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1. Introduction
The aim of this section is to sketch out the claim that the traditional story1 of how we
acquire modal knowledge—the conceivability story—is (or can be seen as) figured on a
perceptual model. That is, the conceivability story of modal knowledge and a representationalist,
or indirect, story of perceptual knowledge share important formal parallels. Broadly, I will
highlight three of these parallels: the mind-world gap; imaginability as perceivability; and error.
By drawing out these parallels between these stories of perceptual and modal knowledge, I
intend to establish the grounds for a comparative examination of skepticism about modal and
perceptual knowledge.
The particular picture of perceptual knowledge that we will consider can broadly be
labeled as a ‘representationalist,’ or indirect, picture.2 The basic idea of representationalism (as it
is being used here) is that a perceptual agent is directly acquainted with a representation, or
‘image’, of an object or state of affairs. As Russell elegantly describes the view: “what we
directly see and feel is merely ‘appearance,’ which we believe to be a sign of some ‘reality’
behind.”3
The view can also be described as an ‘indirect’ story of perception, because of the
mediate relationship between the perceptual agent and external world. The perceptual agent is
I will use terms such as ‘story’ and ‘picture’ to signal that I do not intend to offer a
complete theory of either modal or perceptual knowledge, and to distance myself from a
scientistic conceptualization of philosophical practice (which would employ phrases like ‘a
theory of perceptual knowledge’).
2 One with some background in the philosophy of perception will notice that I elide (at
least) two distinct views: Russellian sense-data ‘theory’ and more contemporary
representationalist views. [At this stage in the project,] I do not think that the distinctions
between these views are crucial for our purposes, and so would unnecessarily complicate
the project.
3 The Problems of Philosophy (2004/1912), 7
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directly acquainted with (has direct epistemic access to) a representational content that
(typically) stands in an intentional relationship to a mind-independent object (i.e.: my
representation of a chair is about some chair in the world). That is, the agent’s epistemic
relationship to the external world is mediated by the representation in such a way that the agent
acquires knowledge of the external world by inferring its status from what her representation
presents as being the case.
On a conceivability story of modal knowledge, we are directly acquainted with an
imagined scenario about which we make a judgment. By conceiving such-and-such, we ‘form a
picture’ of some state of affairs, and judge whether some proposition obtains in our picture. For
example, I might imagine someone falling on an icy sidewalk in Chicago in the winter, and judge
that she slipped. From this scenario and the judgment we make about it, we then infer the
possibility of the proposition judged to obtain in the imagined scenario, where we (typically)
assume this possibility to be a mind-independent modal fact.
2. Mind-World Gap
This initial sketch gestures towards the first parallel between perception and conception:
the mind-world gap. Both pictures offer two domains of entities: a set of ‘internal’ entities—the
representational contents and imagined scenario—on the one hand, and a set of ‘external’
entities—the mind-independent objects or modal facts—on the other. On both pictures, we try to
‘link up’ the internal entities with the external; we say that we have knowledge of the external
entities when they link up with the internal entities in the right way. (In the case of perception,
we call the proper linking up a veridical perception, where the representational content depicts
the external world object ‘as it is.’)
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Moreover, the introduction of two separate domains of entities implies the possibility of
their incongruence, where the internal entities fail to match up with the external entities in the
right way. A representation of a chair, for example, could depict it as black, while the actual
chair is dark grey; an imagined scenario could represent Hesperus as not identical to Phosphorus,
even though Hesperus is necessarily identical to Phosphorus (both are Venus). Ordinarily, we
describe cases of this sort of incongruence, where we make a judgment about the external based
on what is represented to us internally, as ‘error’.
This basic shared formal characteristic of a mind-world gap, then, forms the basis for one
of the other parallels that I will emphasize: the possibility of error in our modal and perceptual
judgments. The mind-world gap also contributes to the link between imaginability and
perceivability, as the formal parallel between the conception and perception pictures we have
sketched out—that both have an internal component that typically corresponds to an external
component—opens up the possibility that the analogy between conception and perception is
more intimate. In essence, then, the rest of this section can be seen as an elaboration on the
observation that both conception and perception share a gap between the mind and world.
Before proceeding upon this elaboration, I would like to comment briefly on one
metaphysical issue lurking in the background: the assumption that some mind-independent
object or fact (typically) corresponds to our perceptual and modal representations (i.e.: that there
is something ‘in the world’ that matches up to what is ‘in the head’). Russell, in The Problems of
Philosophy, acknowledges that a sense-data story of perceptual knowledge does not necessarily
imply the existence of mind-independent objects—a philosopher could (prima facie) coherently
adopt the internal aspect of the sense-data picture without maintaining the external aspect. That
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is, one could say that the only real objects are “minds and their thoughts and feelings” (6), given
that we are directly acquainted only with representations (purportedly) of the external world.
Now, Russell himself (and most representationalists generally), do not adopt such a
position—they are realists in the sense that they maintain that there are in fact mind-independent
objects that stand in intentional relations to mental representations. Typically, one employs an
inference to the best explanation to achieve this result: the best explanation for the systematic
coherence and intentional properties of our internal representations is that they are caused by
external world objects that share properties of what is represented.
The relevant observation is that a similar anti-realist position seems possible for our
picture of conception: it seems (prima facie) coherent to maintain that we are directly acquainted
with imagined scenarios internally that fail to link up in any way with mind-independent facts of
possibility. That is, it seems possible to hold that there are no modal facts, but only conceivable
scenarios.4
The prime focus of this paper is not metaphysical, so I do not want to dwell for too long
on issues of modal factualism (that there are mind-independent modal facts). In particular, I do
not want to get into deep issues into the ontology of modal facts (whether we take possible words
to be equally ‘real,’ in some sense, to the actual world5). For our purposes, we need a only a
relatively thin sense of ‘modal fact:’ something mind-independent that makes our modal claims
(e.g.: That it is possible for the Philadelphia Phillies to win the World Series next year) true.
That this claim contains a modal operator perhaps immediately speaks against the
plausibility of this kind of view. I’ll assume for the moment that we can give an ‘epistemic’
reading of the claim (where ‘possible’ roughly means that our current epistemic position
cannot rule modal anti-factualism out), rather than a metaphysical reading. Metaphysical
modal facts, which are much better candidates for mind-independence than epistemic
modal facts, are the ones we are after here.
5 A primary proponent of this position is David Lewis [need citation]
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Given this relatively low threshold, then, the following argument seems to suffice: We
take our beliefs about modal claims to be true or false: my belief that the Philadelphia Phillies
could win the World Series next year is something that the question of true-conditions arises for
(in this case, we’d probably say that my belief is true, especially if we take ‘could’ in a really
weak (metaphysical or logical) sense of possibility). Now, in order for this belief to be true or
false, we need something to make it so: that is, we need a truth-maker for the claim. What makes
my belief that the Philadelphia Phillies could win the World Series true? It seems that the best
candidate is that it is, in fact, the case that the Philadelphia Phillies could win the World Series
next year! And what would make my belief that the Philadelphia Phillies could win the World
Series next year false? The best candidate here seems to be that it is, in fact, impossible that the
Philadelphia Phillies will win the World Series next year. That is, the truth-conditions of beliefs
about modal claims depend on facts of this form. In this way, we seem to at least give prima
facie grounds for accepting that there is a ‘world’ corresponding to our mental representations of
modal claims—just as we have good grounds for accepting that there is an external world
corresponding to our mental representations about perceptional knowledge.6
4. Imainability as Perceivability
With this preliminary work done to motivate modal factualism—thus affirming that both
our picture of conception and perception have a ‘world’ side on in their respective mind-world
gaps—I will now proceed to draw out further parallels between conception and a
Of course, the point here is not that we have firmly established the existence of mindindependent modal facts, in such a way to render our position impervious to radical
skeptical concerns about this. Rather, the point is simply that the existence of mindindependent modal facts is a natural, intuitive aspect of the picture of modal knowledge
we’re adopting here.
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representationalist picture of perception. Let’s begin with the link between imaginability and
perceivability.7
A common claim that one finds in the conceivability literature is that imagination (the
concrete cognitive process by which one conceives p8) is an ‘offline analogue’ of perceptual
processes. A few examples of this phenomenon:
If we regard the shepherd’s updating of his beliefs [that if the sheep have broken out of
the pen and disappeared, then they have gone down to the river] in the first case [where
he is told, or perceives, that the sheep have broken out of the pen] as an online process,
then we can regard his evaluation of the condition in the second case [where he
imagines the sheep breaking out of the pen and going down to the river] as the
corresponding offline process. If he accepted the conditional on the basis of an
imaginative exercise… then that imaginative exercise is the offline analogue of online
updating. (Williamson, Knowing by Imagining, 10)
…when you conjure up an image of w [a possible world, or a scenario that is a part of a
possible world], you are simulating the activity of really looking at it. Simulating
looking is not a distinct process, but the usual process running ‘off-line.’ Knowledge
gained by internal looking is not a priori because it is acquired through the exercise of a
perceptual faculty rather than a cognitive one. (Yablo, “Coulda, Woulda, Shoulda,”
458).
A terminological issue that I will need to sort out: the relationship of the terms
‘conception’ and ‘imagination.’ (The problem is that the use of these terms is not standard
across the literature.)
8 Conceives that p? I’m not sure which is the better formulation.
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We also find a similar idea in early modern discussions of conceivability, such as Descartes’
“clear and distinction perceptions,” and Hume:
“It is an established maxim in metaphysics, that whatever the mind clearly conceives,
includes the idea of possible existence, or in other words, that nothing we imagine is
absolutely impossible. We can form the idea of a golden mountain, and from thence
conclude that such a mountain my actually exist. We can form no idea of a mountain
without a valley, and therefore regard it as impossible.” (Treatise on Human Nature)
There is a good deal going on in Hume’s ‘established maxim—most centrally the claim that
conceivability (imaginability) implies possibility. What is especially relevant for our
purposes, however, is that Hume describes the imaginative process as one on which we form
an idea of an object, where ‘ideas’ are ultimately derived from ‘impressions,’ which are
provided to a subject through perception. Since the difference between impressions and
ideas “consists in the degrees of force and liveliness, with which they strike upon the mind,
and make their way into our thought or consciousness,” it seems that Hume is describing a
phenomenological similarity of imagination and perception.
This talk of imagination as an ‘off-line perceptual process’ seems to imply that when
we imagine, we put ourselves into a state analogous to a possible perceptual state. That is, to
imagine is to put oneself in an ‘as if perceiving’ state. We find confirmation of this
implication in Yablo:
I take the idea to be that conceiving [imagining]9 is in a certain way analogous to
perceiving. Just as someone who perceives that p enjoys the appearance that p is true,
whoever find p conceivable enjoys something worth describing as the appearance that it
Yablo seems to be a primary exemplar of ‘imagination as the concrete process of
conceiving’ terminology.
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is possible. In slogan form: conceiving involves the appearance of possibility. (“Is
Conceivability a Guide to Possibility,” 5)
Thus, we arrive at the ‘imaginability-perceivability’ parallel: to imagine that p is of a
phenomenological kind with perceiving that p—both involve an appearance of something being
the case, and, moreover, an instance of imagination is a possible instance of perceiving. To
imagine a chair is to (roughly) be in a state as if one is perceiving a chair.
I’d like to address a couple of problems with the imaginability-perceivability parallel.
Conceivability outstrips imaginability: An observation that goes at least as far back as
Descartes is that we conceive of things that we cannot ‘clearly and distinctly perceive’ by means
of the imagination. (Remember, here we are restricting our use of ‘imagination’ to a process in
which one forms a mental image,10 in order to maintain the tight imaginability-perceivability
parallel (imagination as ‘as if perception’).) For example, “if I want to think about a chiliagon, I
certainly understand that it is a figure consisting of a thousand sides… yet I do not image those
thousand sides… as if they were present” (Meditation Six, 40 in the Ariew and Cress
translation). I could not discern the distinction between a thousand sided and ten thousand sided
object by means of ‘as if perception’ (they would both look like circles), but I can obviously
comprehend that the two are distinct. This seems to establish that not all conceptions are
imaginings, in the narrow sense of the latter: we can conceive without imagining.
In the context of our particular discussion, one might respond to the Cartesian worry in
the following way: I can nevertheless imagine myself standing in a perceptual relation to a
thousand sided object, even if the qualitative character of this perceptual relation is
indistinguishable from a possible perceptual relation to a ten thousand sided object. At most,
Or, to include non-visual sensory modalities, a mental analogue of a possible sensory
experience.
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Descartes undermines imaginability as a sufficient condition for modal-knowledge-providing
conception. It still may be necessary for me to imagine myself as if perceiving a thousand sided
object, and then introduce a non-imagery element to make clear that I am in fact conceiving of a
chiliagon.
We can undermine this response by introducing an example that precludes the possibility
of imagining in the ‘as if perceiving’ sense at all. I can conceive of a distant star, so distant that I
could never stand in an observational relation to it. That is, I am conceiving of the star as distant,
where ‘distant’ precludes the possibility of perceiving the star. In order to conceive of this star, I
absolutely cannot imagine the star at all; if I formed a picture of the star, I would not be
imagining it as distant in the specified sense. But it would be quite odd to say that I cannot
conceive of this star at all—it surely seems that I am talking sensibly about the star as distant,
and this seems to imply that I can, in some sense, conceive of the star as distant.
Even where imagination possible, not necessary: Even in cases where I could stand in a
perceptual relation to the relevant object or scenario, I need not, and often do not, form a finegrained analogue of a perceptual state. Yablo provides the materials for this objection with his
example of conceiving of a tiger behind a curtain:
When I imagine a tiger I imagine it as possessed of some determinate striping—what
else?—but there need be no determinate striping such that I imagine my tiger as striped
like that; the content of my imagining is satisfiable by variously striped tigers, but not
by tigers of no determinate striping. Likewise for situations: even if there is much about
my tiger-situation that I leave unspecified as irrelevant to the proposition at hand (e.g.,
the distance from the tiger’s nose to the curtain), still I think of these things as fully
definite in the situation itself. (“Is Conceivability a Guide to Possibility,” 28).
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Or, as a more general formulation: we can image an object as determinate without
determinately imagining it (29).11 This seems to sever a tight link between imaginability and
perceivability, where we describe an instance of imagining as an ‘as if perception,’ because a
particular perception would present the object determinately, not merely as determinate (that is,
with particular specified properties, rather than as having some unspecified, but nevertheless
determinate, properties).
In essence, the two objections are that:
1. There are instances of conceiving that are impossible imaginings.
2. Even in cases of conceivings as possible imaginings, we need not actually imagine what
we are conceiving (where imagine is understood as ‘as if perception’).
Aside: This point about imagining an object merely as determinate relates to a problem
with an objection offered by Dennett to Jackson’s Knowledge Argument (“Epiphenomenal
Qualia?”, Consciousness Explained, 399-400). We can formulate Dennett’s objection in the
following way: The scenario on which the Knowledge Argument rests requires that we
imagine an individual who has knowledge of all the neurological facts (or at least those
relevant to vision). But this set of facts is preposterously immense! It is simply beyond our
cognitive capacities to imagine an individual who has knowledge of ‘all the neurological
facts.’ But since this is precisely what the scenario demands, it is beyond our cognitive
capacities to imagine the scenario from which the central intuition of the Knowledge
Argument is elicited. Thus, whatever intuitions we purportedly derive from the scenario
are not reliable.
Dennett, in effect, demands that the Mary argument must be imagined
determinately, rather than as determinate: we must not only imagine that Mary knows all
the relevant neurological facts about color vision, but also determinately imagine those
facts ourselves. This standard, however, seems absolutely too onerous. For example, I
might arrive at the conclusion that it is possible for the Philadelphia Phillies to win the
World Series next year by imagining a season at which they finish at the top of the division,
and the proceed through the playoffs, to finally win four games in the Series against an
American League team. I do not, however, specify the results of each and every game that
the Phillies play in that season, much less each and every play comprising each and every
game. Rather, I only imagine that there are such determinate results and plays. Doing the
latter would be to imagine the scenario determinately, while the former would be to
imagine it as determinate. And we, in fact, would imagine the situation as determinate in
this case—and still take ourselves to have arrived at knowledge of a modal fact at the end
of our imagining!
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These objections show that the parallel between conception and perception should not be
stressed too far. Still, I think, we can go some ways towards mitigating them.
Actually imagining (in the sense of ‘as if perceiving’) often strengthens of confidence in
the genuine conceivability of what we are claiming to conceive. That is, being able to
determinately imagine an object or scenario provides grounds for believing that we are in fact
grasping a coherent scenario, instead of merely purporting to grasp a confused, incoherent one.
For example, if I were to claim that I could conceive of an object being red and green all over, I
should become wary of this claim when I realize that I cannot form a mental picture of such an
object; in contrast, I become more confident that I can conceive of a golden mountain when I
form a mental picture of it.
This observation can be applied to the examples in the objections above. In the distant
star case, I might start by imagining a star with determinate properties (of such-and-such a size
and color), and then proceed to ‘zoom out’ until I no longer stand in a perceptual relation to that
star. I acknowledge, as Yablo points out, that my claim of conceiving of a star as distant does not
rely on the particular properties I apply to it in my imagination, but I nevertheless gain
confidence in my assertion by making a start at determinately imagining the star.
Likewise, in the case of conceiving of a tiger behind a curtain, I can verify that I really
am conceiving of this by, under pretense, introducing some determinate properties to the
situation I am imagining—such as imagining the tiger as a Bengal tiger, the curtains as beige,
etc.
When someone instructs us to imagine a tiger, or any perceivable scenario, we typically
make a start at a fine-grained picture (which would satisfy an ‘as if perception’ condition). We
do this acknowledging that many of the particular properties we are building into our picture are
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not relevant in their specific determinate presentation. We rarely, if ever, imagine the whole finegrained scenario—we proceed until we are satisfied that we could imagine the whole picture
(given time, energy, and perhaps sufficient powers of attention).12
This point seems to extend to instance of conception employed in philosophical practice.
In complex thought experiments, we lend credence to those scenarios that we can satisfactorily
imagine (get a good enough picture of), and are at least initially wary of those that we cannot do
this for. This helps to explain why many (pace Dennett) find Jackson’s Knowledge Argument
initially compelling: we can make a good start at imaging Mary in a black and white room,
learning all there is to know about neuroscience, and then eventually leaving the room and seeing
a red rose. In contrast, split-brain thought experiments, such as those found in Tye (Ten
Problems of Consciousness, 1995, 78-84), often do not deliver determinate intuitions (about, say,
whether two distinct persons can feel a numerically identical pain).13 It is no coindence, I think,
that it is very hard to form a picture of what is occurring in such thought experiments (such as
the idea that halves of two brains are somehow ‘zippered together’ (Tye, 79)).
It doesn’t seem to me that the intuitions that we have about the epistemic quality (i.e.: the
degree of credence we should lend in intuitions derived from them) of these thought experiments
merely rests upon the idea that more complex thought experiments are prone to error—Mary in a
black and white room, knowing all the neuroscience facts relevant to vision is surely not a
‘simple’ thing to imagine! Rather, when we fail to form a picture of the thought experiment—
If we talk of one conceiving a possible world, rather than just a scenario, it is almost
always the case that we do not determinately imagine every particular property and object
that obtains in that world.
13 Tye himself acknowledges the indeterminate intuitions delivered by split brain scenarios
(81). [I will flesh this claim out more in future work if it seems feasible.]
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when we are unable to imagine ‘as if perceiving’— we are, ceteris paribus, wary that there is
nothing coherent being expressed by the scenario.
So, while the objections above underscore limits on the parallels between perception and
conception, the link between imaginability and perceivability seems to do significant work in our
actual modal reasoning.
5. Error
One merit of an indirect/representation picture of perception is that it gives us a clear
analysis of error: perceptual error occurs when the representational content an agent is
acquainted with fails to accord with the properties of the perceived object (illusion), or when the
representation fails to correspond to any mind-independent object at all (hallucination).
We arrive at this error because of the mind world gap: we have two domains of objects
(representations/sense-data/impressions and mind-independent objects), and so have the
possibility of the domains failing to ‘link up’ in the right way. Our perceptual picture thus serves
as a paradigm for particular varieties of error (illusion and hallucination), where ‘what’s in the
head fails to match up with what’s outside.’
We should expect, then, that an analogous story of perception (one that shares this mindworld gap) admits the possibility of errors of analogous sorts. In particular, we should expect to
identify a type of modal error analogous to hallucination, and one analogous to illusion. I will
now offer some preliminary remarks on how we might see a couple of familiar varieties of modal
error in these analogous relationships.
Hallucination: The hallucinatory analogue for modal error would be one on which there
is no mind-independent modal fact that corresponds to a scenario conceived.
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Yablo’s model of modal error (“Is Conceivability a Guide to Possibility,” 33-36) seems
to fit into this role. On this model:
1. I find p conceivable, but p is impossible.
2. Some other proposition q, is the case.
3. If q is the case, then p is impossible.
4. I either do not know (or deny) (2), or do not know (or deny) (3).
(4) explains why (1) is the case. For example, imagine that someone finds it metaphysically
possible that Hesperus is not identical to Phosphorus.14 Such a person does not know that
‘Hesperus’ and ‘Phosphorus’ are rigid designators with the same actual world referent (Venus),15
or she does not know that identities between rigid designators are, if true, necessarily true.16
In such a case, since it is metaphysically impossible that Hesperus is not identical to
Phosphorus—there is no metaphysically possible world in which this proposition obtains—there
is no mind-independent modal fact that corresponds to what is ‘conceived;’ just as there is no
mind-independent object corresponding to what is being ‘perceived’17 in a case of perceptual
hallucination.
Illusion: The illusionary analogue for modal error would be one on which the
representational contents fail to accord with the corresponding mind-independent modal fact in
the right way. That is, I misconceive of (or misreport on) a particular modal fact—as I might
misperceive a dark grey chair as a black chair in the wrong lighting.
We assume that this is not a case of misreporting, or mistaking an epistemic possibility
for a metaphysical one—these situations will be addressed in the illusion analogue.
15 The first disjunct of (4)
16 The second disjunct of (4)
17 I put ‘conceive’ and ‘perceive’ in scare quotes here to express an inclination towards
taking conception and perception as factive. Admittedly, I have not been consistent in this
usage throughout the section.
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Kripke’s discussion of epistemic possibility in Naming and Necessity (103-104; 140-144)
seems like a good candidate for this role.
I report that I can conceive of a scenario in which Hesperus is not identical to
Phosphorus. I am apprised of the facts that ‘Hesperus’ and ‘Phosphorus’ are co-referential rigid
designators, and that true identities of rigid designators are necessarily true. Yet I claim that I can
still conceive of Hesperus and Phosphorus as non-identical. Kripke’s diagnosis of such a
circumstance is that one is mistaking an epistemic possibility for a metaphysical possibility.18 In
particular, Kripke says that one is mistaking a “qualitatively identical epistemic situation” (104)
for a scenario in which Hesperus is in fact not identical to Phosphorus. Roughly, the qualitatively
identical epistemic situation is one on which an observer sees the last ‘star’ in the evening,
labeling it ‘Hesperus,’ and sees the first ‘star’ in the morning, labeling it ‘Phosphorus,’ but where
the evening star turns out to be, say, Venus, and the morning star, Mars. This is not a situation in
which we are conceiving of Hesperus as not identical to Phosphorus, because the names are not
being used in the same way—the imagined observer is not, in fact, speaking English!
I said just above that this is often described as a situation in which one mistakes an
epistemic possibility for a metaphysical one. This description might be interpreted as saying that
one has only got onto an epistemically possible world, and, since the relationship between
epistemic modality and metaphysical modality is asymmetric (some worlds in the first domain
are not in the second, and vice versa), it is possible that this epistemically possible world does
not map onto a metaphysically possible world. Moreover, in this case, it doesn’t!
I want to resist this interpretation of Kripke’s remarks, as I think it mischaracterizes the
error that occurs. Part of my motivation for resisting this is that, if the epistemic possibility
At least, this is how his diagnosis is traditionally formulated. I diverge from this
formulation to some degree below.
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interpretation went through, it seems that we are no longer talking about a case of illusion, but
rather hallucination, as there is no corresponding mind-independent fact to my (mis)conception.
(Epistemic possibilities are surely mind-dependent.)
But there are independent grounds for resisting this interpretation. The scenario that
Kripke describes to diagnose our intuitions about the conceivability of the non-identity of
Hesperus and Phorphorus itself does seem to be metaphysically possible: it is surely
metaphysically possible that Venus could appear as the last ‘star’ in the evening, and Mars as the
first in the morning, and that an observer could use ‘Hesperus’ as a label for the first, and
‘Phosphorus’ as a label for the second. Kripke is correcting us by pointing out that this
metaphysically possible world is simply not a world on which (our!) Hesperus is not identical to
(our!) Phosphorus.
If this interpretation of Kripke is correct, we do seem to have an analogue to illusion at
hand. A subject conceives of a scenario that has a corresponding modal fact (possible world), but
the subject mistakes this possible world for one on which Hesperus is not identical to
Phosphorus. In a sense, she is attributing properties to the possible world that do not accord with
the actual properties of that world—an illusion type error.
I’ll conclude my remarks on illusion with one complication: We typically say in Kripketype errors of this sort that the subject is misreporting on what she is in fact conceiving, rather
than that the scenario she has in mind is mistaken. That is, we typically give up first-person
authority instead of claiming that the representational contents are ‘off.’ This is typically the
other way round in the case of perceptual illusion: when someone says that she sees a black chair
where there is in fact a dark grey one, we typically say that her representational contents are
‘off’—we typically tell her to look more close at the chair, not her representation of it.
Philip Yaure
The Analogy Between Perception and Conception
9/23/2013
17
Draft: DO NOT CIRCULATE
I hope to have made plausible a parallel between types of modal and perceptual error,
which would contribute to the analogy between perception and conception. However, I will
conclude by noting that even if the parallels have been stretched to far here, there is still an
essential point that may carry through: both the perceptual and conceptual pictures we are
adopting make room for error by opening up a gap between representational contents and mindindependent objects or facts. And it is in this gap that shared varieties of skepticism will fester.