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Eric LaRock, PhD
Assistant Professor of Philosophy
Philosophy Department
Oakland University
348 O’Dowd Hall
Rochester, MI 48309
[email protected]
Consciousness is not a Self-Scanning Mechanism: A Response to Armstrong
1. Introduction
Several contemporary philosophers think the best way to uncover the nature of mind is
through the empirical sciences. That is because, for many, it is not obvious that a priori
conceptual analyses alone could provide sufficient grounds to conclude in favor of either
materialism or dualism.1 We need to supplement our conceptual analyses with empirical
investigations to make headway on the reality of mind and its place in nature. Although
there are wide disagreements between theorists working on the nature of mind, especially
regarding the nature of consciousness, David Armstrong believes that a materialist view
of mind is gaining converts and will eventually become “scientific doctrine.”2 What does
Armstrong mean by a materialist view of mind? It is “the view that we can give a
complete account of man in purely physico-chemical terms.”3 Armstrong goes on to
assert that scientists and philosophers who resist this materialist view of mind “do so
primarily for philosophical, or moral or religious reasons, and only secondarily, and half-
1
For more on this issue, see Dean Zimmerman, “From Experience to Experiencer” and William
Hasker, “Souls Beastly and Human” in The Soul Hypothesis: Investigations into the Existence of
the Soul, ed. Mark Baker and Stewart Goetz (New York: Continuum Press, 2011).
2
David M. Armstrong, “The Nature of Mind” in Brian Cooney, The Place of Mind (Belmont:
Wadsworth, 2000), 136. I cite this version throughout. The preceding was originally published
in Armstrong’s The Nature of Mind and Other Essays (University of Queensland Press, St. Lucia,
Lld), 1980.
3
Ibid.
1
heartedly, for reasons of scientific detail.”4 Perhaps because Armstrong does not want to
appear too dogmatic, he goes on to acknowledge the possibility that empirical
investigations might reveal “new evidence and new problems” that will force advocates
of materialism to “reconsider the physico-chemical view of man.”5 Armstrong is
nevertheless convinced (on the basis of a vague reference to advances in molecular
biology) that empirically minded philosophers should join hands in formulating a theory
which maintains that mind is “nothing but a physico-chemical mechanism” that functions
to cause (and therefore explain) certain sorts of behavior, such as the behaviors involved
in distinguishing, recognizing and perceiving objects, as well as speaking, and any other
behavior animals (both human and nonhuman) are capable of performing.6 Compatible
with his broader logical, metaphysical, and commonsense commitments, Armstrong
maintains that mind plays a causal role in our cognitive and behavioral lives. In this strict
4
Ibid, pp. 136-137. Without getting hung up on this peripheral, yet controversial claim, it is
worth noting that the above claim is either fallacious or a reflection of ignorance, or both; for it
implicitly derides the intelligence of influential anti-materialists and furthermore fails to
acknowledge the possibility of formulating an empirically informed theory of mind other than
materialism. One might even interpret Armstrong to mean that science could only favor the
materialist hypothesis of mind. Even if Armstrong does not maintain such a narrow scope of the
role of scientific investigation, some contemporary materialists tend to express views along these
lines. For example, see Paul Churchland, Matter and Consciousness (Cambridge: MIT Press,
1984). Moreover, it is really hard to reconcile Armstrong’s characterization of those who resist
materialism with any influential, scientifically minded dualist, such as Charles Sherrington, John
Eccles, David Chalmers, William Hasker, and Dean Zimmerman. Why not suppose that a nonreductive approach to mind is positioned to take into account scientific details? See, for example,
David Chalmers, The Character of Consciousness (Oxford: Oxford University Press, 2010); also
Eric LaRock, Binding, Disambiguation, and the Unity of Consciousness, Theory & Psychology,
2007, 17, pp. 747-777; LaRock, Cognition and Consciousness: Kantian Affinities with
Contemporary Vision Research, Kant-Studien, 101, 2010, pp. 445-464.
5
Armstrong, p. 137.
6
Ibid, pp. 138-141. David Lewis is also a defender of the reductive causal view and cites
Armstrong approvingly. See David Lewis, “Mad Pain and Martian Pain” in Problems in mind,
ed. Jack Crumley II (Mountain View, CA: Mayfield, 2000), pp. 110-117. I cite this version
throughout. The preceding article by Lewis was originally published in Readings in Philosophy of
Psychology, volume I (pp. 216-222), edited by N. Block. Cambridge: Harvard University Press,
1980.
2
sense, Armstrong is like Descartes in that he too attributes causal power to the mind
itself; rightly so, they have no sympathies with theories that deny the reality of mental
causation, such as behaviorism and epiphenomenalism. Despite their allegiance to the
reality of mental causation, these two theorists differ quite radically about the ontology of
mind. Unlike Descartes’ stance on a variety of substance dualism, Armstrong believes
that every mental state can, and most likely will, be explained in terms of material states
without remainder; after all, a mental state is, for Armstrong, nothing but a cause in the
central nervous system that is capable of bringing about behavior.
Even though Armstrong argues primarily on conceptual grounds that his
materialism is explanatorily better than both classical and logical species of behaviorism,
he also acknowledges that any view that reduces mind to a material cause inevitably faces
a serious problem, what has become known as the hard problem of consciousness—the
problem of trying to accommodate first-person conscious mental phenomena within a
purely third-person, materialist explanatory framework.7 Armstrong’s purported solution
to this hard problem is to explain first-person conscious mental phenomena in terms of “a
self-scanning mechanism in the central nervous system.”8 He claims that this mechanism
is essentially a selective mechanism that enables an animal with perceptual capacities to
distinguish between the features of objects of any given visual scene, such as the kind of
selective behavior that would be required to distinguish between a green object and a red
object. After highlighting some of the positive aspects of Armstrong’s position, I present
7
Which is to say, once all of the structures and functions have been identified within a cognitive
system, there appears to be a further question: why should conscious experience accompany such
structures and functions in the first place? For the definitive formulation of the hard problem of
consciousness, see David Chalmers, “Facing Up to the Hard Problem of Consciousness,” Journal
of Consciousness Studies 2 (1995): 200-19; see also Chalmers’ The Character of Consciousness
(Oxford: Oxford University Press, 2010).
8
Armstrong, p. 143.
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an empirical case against Armstrong’s claim that consciousness is nothing but a selfscanning mechanism.
2. Classical and Logical Behaviorism
Armstrong finds classical and logical species of behaviorism implausible because both
entail the denial that mental states are the actual causes of behavior. Before examining
Armstrong’s case against behaviorism, it might be helpful to start by reflecting on a core
theoretical claim made by B.F. Skinner, a pioneering advocate of the classical behaviorist
view. Skinner claimed that, under the hypothesis of behaviorism, conscious mental states
are ultimately reducible to behavior: “We may take feeling to be simply responding to
stimuli.”9 This type of claim is compatible with reductive materialism in the philosophy
of mind, which maintains that all mental states can be accounted for in terms of material
states without remainder. Classical behaviorists supposed that once you have explained
the whole range of our behavioral lives, you have explained the whole range of our
mental lives. Armstrong provides a pithy summary of the philosophical upshot of
classical behaviorism: “Thought is not an inner process that lies behind, and brings about,
the words I speak and write: it is my speaking and writing. The mind is not an inner
arena, it is an outward act.”10 Because behavior is a type of material state, Skinner’s
claim is compatible with reductive materialism.
Though Armstrong takes a materialist stance about the nature of mind, he finds
classical behaviorism unsatisfying because it ultimately denies the reality of our common
experience of mental states independent of overt behavior: “One obvious difficulty is that
B.F. Skinner, Skinner, B. F. “About Behaviorism.” Selections reprinted in Problems in Mind,
ed. Jack Crumley (Mountain View: Mayfield, 2000), p. 62. Italics mine.
10
Armstrong, p. 138.
9
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it is our common experience that there can be mental processes going on although there is
no behavior occurring that could possibly be treated as expressions of those processes.”11
We might label this objection the mind without behavior objection. I can have a
conscious thought about eating an apple without actually eating an apple. We should not
underestimate the intuitive power of the forgoing objection. Armstrong suggests that the
mind without behavior objection is directly responsible for inspiring Ryle’s logical form
of behaviorism.
Under Ryle’s hypothesis of logical behaviorism, a mind can possess a mental
state, such as a disposition, without at the same having to manifest that disposition in the
form of behavior. Thus a mind can have mental states independent of behavior. For
example, Smith can possess a disposition of anger without acting angrily. But had you
said one more insulting word to Smith, he would have burst out in anger. Whereas
classical behaviorism sought to define the mental in terms of the behavioral, logical
behaviorism provides room for talk about the mental in both dispositional and behavioral
terms.
Armstrong points out, however, that the trouble for logical behaviorism is that it
defines dispositions too weakly. A disposition, on the logical behaviorist’s account, is
simply a liability or tendency that is manifested when a specific stimulus is present; a
disposition, by Ryle’s lights, is not a state that causes behavior: “To possess a
dispositional property is not to be in a particular state, or to undergo a particular change;
it is to be bound or liable to be in a particular state, or to undergo a particular change,
when a particular condition is realized.”12 For example, if an individual possesses the
11
12
Ibid.
Gilbert Ryle, The Concept of Mind. (New York: Barnes and Noble, 1949), p. 43. Italics mine.
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disposition to laugh, and the relevant external condition is brought about, then the
individual will laugh. For example, if Cherry were to hear just one more joke about the
Oompa Loompas’ song and dance, then she would erupt in laughter. One more joke was
uttered and Cherry burst out in laughter. Any behavioral-hypothetical suggests that
specific environmental conditions play the role of eliciting responses. Even though
common sense might tempt one to think that Rylean advocates of logical behaviorism
could assign causal power to mental dispositions, this would be a mistake because Ryle,
much like Skinner, winds up denying the existence of mental states as the actual causes
of behavior. Fodor’s concise observation is relevant here: “Logical behaviorism is just
radical behaviorism in semantic form. . . . What does not really exist cannot cause
anything, and the logical behaviorist, like the radical behaviorist, believes deep down that
mental causes do not exist.”13
Having examined why Armstrong and others find both classical and logical
species of behaviorism to be less than satisfying materialist accounts of mind, we are now
positioned to consider Armstrong’s central state materialist approach to mind.
3. Armstrong’s Central State Materialism
In contrast to logical behaviorism’s weak notion of dispositions, Armstrong argues that
dispositions are not mere liabilities understood in terms of a behavioral-hypothetical, but
are instead conceived as the actual states that lie behind and cause behavior: “Perhaps
mind can be defined not as behavior, but rather as the inner cause of certain ranges of
behavior. Thought is not speech under suitable circumstances; rather it is something
Jerry Fodor, “The Mind-Body Problem” in Problems in Mind, ed. Jack Crumley (Mountain
View: Mayfield, 2000), p. 121.
13
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within the person that, in suitable circumstances, brings about speech.”14 Armstrong
offers a theory of mental causation that agrees with our introspective intuitions about the
mind in relation to behavior: minds (or mental states) are causally involved in producing
behavior. For example, Stevo perceives the cobra and jumps back because he sees the
cobra is striking. He jumps back because he believes that cobras are dangerous and
furthermore desires to preserve his life. Stevo’s perceptions, beliefs, and desires—his
mental states in general—are the actual causes of his jumping.
Armstrong recognizes that an analysis of dispositions as the inner causes of
behavior does not exclusively warrant materialist conclusions. For if we suppose that our
language is topic-neutral about the mental, any description of mind as the inner cause of
behavior would be logically compatible with Cartesian and certain other non-reductive
accounts of mind. In this way Armstrong acknowledges that dualism accords with
common sense about mental causation as well. But Armstrong argues that if language is
topic neutral about the nature of the mental, then dispositions, as the inner causes of
behavior, are at least compatible with materialism; after all, central state materialism says
that neural events occupy the appropriate causal role of mental states (dispositions),
which are the sole causes of behavior. Armstrong then claims that since science favors
materialism, mental states are probably identical to material states (i.e., internal causes of
a material system) of the central nervous system: “the verdict of modern science seems to
be that the sole cause of mind-betokening behavior in man and the higher animals is the
physico-chemical workings of the central nervous system.”15 Armstrong reduces (or
identifies) mental states to nothing but the cause of specific sorts of behavior. In order to
14
15
Armstrong, p. 140.
Ibid.
7
clarify the concept of a disposition in a scientifically acceptable manner, Armstrong
points out that, unlike the behaviorist who has denied that a disposition is a state internal
to a system, modern science describes dispositions as actual states of systems (e.g., the
weak molecular bonds of a vase make the vase brittle). In the case of brittle glass and
elastic rubber, the modern scientist will say the following:
Faced with the phenomenon of breakage under relatively small impacts, or the
phenomenon of stretching when a force is applied followed by contraction when
the force is removed, he will assume that there is some current state of the glass
or the rubber that is responsible for the characteristic behavior of samples of these
two materials.16
In the case of brittle glass, brittleness is understood to be a specific molecular pattern
possessed by the glass. It is a pattern of the glass itself; thus, when struck lightly, the
molecular pattern is causally involved in the glass’s shattering. If dispositions are
understood as actual states of material systems, Armstrong reasons that we can infer that
dispositions are “actual causes, or causal factors . . . A certain molecular constitution of
glass that constitutes its brittleness is actually responsible for the fact that, when the glass
is struck, it breaks.”17 Analogously, mental dispositions function as the inner causes of
behavior: “mind is nothing but that of an inner principle apt for bringing about certain
sorts of behavior.”18 Because an explanation of mental dispositions can be shown to be
consistent with science, Armstrong concludes that his central state materialist (CSM)
theory of mind is scientifically plausible and superior to both logical behaviorism (LB)
and Cartesian dualist theory (CDT). At this stage in the analysis, it might be useful to
provide a clear summary of Armstrong’s argument:
16
Ibid.
Ibid.
18
Ibid, p. 141.
17
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1. A theory of mind is scientifically plausible only if mind is the cause of behavior. (The
assumption is that scientific explanations are causal explanations.)
2. If LB is scientifically plausible, then mind is the cause of behavior.
3. LB contends that mind is not an internal state that causes behavior (but only a liability
or tendency).
4. Therefore, LB is not scientifically plausible.
5. Mind is the cause of behavior on the CSM theory.
6. Mind is also the cause of behavior on the CDT. (The assumption is that our language
about mind is topic-neutral and thus compatible with both CSM and CDT.)
7. The verdict of modern science favors CSM over CDT.19
8. Therefore, CSM is scientifically plausible (and superior to LB and CDT).
4. CSM and the Problem of Consciousness
Armstrong recognizes that the character of conscious experience is a serious problem for
his own theory. Analyzing mind in terms of an internal material cause alone coheres with
a third-person form of analysis but is nonetheless logically compatible with the absence
of a first-person perspective:
Now can we say that to be conscious, to have experiences, is simply for
something to go on within us apt for the causing of certain sorts of behavior?
Such an account does not seem to do any justice to the phenomena. And so it
seems that our account of the mind, like Behaviorism, will fail to do justice to the
first-person case.20
A purely physico-chemical explanation can get along just fine without ever mentioning a
first-person point of view. One rightly wonders how Armstrong can accommodate firstperson phenomena within his purely third-person, reductive causal account of mind.
Armstrong proposes that first-person consciousness is ultimately a higher order function
of perception: consciousness refers to a “self-scanning mechanism in the central nervous
19
There are many more dualisms than Cartesian style dualism, some of which are empirically
motivated, and it is far from clear that the verdict of modern science favors materialism. For
example, see Chalmers 2010; Hasker 2011; Zimmerman 2011. See also my 2007, 2010.
20
Armstrong, p. 142.
9
system.”21 The idea is that some part (or process) of the central nervous system scans
another part (or process).
Armstrong claims that the self-scanning mechanism is essentially a selective
mechanism that enables an animal with perceptual capacities to distinguish between the
features of objects of any given visual scene, such as the kind of selective behavior that
would be required to distinguish between a green object and a red object: “We can think
of the animal’s perception as a state within the animal apt . . . for selective behavior
between the red-and green-lighted pathways.”22
5. Appraising Armstrong’s Hypothesis
Though Armstrong formulates a logical analysis of consciousness that is compatible with
central state materialism, one could fill in the details with recent findings in neuroscience
about the role that selective neuronal behavior plays in relation to distinguishing an
object’s features when two or more objects comprise a visual scene. For example, if a
visual scene were comprised of a red square (RS) and a blue triangle (BT), selective
neuronal behavior would somehow have to assign features to the right objects. For if the
neurons that fire in response to RS and BT were to fire at the same time, the brain might
easily confuse the features of objects, such that the square would be seen as blue and the
triangle as red. In order to explain how we consciously perceive the features of
competing objects in a reliable way, there must be a higher order form of selective
neuronal behavior that functions to assign features to the right objects. This notion of
higher-order selective behavior is commonly thought to be carried out by the neuronal
21
22
Ibid, p. 143.
Ibid.
10
mechanisms of top-down selective attention and is discussed in a vast literature pool in
the neurosciences.23
For our purposes, the critical question concerns whether consciousness is nothing
but an activity of the neuronal mechanisms of top-down selective attention. Some of the
experimental work of Anne Treisman and colleagues is useful here. In one experimental
set-up, individuals were briefly shown two colored letters at the same time: a green T and
a red O. The experimenters found that when top-down selective attention was prevented
by means of a brief presentation of the letters, individuals would nonetheless experience
illusory conjunctions: the individuals reported seeing “a red T when a green T and a red
O” were presented at the same time.24 Consequently, red, rather than green, was bound to
T and the result was an experience of illusory conjunctions. Several inferences can be
drawn from this study. First, consciousness is not reducible to the mechanisms of topdown selective attention on grounds that conscious states can emerge without the
deployment of the mechanisms of top-down selective attention. Second, binding features
to form a unified object of consciousness (even if the feature-unified object in question
does not reflect the correct features) can occur without the deployment of the neuronal
mechanisms of top-down selective attention. Thus object-feature binding per se is not
reducible to activities carried out by the mechanisms of top-down selective attention.
What functional role do the mechanisms of top-down selective attention perform?
They perform the role of disambiguating the features of objects when competition arises
23
For more on this issue, see Francis Crick, The Astonishing Hypothesis (New York: Charles
Scribner’s Sons, 1984). See also LaRock, Why Neural Synchrony Fails to Explain the Unity of
Visual Consciousness, Behavior and Philosophy, 2006, 34, pp. 39-58.
24
Anne Treisman (2003). “Consciousness and perceptual binding,” in The
Unity of consciousness: Binding, integration, and dissociation, ed. Axel
Cleeremans (Oxford: Oxford University Press, 2003), p. 99.
11
in the cortical hierarchy.25 Thus what Armstrong proposes for an account of the
metaphysics of consciousness is really an account of the epistemology of consciousness:
the neuronal mechanisms of top-down selective attention explain how our cognitive
systems function to assign features to the correct objects.
Fine, the materialist might say. Perhaps all we mean by consciousness is an
ability to carry out some epistemic function, such as the ability to recognize an object. As
David Lewis remarks, “knowing what it’s like is the possession of abilities: abilities to
recognize, abilities to imagine, abilities to predict one’s behavior by means of
imaginative experiments.”26 We might call this Lewis’ attempt to shore up the
weaknesses in CSM. Lewis does after all characterize his own view regarding the nature
of consciousness as consistent with, and an expression of, CSM.27
I think there is important empirical evidence to the contrary. For instance, recent
neuropsychological evidence has shown that persons who undergo damage in the inferior
temporal lobe (or IT) wind up with associative agnosia disorder, the inability to recognize
objects. Even though associative agnostics can no longer recognize objects, they can
nevertheless see them.28 The following is an example of an elderly man diagnosed with
this type of agnosia:
A sixty-year old man . . . woke from a sleep unable to find his clothes, though they
lay ready for him close by. As soon as his wife put the garments into his hands, he
recognized them, dressed himself correctly, and went out. In the streets he found he
could not recognize people—not even his own daughter. He could see things, but not
tell what they were.29
25
See my 2006, 2007, 2010.
Lewis, p. 116.
27
Ibid.
28
For example, see Martha Farah, Visual agnosia: Disorders of object recognition and what they
tell us about normal vision (Cambridge: MIT Press, 1990). See also Steven Kosslyn and Olivier
Koenig, Wet Mind: The New Cognitive Neurosciences (New York: Free Press, 1995).
29
Michael Critchley, The Parietal Lobes. (London: Edward Arnold, 1953), p. 289.
26
12
Although he could not recognize objects, he could see them. This suggests that
consciousness cannot be adequately explained in terms of certain abilities, such as the
ability to recognize. Therefore, Lewis’s attempt to solve the problem of consciousness in
terms of abilities is less than convincing. One might also say, in light of Chalmers’
distinction between hard versus easy problems, that the scope of Lewis’s purported
solution to the problem of consciousness is, at best, consistent with a solution to one of
the easy problems of consciousness (e.g., the problem of recognition); but no solution to
an easy problem entails a solution to the hard problem. Hence, what Lewis (and by
logical extension, Armstrong) sets out to explain and what he actually explains are not
the same.
Finally, one could motivate a conceptually-based objection that would apply to
any brand of reductive materialism through the conceivability of a philosophical
zombie.30 But for those adopting an empirical approach to the problem of consciousness,
a philosophical zombie might not be the most appealing concept. That does not mean
that a zombie concept might not be useful to the empirical sciences in some sense. For
example, what if we inverted the characteristics of a philosophical zombie? Let us call
such a creature an inverse zombie. An inverse zombie would have none of the behavioral
characteristics and responses of a philosophical zombie, but would nevertheless be
conscious. Inverse zombies are not only conceivable; they actually exist: for example,
individuals who experience “anesthesia awareness” fall into such a category. From an
external observer perspective, these patients appear unconscious during general
30
A philosophical zombie is an imaginary creature that is physically, functionally, structurally,
and behaviorally identical to any human being with one exception: it has no conscious
experience. See David Chalmers, The Conscious Mind (Oxford: Oxford University Press, 1996).
13
anesthesia. However, in 1 to 2 out of a 1000 cases, patients under general anesthesia may
be aware of intraoperative events, and sometimes without any objective indices.31
The application of an inverse zombie to our current discussion could go as
follows. Armstrong claims that “mind is nothing but that of an inner principle apt for
bringing about certain sorts of behavior.”32 Now if Armstrong’s causal reductive
hypothesis is feasible, then knocking out the mechanisms that are apt to cause certain
sorts of behavior would involve knocking out the person’s conscious mind. However, in
inverse zombie cases, the mechanisms that are apt to cause behavior are knocked out and
yet the person is still consciousness.
One could provide further support to this empirically based counterexample by
simply noting that persons who suffer from a severe form of locked-in syndrome (also
known as total locked in syndrome) can no longer bring about certain sorts of behavior
because the mechanisms that are apt for causing certain sorts of behavior are no longer
apt for causing certain sorts of behavior (due to chronic motor deficits); yet persons who
are locked-in their brains are still conscious of what is going on in the strongest and most
literal sense.33
See also George Mashour & Eric LaRock, “Inverse Zombies, Anesthesia Awareness, and the
Hard Problem of Unconsciousness,” Consciousness and Cognition, 2008, 17, pp. 1163-1168;
LaRock, “The Philosophical Implications of Anesthesia Awareness,” in Consciousness,
Awareness, and Anesthesia, ed. George Mashour (Cambridge: Cambridge University Press,
2010).
32
Armstrong, p. 141.
33
See G. Bauer, F. Gerstenbrand, and E. Rumpl, “Varieties of the Locked-in Syndrome,” Journal
of Neurology, 1979, vol. 221: pp. 77-91; E. Smith and M. Delagy, “Locked-in syndrome,” British
Medical Journal, 2005, vol. 330: pp. 406-409; S. Laureys, A. Owen, and N. Schiff, “Brain
Function in Coma, Vegetative State, and Related Disorders,” Lancet Neurology, 2004, 3: pp. 537546; See also Antti Revonsuo, Consciousness: The Science of Subjectivity. New York:
Psychology Press, 2010.
31
14