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 naďve 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 naďve 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 Naďve 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 Naďve

Realism. In rejecting Naďve Realism, the common-kind theorist

denies that veridical experiences consist in part in the objects

perceived. Combining this with the claim that Naďve 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 above: if I and R are co-extensive, then infallible

discrimination of events with I from events without I just is infallible

discrimination of events with R from events without R. And the

latter just is Hefty.

Why think that subjects can infallibly discriminate events with

I from events without I? Let x be an event that is indiscriminable

from a veridical perception. Let e be an event that is discriminable

from a veridical perception. Now suppose that subjects can’t

infallibly discriminate events with I from events without I. In particular,

suppose that e and x are themselves indiscriminable. Then e is

indiscriminable from x, and x is (by definition) indiscriminable from

a veridical perception. If indiscriminability is transitive, then e will

be indiscriminable from a veridical perception. But by hypothesis, e

was discriminable from a veridical perception. So we get a contradiction.

That is another argument that the common-kind theorist is

committed to Hefty.19

There seem to be two arguments suggested by Martin’s text that

the common-kind theorist ends up committed to Hefty. Neither argument,

however, shows that the common-kind theorist is committed

the intensional version of Hefty. And it’s the intensional version that

Martin argues against.

 

4. A RESIDUAL PROBLEM

As Martin characterizes the common-kind theory, it ought to be

committed to the view that for each indiscriminability property (e.g.,

the property of being indiscriminable from my veridically seeing

the green cube), there is a single robust mental property such that

any event with the indiscriminability property has the robust mental

property. Some doubt is cast on this claim by considerations related

to intransitivity of some indiscriminability properties. Notably, if

being indiscriminable with respect to hue is intransitive, then there

is reason to reject the common-kind theory as Martin characterizes

it. In this section, I discuss whether this counts in favor of

disjunctivism.

Consider three red swatches that differ slightly in hue: they

are, say, red38, red39 and red40. Many philosophers think that

indiscriminability respect to color is an intransitive relation. Such

intransitivity is supposed to be illustrated by cases of the following

sort: a subject comparing the red38 swatch with the red39 swatch

(at a time) cannot discriminate between their hues. The same subject

comparing the red39 swatch with the red40 swatch (with the red38

swatch out of view) cannot discriminate those hues either. But the

same subject comparing the red38 swatch with the red40 swatch

(with the red39 swatch out of view) can discriminate the hues of

those.

The case just described involves only three swatches, but that’s

not essential to what it is supposed to illustrate. What’s essential is

that there be discriminable hues on the outer edges of a range of

indiscriminable ones. How many indiscriminable ones occupy the

range is not important. If there are cases of the sort just described

– and many philosophers think there are, though some disagree20

they illustrate the intransitivity of looking the same with respect to

hue.

For the sake of argument, I am going to ignore the controversy,

and assume that indiscriminability with respect to hue really is

intransitive. I will also assume, for simplicity, that the intransitivity

shows up with just three swatches. This is empirically dubious,

but makes it easier to get to the main point.21 If it turns out that

indiscriminability with respect to hue isn’t intransitive, then there

is one less reason to reject the common-kind theory as Martin

characterizes it.

It will be useful to spell out a (putative) case of intransitive

indiscriminability in a bit more detail. Let I38 be the property of

being indiscriminable from a veridical perception of red38, and let

E38 and E40 be, respectively, an event of veridically seeing a swatch

of red38 and an event of veridically seeing a swatch of red40. And

finally, make the following assumptions about E38 and E40: E38

is indiscriminable from a veridical perception of red39 and red40;

and E40 is indiscriminable from a veridical perception of red41 and

red42. So E38 has three indiscriminability properties: I38, I39 and

I40. Given these assumptions, E38 and E40 share the indiscriminability

property I40. Both are indiscriminable from a veridical

perception of red40.

What must Martin’s common-kind theorist say about the robust

properties in virtue of which E38 and E40 each have I40? One

version of the common-kind theory would predict that these robust

properties have to be different. For by the hypothesis of intransitivity,

red38 is discriminable from red40. If these shades are

discriminable, then at least some common-kind theorists will want

to say that the specific robust properties are too. These will include

common-kind theorists who take the specific robust properties to

be representational ones, so that differences in what is represented

result in phenomenal differences.

This last move has a notable consequence: one and the same

indiscriminability property could be had in virtue of having different

specific robust properties. And this is to deny one of the claims that

Martin attributed to the common-kind theory: that any two experiences

sharing an indiscriminability property share the same specific

robust property.

Is the view just sketched a disjunctivist view? There is a similarity

with disjunctivism: both disjunctivism and the view sketched

deny that any two experiences that are indiscriminable from the

same veridical perception share the same robust mental property.

However, there are also notable differences. Whereas the disjunctivist

holds that there are pairs of hallucinations and veridical

perceptions that are indiscriminable from the same veridical perception,

yet are of fundamentally different kinds, the view just sketched

can allow that pairs of experiences with different specific robust

properties nevertheless are of the same fundamental kind. Both

experiences have, as it might be, representational phenomenal

properties, and for all the view says, they have a general fundamental kind in common. The difference is only at the level of the specific robust properties.

So the view sketched does not seem to capture the heart of

disjunctivism. It does, however, seem to be incompatible with a

version of intensional Hefty – a version that says that introspection

infallibly reveals which specific robust properties a subject has.

But as we have seen, there are independent reasons to think that

intensional versions of Hefty are wrong anyway.

 

5. CONCLUSION

I’ve suggested that someone could accept the main thrust of the

common-kind theory, while rejecting two other claims that Martin

attributes to it. The two claims are these: first, that the kind common

to perception and hallucination is a property of an event in virtue

of which it is indiscriminable from a veridical perception; second,

that it is a property in virtue of which it is indiscriminable from

anything at all (where indiscriminability is a cognitive notion). The

main thrust of the common-kind theory, I suggested, is that there

are pairs of hallucination and veridical perception sharing a fundamental

kind of mental state, and this part of the theory survives the

denial of the two claims just mentioned.

For all my complaints about the link Martin sees between

indiscriminability and the phenomenal, rejecting it leaves a

serious question unanswered. Even to state the debate between

disjunctivism and its opponents, one needs a way to characterize

the relevant pairs of perceptions and hallucinations. Only some

such pairs raise the question whether they share a fundamental

mental property. Which pairs are these? The claim that they are

the pairs that are indiscriminable from the same veridical perception

provides a simple answer. If this answer is rejected, it’s not

clear what to replace it with. Replacing it with some other notion

of indiscriminability, or with some notion of phenomenal sameness,

brings in weighty theoretical commitments at the outset – just

as Martin’s cognitive notion of indiscriminability does. The moral

seems to be that in this debate, it is difficult to escape making

theoretical commitments from the very start about the kind of access

to experience that introspection provides.22

 

 

 

 

NOTES

 

1 So “being indiscriminable from a veridical perception” should be taken to

mean something stronger than simply being indiscriminable from some veridical

perception or other. How much stronger? If I had two successive veridical experiences

of numerically different but qualitatively identical green cubes, would

the property of being indiscriminable from each be different indiscriminability

properties? For the purposes of this discussion, they could just as well count as

instances of the same property.

 

2 Martin grants the conclusion of the Causal Argument from Hallucination (see

section 4), which he formulates as follows: “whatever kind of experience does

occur in situations like h [hallucination], it is possible that such a kind of experience

occurs when one is veridically perceiving” (p. 12). Of course, “whatever

kind . . .” is restricted to exclude the kind: hallucination.

 

3 . . . while the perceptual event is of a fundamental kind which could not

occur when hallucinating, nonetheless this very same event is also of some other

psychological kind or kinds which a causally matching hallucinatory event . . .

belongs to” (p. 17).

 

4 Martin’s stripe of disjunctivism grants the conclusion of the Causal Argument

from Hallucination (see previous note). There could be versions of disjunctivism

that don’t, however.

 

5 Before beginning the critical part of the discussion, a final expository note,

and a warning. Martin’s disjunctivism is officially undecided on two matters:

first, it leaves unsettled whether it applies to each sensory modalities, or only

to some, or only to perceptual experience in general. Second, it is unsettled on the

status of illusions (where these are distinct from hallucinations) – whether they

always instantiate robust properties in virtue of which they are indiscriminable

from veridical perceptions or not, and if so, what sort of robust properties do this.

I believe that Martin has views on both of these matters, but that they don’t bear

on the issues raised in his paper.

The warning: my discussion, like Martin’s discussion, takes as understood

the idea that a particular, unrepeatable experience could be indiscriminable from

another (perhaps repeatable) event. It’s not entirely clear what this means. The

relevant notion of indiscriminability can’t be a statistical notion, since the event

said to be indiscriminable is unrepeatable. Nor can the notion be reasonably

understood by considering what would happen if the subject had two simultaneous

experiences, compared them, and found that they were the same in the relevant

respect (as one might be able to do with two physical objects). Perhaps one

could think of how the subject would regard the pair of experiences, if she had

them successively; but that introduces complications about memory that seem

extraneous. Nevertheless, there is some intuitive sense in which certain pairs of

experiences seem the same to the subject. Such a notion is needed even to state

the debate between the disjunctivist and the common-kind theorist, and that is one

role that is played by Martin’s notion of indiscriminability. I return to this point

in section 5.

 

6 Another example: consider an experience of seeing the Müller-Lyer lines.

Which veridical perception is such that having an experience of these lines is

indiscriminable from it? Presumably, if two lines really did differ in length,

but each had the characteristic arrows drawn around them, they would look

different than the lines look when they are the same length, at least given how

our perceptual systems work.

In the very latest version of Martin’s paper (written after these comments),

Martin grants that Escher-experiences as a whole are not indiscriminable from a

veridical perception, but suggests that they have constituent parts, each of which

is indiscriminable from a veridical perception (p. 31). This strikes me as an ad

hoc move tailored to specific example, and a retraction of a central claim.

 

7 Such an error theory might hold that color is a property of mental, internal

objects such as sense-data, that it couldn’t even in principle be a property of things

external to the mind, and that color experience nevertheless represents external

things as being colored.

 

8 One sort of worry that a materialist about the mental might press is how experience

could ever get to represent color properties, if such properties were never

instantiated.

 

9 The indefinite description “a visual perception” should be taken to mean the

same as “some veridical perception or other.” Cf. p. 20: “[t]he concept of perceptual

experience in general is that of situations indiscriminable from veridical

perception”; and the passage cited earlier from p. 22: “I argued above that being

indiscriminable from veridical perception is the most inclusive conception we

have of what sensory experience is.”

 

10 In section 3 I discuss some passages from pp. 10–11 of Martin’s paper that

show that he construes the common-kind theory is this way.

 

11 In the very latest version of Martin’s paper (written after these comments),

Martin makes explicit that he accepts the other notion of indiscriminability, not

the positive notion (fn. 11, p. 10). To state the issue between disjunctivism and its

opponents, some way is needed to characterize the similarity between the relevant

experiences, and various notions of indiscriminability are candidate ways to do

this. So it seems worth having the positive notion on the table.

 

12 Cf. “some event is an experience of a street scene just in case it couldn’t be

told apart through introspection from a veridical perception of the street as the

street” (p. 9); “If the condition of indiscriminability is to be met, then a situation

of experience must not lack any property necessary for veridical perception

the absence of which is recognisable simply through reflection” (p. 20); “if any

property of a veridical perception is introspectible – i.e. is recognisagbly present

in perception through reflection . . .” (p. 22). Although in section 9 of his paper

Martin also appeals to impersonal notions of indiscriminability, which seems in

tension with this; I discuss this notion briefly at the end of this section.

 

13 TimothyWilliamson, Identity and Discrimination (Oxford: Blackwell, 1990),

p. 8. Two notable differences between the two notions are these. First, the

positive notion makes use of the notion of disposition, whereas the double negative

notion makes use of the notion of an ability. Second, where the positive

notion defines indiscriminability in terms of judgment, Williamson’s

notion defines it in terms of knowledge. Interestingly, only the first of these

differences seems to survive the attempt to define corresponding notions of

discriminability. For suppose X and Y were discriminable by S at t just in case S

was disposed to judge X distinct from Y. Then X and Y could count as discriminable

for S at t, even in the case that X = Y. And this seems to stretch the notion

of discriminability unacceptably far beyond the ordinary notion. If this infelicity

were fixed by adding that the S at t be disposed to make a correct judgment, then

it starts to look like it involves an appeal to knowledge (or something very much

like it, given the link between knowledge and reliable judgment) after all. (Given

the two dimensions of variation in the pair of notions of indiscriminability we’ve

been considering, there are clearly other notions of indiscriminability that could

also be considered.)

 

14 There may be an additional reason for the common-kind theorist to reject

the link between phenomenality and indiscriminability, at least on Williamson’s

notion of indiscriminability. Consider once more what the sufficiency claim

comes to, givenWilliamson’s notion:

If S has I*, then S cannot activate knowledge that having-I* is distinct

from having a veridical perception.

It is not clear why a common-kind theorist should accept this. Suppose the

epistemic basis in question is supposed to be reflection, where this includes not

only introspection but philosophical theorizing as well. Let us grant that if S has

I*, then on the basis of reflection, S cannot activate knowledge that she’s not

having a veridical perception. Nonetheless, if S is a common kind theorist, S will

take herself to know by philosophical theorizing that having I* is distinct from

having a veridical perception, because S will take herself to know that she could

have I* even if she weren’t veridically perceiving. So it seems that, by her lights, at

least, she can activate knowledge that having I* is distinct from having a veridical

perception.

Of course, Martin thinks that the philosophical theorizing that typically leads

common-kind theorists to this conclusion is mistaken, and perhaps he’s right. But

if the claim is that a subject cannot activate the relevant knowledge on the basis

of philosophical reflection, then it seems unmotivated to attribute the sufficiency

claim to the common-kind theorist in the first place.

 

15 In considering this worry in the text, Martin also discusses the inattentive,

hasty subject John, who treats samples of scarlet and vermillion indifferently.

Intutively, his experiences of each should count as distinct; yet, as Martin points

out, it does not seem inappropriate to say that John can’t discriminate scarlet

from vermillion. Martin takes the moral to be that the disjunctivist should adopt

an ‘impersonal’ notion of indiscriminability, where this impersonal notion applies

equally to the dog. I think the moral is rather that it’s the notion of an ability to

discriminate, rather than a disposition to discriminate, that should figure in the

definitions of indiscriminability.

 

16 Cf. last paragraph of Martin’s section 2.

 

17 The same consideration that makes Hefty implausible for a common-kind

theorist should make it implausible for anyone who accepts Martin’s assumption

that introspection supports Naďve Realism. If, as per Martin’s assumption,

introspection on experience tells you that it consists in part of an object that

you are veridically perceiving, it will be incorrect in cases of hallucination, no

matter whether disjunctivism or the common-kind theory is true. By Martin’s

lights, the common-kind theorist is forced to admit that appearances systematically

appear to us other than they are, because no experiences are the way

introspection (supposedly) says they are; the disjunctivist, in contrast, allows that

some experiences are that way. Whether the disjunctivist also has to admit that

appearances appear other than they are systematically depends on the extent to

which experiences are not veridical. For discussion of the idea that most experiences

are not veridical, see A.D. Smith, The Problem of Perception (Harvard

University Press, 2002), chapter 1.

 

18 Cf. ‘Beyond Dispute’, in T. Crane and S. Patterson (eds.), The History of the

Mind-Body Problem, p. 197.

 

19 The defense just mentioned itself has a controversial premise – the premise

that indiscriminability is transitive. This has been defended by Graff (2001), but

is widely thought to be shown false by cases of the sort discussed in the next

section.

 

20 For assumptions that there are cases structured like the one described, see N.

Goodman, The Structure of Appearance, 1st edn., Cambridge: Harvard University

Press, 1951 and D. Armstrong, A Materialist Theory of Mind, London:

Routledge, 1968. For dissent, see D. Graff, ‘Phenomenal Continuaa and the

Sorites’, Mind (2001); D. Raffman, ‘Is Indistinguishability Non-transitive?’,

Philosophical Topics 28(1) (Spring 2001), pp. 153–175.

 

21 I take it that the heart of the controversy being ignored concerns whether the

relation in question is transitive or not; simplifying assumptions about what form

it takes won’t change anything.

 

22 For helpful comments on earlier drafts, thanks to Alex Byrne and Bernard

Nickel. For extensive discussion of every issue discussed here, thanks to Maja Spener, Scott Sturgeon, and David Chalmers. Additional thanks to the last two for criticizing later drafts. Finally, many thanks are due to Mike Martin, for writing such a rich and rewarding paper, and for so many nice discussions of it before and during the 2002 Oberlin Colloquium.

 

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