how many kinds of consc. rosenthal.pdf

Consciousness

and

Cognition

Consciousness and Cognition 11 (2002) 653–665

www.academicpress.com

How many kinds of consciousness?

David M. Rosenthal a,b

a Program in Philosophy, Neuroscience, and Psychology, Washington University,

St. Louis, MO, USA

b Philosophy and Cognitive Science, City University of NewYork Graduate Center,

365 Fifth Avenue, NewYork, NY 10016-4309, USA

Received 3 July 2002

Abstract

Ned Blocks inﬂuential distinction between phenomenal and access consciousness

has become a staple of current discussions of consciousness. It is not often noted,

however, that his distinction tacitly embodies unargued theoretical assumptions that

favor some theoretical treatments at the expense of others. This is equally so for his

less widely discussed distinction between phenomenal consciousness and what he

calls reﬂexive consciousness. I argue that the distinction between phenomenal and

access consciousness, as Block draws it, is untenable. Though mental states that have

qualitative character plainly diﬀer from those with no mental qualities, a mental

states being conscious is the same property for both kinds of mental state. For one

thing, as Block describes access consciousness, that notion does not pick out any

property that we intuitively count as a mental states being conscious. But the deeper

problem is that Blocks notion of phenomenal consciousness, or phenomenality, is

ambiguous as between two very diﬀerent mental properties. The failure to distin-

guish these results in the begging of important theoretical questions. Once the

two kinds of phenomenality have been distinguished, the way is clear to explain

qualitative consciousness by appeal to a model such as the higher-order-thought

hypothesis.

E-mail address: dro@ruccs.rutgers.edu.

PII: S1053-8100(02)00017-X

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D.M. Rosenthal / Consciousness and Cognition 11 (2002) 653–665

In important work over the last 10 or so years, Ned Block has forcefully argued

that researchers both in philosophy and in psychology apply the term consciousness

and its cognates to distinct kinds of mental occurrence, with theoretically confusing

results. Most of that work has focused on the now well known and widely discussed

distinction between what Block calls phenomenal consciousness and access con-

sciousness. A state is phenomenally conscious if, roughly, it has qualitative char-

acter; Ill say more about this shortly. By contrast, a state is access conscious if its

content is, in Blocks words, ‘‘poised to be used as a premise in reasoning,... [and]

for [the] rational control of action and... speech.’’ 1 According to Block, these two

types of mental occurrence are conceptually independent; a state can, in principle at

least, be conscious in one way without its being conscious in the other.

Block has also distinguished a third type of mental occurrence that is also often

called consciousness, but which, he argues, is distinct from each of the others. This

type of consciousness, which he has variously called reﬂexive, introspective,or

monitoring consciousness, involves the occurrence not just of one mental state, but

two. As he has recently put it, ‘‘[a]n experience is conscious in this sense just in case it

is the object of another of the subjects states, for example one has a thought to the

eﬀect that one has that experience.’’ 2 Its the contrast between phenomenal con-

sciousness and reﬂexive consciousness that has ﬁgured most prominently in Blocks

recent writing, and Ill focus mainly on that contrast in what follows.

Some commentators on Blocks work, myself among them, have raised questions

about these distinctions. One challenge has been about whether one or another of the

phenomena Block describes is properly speaking a kind of consciousness at all. For

this reason among others, Block now proposes to conduct the discussion without

using the term consciousness or its near synonym, awareness. Forswearing those

terms, he now often refers to the three types of mental occurrence simply as phe-

nomenality, global access, and reﬂexivity (202–203). 3

But diGculties remain, even apart from whether something should be called

consciousness. Most of the following discussion focuses on phenomenality and re-

ﬂexivity. But its worth making a few remarks about global access. For one thing,

global access, whatever its connection with consciousness, presumably comes in

many degrees. So its not clear that such connectivity constitutes a single psycho-

logical phenomenon subject to study. Nor, despite its current popularity, 4 is it clear

1 ‘‘On a Confusion about a Function of Consciousness,’’ The Behavioral and Brain Sciences,

18, 2 (June 1995): 227–247, p. 231; emphasis Blocks.

2 ‘‘Paradox and Cross Purposes in Recent Work on Consciousness,’’ Cognition, 79, 1–2

(April 2001): 197–219, p. 205. When not otherwise indicated, page references are to this article.

3 Still, he often speaks of phenomenality as consciousness of something, which seems to

make ineliminable reference to consciousness, e.g., in describing subjects as being phenom-

enally conscious of the letters in the Sperling experiment (209), discussed below.

4 See, e.g., Daniel C. Dennetts idea that ‘‘[c]onsciousness is cerebral celebrity,’’ ‘‘The

Message Is: There Is No Medium,’’ Philosophy and Phenomenological Research LIII, 4

(December 1993): 919–931, p. 929, echoed in much of Consciousness Explained, Boston: Little,

Brown, 1991; and Bernard J. Baarss idea of consciousness as due to a global workspace in,

e.g., A Cognitive Theory of Consciousness, Cambridge: Cambridge Univ. Press, 1988.

D.M. Rosenthal / Consciousness and Cognition 11 (2002) 653–665

655

why global access has anything at all to do with what we intuitively think of as

consciousness. Many mental events occur to which the system has relatively global

access even though they arent conscious in any way whatever. In typical circum-

stances, for example, many mental occurrences that bear on the organisms moving

about wont be conscious, though the system needs to have fairly global access to

them. Conversely, mental states are often conscious despite their lack of global

connectivity, as when we have a speciﬁc conscious thought or image that has little

bearing on the systems overall functioning.

Block claims that the relevant kind of access involves a states being ‘‘poised to be

used...for [the] rational control of action and...speech.’’ But control of action can

be rational without being conscious. So why think that a states being poised for

rational control has anything to do with whether that state is conscious, in any way

whatever? The question is especially pressing given robust experimental ﬁndings that

the readiness potentials associated with decisions occur measurably in advance of

our consciousness of those decisions. 5 Doubtless the answer is that our sense of

having control of ourselves and indeed of being rational in that control stems from

the way we are conscious of our decisions. We are conscious of ourselves as exerting

rational control over our actions. But that doesnt by itself show that a state must be

conscious to exert such rational control.

Putting global access to one side, let me turn to phenomenality. Block describes

phenomenality in diﬀerent ways that arguably pick out distinct types of mental

occurrence. On one account, ‘‘phenomenality... [is w]hat it is like to have an ex-

perience. When you enjoy the taste of wine, you are enjoying gustatory phenome-

nality’’ (202).

But Block also allows that phenomenality can occur not only without ones

knowing it, but in cases in which one would ﬁrmly deny its occurrence. For example,

in cases of so-called visual extinction, subjects report having no subjective experience

of certain visual stimuli on one side of the visual ﬁeld (198). And Block argues that it

is theoretically open to see these subjects as ‘‘really... hav[ing] phenomenal experi-

ence of those stimuli without knowing it’’ (203). On this interpretation, he urges,

subjects have phenomenal consciousness without access consciousness, phenome-

nality without global access. Similarly, the phenomenality Block posits in the striking

case of aerodontalgia he describes is evidently phenomenality without reﬂexivity,

5 See, e.g., Benjamin Libet, Curtis A. Gleason, Elwood W. Wright, and Dennis K. Pearl,

‘‘Time of Conscious Intention to Act in Relation to Onset of Cerebral Activity (Readiness

Potential),’’ Brain, 106, Part III (September 1983): 623–642; Patrick Haggard, Chris Newman,

and Edna Magno, ‘‘On the Perceived Time of Voluntary Actions,’’ British Journal of

Psychology, 90, Part 2 (May 1999): 291–303; and Patrick Haggard and Benjamin Libet,

‘‘Conscious Intention and Brain Activity,’’ Journal of Consciousness Studies, 8, 11 (November

2001): 47–63.

See also my ‘‘The Timing of Conscious States,’’ Consciousness and Cognition, 11, 2 (June

2002): 215–220, and additional references there.

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D.M. Rosenthal / Consciousness and Cognition 11 (2002) 653–665

though the trace laid down in aerodontalgia is very likely no kind of phenomenality

at all. 6

This does not ﬁt comfortably, however, with the explanation of phenomenality as

‘‘[w]hat it is like to have an experience.’’ Its important to distinguish this somewhat

special use of the phrase what its like to describe subjectivity from its more general,

nonmental use. There is something its like to be a table, or even to be this very table.

What its like to be a table, for example, is roughly somethings having characteristic

features of tables.

But this is of course not whats involved in talking about what its like to have an

experience. As Nagel stressed in the article that launched that phrase, what its like to

have an experience is what its like for the individual that has the experience. When a

person enjoys the taste of wine, thereby enjoying gustatory phenomenality, there is

something its like for that person to experience the taste of the wine.

Not so in cases of visual extinction; there is nothing its like for an extinction

subject to have a qualitative experience of the extinguished stimuli. Thats why seeing

visual extinction as the having of phenomenality without ones knowing it does not

ﬁt comfortably with the explanation of phenomenality in terms of what its like to

have an experience.

Block has argued elsewhere that there being something its like in the relevant way

need not involve there being something its like for a subject. The added phrase, he

urges, implies having access to oneself, which is unnecessary for phenomenality. 7 But

there being something its like for one does not imply any explicit access to oneself;

one can be conscious of oneself in the relevant way without also being conscious that

one is. And such implicit, nonintrospective access must in any case occur if there is

something its like to have the experience. Were not interested in there being

something its like for somebody else to have the experience; there must be something

its like for one to have it, oneself. Without specifying that, what its like would be on

a par with what its like to be a table.

If conscious and aware are vexed terms, perhaps we also shouldnt expect much

from the phrase what its like. But, as Block notes in ‘‘Paradox and Cross Pur-

poses,’’ ‘‘[a]ny appeal to evidence to back a theory of consciousness depends on a

pre-theoretic concept of consciousness to supply a starting point’’ (202). So we need

some way to tell, in commonsense terms, when phenomenality occurs and when it

doesnt. And, if we disallow the appeal to there being something its like for one, its

unclear that any pretheoretic way remains.

The disparity between explaining phenomenality in terms of there being some-

thing its like for one and allowing phenomenality of which one has no knowledge

6 In these anecdotal cases, tooth extractions under general anesthetic alone resulted in later

pains, whereas that did not occur when both local and general were administered. Block

hypothesizes that the traces laid down by extractions under general anesthetic alone exhibit

phenomenality. On aerodontalgia, see Robert Melzack and Patrick D. Wall, The Challenge of

Pain, 2nd ed., Penguin, 1988, and P. W. Nathan, ‘‘Pain and Nociception in the Clinical

Context,’’ Philosophical Transactions of the Royal Society of London B, 308 (1985): 219–226.

7 Replying to me, in ‘‘Biology versus Computation in the Study of Consciousness,’’ The

Behavioral and Brain Sciences, 20, 1 (March 1997): 159–166, p. 162.

D.M. Rosenthal / Consciousness and Cognition 11 (2002) 653–665

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suggests that there are, after all, two distinct kinds of phenomenality in play. One

kind consists in the subjective occurrence of mental qualities, while the other kind

consists just in the occurrence of qualitative character without there also being

anything its like for one to have that qualitative character. Lets call the ﬁrst kind

thick phenomenality and the second thin phenomenality. Thick phenomenality is just

thin phenomenality together with there being something that its like for one to have

that thin phenomenality. Just as its useful to distinguish diﬀerent applications of the

term consciousness, so the term phenomenality and its cognates may well be used

in these two distinct ways. 8

If we bracket the issue about how to understand the admittedly vexed phrase

what its like, Blocks view seems to be that phenomenality is simply thin phe-

nomenality, and what Im calling thick phenomenality is phenomenality plus re-

ﬂexivity. For example, he seems to take the ability to report a mental state as an

indication that reﬂexivity is present, presumably because reporting something indi-

cates awareness of it. Thin phenomenality, such as that which occurs in visual ex-

tinction, is not reportable, and we have only theoretical reasons to posit it.

Terminology aside, this ﬁts neatly with my own view of these things. The

pretheoretic notion of a mental states being conscious, Ive argued elsewhere, is

that of ones being conscious of being in that state. Common sense doesnt count

as conscious any state of which a subject is wholly unaware. So states with merely

thin phenomenality are not in any pretheoretic, commonsense way conscious

states.

All thats needed, then, to explain what it is for a mental state to be conscious in

that pretheoretic way is to determine the way were conscious of the mental states we

count as conscious states. The traditional answer to this, from Locke and Kant to

David Armstrong and William Lycan, 9 appeals to sensing; we are conscious of our

conscious states by way of some kind of ‘‘inner sense.’’

But inner sense is an unsatisfactory answer to our question. Sensing is distin-

guished by its having some mental quality; so being conscious of our conscious states

by way of some higher-order, inner sense would require that there be higher-order

qualities. But the only mental qualities that occur when mental states are conscious

are those of the states we are conscious of; there are no additional qualities in virtue

8 Thus Block objects to the apparent assimilation by Anthony I. Jack and Tim Shallice

(‘‘Introspective Physicalism as an Approach to the Science of Consciousness,’’ Cognition, 79,

1–2 [April 2001]: 161–196) and by Stanislas Dehaene and Lionel Naccache (‘‘Towards a

Cognitive Neuroscience of Consciousness: Basic Evidence and a Workshop Framework,’’

Cognition, 79, 1–2 [April 2001]: 1–37) of phenomenality to its function. But it may well be that

these authors are simply talking about thick phenomenality.

9 Immanuel Kant, Critique of Pure Reason, transl. and ed. Paul Guyer and Allen W. Wood,

Cambridge: Cambridge Univ. Press, 1998, p. 174, A22/B37; John Locke, An Essay Concerning

Human Understanding, edited from the 4th (1700) edition by Peter H. Nidditch, Oxford:

Oxford Univ. Press, 1975, II, i, 4, p. 105; D. M. Armstrong, ‘‘What Is Consciousness?,’’ in

Armstrong, The Nature of Mind, St. Lucia, Queensland: University of Queensland Press, 1980,

55–67, p. 61; William G. Lycan, Consciousness and Experience, Cambridge, MA: MIT Press/

Bradford Books, 1996, ch. 2, pp. 13–43.

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