Consciousness in Action
Harvard University Press (1998) ISBN: 0674164202

by Susan L. Hurley
Department of Philosophy
University of Warwick (UK)

Introduction: The Reappearing Self


1. The plot

Perception and action are more deeply interdependent than we usually assume. As well as having empirical implications, this interdependence has consequences for philosophical issues: about the unity of consciousness, relations between mind and world, self-consciousness, cognition, behaviorism, etc. This general theme is developed by these essays on various aspects of consciousness and agency. While they can be read separately, if the essays are read in sequence the attentive reader will discern an overall plot and several subplots.
        
The place of mind and its norms in the natural world has long seemed problematic. But finding a satisfactory conception of relations between mind and world is made more difficult by a certain tendency of thought. This is the tendency to regard perception and action as buffer zones mediating between mind and world. We tend to think of perception as input from world to mind and action as output from mind to world. This Input-Output Picture of perception and action may hold in place traditional worries about the mind's place in the world, as well as more specific philosophical assumptions. If perception is input from the world to the mind and action is output from the mind to the world, then the mind as distinct from the world is what the input is to and what the output is from. So, despite the web of causal relations between organisms and environments, we suppose the mind must be in a separate place, within some boundary that sets it apart from the world.
        
In trying to understand the mind's place in the world, we thus study the function from input to output, especially the way central nervous systems process and transform inputs to human organisms. We argue about whether central cognitive processes must have a language-like structure that explains the conceptual structure of thought. But we tend to ignore the function from output back to input, and the way environments, including linguistic environments, transform and reflect outputs from the human organism. The two functions are not only of comparable complexity, but are causally continuous. To understand the mind's place in the world, we should study these complex dynamic processes as a system, not just the truncated internal portion of them.
        
People and other animals with minds can be seen at one level as dynamic singularities: structural singularities in the field of causal flows characterized through time by a tangle of multiple feedback loops of varying orbits. Consider the circus performer who puts the handle of a dagger in her mouth, tips her head back, balances a sword by its point on the point of the dagger, and with the whole kit balanced above her head magisterially climbs a ladder, swings her legs over the top rung, and climbs back down the other side of the ladder. Each move she makes is both the source of and exquisitely dependent on multiple, internal and external, channels of sensory and motor-signal feedback, the complex calibrations of which have been honed by years of practice. An only slightly less intricate structure of dynamic feedback relations knits the nervous system of a normally active organism into its environment. This is what the contents of the creature's interdependent perceptions and intentions both depend on. The whole complex dynamic feedback system includes not just functions from input to output, but also feedback functions from output to input, some internal to the organism, others passing through the environment before returning. As a result, external states can be needed to explain patterns of activity at the body surface, even if what is to be explained is not identified in terms of external states. The dynamic singularity is centred on the organism and moves through environments with the organism, but it itself has no sharp boundaries.
        
The dynamic singularity conception is at the subpersonal level. We should not confuse different levels of conceptualization: the subpersonal level of causal processes on which mind depends with the personal level of normatively constrained mental contents. When we conceive of intentional agents at the personal level, we think about the relations between what they perceive and intend, what they believe and desire, and try to make sense of them as acting for reasons, though of course allowing for irrationality and mistakes. By contrast, causal explanations in neurophysiological or computational terms describe subpersonal mechanisms and functions. The personal level contents of mental states can be seen as carried by such subpersonal processes, or vehicles of content. But the properties of subpersonal processes, of vehicles of content, cannot simply be projected into personal level mental content, or vice versa. These different ways of looking at and describing an organic system need not display isomorphisms or map onto one another in any simple way. As with emergent properties of dynamic feedback systems in general: Significant qualitative differences at one level may depend on minor quantitative differences at the other level. Discontinuities, intricate or salient structure at one level may be invisible at the other.
        
But the Input-Output Picture does confuse levels. It confuses the subpersonal-level distinction between causal input and causal output with the personal-level distinction between perception and action. Or at least it maps these two distinctions onto one another in an overly simply way. Consider instead the view that the contents of perceptual experience and intentional action both depend on a structure of causal flows that constitutes a complex dynamic feedback system. In other words, both depend on relations between inputs and outputs. This provides a two-level account of the interdependence of perception and action that is characteristic of having a perspective. It corrects the buffer zone view: the picture of perception as input and action as output. Perception and action can be more intimately related to one another than that picture allows. Neuropsychology provides examples that illustrate and support this correction.
        
The main plot in a nutshell is this. It will be argued that the unity of consciousness has both normative, personal-level and subpersonal aspects. The relations between these levels can be approached via the closely related but more general idea of a perspective: the interdependence of perception and action that perspective involves can be explained in terms of their co-dependence on a subpersonal dynamic singularity. This subpersonal aspect of unity does not support sharp causal boundaries either between mind and world or between perception and action. Moreover, it can provide an antidote to the inward retreat of the mind in modern philosophy. At the personal level, the self does not lurk hidden somewhere between perceptual input and behavioral output, but reappears out in the open, embodied and embedded in the world.
        
These themes are developed in two parts. The first part focuses on the unity of consciousness, and the second on the relations between perception and action. We'll preview the two parts in a bit more detail, and then several of the subplots. For ease of reference, terms and phrases that play an important role in the essays will be highlighted here as they are briefly and informally explained.
        The essays need not be read in the order presented. Those wishing to dip into the book rather than read it straight through should use the analytical table of contents to choose according to their interests while also getting a sense of the context provided by other essays. So that the essays can be read separately, some arguments and examples are repeated in different essays. However, several of the longer essays have been divided into parts, which are not intended to be self-standing. The book as a whole is written for an interdisciplinary audience, and some elements of it are likely to be more accessible to philosophers and others to scientists. Readers with one background should understand that some passages may be directed to readers with a different background, and read accordingly. Philosophers may find the degree of detail in discussion of empirical examples and related thought experiments too great, but scientists may find it helpful. Scientists may wish to skip over stretches of unrelieved philosophical argument (especially in essays 2, 3, 6, 7) and may find the discussion of detailed examples and of empirical work of more interest (especially in essays 5, 9, 10).

2. Part 1: The unity of consciousness and action

Some conscious states occupying the same stretch of time are together, while others are separate. While I talk to you, I see your face and hear my own voice. These experiences are together or united within one consciousness. But you also hear my voice, and your experience is separate from mine. This is an easy case. But what is it for simultaneous conscious states to be united or separate? Can we find a principled account of the unity of consciousness at a time that will also apply to hard cases? Or are there just various differences between the cases, no right answers in some cases, and no unified phenomenon of 'the unity of consciousness'? (Essays 2, 3, 5)
        
Kantian and neo-Kantian arguments make it difficult to account for the unity of consciousness in either of two ways. In the Critique of Pure Reason Kant argues that the unity of consciousness cannot be understood in terms of the contents of experience. But he also argues, in effect, that it cannot be understood in terms of the unity of the self as a thing in itself either. This Kantian dilemma has a modern descendant: there are difficulties for both subjective and objective accounts of the unity of consciousness. (Essay 2)
        
According to a traditional understanding of the subjective realm, the contents of consciousness are in principle independent of the external world. Such a view is vulnerable to the 'just-more-content' argument: the unity or separateness of consciousness cannot be accounted for in terms of the subjective contents of consciousness, because the same question of unity or separateness arises again for any such contents. An objective account is needed. If there has to be an answer to the question about whether conscious states at a given time are united or separate, then the subjective realm is not in principle self-sufficient. We can consider whether consciousness could be only partially unified, so that state 1 might be co-conscious with state 2 and state 2 with state 3 even though states 1 and 3 were not co-conscious. But even if we think such partial unity of consciousness makes sense, it turns out that an objective account is still needed. (Essays 2, 3)
        
When we conceive of intentional agents at the personal level, we make sense of what they do holistically: in terms of the relations between what they perceive and intend, or what they believe and desire. What action a perception leads to depends on the contents of the agent's intentions, and vice versa. We also consider the consistency of someone's various perceptions and beliefs, or various intentions and desires. Of course people can be irrational. But we make sense of their irrationality against a background of normative assumptions. Relations between the contents of mental states such as perceptions and intentions are constrained, at least weakly, by norms, such as norms of consistency and instrumental rationality. If such norms are violated too radically, we begin to lose our grip on why the behavior in question counts as an expression of the mental states of an intention agent at all.
        
Norms of consistency at the level of content play an important role in the unity of consciousness. In some cases and under certain assumptions, inconsistent contents can imply disunity. But a normative approach to unity can only provide part of the needed objective account, since consistency is not sufficient for unity: the contents of separate conscious states can be consistent with each other. We can indeed make sense of complete duplication of content in separate centers of consciousness, and norms of consistency could not account for their separateness. Some further component of an objective account is needed. (Essay 3)
        
Neither the contents of consciousness nor the norms of consistency governing contents fully account for unity. Perhaps we should look instead to subpersonal level for the needed further component of an objective account. But now we run into another difficulty. We should not confuse the unity of consciousness with the unity of subpersonal vehicles of consciousness. We cannot simply project properties or structures present at one level onto the other level. There need not be a spatiotemporally unified locus within the brain of unified consciousness, and neuroanatomical structure may not be isomorphic with the structure of consciousness. Unity might take various neurophysiological forms. (Essays 1, 5)
        
Given the difficulties with both subjective and objective accounts of the unity of consciousness, we get both a clue and a lesson from reconsidering the Kantian dilemma. Kant tries to slip between the two horns of this dilemma by accounting for unity in terms of a special sense of self-consciousness--"transcendental apperception". This is neither consciousness of an empirical self as represented in experience, nor consciousness of the self as a thing in itself. Rather, it is consciousness of the possibility of spontaneous conceptualizing activity. The clue is that the unity of consciousness may essentially involve activity in some way. It is wrong to think of perceptual consciousness as passively receptive. The lesson is that much turns on how the receptive and active elements of consciousness are distinguished. Intentional actions raise all the same issues about content and unity that perceptual experiences do. By appealing to intentional activity in an account of the unity of consciousness we run the danger of merely relocating but not solving the problem.
        
How can this danger of regress be avoided, while recognizing the essentially active nature of perception? The distinction between perception and action applies at the personal level. The distinction between input and output applies at the subpersonal level. These are both good distinctions, but we should not project them onto one another by assuming that perception is input from world to mind and action is output from mind to world, as in the buffer zone view. Nor should we simply take the content and unity of intentions for granted in explaining the content and unity of experiences.
        
But consider instead the possibility that the contents of experiences and intentions are both functions of a complex dynamic system of relations between input and output, including both internal and external feedback loops. This could explain the interdependence of perception and action, which is part of what it is to have a perspective: some of the ways in which what you experience and perceive depends systematically on what you do, as well as vice versa. (Essays 2, 4, 5)
        
Such a Two-Level Interdependence View can avoid the danger of regress. It can also avoid the danger of confusing properties of subpersonal vehicles of content with properties of content. So it could in principle contribute to understanding how the needed subpersonal component in an account of the unity of consciousness could avoid this danger. Suppose that content is a function of (or, if you prefer, supervenes on, or is determined by, or depends constitutively on) various causal processes. These may include not just internal vehicles of content, but also external states and causal processes. Content may be a function of distributed as well as local processes, of relations within the organism or between organism and environment as well as of intrinsic properties of discrete neural structures.
        
However, which function of these factors determines content cannot simply be read off from the properties of subpersonal vehicles. This is the confusion of levels we're trying to avoid (though without denying that there is anything to be said about how the levels might be related). Emergence can be unpredictable. And different types of content, such as the contents of perceptions and the contents of intentions, might be different functions of the same system of causal relations: different contents can be superposed on the same network of relations. Which functions of these relations fix contents of certain types could depend on still broader causal processes, such as evolution, which explain why any subpersonal vehicles of a certain type, or any mental states of a certain type, exist at all.
        
However, we are now in a position to see how a Two-Level Interdependence View can explain the interdependence of perception and action without confusing the personal and subpersonal levels. If the contents of perceptions and of intentions are different functions of the same system of relations, then as a purely logical matter a given change in those relations could in principle affect both the contents of perceptions and of intentions. There could be interference or 'crosstalk' between perception and action, as is found when different contents are superposed on the same neural network (essays 1, 10). This phenomenon could have beneficial functions. But for now what matters is that this reasoning does not confuse properties of subpersonal vehicles with properties in content, or assume that content is a transparent function of subpersonal properties. We can respect the distinction between the personal and subpersonal levels while saying something about the relations between them.
        
The general idea of such a Two-Level Interdependence View can be made more specific by considering the role of motor-to-sensory feedback in various empirical cases. In some cases, the unity of perceptual consciousness may vary with the content of simple motor intentions even when sensory inputs are constant. These cases both challenge the Input-Output Picture and suggest that the unity of consciousness may involve feedback. (Essay 5)
        
Could the functional idea of a complex dynamic feedback system provide the needed further component of an objective account of unity? To understand the unity of consciousness we may need to understand the interdependence of perception and action involved in having a perspective. This is the topic of the essays in the second half of the book.

3. Part 2: The interdependence of perception and action

How are states of the external world and the contents of the mind related? A traditional view, often associated with the influence of Descartes, is that mental content is in principle independent of the world or autonomous ('narrow'). Some modern views deny this, and hold that content is world-involving or context-dependent ('wide'). The traditional view of content generates skeptical worries about how knowledge of the world is possible: why couldn't our beliefs about the external world be rampant delusions produced by mad scientists manipulating our brains? By contrast, views of content as world-involving can be seen to emerge from worries about how content itself is possible. For it even to be possible that our beliefs are mistaken, they must be about something in particular, must have determinate content. But in virtue of what could they count as having any particular content, if not their relations to the world? Wittgenstein's later work is sometimes interpreted in this way. (Essays 6, 7)
        
Consider the traditional view that the contents of the mind are in principle independent of the world, so that we might be systematically deluded. If dualism is ruled out, it is natural to understand this view as holding, first, that internal physical states fix mental contents (Internalism) and, second, that it makes sense in principle to suppose that internal physical states can be duplicated in systematically different environments (the Duplication Assumption). This yields the possibility of systematic delusion: mental contents can be duplicated in different environments. (Essay 8)
        
Two kinds of thought experiment are often used in current discussions of relations between mind and world. Inverted Earth arguments compare two situations that duplicate the internal physical states of an organism but in which states of the external world are different. For example, everything red on Earth may be green on Inverted Earth and vice versa. But red objects produce the same internal physical states in the Earthling that green objects produce in his Twin. The question is whether the mental contents of the Earthling and his Twin must also be duplicated in these two situations. If content is narrow or autonomous, it must be. If content is world-involving or context-dependent, it may not be. The answer may depend on whether we are talking about qualitative or representational content. (Essays 7)
        
Inverted Qualia arguments compare two situations that duplicate an organism's relations to states of the external world in relevant respects but in which the internal physical states of the organisms are different. For example, red objects may produce different internal physical states in two people even though the two types of state play exactly the same functional role for them in their environments. Despite the difference in their internal physical states, both people may call just red things 'red', and so on. The question is whether their mental contents are fixed by these duplicated environmental relations and functions, or could vary with internal physical states. Could these two people mean different things by 'red'? Could they experience red things differently: say, could one see green where the other sees red? A traditional view is that such inverted qualia do indeed make sense. (Essay 7)
        
Such thought experiments provide a framework for much current debate about relations between mind and world. Both types of thought experiment can be (but aren't usually) applied to questions about the content of intentional actions, as well as the content of perceptual experience. But note that this framework involves certain assumptions, even before the question is resolved about whether content is world-involving or autonomous. One type of thought experiment supposes internal physical states can in principle be duplicated though relations to the environment are not; the other supposes environmental relations can in principle be duplicated though internal physical states are not. Note also that scientists are often uncomfortable or impatient with these thought experiments. Philosophers tend to dismiss this reaction as failing to understand the conceptual point of the thought experiments. But the unease may itself have a deeper conceptual point.
        
This framework begins to unravel when we consider cases involving spatial perceptions and intentions. Instead of inverted red and green, for example, we could invert or distort spatial features. We now find systematic interdependencies between perception and action, and dynamic feedback from output back to input, which are characteristic of what it is to have a perspective. These create difficulties of principle for the Duplication Assumption made in Inverted Earth thought experiments. For example, it is hard to make sense of an active, perspective-bearing creature whose central nervous system could be dynamically duplicated in certain spatially distorted environments. The difficulties are not merely technical, curable by more philosophical imagination or a bit of science fiction. The interdependence of spatial perceptions and intentions for an active creature sets limits in principle to the creation of virtual reality. And because this point is a consequence of something basic about having a perspective, its implications are not confined to spatial cases.
        
It is no accident that the same dynamic feedback factors that make trouble for the Duplication Assumption in spatial Inverted Earth cases also conflict with the Input-Output Picture. The picture of perception as input from world to mind and action as output from mind to world reinforces the assumption that at least the vehicles of mental contents must be internal and bounded: what input is to and output is from. We need a different way of challenging the view that the mind is in principle independent of the world, one not wedded to this picture. (Essay 8)
        
Neuropsychology can help to undermine the Input-Output Picture as a general conceptual framework for thinking about perception and action. For this purpose we need to turn ourselves through ninety degrees in thinking about content: to focus on relations between input and output rather than on relations between internal and external states. In effect, we shift from scrutiny of the Cartesian mind/world cut to scrutiny of the Humean perception/action cut. There is much scientific interest these days in the idea of active perception, but the philosophical import of this idea is often vague or elusive. The ninety-degree shift provides one way of making the idea of active perception operational for philosophical purposes. It provides an explicit framework for understanding the philosophical relevance of empirical work and related thought experiments. We can understand this new framework by comparison with the standard framework.
        
First, recall that in Inverted Earth cases we suppose internal physical states are duplicated while external relations vary, and we then consider whether content is fixed by internal physical states. When we make the ninety-degree shift, we suppose instead that inputs are duplicated while outputs vary, and then consider whether perceptual content is fixed by inputs or can vary with relations of fixed input to output. That is, can perceptual distinctions depend noninstrumentally on output?
        
Note that the challenge to the input-output picture requires a distinction between instrumental and noninstrumental dependence. For example, it is obvious that perceptual content can vary with output that in turn has an effect on input: If I move around the corner I will see something I cannot see from where I am. This kind of dependence of perceptual content on output is merely instrumental. It operates via changes in input; changes in output are a means to changes in input. This is not surprising and does not challenge the input-output picture. By contrast, noninstrumental dependence of perceptual content on output does not operate via input, but directly. For example, perceptual distinctions may depend on outputs even though inputs are fixed. A simple illustration of how this might happen is the alleged paralyzed eye phenomenon. Suppose my eye muscles are paralyzed so that my eye cannot move. I try to move my eyes sideways but fail, so input to my retina does not change. And no other inputs change. Nevertheless, I may have a visual experience as of the world shifting sideways.
        
Second, recall that in Inverted Qualia cases, we suppose internal physical states vary while external relations and functions are fixed, and we then consider whether content is fixed by external relations and functions. We can again shift to consider the orthogonal situation: we can suppose inputs vary while relations to output are fixed, and then ask whether perceptual invariances can depend on relations to output when input varies.
        
Reciprocal moves can be made concerning distinctions and invariances in the content of basic intentions. In effect, we consider how the Input-Output Picture may fail for distinctions and for invariances in the contents of perceptual experiences and of intentions.
        
This four-box approach can be used to analyze and interpret various empirical (and related hypothetical) cases. These concern unilateral neglect (neglect of the left half of the world, including their own bodies, by otherwise normal people), adaptation to left-right reversing and color-distorting spectacles, the use of tactile stimulation to substitute for visual stimulation in blind patients, the acquisition of control over bodily and brain processes through biofeedback, the reacquisition of bodily control after deafferentation, and so on. Intuitively, these cases have something in common; they are surprising in a similar way.
        
A diagnosis of this intuition is that they show, in various ways, how the Input-Output Picture might fail to hold. We tend to assume this picture as a general conceptual framework: witness the common phrase "perceptual input, behavioral output". But these cases suggest we should not, which is why they are surprising. Some cases illustrate how perceptual distinctions and invariants might depend noninstrumentally on output. Others show how distinctions and invariants in the contents of basic intentions might depend noninstrumentally on input. While some of the cases can be interpreted to fit the Input-Output Picture, it is an empirical question whether this account applies in particular cases. (Essay 9)
        
A different general conceptual framework is needed, which admits the Input-Output Picture as an empirical account in particular cases. Generically, we need a Two-Level Interdependence View; the input-output view can then been seen as a limiting case of nil interdependence. This generic view can be filled out by appeal to the idea of a complex dynamic feedback system.
        
Consider different ways of departing from the dominant tradition in studies of perception and action. The dominant tradition has an old-fashioned, sexist view of the marriage of perception and action. They are separate but unequal: perception is primary, the husband; action is derivative, the wife. We should distinguish two aspects of this tradition. The first is a primarily linear or one-way view of the causal flow: in from the world through sensory systems to perception to cognition to motor systems to action and finally out to the world again. The second is a view of perception and action as merely instrumentally related: perception is seen as a means to action and action a means to perception.
        
We can depart from the tradition in either or both of these respects. But rejecting either aspect of the dominant tradition while retaining the other aspect is unsatisfactory.
        
'Output-side' views of perception such as behaviorism depart from the instrumental but not the one-way aspect of the traditional view. Behaviorism gives no special role to feedback or the dynamically loopy character of causal flows: it casts actions as output. But it does view action as constitutively related to perception. This combination leaves behaviorism open to the objection that it is verificationist: that it collapses the distinction between perceptual experiences and their effects in action, effects that are merely evidence for perceptual experience, not constitutive of it.
Ecological or Gibsonian views of perception depart from the one-way view, but not the instrumental view. They emphasise the dynamic loopiness of the causal flows that make for perception: the importance of sensory feedback from movement. Nevertheless, Gibson insisted that passive movement would do as well as active: the role of feedback was merely instrumental, in that action merely provided a means to higher-order patterns of input. Perception and action are interdependent, on his view, but merely instrumentally interdependent.
        
By contrast, consider a pair of views that can make both moves away from the traditional view. First, they emphasize dynamic feedback. Second, they show how perception and action might in some cases be constitutively interdependent, not merely instrumentally. These two views are the motor theory of perception and the control systems theory of action as the control of perception. These theories fit together, in that they both appeal to dynamic systems in which feedback has a complex role: it may in principle operate both instrumentally and constitutively, and both externally and internally. The combination of these theories yields the view that perception and action both depend on relations between input and output: a version of the Two-Level Interdependence View. Perceptual distinctions and invariants and basic intentional distinctions and invariants emerge together from the complex dynamic system and constrain one another. To describe such a system as perceiving is to describe it as functioning to represent; to describe it as acting is to describe it as functioning to control. But these are different ways of describing the same complex system. And such a system's functions of representation and control do not in general map tidily onto a distinction between input and output.
        
This is an improvement on both of the one-sided departures from the separate-but-unequal tradition. It shows how, despite their rivalry, ecological and motor theories of perception can benefit from one another's insights. And it avoids standard objections to behaviorism: perception and action can be constitutively related without threatening the holism of the mental. (Essay 10)

4. Some subplots.

Some themes are repeated with variations and cross-referencing in different essays, but are not treated comprehensively in one place. Other themes are present only implicitly. A few of these subplots are sketched here, to help see their relationship to the main plot. The sketches below use broad strokes and don't provide fully argued positions. Rather, they may consolidate points scattered about the essays or fill in suggestions or implicit context.

5. Divide and conquer?

We are not trying to produce a grand unified theory of consciousness. Indeed, there is room for skepticism about whether there is a grand unified problem of consciousness. Our approach is rather to break consciousness down into aspects and address those. Perhaps a view of consciousness as a whole can be built up by considering the relationships between these various aspects of it. There are lots of different issues about consciousness. Here are four broad categories of issues.

    A. What does the presence or absence of consciousness consist in? What is it for states to be conscious or not? Under this heading philosophers wonder: Could there be zombies, who are just like people except that their 'mental states' are not conscious? If a system has the right structure of functional relations, is it thereby conscious, or does it matter what materials the system is made of? What work does consciousness do? What evolutionary function might it have? Is it dispensable in science?

    B. What is it for conscious states to be like they are, of the phenomenal types they are? What is it to be whatever it is like to be a bat, or for pain to be like pain, or for something to look like red things look rather than like green things look? How is phenomenal type related to representational type?

    C. What is it for consciousness to be unified at a time?

    D. What is self-consciousness? Does consciousness require self-consciousness? Are there varieties of self-consciousness? Does self-consciousness require conceptual abilities?

Instead of hammering at the front door of the difficult issues about presence or absence, maybe we can slip round the back. Maybe if we begin with issues about unity and self-consciousness, we will end up learning something about phenomenal types and even the presence or absence of consciousness. But we should not assume that the problems of consciousness will fall like a row of dominoes. We should tease issues apart and create a network of small insights. Perhaps together they may impose some overall order on the subject matter. But the correct view may be eclectic and messy. It may have components drawn from traditionally opposed camps, such as normative and functional components. Different aspects of consciousness may require different theoretical tools. We can't rule out in advance the possibility that consciousness organizes itself out of disparate and ill-assorted materials, and that there is no independently discernable overall structure from which its various attributes can be derived.

6. Parallels, myths, and a new angle

Perception and action can be regarded as parallel and isomorphic though separate systems, with different directions of 'fit' to the world. The parallels between them provide ways of elaborating the view of perception and action as buffer zones around the self, which interfaces between input and output. But as we follow perception and action further inward, the self seems always to recede.
        
It can be illuminating to pursue the parallels. Consider the parallel inward retreats of knowledge and of responsibility. Philosophers are often wary of the Cartesian supposition that we only know for certain the contents of our own experiences. They are less often wary of the Kantian supposition that we are only truly responsible for the contents of our own intentions. Yet the effect of luck in contracting the scope of responsibility can be seen as parallel to the effect of the skeptic's hypotheses in contracting the scope of knowledge. (Essay 7)
        
Following the parallels through can also help to see what is wrong with the Input-Output Picture. By taking a new angle on perception and action we allow the self to reappear in the world, where it seemed to be to start with.
        
Consider the "myth of the given": the conception of perceptual experience as the given, as reflecting pure input from world to mind with no active contribution from the perceiver. Both Kant and Wittgenstein reject this idea. Both emphasize, though in different ways, the contribution of our activity to what we experience. Kant appeals to the spontaneity of synthesis in explaining the unity of consciousness and conceptual unity ('combination does not ... lie in the objects'). Wittgenstein appeals to the role of our practices in determining meaning and content ('this is what we do'). Their rejections of the given have profoundly influenced the modern doctrine that the way content classifies the world is 'up to us', not exogenously fixed but a result of our conceptualizing activity.
        
But let's now follow the parallels through. Consider such conceptualizing activity. Is it intentional agency or not?
        
If it is, what should be said about the contents of conceptualizing intentions? How are they determined? A regress lurks. We should not suppose appealing to agency gets beneath the issues about content and unity, as if agency were a matter of pure output from mind to world. We can call this the myth of the giving. It is just as much a mistake as the myth of given, the idea of perceptual experience as pure input. The issues about content and unity arise equally for the contents of intentions. Agency may depend on perception as deeply as perception depends on agency.
        
On the other hand, if intentional agency is not at issue, in what sense are classification and conceptualization up to us? Only in the sense that they result from events and processes that occur in our bodies? They also result from events and processes that occur in the world outside our bodies.
        
Up-to-us doctrines run a danger: the danger of recoiling from a conception of experience as "the given" into an equally mistaken conception of agency. Both myths should be avoided. The revolution that began with Kant's arguments about perceptual experience should be carried through to agency. Action is no more pure output than perception is pure input. The whole of the Input-Output Picture should be rejected, not just half of it. (Essays 2, 6)
        
We get a new angle by making the ninety-degree shift: by making the focus of our scrutiny the perception/action cut rather than the mind/world cut. The constitutive interdependence of perception and action when both depend on complex dynamic feedback systems has several consequences. At the subpersonal level of causal flows, the dynamic singularity matters but the significance of boundaries like the skin or the skull fades. At the personal level of mental content, however, the inward retreat of the self is preempted. Perception and action are not buffer zones around the mind. The self is out in the open, where it seems to be. And both myths are avoided. Perception and action are mutually and symmetrically dependent. (Essays 8, 9, 10)
        
This new angle also brings the philosophical relevance of results in neuropsychology into relief. Various empirical cases suggest the constitutive interdependence of perception and action. But we observe something striking. The action in question in these cases is not spontaneous conceptualizing or pure content-establishing activity: not the fancy kind of action that runs the myth of the giving danger. It is simple, real-world, motor action, contentful in a way that is in turn dependent on perceptual capacities. It is this kind of action that is the essential partner of perception. (Essays 8, 9)
It is a mistake to get sophisticated about experience while remaining naive about action. Someone who wouldn't be caught dead thinking of the content of perceptual experience as autonomous rather than world-involving might well still think of the content of intentions in this way. That makes it easy to make another mistake, which encourages idealism and relativism: to think the kind of activity experience depends on is the fancy, mythical, content-establishing kind. The interdependence of perception and real-world action offers no such encouragement.
        
Conceptualizing is not something we must do in order to experience or think or do anything else, but is a fairly sophisticated activity. What happens in our brains to make perception, action, and conceptualization possible is not necessarily something we do. To the extent the conceptualization of information in experience is something we do, as opposed to something that happens partly in us, we do it by acting in the world, often by linguistic action, but not by acting in a ghostly precontentful kind of way somewhere in our brains. For example, I may point to some architectural details and ornaments in a baroque church and say to a friend: "You can see those lines as Art Nouveau".

7. Perspective and access: self-consciousness, conceptual abilities, agency, and life

Does consciousness require self-consciousness? Self-consciousness is usually thought of as conceptual in character. But conceptual abilities aren't necessary for consciousness, for example, in nonhuman animals. Perhaps consciousness may involve forms of self-consciousness that do not require conceptual abilities. (Essay 4)
        
Consider perspectival self-consciousness. Having a perspective means in part that what you experience and perceive depends systematically on what you do, as well as vice versa, and that you can keep track of some of the ways in which this is so, even if not in conceptual terms. In this sense having a perspective involves self-consciousness. A conscious animal, moving through its environment, has the ability to keep track of relationships between what it perceives and what it does. This ability enables it to use information about itself and its own states and activities as well as information about its environment to meet its needs. It doesn't follow that it has the ability to reason systematically about aspects of itself, others, and the environment in a variety of ways detached from its needs. Its abilities need not have the generality, richly normative character, and systematic decompositional and recombinant structure of conceptual abilities. Perspectival self-consciousness may but need not involve conceptual abilities.
        
Consider also self-consciousness in the sense of access to the contents of conscious states. For people with conceptual abilities, it is arguable that consciousness requires self-consciousness in the sense of self-evidence: cognitive access to the contents of conscious states. But even for creatures without conceptual abilities, consciousness may require self-consciousness in a weaker sense of access, intentional access to the contents of conscious states. Intentional access is closely related to the ability to use information explicitly, an ability that is missing in various examples of covert processing, such as blindsight. Intentional access to content requires the ability to form an intention whose content is provided by certain information and to act on it just for the reason that information provides.
        
If a creature without conceptual abilities can have intentions and act for reasons, it can have intentional access to contents and perspectival self-consciousness. Intentional agency occupies a kind of normative middle ground. It is not mere response to stimulus. It requires at least rudimentary practical rationality, holistic relationships between perceptions and intentions, and weak normative constraints on contents. But the richly structured constraints and inferential norms associated with conceptual abilities go well beyond this.
        
What light do the notions of perspective and access shed on the relations among conceptual abilities, intentional agency, life, consciousness, and self-consciousness? Life appears to be doubly dissociable from intentional agency understood in normative terms, as above. Though both are alive, animals may be intentional agents while plants are not. Robots might be intentional agents, even if they were not alive and their contentful states were not conscious. Both perspective and access to content involve agency, but not necessarily conceptual abilities. For creatures with conscious states, both perspective and access to content may count as forms of self-consciousness. But even if both are necessary for consciousness, neither perspective nor access to content seem to be sufficient for consciousness. It seems that a robot could have both, yet be a "zombie" without conscious states. Could adding in conceptual abilities keep such zombie worries at bay? Or, could it be sufficient for consciousness that a living thing have both perspective and access to content?

8. Vehicles, contents, and boundaries

We should distinguish properties represented in content from properties of vehicles of content: the subpersonal states or processes that carry content. In particular, we should distinguish the personal and subpersonal levels of conceptualization. The contents of the mental states of subjects/agents are at the personal level. Vehicles of content are causally explanatory subpersonal events or processes or states. We shouldn't suppose that the properties or relations of vehicles must be projected into the personal-level contents they carry, or vice versa. This would be to confuse the personal and subpersonal levels. Nevertheless, there may be something to be said about the relations between the processes that determine mental contents and the processes that carry mental content.
        
These distinctions are familiar in various applications. Several further applications are made in the essays.
        
First, to the unity of consciousness. We shouldn't suppose the structure of content, in particular its unity, is isomorphic with the structure of vehicles of content. A unified consciousness need not depend on neuroanatomical unity, and neuroanatomical unity doesn't rule out splits in consciousness. Yet the concept of a subpersonal dynamic singularity may contribute to an account of the unity of consciousness.
        
Second, to the relations between perception and action. The Input-Output Picture confuses the personal-level distinction between perception and action with the subpersonal-level distinction between input and output. This is kin to vehicle/content confusions. Yet the interdependence of the contents of perceptions and intentions may reflect their superposition on the same complex network of dynamic relations. (Essays 1, 5, 8, 9)
        
A third application of the vehicle/content distinction is also relevant, though less of a focus in these essays. But we can use it to illustrate points made in various essays and to suggest how they might be related and further developed. The cognitive abilities of persons display generality and systematicity; content at the personal level has decompositional, recombinant conceptual structure. What explains this structure at the level of subpersonal processing? In particular, must subpersonal vehicles of conceptual content themselves have a language-like or syntactic structure, so that structure in personal-level content is explained by isomorphic subpersonal structure?
        
Their answers to this last question distinguish classical, 'language of thought' approaches to cognitive architecture from connectionist approaches. Classicists answer yes, on either a priori or empirical grounds, while connectionists allow that it may be possible to explain conceptually structured cognitive abilities in terms of neural networks without syntactic structure. The assumption that the processes that support true thought must have a classical architecture (even if they are implemented by a connectionist network) imposes a isomorphism requirement. (Essay 10)
        
Might our conception of ourselves as genuine thinkers impose this constraint on relations between levels? If the conceptual structure of content were not explained by isomorphic subpersonal structure, would displays of 'cognitive ability' be mere patterns of behavior, mere mimicry of true thought? This is another category of zombie worry, this time about thought rather than consciousness. So some argue that if connectionism does give the right account of supposed cognitive abilities, then true thought is eliminated.
        
Much here turns on two questions. First, should the isomorphism requirement be applied, if at all, to what explains particular thoughts and particular displays of cognitive ability, or to what explains why any thought content or cognitive ability of a given type exists at all? Vehicles of content explain tokens: particular thoughts on particular occasions. They are token-explanatory processes. But if the isomorphism requirement holds at all, does it apply to token-explanatory processes or to type-explanatory processes, which explain why a certain type of content exists at all? (Essay 8)
        
Second, must whatever explains conceptually structured cognitive abilities for purposes of the isomorphism requirement be internal? Or can it be world-involving? Can the requirement of isomorphism be satisfied relationally, by processes or states that cross the boundary between organism and environment? If it can be, does it matter whether it is satisfied all over again internally?
        
This second question takes two forms, as applied to type-explanatory and to token-explanatory processes. The answer to the first is obvious. Type-explanatory processes can be world-involving: consider upbringing, linguistic practices, evolution, and so on. These are often appealed to in accounts of what determines content. The answer to the second is less obvious. Could token-explanatory vehicles of content also be world-involving, relational states of persons? Could processes that carry content, as opposed to those that determine content, go external or relational? Arguments against (as well as for) Internalism about what determines content typically presuppose Internalism about what carries content, or vehicles. But is this presupposition of Vehicle Internalism justified?
        
There is nothing spooky about relational properties of persons: they correspond to intrinsic properties of something bigger where causality reigns as usual. Context-dependence is relative to a boundary. We are used to the idea of relations internal to a nervous system as vehicles: relations between events in a distributed process within the brain need not be monitored by a single cell or local module. Such internal relations themselves may be the vehicles of content, rather than the intrinsic properties of some internal monitor of these relations. But if internal relations can qualify as vehicles, why not external relations? Given a continuous complex dynamic system of reciprocal causal relations between organism and environment, what stops the spread? The idea that vehicles might go external takes the notion of distributed processing to its logical extreme. (Essay 8)
        
The isomorphism requirement is usually applied to internal, token-explanatory vehicles of content. But might the intuition that genuine thought requires an isomorphism between the level of content and the level of causal explanation instead be captured by appealing to external, type-explanatory processes? Perhaps this intuition can be satisfied by a whole system, including embedding linguistic environment, even if it is not satisfied by internal vehicles. (Essay 10)

9. The classical sandwich vs. horizontal modularity

A view of perception and action as separate input and output systems compliments a view of thought and cognition as 'central' and in turn separate from the 'peripheral' input and output systems. The virtual processing of cognition is seen as central, even if its implementation is distributed; input to it is provided by perception, and it issues output that generates action. The subpersonal underpinnings of the mind are conceived as vertically modular, with cognition interfacing between perception and action. Against this background, a standard view is that connectionist approaches are at their strongest for the peripheral processes (e.g. sensorimotor control, pattern recognition), but that the central cognitive interface must have classical structure.
        
This classical sandwich conception can be attacked from the center, by arguing against the view that true thought requires isomorphic structure among the internal vehicles of thought. But such attacks often accept the conception of perception and action as peripheral buffer zones, which holds the central interface conception of cognition in place. Another way to undermine the classical sandwich is to attack from the outside, as it were: to challenge the buffer zone view and the separation of perception and action from central cognitive processes.
        
The two angles of attack can be complementary and mutually supporting. Traditional presuppositions about the separateness of perception and action may hold other philosophical assumptions in place. To illustrate this suggestion very briefly, consider first the assumption that the mind decomposes vertically so that cognitive processes are central and distinct, and second the assumption of a dichotomy between internal classical structure and behaviorism.
        
First, we've seen that the Input-Output Picture runs together the personal-level distinction between perception and action and the subpersonal-level distinction between input and output. By contrast, a Two-Level Interdependence View sees perception and action is as interdependent because co-dependent on a complex dynamic system of causal relations, which may extend into the environment. On such a view, instead of seeing the mind as vertically modular we can see it as horizontally modular. Each horizontal module or layer is a content-specific system that loops dynamically through internal sensory and motor processes well as through the environment.
        
This change may help to understand how the conceptual structure of cognition might emerge from dynamic sensorimotor systems and the role environmental structure might have in such systems, even in the absence of internal isomorphic structure. Complex dynamic systems can have very striking emergent properties. Indeed, emergence in complex dynamic systems could be argued to underlie and explain the vehicle-content distinction. An essential lesson we learn from studying such systems is that discontinuities and structure at a higher level can emerge unpredictably (though deterministically), with no isomorphism at the underlying level.
        Such emergent structure could register in evolutionary and cultural processes. A horizontal module might couple perception and action together in specific ways that are functional or adaptive in certain conditions: consider imitation. However, considered in isolation such a specific coupling might be too inflexible to respect the holism of the mental and the constraints of rationality. But just evolution and culture might select specific layers, they might also twist the layers together into still more complex systems that display further, qualitatively novel structure. Rational flexibility and cognitive structure might emerge from intricate higher-order relations of inhibition and facilitation between horizontal layers. But damage to these higher-order relations might reveal the underlying horizontal structure, in the form of various neuropsychological pathologies and dissociations. (Essays 5, 10)
        
Second, recall the zombie worry about 'cognitive abilities' without explanatory, classically structured internal vehicles. This worry can be encouraged by a spurious dichotomy: either the right explanatory internal structure, or mere mimicry, mere patterns of behavior. The Input-Output Picture supports this dichotomy by type-casting behavior, including linguistic behavior, in the role of effect and ignoring its other talents. As the mere effect of thought, behavior is merely evidence for thought. So worries about behaviorism and verificationism get started.
        
The change from the Input-Output Picture to a Two-Level Interdependence View can underscore the obvious but neglected point that to participate in natural language is to perceive and to act, and depends on sensory-motor interactions with linguistic environments. Behavior, including linguistic behavior, is as much cause as effect within a complex dynamic feedback system; it is not merely evidence for something else that's doing the work. (Essay 10)

10. Affinities and implications

Decentralization, self-organizing systems, context-dependence, feedback, emergence: these are themes of some fascinating current work in cognitive science and related disciplines. The sketched subplots have clear affinities with developments in connectionism, dynamic systems theory, artificial life, as well as evident antecedents in cybernetics. These essays can be seen as a philosophical complement, and bridge, to this work in other disciplines. But this book develops these shared themes relatively independently, beginning (at least) from mainstream philosophical concerns, and it puts primary emphasis on their relevance to consciousness rather than to cognition. By tracing continuities that may not be apparent on the surface, I hope this book may help to bring mainstream analytical philosophy into fruitful contact with this work in other disciplines.
        
The Input-Output Picture that is here criticized has had significant implicit influence in ethics. Large questions for further thought are these: What are the implications for ethics, and for social and political philosophy, if this view can not be justified? More generally, to what extent should these normative subjects be studied in ways that are relatively insulated from our advancing understanding, both empirical and theoretical, of the mind?

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