to
Martin, the same story will apply to the case of introspection only if
we suppose that when one introspects the phenomenal character of
one's experience one is detecting features of some realm that is
independent of one's introspective access to it. Martin argues
that if one adopts this model of introspection then one will either
have to allow that it is possible for one's experience to have a
real phenomenal nature rather different from the one it introspectively
seems to have, which remains inaccessible to introspection, or one will
have to accept that introspection involves the use of a
"super-mechanism", which tracks the phenomenal character of
one's experience in a such a way that it cannot fail, or can only
fail when it is knowable that it has.




On Martin's recommended alternative, a subject's introspective perspective on her
experience *coincides* with, and is not independent of, her
experiential perspective on the world. There is no way of specifying a
mechanism of introspection such that there could be a way in which it
goes wrong, not because the faculty of introspection is a
"super-mechanism", but rather because there is no mechanism
of introspection.




According to Martin, if we think of introspective awareness of
experience in the wrong way, the negative epistemic condition (that of
being introspectively indiscriminible from a veridical perception) is
read only as a condition on one's cognitive awareness, and not
as a condition on experience itself. And Martin thinks that this lies
behind many of the objections to his account. In response, Martin
tries to argue that read in the right way introspective
indiscriminability guarantees that phenomenal consciousness is
present. For according to Martin, the disjunctivist should stress the
connection between phenomenal consciousness and having a point of
view, or perspective on the world, a connection central to
Nagel's (1974) discussion of consciousness. So the negative
epistemological condition when correctly interpreted will specify not
just a subject's cognitive response to their circumstances, but
rather their perspective on the world (which the introspective
perspective coincides with), and this will be sufficient for there to
be something it is like for them to be so. It is worth noting that the
reasons that Martin gives for recommending this account of
hallucination appear to apply just in the case of a causally matching
hallucination (i.e. a hallucination that is subjectively
indistinguishable from a veridical perception and which involves the
same kind of proximate cause and brain state as that involved in the
corresponding veridical perception). Moreover, it is not obvious that
a disjunctivist needs to give the same account of all
hallucinations. So if a disjunctivist were to agree to Martin's
reasoning about causally matching hallucinations, it may be open to
her to provide a positive account of other hallucinations.




Fish (2008 and 2009) proposes a rather different disjunctivist account
of hallucination, which applies to all hallucinations, including
causally matching hallucinations. Fish offers what he calls a minimal,
but *positive*, story about hallucination. According to Fish, a
mental state that may be intrinsically quite different from a veridical
perception might come to be mistaken for a veridical perception and
*therein* acquire the status of hallucination. Fish thinks that
the demand for a more substantial intrinsic characterisation of
hallucination is misguided, but that the following positive story can
be told. The indistinguishability of hallucination from veridical
perception is grounded in the similarity of their effects. A
hallucination of an *x* is a mental state that, whilst not
being a veridical perception of an *x*, nevertheless comes to
have effects that are sufficiently similar to those a veridical
perception would have had. If the subject is conceptually
sophisticated these effects will include higher-order beliefs about
seeing an *x*, or seeming to see an *x*. If the subject
is not sophisticated enough to have such beliefs at all, the effects
will be solely behavioural.




This account allows that hallucinations may have no phenomenal
character, and even in those cases in which the mental state does have
phenomenal character, the phenomenal character it has may well not
account for the particular content of the hallucination. (For the
suggestion that the disjunctivist should accept this consequence, see
Sturgeon 2006 and 2008. For criticism of Fish's account, see
Siegel 2008).


### 5.2 Illusion




Different disjunctivists group together perceptions, illusions and
hallucinations in different ways when offering their disjunctive
characterisations of perceptual experience. At points it looks as
though Hinton is suggesting that illusions can be grouped together
with veridical perceptions. For in certain places he says that his
Perception-Illusion disjunctions permit a description of what is seen
in terms of how the thing looks, thereby allowing the following kind
of Perception-Illusion disjunction: '*S* sees something
which *looks* blue or is having that illusion' (1973,
61). In other places he says things that suggest that the illusion of
an object appearing blue should not be grouped together with veridical
perception, for he says that an experience as of blue is equivalent to
the mere disjunction 'Either I actually see an optical object
that is blue in colour, or I am in some situation... that is to
me like that one' (1967b, 12). Snowdon groups together
perceptions and illusions in his disjunctive characterisation of
experience: 'Either (there is something which looks to
*S* to be *F*) or (it is to *S* as if there is
something which looks to *S* to be *F*)'. In
contrast, McDowell, in his appeal to the idea of *facts* being
made perceptually manifest, appears to group together illusions and
hallucinations: an appearance that such-and-such is the case can be
'either a mere appearance or the fact that such-and-such is the
case making itself perceptually manifest to someone'.




The differences in the ways these philosophers formulate their
particular disjunctive characterisations may in part reflect their
different particular interests in appealing to a disjunctive account of
experience. For example, Snowdon's primary concern is to block an
argument about what is required for the perception of *objects*
(see section 6.1), whereas McDowell is concerned to defend an account
of experience that safeguards the distinctive epistemological role of
genuine perception in providing us with *propositional*
knowledge. It is not clear that McDowell needs to deny that there are a
number of facts made perceptually manifest to you when you suffer an
illusion, in which case he might allow that it is possible to group
together veridical perceptions and illusions as cases in which certain
facts are made manifest to their subject.




Similar considerations may apply in the case of experiences that we
might describe as *partial* hallucinations--cases in
which a subject hallucinates an object while veridically perceiving
other aspects of her environment. For example a subject might
veridically perceive a table in front of her while hallucinating a pink
rat on top of it. One question that can be asked of McDowell's
disjunctivism is whether, according to it, we should treat such cases
as ones in which the fact that there is a table in front of the subject
is made perceptually manifest to her, despite the fact that she is
hallucinating a pink rat.




Martin (2004) offers a sketch of how a naive realist might
develop an account of partial hallucination. He suggests that rather
than focusing on experiences *per se*, we can focus on
the various *aspects* of an experience--"the
different entities that one can experience and the ways in which they
can appear to one" (2004, 81). We can then explain those aspects
of a partial hallucination that are not genuinely perceptual in terms
of "that aspect of experience's indiscriminability from the
corresponding aspect of a perceptual awareness of that element"
(2004, 81). Martin also appeals to this idea in offering a suggestion
as to what the disjunctivist should say about the experience of
impossible scenes. His suggestion is that the disjunctivist should
explain such experiences not by direct appeal to the idea of veridical
perception of the impossible scene, but rather by explaining how an
experience with each of the constituent elements is indiscriminable in
that respect from a perception of that element. (For criticism of this
proposal see Siegel 2004). One concern with this proposal is whether
there may be some problem for the disjunctivist in thinking of such
experiences as having a sort of hybrid nature, given that the
disjunctivists think that perceptions and hallucinations are mental
events with such different natures. (For an argument for the claim that
accommodating certain illusions poses significant difficulties for the
disjunctivist, see Smith 2010. See also Millar 2015).




A further question to be asked in this context is whether the
disjunctivist should treat all cases of illusion as equivalent to
cases of partial hallucination. For example, if a subject perceives a
green object that looks to her to be blue, should the disjunctivist
say that the subject is perceiving the object but hallucinating the
blueness it seems to possess? Brewer (2008) offers a disjunctivist
account of certain illusions that he thinks need not be treated as
cases of partial hallucination (e.g., the Mueller-Lyer
illusion). According to Brewer, such illusions are simply cases in
which the direct object of experience has visually relevant
similarities with paradigms of a kind of which it is not in fact an
instance. The fact that the direct object of perception
looks *F*, but isn't, is explained in terms of the idea
that the object may intelligibly be taken to be *F*, when seen
from the point of view in question, in the relevant circumstances of
perception, in virtue of its relevant similarities with certain
paradigm *F*s. In the case of certain illusions, when an object
looks to be a certain way that it isn't, a disjunctivist might
place emphasis on the idea that this misleading appearance is publicly
observable; for instance, it might be the sort of thing one is able to
photograph. The disjunctivist might then say that in such cases we can
ascribe to the seen object a publicly observable feature--a
'look' or 'appearance property' that the
object has. When one sees the object one may be visually aware of this
appearance property--its having the look of an *F*. And
one's awareness of this appearance property may intelligibly
mislead one into mistakenly judging the object to be *F*. (For
related proposals about perceptual illusions, but which differ from
Brewer's account in important respects, see Antony 2011 and
Genone 2014. For defence of the claim that empirically grounded models
of illusion may be congenial to naive realism, see Phillips
2016.) 


## 6. Disjunctivism and the Causal Theory of Perception




Some philosophers associated with the disjunctive theory of perception
are simply concerned to argue that certain common element claims lack
adequate justification, thereby leaving us free to resist arguments
about perception that depend upon such claims in their premises. For
example, Paul Snowdon, one of the philosophers most associated with
disjunctivism, appeals to the possibility of a disjunctive approach to
perceptual experience in order to undermine an argument for a thesis
about our concept of perception. According to the thesis that Snowdon
aims to challenge it is a conceptual requirement that, necessarily, if
*S* (a subject) sees *O* (an object) then *O* is
causally responsible for an experience undergone by (or had by)
*S*. This thesis has been labelled the Causal Theory of
Perception (henceforth it will be referred to as the CTP).




H.P. Grice (1961) originally propounded the main argument for the
CTP. (Other advocates of the theory include Pears (1976) and Strawson
(1974)). Grice's argument takes the following general form. We
are asked to consider cases in which a subject is having an experience
appropriate for seeing an object of a certain kind--e.g., the
subject is having an experience such that it seems to her as if there
is a clock in front of her. There is in fact a clock in front of the
subject, however, the subject fails to see the clock, for the
subject's experience is a hallucination--perhaps induced
by a neuroscientist stimulating her visual cortex. It is argued that
such cases are indeed conceivable, and that in such cases the best
explanation of the subject's failure to see the object before her
is the absence of an appropriate causal connection between the object
and her experience. Hence the CTP is justified.


 According to Snowdon (1980, 1990, 1998, 2011), the plausibility of
this argument rests on a conception of perceptual experience that is
wedded to a common element assumption--in particular, the
assumption that the kind of experience one has when one genuinely
perceives the world is one whose intrinsic nature is independent of
the kinds of objects perceived. On this conception of experience,
experiences are amongst the events, the intrinsic natures of which are
independent of anything outside the subject. According to this view,
the 'looks' sentences that are true in cases of
hallucination and in genuine perception are made true by (or are true
in virtue of) exactly the same kind of occurrence in both cases. Once
this conception of perceptual experience is in play, we might then ask
after the extra-mental conditions required for seeing objects in our
environment. The Gricean thought experiments suggest that simply
having an experience that matches your surrounding environment will
not, in itself, be sufficient for seeing objects in your
environment. So the temptation then is to think that an appropriate
causal connection between your experience and those objects is
necessary for you to see them. The motivation for the CTP is therefore
undermined, according to Snowdon, unless it can be shown that it is
part of our concept of perception that the common element claim
assumed in the argument is correct.




Following Hinton's lead, Snowdon argues that from the fact
that 'looks' sentences are true in cases of hallucination and in
veridical perception, and are not ambiguous, it does not follow that
they are made true by (or are true in virtue of) exactly the same kind
of occurrence in both cases, for they may instead have disjunctive
fulfilment conditions. According to the disjunctive theory Snowdon
considers, the claim that 'It looks to *S* as of there is an
*F*' should be treated as being true in virtue of two
distinct sorts of states of affairs: *Either* (there is
something which looks to *S* to be *F*) *or* (it
is to *S* as if there is something which looks to *S* to
be *F*). This disjunctive theory allows that the two cases
(perception and hallucination), which are described in the same way,
might be of a quite different nature. In particular, it allows that the
kind of experience a subject has when she genuinely perceives the
world is such that its intrinsic nature is not independent of the
kinds of objects perceived. For Snowdon, the availability of this
disjunctive approach to perceptual experience undermines the argument
for the CTP, unless proponents of the argument can say something which
is legitimately conceptual and which shows that this disjunctive
approach must be wrong. (So note that according to Snowdon, an
assertion of the disjunctive theory is not actually needed for a
rejection of the Gricean argument for the CTP.)




For defence of the causalist approach against disjunctivism, see Lowe
2008. For a defence of the claim that disjunctivism is compatible with
the CTP, see Child 1992, 1994 and 2011.


## 7. Conclusion




As we have seen, there are a variety of different disjunctivist views,
often motivated by quite different concerns, and the disagreements
that these disjunctivists have with their opponents are relevant to a
number of debates in the philosophy of perception and
epistemology--debates about the metaphysics and phenomenology of
perceptual experience, our concept of perception, the epistemological
role of perceptual experience, and self-knowledge. Many of the
disjunctivist views and arguments that have been outlined here have
been proposed relatively recently, and the debates they have inspired
seem set to continue. In a further recent development disjunctive
theories of perception have inspired similar disjunctive approaches in
the philosophy of action--concerning both the ontology of action
and a subject's reasons for performing actions. (For discussion of
disjunctive approaches to action see Haddock and McPherson 2008b,
Ruben 2008, Hornsby 2008 and Dancy 2008.)