SUSANNA SIEGEL
INDISCRIMINABILITY
AND THE PHENOMENAL
In Philosophical Studies volume 120, 90-112
In “The Limits
of Self-Awareness” (this volume) , M.G.F. Martin characterizes disjunctivism about perceptual experience as follows:
[S]tatements about how things appear to a perceiver [are] equivalent to statements of a disjunction that either one is perceiving such and such or one is suffering an illusion (or hallucination) . . . such statements are not to be viewed as introducing a report of a distinctive mental event or state common to these various disjoint situations. (p. 1)
The disjunctive
theory stands opposed to the common-kind
theory, according to which there are pairs of genuine
perceptions
and mere seemings to
perceive that have some fundamental kind of
mental state in
common.
The issue
between disjunctivism and the common-kind theory concerns the status of being indiscriminable from a veridical perception. Suppose, for example, that I see a green
cube, and my experience is veridical – no illusion is involved. An example of
the sort of indiscriminability property whose status is at issue is the
property of being indiscriminable from my experience of seeing the green cube.1
As Martin sees
it, the common-kind theorist and
the disjunctivist
have three bones of contention. First, the common-kind theorist affirms, while
the disjunctivist denies, that for any event indiscriminable from a (specific)
veridical perception,
there is a robust
property in virtue of which that event is so
indiscriminable.
According to the common-kind theory, once we
fix on an
indiscriminability property – for instance, the property of
being
indiscriminable from my seeing the green cube – any event
that has this property
has it in virtue of having some
robust property
or other, so the
indiscriminability property isn’t fundamental.
This brings us
to the second bone of contention. As Martin
characterizes it,
the common-kind theory goes further than merely
denying that
indiscrminability from veridical perception is a
brute fact: in
addition, any two events with the same (specific)
indiscriminability
property have it in virtue of having the same
(specific) robust
property. This entails that there is a common
kind:
a kind that
hallucinations and perceptions share.
In contrast,
Martin denies that there is any fundamental kind
to which
hallucinations and perceptions both belong. According
to Martin’s version
of disjunctivism, some experiences – but only
some – are indiscriminable
from a (specific) veridical perception,
even when there is
no robust property they have in virtue of which
they are so
indiscriminable. This is Martin’s line on causally matching
hallucinations: hallucinations with the same proximate
causal antecedents
as veridical perceptions. Such hallucinations,
Martin holds, belong
to the fundamental kind: being indiscriminable
from a veridical
perception.
Other
experiences, Martin thinks, belong to this kind, but it
is not their
fundamental kind. Veridical perceptions are, naturally,
indiscriminable from
veridical perceptions; but they are so
indiscriminable,
Martin thinks, in virtue of having robust properties.
My veridical
perception of the green cube, for instance, Martin
thinks, is
indiscriminable from a veridical perception of the green
cube in virtue of
the perceptual relation that holds between the
perceiver (me), on
the one hand, and the cube and the properties of
it that appear to
me, on the other. Veridical perceptions belong to the
fundamental kind: being
veridical perceptions; whereas causally matching
hallucinations
belong to the fundamental kind: being
indiscriminable from a veridical perception.
So Martin
agrees with the common-kind theorist that there is
a common element
between causally-matching hallucinations and
the veridical
perceptions they causally match;2 but disagrees about
the depth and
significance of the commonality. For Martin, it goes
no deeper than the
indiscriminability property, and it does not
constitute the
fundamental kind to which both experiences belong.3
So far, I’ve
mentioned two of the three bones of contention
between the Martin’s
disjunctivism and the common-kind theory.
The first was that
the disjunctivist (of Martin’s stripe)4 allows, while
the common-kind
theorist denies, that being indiscriminable from a
(specific) veridical
perception can be a brute fact. The second is that
the common-kind
theorist allows, while the disjunctivist denies, that
for any paired
hallucination and perception that (in some intuitive
sense) seem the same
to the subject, there is a single mental state
had by both
experiences that constitutes their fundamental kind.
The third
disagreement concerns the concept of perceptual experience. Martin takes
indiscriminability from veridical perception to
be definitive of
perceptual experience: “being indiscriminable from
veridical
perception,” he writes, “is the most inclusive conception
we have of what
sensory experience is” (p. 22). Now, Martin takes
it that the
common-kind theorist will agree that for an event to so
much as count as a
perceptual experience, it has to be indiscriminable
from a veridical
perception. So they will agree, Martin thinks,
that it’s a
conceptual truth that sensory experiences are indiscriminable
from veridical
perceptions. The disagreement is supposed to
concern whether
anything else is conceptually true of sensory experience.
As Martin construes
his opponent, she says that something
else is: it is part
of the concept of perceptual experiences that they
instantiate mental
properties that realize, or underlie, indiscriminability
from veridical
perception. As to the metaphysical nature of
the common kind
property, there are the options made familiar by
the history of the
philosophy perception so far: candidates include
sense-data, being an
adverbial modification, having propositional
content of some
sort, and combinations thereof.
In what
follows, I will challenge both the assumption that
phenomenality and
indiscriminability from veridical perception are
as closely linked as
Martin thinks they are, and Martin’s defense of
disjunctivism.
Sections 1 and 2 criticize Martin’s claim that every
experience is
indiscriminable from a veridical perception: section 1
focuses on
veridicality; section 2 on indiscriminability. In section 3,
I turn to Martin’s
argument against the common-kind theory, which
is supposed to
motivate taking the disjunctivist conception of experience
as the default. In
section 4 I address a residual question related
to the apparent
intransitivity of looking the same with respect to hue.
I conclude the
discussion in section 5.5
1. VERIDICALITY
Both Martin’s
disjunctivism and the common-kind theory, as Martin understands it, are
supposed to endorse a strong link between the
notions of
phenomenality and indiscriminability from a veridical
perception. More
exactly, both positions are supposed to agree that
any event that
counts as a perceptual experience is indiscriminable
from a veridical
perception.
One might
question the claim that the phenomenal is quite
as closely linked to
indiscriminability from veridical
perception
as Martin suggests.
Consider, for example, a virtual-reality scene
made to look just
like what’s depicted in Escher’s drawing of
the impossible
staircase. There seems to be no possible veridical
perception from
which an experience of seeing such a scene is
indiscriminable. Yet
it seems to be a perfectly good specimen of
a perceptual
experience.6
A different
sort of example casts additional doubt on the claim
that any event that
counts as a perceptual experience is indiscriminable
from a veridical
perception. Suppose the following sort of
error theory of
color is correct: visual experience represents color
properties, but
nothing external is, or could in principle be colored.7
On this view, when
earlier I described my experience by saying that
I saw a green cube,
strictly speaking this was a misdescription: what
I saw was a cube,
and though it appeared green, there was no color
property had by the
cube that my experience even so much as falsely
represented.
If such an
error theory were correct, then there would not be any
veridical perception from which my experience of seeing
the green appearing cube is indiscriminable. Many philosophers would find
such a theory
implausible.8 But presumably its implausibility has
nothing to do with
miscategorizing the event of seeing the greenappearing
cube as an
experience. Like the events of seeing Escher
drawing, this event
seems a fine specimen of an experience; and,
crucially, its
status as fine specimen seems independent of whether
the error theory
described is correct.
I’ve been
questioning the claim that any event that counts
as a perceptual
experience is indiscriminable from a veridical
perception. As we’ve
seen, Martin’s disjunctivism includes an
even stronger claim
connecting phenomenality to indiscriminability, a claim concerning the very
concept of perceptual experiences:
In
fixing on our concept of perceptual experience, we seem to have no more
resources
than we need to pick out something indiscriminable from a veridical
perception.
(p. 11)9
Martin considers it
a conceptual truth about perceptual experiences
that they are
indiscriminable from veridical perception. If this were
right, then error
theorists of color would be conceptually
confused
about what
experience is. But whatever errors such theorists may
be making, they do
not seem to include conceptual confusion about
what to count as an
experience.
2. INDISCRIMINABILITY
So far, I’ve
criticized the idea that phenomenality is linked
to
indiscriminability from veridical
perception. I now want to
challenge the idea
that it is linked to any notion of indiscriminability.
As Martin thinks of
it, indiscriminability is a notion defined
in terms of
judgment. “To discriminate two things,” Martin writes,
“is judge them
non-identical” (p. 26). This suggests that when A
and B are indiscriminable
for a subject, the subject cannot tell them
apart in judgment. Saying no more than this leaves much unsettled
about what
indiscriminability is, and shortly we will consider two
ways to precisify
the notion. For the moment, what’s notable is that
Martin’s notions of discriminability and indiscriminability are cognitive notions.
As we saw
earlier, Martin takes the common-kind theorist to be
committed to the
claim that any event that counts as a perceptual
experience is
indiscriminable from a veridical perception.10 Let S
be a subject, and
let I* be a robust property of the sort that, by
the lights of the
common-kind theory, is supposed to bestow on
any event that has
it the property of being indiscriminable from a
veridical
perception. So fix on an indiscriminability property, such
as the property of
my seeing the green cube, and by the lights of
the common-kind
theory (as Martin construes it) there is a property
I* that
characterizes what it is like to have an experience with that
indiscriminability
property. In the hands of Martin’s common-kind
theorist, then, I*
is supposed to play two roles: first, it is supposed to
make any event that
has it indiscriminable from a veridical perception;
second, it is
supposed to characterize what the experience is like
for the subject.
Martin, then,
takes his opponent to accept the following:
Sufficiency claim:
If S’s experience has I*, then S’s
experience is
indiscriminable from a veridical perception.
What the Sufficiency
claim comes to depends on how the
notion of
indiscriminability is understood. I will now consider two
notions of
indiscriminability, and argue that on each way, someone
sympathetic to the
main thrust of the common-kind theory could
reasonably deny the
Sufficiency claim – though for different reasons
each time. Both
doubts come into focus by considering creatures
who have perceptual
experiences, yet lack the cognitive resources
to make judgments
about them. In addition, as we will see, the
possibility of this
sort of creature also threatens Martin’s positive
view that two
events’ being indiscriminable from the same veridical
perception suffices
for their being phenomenally the same.
I’ll call the
first notion of indiscriminability the positive
notion:11
Positive: X is
indiscriminable from Y by a subject S at
time t iff S is
disposed to judge on basis b that X = Y.
This notion of
indiscriminability has a parameter for the basis of
S’s disposition to
judge. The motivation for having such a parameter
is as follows.
Suppose that X and Y look totally different to S, but S
is disposed to judge
on the basis of consulting an unreliable oracle
that X = Y. Without
the parameter for the basis, by the positive
notion, X and Y
would count as indiscriminable for S. This seems
like the wrong
result. In any case, it seems clear that the basis Martin
has in mind is
“introspection and reflection”,12 so let
us put that in
for b.
Now, suppose
there were a creature who had I*, but who was
not equipped to form
any judgments at all, ergo was not disposed
to judge that she
was veridically perceiving. On the positive
account of
indiscriminability, the sufficiency claim would predict
that if such a
creature had a perceptual experience, then S would
be disposed to judge
on the basis of introspection and reflection
that S’s experience
is a veridical perception. For the sort of creature
imagined, this
prediction would be false.
Martin’s
construal of the common-kind theory, then, would be
too restrictive,
given the positive notion of indiscriminability. The
existence of
creatures who have perceptual experiences without
capacities for
judgment is compatible with there being pairs of
veridical perception
and causally-matching hallucination that share
a common mental
kind. So rejecting the Sufficiency claim does
not seem tantamount
to giving up on the central claim of the
common-kind theory
itself.
I’ve complained
that Martin shouldn’t attribute the Sufficiency
claim to the
common-kind theorist. In my complaint, I’ve assumed
that if some sort of
first-person access to what experiences are like
is required, this
access can take a form other than judgment. It is
a difficult question
how to understand the nature of such access,
once it’s stipulated
not to involve judgment. Perhaps there is a more
primitive form of
introspective access of some sort.
The same sort
of creature presents a different reason for a
common-kind theorist
to deny the Sufficiency claim, when that
claim is taken to
involve indiscriminability understood differently.
I’ll call the second
notion of indiscriminability, which is proposed
by
TimothyWilliamson, the double-negative
notion of indiscriminability:
Double-negative: X
is indiscriminable from Y by a
subject S at time t
iff S is not able at t to activate
knowledge that X =/=
Y.13
Using this notion of
indiscriminability, the Sufficiency claim
comes to this:
Sufficiency
claim-TW: If S’s experience has I*, then S
cannot activate
knowledge that having-I* is distinct from
having a veridical
perception.
With respect to the
sort of creature lacking cognitive equipment
of the sort needed
to form judgments, Sufficiency claim-TW
is trivial. For such
a creature, there will be no pair of perceptual
experiences such
that the creature can activate knowledge that they
are distinct from
one another. So all perceptual experiences of the
creature will count
as indiscriminable from one another.14 This
gives
the common-kind
theorist reason to reject the Sufficiency claim, on
the grounds that it
doesn’t capture anything important in their view.
The case of
creatures with perceptual experiences who lack
capacities for
judgment also suggests an objection to Martin’s
positive view that
being indiscriminable from the same
veridical
perception is
sufficient for two events’ being phenomenally the
same. Assuming
either notion of indiscriminability, all of the experiences
of such creatures
will count as the same, if indiscriminability
suffices for
sameness of experience.
Martin
considers and responds to this very worry. His response is
that the relevant
notion of discriminability is impersonal:
when
we turn to the experiences of sentient but unselfconscious creatures, to the
extent
that we do have a positive grip on the kinds of experience that they can
have,
and which can differ one from another, we also have a grip on how such
experience
would be discriminable through reflection or not . . . a dog might fail
to
discriminate one experience from another, making no judgment about them as
identical
or distinct at all, [but] that is not to say that we cannot judge, in ascribing
them
such experience, that there is an event which would or would not be judgably
different
from another experience. (p. 28)
If the claim here is
that two of the dog’s experiences are discriminable
by someone other than
the dog, that seems correct. But it does
not seem correct to
say that they are discriminable by
reflection, if
reflection is
supposed to be on the part of the subject whose states
are in question.
After all, by hypothesis it is not the dog doing the
reflecting, and it
is not clear what it would be for us to reflect on the
dog’s experiences,
without doing some empirical investigating of a
sort that the dog
would be incapable of carrying out. If the relevant
sort of
(in)discriminability is (in)discriminability for a subject on the
basis of that
subject’s reflection and introspection, then the appeal
to the impersonal
notion won’t work in this case.15
On another
reading, Martin’s response to the worry is that there
is a sense in which
some of the dog’s experiences are discriminable
from one another, to
the dog. But the notion of discriminability that
would make this
claim true could not be a cognitive notion. And as
we’ve seen, it is a
cognitive notion that is at work in Martin’s central
claims.
3. MARTIN’S OBJECTION TO THE
COMMON-KIND THEORY
So far, I’ve
been criticizing Martin’s views of the relation between
indiscriminability
and the phenomenal. These views form the background
to his argument for
disjunctivism. I now want to turn to that
argument itself.
Martin’s
defense of disjunctivism aims to show that the disjunctivist conception of
perceptual experience should be the default
conception. It
should be the default conception, Martin thinks,
because otherwise
one’s epistemological assumptions about the
mind will be very
weighty.16 The fact (as Martin sees it) that
the common-kind
theory is committed to such weighty epistemic
assumptions is the
main objection he raises against that theory.
This fact, in turn,
is the main reason given for why the disjunctivist
conception should be
the default. I will now examine this objection.
Martin gives
the objection in a passage that contrasts the
supposed “modesty”
of disjunctivism with the supposed “immodesty”
of the common-kind
theory. Disjunctivism is supposed to
be modest, because
it takes indiscriminability from a veridical
perception as
necessary and sufficient for an event to count as an
experience. The
common-kind theory, in contrast, is supposed to be
immodest, because it
takes as necessary and sufficient for an event
to be an experience
that it instantiate a robust property that realizes
the
indiscriminability from a veridical perception. In the first part of
the objection,
Martin considers how the common-kind view would
classify a situation
in which a subject was unable to discriminate
her situation from
one in which she was seeing a street scene, and
yet had no robust
property of the sort that the common-kind theory
takes to
characterize perceptual experience:
For
the immodest view in question this could not be a case of visual experience as
of
a street scene, while by modest lights that would be exactly what it is. . . . Now
surely
this result would surely be unfortunate for any immodest view, given our
initial
assumptions. For we supposed that reflection on experience offers support
to
a naïve realist construal of sensory experience. When one reflects on one’s
experience
it seems to one as if one is thereby presented with some experience-independent
elements of the scene before one as constituents of one’s experience
and
not merely as represented to one as in imagination. (p. 10)
There seem to be two
steps here that Martin thinks the common
kind theorist is
forced to take. The first step is that an event is
indiscriminable from
a veridical perception, just in case it seems
to the subject as if
she is “presented with experience-independent
elements of the
scene before her as constituents of her experience”.
This is supposed to
be an upshot of the initial assumption that reflection
on experience
supports a naïve realist construal of experience.
The second step is
that it seems to one as if one is presented with
such elements, just
in case one is having a perceptual experience
(perhaps a
hallucinatory one). And this seems plausible. Putting
these steps
together, being indiscriminable from veridical perception
suffices for being
an experience. As we’ve seen, Martin also thinks
there are grounds
(acceptable to disjunctivist and non-disjunctivist
alike) for the
converse – that all experiences are indiscriminable
from a veridical
perception. I raised some worries about that earlier,
but let us set them
aside here. Combining these commitments gives
us
(1)
I iff E,
where ‘I’ is for
indiscriminability from a veridical perception, and
‘E’ is for being a
perceptual experience, and (1) abbreviates “all
and only the events
indiscriminable from veridical perceptions are
experiences.”
This brings us
to the second part of the objection:
A
proponent of the immodest view can only hope to offer necessary as well as
sufficient
conditions for having an experience – and hence to explain the having
of
an experience in terms of its favored conditions – if it can ensure that
themodest
approach
and its favored form of immodesty coincide in the extension they give
the
concept of experience. (p. 11)
Here the relevant
part of the sentence is the first part, with its
assumption that the
common-kind theorist aims to give necessary as
well as sufficient
conditions for having an experience. The common kind
theory, recall,
takes it to be a conceptual truth about perceptual
experience that such
experiences have a certain robust property (the
exact metaphysical
nature of the property is left open – it could the
property of having
sense-data, or of having propositional contents of
sort, some
combination, etc.)Where this property is R (for ‘robust’),
the assumption comes
to this:
(2) E iff R,
or more exactly, all
and only the experiences have robust property
R.
In the passage
quoted, Martin suggests that the common-kind
theorist can accept
(2) only if she accepts (3):
(3) I iff R,
that is, all and
only the events indiscriminable from veridical perceptions
have the property R.
In embracing (1)–(3), the common-kind
theorist ensures
that it classifies as experiences all the same events
as the
disjunctivism-a-la-Martin does: as Martin puts it, she ensures
that the modest and
immodest approaches “coincide in the extension
they give the
concept of experience.”
The final part
of the objection connects (1)–(3) to a substantive
epistemic principle:
A
proponent of the immodest view can only hope to offer necessary as well as
sufficient
conditions for having an experience – and hence to explain the having
of
an experience in terms of its favored conditions – if it can ensure that the
modest
approach and its favored form of immodesty coincide in the extension
they
give the concept of experience. In turn, this coincidence of extension can by
guaranteed
only if the proponent of the immodest account embraces a substantive
epistemic
principle . . . one must assume that a subject
couldn’t but be in a position
to
discriminate a situation which lacked E1 . . . EN from one which possessed
them.
. . . A responsible subject who
wishes to determine how things are with him
or
herself through reflection must be, on this view, infallible in the answers
they
come
up with. They must not only correctly identify phenomenal properties of a
specific
sort when they are present, but also they cannot be misled into judging
them
present when they are not. (p. 11)
It is the
common-kind theorist’s commitment to (1)–(3) that
supposedly forces
her to accept the substantive epistemic principle,
which from now on I
will call Hefty.
Hefty:
A responsible subject who wishes determine how things are with him or
herself
through reflection must not only correctly identify phenomenal properties of a
specific sort when they are present, but also they cannot be misled into
judging them present when they are not.
The success of
Martin’s objection to the common-kind theory
(and, given the
dialectical context, his success in motivating
disjunctivism) hangs
on two things: first, whether a commitment to
Hefty really does
follow from (1)–(3); second, on how plausible or
implausible Hefty
is. I will consider the second issue first, and then
return to how
exactly the commitment to Hefty on the part of the
common-kind theorist
is supposed to arise.
In assessing
the plausibility of Hefty, a crucial interpretive question is what sorts of
properties E1 . . . EN, the “phenomenal properties of a specific
sort”, are meant to be. Either they are robust
properties that
characterize a specific type of veridical experience,
such as my seeing
the green cube; or else they are the robust general
properties, shared
by all such specific ones, such as the property of
having propositional
content, or being sense-data. Call these strong
and weak robust
properties, respectively.
Up until the
statement of Hefty, it seems clear that it is weak
robust properties
are at issue: notably, premises (2) and (3) concern
the property that
(by the lights of the common-kind theory) is
supposed to be necessary for having an experience at all. And it
is surely not
necessary for an event to count as a perceptual experience
that it have the
strong robust property (if such there be) that
characterizes my veridically
seeing the green cube. As pleasant as it
is for me to see the
green cube, it is thankfully not the only type of
experience one can
have. It seems undeniable that the properties at
issue are the weak
ones, rather than the strong ones. Martin’s case
against Hefty goes
like this:
[T]he
doctrine of infallibilism about the mental is particularly problematic in
relation
to
sensory states once we are forced to admit that appearances. systematically
appear
to us other than they are. For if we can be misled with respect to some
properties
of sensory experiences, there is a question as to what can motivate
the
claim that we are infallible in other judgments about them . . . part of the
motivation
of disjunctivism is precisely the thought that introspection of our sense
experience
supports Naïve Realism, and hence forces us to see both sense-datum
and
intentional theories as forms of error theory. (p. 12)
The idea here seems
to be that Hefty does not sit well with the
common-kind theory,
because the common-kind theory already
accepts some sort
of fallibility to introspection in rejecting Naïve
Realism. In
rejecting Naïve Realism, the common-kind theorist
denies that
veridical experiences consist in part in the objects
perceived. Combining
this with the claim that Naïve Realism introspectively seems to be true – a claim that, as we’ve seen, Martin
thinks the
common-kind theorist should accept (see discussion of
(1) above) – the
result is that introspection is fallible about the metaphysical nature of
perceptual experience. If the common-kind theory
is already committed
to introspection delivering fallible results
about the
metaphysical nature of experience, the thought seems to
be, then the idea
that it would be infallible about some other aspect
of experience seems
to be undermined.17 This is Martin’s reason for
thinking that Hefty
is implausible.
In order to
assess this reason to reject Hefty, one more interpretive
issue concerning
Hefty needs to be settled. Hefty, recall, was
the epistemic
principle that “a responsible subject who wishes to
determine how things
are for themselves sensorily must . .
. not only
correctly identify
phenomenal properties of a specific sort when they
are present, but
also they cannot be misled into judging them present
when they are not”
(p. 10). This principle can be interpreted in two
ways: extensionally
or intensionally.
Taken
extensionally, Hefty entails that a subject who satisfies it
can discriminate on
the basis of introspection between events that
have the weak robust
property and events that lack it. But it is not
required, on the
extensional interpretation of Hefty, that the subject
know what sort of
properties she is discriminating between. It is
enough simply that
she make the discriminations, on the basis of
introspection,
infallibly.
Taken
intensionally, Hefty is much more demanding. A subject
who satisfies
intensional Hefty will be disposed to judge correctly
that she has weak
robust properties of sort R, where R specifies
the metaphysical
nature of the robust properties: e.g., sense-data,
or representational
properties. Intensional Hefty says, in effect, that
introspection can
reveal the basic metaphysical nature of the properties
that characterize
what it is like to have an experience. If intensional
Hefty is true, then introspection
can reveal that perceptual
experience is the
having of representational properties, or sense-data,
or some combination
– whichever (if any) of these properties
perceptual
experiences turn out to have.
In an earlier
paper, Martin gave convincing grounds for doubting
intensional Hefty.
If intensional Hefty were correct, Martin has
noted, it would
difficult to explain how there can so much as be
philosophical
disagreement about the nature of experience. The
disagreements
philosophers have about metaphysics of experience
don’t seem plausibly
to result from variation in their inner lives.18
It does not seem to
be introspection alone that decides between,
say, the sense-datum
theory and the theory that experience consists
entirely in
representational properties. Other sorts reasoning are
needed. So
introspection doesn’t seem to provide substantive knowledge
of weak robust
properties.
The reason
Martin gives in the text for rejecting Hefty also counts
against intensional
Hefty. If the common-kind theorist embraced
intensional Hefty,
she would be saying, in effect, “introspection
wrongly tells me that experiences partly consist in
external objects
that I perceive; yet
it also tells me infallibly that my experience
consists in weak
robust property R.” There is a tension here, given
that R is by
definition the sort of property that can be had by
hallucinations, and
so cannot be object-involving.
But neither of
the arguments Martin gives against Hefty work
so decisively
against the extensional version of Hefty. Introspection
may not infallibly
reveal the nature of weak robust properties (if
there are such), but
that’s compatible with it providing infallible
grounds for
discriminating between events that are experiences and
events that aren’t.
And this is also compatible with introspection
being wrong – even
systematically so – about the nature of weak
robust properties.
So for all Martin says, extensional Hefty has not
been shown to be
implausible, or even in tension with the commonkind
theory. Being
committed to extensional Hefty does not seem
to be a reason to
reject the common-kind theory, or to regard the
disjunctivist
conception of experience as the default.
But what
exactly is the common-kind theorist committed to? As
wes saw earlier, one
of the claims Martin thinks the common-kind
theorist is
committed to is that an event is an experience just in case
it has a robust
property of type R:
(2) E iff R.
From here, it is a
simple step to Hefty, with the following assumption:
subjects can
infallibly discriminate between events that are
experiences and
events that aren’t. For if a subject “couldn’t but be
in a position to
discriminate” experiences from non-experiences,
then she also
“couldn’t but be in a position to discriminate an situation
which lacked E1 . . . EN
from a situation which possessed
them”, where E1 . . . EN
is a weak robust property. This is one way
in which the
common-kind theorist’s commitment to Hefty could
arise.
It seems
plausible to suppose that any common-kind theorist is
indeed committed to
(2), and from (2) plus the assumption about
infallible
discrimination of experiences from non-experiences, some
version of Hefty
follows. The version that follows, however, is the
extensional version.
That version isn’t obviously implausible, and
in any case Martin’s
arguments against Hefty, as we’ve seen, work
only against the
intensional version.
Another
argument that the common-kind theorist is committed to
some version of
Hefty proceeds from two premises: I iff R (claim
(3) above), and the
transitivity of indiscriminability. The main idea
is the same as