Disjunctivism and Illusion

a. d. smith

Warwick University

Disjunctivism is a theory about sensory experience that, as its very

name implies, invokes a certain contrast: between being one thing or

another (and not both). The theory claims that sensory experience

comes in certain fundamentally different and incompatible psychologi-

cal forms. Everyone would accept that, of course. What is distinctive

about disjunctivism is its claim that there are such differences, even

intrinsic ones, that the experiencing subject is necessarily not in a posi-

tion to appreciate simply in virtue of having the experiences and reflect-

ing on, or ‘‘introspecting’’, them, even though the experiences are fully

conscious ones. The contrasting kinds of experience that the disjunctiv-

ist is concerned with are those that intuitively have different cognitive

and epistemological credentials. At one extreme there is veridical

perception. Here one is perceptually aware of a real object in the

world, the object appears just as it really is, and one is thereby, at least

usually, in a position to have perceptual knowledge of this object. This

is, cognitively and epistemologically, a ‘‘good’’ case. At the other

extreme, there is hallucination. Here one is not aware of any real object

in the world at all, and the experience can furnish one with no percep-

tual knowledge of that world. This is a ‘‘bad’’ case. A hallucination

might, however, be subjectively indiscriminable from some veridical

perception, in that one could hallucinate an object of just the same per-

ceptible sort as one might veridically perceive, and the hallucination

might be so lifelike that one could not tell, simply on the basis of

‘‘what it is like’’ to have the experience, that one was not veridically

perceiving such an object. Nevertheless, claims the disjunctivist, these

two sorts of experiences, even considered just as experiences, are intrin-

sically different in nature: so different, indeed, that they should be

regarded as falling into two fundamentally different psychological

kinds. The kind of experience one has when one veridically perceives

384 A. D. SMITH

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some object in the world is one that simply cannot be had by a subject

who is not in perceptual contact with some such object. This kind of

experience is essentially ‘‘object-involving’’, and so is a kind of experi-

ence that one cannot have hallucinatorily.1 Mere subjective indiscrimi-

nability, the disjunctivist claims, should not be used as a criterion for

determining psychological nature in such cases. There is, to be sure,

something that reflective subjects of either perceptual or hallucinatory

experiences can definitely know about their conscious life just on the

basis of reflecting on their experiences. They can, for example, defi-

nitely know that it at least seems to them that they are perceiving

something of a certain sort. In order, however, to emphasise the fact

that two fundamentally different kinds of experiential state can be the

basis of such knowledge, disjunctivists prefer to express the knowledge

in question as being of a disjunctive form: the subjects know that they

are either perceiving something or that they are merely under the

impression that they are.2 We may call such a formulation an ‘‘experi-

ential disjunction’’: one that disjoins what are commonly referred to as

a ‘‘good’’ and a ‘‘bad’’ disjunct.

In this paper I address the question of what account disjunctivism

can or should give of illusion. This is a surprisingly under-discussed

topic. Although most disjunctivists do briefly mention illusion, and

sometimes commit themselves on the question of whether it should be

regarded as falling under the good or the bad disjunct of the experien-

tial disjunction, almost all their detailed discussions of bad cases con-

cern hallucination. Perhaps they sense that illusion may harbour

difficulties for the view. Be this as it may, I shall argue that the phenom-

enon of illusion, at least of certain kinds, indeed cannot be adequately

accommodated by one influential form of disjunctivism. Having estab-

lished that, I shall explore alternative versions of disjunctivism that are

not simply refuted by the facts, and ask whether illusion should be allo-

cated to the good or the bad disjunct. In as much as illusory perceptions

are indeed perceptions—perceptual contact is made with some actual

object in the environment—they share a good feature with veridical per-

ceptions. In as much as they are illusory, however, they are in some

sense ‘‘bad’’. No doubt because of this, disjunctivists themselves are

1 Those writing in this tradition treat objects as entities. In other words, non-existent

intentional objects are not ‘‘countenanced’’. For the purposes of this paper I shall

fall in with this way of thinking.2 I have argued elsewhere (Smith, 2008) that neither the notion of being under the

impression that one is perceiving, when one isn’t, nor its variants that can be found

in the disjunctivist literature (such as being subjectively indiscriminable from a per-

ception), is adequate to pick out the class of hallucinatory experiences. For present

purposes, however, I shall leave aside this somewhat important issue.

DISJUNCTIVISM AND ILLUSION 385

divided over the issue of where to place illusions in the experiential dis-

junction—as Paul Snowdon, himself a leading disjunctivist, recognises:

‘‘In one account (that embodied in the present discussion), the disjuncts

are perception and hallucinations. Into the perception disjunct would go

both accurate and inaccurate perceptions. The other accounts form a

disjunction between accurate perception on the one side and, on the

other, all non-accurate cases. These are the disjunctions to which Hin-

ton . . . and McDowell have attended’’ (1990, 131). For reasons that we

shall see, and as Snowdon himself later indicates, the case of McDowell

is not straightforward, in that his form of disjunctivism is not directly

concerned with the nature of perceptual experience. Hinton, however, is

explicitly concerned with this issue, and he does make it clear that his

bad disjunct includes both illusion and hallucination (Hinton, 1973,

114–121). Another leading disjunctivist who regards both illusion and

hallucination as constituting a bad case is M. G. F. Martin. His contrast

is always between veridical perceptions on the one hand, and states that

are merely subjectively indiscriminable from them on the other.3 Indeed,

Snowdon is in a small minority of disjunctivists in allocating illusion to

the good disjunct. I shall argue that he is right to do so.

It may not be immediately clear, to either insiders or outsiders,

whether these different decisions concerning where to place illusion in

the experiential disjunction reveal a philosophical disagreement; or, if

they do, how significant it is. One might, for example, wonder why dis-

junctivists should be required to operate with just a twofold disjunc-

tion. If the experiential disjunction were presented in terms of veridical

perception or illusory perception or hallucination, perhaps the present

issue would simply evaporate. Even someone who does work with the

simple twofold disjunction, and who places illusions along with halluci-

nations in the bad disjunct, need not deny that illusions and hallucina-

tions differ significantly, perhaps even fundamentally and essentially,

from one another. Indeed, Snowdon himself suggests that the different

formulations of the experiential disjunction ‘‘do not necessarily repre-

sent theories between which we have to choose’’ (1990, 132). Since illu-

sions seem to have both good and bad aspects, perhaps for some

philosophical purposes it is worth stressing their good aspect and asso-

ciating them with veridical perceptions, whereas for other purposes it is

worth underlining their bad aspect and allying them with hallucina-

tions. There is, however, a substantial philosophical issue involved here

on which one does have to take a stand. It is the question whether in

both illusions and hallucinations we find a kind of experience, or

3 Martin adopts disjunctivism as a way of upholding what he terms ‘‘naıve realism’’:

a position that, as we shall see, requires illusions to be placed in the bad disjunct.

386 A. D. SMITH

intrinsic feature of experience, that is necessarily not to be found in any

veridical, non-illusory perceptual experience, or conversely.4 Anyone

who, like Hinton or Martin, places illusion with hallucination in the

bad disjunct clearly thinks that this is so. When Snowdon formulates

his own perception ⁄hallucination disjunction, he may not be expressing

disagreement with this. He may simply be interested in a different issue.

It is, however, this issue that I am concerned with in this paper. When,

therefore, I refer to a form of disjunctivism that endorses the percep-

tion ⁄hallucination disjunction, and thereby allocates illusion to the

good disjunct, I mean a theory that positively claims that there is noth-

ing to illusory experiences, qua experiences, that cannot be found in

veridical experiences.5 To place illusions together with veridical percep-

tions in the good disjunct is, therefore, to commit oneself to the view

that they have, to use John McDowell’s phrase, a ‘‘highest common

factor’’ (McDowell 1982, 472). I take this phrase to express the idea

that types of experience that have such a highest common factor are of

identical psychological kinds, differing at most only in external, rela-

tional matters. As mentioned, I shall argue that such a view is the cor-

rect one for a disjunctivist to hold. Having established that, I shall

conclude by considering how significant such a ‘‘concession’’ may be.

I

In this section I argue that a certain currently influential form of disjunc-

tivism is incapable of giving an adequate account of illusion. All disjunc-

tivists agree that a veridical perceptual experience is of a psychological

type that cannot be had unless one is perceiving some item in the real

world. Most disjunctivists go beyond this, and give a particular explana-

tion of this impossibility. When some worldly object is veridically per-

ceived, this common view has it, the object is a constituent of the

experience. Paul Snowdon goes so far as to make such constituency an

4 For reasons that we shall examine later, ‘‘veridical, non-illusory’’ is not pleonastic.

Since, until then, the issues involved are not pertinent to the discussion, I shall

sometimes write ‘‘veridical’’ where ‘‘veridical and non-illusory’’ would strictly be

accurate.5 Martin (2002, 395 n24) contrasts a view that simply allocates illusions to the bad

disjunct with one that simply allocates them to the good one, and suggests that his

own position is ‘‘somewhere in between these two approaches’’. This is because

Martin construes the terms ‘‘illusory’’ and ‘‘veridical’’—quite correctly, as we shall

see—as applying primarily to the perception of features of objects, rather than of

objects as such. Given the way I have just set up the issue that is to concern us,

however, he is to be placed squarely in the camp of those who allocate illusion to

the bad disjunct. For, as we shall soon see, he certainly supposes there to be some

feature of veridical experience that cannot be found in any illusory experience in so

far as it is illusory.

DISJUNCTIVISM AND ILLUSION 387

essential part of disjunctivism as such. Disjunctivism is, he writes, ‘‘not

exhausted . . . by the simple denial of a common nature’’ to bad and good

experiences. It ‘‘involves also the characterisation of the difference

between the perceptual and non-perceptual in terms of the different con-

stituents of the experiences involved. The experience in a perceptual case

in its nature reaches out to and involves the perceived external object,

not so the experience in other cases’’ (2005, 136–7). The specific form of

disjunctivism that we shall be considering in this section interprets such

constituency as accounting not only for the fact that an experience makes

perceptual contact with the world; it accounts also for the phenomenal

character of the experience, at least in part. Martin, who subscribes to

this view, calls it ‘‘naıve realism’’, and I shall follow him in this. He speci-

fies it as follows: ‘‘According to naıve realism, the actual objects of per-

ception, the external things such as trees, tables and rainbows, which one

can perceive, and the properties which they can manifest to one when

perceived, partly constitute one’s conscious experience, and hence deter-

mine the phenomenal character of one’s experience. This talk of constitu-

tion and determination should be taken literally’’ (1997, 83, my

emphasis).6 For an object to be a constituent of an experience, therefore,

is for it to constitute and determine the phenomenal character of the

experience, at least in part. The object does this by, as it were, importing

its very own features into experience. When, for example, I veridically see

a green square, the ‘‘phenomenal greenness’’ and ‘‘phenomenal square-

ness’’ of my experience are nothing more than the physical greenness and

shape of that square featuring in my experience by way of constituency.

The reason why illusion poses a problem for such a view is that illu-

sions can be, indeed almost always are, partial. Consider, for example, a

case where a green square looks yellow to me, though it does look square.

Since I am really seeing the square, and veridically perceiving its shape,

the square and its shape are presumably constituents of my experience.7

This square’s shape furnishes the phenomenal character of the illusory

perception in some respect: in the respect of being as of a square. What,

however, about the apparent yellowness? It, clearly, must be accounted

for by something other than the green square being a constituent of the

experience, since this is the case when a green square veridically looks

green to me. Some extra, ‘‘bad’’ factor, over and above the green square’s

being a constituent, must, therefore, be attributed to this partially illu-

sory state to account for the illusorily appearing colour: something that

6 ‘‘Determines’’ implies ‘‘is sufficient for’’, as Martin makes clear: ‘‘Difference in

presented elements between two experiences will be sufficient for difference in their

phenomenal properties’’ (Martin 1998, 174).7 We shall consider later how matters stand if this is denied.

388 A. D. SMITH

is absent in the case of completely veridical perception, where the constit-

uent object itself does all the work. A naıve realist about veridical percep-

tion must, it seems, embrace a ‘‘mixed’’ account of such partial illusions,

constituency accounting for the respects in which the experience is veridi-

cal, and some extra factor accounting for the respects in which it is

illusory.8 There are a number of candidates for such a bad factor: some

representational feature, or a quale, for instance. But whatever is postu-

lated will, in certain cases, undermine the naıve realist account of the

veridical perception of an object’s features. This is because, to continue

with our example, a certain square can, through constituency, determine

an aspect of the phenomenal character of a visual experience—making it

such that something looks square—only in virtue of being seen. A visible

shape, however, necessarily has some colour; and only because an

object’s colour is seen is an object’s shape seen.9 Indeed, the apparent

shape of an object, as far as vision is concerned, just is a matter of the dis-

tribution of apparent colour. An object is visibly square to me because

and only because of how colour is distributed in my visual field.10 Because

of this, a square’s being a constituent of my experience cannot account

for why a square seems to be visually present to me unless it also

accounts for the appearance of colour. In the case in hand, the appar-

ently distributed colour is yellow; but the square is actually green. How

could a green square’s being a constituent of my experience account for

the apparent yellowness of the square? By itself, it clearly cannot. So, by

itself it cannot account even for the appearance of a square, since this

depends on apparent colour and how it is distributed. To account for the

distribution of the apparent colour is to account for the appearance of

the shape. If something other than the real square accounts for the

appearance of the colour, something other than the real square (and its

constituency) accounts for the very appearance of the square. Generally,

whatever bad factor is postulated to account for an illusorily appearing

feature in a partially illusory perceptual experience will undermine the

naıve realist account of any veridically appearing aspect whose appearing

presupposes and is fully determined by the appearing of such a feature.

It will not do to respond to this argument by claiming that, although

something other than the square accounts for which colour appears, it

8 Martin (2002, 395 n24) seems to commit himself to this account of the matter.9 What, it may be asked, about glints and gleams? One possible answer is to extend

the term ‘‘colour’’ so that it covers such phenomena. Another, which I favour, is

to deny that in seeing such a glint or gleam you are seeing a part of the object or

its surface. What you see, in these cases, is light reflected from the object.10 Things, at least usually, visually appear as located and variously oriented in three-

dimensional space. The distribution of colour of which I speak is not in some

merely two-dimensional ‘‘visual array’’.

DISJUNCTIVISM AND ILLUSION 389

could be the square that accounts for how this colour is specifically dis-

tributed. The only way, on the naıve realist account, in which the square

can do this, given that the shape is veridically perceived, is by being a

constituent of the experience. It cannot, however, be a constituent with-

out being seen; and it cannot be seen without some particular colour

appearing. According to the present response, however, an object’s being

a constituent of a visual experience does not suffice for any particular col-

our to appear. A square, through being a constituent of an experience,

cannot account for the appearance of just some colour or other. To sup-

pose otherwise is to treat constituency as a weaker notion than it in fact

is. The constituency view is not merely that an object is responsible for

the phenomenal character of an experience when the latter is veridical. It

is, rather, responsible for this character specifically in virtue of importing

its own character into the experience through constituency. It must,

therefore, import everything that is necessary for its constituency, and

hence for its veridically perceived features to be seen. This is just what

does not happen in illusory cases of the sort we are considering.

An alternative way for the naıve realist to account for such illusory

perceptions would be to deny that any extra factor is responsible for the

illusorily appearing colour. This would apply to the case in hand some-

thing like the account that Martin offers of certain hallucinations.11

According to that account, the only thing that can be said about the phe-

nomenal character of these hallucinations is that they are not subjectively

discriminable from some kind of veridical perception: their ‘‘only positive

mental characteristics are negative epistemological ones—that they can-

not be told apart by the subject from veridical perception’’ (Martin,

2004, 73–4). Applied to the illusory case of a green square looking yellow,

one would say that the square’s being a constituent of the experience

accounts for a square appearance, and that its looking specifically yellow

is simply a matter of the experience’s negative epistemological character-

istic of not being subjectively distinguishable from veridically seeing

something yellow, or something along these lines. Since no positive fea-

ture is postulated to account for the apparent yellowness, there is, it may

be thought, nothing to conflict with or undermine the real square’s actual

shape accounting for the apparent squareness through constituency. This

will not help matters, however, since it still remains impossible for the

square’s actual shape to appear at all in a way compatible with naıve real-

ism. It can appear only in virtue of some colour appearing as distributed

in a particular way, and one must account for the latter in order to

account for the former. The veridical appearance of the square is

11 The hallucinations in question are those that have the same kind of proximal cause

as some (possible) veridical perception.

390 A. D. SMITH

certainly not, however, for the naıve realist, simply a negative epistemo-

logical matter, as is, supposedly, the appearance of colour.

II

Bill Brewer has recently offered an analysis of illusory perception that,

if acceptable, would block the preceding argument against the naıve

realist form of disjunctivism. Brewer has given up his earlier representa-

tionalist account of perceptual consciousness, and now holds that per-

ceived objects not only are constituents of perceptual experience, but

that they ‘‘constitute the subjective character of perceptual experience’’

(2006, 168). Moreover, he offers an account of how this can be true in

the case of illusion. His analysis postulates ‘‘two levels in the subjective

character of experience’’. At the first level, ‘‘the mind-independent

direct object itself, just as it actually is, . . . is constitutive of this sub-

jective character’’. The second level consists of the way in which an

object presented at the first level ‘‘may mistakenly be perceptually

taken’’ (2006, 172). What is significant about Brewer’s proposal is that

error enters into an illusory experience only at this second level: it is to

be attributed solely to the subject’s response to what is perceptually

presented. ‘‘In perceptual experience,’’ he writes, ‘‘a person is simply

presented with the actual constituents of the physical world themselves.

Any errors in her worldview which result are products of the subject’s

responses to this experience, however automatic, natural or understand-

able in retrospect these responses may be. Error, strictly speaking,

given how the world actually is, is never an essential feature of experi-

ence itself’’ (2006, 169). It should be clear how naıve realism is

sustained by this account of illusion. Objects in the world can be con-

stituents of illusory experiences, and determinative of their phenomenal

character, since how they are in such experiences, at least at the first

level, is how they actually are. Any mismatch occurs only when it

comes to our response to our (first level) experiences. In a later work

Brewer is not so explicit about the two-level nature of the account; and

yet it is still in place. He still postulates that ‘‘the core subjective char-

acter of perceptual experience is given simply by citing the physical

object which is its mind-independent direct object’’ (2008, 171). In cases

of illusion, however, this physical object, given a certain point of view

and ‘‘circumstances of perception’’, bears certain visually relevant simi-

larities to a different kind of object; and these similarities may ‘‘intelli-

gibly lead’’ one to take the object as being of this other kind. It is such

similarities and the way they provide an ‘‘intelligible ground’’ for error

that constitute the illusory ‘‘look’’ of the thing (2008, 171–2 and 178).

Such a look is, however, still regarded as something over and above a

DISJUNCTIVISM AND ILLUSION 391

‘‘more basic phenomenal presentation’’ of the object that constitutes

the ‘‘core’’ subjective character of the experience (2008, 178).

Brewer illustrates how his account is meant to work by applying it to

the case of the Muller-Lyer illusion. Brewer suggests that the two objec-

tively equal lines in the Muller-Lyer figure are present as equal lines in

our core experience when we view the figure, so that the basic phenome-

nal character of our experience is indeed as of equal lines. Nevertheless,

these lines ‘‘have the power to mislead us, in virtue of their perceptually

relevant similarities with other things’’. For these lines bear a similarity

to two unequal lines, one of which is nearer to the viewer than the other

so that they have the same projective length in the plane in which the

Muller-Lyer figure is located. The inward and outward pointing wings

at the ends of the two lines function to make this similarity ‘‘salient’’,

and bring two unequal lines ‘‘to mind’’ (2006, 168–9).

Such a two-level account is not implausible in relation to some illu-

sions: those that psychologists call ‘‘cognitive illusions’’, and of which

the Muller-Lyer illusion is one. Brewer claims, however, that his account

can be applied to ‘‘many of the most standard cases of visual illusion’’

(2008, 173). Unless it applies to all types of illusion, naıve realism will

still be inadequate, but in fact it does not apply to any illusions at all

other than the ‘‘cognitive’’ ones: to any, that is to say, that are more

physiologically or physically based. It does not, for instance, to continue

with our example of colour, apply to the illusorily appearing colours

that are due either to unusual lighting or to simultaneous or successive

colour contrast. In such cases it is one’s sensory experience itself, at the

most basic level, that is affected, not just some response to the experi-

ence. Because of this, there are in such cases no visually relevant similari-

ties of the sort that Brewer can point to in the Muller-Lyer illusion. A

green square can look yellow to me because of the peculiar lighting.12

12 A naıve realist may suggest that when, as most of us would say, illusion is caused

by the behaviour of light, or by other objective features of the environment—as in

the present example, and in the familiar example of the straight stick half immersed

in water—there is really no illusion at all, since we are accurately picking up on

real features in the ‘‘external world’’. The green square is, it may be suggested, yel-

low-in-this-light, and the stick is, as we might say, ‘‘optically bent’’. (I am grateful

to an anonymous referee of this journal for raising this objection.) I reject this sug-

gestion, because it is incapable of recognising that, in the situations in question, we

get anything wrong at all about our environment. (The error cannot be attributed

to our taking the situation to be in some sense ‘‘standard’’ when it is not, since we

need not so take it: we may be perfectly well aware of the situation for what it is.)

This inadequacy is grounded on the fact that when I, for example, see a stick, it is

the shape of the stick that seems apparent to me—not its ‘‘optical shape’’. In any

case, there are many kinds of wholly internally caused, physiologically based illu-

sions—such as those due to simultaneous or successive colour contrast— in relation

to which this naıve realist proposal is a complete non-starter.

392 A. D. SMITH

There is, however, no ‘‘relevant’’ similarity at all between green and

yellow. They are simply two quite different colours. In fact, when Brewer

explicitly considers non-cognitive illusions, he is forced to make it clear

that his visually relevant similarities cover things of which the subject

may be totally unaware. ‘‘Two objects have visually relevant similari-

ties,’’ he writes, ‘‘when they share sufficiently many properties amongst

those which have a significant involvement in the physical processes

underlying vision. Thus, and very crudely, visually relevant similarities

are identities in such things as, the way in which light is reflected and

transmitted from the objects in question, and the way in which stimuli

are handled by the visual system, given its evolutionary history and our

shared training during development’’ (2008, 172). It should be evident,

however, that such similarities as these, wholly unknown to the experi-

encing subject as they typically are, can play no role in an account of

illusion that locates error only in an ‘‘intelligible’’ response to a core

experience that perfectly matches the actual situation perceived. When I

see the yellow-looking square, there is no sense at all in which I see the

light travelling to my eyes. The light does not look any way at all to

me.13 It is the square that I see and that looks a certain way. And in

cases of colour contrast, there is not even a relevant similarity in any-

thing external to the observer. According to Brewer, illusion consists in

the fact that visually relevant similarities ‘‘may intelligibly be taken for

qualitative identities’’ (2008, 173). But nothing I am wholly unaware of

can be ‘‘taken’’ by me in any way whatever. Are we really to suppose

that a white object’s looking green to me after I have been staring at a

red surface is a matter of the state of my retinal cells providing an ‘‘intel-

ligible ground’’ for a response that brings green ‘‘to mind’’? There is no

intelligibility here at all. It is just a matter of psycho-physical causation.

The ‘‘visually relevant similarities’’ in all such non-cognitive illusions

simply concern the processes that give rise to experience. They are oper-

ative before any experience occurs, even at a ‘‘first’’ level, and they

condition the phenomenal character of that experience.

Moreover, the suggestion that, in illusion, the perceived object is

accurately registered phenomenally in a first-level experience has

dropped out of Brewer’s account when it is applied to non-cognitive

illusions, or is at least playing no explanatory role. This is not surpris-

ing, since the suggestion that, in the case of non-cognitive illusions, the

actual character of the perceived object phenomenally characterises the

experience (in the respect in which it is illusory) is wholly indefensible.

In the case of the Muller-Lyer illusion, according to Brewer, an equal-

ity of the lines characterises one’s core experience—an experience that

13 Glints and gleams aside.

DISJUNCTIVISM AND ILLUSION 393

constitutes a ‘‘more basic phenomenal presentation’’ of the object than

is to be found at the second level, where alone error inters into the pic-

ture (2008, 178)). When a green object looks yellow because of the

lighting, however, greenness does not phenomenally characterise my

experience in any way at all. It is not, in such a case, simply that my

response involves an (intelligible) error. The response is just what it

should be to a core experience that is qualitatively identical to the one

I get when a yellow object looks yellow. In order to justify his claim

that equality in length does indeed characterise the core visual experi-

ence when the Muller-Lyer figure is seen, Brewer points out that the

lines in the figure would not appear to change length if the attached

wings were to shrink to vanishing point (2006, 170). This perhaps sug-

gests that there is a certain phenomenal sameness to the lines with and

without the wings; and that since the lines without wings are certainly

phenomenally equal, so are the lines in the actual Muller-Lyer figure

with their wings. Nothing analogous to this is to be found when light-

ing changes, or when a colour becomes surrounded by another colour

that gives rise to simultaneous colour contrast. In order further to jus-

tify his claim that phenomenal equality is present in the ‘‘core’’ experi-

ence of the Muller-Lyer figure, Brewer suggests that if you were to

point to where the ends of the two lines in the figure appear to be, you

will point to their actual location—which also perhaps suggests that

equality is in some way phenomenally manifest to you. Again, nothing

analogous is to be found in the case of non-cognitive illusions. When

that green square looks yellow to me, all my non-inferential responses

are those appropriate to yellow. Or, to take a non-cognitive illusion

that is closer to the Muller-Lyer illusion in that it involves spatial prop-

erties, consider the straight stick that looks bent when half submerged

in water. Here, when I point to the ends of the stick on the basis of

how it appears to me, I will not point to their actual location.

The following sort of situation also shows Brewer’s proposal to be

unworkable as a general account of illusion. Consider a situation where

you view two equal lines through distorting lenses, so that just one of

the lines looks a little longer than it is. Choose the right distortion, and

when the Muller-Lyer illusion is exemplified by adding suitable attach-

ments to the ends of the lines, the two lines will look equal with their

attachments.14 Since the attachments function the same way in this case

as in the usual Muller-Lyer case, Brewer’s two level analysis must rec-

ognise a phenomenal difference in the length of the two lines, due to

the non-cognitive illusory effect produced by the distorting lenses, at

14 This would be a case of ‘‘veridical illusion’’: a phenomenon to which we shall

attend later.

394 A. D. SMITH

the first level of experience—something that his account is meant to

rule out.

The case against a two-level account of any non-cognitive illusion is

overwhelming. At least wherever non-cognitive illusions are concerned,

the actual character of the perceived object is not, in so far as the expe-

rience is illusory, phenomenally manifest to the subject at all, at any

‘‘level’’ of experience. All such illusions therefore stand in the way of

defending naıve realism against the arguments of the previous section.

III

The only way for the naıve realist form of disjunctivism to avoid the

problems detailed above is to claim that illusory perceptual experiences,

even when they contain veridical elements, are wholly different in kind

from completely veridical perceptual experiences. The ‘‘mixed’’ account

of partial illusion we have been considering is rejected, and it is denied

that the veridical aspects of a partially illusory appearances are to be

accounted for by constituency. The question now arises, of course, how

illusions are to be distinguished from hallucinations; but that will pose

no serious problem in principle. One possibility—in fact, as far as I can

see, the only possibility consistent with the direct realism that naıve real-

ism is intent upon defending—is for the naıve realist to conceive of both

illusions and hallucinations as representational states, with no worldly

objects as constituents, but to distinguish between hallucinations and illu-

sions on the basis of a distinction between different kinds of representa-

tional content: by, for example, denying to hallucinations, but attributing

to illusory perceptual states, object-dependent representational content.15

Such an ‘‘unmixed’’ account is, however, at odds with the funda-

mental motivation for naıve realism, and, indeed, with its literal formu-

lation. As Martin has stressed on a number of occasions, naıve realism

is adopted by its proponents as being ‘‘the best articulation of how our

experiences strike us as being to introspective reflection on them’’

(2004, 42). By contrast, both sense-datum and representationalist

accounts amount to ‘‘error-theories of sense experience’’ (2004, 84).

The naıve realist is happy to convict us of error when we hallucinate,

for then we are merely under the mistaken impression that we are

really perceiving things. But the naıve realist who endorses an

‘‘unmixed’’ account of partially illusory experience must convict us of

error even when we are veridically perceiving some aspect of the sur-

rounding world. When I misperceive that green square as yellow, I see

the object’s shape just as it is. And yet my entire visual perception of

15 More on this notion below.

DISJUNCTIVISM AND ILLUSION 395

the square has, on the present unmixed account, a fundamentally dif-

ferent nature from that of any wholly veridical perception. Anything

other than a naıve realist, ‘‘constituency’’ account of perception is,

however, supposed to constitute an error-theory. ‘‘We should,’’ writes

Martin, ‘‘be moved to this position [sc. naıve realism] in defence of a

natural conception of how our veridical perceptual experience relates

us to the world around us. That is what leads us to Naıve Realism’’

(2004, 84). If so, we should be equally moved when it comes to the

veridical aspects of partially illusory perceptions. The naıve realist

claim that veridically perceived objects are constituents of perceptual

experiences is straightforwardly falsified by a case such as the yellow-

looking green square. The square is veridically perceived as a square,

but cannot, on the unmixed account, be a constituent of the perceiver’s

visual experience, because of its illusory yellowness. And yet, when I

see that green square, I see its actual shape. I see, as Wilfrid Sellars

would have put it, its very squareness. That the square looks yellow to

me in no way conflicts with this fact.

More significantly, a naıve realist account that embraces an

unmixed, representationalist account of illusion is objectively untenable

because of a variant of the following argument. Suppose, again, that I

am misperceiving that green square as yellow (though as square). On

the present account, this is a representational state that does not have

the square as a constituent. Suppose, now, that because of some change

in the situation, my representational state becomes wholly accurate.

The naıve realist surely cannot deny that this is possible. In such a situ-

ation, however, I cease to misperceive the square’s colour. Since I am

now perceiving the square in a wholly veridical way, it should now be,

for the naıve realist, a constituent of my visual experience. But the only

change I have postulated in the original experiential state is one that

concerns that state’s intentional content and its correctness. The state

remains a representational state, not one that now has physical objects

as constituents. This, however, is impossible if naıve realism is true,

and at least all wholly veridical perceptions involve the perceived object

as a constituent of experience. Such an intentionalist account will

undercut the entire naıve realist position.

I said that it is a variant of the foregoing argument that will invali-

date a naıve realist unmixed account of illusion. A variation is

required, because the argument lacks cogency as it stands. This is

because it presupposes that a wholly veridical intentional perceptual

state will necessarily involve no illusion; and this is false, since illusions

are not necessarily non-veridical in the sense of misrepresenting the

nature of the object perceived. An experience can arise, for example,

from two independently operative illusion-inducing factors—abnormal

396 A. D. SMITH

lighting and lateral inhibition or retinal fatigue, say—that precisely off-

set one another, so that how something ends up appearing is the way it

actually is.16 Some readers may not be inclined to regard this sort of

case as one of illusion at all—so tight may be the connection between

illusion and misrepresentation in some people’s minds. In fact, whether

or not such a case is properly termed an ‘‘illusion’’ is not a matter of

great philosophical importance. Everyone will, I assume, at least agree

that such a case is not a wholly optimal case of perception. One indica-

tion that it is indeed less than perceptually optimal is that we should

deny that the subject who sees a green square that looks green to him

because of two illusion-inducing factors that conspire to produce this

effect is in a position either to know that or to see that the square is

green.17 The important point, now, is that the naıve realist will not

unreasonably apply the constituency account of the phenomenal char-

acter of experience only to ‘‘optimal’’ cases of perception. If, therefore,

intentionalism is to undercut the present ‘‘unmixed’’ version of naıve

realism, it must be able to offer an acceptable account of such

‘‘optimality’’—one that involves more than mere correctness of percep-

tual representation. I now indicate how this may be done.

The reason we judge the veridical cases now under consideration to

be less than optimal cases of perception is that the veridicality of the

experiences in question is fortuitous, because of the nature of the visual

processes involved. Given just this shade of green, and just these sur-

rounding colours producing a retinal effect that gives rise to the phe-

nomenon of simultaneous colour contrast, and just this abnormal light,

the green thing looks green; but this type of situation does not reliably

give rise to accurate perception.18 This fact certainly supports our

judgement that a subject in such a situation would not know that the

object before him is indeed green. Moreover, it supports our judgement

that such a subject would not see that the object is green.19 This is not

16 Johnston (2006, 271–4) has already argued for this. The illusions he considers,

however, all involve at least one arguably ‘‘cognitive’’ illusion. Although this in no

way affects the general point, as far as the present argument is concerned it is, for

reasons we have noted earlier in connection with Brewer, better to avoid reliance

on illusions of this kind.17 If you do not think that the sort of case now in question is even less than optimal,

then you do not think that such a case harbours any problem for intentionalism as

it stands; and nor, therefore, for the suggestion that intentionalism ‘‘undercuts’’

naıve realism.18 That these two factors merely happen to conspire to produce accurate perception is

fundamental to our judgement on such cases, for we can imagine a sensory system

that works optimally, and as a matter of course, by employing two sub-systems

that reliably off-set one another in this fashion.19 Mark Johnston (2006, 271–6) has emphasised the need for any adequate account

of ‘‘veridical illusion’’ to account for this fact.

DISJUNCTIVISM AND ILLUSION 397

because seeing that entails (visually) knowing that—so that accounting

for the absence of the latter would ipso facto account for the absence

of the former. There are two sorts of situation that render such an

entailment at least dubious. First, you can clearly see that something is

the case, and yet not believe your eyes, because of some (false) collat-

eral belief that you have. One could attempt to preserve the link

between seeing that and knowing that by severing the link between

knowing and believing; but that would itself be contestable. The second

example, however, is independent of this issue. For you can clearly see

that something is the case, and correctly believe it is, even if you are in

the middle of a period when you are having spontaneous hallucinations

or illusions. Since it is a real possibility that you are hallucinating or

having an illusion now, though in fact you are not, you do not know

to be so what you see to be so. It is not, therefore, that subjects of the

sort of non-optimal visual cases now under consideration fail to see

that things are as they appear to be simply because they do not know

this, but, rather, because of the specific reason why they do not. In the

two kinds of situation just mentioned, subjects can see that things are

as they appear to be without knowing this only because the factors that

are incompatible with knowledge are extrinsic to perception itself. One

is matter of whether or not a natural perceptual belief is inhibited by

collateral information—which is matter of how a subject epistemologi-

cally exploits a perception; and the other is a matter of whether a given

perception occurs in a situation in which there is a real possibility of

certain other (hallucinatory or illusory) perceptions occurring. By con-

trast, the intentionalist’s account of ‘‘veridical illusion’’ deals with fac-

tors that are internal to perception, since it concerns the aetiology of

perceptual experience itself and, therefore, how one stands perceptually

to a certain object. The notion of seeing that comes apart from (visu-

ally) knowing that just to the extent that the former, unlike the latter,

essentially concerns just the relation in which I stand perceptually to an

object (given certain conceptual capacities and attention).

In this way an intentionalist can give an account of ‘‘optimal’’

perception that does not involve any elements of naıve realism. It is,

therefore, this account that functions to undercut the naıve realist

account of such optimal perceptions. Note that I am here not simply

playing one perceptual theory off against another. I am not simply

saying that a representationalist has an account of wholly veridical,

‘‘optimal’’ perception that is at odds with naıve realism. The point is

that the only form of naıve realism still in the field is one that is

itself committed to endorsing a representationalist theory of illusion.

So, unless naıve realists can point out some error in the foregoing

extension of the theory to cover optimal perceptual states, they will

398 A. D. SMITH

themselves be saddled with an account that invalidates their own

constituency analysis of such states, since they cannot both endorse

representationalism as an account of illusory states and yet reject an

unobjectionable development of that position that accounts for opti-

mal cases. For this reason, and also because, as I suggested at the

beginning of this section, an ‘‘unmixed’’ account of partly veridical

perceptions is anyway in conflict with the motivation of naıve real-

ism, we must conclude that such a unmixed account must be

rejected. This was, however, naıve realism’s last stand in its attempt

to account for illusion. So, naıve realism must be entirely rejected.

Disjunctivism, if it is to survive, must be dissociated from it.

IV

In this section I consider the issue of where to place illusion in the

experiential disjunction—in the good or the bad disjunct—when

naıve realism has been rejected. This issue of where to place illusion

is not independent of the fate of naıve realism, since a disjunctivist

theory that embraces naıve realism is forced to allocate illusion to

the bad disjunct—at least as I have interpreted such an assignment.

This is because, in cases of veridical, non-illusory perception, naıve

realism accounts for the phenomenal character of experience simply

in terms of a certain physical object being a constituent of the expe-

rience. The ‘‘phenomenal yellowness’’ of my veridical perception of a

canary just is a matter of that yellow bird being a constituent of my

experience. The phenomenal yellowness of my experience when I illu-

sorily see some differently coloured object as yellow must be

accounted for in some other way—a way that necessarily has no

place in accounting for the phenomenal character of veridical percep-

tion, since here the constituent object does all the work. As Martin

writes, ‘‘The naıve realist account of perceptual experience . . . can-

not be applied to any case of delusive experience, such as illusions

where one does perceive an external object, but misperceives it as

other than it really is. If we suppose that such cases involve the

same type of mental state, perceptual experience, as veridical percep-

tion, then that will directly contradict the naıve realist account even

of those cases’’ (1997, 85).20 Since, however, naıve realism must be

20 In so far as Brewer’s form of naıve realism regards illusion as occurring subse-

quently to experience itself, in some ‘‘response’’ to such experience, he assigns illu-

sions, or at least the truly experiential components of illusions, to the good

disjunct. But that is because, in effect, Brewer does not recognise illusion as a genu-

inely sensory phenomenon at all.

DISJUNCTIVISM AND ILLUSION 399

rejected, the question of where to place illusion in the experiential

disjunction remains open.

Naıve realism involves a certain way of interpreting the common

disjunctivist claim that in good perceptual cases a certain object is a

constituent of experience. Such a constituency view does not in and

of itself amount to naıve realism, however. I have already quoted

Paul Snowdon claiming that such constituency is an essential ingredi-

ent in any theory that deserves to be regarded as a form of disjunc-

tivism; and yet he himself does not endorse naıve realism, in the

present sense, in any of his writings. Indeed, he informs me that he

rejects it. Does such a form of disjunctivism—one that accepts con-

stituency but rejects naıve realism—also determine where illusion is

to be placed in the experiential disjunction? It does: illusion must be

placed in the good disjunct—as Snowdon himself consistently does.

For in rejecting naıve realism—the view that a worldly constituent

of an experience determines the phenomenal character of that exper-

ience—the present form of disjunctivism is left with no role for

constituency other than to constitute an experience as being a

perceptual experience, rather than a mere hallucination. Constituency

simply ensures, or expresses the fact, that perceptual contact is made

with the real world. And for those disjunctivists (the vast majority)

who peddle the idea of constituency, it is this issue of whether a

perceived object is a constituent of a sensory experience or not that

alone determines the fundamental psychological kind to which the

experience is to be allocated—and, therefore, on which side of the

‘‘experiential disjunction’’ the experience falls.

Despite what Snowdon claims, however, it is not necessary for a dis-

junctivist to hold that worldly objects are constituents of ‘‘good’’ expe-

riences. He is certainly right that ‘‘the mere denial of a common

nature’’, as he puts it, does not fully capture the disjunctivist position.

It is necessary that this lack of a common nature derive from a differ-

ence in how one stands cognitively to the world. It is precisely because

certain experiences require the world to be a certain way, and require

us to stand in a certain cognitively favourable relation to that world,

that they count as good perceptual cases. With them, and with them

alone, is the world perceptually ‘‘present’’ to one in some sense that is

prized. A constituency view of experience is not required in order to

capture all of this, however. So we have not yet covered all possible

forms of disjunctivism.

What sort of theory it is that both counts as a form of disjunctivism

and yet rejects the idea that worldly objects are constituents of even good

experiences? According to many writers, any direct realist theory that

rejects a constituency account of perceptual experience amounts to some

400 A. D. SMITH

form of ‘‘representationalist’’ or ‘‘intentionalist’’ theory of experience.21

Such a theory holds that sensory experience, both perceptual and halluci-

natory, possesses ‘‘intentional (or representational) content’’ in virtue of

which such experience presents the world as being a certain way. What is

thus presented—some object or state of affairs in the world—is always

distinct from the experience that presents it. Intentional content also

determines, at least in part, the phenomenal character of experience.22 It

is, I believe, correct to hold that such a theory is the only direct realist

alternative to a constituency view—though calling it a ‘‘representational-

ist’’ theory may cause some hackles to rise. One can understand resistance

to the idea that anyone who denies that worldly objects are constituents

of experience is committed to viewing us as merely ‘‘representing’’ the

world when we plainly and directly perceive it. Perhaps the alternative

term ‘‘intentionalist’’ will help to allay such fears. Moreover, one can,

where perception is concerned, restrict the term ‘‘represent’’ and its cog-

nates to the experiences themselves and the sensory systems involved in

their production, and deny that the subject (‘‘merely’’) represents how

things are. When the world is represented by a subject’s experiences in a

certain way, the world is presented to the subject of these experiences. It

is, it may be held, the experiential character of such representations that

renders the term ‘‘represent’’ inappropriate as applied to the subject of

experience. If such scruples about ‘‘merely representing’’ the world are

respected, as I believe they can be, it does seem to me that intentionalist

(or, as I shall, in fact, also write, ‘‘representationalist’’) accounts of

experience are the only direct realist alternative to a constituency view.

Although many intentionalists are not disjunctivists at all, there is

certainly a possible marriage between the two positions.23 This will be

possible, however, only if an intentionalist account of experience recog-

nises two fundamentally different ways of experientially representing

the world—one characterising the good, and one the bad, disjunct.

These two ways must, for an intentionalist, be spelled out in terms of a

21 For example, Brewer (2006, 168) states that a constituency view is ‘‘the only alter-

native to characterizing experience by its representational content’’. Martin (2002)

concurs. Phenomenalists and certain indirect realists will fall into neither category,

of course. It is, however, only direct realist accounts of perception that need to be

considered here, since disjunctivism, whatever else it is, is essentially a direct realist

perceptual theory.22 Many intentionalist theories are reductive, in the sense that they claim that sensory

experience is nothing but a matter of representing the world in a certain way. In-

tentionalism need not be thus reductive. Husserl is a classical non-reductivist. More

recently Block (e.g., 2003) has advocated a non-reductive version. This issue is not,

however, relevant to the present discussion, however important in its own right.23 Alex Byrne (2001, 202 n7), for example, makes it clear that his own representation-

alist theory is compatible with disjunctivism.

DISJUNCTIVISM AND ILLUSION 401

difference in intentional content.24 Since it is definitive of disjunctivism

that one cannot enjoy a good experiential state without perceiving

some real object in the world, the sort of intentional content that is

required in order to confer such ‘‘good’’ status on an experience is

object-dependent content: a type of content, that is to say, that a psy-

chological state can have only when it is the case that there really is an

object that the state represents. Nothing short of this would guarantee

that the experiences that possess such content are of such a kind that

they are possible only when some real object is being perceived, as dis-

junctivism requires. More than this may, however, be required if an in-

tentionalist account is to do justice to the disjunctivist position, even

when it is specified that the psychological states in question are sensory

in character.25 Paul Snowdon has suggested to me that any case where

one hallucinates a familiar object shows that experiential object-depen-

dent content is too weak a notion to capture disjunctivist claims. The

psychological state here is, it may be thought, both sensory and object-

involving; and yet, being a hallucination, it falls under the bad disjunct.

For reasons I have given elsewhere (2002, 265–6), I reject the sugges-

tion that hallucinatory experiences themselves can contain the sort of

object-dependent content suggested by Snowdon. But let us suppose

that they can. If so, the intentionalist disjunctivist must appeal to a

more specific type of intentional content: one that requires not just the

(sometime) existence of its object, but that object’s presence. Such con-

tent, and the experiences that possess it, need to be, we might say, not

merely object-dependent, but object-involving.26 Such content is itself

24 Although, as mentioned in n22 above, intentionalism need not offer a reductive

account of sensory experience, and so can recognise something other than representa-

tional content as intrinsic to, and even as essential to, such experience, no such extra

feature is able to sustain a disjunctivist division of experiences into different funda-

mental kinds. The only non-representational variation in sensory states that any rep-

resentationalist will countenance is in some irreducible sensory features of such states:

qualia. Qualia, however, are supposed to account only for the phenomenal character

of experiences (at least in part). Since both illusions and hallucinations can be phe-

nomenally identical to veridical perceptions, no such variation in sensory character

can constitute the disjunctivist’s fundamental difference in kind of psychological state.25 According to Martin, ‘‘If one holds that the content of perceptual experience can

be singular, and also holds that singular content is object-dependent, then one will

thereby be forced to be disjunctivist’’ (2002, 395 n25). This may well be right; but,

as we are about to see, the point is not self-evident.26 Martin (2003) has signalled a different distinction by contrasting the terms ‘‘object-

involving’’ and ‘‘object-dependent’’. He draws his own distinction as part of an

exploration of a possible non-disjunctivist position that yet construes perceptual

experience as object-involving. (The account in question is Tyler Burge’s.) Since

Martin’s distinction is of significance only in relation to such an account, and since

that account is not disjunctivist, it is not relevant to the present discussion, what-

ever intrinsic interest it may have.

402 A. D. SMITH

sometimes characterised these days, employing a natural extension of

the term, as demonstrative. It is such content, the intentionalist will

hold, that underwrites successful perceptual judgement to the effect that

this object is such and such. It is the absence of such content in the hal-

lucinatory case that explains why any such demonstrative judgement

there misfires. This sketch will have to suffice here to indicate the sort

of intentionalist theory that can embody disjunctivism, since what we

are primarily concerned with are the consequences of embracing such a

theory for an account of illusion.27

Distinguishing between experiences on the basis of whether their

intentional content is or is not object-involving, or ‘‘demonstrative’’, is

clearly going to be at the heart of any intentionalist form of disjunctiv-

ism. Distinguishing experiences in this way will not, however, serve to

distinguish illusions from veridical perceptions, but only perceptions of

either sort from hallucinations. Both illusory and veridical perceptions

will have such object-involving content in virtue of the fact that both

are perceptions. The perfectly obvious essential difference between an

illusion and a hallucination is that in the former, but not the latter, a

real object is perceived—just as is the case with veridical perception.

An intentionalist will certainly attribute object-involving content to

veridical, non-illusory perceptions. But it is hardly because such ‘‘opti-

mal’’ perceptions are specifically veridical that this is the right thing to

say. My non-illusory perception of a green square does not possess

object-involving content because I get the square’s colour right: it is

simply because I am actually seeing the square—something I can do

even though I get the colour wrong as a result of illusion. My seeing

the square puts me in a position to make a certain sort of demons-

trative judgement: one to the effect that this object is green. This

judgement is possible, for the intentionalist, only because of the object-

involvingness of the experiential state of which it is an expression. The

same will hold when I misperceive the object as yellow. My natural

judgement, in such a case, to the effect that ‘‘this is yellow’’ will be

27 A final word on this issue, though. John Campbell (2002, 135–6) interprets such an

intentionalist account as construing experience in terms of grasping a demonstra-

tive, object-dependent thought. He then, quite reasonably, goes on to criticise any

such account as failing to do justice to the distinctive role that experience plays in

relation to thought. The intentionalist form of disjunctivism that we are now con-

sidering, however, views experiences themselves as possessing object-dependent con-

tent. Such experiences will put a suitably cognitively equipped subject in a position

to entertain a corresponding demonstrative thought; but they are not themselves

modes of thinking. (They could, indeed, be wholly non-conceptual in nature.)

Campbell interprets an intentionalist account in the way he does because of a

restriction of intentionality to thinking, which there is absolutely no reason to

accept.

DISJUNCTIVISM AND ILLUSION 403

mistaken, of course; but this judgement can be entertained at all only

because of the perceptual presence of the object itself—something that

the object-involving content of an experience alone guarantees.

Although intentionalist disjunctivism cannot distinguish between illu-

sory and non-illusory perceptual states in terms of the above sort of

object-involving content, it may be thought that it can do so in terms

of an element of content that relates specifically to features of objects.

When I ‘‘optimally’’ see a green square, I not only see the square, but

also, to echo Sellars again, its very greenness. On the basis of so seeing

the square and its colour I can think demonstratively of this green col-

our, and mean by that, not some repeatable shade of colour, however

determinate, but a particular instance of colour. When I hallucinate, I

can do no such thing. And perhaps I am not in a position to think

demonstratively about an object’s features when those features are illu-

sorily perceived (even veridically). The suggestion would be that in vir-

tue of the illusory nature of a perception of a thing’s colour, the

experience at best visually represents a certain colour as instantiated,

but not a particular instantiation of a colour. There is no actual

instance of a colour that it represents. This approach would give us a

neat threefold distinction. An optimal perception is demonstratively

related to its object and its veridically perceived features; an illusory

perception is demonstratively related to its object, but not to its illuso-

rily perceived features; and hallucination is demonstratively related to

nothing, though it putatively is. On this basis one could allocate illu-

sion to the bad disjunct in virtue of its not, in so far as it is illusory,

representing an object’s features in a manner suitable for sustaining

demonstrative judgement.

This proposal will not work, however, since what has just been said

of ‘‘optimal’’ perceptions, as supposedly distinctive and essential to

them, applies equally, and essentially, to illusory perceptions. When we

illusorily perceive an object, we perceive the object’s features—even the

ones that illusorily appear to us. To deny this is to deny that we see an

object at all in at least some illusory cases. For one cannot perceive a

thing at all without perceiving some feature that it has; and one cannot

consciously perceive a thing at all (so that it consciously seems a cer-

tain way to the subject) without consciously perceiving some feature

that it has (and that, therefore, itself appears a certain way to the sub-

ject). We have already seen that visually perceiving an object’s shape

requires seeing that object’s colour. So if, in seeing a green square that

looks yellow to me, I did not see the object’s colour, I would not see

its shape either. If these are the only two features of the object that

appear to me, as may be the case, I would therefore not see anything

of the object at all. Indeed, we can suppose that I misperceive both the

404 A. D. SMITH

object’s colour and its shape. If it is claimed that, because of illusion, I

fail to see either of these features of the object, then, even more obvi-

ously, I end up not seeing it at all.28 So, when that green square looks

yellow to me, I perceive its colour: its actual colour, that is, since it has

no other. Since I see the square’s colour, and that colour is green, I see

the square’s greenness (though not as green, of course). It is, indeed,

precisely this greenness that looks yellow to me. What other feature

could it be? And nothing can look a certain way to me unless I see it.

If it had had a different colour, doubtless that colour would not have

looked yellow to me in this light. Again, suppose the colour of this

green square were (really, objectively) to turn a darker shade—in

response, say, to a change in temperature. In some, perhaps most, such

cases, the apparent yellowness would seem to become darker. Here I

would be seeing the actual darkening of the square’s colour—some-

thing I could not do were I not seeing its colour. It is only because of

the fact that, when we suffer illusion, we illusorily perceive the actual

features of an object that a suitably cognitively equipped subject can,

on the basis of an illusory experience, make a perceptual demonstrative

judgement about the actual features of the object perceived. Seeing the

green square as I do—that is, as yellow—I could judge that this col-

our—that is to say, this colour instance—is qualitatively identical to

that of some canary I had recently seen. Here I would be making a per-

ceptually based demonstrative judgement about the actual colour of

the square: something I could not do if I were not perceiving it and

visually representing it in an object-involving way. That I would indeed

be making such a judgement is clear from the fact that such a judge-

ment would be false—rather than entirely lacking an object or subject

matter. And the reason for this is that the square, unlike the canary, is

not really yellow.29 Even illusion is, we may say, ‘‘feature-involving’’.

Intentionalism cannot, therefore, distinguish between illusory and

veridical perceptual states in term of an intrinsic difference in inten-

tional content. It can do so in terms of the distinction between the

accuracy and inaccuracy of the intentional content; but this is an

extrinsic matter. We saw earlier that the existence of veridical illusion

shows that a distinction between accuracy and inaccuracy is not

28 A surprisingly large number of philosophers have claimed that it is impossible for

all the perceived features of an object to be perceived illusorily: that illusion must

be partial. There is nothing whatever to be said for this view. For a brief discussion

and diagnosis of this error, see my (2002, 82–3).29 I could, of course, judge that the colour the square appears to me to have is identi-

cal to that of the canary, and then I would be correct. In the straightforward situa-

tion in question, however, I am making the simpler judgement about the colour of

the square.

DISJUNCTIVISM AND ILLUSION 405

sufficient to account for the distinction between illusory and non-illu-

sory (or, at least, optimal and non-optimal) perceptual states. Never-

theless, the extra resources that were employed there to make good this

deficiency are insufficient to locate illusion in the bad disjunct. All that

was required for a state to be non-optimal, even though it was veridi-

cal, was that it not put one in a position either to know that or to see

that the perceived object is really as it appears (in some relevant

respect), and this was spelled out in terms of the perceptual processes

involved only fortuitously resulting in veridical perceptual states (when

they do). This, too, is an extrinsic matter, at least for an intentionalist.

Indeed, for an intentionalist, the only relevant intrinsic features of

intentional states are features of intentional content.30 But on this

score, as we have just seen, there is no differentiating between optimal

perceptual states and non-optimal ones.

Nevertheless, it may occur to some readers that bringing into the in-

tentionalist account of non-optimality a reference to the possibility of

knowledge provides the basis for regarding illusory perceptions

(whether veridical or not) as intrinsically different in kind from any

non-illusory perceptions. In particular, readers may be reminded of

John McDowell’s form of disjunctivism. He contrasts psychological

states, allocating them to the good or the bad disjunct, precisely in

terms of their potentiality for giving the subject knowledge. The dis-

junction that McDowell typically employs is that of a fact being mani-

fest to one as opposed to the mere appearance of such a fact. That a

fact is manifest to one does not mean that one knows it to obtain.

What the manifestness of a fact does, rather, is to ‘‘make knowledge

of the fact available to one’’ (McDowell 1982, 457). According to

McDowell, ‘‘for some purposes the notion of being in a position to

know something is more interesting than the notion of actually know-

ing it’’ (ibid., n1). If, however, psychological states are allocated to the

good or the bad disjunct on this basis, it looks as if the intentionalist

account ought to put illusion squarely in the bad disjunct of the

perceptual disjunction.

As I mentioned earlier, however, although McDowell is certainly a

disjunctivist of sorts, his disjunctivism is not a perceptual theory at all.

That his concern is but indirectly related to the issue of the nature of

perceptual experience is made clear when he considers a subject whose

visual system properly operates only fitfully, in such a way that he is

prone to hallucinate things. On an occasion where it is working prop-

erly (though he does not know this), the subject sees a certain object,

and sees it veridically and non-illusorily. According to McDowell, this

30 See n24 above.

406 A. D. SMITH

constitutes a ‘‘bad’’ case. This subject is not in a position to acquire

knowledge, and no fact is manifest to him, since for all he knows he

could be hallucinating. Although, in McDowell’s example, the subject

genuinely sees a tomato in front of him, he ‘‘need not count as experi-

encing the presence of a tomato. . . One counts as experiencing the fact

making itself manifest only in the exercise of a (fallible) capacity to tell

how things are’’ (ibid.). For McDowell, therefore, even a veridical,

non-illusory perceptual experience is, in virtue of an unfavourable con-

text, to be allocated to the bad disjunct. It is not types of experience as

such that McDowell is interested in classifying disjunctively, but experi-

ences-in-a-context. And this is the most that a theory that works with

the notion of being in a position to know can claim.

We must conclude, therefore, that intentionalism cannot regard illu-

sion as an intrinsically different sort of fundamental psychological state

from non-illusory perception, and so is unable to place illusion any-

where other than in the good disjunct. Since this is also true of Snow-

don’s version of disjunctivism, and these are the only two disjunctivist

alternatives to the discredited naıve realist theory, we must conclude

that disjunctivism as such must allocate illusion to the good perceptual

disjunct.

V

We should finally consider what significance such a ‘‘concession’’ may

have. Presumably those philosophers who have both embraced disjunc-

tivism and have placed illusions in the bad disjunct did so because they

thought that otherwise some unfortunate cognitive consequence would

ensue; or that some cognitive virtue would otherwise be lost. In order

fully to appreciate the possible effect of our concession, we should need

to see what it precisely is that disjunctivism is supposed to uphold; and

unfortunately there are almost as many such aims as there are disjunc-

tivists. I shall, therefore, restrict myself to addressing two related con-

cerns that are, I think, fundamental. Disjunctivists, whatever other

aims and interests they may have, are concerned to defend direct real-

ism, and believe that disjunctivism is the only way to defend it. It may

be thought that the present concessive proposal puts such direct realism

in peril, because it requires us to acknowledge that there is a ‘‘highest

common factor’’ to illusory perceptual states and veridical, non-illusory

ones. This may be thought worrying, because it implies that when we

normally and non-illusorily see a thing, we do so in virtue of having a

type of experience that might have been illusory. This does not, how-

ever, in any way imperil direct realism. It might, if the common funda-

mental kind to which both illusory and non-illusory perceptions are

DISJUNCTIVISM AND ILLUSION 407

assigned were insufficient to constitute direct awareness of the world.

One can, therefore, understand a worry about the suggestion that there

is a highest common factor, a complete identity in psychological nat-

ure, in veridical perception and a possible hallucination. Since a hallu-

cinatory state involves no awareness of the world, and yet just such a

state supposedly constitutes the entire experiential dimension of a

veridical perception, even the latter can, it may be thought, afford no

experiential direct awareness of the world either. I do not say that this

line of thought is unanswerable, but one can at least see the worry.

When it comes to veridical and illusory perceptions, however, the

worry is not even visible, since the latter do give one a direct awareness

of the world, in virtue of being, unlike hallucinations, perceptions. At

least we need some argument to show that they do not; and I cannot

think of one that ought to be convincing to a disjunctivist.

There is, however, a remaining concern that may be thought not to

be adequately addressed by pointing out that allocating illusion to the

good disjunct in no way impugns direct realism. This concern is to pre-

serve the thought that in non-illusory perception, and here alone, an

object and its perceptible features are manifest to one. When I non-illu-

sorily perceive a green square, its greenness is immediately present to

my consciousness. When it illusorily looks yellow, however, something

less than this is the case—even when, as in veridical illusion, it really is

yellow. This observation, even if correct, will support the decision to

place illusion in the bad disjunct, however, only if such manifestness is

an intrinsic and essential characteristic of a certain kind of experience.

It can be this, however, only if naıve realism is true, which it is not.

For in order for the observation to be correct, manifestness must at

least require that the object be accurately perceived. So, if manifestness

is an intrinsic and essential feature of a kind of experience, so is accu-

racy. Accuracy is clearly not an essential feature of experiences accord-

ing to intentionalism. Nor is it according to Snowdon’s version of the

constituency theory. It can be an essential feature only on the naıve

realist account of things, where constituency—certainly an essential

matter—determines the phenomenological character of an experience,

and hence ensures accuracy. Naıve realism is false, however; and these

are the only direct realist options. Such manifestness cannot, therefore,

be an essential feature of experiences, and our observation loses its

force as an objection to placing illusion in the good disjunct. If there is

a sense of ‘‘manifest’’, as doubtless there is, according to which the

world is never manifest to one in virtue of perceiving illusorily, then

such manifestness is something that accrues accidentally to any intrinsi-

cally specified kind of experience. There is, perhaps, a weaker sense of

the term according to which only certain intrinsically specifiable kinds

408 A. D. SMITH

of experience allow the world to be ‘‘manifest’’ to us. In this sense,

however, for the world to be manifest is just for it to be directly per-

ceived—something that holds for perceptual experience as such,

whether it be illusory or not. It is understandable why one might want

such openness to the world to be written into the very nature of a cer-

tain kind of experience. To demand that, in addition, accuracy be built

into the very nature of such experience is to want too much. Indeed,

disjunctivists should not be at all hesitant in allocating illusion to the

good disjunct, since the clear fundamental distinction in this area is

between all perceptions, whether illusory or not, on the one hand, and

mere hallucinations on the other. Both illusory and non-illusory per-

ceptions are genuine perceptions. With both, perceptual contact is

made with some real item in the physical world, and it itself appears

some way to the perceiver.31 On their basis, demonstrative thoughts

about a perceived object are equally possible for suitable cognitively

equipped subjects. All this indicates a fundamental sameness of kind.

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