mental lives. This article, which has three main sections, discusses
both of these phenomena, and the connection between them. The first
part discusses mental images and, in particular, the dispute about
their representational nature that has become known as the imagery
debate. The second part turns to the faculty of the imagination,
discussing the long philosophical tradition linking mental imagery and
the imagination—a tradition that came under attack in the early part
of the twentieth century with the rise of behaviorism. Finally, the
third part of this article examines modal epistemology, where the
imagination has been thought to serve an important philosophical
function, namely, as a guide to possibility.
1. The Imagery Debate
Consider the following list of questions:
* What shape are a beagle's ears?
* How many windows are in your bedroom?
* Which is a darker shade of green, a pine tree or a frozen pea?
* When a person stands up straight, which is higher, her navel
or her wrist?
* If the letter D is turned on its back and put on top of a J,
what does the combination remind you of?
When attempting to answer these questions, which are adapted from
Pinker 1997 and Kosslyn 1995, you undoubtedly produced mental
imagery—images of beagles, of windows, and of peas. For some of these
questions, you probably had to produce two different images to compare
to one another, while for some of the other questions, you probably
had to rotate the image you produced from the orientation at which it
started. These tasks probably also seemed routine—the production and
manipulation of mental images are common aspects of our mental lives.
But what are these mental images? What role do they play in our mental
life? In attempting to answer these questions, philosophers and
cognitive scientists have given two very different sorts of answer.
a. Two Views About Mental Images: Pictorialism vs. Descriptionalism
We are naturally inclined to think of mental images as analogous to
non-mental images. Consider, for example, my mental image of the Grand
Canyon and a photograph of the Grand Canyon. Intuitively, the two are
similar sorts of representations. Both are pictures—only the latter is
in a frame while the former is in my head.
This view of mental images, commonly referred to as pictorialism, is
defended most prominently by Fodor (1975) and Kosslyn (1980). (See
also Kosslyn and Pomerantz 1977.) In addition to its intuitive
attractiveness, pictorialism derives support from various empirical
experiments concerning mental image rotation and scanning (Shepard and
Metzler 1971; Kosslyn 1973; Shepard and Cooper 1982). In one such
experiment, subjects were asked to identify whether a pair of figures,
such as letters, digits, or block formations, were identical or
different. In each pair, the second figure had been rotated to an
orientation different from the first. The experimenters discovered
that subjects' response times varied directly with the degree of
rotation between the figures, a finding that suggests that the
subjects were mentally rotating images of the objects.
Despite this intuitive and empirical support, however, pictorialism
runs into trouble in its attempt to account for the mental pictures
(or, at least, the quasi-pictures—see Kosslyn 1980) that it posits. If
such pictures are non-physical, then they are not made of the right
sort of "stuff" for use in a scientific conception of the mind. In
order to avoid dualism, then, the pictorialist seems forced to suppose
that these pictures in the head are located in the brain.
Unfortunately, this supposition is also problematic, as it is not
clear that there are any structures in the brain that could plausibly
be construed as these physical pictures.
Motivated in large part by such worries, many philosophers and other
researchers in contemporary cognitive science advocate an alternative
view called descriptionalism. Among its most prominent defenders are
Dennett (1969, 1979) and Pylyshyn (1973, 1978). While pictorialists
claim that mental images represent roughly in the way that pictures
represent, descriptionalists claim that they represent roughly in the
way that language represents. Consider a state of affairs where George
W. Bush is seated to the right of Dick Cheney. One way to represent
this situation is by drawing a picture of Bush and Cheney with Bush
sitting to Cheney's right. As we have seen, pictorialists claim that
this provides us with a model for the way that mental images
represent. But another way to represent the same state of affairs is
with a sentence such as, "George W. Bush is sitting to the right of
Dick Cheney." Descriptionalists claim that this provides a better
model for the way that mental images represent.
Natural language descriptions, however, are by no means the only kind
of representations that count as descriptional in the sense intended
by descriptionalists. In fact, for the descriptionalists, a
representation can count as descriptional even if it is not literally
descriptive of the states of affairs represented. Consider one such
representation: the binary language of a computer. In a computational
system, a particular string of 0s and 1s might represent the above
state of affairs. Alternatively, consider a representation of this
state of affairs that proceeds by defining a certain operator, the
"RIGHT-OF" operator, that takes an ordered argument pair:
RIGHT-OF(George W. Bush, Dick Cheney). Like the sentence "George W.
Bush is sitting to the right of Dick Cheney," the binary
representation and the operator representation are clearly not
pictorial in nature. One important reason is that these
representations do not look like what they represent. What sets
pictorial representations apart from other representations is that
they represent in virtue of having at least one visual characteristic
(e.g., form, shape, or color) in common with what they represent. So,
for example, though a black-and-white photograph can represent a
pumpkin pictorially, a drawing of a purple triangle cannot.
The dispute between the pictorialists and the descriptionalists, known
as the imagery debate, has generated considerable controversy and
discussion in the last thirty years. As we have seen, the imagery
debate concerns the representative nature of mental images. The
descriptionalists challenge the pictorialists' claim that mental
images represent in a pictorial way. Unfortunately, the imagery debate
is commonly mischaracterized as a debate over the existence of mental
images. Descriptionalists are often taken to be denying the existence
of mental images, while pictorialists are often taken to be defending
their existence. (See Block 1981a for discussion of this
mischaracterization.) The situation is exacerbated by the very
participants in the debate, who themselves often obfuscate the issue
between them. Dennett (1979) describes the debate as "a war between
the believers and the skeptics, the lovers of mental images … and
those who decry or deny them," and he frequently puts his own position
in terms of "abandoning" mental images. Likewise, Fodor (1975) cites
empirical studies in an effort to "argue forcibly for the
psychological reality of images." The pictorialist, however, should
really be seen as arguing for the psychological reality of pictorial
representation, which is also what the descriptionalist should be seen
as abandoning.
b. The Argument from Introspection
It is also important to note that the imagery debate is not a debate
over whether we "think in words" or "think in images." To see this, it
will be useful to consider the argument from introspection that is
directed at descriptionalism. When we introspect, it seems to us that
our mental images look like what they represent. This introspective
judgment is often taken as definitive support for pictorialism, since
pictorial representations look like what they represent while
descriptional representations do not.
Block (1983) and Tye (1991) each argue persuasively that this argument
should be rejected. Properly understood, the evidence from
introspection can be seen to be neutral with respect to the imagery
debate. To see this, we need to distinguish the experience of imaging
from the representation that underlies or accounts for this
experience. Consider the following analogy: Suppose you were to come
across a box on whose surface was displayed a crude black and white
image of a rabbit in a meadow. You might then ask: What is going on
inside this box to account for the rabbit-image? One possibility is
that some sort of slide projector inside the box projects the
rabbit-image onto the box's surface. If this were the case, then what
underlies the image would be a pictorial process. But another
possibility is that a computer inside the box produces the
rabbit-image by way of binary code – strings of 0s and 1s that turn
certain pixels on the surface of the box to black, certain pixels to
gray, and so on, such that the rabbit image appears. If this were the
case, then what underlies the image would be a non-pictorial process.
As this analogy suggests, the pictorialists claim that underlying the
experience of mental imagery is some sort of representation that is
pictorial in nature while the descriptionalists claim that underlying
the experience of mental imagery is some sort of representation that
is descriptional or linguistic in nature. By distinguishing between
experiences and the underlying representations, we undercut the force
of the introspective judgment that lies at the heart of the argument
from introspection, namely, that mental images look like what they
represent.
Pictorialists and descriptionalists alike thus accept that we
sometimes think in images. In other words, pictorialists and
descriptionalists agree that we have certain imagistic experiences,
that we experience what we would call "imaging." When we introspect,
when we look within, it seems to us as if we are experiencing mental
pictures. But the experience is one thing, the representation that
accounts for this experience another. The pictorialists think that the
introspective data should be interpreted just as it seems—our mind
manipulates representations that are pictorial in nature. The
pictorialist view thus offers us a unified conception of our
experiences and the representations that underlie them. In contrast,
the descriptionalists think that the introspective data is misleading
in a certain sense; our experiences are not quite as they seem.
Insofar as it seems to us that we have certain mental representations
that are pictorial in nature, we are the victims of an illusion.
In defending descriptionalism against the argument from introspection,
Tye (1991) makes the further point that all that introspection really
suggests is that imaging is like perception: "to assert that a mental
image of my brother, say, looks to me like my brother is merely to
assert that my imagistic experience is like the perceptual experience
I undergo when I view my brother with my eyes." Empirical experiments
have tended to confirm introspective reports that imaging resembles
perceiving. Perky (1910) placed a number of people in a room, facing a
screen, and asked them to produce mental images of various ordinary
objects on the screen. The subjects were not aware of the fact that,
after they had reported that they were engaged in the requested
imaging (of a banana, for example), an image of a banana was lightly
projected onto the screen. The projected image was slowly increased in
intensity until, eventually, it was visible to any newcomer entering
the room. Nonetheless, the subjects never realized that they were
seeing an image of a banana. The only differences that they noted in
their subjective experiences were changes in the size and the
orientation of the banana they had been imaging. In this highly
controlled setting at least, seeing was mistaken for visual imaging.
Additional empirical evidence strongly suggests that the mechanisms
underlying imagery and underlying perception are the same. (For an
overview of some such experiments, see Finke and Shepard 1986.) One
set of important results was generated by Kosslyn (1993), who
demonstrated using positron emission tomography (PET) that areas of
the brain activated when we engage in object recognition are also
activated when we produce visual mental imagery. Other important
results come from studies on patients who have suffered damage to
parts of their visual system. Bisiach and Luzzatti (1978) studied
patients who suffer from hemi-neglect, i.e., patients who ignore
objects in one half of their visual field. These patients were
discovered also to neglect objects in the same half when producing
mental images. To give another example, prosopagnosiacs, who cannot
recognize faces, have been shown to suffer from similar difficulties
when interpreting mental imagery (Levine, Warach, and Farah 1985).
Given the totality of the evidence, both introspective and empirical,
it seems reasonable to assume that the representations underlying the
experience of imagery are like the representations that underlie the
experience of perception. Importantly, however, the representations
that underlie the experience of perception may themselves be
descriptional in nature. Thus, without a theory of the nature of the
representation underlying perceptual experience, evidence connecting
mental imagery with perception cannot be taken as support for
pictorialism.
c. Objections to Pictorialism
While the above considerations suggest that the argument from
introspection should be rejected, they do not entail the truth of
descriptionalism. So why would anyone embrace descriptionalism? One
influential consideration, as noted earlier, comes from the seeming
incompatibility of pictorialism and materialism. This problem, at
least in part, is what Block (1983) has called the No Seeum Objection:
when we look in the brain, we do not see any pictures.
Of course, when we look in the brain, we do not see any descriptions
either. But, in contrast to the pictorialists, the descriptionalists
seem to have an easy response to the No Seeum charge. Sterelny (1986)
notes that, since sentences are not medium-dependent, accounting for
descriptional representations in the brain is unproblematic:
"Sentences can come as sound waves, marks on paper, electrical pulses,
punched cards, and so on. Why not then as patterns of neural firings
as well?"
Interestingly, Block (1983) argues that we can extend this sort of
response to protect pictorialism from the No Seeum objection as well.
To know whether you are looking at a descriptional representation, you
must be familiar with the representational medium that is in use.
Block proposes that the pictorialist can adopt this same line of
reasoning. What makes something the sort of representation that it is,
regardless of whether it is pictorial or descriptional, depends in
large part on the system of representation in which it functions.
Thus, until we know more about how the representational system of the
brain works, we are unlikely even to be able to tell which structures
in the brain are representations, let alone what sort of
representations they are.
Descriptionalism has also been thought to gain support from the
Paraphernalia Objection to pictorialism: even if we were to discover
pictures in the brain, these pictures could not play a role in our
cognitive processes unless there were an internal eye to see the
pictures, and since there is no such internal eye, pictorialism must
be false. (See Rey 1981, Block 1983 for discussion of this objection.)
Dennett (1969) voices the Paraphernalia objection by way of an apt
analogy:
Imagine a fool putting a television camera on his car and
connecting it to a small receiver under the bonnet so the engine could
'see where it is going'. The madness in this is that although an image
has been provided, no provision has been made for anyone or anything
analogous to a perceiver to watch the image.
According to the Paraphernalia objection, the pictorialist is like
this fool. Block (1983) and Kosslyn (1980) each suggest responses that
the pictorialist can make to this objection; in short, the basic
strategy is to invoke mechanistic explanation.
Finally, Dennett (1969) presents two examples that seem to cause
trouble for pictorialism and provide support for descriptionalism. The
first example involves a striped tiger. (See also Armstrong 1968 for a
related example involving a speckled hen.) Form a mental image of a
tiger and then try to answer the following question: How many stripes
does that tiger have? Invariably, the question cannot be answered; the
mental images that we form typically do not contain that information.
However, just as all tigers have a definite number of stripes, so too
do all pictures of tigers. Thus, if mental images were pictorial, a
mental image of a tiger should reveal a definite number of stripes.
More formally, the objection to pictorialism that the striped tiger
example poses can be stated as follows:
1. Mental images can be indeterminate with respect to visual
properties (e.g., the number of stripes on a tiger).
2. Pictorial representations cannot be indeterminate with
respect to visual properties.
3. So, mental images are not pictorial representations.
Dennett's second example attempts to show that mental images can be
noncommittal in a way in which pictorial representations generally
cannot. (See also Shorter 1952. In what follows, I slightly modify
Dennett's example. See Block 1981a for a discussion of why the example
needs modification.) Form a mental image of a tall woman wearing a hat
and then try to answer the following questions: What kind of hat was
it? Was she sitting or standing? Was she indoors or outdoors? Was she
wearing shoes? Was she wearing a watch? Though you can undoubtedly
answer some of these questions—probably you can tell what kind of hat
the woman was wearing in your image, be it a beret or a cowboy hat or
a baseball cap—you were probably unable to answer some of the others.
When asked whether she was indoors or outdoors, or whether she was
wearing a watch, you probably did not have enough information to
answer the question. And this need not be because you imagined her
only from the neck up. Even if you imagined her full-figure before
you, your image likely did not go into sufficient detail to enable you
to answer whether she was wearing a watch.
Consider next a picture of a tall woman wearing a hat. Dennett argues
that in a pictorial representation of the woman, assuming that her
wrists are in view, she must either be depicted wearing a watch or not
wearing a watch. The only way for the picture to avoid addressing the
issue would be to have something obscuring the woman's wrists. This
seems to differentiate the representational nature of a mental image
from the representational nature of a picture. Your image can be
inexplicitly noncommittal about whether she is wearing a watch, but a
picture can only be explicitly noncommittal about it. (This
terminology derives from Block 1981a.)
Finally, consider a written description of the woman. Clearly a
description can be inexplicitly noncommittal. Your description might
be very short, for example, which would make it impossible to tell
whether the woman was wearing a watch or not. Dennett thus concludes
that mental imagery has to be descriptional, and not pictorial, in
nature.
In response to this example, Block (1981a), Fodor (1975), and Tye
(1991) have each argued that Dennett is operating with too narrow a
conception of pictorial representation, accusing him of committing the
photographic fallacy. If we consider photographs, which are one kind
of pictorial representation, then it might seem that Dennett is right:
photographs are incapable of being inexplicitly noncommittal about
visual features. But consideration of photographs does not show that
pictorial representation in general lacks this option. In particular,
consider children's drawings or stick figures. In drawing a stick
figure of a woman, you might simply fail to go into the matter of the
woman's wristwear. There are lots of different kinds of pictorial
representation, and although both stick figure drawings and
photographs represent pictorially, they do so in very different ways.
The pictorialists' claim that mental images represent pictorially
should not force one to the position that mental images are like
mental snapshots; they might be more like mental stick-figure
drawings.
Interestingly, these points about the photographic fallacy do not
protect the pictorialist from the striped tiger example. Since there
is a difference between being inexplicitly noncommittal and being
indeterminate, the fact that some pictorial representations, like
stick figures, are able to be inexplicitly noncommittal about certain
visual features does not show that they can be indeterminate about
these visual features. The descriptionalist might argue that just as a
photograph has to depict a determinate number of stripes on the tiger,
so too does a stick-figure drawing.
Fodor (1975) suggests a way to deny the first premise of the above
argument. It might be that there is some definite answer to the
question, "how many stripes does my image-tiger have?" but that I
cannot answer the question because images are labile (changing
constantly, plastic); the problem is that we cannot hold onto our
images long enough to count the stripes. Ultimately, however, Fodor
rejects the second premise of the above argument, suggesting that on
blurry or out-of-focus pictures there may not be a determinate answer
to the question, "How many stripes are there on the photograph?" (See
Hannay 1971 for a similar treatment of the problem.)
Alternatively, the pictorialist might reject the move that Dennett
seems to make from the claim:
(a) I cannot count the stripes on the tiger in my mental image
to the claim:
(b)The mental image is indeterminate with respect to the number of stripes.
Your mental image might well be determinate without your being able to
count the stripes. For example, if you only get a fleeting glance at
an actual tiger, you are not going to be able to count his stripes.
(See Lyons 1984 for a suggestion of this sort.) But that does not
entail that the tiger has an indeterminate number of stripes.
d. A Remaining Question About Pictorial vs. Descriptional Representation
Above, in explaining the descriptionalist view, I noted that
descriptional representations need not be literally descriptive.
Descriptional representations are characterized primarily negatively,
i.e., for the purposes of understanding the imagery debate, a
representation will count as descriptional as long as it is not
pictorial. This assumes, however, that we have a clear understanding
of what makes a representation pictorial. Unfortunately, spelling out
exactly what makes a representation a pictorial one—or, to put it
another way, spelling out the nature of depiction—turns out to be
rather difficult.
It is standardly noted that a pictorial representation must have at
least one feature in common with what it is representing. Not just any
feature will do, so we will have to limit ourselves to visual
features. Suppose that we could specify, without begging any
questions, what a visual feature is. In any case, we can surely
identify some uncontroversial examples of visual features, such as
color and shape, even if we cannot give a precise specification of
what makes something a visual feature. Nonetheless, it soon becomes
apparent that merely sharing the visual feature of color with the
thing represented seems insufficient to make a representation
pictorial. To take an obvious example, writing the noun "apple" in red
ink does not make it a pictorial representation of an apple. (See Rey
1981 and Hopkins 1995 for further discussion of the nature of
depiction.)
In the absence of a clear characterization of pictorial
representation, some recent accounts of mental images may seem
difficult to classify as either pictorialist or descriptionalist. For
example, Tye (1991) claims that his own view of mental imagery—which
treats images as interpreted, symbol-filled arrays—is a "hybrid" one.
Since these arrays are in some respects like pictures but in other
respects like linguistic representations, Tye claims that his view
cannot be easily classified as either pictorialist or
descriptionalist.
2. Accounts of Imagination
Mental imagery clearly plays a role in many mental activities. For
example, memory often proceeds by way of imagery. But no mental
activity is more prominently linked with mental imagery than that of
imagining. In this section, I will discuss different accounts of the
imagination, paying particular attention to the connections between
imagery and imagination.
a. Image-Based Theories
Descartes' treatment of the imagination (1642/1984) is representative
of a long philosophical tradition that analyzes imagination in terms
of mental imagery. As he says in his Meditations on First Philosophy:
[I]f I want to think of a chiliagon, although I understand that it
is a figure consisting of a thousand sides just as well as I
understand the triangle to be a three-sided figure, I do not in the
same way imagine the thousand sides or see them as if they were
present before me. … But suppose I am dealing with a pentagon: I can
of course understand the figure of a pentagon, just as I can the
figure of a chiliagon, without the help of the imagination; but I can
also imagine a pentagon, by applying the mind's eye to its five sides
and the area contained within them. And in doing this I notice quite
clearly that imagination requires a peculiar effort of mind which is
not required for understanding.
Presumably, what he means by this "peculiar effort of mind" is the
effort to produce an image. In this way, Descartes sharply
distinguishes the act of imagining from the related intellectual act
of conceiving (or, in his terms, the act of understanding).
On this understanding of the imagination, imagining is thought of as
importantly analogous to perception. This fits well with various
experimental data (notably, Perky 1910) and corresponds to a long
philosophical tradition of treating imagining as an inferior kind of
perceiving. For example, Hobbes (1651/1968) refers to imagining as
"decaying sense" and Berkeley (1734/1965) claims that sense
perceptions are "more strong, lively, and distinct" than our
imaginings.
This analogy between imagining and perceiving makes it natural to
consider imagination as a kind of perception with the "mind's eye."
Again, Descartes' discussion of the imagination in the Sixth
Meditation provides a representative example of this:
When I imagine a triangle, for example, I do not merely understand
that it is a figure bounded by three lines, but at the same time I
also see the three lines with my mind's eye as if they were present
before me; and this is what I call imagining. (1642/1984)
Of course, there are clear instances of imagining in which the mind's
"eye" is not doing any work at all, i.e., in which visual images are
not involved. Vendler (1984) gives examples such as imagining the roar
of the lion, imagining the smell of onions frying on a grill,
imagining the heat of the sun, imagining the pain in one's molar. The
image-based account thus must extend the notion of image to encompass
imagistic representations from other sensory modalities. Presumably,
there are counterparts to visual images for each of the other
senses—auditory images, olfactory images, and so on. The case of
imagining the pain in one's molar can be dealt with in a parallel way.
Although pain is not perceived by one of the five traditional senses,
there is an analogue to sensory images that comes into play in this
case: what is often called an affective image.
Even with this broad understanding of the notion of image, however,
there are instances of uses of the word "imagine" in everyday language
that do not seem to involve mental imagery. Consider cases where
"imagine" is used to signal supposition (or, even more commonly, false
supposition), as when a parent who says, "I imagined that my daughter
was in her room last night, when in fact I now learn that she snuck
out her bedroom window." Consider also cases where "imagine" is used
as part of various idiomatic expressions, as when someone says,
"Imagine that!" in response to some surprising news.
Fortunately for the proponent of an image-based account, such cases
can be easily dismissed. Surely it is unreasonable to expect that we
should have to accommodate every ordinary language use of "imagine" or
its cognates when giving an account of the imagination. (But see White
1990 for a contrary view.) Rather, what we should focus on are the
cases where the imagination is actually being exercised and attempt to
explain the nature of such imaginative exercises. This is what the
proponent of the image-based account attempts to do.
So let us focus on actual exercises of the imagination. Are there any
such exercises in which there is no mental imagery? Ryle (1949)
answers in the affirmative. Though he grants that acts commonly
described as "having a mental picture" of something are instances of
imagining, he argues that concentrating on these sorts of examples to
the exclusion of others gives us a misleading picture of what the
imagination is. Consider:
1. a witness who lies when she takes the stand
2. an inventor who contemplates the machine she is working on
3. a novelist working out the plot of her next book
4. a group of children who are pretending that they are bears.
In these cases, Ryle claims that the witness, the inventor, the
novelist, and the children may be exercising their imaginations
without accompanying imagery. (In fact, the exercises of the
imagination that occur when the judge listens to the lying witness'
story, the inventor's colleague comments on the new machine, someone
reads the novel, and the mother ignores the growls emanating from the
"bears," also might well proceed without imagery.) Think about what is
going on when a group of children "play bears." They get down on their
hands and knees, growl at each other, probably rearrange the sofa
cushions to make dens for themselves, and so on—but while engaging in
this activity, they need not produce mental imagery of, say, furry
paws and the snowbound den.
In response to Ryle's discussion, the proponent of an image-based
conception of the imagination might argue that these cases conflate
being imaginative with exercising the imagination. But even if this
suggestion covers the above cases, there are additional examples for
which the suggestion lacks plausibility. White (1990) suggests that
"we can imagine, or be unable to imagine, what the neighbours will
think or why someone should try to kill us, just as we can imagine
that the neighbours envy us or that someone is trying to kill us. Yet
none of these imagined situations is something picturable in visual,
auditory or tangible terms and, therefore, none is something
pertaining to imagery." Likewise, although we can imagine George W.
Bush playing the electric guitar, how (assuming that imagining
requires imagery) can we imagine his having a secret desire to be a
rock and roll musician? What image could we produce to imagine, as
John Lennon exhorts us to do, that there's no heaven?
In addition to dealing with counterexamples such as these, there are
two questions that any proponent of an image-based account must
answer:
(1)What role does the image play in imagining?
(2)What makes an imagining the imagining that it is?
Image-based theories have often been saddled with an unfortunate
answer to the first of these questions. First, once someone invokes
mental images in an account of imagination, she appears to commit
herself to the claim that such images are the objects of our
imaginings—a highly implausible claim. (For development of this
argument, see Vendler 1984.) In brief, the problem with this view is
that when I imagine something, say George W. Bush, my imagining is
about George W. Bush, not about a mental image. The proponent of an
image-based account thus must find some other way of answering
question (1).
Interestingly, image-based theories have also often been saddled with
an unfortunate answer to the second question, namely, that the image
involved in an imagining serves to individuate the imagining from
other imaginings. The problem, however, is that imagery seems neither
necessary nor sufficient to make an imagining the imagining it is. The
basic worry traces back to Wittgenstein (1953), who wrote, "What makes
my image of him into an image of him? Not its looking like him." (See
also Tidman 1994.) Consider the following two examples from White
(1990):
One is imagining exactly the same thing when one imagines that,
for example, a sailor is scrambling ashore on a desert island, however
varied one's imagery may be.
The imagery of a sailor scrambling ashore could be exactly the
same as that of his twin brother crawling backwards into the sea, yet
to imagine one of these is quite different from imagining the other.
Although proponents of image-based theories have various options for
answering both of these questions (see Kind 2001), the associated
problems have often led to the abandonment of image-based accounts.
b. Non-Image-Based Theories
In response to the apparent problems besetting image-based accounts
(particularly the apparent counterexamples discussed above), many
theorists deemphasize the role and importance of mental imagery in
imagination. While accepting that some exercises of the imagination
involve imagery, they deny that the imagery plays any sort of
essential role in making a mental act an act of the imagination;
moreover, they also claim that there are other instances of imagining
that do not involve imagery. Scruton (1974) and Walton (1990) both
offer theories of this sort. Scruton claims that "imagining may, and
often does, involve imagery" but that "neither [imagination nor
imagery] is a necessary feature of the other." Walton accepts that
some exercises of the imagination "consist partly in having mental
images," but claims also that "imagining can occur without imagery."
Hidé Ishiguru (1966) deemphasizes the image even further. On
Ishiguru's view, imagery never plays an essential role in imagining:
"mental images are, at most, necessary tools for a limited number of
people in certain kinds of exercise of the imagination and are, for
many people, merely psychological accompaniments which occur when they
are engaged in imaginative work and not the essence of it." Finally,
another non-image-based account is offered by White (1990), who claims
that to imagine a state of affairs is to think of it as possibly being
so.
Perhaps the most important variety of non-image-based account,
however, is the experiential theory. Lyons (1986), Peacocke (1985),
and Vendler (1984) each offer a version of this theory. While there
are significant differences between these three philosophers' versions
of the experiential theory, there are nonetheless important
similarities, and I will here concentrate on Vendler's version as
representative of the tradition that analyzes imagining in terms of
experience.
Vendler explicitly treats imagination as a kind of vicarious
experience, claiming that "the materia ex qua of all imagination is
imagined experience." To motivate this account, Vendler contrasts two
different kinds of imaginative exercises. First, imagine swimming in
cold water. Next, imagine yourself swimming in cold water. In the
first case, what you do is to imagine the salty taste of the water,
the feel of the waves as they lap against you, and so on. You put
yourself in the water from the inside. Vendler calls this subjective
imagining. In the second case, one thing you might do is to picture
yourself in the water, so you see your head bobbing in the waves, and
so on. Once again, you put yourself in the water, but in this case you
do it from the outside. Vendler calls this objective imagining.
Notice that I can adopt the same objective perspective in imagining
someone else. I can just as easily imagine my sister or my husband
swimming in the ocean as I can imagine myself swimming in the ocean.
But subjective imagining works differently. There, I conjure up the
experiences that I would be having if I were in certain circumstances,
and it seems that I can do this only about myself. In objective
imagining, I imagine what someone, myself included, would look like in
a certain situation; in subjective imagining, I imagine what the
situation itself would feel like.
Clearly, subjective imagining involves evoking experiences. When I
imagine swimming in the ocean, I evoke experiences like feeling cold,
being pulled by the current, and seeing the shoreline. Interestingly,
however, Vendler argues that objective imagining also requires us to
evoke experiences. When I imagine myself swimming in the water, I am
essentially imagining the experience of seeing (or hearing, etc.)
myself swimming in the water. Thus, objective imagination ultimately
reduces to a specialized kind of subjective imagination. According to
Vendler, the materials of both subjective and objective imagination
are basically the same, namely, experiences. Both kinds of imagination
are constructions out of experiences, but the constructions proceed in
slightly different ways: "In the subjective case the aim is to
represent a consciousness, one's own, or someone else's, at a given
point of life-history. In the objective case the purpose is to
represent a thing as it appears in the field of experience" (Vendler
1984).
Adopting an experiential account has interesting consequences for
answering the question: What can we imagine? The basic form of
subjective imagining is "I imagine -ing," suggesting that we can
substitute any activity for . But Vendler does not believe that we
can. Consider being dead, or being sound asleep, or snoring while
sound asleep. These are activities, or states of being, that lack
experiential content. According to an experiential account of
imagining, it is a necessary condition on imagining performing a
certain action (or imagining being in a certain condition C) that
there be an experiential content to -ing (or to being C). Thus these
are activities that Vendler does not think we can imagine.
An interesting corollary of this necessary condition comes out in
Nagel's seminal paper, "What is it like to be a bat?" (1974). Bats are
mammals, and most of us would probably share the intuition that they
have conscious experiences, but bats perceive the external world in a
way that is radically different from the way we perceive the external
world: they use sonar, or echolocation. They emit high-pitched, subtly
modulated noises and then detect objects that are in range on the
basis of the reflections they detect. This raises an interesting
question: can we know what it is like to be a bat? In attempting to
answer this question, Nagel implicitly endorses the claim of an
experiential account that we can only imagine what we can experience;
as he notes, "Our own experience provides the basic material for our
imagination, whose range is therefore limited." Because Nagel thinks
our imagination does not allow us to extrapolate to the experience of
bats, he denies that we can imagine what it is like to be a bat. This
shows that on an experiential account, not only must there be an
experiential content to -ing (or to being C), but also it must be the
case that the experiential content is in principle accessible to the
imaginer.
Although the experiential account has some intuitive plausibility, the
reduction of objective imagination to subjective imagination requires
the proponent of the experiential analysis to do some fancy footwork
in response to certain occurrences of the word "imagine" that come up
in everyday speech. For example, it is quite common to say things
like:
"Imagine that there is life on Mars."
"I can pretty clearly imagine why she married him."
"Imagine what would happen if the NAFTA treaty had not been signed."
In each case, it seems as if we change the meaning of each of these
mental exercises if we insert the word "seeing." Imagining that there
is life on Mars might not entail putting myself into the situation as
observer, that is, it seems that it need not involve imagining seeing
that there is life on Mars. Similar points can be made about the other
two cases.
To deal with this problem, Vendler argues that the word "imagine"
functions differently in these cases from the way it functions in the
cases of objective and subjective imagination that we've been talking
about. In essence, Vendler denies that these claims describe genuine
exercises of the imagination. Just as one might say "I can pretty well
see why she married him" without implying that one was doing something
with one's eyes, one can say "I can pretty well imagine why she
married him" without implying that one is doing something with one's
imagination. In this case, it seems plausible to suppose that what is
going on is an exercise of reasoning rather than a perceptual or
imaginative exercise. (This recalls the strategy used by the
image-based theorists to dismiss cases in which the word "imagining"
seems to mean only supposition.)
There are, however, other cases that Vendler may not be able to
dismiss as easily. Some of these are the sorts of cases that threaten
image-based accounts—both image-based theories and experiential
theories have trouble accounting for apparently non-perceptual
imagining, as when someone imagines a solution to a problem. White
(1990) suggests other examples as well; for example, one can imagine
"sacrificing everything for one's principles or selling one's
birthright for a mess of pottage, without giving oneself a
representation of any experiences." Or, to use another of White's
examples, suppose someone imagines giving up all she has for love. It
is hard for the experiential theorist to dismiss this as an exercise
of mere reasoning, but likewise, it is not plausible to suggest that
in such an imagining what one is doing is imagining seeing oneself
giving up all one has for love.
Interestingly, the fact that examples of the sort that threatened
image-based accounts reappear in the context of experiential accounts
suggests an important connection between these two types of accounts.
Though image-based accounts and experiential accounts initially appear
clearly different, in that they draw attention to different features
that make an act an act of the imagination, it can be argued that the
experiential analysis entails that acts of the imagination will
involve mental imagery. If such an argument were to succeed, then the
experiential account would ultimately collapse into an image-based
account. Recall that Vendler claims that the material of the
imagination is imagined experience. The image-based theorist might try
to argue that these experiences can only be understood in terms of
imagery. Similar points might be made about other experiential
theories. For example, Lyons (1986) offers an experiential analysis
according to which imagination is the "replay" of perception. For
Lyons, when someone imagines something, she does not form a mental
image but rather rehearses, reactivates, or replays the act of seeing
that thing. But since, as we saw above, empirical evidence strongly
suggests that the mechanisms underlying imagery and underlying
perception are the same, the replay of perception will likely involve
imagery as well.
As the foregoing suggests, even if experiential theories do not
analyze imagination in terms of imagery, such theories may be thought
at least implicitly to rely on imagery. Thus, insofar as mental
imagery is ontologically problematic, such problems will likely
confront experiential theories as well as image-based theories.
Ontological worries about imagery began with the rise of behaviorism
in the early twentieth century. As the mind-brain identity theory
gained currency in the 1950s, worries about imagery grew, since the
very existence of mental images has been thought to raise an
ontological problem for such theories. To put the problem crudely,
images are not the right sort of "stuff" for use in a scientific
explanation of the mind. This problem has engendered a strong
antipathy for mental images in the second half of the twentieth
century. Correspondingly, many of the mid- to late-twentieth century
theories of imagination, such as those offered by Ryle (1949), Shorter
(1952), Armstrong (1968), and Dennett (1969), are imageless theories.
Ryle's theory, which is probably the most developed of the imageless
theories, was constructed in direct reaction to the Cartesian view of
imagining. Ryle worries that once we think of imagining as a sort of
seeing with the mind's eye, we are inclined to suppose that there
exist things, mental images, that are seen with the mind's eye. His
goal is to prevent this natural move: "the familiar truth that people
are constantly seeing things in their minds' eyes and hearing things
in their heads is no proof that there exist things which they see and
hear…." His defense of this claim relies in large part on an analogy:
Just as the fact that a murder is staged as part of a play does not
entail that there is a victim actually murdered, the fact that we see
things with the mind's eye does not entail that there are things
actually seen. This analogy also leads Ryle to a positive theory of
the imagination. Since an actor's resemblance to a murderer can be
explained by the fact that he is pretending to be a murderer, and
pretending to murder, we can also explain the similarity between the
imaginer and the observer by invoking the notion of pretense. More
generally, Ryle claims that imagining is a species of pretending.
Ryle is clearly right that there are similarities between imagining
and pretending; in particular, there is what we might call an "air of
hypotheticality" to both activities. But despite such similarities, it
seems a mistake to characterize the former sort of activity in terms
of the latter. As Ryle characterizes it, pretending is typically a
performance intended to convince, while imagining is the sort of
pretending that typically aims at convincing oneself rather than
others. But many cases of imagining involve no attempt at
persuasion—even of oneself. Consider various different kinds of
imagining: imagining one's next dentist appointment, imagining the
pain of having a tooth pulled, or imagining the tooth itself. In none
of these imaginings must we suppose that the imaginer tries to
convince herself of anything. White (1990) criticizes Ryle's analogy
between pretending and imagining in detail, elaborating numerous
differences between these two types of activities. (See also Hamlyn
1994.)
Kind (2001), in addition to providing further criticism of Ryle's
account, argues more generally that any theory of imageless imagining
is likely to be unsatisfactory. The argument rests on the inability of
imageless theories to account sufficiently for three features of
imagining: its directedness, its active nature, and its phenomenology.
A theory which assimilates imagining to pretending, as Ryle's did, can
account for the active nature of imagining, and perhaps for its
directedness, but not for its distinctive phenomenology. Another
option available to the imageless theorist, such assimilating
imagining to belief, will account for its directedness, but not for
its active nature or its phenomenology. Likewise, if the imageless
theorist were to assimilate imagining to sensation, he could account
for its phenomenology, and perhaps for its directedness, but not for
its active nature. Though Kind admits that there may be other options
available to the imageless theorist, she takes her reflection on the
above examples to suggest the basic difficulty that any imageless
theory confronts: It seems that an adequate account of imagination
must invoke some sort of mental representation in order to account for
the directedness and active nature of imagining, but non-imagistic
mental representations seem unable to account for imagining's
phenomenology. The invocation of imagery seems to be the only way to
account for the three features of imagining in conjunction.
3. Imagination and Possibility
Now that we have reflected on the nature of the imagination, in this
last section let us consider briefly the role that imagination plays
in modal epistemology. Like Hume (1739/1969), who wrote in the
Treatise that "nothing we imagine is absolutely impossible,"
contemporary philosophers have often associated the imaginable with
the possible. Moreover, it is commonly supposed that the faculty of
the imagination is an important tool in our acquisition of modal
knowledge; the imagination, it is thought, serves as an
epistemological guide to possibility.
Strictly speaking, the above quotation from Hume draws a connection
between what we (in fact) imagine and what is possible, but
philosophers have generally drawn the evidential link between what is
imaginable and what is possible. Conversely, there has also been
thought to be an evidential link between what is unimaginable and what
is impossible; Hume claimed, for example, that our inability to
imagine a mountain without a valley leads us to regard a valley-less
mountain as impossible. The traditional conception of the link between
imagination and possibility thus comprises the following two claims:
Unimaginability claim: if something is unimaginable, then it is impossible.
Imaginability claim: if something is imaginable, then it is possible.
Though these claims did not originate with Hume—Descartes (1642/1984),
for example, famously relied on the imaginability claim in his
argument for dualism, drawing the conclusion that disembodiment is
possible from the premise that disembodiment is imaginable—he is the
philosopher with whom they are most commonly associated. Thus, I will
refer to them jointly as the Humean thesis.
Many different notions of possibility abound in contemporary
philosophical discussion, so we should be clear that the possibility
invoked by the Humean thesis is usually meant to be a very weak one,
namely, logical possibility. Importantly, logical possibility far
outstrips physical possibility; what is physically possible is
governed by the laws of physics, but what is logically possible is
governed only by the laws of logic. Were the imagination meant to be a
guide to the physically possible, the imaginability claim would be
immediately problematic. Many physical impossibilities seem easily
imaginable: I might imagine a juggling pin remaining suspended in the
air after having been thrown there, or I might imagine the eight ball
remaining absolutely motionless after I hit it with the cue ball.
Ultimately, it seems that an analogy to perception motivates the
Humean thesis: imagination is supposed to give rise to knowledge of
possibility as perception gives rise to knowledge of the actual world.
Our knowledge of the world in which we live is grounded largely in
perception. But, since we have no sensory access to what is not
actually the case, perception can afford us no real insight into
non-actualized possibilities. In contrast, the imagination is not
limited to what is actually the case. This feature of the imagination,
in conjunction with the close connection between perception and
imagination, is what seems to lead us to rely on the imagination for
knowledge of possibility.
In fact, we need only to reflect briefly on how we typically form
modal judgments to see the force of the Humean thesis. Presumably, we
are convinced that it is possible for there to be purple cows, and for
humans to fly unaided by machines, as a result of our imaginings: we
can imagine a purple cow, and we can imagine humans flying without
mechanical aid. Likewise, consider how we would determine whether
round squares are possible, or whether it would have been possible for
me to have been a fish. Our conviction that these are impossible
states of affairs springs from our inability to imagine them. As Hart
(1988) writes, "One's own experience in settling modal questions seems
to show that the imagination plays a fundamental role."
But despite this intuitive support for the Humean thesis, there is
legitimate reason to worry about it. The unimaginability claim in
particular has been thought to be especially problematic. One problem
derives from the fact that there is considerable variation among
individuals' imaginative capacities. Jill might be able to imagine
many things that Jack cannot, in which case it would seem clear that
we are by no means entitled to infer from the fact that Jack cannot
imagine something that it is impossible. Fortunately, this problem can
be fairly easily resolved by interpreting "unimaginable" as something
like "unimaginable by any human." Another problem is the fact that
there might be features of human psychology that make certain states
of affairs in principle unimaginable by any of us. But if the
unimaginability of a state of affairs is due solely to some
psychological limitation on our part, then we would not seem to be
justified in inferring the impossibility of such a state. (See White
1990; Tidman 1994.)
Most problematic, however, is that the limitation of the possible to
the imaginable, particularly on an image-based analysis of
imagination, seems overly restrictive. Insofar as the imagination
cannot extend to non-sensory objects and states of affairs,
philosophers claim that we should not draw conclusions about
impossibility based on unimaginability. For this reason, the Humean
thesis is often interpreted as about conceivability rather than
imaginability, where conception is supposed to be an intellectual
faculty. (See Yablo 1993; Tidman 1994. But see Hart 1988 and Kind 2002
for arguments against this interpretation of the Humean thesis.)
The imaginability claim is generally thought to be less problematic
than the unimaginability claim, and as such it (and/or the parallel
conceivability claim) is often used in philosophical arguments.
Modern-day philosophers of mind, in the tradition of the Cartesian
argument mentioned above, argue that certain of our imaginings condemn
type materialism. Type materialism is committed to the claim that
pain, for example, is necessarily identical to a certain brain state,
call it "S". Insofar as we can imagine creatures who are in pain
despite lacking biological brains (and thus S-states) altogether, it
seems that it is possible for pain to be distinct from S-states.
Related imaginings are brought to bear against functionalist theories
of mind. To defend their theories, materialists and functionalists
either argue directly against the imaginability claim, suggesting that
imagining is not a reliable guide to possibility, or argue that in the
imaginings in question we have not imagined what we think we have (Tye
1995). This latter point has led to a general cautionary tone in
recent discussions of the connection between imagination and
possibility, with many philosophers greatly restricting both the kind
of imagining that can serve as an epistemic guide to modality and the
kind of possibility to which imagining can serve as a guide (see
Chalmers 2002 and Yablo 1993).
4. References and Further Reading
Armstrong, D. 1968. A Materialist Theory of the Mind. London:
Routledge & Kegan Paul.
Berkeley, G. 1734/1965. "A Treatise Concerning the Principles of Human
Knowledge" and "Three Dialogues Between Hylas and Philonous." In
George Berkeley: Principles, Dialogues, and Philosophical
Correspondence, edited with an introduction by C.M. Turbayne.
Indianapolis: Bobbs-Merrill Educational Publishing.
Bisiach, E., and Luzzatti, C. 1978. "Unilateral Neglect of
Representational Space." Cortex 14: 129-33.
Block, N. 1981. Imagery. Cambridge, Mass.: MIT Press.
Block, N. 1981a. "What Is the Issue?" In Block 1981.
Block, N. 1981b. Readings in the Philosophy of Psychology, vol. 2.
Cambridge, Mass.: Harvard University Press.
Block, N. 1983. "Mental Pictures and Cognitive Science." In Lycan
1990. Casey, E. 1971. "Imagination: Imagining and the Image."
Philosophy and Phenomenological Research 31: 475-90.
Chalmers, D. 2002. "Does Conceivability Entail Possibility?"
Imagination, Conceivability, and Possibility, edited by T. Gendler and
J. Hawthorne. Oxford: Oxford University Press.
Currie, G. 1995. "Visual Imagery as the Simulation of Vision." Mind
and Language 10: 25-44.
Dennett, D. 1969. "The Nature of Images and the Introspective Trap."
In Block 1981.
Dennett, D. 1979. "Two Approaches to Mental Images." In Block 1981.
Descartes, R. 1642/1984. "Meditations on First Philosophy." In The
Philosophical Writings of Descartes, vol. 2, edited by J. Cottingham
et al. Cambridge: Cambridge University Press.
Finke, R.A., and Shepard, R.N. 1986. "Visual Function of Mental
Imagery." In Handbook of Perception and Human Performance, edited by
K.R. Boff, L. Kaufman, and J.P. Thomas. Chichester: John Wiley & Sons
(1986).
Flew, A. 1953. "Images, Supposing, and Imagining." Philosophy 28: 246-254.
Fodor, J. 1975. "Imagistic Representation." In Block 1981.
Hamlyn, D.W. 1994. "Imagination." In A Companion to the Philosophy of
Mind, edited by Samuel Guttenplan. Oxford: Blackwell Publishers
(1994): 361-66.
Hannay, A. 1971. Mental Images: A Defence. London: George Allen and Urwin, Ltd.
Hart, W.D. 1988. The Engines of the Soul. Cambridge: Cambridge University Press.
Heil, J. 1998. Philosophy of Mind. New York: Routledge.
Hobbes, T. 1651/1968. Leviathan. London: Penguin Books.
Hopkins, R. 1995. "Explaining Depiction." Philosophical Review 104: 425-55.
Hume, D. 1739/1969. A Treatise of Human Nature. Edited by E.C.
Mossner. London: Penguin Books.
Ishiguro, H. 1967. "Imagination." Proceedings of the Aristotelian
Society, Supplementary 41: 37-56.
Kind, A. 2001. "Putting the Image Back in Imagination," Philosophy and
Phenomenological Research 62: 85-109.
Kind, A. 2002 (unpublished). "Imagination and Possibility."
Kosslyn, S.M. 1973. "Scanning Visual Images: Some Structural
Implications." Perception and Psychophysics 14: 90-94.
Kosslyn, S.M., and Pomerantz, J.R. 1977. "Imagery, Propositions, and
the Form of Internal Representations." Cognitive Psychology 9: 52-76.
Kosslyn, S.M. 1980. Image and Mind. Cambridge, Mass.: Harvard University Press.
Kosslyn, S.M. 1993. Image and Brain: The Resolution of the Imagery
Debate. Cambridge, Mass.: Harvard University Press.
Kosslyn, S.M., and Osherson, D.N. 1995. Visual Cognition, An
Invitation to Cognitive Science, vol. 2. Cambridge, Mass.: The MIT
Press.
Levine, D., Warach, J., and Farah, M. 1985. "Two Visual Systems in
Mental Imagery." Neurology 35: 1011-18.
Lycan, W.G. 1990. Mind and Cognition. Cambridge, Mass.: Basil Blackwell.
Lyons, W. 1984. "The Tiger and His Stripes." Analysis 44: 93-93.
Lyons, W. 1986. "'Introspection' as the Replay of Perception." The
Disappearance of Introspection. Cambridge, Mass.: MIT Press/Bradford
Books.
Nagel, T. 1974. "What Is It Like To Be a Bat?" Philosophical Review 83
(4): 435-50.
Peacocke, C. 1985. "Imagination, Experience and Possibility: a
Berkeleian View Defended." In Essays on Berkeley, edited by J. Foster
and H. Robinson. Oxford: Clarendon Press (1985): 19-35.
Perky, C.W. 1910. "An Experimental Study of Imagination." American
Journal of Psychology 21: 422-52.
Russow, L.M. 1978. "Some Recent Work on Imagination." American
Philosophical Quarterly 15 (1): 57-66.
Pinker, S. 1997. How the Mind Works. New York: Norton.
Pylyshyn, Z. 1973. "What the Mind's Eye Tells the Mind's Brain—A
Critique of Mental Imagery." Psychological Bulletin 80:1-24.
Pylyshyn, Z. 1978. "Imagery and Artificial Intelligence." In
Perception and Cognition: Issues in the Foundation of Psychology,
edited by C. Wade Savage. Minneapolis: University of Minnesota Press
(1978): 19-56.
Reynolds, S.L. 1989. "Imagining Oneself To Be Another." Nous 23: 615-33.
Ryle, G. 1949. "Imagination." The Concept of Mind. London: Hutchison & Company.
Schwitzgebel, E. 2002. "How Well Do We Know Our Own Conscious
Experience? The Case of Imagery." Journal of Consciousness Studies 9:
35-53.
Scruton, R. 1982. Art and Imagination. London: Routledge.
Seddon, G. 1972. "Logical Possibility." Mind 81: 481-94.
Shepard, R. N., and Metzler, J. 1971. "Mental Rotation of
Three-Dimensional Objects." Science 171: 701-03.
Shepard, R.N., and Cooper, L. 1982. Mental Images and Their
Transformations. Cambridge, Mass.: MIT Press/Bradford Books.
Shorter, J.M. 1952. "Imagination." Mind 61: 528-42.
Sterelny, K. 1986. "The Imagery Debate."
Tidman, Paul. 1994. "Conceivability as a Test for Possibility."
American Philosophical Quarterly 31: 297-309.
Tipton, I. 1987. "Berkeley's Imagination." In Essays on the Philosophy
of George Berkeley, edited by E. Sosa. Dordrecht: D. Reidel Publishing
Company (1987).
Tye, M. 1994. "Imagery." In A Companion to the Philosophy of Mind,
edited by Samuel Guttenplan. Oxford: Blackwell Publishers (1994):
355-61.
Tye, M. 1991. The Imagery Debate. Cambridge, Mass.: MIT Press.
Tye, M. 1995. Ten Problems of Consciousness. Cambridge, Mass.: MIT Press.
Walton, K. 1990. Mimesis as Make Believe. Cambridge, Mass.: Harvard
University Press.
White, A. 1990. The Language of Imagination. Cambridge, Mass.: Basil Blackwell.
Williams, B. 1968. "Imagination and the Self." Problems of the Self.
Cambridge: Cambridge University Press.
Wittgenstein, L. 1953. Philosophical Investigations. New York:
Macmillan Publishing Co.
Vendler, Z. 1984. The Matter of Minds. Oxford: Clarendon Press.
Yablo, S. 1993. "Is Conceivability a Guide to Possibility?" Philosophy
and Phenomenological Research 53 (1): 1-42.
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