Philosophy, Neuroscience and Consciousness

Rex Welshon

• Verlag: Routledge
• Jahr: 2016
• ISBN:
  9781315478753
• Auflage: 1
• Thema: Philosophie
• Thema: Histoire et théorie de la philosophie

Explaining consciousness is one of the last great unanswered scientific and philosophical problems. Immediately known, familiar and obvious, consciousness is also baffling, opaque and strange. This introduction to the problems posed by consciousness discusses the most important work of cognitive science, neurophysiology and philosophy of mind of the past thirty years and presents an up to date assessment of the issues and debates. The reader is first introduced to the way that consciousness has been thought about in the history of philosophy and psychology. The author then presents an informal and largely non-technical account of the properties of consciousness that are thought to be the most paradigmatic and problematic. Recent scientific work on consciousness, from neurophysiological studies of the brain and evolutionary studies of the development of consciousness to computational theories of the mind are then examined and the philosophical problems that these accounts raise are systematically introduced. The final chapters of the book consider more practical matters by addressing self-deception, neuroses, the unconscious and notions of the self, before concluding with an assessment of the future for psychology and the philosophy of mind.

1. CONSCIOUSNESS AND CONSCIOUS PROPERTIES

Our topics are consciousness, its properties, what neuroscience has to say about them, and whether what neuroscience has to say about them is enough to warrant reducing conscious properties and events to neural assemblies, their activities and their properties. A psychological state, process, or event is conscious in the full sense of the term whenever it is intentionally structured, qualitatively endowed and subjectively perspectival or, more pedantically, whenever it has the properties of being intentionally structured, qualitatively endowed and subjectively perspectival. As so understood, a conscious event is complex, for it is a set of properties instantiated by a psychological event, state or process. Since it is a set of properties that are instantiated when a psychological event, state or process is conscious, any such event, state or process that has deficits to one or more of these properties is compromised. Neuroscience confirms the existence of compromised conscious events, states and processes.

In this first chapter, we begin the process of untangling the knots posed by consciousness and its properties by trying to appreciate why intentionality, qualitative character and subjective perspectivity are so confounding, to understand what these properties are, and to clarify some of the ways the terms “conscious” “unconscious” and “subconscious” are used in contemporary neuroscience and philosophy. In subsequent chapters, we discuss in a philosophical environment the nature of various candidate relations between conscious events and their properties, and neural processes and their properties. We then turn to evidence that there are neural correlates of conscious properties. In the final four chapters, that evidence is assessed from a philosophical perspective.

SPECIES OF CONSCIOUSNESS

Investigating scientific and philosophical work on consciousness immediately reveals that “consciousness” picks out not a single phenomenon but rather a whole family of phenomena. Philosophers, cognitive scientists and neuroscientists variously talk about each of the following: awakened arousal; tonic alertness; phenomenal consciousness; access consciousness; peripheral consciousness; higher-order consciousness; reflective consciousness; primary consciousness; monitoring consciousness; self-awareness; self-consciousness; state consciousness; creature consciousness; altered states of consciousness; unconsciousness; non-consciousness; subconsciousness. It is all a little bewildering. Moreover, this list does not even include the conscious processes of greatest interest to neuroscientists, states such as perception, interoception, proprioception, emotion, attention, working memory, cognition and metacognition. We take this opportunity to disentangle some of the kinds of consciousness frequently used and to describe in a little greater detail the kinds to which we will return again and again. We introduce perception, interoception, proprioception, emotion, attention, working memory, cognition and metacognition presently.

Arousal and tonic alertness refer to a state of an organism.¹ An organism is aroused when neurochemical activity in its central nervous system is activated to a sufficiently high level that the organism is responsive to stimuli. An organism that is not aroused is asleep or either in a stupor, a deeply unresponsive state interrupted only by applying repeated and forceful stimuli, or in a coma, a deeply unresponsive state that continues uninterrupted despite repeated and forceful stimuli. Coma and stupor are distinct from vegetative state, a superficially similar disorder characterized by preservation of the sleep-waking cycle and the absence of higher-order mental activity. Dream sleep is an interesting state, of course, because while we dream, arousal is dissociated from qualitatively endowed, intentional and perspectival experience: we are not responsive to stimuli but experience dream content. Tonic alertness is a level of neurochemical activation that obtains only if arousal has obtained, contains no specific content, and underwrites the sustenance of a coherent line of experience, thought or action (Filley 2001, 2002). Tonic alertness is intermediate between arousal and phasic attention, the latter of which is an isolable state of augmented alertness in which there is affective and cognitive orientation to, selection of, and concentration upon, some content in the field of experience.

Phenomenal consciousness and access consciousness are widely used terms associated with the work of Ned Block (2005, [1995] 2007), a contemporary philosopher. Informally, phenomenal consciousness is qualitatively endowed consciousness. Qualitatively endowed consciousness refers to the set of conscious events that have qualitative character, where qualitative character refers to any of the myriad ways conscious events are like for the subject. A psychological event, state or process is phenomenally conscious if there is something it is like to have that event. Phenomenal consciousness has been discussed by philosophers for centuries. In psychology, the situation is different. Having made a brief appearance in psychology with James, Wundt and Titchener, phenomenal consciousness quickly slipped into scientific disrepute and has only recently been rehabilitated in neuroscience with the emergence of sophisticated imaging techniques that can identify its neural correlates. Access consciousness is the set of conscious psychological events, states and processes that are poised for subsequent cognitive (thinking) and affective (emotional) activity. A psychological event, state or process is access conscious if it can be used for subsequent psychological activity. Block has recently (2007a) dropped both terms, replacing them with the less loaded “phenomenology” and “accessibility”. We concur with this decision – in this book, neither “phenomenal consciousness” nor “access consciousness” is used. We instead assume that phenomenology and accessibility are conscious properties. We further assume that phenomenology and accessibility are properties of certain psychological states, events and processes (Burge [2006] 2007). These properties are introduced in greater detail in the next section.

Of the four kinds of states, processes and events described so far, arousal is arguably not properly a kind of consciousness at all, for while it may be required for consciousness, an organism can be, as is the case of someone in persistent vegetative state, aroused but unconscious. Tonic alertness, on the other hand, is arguably close to a baseline conscious state, if not actually a baseline conscious state. Phenomenology and accessibility are conscious properties. The relations between tonic alertness and phenomenology and accessibility are discussed in later chapters.

However one establishes a minimal conscious state, other species of conscious states that do not occur without more basic species also bear introduction. Phenomenally conscious states and the most basic of access conscious states are species of object-level or primary conscious states; that is, they are kinds of conscious states that occur without the occurrence of any more basic kinds of conscious states and whose occurrence is necessary for other less basic kinds of conscious states. Conscious states that cannot occur without primary conscious states and that are about primary conscious states are species of secondary or reflexive conscious states (Rees et al. 2002; Searle 2000). There are a number of related phenomena in this class, including reflection, monitoring, error detection, error correction, self-reflection and self-consciousness.

Perceptual, interoceptive, proprioceptive, affective and some cognitive events, states and processes that are phenomenally conscious are primary because they occur upon the foundation of subconscious sensory processing but prior to any reflexive conscious events, states or processes (Burge [2006] 2007). I may, for example, experience a rich and subtle palette of colours as the setting sun reflects off a mile-long escarpment of sandstone. That event is an example of a primary conscious event that has both phenomenal and access properties. I may of course direct attention to that event’s phenomenological character. I may attend to the last colour seen as the sun sinks below the horizon. That subsequent event is reflexively conscious. In general, accessible events, states and processes are primary when they occur subsequent to subconscious processing but prior to conscious events, states or processes that are about them. Again, some access conscious events, states and processes – the reflexive ones – are about primary conscious events, states or processes. Included in the class of reflexive access conscious events are top-down attention, introspection, self-awareness and executive functions such as cognitive control, monitoring, error correction, metacognition, planning and decision-making. Each of these differs from the next either as to the nature of what it is about or represents or as to the nature of the cognitive or affective interest it brings to bear on what it is about. Thinking about our decision-making process in buying a car is, for instance, distinct from reflecting on our procliv...