斯坦福哲学百科全书词条：意识（1）
Consciousness
First published Fri Jun 18, 2004; substantive revision Tue Jan 14, 2014
Perhaps no aspect of mind is more familiar or more puzzling than consciousness and our conscious experience of self and world. The problem of consciousness is arguably the central issue in current theorizing about the mind. Despite the lack of any agreed upon theory of consciousness, there is a widespread, if less than universal, consensus that an adequate account of mind requires a clear understanding of it and its place in nature. We need to understand both what consciousness is and how it relates to other, nonconscious, aspects of reality.
1. History of the issue
2. Concepts of Consciousness
2.1 Creature Consciousness
2.2 State consciousness
2.3 Consciousness as an entity
3. Problems of Consciousness
4. The descriptive question: What are the features of consciousness?
4.1 First-person and third-person data
4.2 Qualitative character
4.3 Phenomenal structure
4.4 Subjectivity
4.5 Self-perspectival organization
4.6 Unity
4.7 Intentionality and transparency
4.8 Dynamic flow
5. The explanatory question: How can consciousness exist?
5.1 Diversity of explanatory projects
5.2 The explanatory gap
5.3 Reductive and non-reductive explanation
5.4 Prospects of explanatory success
6. The functional question: Why does consciousness exist?
6.1 Causal status of consciousness
6.2 Flexible control
6.3 Social coordination
6.4 Integrated representation
6.5 Informational access
6.6 Freedom of will
6.7 Intrinsic motivation
6.8 Constitutive and contingent roles
7. Theories of consciousness
8. Metaphysical theories of consciousness
8.1 Dualist theories
8.2 Physicalist theories
9. Specific Theories of Consciousness
9.1 Higher-order theories
9.2 Reflexive theories
9.3 Representationalist theories
9.4 Narrative Interpretative Theories
9.5 Cognitive Theories
9.6 Information Integration Theory
9.7 Neural Theories
9.8 Quantum theories
9.9 Non-physical theories
10. Conclusion
Bibliography
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1. History of the issue
Questions about the nature of conscious awareness have likely been asked for as long as there have been humans. Neolithic burial practices appear to express spiritual beliefs and provide early evidence for at least minimally reflective thought about the nature of human consciousness (Pearson 1999, Clark and Riel-Salvatore 2001). Preliterate cultures have similarly been found invariably to embrace some form of spiritual or at least animist view that indicates a degree of reflection about the nature of conscious awareness.
Nonetheless, some have argued that consciousness as we know it today is a relatively recent historical development that arose sometime after the Homeric era (Jaynes 1974). According to this view, earlier humans including those who fought the Trojan War did not experience themselves as unified internal subjects of their thoughts and actions, at least not in the ways we do today. Others have claimed that even during the classical period, there was no word of ancient Greek that corresponds to “consciousness” (Wilkes 1984, 1988, 1995). Though the ancients had much to say about mental matters, it is less clear whether they had any specific concepts or concerns for what we now think of as consciousness.
Although the words “conscious” and “conscience” are used quite differently today, it is likely that the Reformation emphasis on the latter as an inner source of truth played some role in the inward turn so characteristic of the modern reflective view of self. The Hamlet who walked the stage in 1600 already saw his world and self with profoundly modern eyes.
By the beginning of the early modern era in the seventeenth century, consciousness had come full center in thinking about the mind. Indeed from the mid-17th through the late 19th century, consciousness was widely regarded as essential or definitive of the mental. René Descartes defined the very notion of thought (pensée) in terms of reflexive consciousness or self-awareness. In the Principles of Philosophy (1640) he wrote,
By the word ‘thought’ (‘pensée’) I understand all that of which we are conscious as operating in us.
Later, toward the end of the 17th century, John Locke offered a similar if slightly more qualified claim in An Essay on Human Understanding (1688),
I do not say there is no soul in man because he is not sensible of it in his sleep. But I do say he can not think at any time, waking or sleeping, without being sensible of it. Our being sensible of it is not necessary to anything but our thoughts, and to them it is and to them it always will be necessary.
Locke explicitly forswore making any hypothesis about the substantial basis of consciousness and its relation to matter, but he clearly regarded it as essential to thought as well as to personal identity.
Locke's contemporary G.W. Leibniz, drawing possible inspiration from his mathematical work on differentiation and integration, offered a theory of mind in the Discourse on Metaphysics (1686) that allowed for infinitely many degrees of consciousness and perhaps even for some thoughts that were unconscious, the so called “petites perceptions”. Leibniz was the first to distinguish explicitly between perception and apperception, i.e., roughly between awareness and self-awareness. In the Monadology(1720) he also offered his famous analogy of the mill to express his belief that consciousness could not arise from mere matter. He asked his reader to imagine someone walking through an expanded brain as one would walk through a mill and observing all its mechanical operations, which for Leibniz exhausted its physical nature. Nowhere, he asserts, would such an observer see any conscious thoughts.
Despite Leibniz's recognition of the possibility of unconscious thought, for most of the next two centuries the domains of thought and consciousness were regarded as more or less the same. Associationist psychology, whether pursued by Locke or later in the eighteenth century by David Hume (1739) or in the nineteenth by James Mill (1829), aimed to discover the principles by which conscious thoughts or ideas interacted or affected each other. James Mill's son, John Stuart Mill continued his father's work on associationist psychology, but he allowed that combinations of ideas might produce resultants that went beyond their constituent mental parts, thus providing an early model of mental emergence (1865).
The purely associationist approach was critiqued in the late eighteenth century by Immanuel Kant (1787), who argued that an adequate account of experience and phenomenal consciousness required a far richer structure of mental and intentional organization. Phenomenal consciousness according to Kant could not be a mere succession of associated ideas, but at a minimum had to be the experience of a conscious self situated in an objective world structured with respect to space, time and causality.
Within the Anglo-American world, associationist approaches continued to be influential in both philosophy and psychology well into the twentieth century, while in the German and European sphere there was a greater interest in the larger structure of experience that lead in part to the study of phenomenology through the work of Edmund Husserl (1913, 1929), Martin Heidegger (1927), Maurice Merleau-Ponty (1945) and others who expanded the study of consciousness into the realm of the social, the bodily and the interpersonal.
At the outset of modern scientific psychology in the mid-nineteenth century, the mind was still largely equated with consciousness, and introspective methods dominated the field as in the work of Wilhelm Wundt (1897), Hermann von Helmholtz (1897), William James (1890) and Alfred Titchener (1901). However, the relation of consciousness to brain remained very much a mystery as expressed in T. H. Huxley's famous remark,
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 the Djin, when Aladdin rubbed his lamp (1866).
The early twentieth century saw the eclipse of consciousness from scientific psychology, especially in the United States with the rise of behaviorism (Watson 1924, Skinner 1953) though movements such as Gestalt psychology kept it a matter of ongoing scientific concern in Europe (Köhler 1929, Köffka 1935). In the 1960s, the grip of behaviorism weakened with the rise of cognitive psychology and its emphasis on information processing and the modeling of internal mental processes (Neisser 1965, Gardiner 1985). However, despite the renewed emphasis on explaining cognitive capacities such as memory, perception and language comprehension, consciousness remained a largely neglected topic for several further decades.
In the 1980s and 90s there was a major resurgence of scientific and philosophical research into the nature and basis of consciousness (Baars 1988, Dennett 1991, Penrose 1989, 1994, Crick 1994, Lycan 1987, 1996, Chalmers 1996). Once consciousness was back under discussion, there was a rapid proliferation of research with a flood of books and articles, as well as the introduction of specialty journals (The Journal of Consciousness Studies, Consciousness and Cognition, Psyche), professional societies (Association for the Scientific Study of Consciousness—ASSC) and annual conferences devoted exclusively to its investigation (“The Science of Consciousness”).
2. Concepts of Consciousness
The words “conscious” and “consciousness” are umbrella terms that cover a wide variety of mental phenomena. Both are used with a diversity of meanings, and the adjective “conscious” is heterogeneous in its range, being applied both to whole organisms—creature consciousness—and to particular mental states and processes—state consciousness (Rosenthal 1986, Gennaro 1995, Carruthers 2000).
2.1 Creature Consciousness
An animal, person or other cognitive system may be regarded as conscious in a number of different senses.
Sentience. It may be conscious in the generic sense of simply being a sentient creature, one capable of sensing and responding to its world (Armstrong 1981). Being conscious in this sense may admit of degrees, and just what sort of sensory capacities are sufficient may not be sharply defined. Are fish conscious in the relevant respect? And what of shrimp or bees?
Wakefulness. One might further require that the organism actually be exercising such a capacity rather than merely having the ability or disposition to do so. Thus one might count it as conscious only if it were awake and normally alert. In that sense organisms would not count as conscious when asleep or in any of the deeper levels of coma. Again boundaries may be blurry, and intermediate cases may be involved. For example, is one conscious in the relevant sense when dreaming, hypnotized or in a fugue state?
Self-consciousness. A third and yet more demanding sense might define conscious creatures as those that are not only aware but also aware that they are aware, thus treating creature consciousness as a form of self-consciousness (Carruthers 2000). The self-awareness requirement might get interpreted in a variety of ways, and which creatures would qualify as conscious in the relevant sense will vary accordingly. If it is taken to involve explicit conceptual self-awareness, many non-human animals and even young children might fail to qualify, but if only more rudimentary implicit forms of self-awareness are required then a wide range of nonlinguistic creatures might count as self-conscious.
What it is like. Thomas Nagel's (1974) famous“what it is like”criterion aims to capture another and perhaps more subjective notion of being a conscious organism. According to Nagel, a being is conscious just if there is “something that it is like” to be that creature, i.e., some subjective way the world seems or appears from the creature's mental or experiential point of view. In Nagel's example, bats are conscious because there is something that it is like for a bat to experience its world through its echo-locatory senses, even though we humans from our human point of view can not emphatically understand what such a mode of consciousness is like from the bat's own point of view.
Subject of conscious states. A fifth alternative would be to define the notion of a conscious organism in terms of conscious states. That is, one might first define what makes a mental state a conscious mental state, and then define being a conscious creature in terms of having such states. One's concept of a conscious organism would then depend upon the particular account one gives of conscious states (section 2.2).
Transitive Consciousness. In addition to describing creatures as conscious in these various senses, there are also related senses in which creatures are described as being conscious of various things. The distinction is sometimes marked as that between transitive and intransitive notions of consciousness, with the former involving some object at which consciousness is directed (Rosenthal 1986).
2.2 State consciousness
The notion of a conscious mental state also has a variety of distinct though perhaps interrelated meanings. There are at least six major options.
States one is aware of. On one common reading, a conscious mental state is simply a mental state one is aware of being in (Rosenthal 1986, 1996). Conscious states in this sense involve a form of meta-mentality or meta-intentionality in so far as they require mental states that are themselves about mental states. To have a conscious desire for a cup of coffee is to have such a desire and also to be simultaneously and directly aware that one has such a desire. Unconscious thoughts and desires in this sense are simply those we have without being aware of having them, whether our lack of self-knowledge results from simple inattention or more deeply psychoanalytic causes.
Qualitative states. States might also be regarded as conscious in a seemingly quite different and more qualitative sense. That is, one might count a state as conscious just if it has or involves qualitative or experiential properties of the sort often referred to as “qualia” or “raw sensory feels”. (See the entry on qualia.) One's perception of the Merlot one is drinking or of the fabric one is examining counts as a conscious mental state in this sense because it involves various sensory qualia, e.g., taste qualia in the wine case and color qualia in one's visual experience of the cloth. There is considerable disagreement about the nature of such qualia (Churchland 1985, Shoemaker 1990, Clark 1993, Chalmers 1996) and even about their existence. Traditionally qualia have been regarded as intrinsic, private, ineffable monadic features of experience, but current theories of qualia often reject at least some of those commitments (Dennett 1990).
Phenomenal states. Such qualia are sometimes referred to as phenomenal properties and the associated sort of consciousness as phenomenalconsciousness, but the latter term is perhaps more properly applied to the overall structure of experience and involves far more than sensory qualia. The phenomenal structure of consciousness also encompasses much of the spatial, temporal and conceptual organization of our experience of the world and of ourselves as agents in it. (See section 4.3) It is therefore probably best, at least initially, to distinguish the concept of phenomenal consciousness from that of qualitative consciousness, though they no doubt overlap.
What-it-is-like states. Consciousness in both those senses links up as well with Thomas Nagel's (1974) notion of a conscious creature, insofar as one might count a mental state as conscious in the “what it is like” sense just if there is something that it is like to be in that state. Nagel's criterion might be understood as aiming to provide a first-person or internal conception of what makes a state a phenomenal or qualitative state.
Access consciousness. States might be conscious in a seemingly quite different access sense, which has more to do with intra-mental relations. In this respect, a state's being conscious is a matter of its availability to interact with other states and of the access that one has to its content. In this more functional sense, which corresponds to what Ned Block (1995) calls access consciousness, a visual state's being conscious is not so much a matter of whether or not it has a qualitative “what it's likeness”, but of whether or not it and the visual information that it carries is generally available for use and guidance by the organism. In so far as the information in that state is richly and flexibly available to its containing organism, then it counts as a conscious state in the relevant respect, whether or not it has any qualitative or phenomenal feel in the Nagel sense.
Narrative consciousness. States might also be regarded as conscious in a narrative sense that appeals to the notion of the “stream of consciousness”, regarded as an ongoing more or less serial narrative of episodes from the perspective of an actual or merely virtual self. The idea would be to equate the person's conscious mental states with those that appear in the stream (Dennett 1991, 1992).
Although these six notions of what makes a state conscious can be independently specified, they are obviously not without potential links, nor do they exhaust the realm of possible options. Drawing connections, one might argue that states appear in the stream of consciousness only in so far as we are aware of them, and thus forge a bond between the first meta-mental notion of a conscious state and the stream or narrative concept. Or one might connect the access with the qualitative or phenomenal notions of a conscious state by trying to show that states that represent in those ways make their contents widely available in the respect required by the access notion.
Aiming to go beyond the six options, one might distinguish conscious from nonconscious states by appeal to aspects of their intra-mental dynamics and interactions other than mere access relations; e.g., conscious states might manifest a richer stock of content-sensitive interactions or a greater degree of flexible purposive guidance of the sort associated with the self-conscious control of thought. Alternatively, one might try to define conscious states in terms of conscious creatures. That is, one might give some account of what it is to be a conscious creature or perhaps even a conscious self, and then define one's notion of a conscious state in terms of being a state of such a creature or system, which would be the converse of the last option considered above for defining conscious creatures in terms of conscious mental states.
2.3 Consciousness as an entity
The noun “consciousness” has an equally diverse range of meanings that largely parallel those of the adjective “conscious”. Distinctions can be drawn between creature and state consciousness as well as among the varieties of each. One can refer specifically to phenomenal consciousness, access consciousness, reflexive or meta-mental consciousness, and narrative consciousness among other varieties.
Here consciousness itself is not typically treated as a substantive entity but merely the abstract reification of whatever property or aspect is attributed by the relevant use of the adjective “conscious”. Access consciousness is just the property of having the required sort of internal access relations, and qualitative consciousness is simply the property that is attributed when “conscious” is applied in the qualitative sense to mental states. How much this commits one to the ontological status of consciousness per se will depend on how much of a Platonist one is about universals in general. (See the entry on the medieval problem of universals.) It need not commit one to consciousness as a distinct entity any more than one's use of “square”, “red” or “gentle” commits one to the existence of squareness, redness or gentleness as distinct entities.
Though it is not the norm, one could nonetheless take a more robustly realist view of consciousness as a component of reality. That is one could think of consciousness as more on a par with electromagnetic fields than with life.
Since the demise of vitalism, we do not think of life per se as something distinct from living things. There are living things including organisms, states, properties and parts of organisms, communities and evolutionary lineages of organisms, but life is not itself a further thing, an additional component of reality, some vital force that gets added into living things. We apply the adjectives “living” and “alive” correctly to many things, and in doing so we might be said to be attributing life to them but with no meaning or reality other than that involved in their being living things.
Electromagnetic fields by contrast are regarded as real and independent parts of our physical world. Even though one may sometimes be able to specify the values of such a field by appeal to the behavior of particles in it, the fields themselves are regarded as concrete constituents of reality and not merely as abstractions or sets of relations among particles.
Similarly one could regard “consciousness” as referring to a component or aspect of reality that manifests itself in conscious states and creatures but is more than merely the abstract nominalization of the adjective “conscious” we apply to them. Though such strongly realist views are not very common at present, they should be included within the logical space of options.
There are thus many concepts of consciousness, and both “conscious” and “consciousness” are used in a wide range of ways with no privileged or canonical meaning. However, this may be less of an embarrassment than an embarrassment of riches. Consciousness is a complex feature of the world, and understanding it will require a diversity of conceptual tools for dealing with its many differing aspects. Conceptual plurality is thus just what one would hope for. As long as one avoids confusion by being clear about one's meanings, there is great value in having a variety of concepts by which we can access and grasp consciousness in all its rich complexity. However, one should not assume that conceptual plurality implies referential divergence. Our multiple concepts of consciousness may in fact pick out varying aspects of a single unified underlying mental phenomenon. Whether and to what extent they do so remains an open question.
3. Problems of Consciousness
The task of understanding consciousness is an equally diverse project. Not only do many different aspects of mind count as conscious in some sense, each is also open to various respects in which it might be explained or modeled. Understanding consciousness involves a multiplicity not only of explananda but also of questions that they pose and the sorts of answers they require. At the risk of oversimplifying, the relevant questions can be gathered under three crude rubrics as the What, How, and Why questions:
The Descriptive Question: What is consciousness? What are its principal features? And by what means can they be best discovered, described and modeled?
The Explanatory Question: How does consciousness of the relevant sort come to exist? Is it a primitive aspect of reality, and if not how does (or could) consciousness in the relevant respect arise from or be caused by nonconscious entities or processes?
The Functional Question: Why does consciousness of the relevant sort exist? Does it have a function, and if so what is it? Does it act causally and if so with what sorts of effects? Does it make a difference to the operation of systems in which it is present, and if so why and how?
The three questions focus respectively on describing the features of consciousness, explaining its underlying basis or cause, and explicating its role or value. The divisions among the three are of course somewhat artificial, and in practice the answers one gives to each will depend in part on what one says about the others. One can not, for example, adequately answer the what question and describe the main features of consciousness without addressing the why issue of its functional role within systems whose operations it affects. Nor could one explain how the relevant sort of consciousness might arise from nonconscious processes unless one had a clear account of just what features had to be caused or realized to count as producing it. Those caveats notwithstanding, the three-way division of questions provides a useful structure for articulating the overall explanatory project and for assessing the adequacy of particular theories or models of consciousness.
4. The descriptive question: What are the features of consciousness?
The What question asks us to describe and model the principal features of consciousness, but just which features are relevant will vary with the sort of consciousness we aim to capture. The main properties of access consciousness may be quite unlike those of qualitative or phenomenal consciousness, and those of reflexive consciousness or narrative consciousness may differ from both. However, by building up detailed theories of each type, we may hope to find important links between them and perhaps even to discover that they coincide in at least some key respects.
4.1 First-person and third-person data
The general descriptive project will require a variety of investigational methods (Flanagan 1992). Though one might naively regard the facts of consciousness as too self-evident to require any systematic methods of gathering data, the epistemic task is in reality far from trivial (Husserl 1913).
First-person introspective access provides a rich and essential source of insight into our conscious mental life, but it is neither sufficient in itself nor even especially helpful unless used in a trained and disciplined way. Gathering the needed evidence about the structure of experience requires us both to become phenomenologically sophisticated self-observers and to complement our introspective results with many types of third-person data available to external observers (Searle 1992, Varela 1995, Siewert 1998)
As phenomenologists have known for more than a century, discovering the structure of conscious experience demands a rigorous inner-directed stance that is quite unlike our everyday form of self-awareness (Husserl 1929, Merleau-Ponty 1945). Skilled observation of the needed sort requires training, effort and the ability to adopt alternative perspectives on one's experience.
The need for third-person empirical data gathered by external observers is perhaps most obvious with regard to the more clearly functional types of consciousness such as access consciousness, but it is required even with regard to phenomenal and qualitative consciousness. For example, deficit studies that correlate various neural and functional sites of damage with abnormalities of conscious experience can make us aware of aspects of phenomenal structure that escape our normal introspective awareness. As such case studies show, things can come apart in experience that seem inseparably unified or singular from our normal first-person point of view (Sacks 1985, Shallice 1988, Farah 1995).
Or to pick another example, third-person data can make us aware of how our experiences of acting and our experiences of event-timing affect each other in ways that we could never discern through mere introspection (Libet 1985, Wegner 2002). Nor are the facts gathered by these third person methods merely about the causes or bases of consciousness; they often concern the very structure of phenomenal consciousness itself. First-person, third-person and perhaps even second-person (Varela 1995) interactive methods will all be needed to collect the requisite evidence.
Using all these sources of data, we will hopefully be able to construct detailed descriptive models of the various sorts of consciousness. Though the specific features of most importance may vary among the different types, our overall descriptive project will need to address at least the following seven general aspects of consciousness (sections 4.2–4.7).
4.2 Qualitative character
Qualitative character is often equated with so called “raw feels” and illustrated by the redness one experiences when one looks at ripe tomatoes or the specific sweet savor one encounters when one tastes an equally ripe pineapple (Locke 1688). The relevant sort of qualitative character is not restricted to sensory states, but is typically taken to be present as an aspect of experiential states in general, such as experienced thoughts or desires (Siewert 1998).
The existence of such feels may seem to some to mark the threshold for states or creatures that are really conscious. If an organism senses and responds in apt ways to its world but lacks such qualia, then it might count as conscious at best in a loose and less than literal sense. Or so at least it would seem to those who take qualitative consciousness in the “what it is like” sense to be philosophically and scientifically central (Nagel 1974, Chalmers 1996).
Qualia problems in many forms—Can there be inverted qualia? (Block 1980a 1980b, Shoemaker 1981, 1982) Are qualia epiphenomenal? (Jackson 1982, Chalmers 1996) How could neural states give rise to qualia? (Levine 1983, McGinn 1991)—have loomed large in the recent past. But the What question raises a more basic problem of qualia: namely that of giving a clear and articulated description of our qualia space and the status of specific qualia within it.
Absent such a model, factual or descriptive errors are all too likely. For example, claims about the unintelligibility of the link between experienced red and any possible neural substrate of such an experience sometimes treat the relevant color quale as a simple and sui generisproperty (Levine 1983), but phenomenal redness in fact exists within a complex color space with multiple systematic dimensions and similarity relations (Hardin 1992). Understanding the specific color quale relative to that larger relational structure not only gives us a better descriptive grasp of its qualitative nature, it may also provide some “hooks” to which one might attach intelligible psycho-physical links.
Color may be the exception in terms of our having a specific and well developed formal understanding of the relevant qualitative space, but it is not likely an exception with regard to the importance of such spaces to our understanding of qualitative properties in general (Clark 1993, P.M. Churchland 1995). (See the entry on qualia.)
4.3 Phenomenal structure
Phenomenal structure should not be conflated with qualitative structure, despite the sometimes interchangeable use of “qualia” and “phenomenal properties” in the literature. “Phenomenal organization” covers all the various kinds of order and structure found within the domain of experience, i.e., within the domain of the world as it appears to us. There are obviously important links between the phenomenal and the qualitative. Indeed qualia might be best understood as properties of phenomenal or experienced objects, but there is in fact far more to the phenomenal than raw feels. As Kant (1787), Husserl (1913), and generations of phenomenologists have shown, the phenomenal structure of experience is richly intentional and involves not only sensory ideas and qualities but complex representations of time, space, cause, body, self, world and the organized structure of lived reality in all its conceptual and nonconceptual forms.
Since many non-conscious states also have intentional and representational aspects, it may be best to consider phenomenal structure as involving a special kind of intentional and representational organization and content, the kind distinctively associated with consciousness (Siewert 1998). (See the entry on representational theories of consciousness).
Answering the What question requires a careful account of the coherent and densely organized representational framework within which particular experiences are embedded. Since most of that structure is only implicit in the organization of experience, it can not just be read off by introspection. Articulating the structure of the phenomenal domain in a clear and intelligible way is a long and difficult process of inference and model building (Husserl 1929). Introspection can aid it, but a lot of theory construction and ingenuity are also needed.
There has been recent philosophical debate about the range of properties that are phenomenally present or manifest in conscious experience, in particular with respect to cognitive states such as believing or thinking. Some have argued for a so called “thin” view according to which phenomenal properties are limited to qualia representing basic sensory properties, such as colors, shapes, tones and feels. According to such theorists, there is no distinctive “what-it-is-likeness” involved in believing that Paris is the capital of France or that 17 is a prime number (Tye, Prinz 2012). Some imagery, e.g., of the Eiffel Tower, may accompany our having such a thought, but that is incidental to it and the cognitive state itself has no phenomenal feel. On the thin view, the phenomenal aspect of perceptual states as well is limited to basic sensory features; when one sees an image of Winston Churchill, one's perceptual phenomenology is limited only to the spatial aspects of his face.
Others holds a “thick” view according to which the phenomenology of perception includes a much wider range of features and cognitive states have a distinctive phenomenology as well (Strawson 2003, Pitt 2004, Seigel 2010). On the thick view, the what-it-is-likeness of perceiving an image of Marilyn Monroe includes one's recognition of her history as part of the felt aspect of the experience, and beliefs and thoughts as well can and typically do have a distinctive nonsensory phenomenology. Both sides of the debate are well represented in the volume Cognitive Phenomenology (Bayne and Montague 2010).
4.4 Subjectivity
Subjectivity is another notion sometimes equated with the qualitative or the phenomenal aspects of consciousness in the literature, but again there are good reason to recognize it, at least in some of its forms, as a distinct feature of consciousness—related to the qualitative and the phenomenal but different from each. In particular, the epistemic form of subjectivity concerns apparent limits on the knowability or even the understandability of various facts about conscious experience (Nagel 1974, Van Gulick 1985, Lycan 1996).
On Thomas Nagel's (1974) account, facts about what it is like to be a bat are subjective in the relevant sense because they can be fully understood only from the bat-type point of view. Only creatures capable of having or undergoing similar such experiences can understand their what-it's-likeness in the requisite empathetic sense. Facts about conscious experience can be at best incompletely understood from an outside third person point of view, such as those associated with objective physical science. A similar view about the limits of third-person theory seems to lie behind claims regarding what Frank Jackson's (1982) hypothetical Mary, the super color scientist, could not understand about experiencing red because of her own impoverished history of achromatic visual experience.
Whether facts about experience are indeed epistemically limited in this way is open to debate (Lycan 1996), but the claim that understanding consciousness requires special forms of knowing and access from the inside point of view is intuitively plausible and has a long history (Locke 1688). Thus any adequate answer to the What question must address the epistemic status of consciousness, both our abilities to understand it and their limits (Papineau 2002, Chalmers 2003). (See the entry onself-knowledge).
4.5 Self-perspectival organization
The perspectival structure of consciousness is one aspect of its overall phenomenal organization, but it is important enough to merit discussion in its own right. Insofar as the key perspective is that of the conscious self, the specific feature might be called self-perspectuality. Conscious experiences do not exist as isolated mental atoms, but as modes or states of a conscious self or subject (Descartes 1644, Searle 1992, though pace Hume 1739). A visual experience of a blue sphere is always a matter of there being some self or subject who is appeared to in that way. A sharp and stabbing pain is always a pain felt or experienced by some conscious subject. The self need not appear as an explicit element in our experiences, but as Kant (1787) noted the “I think” must at least potentially accompany each of them.
The self might be taken as the perspectival point from which the world of objects is present to experience (Wittgenstein 1921). It provides not only a spatial and temporal perspective for our experience of the world but one of meaning and intelligibility as well. The intentional coherence of the experiential domain relies upon the dual interdependence between self and world: the self as perspective from which objects are known and the world as the integrated structure of objects and events whose possibilities of being experienced implicitly define the nature and location of the self (Kant 1787, Husserl 1929).
Conscious organisms obviously differ in the extent to which they constitute a unified and coherent self, and they likely differ accordingly in the sort or degree of perspectival focus they embody in their respective forms of experience (Lorenz 1977). Consciousness may not require a distinct or substantial self of the traditional Cartesian sort, but at least some degree of perspectivally self-like organization seems essential for the existence of anything that might count as conscious experience. Experiences seem no more able to exist without a self or subject to undergo them than could ocean waves exist without the sea through which they move. The Descriptive question thus requires some account of the self-perspectival aspect of experience and the self-like organization of conscious minds on which it depends, even if the relevant account treats the self in a relatively deflationary and virtual way (Dennett 1991, 1992).
4.6 Unity
Unity is closely linked with the self-perspective, but it merits specific mention on its own as a key aspect of the organization of consciousness. Conscious systems and conscious mental states both involve many diverse forms of unity. Some are causal unities associated with the integration of action and control into a unified focus of agency. Others are more representational and intentional forms of unity involving the integration of diverse items of content at many scales and levels of binding (Cleeremans 2003).
Some such integrations are relatively local as when diverse features detected within a single sense modality are combined into a representation of external objects bearing those features, e.g. when one has a conscious visual experience of a moving red soup can passing above a green striped napkin (Triesman and Gelade 1980).
Other forms of intentional unity encompass a far wider range of contents. The content of one's present experience of the room in which one sits depends in part upon its location within a far larger structure associated with one's awareness of one's existence as an ongoing temporally extended observer within a world of spatially connected independently existing objects (Kant 1787, Husserl 1913). The individual experience can have the content that it does only because it resides within that larger unified structure of representation. (See the entry onunity of consciousness.)
Particular attention has been paid recently to the notion of phenomenal unity (Bayne 2010) and its relation to other forms of conscious unity such as those involving representational, functional or neural integration. Some have argued that phenomenal unity can be reduced to representational unity (Tye 2005) while others have denied the possibility of any such reduction (Bayne 2010).
4.7 Intentionality and transparency
Conscious mental states are typically regarded as having a representational or intentional aspect in so far as they are about things, refer to things or have satisfaction conditions. One's conscious visual experience correctly represents the world if there are lilacs in a white vase on the table (pace Travis 2004), one's conscious memory is ofthe attack on the World Trade Center, and one's conscious desire is for a glass of cold water. However, nonconscious states can also exhibit intentionality in such ways, and it is important to understand the ways in which the representational aspects of conscious states resemble and differ from those of nonconscious states (Carruthers 2000). Searle (1990) offers a contrary view according to which only conscious states and dispositions to have conscious states can be genuinely intentional, but most theorists regard intentionality as extending widely into the unconscious domain. (See the entry on consciousness and intentionality.)
One potentially important dimension of difference concerns so calledtransparency, which is an important feature of consciousness in two interrelated metaphoric senses, each of which has an intentional, an experiential and a functional aspect.
Conscious perceptual experience is often said to be transparent, or in G.E. Moore's (1922) phrase “diaphanous”. We transparently “look through” our sensory experience in so far as we seem directly aware of external objects and events present to us rather than being aware of any properties of experience by which it presents or represents such objects to us. When I look out at the wind-blown meadow, it is the undulating green grass of which I am aware not of any green property of my visual experience. (See the entry on representational theories of consciousness.) Moore himself believed we could become aware of those latter qualities with effort and redirection of attention, though some contemporary transparency advocates deny it (Harman 1990, Tye 1995, Kind 2003).
Conscious thoughts and experiences are also transparent in a semantic sense in that their meanings seem immediately known to us in the very act of thinking them (Van Gulick 1992). In that sense we might be said to ‘think right through’ them to what they mean or represent. Transparency in this semantic sense may correspond at least partly with what John Searle calls the “intrinsic intentionality” of consciousness (Searle 1992).
Our conscious mental states seem to have their meanings intrinsically or from the inside just by being what they are in themselves, by contrast with many externalist theories of mental content that ground meaning in causal, counterfactual or informational relations between bearers of intentionality and their semantic or referential objects.
The view of conscious content as intrinsically determined and internally self-evident is sometimes supported by appeals to brain in the vat intuitions, which make it seem that the envatted brain's conscious mental states would keep all their normal intentional contents despite the loss of all their normal causal and informational links to the world (Horgan and Tienson 2002). There is continued controversy about such cases and about competing internalist (Searle 1992) and externalist views (Dretske 1995) of conscious intentionality.
Though semantic transparency and intrinsic intentionality have some affinities, they should not be simply equated, since it may be possible to accommodate the former notion within a more externalist account of content and meaning. Both semantic and sensory transparency obviously concern the representational or intentional aspects of consciousness, but they are also experiential aspects of our conscious life. They are part of what it's like or how it feels phenomenally to be conscious. They also both have functional aspects, in so far as conscious experiences interact with each other in richly content-appropriate ways that manifest our transparent understanding of their contents.
4.8 Dynamic flow
The dynamics of consciousness are evident in the coherent order of its ever changing process of flow and self-transformation, what William James (1890) called the “stream of consciousness.” Some temporal sequences of experience are generated by purely internal factors as when one thinks through a puzzle, and others depend in part upon external causes as when one chases a fly ball, but even the latter sequences are shaped in large part by how consciousness transforms itself.
Whether partly in response to outer influences or entirely from within, each moment to moment sequence of experience grows coherently out of those that preceded it, constrained and enabled by the global structure of links and limits embodied in its underlying prior organization (Husserl 1913). In that respect, consciousness is an autopoietic system, i.e., a self-creating and self-organizing system (Varela and Maturana 1980).
As a conscious mental agent I can do many things such as scan my room, scan a mental image of it, review in memory the courses of a recent restaurant meal along with many of its tastes and scents, reason my way through a complex problem, or plan a grocery shopping trip and execute that plan when I arrive at the market. These are all routine and common activities, but each involves the directed generation of experiences in ways that manifest an implicit practical understanding of their intentional properties and interconnected contents (Van Gulick 2000).
Consciousness is a dynamic process, and thus an adequate descriptive answer to the What question must deal with more than just its static or momentary properties. In particular, it must give some account of the temporal dynamics of consciousness and the ways in which its self-transforming flow reflects both its intentional coherence and the semantic self-understanding embodied in the organized controls through which conscious minds continually remake themselves as autopoietic systems engaged with their worlds.
A comprehensive descriptive account of consciousness would need to deal with more than just these seven features, but having a clear account of each of them would take us a long way toward answering the “What is consciousness?” question.
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