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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.
2002 Elsevier Science (USA). All rights reserved.
E-mail address:
dro@ruccs.rutgers.edu.
1053-8100/02/$ - see front matter 2002 Elsevier Science (USA). All rights reserved.
PII: S1053-8100(02)00017-X
654
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.
656
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
657
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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