Some Concepts of Consciousness[1]
Ned Block
NYU
Abstract
Consciousness is a mongrel concept: there are a number of very
different "consciousnesses".
Phenomenal consciousness is experience; the phenomenally conscious
aspect of a state is what it is like to be in that state. The mark of access-consciousness, by
contrast, is availability for use in reasoning and rationally guiding speech
and action. These concepts are often
partly or totally conflated, with bad results.
The concept
of consciousness is a hybrid or better, a mongrel concept: the word
`consciousness' connotes a number of different concepts and denotes a number of
different phenomena. We reason about
"consciousness" using some premises that apply to one of the
phenomena that fall under "consciousness", other premises that apply
to other "consciousnesses" and we end up with trouble. There are many parallels in the history of
science. Aristotle used `velocity'
sometimes to mean average velocity and sometimes to mean instantaneous
velocity; his failure to see the distinction caused confusion (Kuhn,
1964). The Florentine Experimenters of
the 17th Century used a single word (roughly translatable as "degree of
heat") for temperature and for heat, generating paradoxes (Block and
Dworkin, 1974). For example, when they
measured "degree of heat" by whether various heat sources could melt
paraffin, heat source A came out hotter than B, but when they measured
"degree of heat" by how much ice a heat source could melt in a given
time, B was hotter than A (Wiser and Carey, 1983). These are very different cases, but there is
a similarity, one that they share with the case of `consciousness'. The similarity is: very different concepts
are treated as a single concept. I think
we all have some tendency to make this mistake in the case of
"consciousness".
Phenomenal Consciousness
First, consider phenomenal consciousness,
or P-consciousness, as I will call it.
Phenomenal consciousness is experience; what makes a state phenomenally
conscious is that there is something “it is like” (Nagel, 1974) to be in that
state. Let me acknowledge at the outset
that I cannot define P-consciousness in any remotely non-circular way. I don't consider this an embarrassment. The history of reductive definitions in
philosophy should lead one not to expect a reductive definition of
anything. But the best one can do for
P-consciousness is in some respects worse than for many other things because
really all one can do is point to the phenomenon (cf. Goldman, 1993a). Nonetheless, it is important to point
properly. John Searle, acknowledging that consciousness cannot be defined non-circularly,
defines it as follows:
“By consciousness I simply mean those
subjective states of awareness or sentience that begin when one wakes in the
morning and continue throughout the period that one is awake until one falls
into a dreamless sleep, into a coma, or dies or is otherwise, as they say,
unconscious. [This comes from Searle 1990; there is a much longer attempt along
the same lines in his 1992, p. 83ff.]”
I will argue
that this sort of pointing is flawed because it points to too many things, too
many different consciousnesses.
So how
should we point to P-consciousness?
Well, one way is via rough synonyms.
As I said, P-consciousness is experience. P-conscious properties are experiential
properties. P-conscious states are
experiential states; that is, a state is P-conscious just in case it has
experiential properties. The totality of
the experiential properties of a state are “what it is like" to have
it. Moving from synonyms to examples, we
have P-conscious states when we see, hear, smell, taste and have pains.
P-conscious properties include the experiential properties of sensations,
feelings and perceptions, but I would also include thoughts, wants and
emotions.[2] An important feature of P-consciousness is
that differences in intentional content often make a P-conscious
difference. What it is like to hear a
sound as coming from the left differs from what it is like to hear a sound as
coming from the right. Further, P-conscious
differences often make an intentional difference. And this is partially explained by the fact
that P-consciousness is often—perhaps
even always--representational. (See Jackendoff, 1987; van Gulick, 1989; McGinn,
1991, Ch 2; Flanagan, 1992, Ch 4; Goldman,1993b.) So far, I don't take myself to have said
anything terribly controversial. The
controversial part is that I take P-conscious properties to be distinct from
any cognitive, intentional, or functional property. At least, no such reduction of P-consciousness
to the cognitive, intentional or functional can be known in the armchair manner
of recent deflationist approaches. (Cognitive = essentially involving thought;
intentional properties = properties in virtue of which a representation or
state is about something; functional properties = e.g. properties definable in
terms of a computer program. See Searle,
1983 on intentionality; See Block, 1980,1994, for better characterizations of a
functional property.) But I am trying
hard to limit the controversiality of my assumptions. Though I will be assuming that functionalism
about P-consciousness is false, I will be pointing out that limited versions of
many of the points I will be making can be acceptable to the functionalist.[3]
By way of
homing in on P-consciousness, it is useful to appeal to what maybe a contingent
property of it, namely the famous "explanatory gap". To quote T.H. Huxley (1866), "How it is
that anything so remarkable as a state of consciousness comes about as a result
of irritating nervous tissue, is just as unaccountable as the appearance of
Djin when Aladdin rubbed his lamp."
Consider a famous neurophysiological theory of P-consciousness offered
by Francis Crick and Christof Koch: namely, that a synchronized35-75 hertz
neural oscillation in the sensory areas of the cortex is at the heart of
phenomenal consciousness. Assuming for
the moment that such neural oscillations are the neural basis of sensory
consciousness, no one has produced the concepts that would allow us to explain
why such oscillations are the neural basis of one phenomenally consciousness
state rather than another or why the oscillations are the neural basis of a
phenomenally conscious state rather than a phenomenally unconscious state.
However,
Crick and Koch have offered a sketch of an account of how the 35-75 hertz
oscillation might contribute to a solution to the "binding
problem". Suppose one
simultaneously sees a red square moving to the right and a blue circle moving
to the left. Different areas of the
visual cortex are differentially sensitive to color, shape, motion, etc. so
what binds together redness, squareness and rightward motion? That is, why don't you see redness and
blueness without seeing them as belonging with particular shapes and particular
motions? And why aren't the colors
normally seen as bound to the wrong shapes and motions? Representations of colors, shapes and motions
of a single object are supposed to involve oscillations that are in phase with
one another but not with representations of other objects. But even if the oscillation hypothesis deals
with the informational aspect of the binding problem (and there is some
evidence against it), how does it explain what it is like to see something
as red in the first place--or for that matter, as square or as moving to
the right? Why couldn't there be brains
functionally or physiologically just like ours, including oscillation patterns,
whose owners' experience was different from ours or who had no experience at
all? (Note that I don't say that there could be such brains. I just want to know why not.) No one
has a clue how to answer these questions.
The
explanatory gap in the case of P-consciousness contrasts with our better
(though still not very good) understanding of the scientific basis of cognition. We have two serious research programs into
the nature of cognition, the classical "language of thought” paradigm, and
the connectionist research program. Both
assume that the scientific basis of cognition is computational. If this is idea is right—and it seems
increasingly promising—it gives us a better grip on why the neural basis of a
thought state is the neural basis of that thought rather than some other
thought or none at all than we have about the analogous issue for consciousness
What I've
been saying about P-consciousness is of course controversial in a variety of
ways, both for some advocates and some opponents of some notion of
P-consciousness. I have tried to steer
clear of some controversies, e.g. controversies over inverted and absent
qualia; over Jackson's (1986) Mary, the woman who is raised in a black and
white room, learning all the physiological and functional facts about the brain
and color vision, but nonetheless discovers a new fact when she goes outside
the room for the first time and learns what it is like to see red; and even
Nagel's view that we cannot know what it is like to be a bat.[4] Even if you think that P-consciousness as I
have described it is an incoherent notion, you may be able to agree with the
main point of this paper, which is that a great deal of confusion arises as a
result of confusing P-consciousness with something else. Not even the concept of what time it is now
on the sun is so confused that it cannot itself be confused with something
else.
Access-Consciousness
I now turn to the non-phenomenal notion of
consciousness that is most easily and dangerously conflated with
P-consciousness: access-consciousness. I
will characterize access-consciousness, give some examples of how it makes
sense for someone to have access-consciousness without phenomenal consciousness
and vice versa, and then go on to the main theme of the paper, the damage done
by conflating the two.
A-consciousness is access-consciousness. A representation is A-conscious if it is broadcast for free use in reasoning and for direct “rational” control of action (including reporting). An A-state is one that consists in having an A-representation. I see A-consciousness as a cluster concept in which reportability is the element of the cluster that has the smallest weight even though it is often the best practical guide to A--consciousness.
The ‘rational’ is meant to rule out
the kind of automatic control that obtains in blindsight. (Blindsight is a syndrome involving patients
who have brain damage in the first stage of visual processing, primary visual
cortex. These patients seem to have
“holes” in their visual fields. If the
experimenter flashes stimuli in these holes and asks the patient what was
flashed, the patient claims to see nothing but can often guess at high levels
of accuracy, choosing between two locations or directions or whether what was
flashed was an ‘X’ or an ‘O’.)
I will
suggest that A-consciousness plays a deep role in our ordinary `consciousness'
talk and thought. However, I must admit
at the outset that this role allows for substantial indeterminacy in the
concept itself. In addition, there are
some loose ends in the characterization of the concept which cannot be tied up
without deciding about certain controversial issues, to be mentioned below.[5] My
guide in making precise the notion of A-consciousness is to formulate an
information processing correlate of P-consciousness that is not ad hoc and
mirrors P-consciousness as well as a non-ad hoc information processing notion
can.
In the original version of this
paper, I defined ‘A-consciousness’ as (roughly) ‘poised for control of speech,
reasoning and action’.[6] In a comment on the original version of this
paper, David Chalmers (1997) suggested defining ‘A-consciousness’ instead as
‘directly available for global control’.
Chalmers’ definition has the advantage of avoiding enumerating the kinds
of control. That makes the notion more
general, applying to creatures who have kinds of control that differ from
ours. But it has the disadvantage of
that advantage, counting simple organisms as having A-consciousness if they
have representations that are directly available for global control of whatever
resources they happen to have. If the idea of A-consciousness is to be an
information processing image of P-consciousness, it would not do to count a
slug as having A-conscious states simply because there is some machinery of
control of the resources that a slug happens to command..
As I noted, my
goal in precisifying the ordinary notion of access as it is used in thinking
about consciousness is to formulate a non-ad hoc notion that is close to an
information processing image of P-consciousness. A flaw in both my definition and Chalmers’ definition
is that they make A-consciousness dispositional whereas P-consciousness is
occurrent. As noted in the critique by
Atkinson and Davies (1995), that makes the relation between P consciousness and
A-consciousness the relation between the ground of a disposition and the
disposition itself. (See also Burge, 1997.)
This has long been one ground of criticism of both functionalism and
behaviorism (Block and Fodor, 1972), but there is no real need for an
information-processing notion of consciousness to be saddled with a category
mistake of this sort. I have dealt with
the issue here by using the term ‘broadcast’, as in Baars’ (1988) theory that
conscious representations are ones that are broadcast in a global
workspace. A-consciousness is similar to
that notion and to Dennett’s (1993) notion of consciousness as cerebral
celebrity.[7]
The interest in the A/P distinction
arises from the battle between two different conceptions of the mind, the
biological and the computational. The
computational approach supposes that all of the mind (including consciousness)
can be captured with notions of information processing, computation and
function in a system. According to this
view (often called functionalism by philosophers), the level of abstraction for
understanding the mind is one that allows multiple realizations, just as one
computer can be realized electrically or hydraulically. Their bet is that the different realizations
don’t matter to the mind, generally, and to consciousness specifically. The biological approach bets that the
realization does matter. If P = A, the
information processing side is right.
But if the biological nature of experience is crucial, then realizations
do matter, and we can expect that P
and A will diverge.[8]
Although I
make a distinction between A-consciousness and P-consciousness, I also want to
insist that they interact. For example,
what perceptual information is being accessed can change figure to ground and
conversely, and a figure-ground switch can affect one's phenomenal state. For example, attending to the feel of the
shirt on your neck, accessing those perceptual contents, switches what was in
the background to the foreground, thereby changing one's phenomenal state. (See Hill, 1991, 118-126; Searle, 1992.)
Of course,
there are notions of access in which the blindsight patient's guesses count as
access. There is no right or wrong here. Access comes in various degrees and
kinds, and my choice here is mainly determined by the desideratum of finding a
notion of A-consciousness that mirrors P-consciousness. If the blindsight patient’s perceptual
representations are not P-conscious, it would not do to count them as
A-conscious. (I also happen to think
that the notion I characterize is more or less one that plays a big role in our
thought, but that won't be a major factor here.)
I will
mention three main differences between P-consciousness and
A-consciousness. The first point, put
crudely, is that P-conscious content is phenomenal, whereas A-conscious
content is representational. It is of
the essence of A-conscious content to play a role in reasoning, and only
representational content can figure in reasoning. The reason this way of putting the point is
crude is that many (perhaps even all) phenomenal contents are also
representational. And some of the representational contents of a
P-conscious state may be intrinsic to those P-contents..[9]
(In the last
paragraph, I used the notion of P-conscious content. The P-conscious
content of a state is the totality of the state's experiential properties, what
it is like to be in that state. One can
think of the P-conscious content of a state as the state's experiential
"value" by analogy to the representational content as the state’s
representational "value". In
my view, the content of an experience can be both P-conscious and A-conscious;
the former in virtue of its phenomenal feel and the latter in virtue of its
representational properties.)
A closely
related point: A-conscious states are necessarily transitive: A-conscious
states must always be states of consciousness of. P-conscious states, by
contrast, sometimes are and sometimes are not transitive. P-consciousness, as such, is not
consciousness of. (I'll return to this
point in a few paragraphs.)
Second, A-consciousness
is a functional notion, and so A-conscious content is system-relative: what
makes a state A-conscious is what a representation of its content does in a
system. P-consciousness is not a
functional notion.[10] In terms of Schacter's model of the mind (see
the original version of this paper Block (1995)), content gets to be
P-conscious because of what happens inside the P-consciousness
module. But what makes content
A-conscious is not anything that could go on inside a module, but rather
informational relations among modules.
Content is A-conscious in virtue of (a representation with that content)
reaching the Executive system, the system that is in charge of rational control
of action and speech, and to that extent, we could regard the Executive module
as the A-consciousness module. But to
regard anything as an A-consciousness module is misleading, because what
makes a typical A-conscious representation A-conscious is what getting to the
Executive module sets it up to do, namely affect reasoning and action.
A third
difference is that there is such a thing as a P-conscious type or kind
of state. For example the feel of pain
is a P-conscious type--every pain must have that feel. But any particular token thought that is
A-conscious at a given time could fail to be accessible at some other time,
just as my car is accessible now, but will not be later when my wife has
it. A state whose content is
informationally promiscuous now may not be so later.
The paradigm
P-conscious states are sensations, whereas the paradigm A-conscious states are
"propositional attitude" states like thoughts, beliefs and desires,
states with representational content expressed by "that"
clauses. (E.g. the thought that grass is
green.) What, then, gets broadcast when
a P-conscious state is also A-conscious?
The most straightforward answer is: the P-content itself. However, exactly what this comes to depends
on what exactly P-content is. If
P-content is non-conceptual, it may be said that P contents are not the right
sort of thing to play a role in inference and guiding action. However, even with non-humans, pain plays a
rational role in guiding action.
Different actions are appropriate responses to pains in different
locations. Since the contents of pain do
in fact play a rational role, either their contents are conceptualized enough, or else non-conceptual or not
very conceptual content can play a rational role.
There is a
familiar distinction, alluded to above, between `consciousness’ in the sense in
which we speak of a state as being a conscious state (intransitive
consciousness) and consciousness of something (transitive
consciousness). (The
transitive/intransitive terminology seems to have appeared first in Malcolm
(1984) , but see also Rosenthal (1997).
Humphrey (1992) mentions that the
intransitive usage is much more recent, only 200 years old.) It is easy to fall into an identification of
P-consciousness with intransitive consciousness and a corresponding
identification of access-consciousness with transitive consciousness. Such an identification is over simple. As I mentioned earlier, P-conscious contents
can be representational. Consider a perceptual
state of seeing a square. This state has
a P-conscious content that represents something, a square, and thus it is a
state of P-consciousness of the square.
It is a state of P-consciousness of the square even if it doesn't
represent the square as a square, as would be the case if the perceptual
state is a state of an animal that doesn't have the concept of a square. Since there can be P-consciousness of
something, P-consciousness is not to be identified with intransitive
consciousness.
Here is a
second reason why the transitive/intransitive distinction cannot be identified
with the P-consciousness/A-consciousness distinction: The of-ness
required for transitivity does not guarantee that a content be utilizable by a consuming
system, a system that uses the representations for reasoning or planning or
control of action at the level required for A-consciousness. For example, a perceptual state of a
brain-damaged creature might be a state of P-consciousness of, say, motion,
even though connections to reasoning and rational control of action are damaged
so that the state is not A-conscious. In
sum, P-consciousness can be consciousness of, and consciousness of need not be
A-consciousness.
Those who
are uncomfortable with P-consciousness should pay close attention to
A-consciousness because it is a good candidate for a reductionist
identification with P-consciousness.[11]
Many of my
critics (Searle, 1992, Burge, 1997) have noted that if there can be “zombies”,
cases of A without P, they are not conscious in any sense of the term. I am sympathetic, but I don’t agree with the
conclusion that some have drawn that the A-sense is not a sense of
“consciousness” and that A is not a kind of consciousness. A-consciousness can be a kind of
consciousness even if it is parasitic on a core notion of P-consciousness. A parquet floor is a floor even though it
requires another floor beneath it. A
consciousness can come and go against a background of P consciousness.
The
rationale for calling A consciousness a kind of consciousness is first that it
fits a certain kind of quasi-ordinary usage.
Suppose one has a vivid mental image that is repressed. Repression need not make the image go away or
make it non-phenomenal. One might
realize after psychoanalysis that one had the image all along, but that one
could not cope with it. It is
“unconscious” in the Freudian sense—which is A-unconsciousness. Second, A-consciousness is typically the kind
of consciousness that is relevant to use of words like “conscious” and “aware”
in cognitive neuroscience. This point is
made in detail in my comment on a special issue of the journal Cognition (Block, 2001) This issue summarizes the
“state of the art” and some of the writers are clearly talking about
A-consciousness (or one or another version of monitoring consciousness—see
below) whereas others are usually talking about P-consciousness. The A notion
of consciousness is the most prominent one in the discussion in that issue and
in much of the rest of cognitive neuroscience.
(See the article by Dehaene and Naccache in that volume which is very
explicit about the use of A-consciousness.)
Finally, recall that my purpose in framing the notion of A consciousness
is to get a functional notion of consciousness that is not ad hoc and comes as
close to matching P consciousness as a purely functional notion can. I hope to show that nonetheless there are
cracks between P and A. In this
context, I prefer to be liberal with terminology, allowing that A is a form of
consciousness but not identical to phenomenal consciousness.
A-Consciousness Without P-Consciousness
The main point of this paper is that these
two concepts of consciousness are distinct and quite likely have different
extensions yet are easily confused. Let
us consider conceptually possible cases of one without the other. Actual cases will be more controversial.
First, I
will give some putative examples of A-consciousness without
P-consciousness. If there could be a
full-fledged phenomenal zombie, say a robot computationally identical to a
person, but whose silicon brain did not support P-consciousness, that would do
the trick. I think such cases
conceptually possible, but this is very controversial. (See Shoemaker, 1975,
1981)
But there is
a less controversial kind of case, a very limited sort of partial zombie. Consider the blindsight patient who
"guesses" that there is an `X' rather than an `O' in his blind
field. Taking his word for it (for the
moment), I am assuming that he has no P-consciousness of the `X'. The blindsight patient also has no
`X'-representing A-conscious content, because although the information that
there is an `X' affects his "guess", it is not available as a premise
in reasoning (until he has the quite distinct state of hearing and believing
his own guess), or for rational control of action or speech. Marcel (1986) points out that the thirsty
blindsight patient would not reach for a glass of water in the blind field. So
the blindsight patient's perceptual or quasi-perceptual state is unconscious in
the phenomenal and access senses (and in the monitoring senses to
be mentioned below too).
Now imagine
something that may not exist, what we might call superblindsight. A real blindsight patient can only guess when
given a choice from a small set of alternatives (`X'/`O'; horizontal/vertical,
etc). But suppose--interestingly, apparently contrary to fact--that a blindsight
patient could be trained to prompt himself at will, guessing what is in the
blind field without being told to guess.
The superblindsighter spontaneously says "Now I know that there is
a horizontal line in my blind field even though I don't actually see it."
Visual information of a certain limited sort (excluding color and complicated
shapes) from his blind field simply pops into his thoughts in the way that
solutions to problems we've been worrying about pop into our thoughts, or in
the way some people just know the time or which way is North without having any
perceptual experience of it. He knows
there is an ‘X’ in his blind field, but he doesn’t know the type font of the
‘X’. The superblindsighter himself
contrasts what it is like to know visually about an `X' in his blind field and
an `X' in his sighted field. There is
something it is like to experience the latter, but not the former, he
says. It is the difference between just
knowing and knowing via a visual experience. Taking his word for it, here is the point:
the perceptual content that there is an `X' in his visual field is A-conscious
but not P-conscious. The superblindsight case is a very limited partial zombie.
Of course,
the superblindsighter has a thought that there is an ‘X’ in his blind
field that is both A-conscious and P-conscious. But I am not talking about the thought. Rather, I am talking about the state of his
perceptual system that gives rise to the thought. It is this state that is A-conscious without
being P-conscious.[12]
The
(apparent) non-existence of superblindsight is a striking fact, one that a
number of writers have noticed, more or less.
What Marcel was in effect pointing out was that the blindsight patients,
in not reaching for a glass of water, are not superblindsighters. (See also Farah (1994). Blind perception is never super blind
perception.[13]
Notice that
the superblindsighter I have described is just a little bit different (though
in a crucial way) from the ordinary blindsight patient. In particular, I am not
relying on what might be thought of as a full-fledged quasi-zombie,
a super-duper-blindsighter whose blindsight is every bit as good,
functionally speaking, as his sight. In the case of the super-duper
blindsighter, the only difference between vision in the blind and
sighted fields, functionally speaking, is that the quasi-zombie himself regards
them differently. Such an example will
be regarded by some (though not me) as incoherent--see Dennett, 1991, for example. But we can avoid disagreement about the
super-duper-blindsighter by illustrating the idea of A-consciousness without
P-consciousness by appealing only to the superblindsighter. Functionalists may
want to know why the superblindsight case counts as A-conscious without
P-consciousness. After all, they may
say, if we have really high quality access in mind, the superblindsighter
that I have described does not have it, so he lacks both P-consciousness
and really high quality A-consciousness.
The super-duper-blindsighter, on the other hand, has both,
according to the functionalist, so in neither case, according to the objection,
is there A-consciousness without P-consciousness.
One could
put the point by distinguishing three types of access: (1) really high quality
access, (2) medium access and (3)poor access.
The actual blindsight patient has poor access (he has to be
prompted to guess), the superblindsight patient has medium access and the
super-duper blindsight patient--as well as most of us--has really high quality
access. The functionalist objector I am
talking about identifies P-consciousness with A-consciousness of the really
high quality kind, whereas I am allowing A-consciousness with only medium
access. (We agree in excluding low quality access. The issue, then, is whether the functionalist
can get away with restricting access to high quality access. I think not.
I believe that in some cases, normal phenomenal vision involves only
medium access. The easiest case to see
for yourself with is peripheral vision.
If you wave a colored object near your ear, you will find that in the
right location you can see the movement without having the kind of rich access
that you have in foveal vision. For
example, your ability to recover shape and color is poor.
Why isn’t
peripheral vision a case of A without P?
In peripheral vision, we are both A and P conscious of the same
features—e.g. motion but not color. But
in superblindsight—so the story goes—there is no P consciousness of the
horizontal line. (He just knows.) I conclude that A without P is conceptually
possible even if not actual.
P-Consciousness Without A-Consciousness
Consider an
animal that you are happy to think of as having P-consciousness for which brain
damage has destroyed centers of reasoning and rational control of action, thus
preventing A-consciousness. It certainly
seems conceptually possible that the neural bases of
P-consciousness systems and A-consciousness systems be distinct, and if they
are distinct, then it is possible, at least conceptually possible, for one to
be damaged while the other is working well.
Evidence has been accumulating for twenty-five years that the primate
visual system has distinct dorsal and ventral subsystems. Though there is much disagreement about the
specializations of the two systems, it does appear that much of the information
in the ventral system is much more closely connected to P-consciousness than
information in the dorsal system (Goodale and Milner, 1992). So it may actually be possible to damage
A-consciousness without P-consciousness and perhaps even conversely.[14]
Further, one
might suppose (Rey, 1983, 1988; White, 1987) that some of our own
subsystems--say each of the two hemispheres of the brain—might themselves be
separately P-conscious. Some of these
subsystems might also be A-consciousness, but other subsystems might not have
sufficient machinery for reasoning or reporting or rational control of action
to allow their P-conscious states to be A-conscious; so if those states are not
accessible to another system that does have adequate machinery, they will be
P-conscious but not A-conscious.
Here is
another reason to believe in P-consciousness without A-consciousness: Suppose that you are engaged in intense
conversation when suddenly at noon you realize that right outside your window,
there is—and has been for some time--a pneumatic drill digging up the
street. You were aware of the noise all
along, one might say, but only at
In addition,
this case involves a natural use of `conscious' and `aware' for A-consciousness
and P-consciousness.. `Conscious' and
`aware' are more or less synonymous, so when we have one of them we might think
of it as awareness, but when we have both it is natural to call that conscious
awareness. This case of P-consciousness
without A-consciousness exploits what William James (1890) called
"secondary consciousness" (at
least I think it does; James scholars may know better), a category that he may
have meant to include cases of P-consciousness without attention.
I have found
that the argument of the last paragraph makes those who are distrustful of
introspection uncomfortable. I agree
that introspection is not the last word, but it is the first word, when it comes
to P-consciousness. The example shows
the conceptual distinctness of P-consciousness from A-consciousness and it also
puts the burden of proof on anyone who would argue that as a matter of
empirical fact they come to the same thing.
A-consciousness
and P-consciousness very often occur together. When one or the other is
missing, we can often speak of unconscious states (when the context is
right). Thus, in virtue of missing
A-consciousness, we think of Freudian states as unconscious. And in virtue of missing P-consciousness, it
is natural to describe the superblindsighter or the unfeeling robot or computer
as unconscious. Lack of
monitoring-consciousness in the presence of A and P is also sometimes described
as unconsciousness. Thus Julian Jaynes
describes Greeks as becoming conscious when—in between the time of the Illiad
and the Odyssey, they become more reflective.
Flanagan
(1992) criticizes my notion of A-consciousness, suggesting that we replace it
with a more liberal notion of informational sensitivity that counts the
blindsight patient as having access-consciousness of the stimuli in his blind
field. The idea is that the blindsight
patient has some access to the information about the stimuli in the
blind field, and that amount of access is enough for access consciousness. Of course, as I keep saying, the notion of
A-consciousness that I have framed is just one of a family of access
notions. But there is more than a verbal
issue here. The real question is what
good is A-consciousness as I have framed it in relation to the blindsight
issue? The answer is that in blindsight,
the patient is supposed to lack "consciousness" of the stimuli
in the blind field. My point is that the
blindsight lacks both P-consciousness and a kind of access (both medium and
high level access in the terminology used earlier), and that these are easily
confused. This point is not challenged
by pointing out that the blindsight patient also has a lower level of access to
this information.
The kind of
access that I have built into A-consciousness plays a role in theory outside of
this issue and in daily life. Consider
the Freudian unconscious. Suppose I have
a Freudian unconscious desire to kill my father and marry my mother. Nothing in Freudian theory requires that this
desire be P-unconscious; for all Freudians should care, it might be
P-conscious. What is the key to the
desire being Freudianly unconscious is that it come out in slips, dreams, and
the like, but not be freely available as a premise in reasoning (in virtue
of having the unconscious desire) and that it not be freely available to guide
action and reporting. Coming out in slips and dreams makes it conscious in
Flanagan's sense, so that sense of access is no good for capturing
the Freudian idea. But it is unconscious in my A-sense. If I can just tell you that I have a desire
to kill my father and marry my mother (and not as a result of therapy) then it
isn't an unconscious state in either Freud's sense or my A sense. Similar points can be made about a number of
the syndromes that are often regarded as disorders of consciousness. For example, consider prosopagnosia, a
syndrome in which someone who can see noses, eyes, etc., cannot recognize
faces. Prosopagnosia is a disorder of
A-consciousness, not P-consciousness and not Flanagan's informational
sensitivity. We count someone as a
prosopagnosic even when they are able to guess at better than a chance level
who the face belongs to, so that excludes Flanagan's notion. Further,
P-consciousness is irrelevant, and that excludes P-consciousness as a
criterion. It isn't the presence or
absence of a feeling of familiarity that defines prosopagnosia, but rather the
patient not knowing who the person is whose face he is seeing or whether he
knows that person.
I am
finished sketching the contrast between P-consciousness and
A-consciousness. In the remainder of
this section, I will briefly discuss two cognitive notions of consciousness, so
that they are firmly distinguished from both P-consciousness and A-consciousness.
Self-consciousness #
By this term, I mean the possession of the
concept of the self and the ability to use this concept in thinking about
oneself. A number of higher primates
show signs of recognizing that they see themselves in mirrors. They display interest in correspondences
between their own actions and the movements of their mirror images. By contrast, dogs treat their mirror images
as strangers at first, slowly habituating.
In one experimental paradigm, experimenters painted colored spots on the
foreheads and ears of anesthetized primates, watching what happened. Chimps between ages 7 and 15 usually try to
wipe the spot off (Povinelli, 1994; Gallup, 1982). Monkeys do not do this, according to
published reports as of 1994. (Since then, Hauser et. al., 1995, have shown
that monkeys can pass the test if the mark is salient enough) Human babies don't show similar behavior
until the last half of their second year.
Perhaps this is a test for self-consciousness. (Or perhaps it is only a test for
understanding mirrors; but what is involved in understanding mirrors if not
that it is oneself one is seeing?) But even if monkeys and dogs have no
self-consciousness, no one should deny that they have P-conscious pains, or
that there is something it is like for them to see their reflections in the
mirror. P-conscious states often seem to
have a "me-ishness" about them, the phenomenal content often
represents the state as a state of me.
But this fact does not at all suggest that we can reduce P-consciousness
to self-consciousness, since such "me-ishness" is the same in states
whose P-conscious content is different.
For example, the experience as of red is the same as the experience as
of green in self-orientation, but the two states are different in phenomenal
feel.[15]
Monitoring-consciousness
The idea of consciousness as some sort of
internal monitoring takes many forms.
One notion is that of some sort of inner perception. This could be a form of P-consciousness, namely
P-consciousness of one's own states or of the self. Another notion is often put in
information-processing terms: internal scanning. And a third, metacognitive notion, is that of
a conscious state as one that is accompanied by a thought to the effect that
one is in that state.[16] Let
us lump these together as one or another form of monitoring-consciousness. Given my liberal terminological policy, I
have no objection to monitoring-consciousness as a notion of
consciousness. Where I balk is at the
idea that P-consciousness just is one or another form of
monitoring-consciousness.
To identify
P-consciousness with internal scanning is just to grease the slide to
eliminativism about P-consciousness.
Indeed, as Georges Rey (1983) has pointed out, ordinary laptop computers
are capable of various types of self-scanning, but as he also points out, no
one would think of their laptop computer as "conscious" (using the
term in the ordinary way, without making any of the distinctions I've
introduced). Since, according to Rey,
internal scanning is essential to consciousness, he concludes that the concept
of consciousness is incoherent. If one
regards the various elements of the mongrel concept that I have been
delineating as elements of a single concept, then that concept is indeed
incoherent and needs repair by making distinctions along the lines I have been
suggesting. I doubt that the ordinary concept
of consciousness is sufficiently determinate for it to be incoherent, though
whether or not this is so is an empirical question about how people use words
that it is not my job to decide. However
that inquiry turns out, Rey’s mistake is
to trumpet the putative incoherence of the concept of consciousness as if it
showed the incoherence of the concept of phenomenal
consciousness.[17]
Rosenthal
(1997) defines reflexive consciousness as follows: S is a reflexively conscious state of mine « S
is accompanied by a thought--arrived at non-inferentially and
non-observationally-- to the effect that I am in S. He offers this “higher
order thought” (HOT) theory as a theory of phenomenal consciousness. It is obvious that phenomenal consciousness
without HOT and HOT without phenomenal consciousness are both conceptually possible. For examples, perhaps dogs and infants have phenomenally
conscious pains without higher order thoughts about them. For the converse case, imagine that by
bio-feedback and imaging techniques of the distant future, I learn to detect
the state in myself of having the Freudian unconscious thought that it would be
nice to kill my father and marry my mother.
I could come to know—non-inferentially and non-observationally—that I
have this Freudian thought even though the thought is not phenomenally
conscious.
Rosenthal sometimes talks as if
it is supposed to be a basic law of nature that phenomenal states and HOTs
about them co-occur. That is a very adventurous claim. But even if it is true, then there must be a mechanism that explains
the correlation, as the fact that both heat and electricity are carried by free
electrons explains the correlation of electrical and thermal conductivity. But any mechanism breaks down under extreme
conditions, as does the correlation of electrical and thermal conductivity at
extremely high temperatures. So the
correlation between phenomenality and HOT would break down too, showing that higher
order thought does not yield the basic scientific nature of phenomenality.
Rosenthal’s
definition of his version of monitoring-consciousness has a number of ad hoc
features. “Non-observationally” is
required to rule out (e.g.) a case in which I know about a thought I have
repressed by observing my own behavior.
“Non-inferentially” is needed to avoid a somewhat different case in
which I appreciate (non-observationally) my own pain and infer a repressed
thought from it. Further, Rosenthal’s
definition involves a stipulation that the possessor of the monitoring-conscious
state is the same as the thinker of the thought—otherwise my thinking
about your pain would make it a conscious pain. All these ad hoc features can be eliminated
by moving to the following definition of monitoring-consciousness: S is a monitoring-conscious
state « S is
phenomenally presented in a thought about S.
This definition uses the notion of phenomenality, but this is no
disadvantage unless one holds that there is no such thing apart from monitoring
itself. The new definition, requiring
phenomenality as it does, has the additional advantage of making it clear why monitoring-consciousness
is a kind of consciousness.
There is an
element of plausibility to the collapse of P-consciousness into
monitoring-consciousness. Consider two dogs, one of which has a perceptual
state whereas the other has a similar perceptual state plus a representation of
it. Surely the latter dog has a
conscious state even if the former dog does not. Quite right, because consciousness of
plausibly brings consciousness with it. (I'm only endorsing the plausibility of
this idea, not its truth.) But the converse is more problematic. If I am conscious of a pain or a thought,
then, plausibly, that pain or thought has some P-conscious aspect. But even if consciousness of entails
P-consciousness, that gives us no reason to believe that P-consciousness
entails consciousness of, and it is the implausibility of this converse proposition
that is pointed to by the dog problem.
The first dog can have a P-conscious state too, even if it is not
conscious of it.
Perhaps you
are wondering why I am being so terminologically liberal, counting
P-consciousness, A-consciousness, monitoring consciousness and
self-consciousness all as types of consciousness. Oddly, I find that many critics wonder why I
would count phenomenal consciousness as consciousness, whereas many
others wonder why I would count access or monitoring or self
consciousness as consciousness. In fact
two reviewers of this paper complained about my terminological liberalism, but
for incompatible reasons. One reviewer
said: "While what he uses ["P-consciousness"] to refer to--the
"what it is like" aspect of mentality--seems to me interesting and
important, I suspect that the discussion of it under the heading
"consciousness" is a source of confusion...he is right to distinguish
access-consciousness (which is what I think deserves the name
"consciousness") from this."
Another reviewer said: "I really still can't see why access is
called...access-consciousness? Why isn't
access just...a purely information processing (functionalist)
analysis?" This is not a merely
verbal matter. In my view, all of us,
despite our explicit verbal preferences, have some tendency to use `conscious'
and related words in both ways, and our failure to see this causes a good deal
of difficulty in thinking about "consciousness".
I've been
talking about different concepts of "consciousness" and I've also
said that the concept of consciousness is a mongrel concept. Perhaps, you are thinking, I should make up
my mind. My view is that `consciousness'
is actually an ambiguous word, though the ambiguity I have in mind is not one
that I've found in any dictionary. I
started the paper with an analogy between `consciousness' and `velocity', and I
think there is an important similarity.
One important difference, however, is that in the case of `velocity', it
is easy to get rid of the temptation to conflate the two senses, even though
for many purposes the distinction is not very useful. With `consciousness', there is a tendency
towards "now you see it, now you don't." I think the main reason for this is that
P-consciousness presents itself to us in a way that makes it hard to imagine
how a conscious state could fail to be accessible and self-reflective, so it is
easy to fall into habits of thought that do not distinguish these concepts.[18]
The chief
alternative to the ambiguity hypothesis is that there is a single concept of
consciousness that is a cluster concept.
For example, a prototypical religion involves belief in supernatural
beings, sacred and profane objects, rituals, a moral code, religious feelings,
prayer, a worldview, an organization of life based on the world view and a
social group bound together by the previous items (Alston, 1967). But for all of these items, there are actual
or possible religions that lack them. For example, some forms of Buddhism do
not involve belief in a supreme being and Quakers have no sacred objects. It is convenient for us to use a concept of
religion that binds together a number of disparate concepts whose referents are
often found together.
The
distinction between ambiguity and cluster concept can be drawn in a number of
equally legitimate ways that classify some cases differently. That is, there is
some indeterminacy in the distinction.
Some might even say that velocity is a cluster concept because
for many purposes it is convenient to group average and instantaneous velocity
together. I favor tying the distinction
to the clear and present danger of conflation, especially in the form of
equivocation in an argument. Of course,
this is no analysis, since equivocation is definable in terms of
ambiguity. My point, rather, is that one
can make up one's mind about whether there is ambiguity by finding equivocation
hard to deny. In Block (1995), the
longer paper from which this paper derives, I give some examples of conflations.
When I
called consciousness a mongrel concept I was not declaring allegiance to
the cluster theory. Rather, what I had
in mind was that an ambiguous word often corresponds to an ambiguous mental
representation, one that functions in thought as a unitary entity and thereby
misleads. These are mongrels. I would also describe velocity and degree
of heat (as used by the Florentine Experimenters of the 17th Century) as
mongrel concepts. This is the grain of
truth in the cluster-concept theory.
Note the
distinction between the claim that the concept of consciousness is a mongrel
concept and the claim that consciousness is not a natural kind (Churchland,
1983, 1986). The former is a claim about the concept, one that can be verified
by reflection alone. The latter is like
the claim that dirt or cancer are not natural kinds, claims that require
empirical investigation.[19]
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[1] Abridged
(with changes by the author) from “On a Confusion about a Function of
Consciousness” in The Behavioral and Brain Sciences 18, 2, 1995 with
permission of the author and Cambridge University Press. I have changed only what seems mistaken even
from the point of view of my former position.
No attempt has been made to systematically update the references.
[2] But
what is it about thoughts that makes them P-conscious? One possibility is that it is just a series
of mental images or sub vocalizations that make thoughts P-conscious. Another possibility is that the contents
themselves have a P-conscious aspect independently of their vehicles. See Lormand, forthcoming and Burge, 1997.
[3] My
view is that although P-conscious content cannot be reduced to or
identified with intentional content, (at least not on relatively apriori
grounds) P-conscious contents often—maybe always--have an intentional aspect,
representing in a primitive non-intentional way.
[4] I
know some will think that I invoked inverted and absent qualia a few paragraphs
above when I described the explanatory gap as involving the question of why a
creature with a brain which has a physiological and functional nature like ours
couldn't have different experience or none at all. But the spirit of the question as I asked it
allows for an answer that explains why such creatures cannot exist, and thus
there is no presupposition that these are real possibilities.
[5] I
have been using the P-consciousness/A-consciousness distinction in my lectures
for many years, but it only found its way into print in my "Consciousness
and Accessibility" (1990), and my (1991, 1992, 1993). My claims about the distinction have been
criticized in Searle (1990, 1992) and Flanagan (1992)--I reply to Flanagan
below; and there is an illuminating discussion in Davies and Humphreys (1993b),
a point of which will be taken up in a footnote to follow. See also Levine's (1994) review of Flanagan
which discusses Flanagan's critique of the distinction. See also Kirk (1992) for an identification of
P-consciousness with something like A-consciousness.
[6] The full definition
was: A state is access-conscious if, in
virtue of one’s having the state, a representation of its content is (1)
inferentially promiscuous, that is,
poised for use as a premise in reasoning, (2) poised for rational control of
action, and (3) poised for rational control of speech.
[7] Dennett (1991) and Dennett
and Kinsbourne (1992) advocate the “multiple drafts” account of
consciousness. Dennett switched to the
cerebral celebrity view in his 1993 paper
[8] See Dennett (2001) and
Block (2001) for a more sophisticated treatment of this dialectic.
[9] Some
may say that only fully conceptualized content can play a role in reasoning, be
reportable, and rationally control action.
Such a view should not be adopted in isolation from views about which
contents are personal and which are sub-personal.
[10] The concept of P-consciousness is not a functional concept, however,
I acknowledge the empirical possibility that the scientific nature of
P-consciousness has something to do with information processing. We can ill afford to close off empirical
possibilities given the difficulty of solving the mystery of P-consciousness.
[11] The
distinction has some similarity to the sensation/perception distinction; I
won't take the space to lay out the differences. See Humphrey (1992) for an interesting
discussion of the latter distinction.
[12] If
you are tempted to deny the existence of these states of the perceptual system,
you should think back to the total zombie just mentioned. Putting aside the issue of the possibility of
this zombie, note that on a computational notion of cognition, the zombie has all
the same A-conscious contents that you have (if he is your computational
duplicate). A-consciousness is an
informational notion. The states of the
superblindsighter's perceptual system are A-conscious for the same reason as
the zombie's.
[13] Farah claims that blindsight is more degraded than sight. But Weiskrantz (1988) notes that his patient
DB had better acuity in some areas of the blind field (in some circumstances)
than in his sighted field. It would be
better to understand her "degraded" in terms of lack of access.
[14] Thus, there is a conflict between this physiological claim and the
Schacter model which dictates that destroying the P-consciousness module will
prevent A-consciousness.}
[15] See
White (1987) for an account of why self-consciousness should be firmly
distinguished from P-consciousness, and why self-consciousness is more relevant
to certain issues of value.
[16] The
pioneer of these ideas in the philosophical literature is David Armstrong
(1968, 1980). William Lycan (1987) has
energetically pursued self-scanning, and David Rosenthal (1986, 1993), Peter
Carruthers (1989, 1992) and Norton Nelkin (1993) have championed higher order
thought. Seealso Natsoulas (1993). Lormand (forthcoming) makes some powerful
criticisms of Rosenthal.
[17] To
be fair to Rey, his argument is more like a dilemma: for any supposed feature
of consciousness, either a laptop of the sort we have today has it or else you
can't be sure you have it yourself. In the case of P-consciousness, laptops
don't have it, and we are sure we do, so once we make these distinctions, his
argument loses plausibility.
[18] This
represents a change of view from Block, 1994, wherein I said that
`consciousness' ought to be ambiguous rather than saying it is now ambiguous.
[19] I
would like to thank Tyler Burge, Susan Carey, David Chalmers, Martin Davies,
Wayne Davis, Bert Dreyfus, Guven Guzeldere, Paul Horwich, Jerry Katz, Leonard
Katz, Joe Levine, David Rosenthal, Jerome Schaffer, Sydney Shoemaker, Stephen
White and Andrew Young for their very helpful comments on earlier versions of
this paper. I have been giving this
paper at colloquia and meetings since the fall of 1990, and I am grateful to
the many audiences which have made interesting and useful comments, especially
the audience at the conference on my work at the University of Barcelona in
June, 1993