mental states involved in a "good case" experience of veridical
perception and a "bad case" experience of hallucination differ, even
in those cases in which the two experiences are indistinguishable for
their subject. Consider the veridical perception of a bar stool and an
indistinguishable hallucination; both of these experiences might be
classed together as experiences (as) of a bar stool or experiences of
seeming to see a bar stool. This might lead us to think that the
experiences we undergo in the two cases must be of the same kind, the
difference being that the former, but not the latter, is connected to
the world in the right kind of way. Such a conjecture has been called
a "highest common factor" or "common kind" assumption. At heart,
disjunctivism consists in the rejection of this assumption. According
the disjunctivist, veridical experiences and hallucinations do not
share a common component. There are a host of interesting questions
surrounding disjunctivism including: What is involved in the claims
that good case and bad case experiences differ? Why might one might
want to be a disjunctivist? What kinds of claims can the disjunctivist
make about hallucination and illusion? These questions, and problems
for the thesis, will be discussed as we proceed.
1. Introduction
If disjunctivism consists in the rejection of the claim that veridical
perceptions and hallucinations share a common factor, why
"disjunctivism"? The thesis acquires its name from the particular way
in which it reinterprets statements that, at face value, might appear
to commit us to the existence of experiences, understood as good
case/bad case common factors. Consider the sentence, 'I seem to see a
flash of light'. Such a sentence could be true regardless of whether
we are perceiving or hallucinating. As such, the truthmaker of such a
sentence might seem to be something common to the two cases, and a
commitment to the truth of such sentences in turn to commit us to a
common factor. However, J.M. Hinton contends that 'I seem to see a
flash of light' is simply "a more compact way of saying" something
like this: "Either I see a flash of light, or I have an illusion of a
flash of light" (1967: 217).
It is this reinterpretation of seems-sentences as disjunctive in form
that gives disjunctivism its name. Moreover, not only do
disjunctivists insist that a seems-statement is shorthand for a
disjunctive statement, they insist that such statements have a
disjunctive truthmaker. The statement, Either I see an F or it merely
seems to me as if that were so, can be made true in two different
ways: either by its being true that I actually do see an F, or by its
being true that I don't see an F but that it is for me as if I did. To
see how this is supposed to work, consider the following example from
Don Locke:
"This is a woman, or a man dressed as a woman" does not assert the
presence of a woman/transvestite-neutral entity … its truth depends
simply on the presence of either a woman or a transvestite, as the
case may be. (1975: 467)
In this way, Hinton shows how we can be committed to the existence of
true seems-statements without being committed to a common factor that
makes them true.
In reinterpreting seems-statements in this way, Hinton opens the door
for philosophers to claim that veridical perception and hallucination
might be psychologically different kinds of experience, which
nonetheless both make it the case that it seems to the subject to be a
certain way. The core disjunctive claim is therefore that "we should
understand statements about how things appear to a perceiver to be
equivalent to a disjunction that either one is perceiving such and
such or one is suffering a … hallucination; and that such statements
are not to be viewed as introducing a report of a distinctive mental
event or state common to these various disjoint situations. (Martin
2004: 37).
2. Disjunctivism and Naïve Realism
In insisting that veridical perceptions and hallucinations are mental
states of different kinds, the disjunctivist takes on the explanatory
burden of giving an account of how two experiences could be
indistinguishable without being experiences of the same kind. Given
this, what might lead someone to endorse disjunctivism? We shall
consider specific arguments for disjunctivism in section 4, but for
present purposes it will suffice to note that the typical motivation
has been to make room for a "naïve realist" theory of veridical
experience. The naïve realist claims that, in the good cases, external
objects and their properties "partly constitute one's conscious
experience" (Martin 1997: 83) and thereby "shape the contours of the
subject's conscious experience" (Martin 2004: 64). So naïve realism
entails disjunctivism: if naïve realism is true, then the kind of
mental state that is involved in a veridical perception – a mental
state that relates the subject to elements of the mind-independent
environment – could not be involved in a hallucinatory situation. The
hallucinatory state must therefore be of a different kind. A defence
of naïve realism therefore requires a defence of disjunctivism.
As there is such an intimate connection between disjunctivism and
naïve realism, some theorists have actually incorporated naïve realism
about the good cases into the very definition of disjunctivism. Paul
Snowdon, one of the names most closely associated with the theory,
takes disjunctivism to involve the claim that: "the experience in a
genuinely perceptual case has a different nature to the experience
involved in a non-perceptual case. It is not exhausted, however, by
the simple denial of a common nature, but involves also the
characterisation of the difference between the perceptual and
non-perceptual in terms of the different constituents of the
experiences involved. The experience in the perceptual case in its
nature reaches out to and involves the perceived external object, not
so the experience in other cases." (2005: 136-7; for a similar
formulation, see Sturgeon 2006: 187). However, despite the fact that
naïve realism entails the denial of the common kind thesis, the denial
of the common kind thesis does not entail naïve realism. For this
reason, I think it makes taxonomic sense to restrict the label
"disjunctivist" to theories that deny that there is a common factor to
indistinguishable cases of veridical perception and hallucination. Yet
of course, as naïve realism entails disjunctivism, an argument for
naïve realism is thereby also an argument for disjunctivism. We will
come back to this when considering motivations for disjunctivism in
section 4. Before we do this, however, we need to take a moment to
look closely at the claim that veridical perception and hallucination
share a common component.
3. Types of Disjunctivism
The reason for caution is that, if we read this claim as holding that
veridical perception and hallucination have nothing in common
whatsoever, then it is surely false. As we have already seen, a
veridical perception of an F and a hallucination of an F have at least
this in common: they are both visual experiences of an F / cases of
seeming to see an F. So the "no common factor" claim must be read as
allowing that they have something in common. This, however, raises an
important question. In what respects can the mental states involved in
veridical perception and hallucination be the same and the theory
remain a version of disjunctivism? This opens up the possibility of
different types of disjunctivism.
For example, Byrne and Logue formulate a version of disjunctivism they
call epistemological disjunctivism, which is disjunctivist about
perceptual evidence (2008: 66). That is, the epistemological
disjunctivist denies that one's perceptual evidence is the same across
indistinguishable cases of veridical perception and hallucination. As
Snowdon puts it, "we can divide cases where it is true that it appears
to the subject as if P into two sorts; one is where the subject is in
a position to know that P, in that the fact that P is manifested to
him, and others where the subject is in a position to know merely that
it appears to be P" (2005: 140). On both Byrne and Logue's
presentation and Snowdon's, epistemological disjunctivism is
consistent with the two experiences having substantial commonalities.
As Snowdon asks, "why cannot a single basic sort of (inner) experience
have quite different epistemological significance in different cases,
depending, say, on the context and on facts about causation?" (ibid.)
Epistemological disjunctivism, then, leaves room for veridical
perception and hallucination to be of the same metaphysical kind, so
long as they do not have the same epistemological status. More robust
versions of disjunctivism will go on to reject the claim that
veridical perception and hallucination are of the same metaphysical
kind. For example, we might define "metaphysical disjunctivism" as the
claim that veridical perceptions and hallucinations are different
kinds of mental states in as much as they have different constituents,
or different supervenience bases. Yet as Byrne and Logue point out,
even this seems to be compatible with the two mental states having
something in common. Thus they introduce the "moderate view" (2008:
71), which accepts that the good cases and bad cases "are different in
significant mental respects, despite having a common mental element,"
where this common mental element is in the picture to ground the
phenomenal similarity of the two states. A yet more robust version of
disjunctivism, then, holds that, despite cases of veridical perception
and hallucination both being cases in which it seems to the subject as
if P, they nonetheless do not have even phenomenal character in
common.
In an attempt to impose some order, Martin characterizes disjunctivism
as committed to the claim that the "most fundamental kind that the
perceptual event is of, the kind in virtue of which the event has the
nature that it does, is one which couldn't be instanced in the case of
hallucination." (2004: 60). They key notion here is that of a
"fundamental kind" – the kind in virtue of which the event has the
nature it does. How do we determine the fundamental kind a particular
mental state or event belongs to? By determining the "most specific
answer to the question, 'What is it?'" (2006: 361). So, for example,
take our veridical experience of a bar stool. If the common kind
theory were correct, then the "best candidate for the fundamental or
essential kind" of both a veridical perception of a bar stool and a
hallucination of a bar stool would be that they are both instances of
the kind: experience (as) of a bar stool. Disjunctivism, however,
allows that the "best candidate for the fundamental or essential kind"
of a veridical perception of a bar stool is that it is an instance of
the kind: veridical perception of a bar stool. Hallucinations, of
course, do not belong to this kind (2004: 72). We will discuss the
kinds that hallucinations do belong to in section 6.2.
So we have a number of different varieties of disjunctivism available;
varieties that differ in the degree of similarities that the mental
states involved in veridical perception and hallucination are allowed
to share. However, as we shall see in the next section, not every type
of disjunctivism just discussed will successfully legitimate the
various motivations that have been cited as reasons for endorsing
disjunctivism.
4. Arguments for Disjunctivism
Before we move onto reasons to think that disjunctivism is true, it is
worth noting that its first outing post-Hinton was in fact as a
component of an argument, due to Paul Snowdon, against the Causal
Theory of Perception. But this argument does not require the truth of
disjunctivism, merely its conceptual coherence, for which reason I
mention it only briefly. The causal theory claims that "it is a
conceptual requirement that, necessarily, if P (a subject) sees O (an
object) then O is causally responsible for an experience (call it E)
undergone by (or had by) P" where "experiences are amongst the events,
the intrinsic natures of which are independent of anything outside the
subject" (Snowdon 1990: 123). So the causal theory is committed, not
only to a common factor conception of experiences, but also to the
claim that this is a conceptual truth – something "immediately
acknowledgeable by any person, whatever their education, who can count
as having the concept in question" (1980: 176). Essentially, Snowdon's
argument consists in arguing that, even if disjunctivism turns out to
be false, it will only be "scientifically established facts about
perceptual and hallucinatory processes" that disprove it (1990: 130).
But these are results that the man on the street could not be expected
to know merely in virtue of having the concept of perception. So even
if it is false, disjunctivism is not a conceptual falsehood and
therefore the second claim of the causal theory – that the intrinsic
nature of the experience a subject has when perceiving an object is
independent of anything outside the subject – is not a conceptual
truth as the causal theorist requires.
a. Epistemological Motivations
As Snowdon's argument does not require the truth of disjunctivism, we
still have been given no arguments for the thesis. One salient
motivation has to do with epistemology. Consider a sceptical argument
that runs as follows. When we hallucinate, the kind of experience we
have clearly fails to put us in a position to know anything about the
external world. The experience we have in the case of a veridical
perception indistinguishable from this hallucination is an experience
of the same kind. As the bad case experience fails to put us in a
position to acquire knowledge, having the same kind of experience in
the good case cannot place us in a better epistemic position. So even
when we have veridical experiences, we are not in a position to know
anything about the external world.
Disjunctivism offers to block this argument by denying the premise
that the experience we have when we veridically perceive is the same
as the experience we have when we hallucinate. This would not, of
course, prove that we do know anything about the external world,
merely that such knowledge is not impossible. Yet this would block the
sceptic from using the impossibility of knowledge as a premise in an
argument for this conclusion. In response, the disjunctivist's
opponent may point out that, given the acknowledged
indistinguishability of veridical perception and hallucination, we
cannot know, on any given occasion, whether we are hallucinating or
perceiving veridically. So it is not after all clear that
disjunctivism does provide any epistemic advantages. The disjunctivist
might then reply that this misses the point. It is not that
disjunctivism offers an argument to prove that we do have knowledge,
rather it offers a rebuttal to an argument that we cannot. To
illustrate this, consider the familiar sceptical claim that all of our
experiences might have been just as they are even if we were in the
clutches of Descartes' demon. If the disjunctivist is correct, this is
no longer possible – if any of my experiences are in fact veridical,
then they could not have been as they are misleading. Suppose, then,
that the sceptic were to reformulate the sceptical hypothesis as
follows: all of your experiences might have been of the misleading
kind. Now we can ask, so what? As long as they are not misleading,
then many of our empirical beliefs will be justified. As McDowell puts
it, this leaves the door open for us to hold that "our knowledge that
[the sceptical] possibilities do not obtain is sustained by the fact
that we know a great deal about our environment" (2008: 379).
An interesting question about the epistemological motivation for
disjunctivism is that of which variety of disjunctivism it requires.
In one sense, it clearly requires epistemological disjunctivism,
according to which good cases and bad cases differ in epistemological
significance. Yet having said this, we might also wonder to what
extent two experiences that are the same in significant respects might
be plausibly held to provide different levels of perceptual evidence.
Could two experiences with the same constituents and phenomenal
character be claimed to be significantly epistemologically different?
If not, what about experiences that are metaphysically different but
phenomenally similar? Or does the claim of significant epistemological
difference require the most robust version of disjunctivism:
phenomenal disjunctivism? The answers given to these questions will in
turn depend on one's position on other questions in epistemology, such
as the nature of justification. For example, an externalist about
justification can easily allow that two experiences that are
metaphysically similar can differ in epistemological significance, yet
one inclined to internalism about justification may need to go all the
way to a phenomenal disjunctivism. How compelling we find the
epistemological motivation will therefore depend on a range of other
issues.
b. Modesty
Another argument that has been used to support disjunctivism is that,
unlike common factor theories, it is not required to "attribute to
responsible subjects potential infallibility about the course of their
experiences" (2004: 51). This argument turns on what is required for a
particular experiential occurrence to count as a "visual experience",
where this category includes veridical perceptions and hallucinations.
Martin begins by asking us to consider a veridical perception of a bar
stool and a perfectly indiscriminable hallucination of such. Now ask,
in virtue of what do these both count as experiences of a bar stool?
According to the common factor theorist, veridical perceptions are
experiences with certain positive characteristics that are both
necessary and sufficient for that perception to qualify as an
experience of a bar stool. Then, "when I come to recognize the
possibility of perfect hallucination just like my current perception,
what I do is both recognize the presence of these characteristics … in
virtue of which this event is such an experience, and also recognize
that an event's possessing these characteristics is independent of
whether the event is a perception or not." (2004: 47). According to
Martin's kind of disjunctivist, however, nothing more needs to be
said; something is an experience of a bar stool just in case it is
indiscriminable from a veridical perception of a bar stool.
With these two explanations in hand, Martin then points out that as of
yet, "nothing rules out as possible a situation in which [these
positive characteristics] are absent but in which a subject would be
unable to discriminate through reflection this situation from one in
which a [bar stool] was really being seen." (2004: 49). Now the
disjunctivist's conception of what is required for an event to qualify
as visual experience would allow us to count such an event as an
experience (as) of a bar stool simply in virtue of the fact that it is
indiscriminable from a veridical perception of a bar stool. The
alternative conception, however, could not count this as a visual
experience. In order to rule out the possibility of such cases, Martin
therefore suggests that the disjunctivist's opponent will have to
assume that a careful subject simply cannot fail to recognize the
presence of positive characteristics when they are present, or the
absence of such characteristics when they are absent. Thus unlike the
disjunctivist, the common factor theorist has to immodestly attribute
to subjects substantive epistemic powers. Disjunctivism is therefore a
more modest and hence preferable theory.
c. Naïve Realism: Phenomenology
Another set of motivations for disjunctivism turn on the fact, noted
in section 2 above, that naïve realism requires disjunctivism, and
that naïve realism is the view of the 'common man' or, as Martin puts
it, that it "best articulates how sensory experience seems to us to be
just through reflection" (2006: 354). Yet as Hawthorne and Kovakovich
point out, if it is true that the common man does indeed have a view
of visual experience, which in itself is not obvious, it is unlikely
to be specific enough to decide between philosophical theories of
perception. For example, whatever force this motivation carries turns
on the idea that the common man would endorse the naïve realist's
theory of the good cases. But it is entirely possible that the common
man would also have views about, say, the nature of hallucination or
the relationship between consciousness and the brain that are
inconsistent with this view. If this were to be the case, then the
appeal to the common man may well be indecisive. Finally, Hawthorne
and Kovakovich argue that there would not be "much point in pursuing
the philosophy of perception in a setting where it is assumed that
[common sense] commitments will survive philosophical and scientific
reflection. After all, we shouldn't think that vulgar common sense has
seen in advance how to handle various challenges to its commitments"
(2006: 180)
Despite these difficulties, Benj Hellie has recently offered a
phenomenological argument in favour of naïve realism. This argument
turns on the premise that, "a judgment about an experience to the fact
that it is F based on phenomenological study [by experts, under ideal
circumstances] will be accurate" (2007a: 267). He then lists a number
of judgments from such experts on phenomenological study, which he
claims embody judgments that veridical visual experience is naïve
realist in character. To give a flavour of these quotes, consider
Levine's claim that the "ripe tomato seems immediately present to me
in experience […] The world is just there" (2006: 179) and Campbell's
claim that "the phenomenal character of your experience … is
constituted by the layout of the room itself" (2002: 116).
An alternative phenomenological motivation is also developed by
Martin. This motivation is distinctive, however, in that it turns on
the phenomenology of sensory visual imagination rather than that of
visual perception per se (2002: 402-19). In brief, Martin argues first
for the Dependency Thesis – that imagining X = imagining experiencing
X – and then for the claim that to imagine experiencing is to imagine
how things would be immediately presented to us in such an experience.
He then argues that the naïve realist can give a much better account
of this imagined immediacy than can a representationalist because,
according to naïve realism, the immediacy of a visual experience of X
is explained by X's being presented to the subject. So in imagining an
experience of X, one thereby imagines X being presented to the subject
and immediacy follows. The representationalist's account of visual
immediacy, on the other hand, turns on the fact that the attitude the
subject bears to the relevant content is stative – i.e. committal to
the truth of the content – whereas, in imagination, one does not bear
a stative attitude to the imagined content. One "is not thereby in a
state whose attitudinative aspect would give rise to the phenomenon of
immediacy" (2002: 415). According to Martin, naïve realism therefore
gives the correct account of the phenomenology of sensory visual
imagination.
d. Naïve Realism: Demonstrative Reference
John Campbell (2002) has argued that a naïve realist conception of
experience is a requirement for the very possibility of having
thoughts about mind-independent objects at all. Campbell's contention
is that, if you are to know what my use of a demonstrative expression
refers to, you have to be able to consciously single out the relevant
object, an ability that requires a naïve realist conception of
conscious visual experience. To illustrate this, Campbell uses an
example of a party where you ask me questions about 'that woman'. Even
if it turns out that I can make reliable guesses about what the woman
is wearing, drinking, and so on, Campbell suggests that if I cannot
consciously pick out the woman you are talking about, then I do not
know to whom you are referring (2002: 8-9). He concludes that
conscious (visual) attention is therefore ordinarily required for us
to have knowledge of the reference of demonstratives. This therefore
places a condition on an adequate account of visual experience – it
must explain how it can be the source of this kind of knowledge.
Campbell then asks: what would experience have to be like for it to
play the role of grounding our knowledge of the reference of a
demonstrative? He then argues that, to know the reference of a
demonstrative, we must interpret the demonstrative as "referring to a
categorical object, not merely a collection of potentialities" (2002:
145). To see why, suppose I do have the ability to reliably guess what
the woman you are talking about is eating, drinking and wearing. If
all there was to knowing the reference of a demonstrative was to be
aware of the various potentialities that the object has, I would
therefore know the reference of your use of 'that woman'. Yet as we
saw, I do not know the reference of your demonstrative. What is
missing, Campbell suggests, is experience of why these potentialities
exist – experience of the categorical object that grounds these
potentialities. So if experience is to explain our knowledge of
demonstrative reference, then an adequate analysis of experience must
account for the fact that experience is experience of the categorical.
This is just the kind of account that is offered by naïve realism.
5. Objections to Disjunctivism
As we have seen, as the truth of naïve realism entails the truth of
disjunctivism, then arguments for naïve realism are thereby arguments
for disjunctivism. And indeed, the majority of arguments for
disjunctivism appear therefore to require the most robust phenomenal
version of the thesis. Yet as the entailment does not go in the other
direction, an objection to naïve realism is not, thereby, an objection
to disjunctivism. In this section, I will therefore only focus on
objections to disjunctivism itself. For objections to naïve realism –
objections, the success of which may remove some or all of the
motivations for being a disjunctivist.
a. The Causal Argument
As an argument against disjunctivism, the causal argument starts from
the obvious truth that, in order for perceiving to take place, there
must be chains of causation from the perceived object to the subject's
sense organs, and then to the subject's brain. A simple version of the
causal argument proceeds as follows. At the end of this causal chain
is an experience. Suppose then that the intermediate stages of the
causal chain were activated in a nonstandard manner – say, by direct
stimulation of the brain. So long as the later stages of the causal
chain were as they would have been in the good case, the same kind of
experience will result. But this is just to say that the same kind of
experience can be caused in both good cases and bad cases, contra
disjunctivism.
As expressed here, this argument turns on a principle we might call
the "same immediate cause – same effect" principle. It asserts that,
so long as the neural stage in the causal chain prior to the
experience is the same then, no matter whether that prior stage was
produced by external objects or internal misfirings, the effect – the
experience – will be the same in both cases. The issue then becomes
one of whether or not we should accept this principle. And there are
reasons to think that we should not. To adapt an example from Dretske,
if forgers managed to reproduce the machine that prints legitimate
banknotes, the banknotes the forgers print on it will still be
counterfeit, even though the immediate "cause" of these banknotes is
the same as the immediate "cause" of genuine currency. Or, to take a
more philosophical example, considerations familiar from the work of
Putnam (1975) suggests that what makes my thoughts about water is not
a feature of their immediate causes, but their distal causes. So there
are reasons why we might dispute the "same immediate cause – same
effect" principle when the effects in question are taken to be
experiences.
For this reason, some opponents of disjunctivism have resorted to a
weaker version of the principle. A.D. Smith, for example, insists that
"it is surely not open to serious question that [the same immediate
cause – same effect principle] does apply with respect to the merely
sensory character of conscious states" (2002: 203). Here is a nice
passage in which this contention is laid out in detail.
Distal environmental causes generate experiential effects only by
generating more immediate links in the causal chains between
themselves and experience, namely, physical stimulations in the body's
sensory receptors … These states and processes causally generate
experiential effects only by generating still more immediate links in
the causal chains between themselves and experience – namely, afferent
neural impulses, resulting from transduction at the sites of the
sensory receptors on the body. Your mental intercourse with the world
is mediated by sensory and motor transducers at the periphery of your
central nervous system. Your conscious experience would be
phenomenally just the same even if the transducer-external causes and
effects of your brain's afferent and efferent neural activity were
radically different from what they are" (Horgan and Tienson 2002:
526-7).
The contention here is that, even if there are reasons to think that
changes in a subject's environment would affect the overall nature of
the mental state that results from the same type of neural stimulation
(perhaps because it could make a "seeing of water" experience into a
"seeing of twater" experience), the "conscious [aspects of the]
experience would be phenomenally just the same". This result, of
course, would suffice to refute the phenomenal version of
disjunctivism, if not the thesis in its metaphysical and
epistemological forms. Again, though, for this argument to succeed,
the weaker principle – that "same immediate cause – same effect" is
true for the phenomenal aspects of mental states – must be found to be
acceptable. One consideration that has been cited in its favour is
that it provides an explanation of how indiscriminable hallucinations
are possible at all: "if it were not the case that perceptual
processes, however stimulated, were sufficient to generate experience,
it would be a mystery why [veridical-seeming] hallucinations should
occur" (Robinson 1994: 152). However the legitimacy of this motivation
can be challenged.
b. The "Screening Off" Objection
Even if the causal argument in this form is rejected, the
disjunctivist is still not out of the woods. Suppose the kind of
neural replication appealed to by the causal argument is at least
possible in principle. And suppose, too, that the mental upshot of
such neural replication would be an indistinguishable hallucination.
Most theorists, I think, would accept these two plausible claims. Yet
if they are accepted, the disjunctivist is still in difficulty, even
though we haven't yet mentioned the phenomenal character of the
experiences. The problem is this. If an indiscriminable hallucination
is produced by neural replication, then we might think that there must
be an explanation of this indiscriminability: that the hallucinatory
experience must have a property – call it property I – that explains
why the hallucination is mistaken for a veridical experience. But in
these neural replication situations – Martin calls them "causally
matching" hallucinations (2004: 60) – it must be that the neural
activity alone suffices for the experience to have property I. Now, if
the same neural activity takes place in a case of veridical
perception, then it would also suffice for the veridical experience to
have property I. But then the disjunctivist's opponent can argue as
follows.
We have already accepted that property I – whatever this property may
be – accounts for the fact that the hallucinatory experience seems, to
its subject, just like a veridical perception. Now for the reasons
just given, veridical experiences also have property I, together with
whatever special phenomenal character they have by virtue of being
veridical. But so long as I suffices to explain why the hallucination
is taken to be a veridical experience, then I also ought to suffice to
explain why the veridical perception is taken to be a veridical
experience. Property I would therefore seem to "screen off" whatever
additional characteristics the veridical experience may have from
having any explanatory import. The disjunctivist needs to be aware of
this threat in developing theories of hallucination as we shall see.
c. Matching Hallucinations to Perceptions
This objection takes, as a starting point, the idea that for any
possible veridical perception, there is a hallucination that 'matches'
or 'corresponds' to that veridical perception – the hallucination that
would, from the subject's point of view, seem just like that veridical
perception. The challenge for the disjunctivist is to give an account
of what this correspondence amounts to. Farkas puts the challenge this
way:
take a particular veridical perception (VP) of a teacup in front
of me, and the corresponding hallucination (H). H is not a perception
of the teacup – but this is true of many other events as well. What
else do we have to say about H to make sure that it is the
hallucination corresponding to the VP in question? (2006: 205-6).
One plausible answer to this question, suggests Farkas, is that both
good cases and bad cases have to "involve the same phenomenal
properties" (2006: 207). Yet as she points out, this answer has "a
metaphysical character," indeed one that commits us to the existence
of something that the two cases have in common. This is, therefore, an
answer that the phenomenal disjunctivist, at least, cannot endorse.
Farkas then goes on to canvas a number of non-metaphysical answers to
this question and argues that they all fail to provide a plausible
response. The conclusion drawn is that the only way we can provide an
adequate account of what it is for a hallucination to correspond to a
veridical perception of a particular kind is to accept, contra
phenomenal disjunctivism at least, that the two states have something
metaphysical in common.
6. Theories of Hallucination
Thus far we have seen that the disjunctivist has a negative claim to
make about hallucination: that it is not an experience of the same
kind as a veridical perception. But what else can the disjunctivist
say about hallucination?
a. Positive Disjunctivism
The positive disjunctivist insists that there is a positive story to
tell about the nature of the hallucinatory state. For example, one
might insist that hallucination involves the awareness of something
other than external objects – some object proxy, if you will. Michael
Thau (2004: 195) suggests that this is the form of disjunctivism
advocated by John McDowell. In presenting his disjunctive position,
McDowell suggests 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" (1982: 472).
Immediately following this presentation, McDowell goes on to say that
"mere appearances" are the objects of deceptive experiences. So
McDowell's complete picture looks to be one on which we have one kind
of experiential relation to two different kinds of objects: "facts
made manifest" in the perceptual case, and "mere appearances" in the
hallucinatory ones.
A related view is presented by Mark Johnston (2004), although it is
unclear whether or not it really qualifies as a variant of
disjunctivism. Johnston contends that, when we have a veridical visual
experience, we are aware of an instantiated sensible profile: "a
complex, partly qualitative and partly relational property, which
exhausts the way the particular scene before your eyes is" (2004:
134). Importantly, the sensible profile that we are aware of, says
Johnston, is a type not a token; had we stood before an array of
different particulars instantiating the same sensible profile, what we
are aware of – the sensible profile – would have been the same. Then,
when you have a hallucination that is indiscriminable from this
experience, "you are simply aware of the partly qualitative, partly
relational profile. … When the visual system misfires, as in
hallucination, it presents uninstantiated complexes of sensible
qualities and relations" (2004: 135).
On Johnston's view, there are, then, clear similarities between good
cases and bad cases – in particular, in both cases the subject is
aware of the same sensible profile. Yet there are important
differences too. "When we see," says Johnston, "we are aware of
instantiations of sensible profiles. When we hallucinate we are aware
merely of the structured qualitative parts of such sensible profiles.
Any case of hallucination is thus a case of "direct" visual awareness
of less than one would be "directly" aware of in the case of seeing"
(2004: 137 emphasis added). The objects of hallucination are therefore
"proper parts" of the objects of seeing (140). So Johnston's view
seems best described as a variant of the moderate view outlined in
section 3 above. The difficulty faced by positive views is that they
flirt with the screening off problem just noted. Focusing on the
McDowellian view first, suppose that a certain pattern of neural
activity suffices for one to be aware of "mere appearances" in the bad
cases. But then, what about the same neural activity that occurs in
the good case? If it is claimed that this does not suffice for
awareness of mere appearances, then we might wonder why, "if the
mechanism or brain state is a sufficient causal condition for the
production of an image, or otherwise characterised subjective
sense-content, when the [objects] are not there, why is it not so
sufficient when they are present? Does the brain state mysteriously
know how it is being produced … or does the [object], when present,
inhibit the production of an image by some sort of action at a
distance?" (Robinson 1994: 153-4). Yet if we do accept that the
pattern of neural activity also suffices for the subject to be aware
of "mere appearances" in the good cases, then as these suffice to
explain how things are from the subject's perspective in the bad
cases, they should likewise suffice in the good cases. But if this is
so, then an appeal to the subject's being aware of "facts made
manifest" in the good cases seems superfluous, at least for the
purposes of characterizing how things are from the subject's
perspective.
It is less clear how Johnston's view fares here. At a point in his
paper, he asks: "Why isn't awareness of a sensible profile a common
act of awareness as between seeing and hallucination? It may be held
to be … But it does seem that once we adopt the act/object treatment
of visual experience it is more natural to individuate an act of
awareness occurring at a time in terms of an object that includes all
that one is aware of in the relevant time" (2004: 171). Given that, as
noted above, the perceiver is aware of more than the hallucinator (in
that the perceiver is aware of the particulars that instantiate the
sensible profile whilst the hallucinator is aware of the sensible
profile alone), his suggestion seems to be that, when we account for
the perceiver's awareness of the particulars, we thereby account for
the perceiver's awareness of the sensible profile. There is then no
need to introduce an additional awareness of an (uninstantiated)
sensible profile. Yet this may not convince his opponents. The
objection remains: if neural activity suffices for awareness of an
uninstantiated sensible profile in the bad cases, it should suffice in
the good cases too, whether or not we need to appeal to this to
explain the fact that the subject is aware of a sensible profile at
all. So Johnston's view may also be threatened by the screening off
worry, even if it is in the sense that a subject's awareness of a
particular sensible profile is overdetermined.
b. Negative Disjunctivism
It is this concern – that any positive account of hallucination will
play into the hands of the screening off objection – that motivates
some disjunctivists to provide an essentially negative account of
hallucination. In answer to the question, "What else can the
disjunctivist say about hallucination?", the negative disjunctivist
says, nothing else – all that we can say about indiscriminable
hallucinations is that they are not veridical perceptions but are
indiscriminable from them. This approach is most closely associated
with the work of M.G.F. Martin.
Given the threat of the screening off worry, Martin investigates
whether there are any limitations to the general principle that common
properties screen special properties off from being causally
efficacious and concludes that there are. Consider the property of
being an unattended bag in an airport, which causes a security alert.
Sometimes objects with this property are harmless, but sometimes they
contain a bomb. Now ask: does the property common to harmless and
non-harmless objects – that of being an unattended bag in an airport –
screen off the non-common property of being a bomb in an airport from
being explanatory? Not at all. Instead, the only reason the common
property of being an unattended bag in an airport has the explanatory
role it does is because, sometimes, this property is correlated with
the special property of being a bomb in an airport. In such a case, we
can say that the explanatory potential of the common property of being
an unattended bag in airport is "inherited from" or "dependent upon"
the explanatory potential of the special property of being a bomb in
an airport. As Martin concludes, common properties with "inherited or
dependent explanatory potential offer us exceptions to the general
model of common properties screening off special ones" (2004: 70).
In the discussion of Martin's claim that disjunctivism is a more
"modest" theory of visual experience than a common factor theory
(section 4.2), we saw that Martin's kind of disjunctivist accepts that
a hallucination of a certain kind has the property of being
indiscriminable from a veridical perception. Now although such
indiscriminability properties are common to both good cases and bad
cases – a veridical perception of an F is indiscriminable from itself
– whatever explanatory potential indiscriminability properties have is
inherited from the explanatory potential of the associated veridical
experience.
Why did James shriek like that? He was in a situation
indiscriminable from the veridical perception of a spider. Given
James's fear of spiders, when confronted with one he is liable so to
react; and with no detectable difference between this situation and
such a perception, it must seem to him as if a spider is there, so he
reacts in the same way. (2004: 68).
Martin therefore suggests that, if the screening off worry is to be
avoided, the disjunctivist must characterize the hallucinatory state
purely negatively – must say that "when it comes to a mental
characterization of the hallucinatory experience, nothing more can be
said than the relational and epistemological claim that it is
indiscriminable from the perception" (2004: 72). So whilst there is a
kind which is shared by hallucination and veridical perception – the
kind: being indiscriminable from a veridical perception – only for
hallucinations is this their most fundamental kind. Where veridical
perceptions are concerned, "being a veridical perception of a tree is
a better candidate for being its fundamental or essential kind than
being indiscriminable from being such a veridical perception" (2004:
72). This is how Martin avoids the screening off objection.
Negative disjunctivism is also endorsed by Brewer (2008: 173) and Fish
(2008). Fish does say a little more on the question of what it is that
makes hallucinations indiscriminable from veridical perceptions,
however. According to Fish, for a hallucination to be indiscriminable
from a veridical perception of a certain kind is for it to generate
the same kinds of introspective beliefs that a veridical perception of
that kind would have generated. Consider again James's veridical
experience of a spider. Normally, this would lead James to believe
that he sees a spider. A hallucination qualifies as indiscriminable
from such a veridical perception if it also yields such beliefs. It is
the presence of these beliefs that then explains why hallucinating
subjects behave as they do: as a hallucination of a spider leads James
to believe that he sees a spider (by definition), so James will
therefore react in the way he would if he really did see a spider.
c. Negative Disjunctivism and Indiscriminability: Objections
Given the negative disjunctivist's characterization of the
hallucinatory state as a state that is indiscriminable from a
veridical perception of a certain kind, a lot hangs on the way in
which the key notion of indiscriminability is understood. In
discussing these issues, Martin suggests that a hallucination of an F
"is such that it is not possible to know through reflection that it is
not one of the veridical perceptions [of an F]" (2006: 364). We can
therefore define indiscriminability as follows: x is indiscriminable
from a veridical perception of an F if and only if x is such that it
is not possible to know through reflection that it is not a veridical
perception of an F. There are two key features of this definition that
have been the source of objections. First, the restriction to the
relevant knowledge being acquired 'through reflection'; second, the
question of how to interpret the modality present in 'not possible to
know'.
One way of coming to know that your experience is not a veridical
perception of an F is by testimony. However, Martin suggests that,
even if you know that your experience is not veridical in this way, it
might still qualify as indistinguishable from a veridical perception.
He therefore introduces the 'through reflection' clause in order to
rule out knowledge from testimony as a defeater for
indistinguishability (2006: 364-5). Sturgeon, however, argues that it
is far from straightforward to spell out just what information should
be disqualified by not being available 'through reflection'(2006:
208-10). On the one hand, he suggests that the 'through reflection'
restriction must be strong enough to rule out any of the routes by
which a hallucinating subject might 'figure out' that they are
hallucinating and hence must be taken to stipulate that the
"information involved in background beliefs cannot be generally
available to reflection …. Otherwise the possibility of everyday
knowledge of [hallucination] will slip through the net [and] count as
knowledge obtainable by reflection" (2006: 209).
On the other hand, he points out that when one hallucinates an F, one
is thereby in a position to know a vast array of things. As a
hallucination of an F is discriminable from veridical experiences of
Gs, Hs, and Js, Martin's definition of indiscriminability will require
that, for each case, a subject hallucinating an F can know, by
reflection alone, that his experience is not one of these veridical
experiences. But Sturgeon suggests that this "is a huge amount of
knowledge to be got solely by reflection … and not by reflection on
the visual character of [the hallucination], recall. … The only way
that could be true, I submit, is if background beliefs were generally
available to reflection on context" (2006: 210). With these two
results, Sturgeon presents Martin with a dilemma. On the one hand, to
rule out the possibility we might simply use our background beliefs to
figure out that we are hallucinating, the 'through reflection' clause
must restrain us from making use of background beliefs. Yet on the
other, to make sense of all the reflective knowledge Martin's theory
allows that we are in a position to acquire when we hallucinate, the
'through reflection' clause must allow us to make use of background
beliefs. But this, suggests Sturgeon, is just to say that Martin
cannot give an adequate account of the 'through reflection'
restriction.
Another source of objections has stemmed from Martin's interpretation
of the 'not possibly knowable' condition. The concern is that we want
to allow that creatures that lack the sophistication to know things
might nonetheless have hallucinations. But given the centrality of the
notion of knowledge in Martin's definition of indistinguishability, if
a creature cannot know things at all, then for any hallucination it
might have, the creature cannot know that it is not veridically
perceiving an F, or a G, or an H, and so on. So all hallucinations
will be such that, for the creature, they will qualify as
indiscriminable from each and every kind of creature perception.
In discussing this concern, Martin insists that whilst a creature
"might fail to discriminate one experience from another, making no
judgment about them as identical or distinct at all, that is not to
say that we cannot judge, in ascribing to them such experience, that
there is an event which would or would not be judgeably different from
another experience" (2004: 54). In other words, Martin suggests that
"not possibly known" should not be interpreted personally, such that a
specific creature's capacities are relevant to the question of what
qualifies as being possible to know, but rather in an impersonal way.
So in saying that a hallucination is not possibly known to be distinct
from a veridical perception of a certain kind, Martin does not mean
not possibly known by the subject but rather, not possibly known in
some impersonal sense.
Siegel argues that this claim faces the crucial problem of explaining
how we can pick out the hallucinatory 'experience' – the state or
event that is reflected upon – in an appropriate yet non
question-begging manner (2008: 212). Given Martin's view, the state or
event cannot be picked out in virtue of its having any robust features
as this would conflict with the claim that nothing more can be said of
the hallucination than that it is indiscriminable from the veridical
perception. Yet we cannot pick out the relevant state in virtue of its
indiscriminability property either. As we are trying to explain what
it is for a state of the creature's to have the indiscriminability
property in the first place, we cannot get a fix on which state we are
talking about by appeal to its being the one that has that property.
Fish's view diverges from Martin's on both of these questions. Where
Martin endorses an impersonal sense of indiscriminability, Fish
endorses a personal sense; where Martin rules out testimony, Fish
rules it in. This does mean, of course, that Fish foregoes Martin's
explanations of the indiscriminability of both animal hallucinations
and hallucinations in which the subject is aware that they are
hallucinating. In the case of animal hallucinations, Fish responds by
extending the claim that indiscriminability requires sameness of
introspective beliefs to the claim that indiscriminability requires
sameness of cognitive effects, where both behaviour and (in
conceptually sophisticated creatures) introspective beliefs qualify as
a species of cognitive effect. Then, where animals are concerned, a
hallucination can qualify as indiscriminable from a veridical
perception of a certain kind so long as it yields the kinds of
behaviour that a veridical perception of that kind would have yielded.
When it comes to known hallucinations, Fish contends that we do not
have to rule out testimony so long as we relativize the relevant
effects to the overall cognitive context the subject is in. Consider a
situation in which a subject is hallucinating but comes to believe,
through testimony, that their experience is hallucinatory and
therefore does not form the belief that they see something. Fish asks
us to consider what would be the effects of a veridical perception of
the relevant kind in a parallel situation in which a subject believes,
through testimony, that they are hallucinating. He suggests that, in
such a case, a veridical perception would likewise fail to yield the
relevant kinds of belief. On these grounds, he therefore contends that
the hallucination would still have the same cognitive effects as a
veridical perception would have had, and thereby qualifies as
indiscriminable from that perception.
Siegel also objects to Fish's version of negative disjunctivism by
pointing out that relativizing cognitive effects to particular
contexts has an unappealing consequence: that there will be contexts
in which even a veridical perception would not lead a subject to
believe that they saw something. But in such cases, she contends, a
hallucination that had the same effects as this veridical perception
would have had will lack the resources to explain how this
hallucination has a felt reality (2008: 217). Likewise, she contends
that an animal that was lethargic or sick might have a hallucination
and fail to engage in any kind of behaviour at all. Once again, Fish's
view doesn't appear to have the resources to accommodate this.
7. Theories of Illusion
So given the different approaches to the bad case of hallucination,
what can the disjunctivist say about the bad case of illusion? The two
obvious possibilities are to place illusion into one of the two
disjuncts that we already have: to treat illusions as either like
hallucinations or like veridical perceptions.
a. Illusion as Hallucination
McDowell seems to endorse the former approach. Recall his claim 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" (1982/1998: 386-7). As the veridical
disjunct contains cases in which a "fact" is made manifest then, given
that there is no such thing as a non-obtaining fact, any scenario in
which it appears to the subject that such-and-such is the case when it
is not could not be a case of a fact being made manifest. So illusions
looks to fall into the category of cases in which it merely appears as
though a fact is made manifest along with hallucinations.
However, there are concerns with an attempt to treat illusions as
hallucinations. Robinson protests that, "if all non-veridical
perceptions were treated in the same way as hallucinations, then every
case of something not looking exactly as it is would be a case in
which one was aware of some kind of subjective content. Only perfectly
veridical perceptions would be free of such subjective contents"
(1994: 159). This leads A.D. Smith to ridicule the view: the "picture
of our daily commerce with the world through perception that therefore
emerges is one of a usually indirect awareness of physical objects
occasionally interrupted by direct visions of them glimpsed in
favoured positions" (2002: 28).
b. Illusion as Veridical Perception
So perhaps we would do better to bring illusion under the perceptual,
rather than the hallucinatory, disjunct. The key disjunctions offered
by both Snowdon and Child suggest they would prefer this approach. As
illusions involve situations in which something does look to be F to a
subject, but where that thing – the thing that looks to be F – is not
really F, the fact that both Snowdon and Child characterize the
perceptual disjunct as containing cases in which something looks to S
to be F suggests that they view this disjunct as containing illusions
as well as veridical perceptions.
Now of course, if illusion is treated as a special case of veridical
perception, then the specific way in which illusion is treated will be
dictated by the theory of the good cases. Yet as we are treating
disjunctivism as not being committed to any particular theory of the
good cases, this doesn't yet tell us much about illusion. However, it
is worth noting that, as one of the most significant motivations for
disjunctivism is to make room for a naïve realist account of the good
cases, as illusions are cases in which objects look to be a way that
they are not, on the face of it, this approach to illusion would not
obviously be available to a disjunctivist who also wanted to be a
naïve realist about the good cases.
Having said this, in a recent paper, Brewer develops an account of
illusion that treats it as a special case of veridical perception,
understood in broadly naïve realist terms. Brewer's view of good case
experience is that "the core subjective character of perceptual
experience is given simply by citing the physical object which is its
mind-independent direct object." (2008: 171). But how, we might think,
could we give an analogous account of the core subjective character of
illusion? Well, suggests Brewer, when seen from different points of
view and/or in different circumstances, a certain kind of external
object/property may have "visually relevant similarities" with
paradigms of other kinds of object/property. These visually relevant
similarities may lead us to take the kind of object/property we see to
be an instance of the kind for which those visual features are
paradigm – a kind that the object/property is not, in fact, a member
of.
To grasp the notion of a kind for which certain visual features are
paradigm, consider the process of learning concepts. Our parents or
teachers guide our acquisition of kind concepts by making paradigm
instances of those kinds salient. To teach a child the meaning of the
term, "red," for example, we do not show the child a red object in
darkness, or make the child wear unusually colored spectacles; we show
the child the red object in conditions in which it will be seen as
paradigmatically red. This is because, in these conditions, the object
has visual features that are paradigm for the kind: red.
Brewer then shows how this can accommodate various kinds of illusion –
in this case, an illusion of color:
a white piece of chalk illuminated with red light looks red. The …
proposal is that the core of the subjective character of such illusory
experience is constituted by that very piece of chalk itself: a
particular … mind-independent physical object. From the viewpoint in
question, and given the relevant perceptual circumstances –
especially, of course, the abnormally red illumination – it looks red.
This consists in the fact that it has visually relevant similarities
with paradigm red objects: the light reflected from it is like that
reflected from such paradigms in normal viewing conditions (2008:
173).
On Brewer's view, then, illusions are not really "illusory" at all. In
the case just described, we are seeing the chalk as it is in those
circumstances. So the illusion is really a special case of veridical
perception. However, we would also say that the white chalk looks red.
This, Brewer suggests, is to say no more than that, in the
circumstances in which the white object is veridically seen, it has
visually relevant similarities with paradigmatically red objects. That
is all that we mean when we say that this is a case of illusion.
Whether this kind of approach can be extended to accommodate all
illusions remains to be seen.
8. Conclusion
As a theory of visual experiences, disjunctivism is very much in its
infancy, and much interesting research remains to be done.
9. References and Further Reading
References marked (*) can be found in A. Haddock and F. Macpherson
(eds.) (2008) Disjunctivism: Perception, Action, and Knowledge
(Oxford: Oxford University Press).
References marked (+) are reprinted in Byrne, A. and Logue, H. (eds.)
(2009) Disjunctivism: Contemporary Readings (Cambridge MA: The MIT
Press).
Introduction
(+) Hinton, J. M. (1967) "Visual Experiences" Mind 76, 217-27.
––– (1973) Experiences: An Inquiry into Some Ambiguities (Oxford:
Clarendon Press).
(*) Snowdon, P. (2008) "Hinton and the Origins of Disjunctivism" in A.
Haddock and F. Macpherson (eds.) Disjunctivism: Perception, Action,
and Knowledge (Oxford: Oxford University Press), 35-56.
Disjunctivism and Naïve Realism
(+) Martin, M. G. F. (1997) "The Reality of Appearances" in M.
Sainsbury (ed.) Thought and Ontology (Milan: FrancoAngeli), 81-106.
Snowdon, P. (2005) "The Formulation of Disjunctivism: A Response to
Fish" Proceedings of the Aristotelian Society 105, 129-41.
Types of Disjunctivism
(*) Byrne, A. and H. Logue (2008) "Either / Or" in A. Haddock and F.
Macpherson (eds.) Disjunctivism: Perception, Action, and Knowledge
(Oxford: Oxford University Press), 57-94.
Snowdon, P. (2005) "The Formulation of Disjunctivism: A Response to
Fish" Proceedings of the Aristotelian Society 105, 129-41.
(+) Martin, M.G.F. (2004) "The Limits of Self-Awareness" Philosophical
Studies 120, 37-89.
––– (2006) "On Being Alienated" in T.S. Gendler and J. Hawthorne
(eds.) Perceptual Experience (Oxford: Clarendon Press), 354-410.
Arguments for Disjunctivism
(+) McDowell, J. (1982) "Criteria Defeasibility and Knowledge"
Proceedings of the British Academy, 455-79.
(+) Snowdon, P. (1981) "Perception, Vision and Causation" Proceedings
of the Aristotelian Society 81, 175-92.
(+) ––– (1990) "The Objects of Perceptual Experience" Proceedings of
the. Aristotelian Society, Supplementary Volume 64, 121–50.
Epistemological Motivations
(+) Johnston, M. (2004) "The Obscure Object of Hallucination"
Philosophical Studies 120, 113-83.
McDowell, J. (1986/1998) "Singular Thought and the Extent of Inner
Space" in his Meaning, Knowledge and Reality (Cambridge MA: Harvard
University Press), 228-59.
(*) ––– (2008) "The Disjunctive Conception of Experience as Material
for a Transcendental Argument" in A. Haddock and F. Macpherson (eds.)
Disjunctivism: Perception, Action, and Knowledge (Oxford: Oxford
University Press), 376-89.
(*) Pritchard, D. (2008) "McDowellian Neo-Mooreanism" in A. Haddock
and F. Macpherson (eds.) Disjunctivism: Perception, Action, and
Knowledge (Oxford: Oxford University Press), 283-310.
Wright, C. (2002) "(Anti-)Skeptics Simple and Subtle: G.E. Moore and
John McDowell", Philosophy and Phenomenological Research, 65, 330-48.
(*) ––– (2008) "Comments on John McDowell's 'The Disjunctive
Conception of Experience as Material for a Transcendental Argument'"
in A. Haddock and F. Macpherson (eds.)
Disjunctivism: Perception, Action, and Knowledge (Oxford: Oxford
University Press), 390-404.
Modesty
(+) Martin, M.G.F. (2004) "The Limits of Self-Awareness" Philosophical
Studies 120, 37-89. Hawthorne, J. and K. Kovakovich (2006)
"Disjunctivism" Proceedings of the Aristotelian Society, Supplementary
Volume 80, 145-83.
Naïve Realism: Phenomenology
Hawthorne, J. and K. Kovakovich (2006) "Disjunctivism" Proceedings of
the Aristotelian Society, Supplementary Volume 80, 145-83.
Hellie, B. (2007) "Factive Phenomenal Characters" Philosophical
Perspectives 21, 259-306. Martin, M.G.F. (2002) "The Transparency of
Experience" Mind and Language 17, 376-425. Noordhof, P. (2002)
"Imagining Objects and Imagining Experiences" Mind and Language 17,
426-455.
Naïve Realism: Demonstrative Reference
Campbell, J. (2002) Reference and Consciousness (Oxford: Clarendon Press).
Snowdon, P. (1992) "How to interpret 'direct perception'" in T. Crane
(ed.) The Contents of Experience: Essays on Perception (Cambridge:
Cambridge University Press), 49-78.
The Causal Argument
Robinson, H. (1994) Perception (London: Routledge).
Smith, A. D. (2002) The Problem of Perception (Cambridge MA: Harvard
University Press).
(*) ––– (2008) "Disjunctivism and Discriminability" in A. Haddock and
F. Macpherson (eds.) Disjunctivism: Perception, Action, and Knowledge
(Oxford: Oxford University Press),181-204.
The "Screening Off" Objection
(+) Martin, M.G.F. (2004) "The Limits of Self-Awareness" Philosophical
Studies 120, 37-89.
––– (2006) "On Being Alienated" in T.S. Gendler and J. Hawthorne
(eds.) Perceptual Experience (Oxford: Clarendon Press), 354-410.
Matching Hallucinations to Perceptions
Farkas, K. (2006) "Indiscriminability and the Sameness of Appearance"
Proceedings of the Aristotelian Society 106, 205-25.
Hawthorne, J. and K. Kovakovich (2006) "Disjunctivism" Proceedings of
the Aristotelian Society, Supplementary Volume 80, 145-83.
Positive Disjunctivism
(+) McDowell, J. (1982) "Criteria Defeasibility and Knowledge"
Proceedings of the British Academy, 455-79.
(+) Johnston, M. (2004) "The Obscure Object of Hallucination"
Philosophical Studies 120, 113-83.
Negative Disjunctivism
(+) Martin, M.G.F. (2004) "The Limits of Self-Awareness" Philosophical
Studies 120, 37-89.
––– (2006) "On Being Alienated" in T.S. Gendler and J. Hawthorne
(eds.) Perceptual Experience (Oxford: Clarendon Press), 354-410.
(*) Fish, W.J. (2008) "Disjunctivism, Indistinguishability and the
Nature of Hallucination" in A. Haddock and F. Macpherson (eds.)
Disjunctivism: Perception, Action, and Knowledge (Oxford: Oxford
University Press), 144-167.
Negative Disjunctivism and Indiscriminability: Objections Siegel, S.
(2004) "Indiscriminability and the Phenomenal" Philosophical Studies
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