The Cambridge Handbook of Consciousness
The Cambridge Handbook of Consciousnessis the first of its kind in the field, and its appearance marks a unique time in the history of intellectual inquiry on the topic. After decades during which consciousness was considered beyond the scope of legitimate scientific investigation, conscious- ness re-emerged as a popular focus of research toward the end of the last century, and it has remained so for nearly2 0years. There are now so many different lines of investigation on con- sciousness that the time has come when the field may finally benefit from a book that pulls them together and, by juxtaposing them, provides a comprehensive survey of this exciting field.
Philip David Zelazo is Professor of Psychology at the University of Toronto, where he holds a Canada Research Chair in Developmental Neuroscience. He is also Co-Director of the Sino-Canadian Centre for Research in Child Development, Southwest University, China. He was Founding Editor of the Journal of Cogni- tion and Development. His research, which is funded by the Natural Sciences and Engineer- ing Research Council (NSERC) of Canada, the Canadian Institutes of Health Research (CIHR), and the Canadian Foundation for Innovation
(CFI), focuses on the mechanisms underly- ing typical and atypical development of exec- utive function – the conscious self-regulation of thought, action, and emotion. In September 2 0 0 7, he will assume the Nancy M. and John L. Lindhal Professorship at the Institute of Child Development, University of Minnesota.
Morris Moscovitch is the Max and Gianna Glass- man Chair in Neuropsychology and Aging in the Department of Psychology at the University of Toronto. He is also a Senior Scientist at the Rotman Research Institute of Baycrest Centre for Geriatric Care. His research focuses on the neuropsychology of memory in humans but also addresses attention, face recognition, and hemi- spheric specialization in young and older adults, and in people with brain damage.
Evan Thompson is Professor of Philosophy at the University of Toronto. He is the author ofMind in Life: Biology, Phenomenoloy, and the Sciences of MindandColour Vision: A Study in Cognitive Sci- ence and the Philosophy of Perception. He is also the co-author of The Embodied Mind: Cognitive Science and Human Experience. He is a former holder of a Canada Research Chair.
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The Cambridge Handbook of Consciousness
Edited by
Philip David Zelazo, Morris Moscovitch and Evan Thompson
University of Toronto
iii
Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
First published in print format
ISBN-13 978-0-521-85743-7
ISBN-13 978-0-521-67412-6 ISBN-13 978-0-511-28923-1
© Cambridge University Press 2007
2007
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This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press.
ISBN-10 0-511-28923-5
ISBN-10 0-521-85743-0
ISBN-10 0-521-67412-3
Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.
Published in the United States of America by Cambridge University Press, New York www.cambridge.org
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hardback
To the memory of Francisco J. Varela ( 7 September 19 4 6 – 2 8 May 2 0 0 1 ) – ET To my growing family: Jill, Elana, David, Leora, and Ezra Meir
– MM For Sam, and the next iteration
– PDZ
And a special dedication to Joseph E. Bogen ( 13 July 19 2 6 – 2 2 April 2 0 0 5 )
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Contents
List of Contributors pagexi
1. Introduction 1
p a r t i
THE COGNITIVE SCIENCE OF CONSCIOUSNESS
a . philosophy
2. A Brief History of the Philosophical Problem of Consciousness 9 William Seager
3. Philosophical Theories of Consciousness: Contemporary
Western Perspectives 3 5
Uriah Kriegel
4. Philosophical Issues:
Phenomenology 6 7
Evan Thompson and Dan Zahavi 5. Asian Perspectives: Indian Theories
of Mind 8 9
Georges Dreyfus and Evan Thompson
b . computational approaches to consciousness
6. Artificial Intelligence and
Consciousness 117
Drew McDermott
7. Computational Models of Consciousness: A Taxonomy
and Some Examples 15 1
Ron Sun and Stan Franklin
c . cognitive psychology
8. Cognitive Theories of
Consciousness 17 7
Katharine McGovern and Bernard J. Baars
9. Behavioral, Neuroimaging, and Neuropsychological Approaches to Implicit Perception 2 0 7 Daniel J. Simons, Deborah E.
Hannula, David E. Warren, and Steven W. Day
vii
viii contents 1 0. Three Forms of Consciousness in
Retrieving Memories 2 5 1 Henry L. Roediger III, Suparna
Rajaram, and Lisa Geraci
1 1. Metacognition and Consciousness 2 8 9 Asher Koriat
1 2. Consciousness and Control
of Action 3 2 7
Carlo Umilt `a
d . linguistic considerations
1 3. Language and Consciousness 3 5 5 Wallace Chafe
1 4. Narrative Modes of Consciousness
and Selfhood 3 7 5
Keith Oatley
e . developmental psychology
1 5. The Development
of Consciousness 4 0 5
Philip David Zelazo, Helena Hong Gao, and Rebecca Todd
f . alternative states of consciousness
1 6. States of Consciousness: Normal and Abnormal Variation 4 3 5 J. Allan Hobson
1 7. Consciousness in Hypnosis 4 4 5 John F. Kihlstrom
1 8. Can We Study Subjective Experiences Objectively?
First-Person Perspective Approaches and Impaired Subjective States of Awareness
in Schizophrenia 4 8 1
Jean-Marie Danion and Caroline Huron
1 9. Meditation and the Neuroscience of Consciousness: An Introduction 4 9 9 Antoine Lutz, John D. Dunne, and
Richard J. Davidson
g . anthropology/social
psychology of consciousness
2 0. Social Psychological Approaches
to Consciousness 5 5 5
John A. Bargh
2 1. The Evolution of Consciousness 5 7 1 Michael C. Corballis
2 2. The Serpent’s Gift: Evolutionary Psychology and Consciousness 5 9 7 Jesse M. Bering and David F.
Bjorklund
2 3. Anthropology of Consciousness 6 3 1 C. Jason Throop and Charles
D. Laughlin
h . psychodynamic approaches to consciousness
2 4. Motivation, Decision Making, and Consciousness: From
Psychodynamics to Subliminal Priming and Emotional Constraint
Satisfaction 6 7 3
Drew Westen, Joel Weinberger, and Rebekah Bradley
p a r t ii
THE NEUROSCIENCE OF CONSCIOUSNESS
a . neurophysiological mechanisms of consciousness
2 5. Hunting the Ghost: Toward a
Neuroscience of Consciousness 7 0 7 Petra Stoerig
2 6. Neurodynamical Approaches to
Consciousness 7 3 1
Diego Cosmelli, Jean-Philippe Lachaux, and Evan Thompson
b . neuropsychological aspects of consciousness: disorders and neuroimaging
2 7. The Thalamic Intralaminar Nuclei and the Property of Consciousness 7 7 5 Joseph E. Bogen
contents ix 2 8. The Cognitive Neuroscience of
Memory and Consciousness 8 0 9 Scott D. Slotnick and Daniel
L. Schachter
c . affective neuroscience of consciousness
2 9. The Affective Neuroscience of Consciousness: Higher- Order Syntactic Thoughts, Dual Routes to Emotion and Action, and
Consciousness 8 3 1
Edmund T. Rolls
d . social neuroscience of consciousness
3 0. Consciousness: Situated and Social 8 6 3 Ralph Adolphs
p a r t iii
QUANTUM APPROACHES TO CONSCIOUSNESS
3 1. Quantum Approaches to
Consciousness 8 8 1
Henry Stapp
Author Index 9 0 9
Subject Index 9 3 9
x
List of Contributors
Ralph Adolphs, PhD Department of Psychology California Institute of Technology HSS2 2 8-7 7
Pasadena, CA9 112 5USA E-mail: [email protected] Bernard J. Baars, PhD
The Neurosciences Institute 10 6 4 0John Jay Hopkins Drive San Diego, CA9 2 12 1USA E-mail: [email protected] John A. Bargh, PhD Department of Psychology Yale University
2 Hillhouse Avenue P.O. Box2 0 8 2 0 5
New Haven, CT0 6 5 2 0-8 2 0 5USA E-mail: [email protected] Jesse M. Bering, PhD
Institute of Cognition and Culture Queen’s University, Belfast 4Fitzwilliam Street
Belfast, Northern Ireland BT7 1NN E-mail: [email protected] David F. Bjorklund, PhD Department of Psychology Florida Atlantic University Boca Raton, FL3 3 4 3 1-0 0 9 1USA E-mail: [email protected]
Joseph E. Bogen, MD (Deceased)
Formerly of University of Southern California and the University of California, Los Angeles Rebekah Bradley
Department of Psychiatry and Behavioral Sciences
Emory University 14 6 2 Clifton Road Atlanta, GA3 0 3 2 2USA E-mail: [email protected] Wallace Chafe, PhD Department of Linguistics
University of California, Santa Barbara Santa Barbara, CA9 3 10 6USA E-mail: [email protected] Michael C. Corballis, PhD Department of Psychology University of Auckland Private Bag9 2 0 19
Auckland10 2 0NEW ZEALAND E-mail: [email protected] Diego Cosmelli, PhD
Centro de Estudios Neurobiol ´ogicos Departomento de Psiquiatr ´oa P. Universidad Cat ´olica de Chile Marcoleto3 8 7,2◦piso
Santiago, Chile
xi
xii list of contributors (Also: Laboratoire de neurosciences Cognitives
et Imagerie C´er´ebrale (LENA)
4 7Bd de l’H ˆopital,7 5 6 5 1Paris FRANCE) E-mail: [email protected] Jean-Marie Danion, MD
INSERM Unit´e4 0 5
H ˆopital Civil de Strasbourg – Clinique Psychiatrique
1place de l’H ˆopital – BP n◦4 2 6
6 7 0 9 1STRASBOURG Cedex FRANCE E-mail: jean-marie.danion@chru strasbourg.fr Richard J. Davidson, PhD
W. M. Keck Laboratory for Functional Brain Imaging and Behavior
Waisman Center
University of Wisconsin-Madison 15 0 0Highland Avenue
Madison, WI5 3 7 0 3-2 2 8 0USA E-mail: [email protected] Steven W. Day, BSc Department of Psychology University of Illinois 6 0 3East Daniel Street Champaign, IL6 18 2 0USA Georges Dreyfus, PhD Department of Religion Williams College E14Stetson Hall
Williamstown, MA0 12 6 7USA
E-mail: [email protected] John D. Dunne, PhD
Department of Religion Emory University Mailstop:15 3 5/0 0 2/1AA 5 3 7Kilgo Circle Atlanta, GA3 0 3 2 2USA E-mail: [email protected] Stan Franklin, PhD
Institute for Intelligent Systems The University of Memphis Memphis, TN3 8 15 2USA E-mail: [email protected] Helena Hong Gao, PhD
School of Humanities and Social Sciences Nanyang Technological University Singapore6 3 9 7 9 8
E-mail: [email protected] Lisa Geraci, PhD
Department of Psychology Washington University One Brookings Drive
Campus Box112 5
St. Louis, MO6 3 13 0-4 8 9 9USA E-mail: [email protected] Deborah E. Hannula
Psychology Department University of Illinois
6 0 3E. Daniel Street, Room8 0 7 Champaign, IL6 18 2 0USA E-mail: [email protected] J. Allan Hobson, MD
Massachusetts Mental Health Center Psychiatry, S12
7 4Fenwood Road Boston, MA0 2 115USA
E-mail: allan [email protected] Caroline Huron, MD, PhD
INSERM0 117
Service Hopitalo-Universitaire de Sant´e Mentale et Th´erapeuthique
H ˆopital Sainte-Anne Universit´e Paris V Pavillon Broca 2ter rue d’Al´esia 7 5 0 14Paris FRANCE
E-mail: [email protected] John F. Kihlstrom, PhD
Department of Psychology, MC16 5 0 University of California, Berkeley Tolman Hall3 2 10
Berkeley, CA9 4 7 2 0-16 5 0USA E-mail: [email protected] Asher Koriat, PhD
Department of Psychology University of Haifa Haifa3 19 0 5 ISRAEL
E-mail: [email protected] Uriah Kriegel, PhD
Department of Philosophy Social Science Bldg. Rm2 13 P.O. Box2 10 0 2 7
Tucson, AZ8 5 7 2 1-0 0 2 7USA E-mail: [email protected] Jean-Philippe Lachaux
INSERM – Unit´e2 8 0
Centre Hospitalier Le Vinatier Bˆatiment4 5 2
9 5Boulevard Pinel 6 9 5 0 0BRON, FRANCE E-mail: [email protected]
list of contributors xiii Charles D. Laughlin, PhD
Department of Sociology and Anthropology Carleton University
12 5Colonel By Drive
Ottawa, ON K1S5B6CANADA Antoine Lutz, PhD
W. M. Keck Laboratory for Functional Brain Imaging and Behavior
Waisman Center
University of Wisconsin-Madison 15 0 0Highland Avenue
Madison, WI5 3 7 0 3-2 2 8 0USA E-mail: [email protected] Drew McDermott, PhD
Department of Computer Science Yale University
P.O. Box2 0 8 2 8 5
New Haven, CT0 6 5 2 0-8 2 8 5USA E-mail: [email protected] Katharine McGovern, PhD
California Institute of Integral Studies 14 5 3Mission Street
San Francisco, CA9 4 10 3 USA E-mail: [email protected] Keith Oately, PhD
Department of Human Development and Applied Psychology
Ontario Institute for Studies in Education/University of Toronto 2 5 2Bloor Street West
Toronto, ON M5S1V6CANADA E-mail: [email protected] Suparna Rajaram, PhD
Department of Psychology SUNY at Stony Brook
Stony Brook, NY117 9 4-2 5 0 0USA E-mail: [email protected] Henry L. Roediger III, PhD
Department of Psychology, Box112 5 Washington University
One Brookings Drive
St. Louis, MO6 3 13 0-4 8 9 9USA E-mail: [email protected] Edmund T. Rolls, PhD
University of Oxford
Department of Experimental Psychology South Parks Road
Oxford OX1 3UD ENGLAND E-mail: [email protected]
Daniel L. Schachter, PhD Department of Psychology Harvard University
Cambridge, MA0 2 13 8USA E-mail: [email protected] William Seager, PhD Department of Philosophy
University of Toronto at Scarborough 2 6 5 Military Trail
Scarborough, ON M1C1A4 CANADA E-mail: [email protected] Daniel J. Simons, PhD
Psychology Department University of Illinois
6 0 3 E. Daniel Street, Room8 0 7 Champaign, IL6 18 2 0USA E-mail: [email protected] Scott D. Slotnick Department of Psychology Boston College
McGuinn Hall
Chestnut Hill, MA0 2 4 6 7USA E-mail: [email protected] Henry Stapp, PhD
Lawrence Berkeley National Lab Physics Division
1Cyclotron Road Mail Stop5 0A-5 10 1 Berkeley, CA9 4 7 2 0-8 15 3USA E-mail: [email protected] Petra Stoerig, PhD
Institute of Physiological Psychology Heinrich-Heine-University
D ¨usseldorf D-4 0 2 2 5GERMANY E-mail: [email protected] Ron Sun, PhD
Cognitive Science Department Rensselaer Polytechnic Institute 110Eighth Street, Carnegie3 0 2A Troy, NY12 18 0USA
E-mail: [email protected] Evan Thompson, PhD Department of Philosophy University of Toronto 15King’s College Circle
Toronto, ON M5S3H7CANADA E-mail: [email protected] C. Jason Throop, PhD
Department of Anthropology University of California, Los Angeles 3 4 1Haines Hall
Los Angeles, CA9 0 0 9 5 USA E-mail: [email protected]
xiv list of contributors Rebecca Todd, BA
Department of Human Development and Applied Psychology
Ontario Institute for Studies in Education/University of Toronto 2 5 2Bloor Street West
Toronto, Ontario M5S1V6CANADA E-mail: [email protected] Carlo Umilt `a, PhD
Dipartimeto di Psicologia Generale Universita di Padova
via8Febbraio,2-3 5 12 2Padova ITALY E-mail: [email protected] David E. Warren, BSc Department of Psychology University of Illinois 6 0 3E. Daniel Street Champaign, IL6 18 2 0USA E-mail:[email protected] Joel Weinberger, PhD Derner Institute Adelphi University Box7 0 1
Garden City, NY115 3 0USA
E-mail:[email protected]
Drew Westen, PhD Department of Psychology Emory University
5 3 2N. Kilgo Circle Atlanta, GA3 0 3 2 2USA E-mail: [email protected] Dan Zahavi, PhD
Danish National Research Foundation Center for Subjectivity Research Kobmagergade4 6
DK-115 0Copenhagen K DENMARK E-mail: [email protected]
Philip David Zelazo, PhD Department of Psychology University of Toronto 10 0St. George Street
Toronto, ON M5S3G3CANADA E-mail: [email protected] (After September2 0 0 7:
Institute of Child Development University of Minnesota 5 1East River Road
Minneapolis, MN5 5 4 5 5USA E-mail: [email protected])
The Cambridge Handbook of Consciousness
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xvi
C H A P T E R 1
Consciousness: An Introduction
Philip David Zelazo, Morris Moscovitch, and Evan Thompson
The Cambridge Handbook of Consciousness brings together leading scholars from around the world who address the topic of con- sciousness from a wide variety of perspec- tives, ranging from philosophical to anthro- pological to neuroscientific. This handbook is the first of its kind in the field, and its appearance marks a unique time in the his- tory of intellectual inquiry on the topic.
After decades during which consciousness was considered beyond the scope of legiti- mate scientific investigation, consciousness re-emerged as a popular focus of research during the latter part of the last century and it has remained so for more than 2 0 years.
Indeed, there are now so many different lines of investigation on consciousness that the time has come when the field may finally benefit from a book that pulls them together and, by juxtaposing them, provides a com- prehensive survey of this exciting field.
By the mid-19 9 0s, if not earlier, it was widely agreed that one could not get a full appreciation of psychological phenomena – for example, of perception or memory – without distinguishing between conscious and unconscious processes. The antecedents
of this agreement are many, and it would be beyond the scope of this Introduction to do more than highlight a few (for further discussion, see Umilt`a & Moscovitch,19 9 4).
One of the most obvious is the so-called cog- nitive revolution in psychology and the sub- sequent emergence of cognitive science as an interdisciplinary enterprise. Whereas previ- ously psychologists sought to describe law- ful relations between environmental stimuli and behavioral responses, in the mid-19 5 0s or so they began to trace the flow of infor- mation through a cognitive system, viewing the mind as a kind of computer program.
It eventually became clear, however, that by focusing on the processing of information – the kind of thing a computer can do – psychology left out most of what really matters to us as human beings; as conscious subjects, it left us cold. The cognitive revo- lution opened the door to the study of such topics as attention and memory, and some time later, consciousness came on through.
The pre-19 9 0s tendency to avoid discus- sions of consciousness, except in certain con- texts (e.g., in phenomenological philoso- phy and psychoanalytic circles), may have 1
2 the cambridge handbook of consciousness been due, in part, to the belief that con-
sciousness necessarily was a kind of ghost in the machine – one that inevitably courted the awful specter of dualism. Since then, however, our ontological suppositions have evolved, and this evolution may be a conse- quence of the growing trend toward interdis- ciplinary investigation – seen, for example, in the emergence of cognitive science and neu- roscience as coherent fields. The transdisci- plinary perspective afforded by new fields may have engendered an increased open- ness and willingness to explore problems that earlier were deemed too difficult to address. Certainly, it provided the means that made these problems seem soluble.
Indeed, precisely because consciousness is such a difficult problem, progress in solv- ing it probably depends on a convergence of ideas and methodologies: We are unlikely to arrive at an adequate understanding of con- sciousness in the absence of a transdiscipli- nary perspective.
Clinical sciences, and in particular neu- ropsychology, also played a prominent role in helping usher in a new willingness to tackle the problem of consciousness. Vari- ous unusual syndromes came to light in the latter half of the 2 0th century, and these syndromes seemed to demand an explana- tion in terms of consciousness. Blindsight is a good example: In this syndrome, patients with lesions to the occipital lobe of the brain are phenomenologically blind, but can nonetheless perform normally on a number of visual tasks. Another example is amne- sia, in which people who are phenomeno- logically amnesic as a result of damage to medial temporal lobes or the diencephalon can acquire, retain, and recover informa- tion without awareness. Similar examples emerged in other domains, and it soon became clear that processes under con- scious control complement, or compete with, unconscious processes in the control of cognition and behavior. These issues are also beginning to play a major role in the rigorous, scientific analysis of psychopathol- ogy, the one field in which concerns with the role of conscious and unconscious processes have played a steady role since Freud. More-
over, some of these same atypical phenom- ena (e.g., blindsight) have also been demon- strated in non-human animals, raising the possibility that consciousness is not associ- ated exclusively with human beings.
A third prominent contribution to the current state of affairs is the development of new techniques that have made it pos- sible to treat consciousness in a more rig- orous and scientifically respectable fashion.
Foremost among these is the development of neuroimaging techniques that allow us to correlate performance and subjective expe- rience with brain function. These techniques include electrophysiological methods, such as magneto-encephalography (MEG), and various types of functional neuroimaging, including functional magnetic resonance imaging (fMRI). The analytic sophistication of these technologies is growing rapidly, as is the creation of new technologies that will expand our capabilities to look into the brain more closely and seek answers to questions that now seem impossible to address.
There is currently considerable interest in exploring the neural correlates of conscious- ness. There is also a growing realization, however, that it will not be possible to make serious headway in understanding con- sciousness without confronting the issue of how to acquire more precise descriptive first-person reports about subjective expe- rience (Jack & Roepstorff, 2 0 0 3, 2 0 0 4).
Psychologists, especially clinical psycholo- gists and psychotherapists, have grappled with this issue for a long time, but it has gained new prominence thanks to the use of neuroimaging techniques. Here one guid- ing idea is that it may be possible to recover information about the highly variable neu- ral processes associated with conscious- ness by collecting more precise, trial-by- trial first-person reports from experimental participants.
If ever it was possible to do so, cer- tainly serious students of the mind can no longer ignore the topic of conscious- ness. This volume attempts to survey the major developments in a wide range of intellectual domains to give the reader an appreciation of the state of the field and
consciousness: an introduction 3 where it is heading. Despite our efforts to
provide a comprehensive overview of the field, however, there were several unavoid- able omissions. Though we had hoped to include chapters on psychedelic drugs and on split-brain research, in the end we were unable to obtain these chapters in time.
Readers interested in the latest scientific writing on drugs and consciousness may wish to see Benny Shanon’s (2 0 0 2) book on ayahuasca. Michael Gazzaniga’s (19 9 8) book, The Mind’s Past, provides an accessi- ble overview of work on split-brain research and its implications for subjective experi- ence. We note, too, that although we were able to cover philosophical approaches to consciousness from a variety of cultural perspectives, including Continental phe- nomenology and Asian philosophy (particu- larly Buddhism), there were inevitably oth- ers that we omitted. We apologize for these unfortunate gaps.
The volume is organized mainly around a broad (sometimes untenable) distinction between cognitive scientific approaches and neuroscientific approaches. Although we are mindful of the truly transdisiplinary nature of contemporary work on consciousness, we believe this distinction may be useful for readers who wish to use this handbook as an advanced textbook. For example, readers who want a course in consciousness from a cognitive science perspective might concen- trate on Chapters2–2 4. Readers approach- ing the topic from the perspective of neu- roscience might emphasize Chapters2 5–3 1. A more sociocultural course could include Chapters 2–4, 13–15, 19–2 4, and 3 1. More focused topical treatments are also possible.
For example, a course on memory might include Chapters6–8,10,18, and2 9.
The topic of consciousness is relevant to all intellectual inquiry – indeed, it is the foundation of this inquiry. As the chap- ters collected here show, individually and together, by ignoring consciousness, one places unnecessary constraints on our under- standing of a wide range of phenomena – and risks grossly distorting them. Many mys- teries remain (e.g., what are the neural sub- strates of consciousness? are there varieties
or levels of consciousness within domains of functioning, across domains, across species, and/or across the lifespan?), but there has also been considerable progress. We hope this collection serves a useful function by helping readers see both how far we have come in understanding consciousness and how far we have to go.
Acknowledgments
The editors would like to thank Phil Laugh- lin, formerly of CUP, who encouraged us to prepare this volume, and Armi Macaballug and Mary Cadette, who helped us during the final production phases. Dana Liebermann provided valuable assistance as we planned the volume, and Helena Hong Gao helped us pull the many chapters together; we are very grateful to them both. We would also like to thank the contributors for their patience during the editorial process (the scope of this volume threatened, at times, to turn this pro- cess into an editorial nightmare . . . ). Finally, we note with sadness the death of Joseph Bogen, one of the pioneers in research on consciousness. We regret that he was unable to see his chapter in print.
References
Gazzaniga, M. S. (19 9 8).The mind’s past. Berke- ley, CA: University of California Press.
Jack, A. & Roepstorff, A. (Eds.) (2 0 0 3).Trusting the subject? The use of introspective evidence in cognitive science. Vol.1.Thorverton, UK: Imprint Academic.
Jack, A. & Roepstorff, A. (Eds.) (2 0 0 4). Trust- ing the subject? The use of introspective evi- dence in cognitive science. Vol. 2.Thorverton, UK: Imprint Academic.
Shanon, B. (2 0 0 2). The antipodes of the mind:
Charting the phenomenology of the ayahuasca experience. New York: Oxford University Press.
Umilt`a, C. & Moscovitch, M. (Eds.). (19 9 4).Con- scious and nonconscious information processing:
Attention and Performance XV: Conscious and nonconscious processes in cognition. Cambridge, MA: MIT/Bradford Press.
4
P a r t I
THE COGNITIVE SCIENCE OF CONSCIOUSNESS
5
6
A. Philosophy
7
8
C H A P T E R 2
A Brief History of the Philosophical Problem of Consciousness
William Seager
Abstract
The problem of consciousness, generally referred to as the mind-body problem although this characterization is unfortu- nately narrow, has been the subject of philo- sophical reflection for thousands of years.
This chapter traces the development of this problem in Western philosophy from the time of the ancient Greeks to the mid- dle of the 2 0th century. The birth of sci- ence in the 17th century and its subse- quent astounding success made the problem of mind particularly acute, and produced a host of philosophical positions in response.
These include the infamous interactionist dualism of Descartes and a host of dual- ist alternatives forced by the intractable problem of mind-matter interaction; a vari- ety of idealist positions which regard mind as ontologically fundamental; emergentist theories which posit entirely novel enti- ties, events, and laws which ‘grow’ out of the material substrate; panpsychist, double aspect, and ‘neutral monist’ views in which both mind and matter are somehow reflec- tions of some underlying, barely knowable
ur-material; and increasingly sophisticated forms of materialism which, despite fail- ing to resolve the problem of consciousness, seemed to fit best with the scientific view of the world and eventually came to dominate thinking about the mind in the2 0th century.
I. Forms of Consciousness
The term ‘consciousness’ possesses a huge and diverse set of meanings. It is not even obvious that there is any one ‘thing’ that all uses of the term have in common which could stand as its core referent (see Wilkes 19 8 8). When we think about conscious- ness we may have in mind highly complex mental activities, such as reflective self- consciousness or introspective conscious- ness, of which perhaps only human beings are capable. Or we may be thinking about something more purelyphenomenal, perhaps something as apparently simple and uni- tary as a momentary stab of pain. Paradig- matic examples of consciousness are the per- ceptual states of seeing and hearing, but the nature of the consciousness involved is 9
1 0 the cambridge handbook of consciousness actually complex and far from clear. Are
the conscious elements of perception made up only of raw sensations from which we construct objects of perception in a quasi- intellectual operation? Or is perceptual con- sciousness always of ‘completed’ objects with their worldly properties?
The realm of consciousness is hardly exhausted by its reflective, introspective, or perceptual forms. There is distinctivelyemo- tional consciousness, which seems to nec- essarily involve both bodily feelings and some kind of cognitive assessment of them.
Emotional states require a kind of evalua- tion of a situation. Does consciousness thus include distinctive evaluative states, so that, for example, consciousness of pain would involve both bodily sensations and a con- scious sense of aversion? Linked closely with emotional states are familiar, but nonethe- less rather peculiar, states of consciousness that are essentially other directed, notably empathy and sympathy. We visibly wince when others are hurt and almost seem to feel pain ourselves as we undergo this unique kind of experience.
Philosophers argue about whether all thinking is accompanied by or perhaps even constituted out of sensory materials (images have been the traditional favorite candidate material), and some champion the idea of a pure thought-consciousness independent of sensory components. In any event, there is no doubt that thought is something that often happens consciously and is in some way different from perception, sensation, or other forms of consciousness.
Another sort of conscious experience is closely associated with the idea of conscious thought but not identical to it: epistemolog- ical consciousness, or the sense of certainty or doubt we have when consciously enter- taining a proposition (such as ‘2 +3 = 5’ or ‘the word ‘eat’ consists of three letters’).
Descartes famously appealed to such states of consciousness in the ‘method of doubt’
(see hisMeditations16 4 1/19 8 5).
Still another significant if subtle form of consciousness has sometimes been given the name ‘fringe’ consciousness (see Mangan
2 0 0 1, following James 18 9 0/19 5 0, ch. 9), which refers to the background of aware- ness which sets the context for experience.
An example is our sense of orientation or rightness in a familiar environment (consider the change in your state of consciousness when you recognize someone’s face who at first appeared to be a stranger). Moods present another form of fringe conscious- ness, with clear links to the more overtly conscious emotional states but also clearly distinct from them.
But I think there is a fundamental com- monality to all these different forms of con- sciousness. Consciousness is distinctive for its subjectivity or its first-person character.
There is ‘something it is like’ to be in a con- scious state, and only the conscious subject has direct access to this way of being (see Nagel19 7 4). In contrast, there is nothing it is like to be a rock, no subjective aspect to an ashtray. But conscious beings are essentially different in this respect. The huge variety in the forms of consciousness makes the prob- lem very complex, but the core problem of consciousness focuses on the nature of sub- jectivity.
A further source of complexity arises from the range of possible explanatory tar- gets associated with the study of conscious- ness. One might, for instance, primarily focus on the structure or contents of con- sciousness. These would provide a valid answer to one legitimate sense of the ques- tion, What is consciousness? But then again, one might be more interested in how con- sciousness comes into being, either in a developing individual or in the universe at large. Or one might wonder how conscious- ness, seemingly so different from the purely objective properties of the material world studied by physics or chemistry, fits in with the overall scientific view of the world. To address all these aspects of the problem of consciousness would require volumes upon volumes. The history presented in this chap- ter focuses on what has become perhaps the central issue in consciousness studies, which is the problem of integrating subjectivity into the scientific view of the world.
a brief history of the philosophical problem of consciousness 1 1
II. The Nature of the Problem
Despite the huge range of diverse opinion, I think it is fair to say that there is now something of a consensus view about the ori- gin of consciousness, which I call here the mainstreamview. It is something like the fol- lowing. The world is a purely physical sys- tem created some13 billion years ago in the prodigious event that Fred Hoyle labeled the big bang. Very shortly after the big bang the world was in a primitive, ultra-hot, and chaotic state in which normal matter could not exist, but as the system cooled the famil- iar elements of hydrogen and helium, as well as some traces of a few heavier ele- ments, began to form. Then very interesting things started to happen, as stars and galax- ies quickly evolved, burned through their hydrogen fuel, and went nova, in the process creating and spewing forth most of the ele- ments of the periodic table into the increas- ingly rich galactic environments.
There was not a trace of life, mind, or consciousness throughout any of this pro- cess. That was to come later. The mainstream view continues with the creation of plan- etary systems. At first these systems were poor in heavier elements, but after just a few generations of star creation and destruc- tion there were many Earth-like planets scat- tered through the vast – perhaps infinite – expanse of galaxies, and indeed some 7 or 8 billion years after the big bang, the Earth itself formed along with our solar system.
We do not yet understand it very well, but whether in a warm little pond, around a deeply submerged hydrothermal vent, amongst the complex interstices of some clay-like matrix, as a pre-packaged gift from another world, or in some other way of which we have no inkling, conditions on the early Earth somehow enabled the special – though entirely in accord with physical law – chemistry necessary for the beginnings of life.
But even with the presence of life or proto-life, consciousness still did not grace the Earth. The long, slow processes of evolu-
tion by natural selection took hold and ulti- mately led at some time, somewhere to the first living beings that could feel– pain and pleasure, want and fear – and could expe- rience sensations of light, sound, or odors.
The mainstream view sees this radical devel- opment as being conditioned by the evolu- tion of neurological behavior control systems in co-evolutionary development with more capable sensory systems. Consciousness thus emergedas a product of increasing biological complexity, from non-conscious precursors composed of non-conscious components.
Here we can raise many of the cen- tral questions within the problem of con- sciousness. Imagine we were alien exo- biologists observing the Earth around the time of the emergence of consciousness.
How would we know that certain organ- isms were conscious, while other organisms were not? What is it about the conscious organisms that explains why they are conscious? Furthermore, the appearance of conscious beings looks to be a development that sharply distinguishes them from their precursors, but the material processes of evolution are not marked by such radical discontinuities. To be sure, we do find strik- ing differences among extant organisms. The unique human use of language is perhaps the best example of such a difference, but of course the apes exhibit a host of related, potentially precursor abilities, as do human beings who lack full language use. Thus we have possible models of at least some aspects of our prelinguistic ancestors which suggest the evolutionary path that led to language.
But the slightest, most fleeting spark of feeling is a full-fledged instance of conscious- ness which entirely differentiates its posses- sor from the realm of the non-conscious.
Note here a dissimilarity to other biologi- cal features. Some creatures have wings and others do not, and we would expect that in the evolution from wingless to winged there would be a hazy region where it just would not be clear whether or not a cer- tain creature’s appendages would count as wings or not. Similarly, as we consider the
1 2 the cambridge handbook of consciousness evolutionary advance from non-conscious to
conscious creatures, there would be a range of creatures about which we would be unclear whether they were conscious or not.
But in this latter case, there is a fact whether or not the creatures in that range are feeling anything, however dimly or weakly, whereas we do not think there must be a fact about whether a certain appendage is or is not a wing (a dim or faint feeling is10 0% a kind of consciousness, but a few feathers on a fore- limb is not a kind of wing). It is up to us whether to count a certain sort of appendage as a wing or not – it makes no difference, so to speak, to the organism what we call it.
But it is not up to us to decide whether or not organism X does or does not enjoy some smidgen of consciousness – it either does or it does not.
Lurking behind these relatively empiri- cal questions is a more basic theoretical, or metaphysical, issue. Given that crea- tures capable of fairly complex behavior were evolving without consciousness, why is consciousness necessary for the contin- ued evolution of more complex behavior?
Just as wings are an excellent solution to the problem of evolving flight, brains (or more generally nervous systems) are won- derful at implementing richly capable sen- sory systems and coordinated behavior con- trol systems. But why should these brains be conscious? Although perhaps of doubt- ful coherence, it is useful to try to imag- ine our alien biologists as non-conscious beings. Perhaps they are advanced machines well programmed in deduction, induction, and abduction. Now, why would they ever posit consciousness in addition to, or as a feature of, complex sensory and behavioral control systems? As Thomas Huxley said,
‘How it is that anything so remarkable as a state of consciousness comes about as a result of irritating nervous tissue, is just as unaccountable as the appearance of Djin when Aladdin rubbed his lamp’ (18 6 6, 8, 2 10). We might, rather fancifully, describe this core philosophical question about con- sciousness as how the genie of conscious- ness gets into the lamp of the brain, or why, to use Thomas Nagel’s (19 7 4) famous
phrase, there is ‘something it is like’ tobea conscious entity?
III. Ancient Hints
Of course, the mainstream view has not long been mainstream, for the problem of consciousness cannot strike one at all until a fairly advanced scientific understanding of the world permits development of the materialism presupposed by the mainstream view. A second necessary condition is sim- ply the self-recognition that we are con- scious beings possessing a host of mental attributes. And that conception has been around for a long time. Our ancestors ini- tiated a spectacular leap in conceptual tech- nology by devising what is nowadays called folk psychology. The development of the concepts of behavior explaining states such as belief and desire, motivating states of pleasure and pain, and information-laden states of perceptual sensation, as well as the complex links amongst these concepts, is perhaps the greatest piece of theorizing ever produced by human beings. The power and age of folk psychology are attested by the universal animism of preliterate peo- ples and the seemingly innate tendencies of very young children to regard various natural or artificial processes as exemplify- ing agency (see, among many others, Bloom 2 0 0 4; Gergeley et al.19 9 5; Perner19 9 1). The persistence of the core mentalistic notions of goal and purpose in Aristotle’s proto- scientific but highly sophisticated theoriz- ing also reveals the powerful hold these con- cepts had, and have, on human thought. But to the extent that mentalistic attributes are regarded as ubiquitous, no special problem of relating the mental to the non-mental realm can arise, for there simply is no such realm.
But interesting hints of this problem arise early on in philosophy, as the first glim- merings of a naturalistic world view occur.
A fruitful way to present this history is in terms of a fundamental divergence in thought that arose early and has not yet died out in current debate. This is the contrast
a brief history of the philosophical problem of consciousness 1 3 between emergence and panpsychism. The
mainstream view accepts emergence: mind or consciousness appeared out of non- conscious precursors and non-conscious components (note there is both a synchronic and diachronic sense of emergence). Panpsy- chism is the alternative view that emergence is impossible and mind must be already and always present, in some sense, throughout the universe (a panpsychist might allow that mind emerges in the trivial sense that the universe may have been created out of noth- ing and hence out of ‘non-consciousness’;
the characteristically panpsychist position here would be that consciousness must have been created along with whatever other fundamental features of the world were put in place at the beginning). Of course, this divergence transcends the mind-body problem and reflects a fundamental differ- ence in thinking about how the world is structured.
The Presocratic philosophers who flour- ished some2,5 0 0 years ago in the Mediter- ranean basin were the first in the West to conceive of something like a scientific approach to nature, and it was their con- ception that eventually led to what we call science. Although their particular theories were understandably crude and often very fanciful, they were able to grasp the idea that the world could be viewed as composed out of elemental features, whose essential char- acterization might be hidden from human senses and which acted according to constant and universal principles or laws.
The Presocratics immediately recognized the basic dilemma: either mind (or, more generally, whatever apparently macroscopic, high-level, or non-fundamental property is at issue) is an elemental feature of the world, or it somehow emerges from, or is condi- tioned by, such features. If one opts for emer- gence, it is incumbent upon one to at least sketch the means by which new features emerge. If one opts for panpsychism (thus broadly construed), then one must account for the all too obviously apparent total lack of certain features at the fundamental level.
For example, Anaxagoras (c. 5 0 0–4 2 5 bce) flatly denied that emergence was possible
and instead advanced the view that ‘every- thing is in everything’. Anaxagoras explained the obvious contrary appearance by a
‘principle of dominance and latency’ (see Mourelatos19 8 6), which asserted that some qualities were dominant in their contri- bution to the behaviour and appearance of things. However, Anaxagoras’s views on mind are complex because he apparently regarded it as uniquely not containing any measure of other things and thus not fully in accord with his mixing principles. Per- haps this can be interpreted as the asser- tion that mind is ontologically fundamen- tal in a special way; Anaxagoras did seem to believe that everything has some por- tion of mind in it while refraining from the assertion that everything has a mind (even this is controversial; see Barnes19 8 2, 4 0 5 ff.).
On the other hand, Empedocles, an almost exact contemporary of Anaxagoras, favoured an emergentist account based upon the famous doctrine of the four elements:
earth, air, fire and water. All qualities were to be explicated in terms of ratios of these elements. The overall distribution of the elements, which were themselves eternal and unchangeable, was controlled by ‘love and strife’, whose operations are curiously reminiscent of some doctrines of mod- ern thermodynamics, in a grand cyclically dynamic universe. It is true that Empedo- cles is sometimes regarded as a panpsy- chist because of the universal role of love and strife (see Edwards 19 6 7, for exam- ple), but there seems little of the mental in Empedocles’s conceptions, which are rather more like forces of aggregation and dis- aggregation, respectively (see Barnes 19 8 2, 3 0 8 ff.).
The purest form of emergentism was pro- pounded by the famed atomist Democritus (c. 4 6 0–3 7 0 bce). His principle of emer- gence was based upon the possibility of multi-shaped, invisibly tiny atoms interlock- ing to form an infinity of more complex structures. But Democritus, in a way echo- ing Anaxagoras and perhaps hinting at the later distinction between primary and sec- ondary properties, had to admit that the
1 4 the cambridge handbook of consciousness qualities of experience (what philosophers
nowadays call qualia, the subjective fea- tures of conscious experience) could not be accounted for in this way and chose, ulti- mately unsatisfactorily, to relegate them to non-existence: ‘sweet exists by convention, bitter by convention, in truth only atoms and the void’. Sorely missed is Democritus’s account of how conventions themselves – the consciously agreed upon means of com- mon reference to our subjective responses – emerge from the dancing atoms (thus, the ideas of Democritus anticipate the reflex- ive problem of modern eliminativist mate- rialists [e.g., Churchland 19 8 1] who would enjoin us to consciously accept a view which evidently entails that there is no such thing as conscious acceptance of views – see Chapter3).
What is striking about these early strug- gles about the proper form of a scientific understanding of the world is that the mind and particularly consciousness keep rising as special problems. It is sometimes said that the mind-body problem is not an ancient philosophical issue on the basis that sensa- tions were complacently regarded as bod- ily phenomena (see Matson 19 6 6), but it does seem that the problem of conscious- ness was vexing philosophers 2,5 0 0 years ago, and in a form redolent of contem- porary worries. Also critically important is the way that the problem of conscious- ness inescapably arises within the context of developing an integrated scientific view of the world.
The reductionist strain in the Presocratics was not favoured by the two giants of Greek philosophy, Plato and Aristotle, despite their own radical disagreements about how the world should be understood. Plato utterly lacked the naturalizing temperament of the Presocratic philosophers, although he was well aware of their efforts. He explicitly criti- cizes Anaxagoras’s efforts to provide natural- istic, causal explanations of human behavior (seePhaedo, Plato19 6 1).
Of course, Plato nonetheless has a signifi- cant role in the debate because he advances positive arguments in favour of the thesis that mind and body are distinct. He also
provides a basic, and perpetually influen- tial, tri-component-based psychological the- ory (seeRepublic, Book4, Plato19 6 1). These facets of his thought illustrate the two basic aspects of the problem of consciousness: the ontological question and the issue of how mind is structured. Plato’s primary motiva- tion for accepting a dualist account of mind and body presumably stems from the doc- trine of theforms. These are entities which in some way express the intrinsic essence of things. The form of circle is that which our imperfect drawings of circles imitate and point to. The mind can grasp this form, even though we have never perceived a true cir- cle, but only more or less imperfect approx- imations. The ability of the mind to com- mune with the radically non-physical forms suggests that mind itself cannot be physical.
In thePhaedo, Plato (putting words in the mouth of Socrates) ridicules the reduction- ist account of Anaxogoras which sees human action as caused by local physical events. In its place, the mind is proposed as the final (i.e., teleological) cause of action, merely conditioned or constrained by the physical:
‘if it were said that without such bones and sinews and all the rest of them I should not be able to do what I think is right, it would be true. But to say that is because of them that I do what I am doing, and not through choice of what is best – although my actions are controlled by mind – would be a very lax and inaccurate form of expression’ (Phaedo, 9 8b ff.).
In general, Plato’s arguments for dualism are not very convincing. Here’s one. Life must come from death, because otherwise, as all living things eventually die, everything would eventually be dead. Life can come from death only if there is a distinct ‘compo- nent’, responsible for something being alive, that persists through the life-death-life cycle.
That persistent component is soul or mind (Phaedo 7 2c-d). Another argument which Plato frequently invokes (or presupposes in other argumentation) is based on reincarna- tion. If we grant that reincarnation occurs, it is a reasonable inference that something persists which is what is reincarnated. This is a big ‘if’ to modern readers of a scientific
a brief history of the philosophical problem of consciousness 1 5 bent, but the doctrine of reincarnation was
widespread throughout ancient times and is still taken seriously by large numbers of people. The kernel of a more powerful argument for dualism lurks here as well, which was deployed by Descartes much later (see below).
Aristotle is famously more naturalisti- cally inclined than Plato (Raphael’sSchool of Athensshows Plato pointing upward to the heavens while Aristotle gestures downward to Earth as they stare determinedly at each other). But Aristotle’s views on mind are complex and obscure; they are certainly not straightforwardly reductionist (the soul is not, for example, a particularly subtle kind of matter, such as fire). Aristotle’s metaphysics deployed a fundamental distinction between matter and form, and any object necessar- ily instantiates both. A statue of a horse has its matter, bronze, and its form, horse.
Aristotle is not using Plato’s conception of form here. The form of something is not an other-world separate entity, but something more like the way in which the matter of something is organized or structured. Nor by matter does Aristotle mean the fundamental physical stuff we refer to by that word; mat- ter is whatever relatively unstructured stuff is ‘enformed’ to make an object (English retains something of this notion in its use of matter to mean topic), so bronze is the matter of a statue, but soldiers would be the matter of an army. Objects can differ in mat- ter, but agree in form (two identical pictures, one on paper and another on a computer screen) or vice versa. More abstractly, Aris- totle regardedlifeas the form of plants and animals and named the form of living things soul(‘the form of a natural body having life potentially within it’19 8 4,De Anima, bk.2, ch. 1). Aristotle’s views have some affinity both with modern biology’s conception of life and the doctrine of psychophysical func- tionalism insofar as he stresses that soul is not a separate thing requiring another onto- logical realm, but also cannot be reduced to mere matter because its essential attribute is function and organization (for a close and skeptical look at the link between Aristo- tle’s philosophy and modern functionalism
see Nelson 19 9 0; see also Nussbaum and Putnam19 9 2).
Yet there are elements of Aristotle’s account that are not very naturalistic. Early in the De Anima Aristotle raises the pos- sibility that the relation between the body and the mind is analogous to that between sailor and ship, which would imply that mind is independent of body. Later Aristotle apparently endorses this possibility when he discusses, notoriously obscurely, the ‘active intellect’ – the ‘part’ of the soul capable of rational thought (De Anima, bk.3, chs.4– 5). Aristotle clearly states that the active intellect is separable from body and can exist without it. For Aristotle, like Plato, the problematic feature of mind was its capac- ity for abstract thought and not conscious- ness per se, although of course these thinkers were implicitly discussingconsciousthought and had no conception of mind apart from consciousness.
Discussion of one particular, and highly interesting if perennially controversial, fea- ture of consciousness can perhaps be traced to Aristotle. This is the self-intimating or self-representing nature of all conscious states. Many thinkers have regarded it as axiomatic that one could not be in a con- scious state without being aware of that state, and Aristotle makes some remarks that suggest he may belong to this school of thought. For example, in Book Three ofDe AnimaAristotle presents, rather swiftly, the following regress argument:
Since we perceive that we see and hear, it is necessarily either by means of the seeing that one perceives that one sees or by another [perception]. But the same [perception] will be both of the seeing and of the colour that underlies it, with the result that either two [perceptions] will be of the same thing, or it [the perception] will be of itself. Further, if the perception of seeing is a different [perception], either this will pro- ceed to infinity or some [perception] will be of itself; so that we ought to posit this in the first instance.
The passage is somewhat difficult to inter- pret, even in this translation from Vic- tor Caston (2 0 0 2) which forms part of an
1 6 the cambridge handbook of consciousness intricate (and controversial) mixed philo-
sophical, exegetical, and linguistic argument in favor of the view that Aristotle accepted a self-representational account of conscious states which possessed unique phenomenal properties. Aristotle’s argument appears to be that if it is essential to a conscious state that it be consciously apprehended then con- scious states must be self-representing on pain of an infinite regress of states, each representing (and hence enabling conscious apprehension of) the previous state in the series. The crucial premise that all mental states must be conscious is formally neces- sary for the regress. Modern representational accounts of consciousness which accept that conscious states are self-intimating, such as the Higher Order Thought theory, can block the regress by positing non-conscious thoughts which make lower order thoughts conscious by being about them (see Seager 19 9 9, Chapter3, and see Chapters3and4, this volume).
IV. The Scientific Revolution
Although the philosophy of the Middle Ages was vigorous and compendious, the prob- lem of fitting consciousness into the natu- ral world did not figure prominently (for an argument, following in the tradition of Mat- son 19 6 6, that the medievals’ views on the nature of sensation precluded the recogni- tion of at least some versions of the mind- body problem, see King2 0 0 5). There were many acute studies of human psychology and innovative theoretical work on the con- tent and structure of consciousness and cog- nition. Of special note is the 4th-century philosopher and Church Father, St. Augus- tine (3 5 4–4 3 0 ce). His writings exhibit important insights into the phenomenology of consciousness, especially with regard to the experience of time, will, and the self (see especiallyConfessionsandOn Free Will;
4 0 0/19 9 8,4 2 6/19 9 8). He was one of the first philosophers to address the problem of other minds, arguing on the basis of introspection and analogy that because others behave as he behaves when he is aware of being in a
certain mental state, they too have mental states. In addition, he anticipated certain key features of Descartes’ dualistic account of human beings, including Descartes’ famous argument from his conscious self-awareness to the certainty of his own existence (City of God, Bk.11, Ch.2 1) and the idea that mind and body, although ontologically entirely distinct, somehow are united in the human person. Here Augustine also broaches one of the key puzzles of Cartesian dualism where he admits the ‘mode of union’ by which bodies and spirits are bound together to become animals is ‘beyond the comprehen- sion of man’ (City of God, Bk. 2 1, Ch. 10).
Although we see here that Augustine did not agree with Descartes in denying minds to animals, we can also note the complete lack of any idea that this mystery poses any special problem for our understanding of the natural world (see O’Daly19 8 7for a detailed discussion of Augustine’s philosophy of mind).
In fact, the tenets of Christian dogma, eventually wedded to a fundamentally Aris- totelian outlook, conspired to suppress any idea that consciousness or mind could be, should be, or needed to be explained in natu- ralistic terms. It was the scientific revolution of the16th and17th centuries that forced the problem into prominence.
Galileo’s distinction between primary and secondary properties, crucial for the development of science insofar as it freed sci- ence from a hopelessly premature attempt to explain complex sensible qualities in mechanical terms, explicitly set up an oppo- sition between matter and consciousness: ‘I think that tastes, odors, colors, and so on are no more than mere names so far as the object in which we place them is concerned, and that they reside only in the consciousness.
Hence if the living creature were removed all these qualities would be wiped away and annihilated’ (16 2 3/19 5 7,2 7 4). The welcome consequence is that if there are therefore no colors in the world then science is free to ignore them. That was perhaps good tactics in Galileo’s time, but it was a strategic time bomb waiting to go off when science could no longer delay investigating the mind itself.
a brief history of the philosophical problem of consciousness 1 7 The mind-body problem in its modern
form is essentially the work of a single genius, Ren´e Descartes (15 9 6–16 5 0), who reformed the way we think about mind and conscious- ness, leaving us with a set of intuitions that persist to this day. To take just one topi- cal example, the basic idea behind the fic- tional technology of theMatrixfilms is thor- oughly Cartesian: what we experience is not directly related to the state of the environ- ment, but is instead the result of a com- plex function – involving essential sensory and cognitive mediation based upon neural systems – from the environment to our cur- rent state of consciousness. Thus two brains that are in identical states ought to be in the same state of consciousness, no matter what differences there are in their respec- tive environments. It now seems intuitively obvious that this is correct (so contemporary philosophers make exotic and subtle argu- ments against it) and that, to take another stock philosophical example, a brain in a vat, if kept alive in an appropriate chemical bath and if fed proper input signals into its sev- ered nerve endings (cleverly coupled to the output of the brain’s motor output nerves), would have experiences which could be indistinguishable from, say, those you are having at this very moment. This thought experiment reveals another of the reforma- tions of philosophy instituted by Descartes:
the invention of modern epistemology, for how could youknowthat you are not such a brain in a vat.
Descartes was of course also one of the creators of the scientific revolution, pro- viding seminal efforts in mathematics and physics. But he also saw with remarkable prevision the outlines of neuropsychology.
With no conception of how the nervous system actually works and instead deploy- ing a kind of hydraulic metaphor, Descartes envisioned nerve-based sensory and cogni- tive systems and a kind of network struc- ture in the brain, even – anticipating Hebb – suggesting that connections in the brain are strengthened through associated activa- tion. His notorious discussion of animals as machines can be seen as the precursor of a materialist account of cognition.
But Descartes is most remembered and reviled for his insistence upon the strict separation of mind and body which, we are enjoined to believe, required sunder- ing the world itself into radically dis- tinct realms, thereby fundamentally splitting human beings from nature (including their own), denigrated emotion in favour of rea- son, and inspired a lack of respect for animals and nature in general. Why was Descartes a dualist? Some have suggested that Descartes lacked the courage to follow his science to its logical and materialist conclusion (the fate of Galileo is said to have had a strong effect on him, or it may be that Descartes really had no wish to harm the Catholic church). But Descartes did have arguments for his dual- ism, some of which still have supporters.
These arguments also set out one of the basic strategies of anti-materialism.
To show that mind and body are distinct, it will suffice to show that mind has some property that matter lacks. The general prin- ciple here, which is that of the alibi, was cod- ified by another 17th-century philosopher, Gottfried Leibniz (16 4 6–17 16) and is now known as Leibniz’s Law: if x has a property which y lacks, then x and y are not iden- tical. Descartes argued, for example, that although matter is extended in space, mind takes up no space at all. Thus, they could not be identical. It certainly does seem odd to ask how many cubic centimeters mymind takes up (does a broad mind take up more space than a narrow one?). But it is not obvi- ous that this question is anything more than merely a feature of the conventional way we think about minds. An analogy would be an argument that machines cannot think because they are not alive; there is no par- ticular reason to think that the heretofore constant and evident link between life and thought represents anything more than a kind of accident in the way minds happened to be created. In any event, thisstrategyis still at the core of the problem of consciousness.
One current line of argument, for example, contends that consciousness has a kind of first-person subjectivity (the ‘what it is like’
to experience something), whereas matter is purely third-person objective – hence
1 8 the cambridge handbook of consciousness consciousness and matter must be funda-
mentally different phenomena.
Descartes, in the sixth of hisMeditations (16 4 1/19 8 5), also invented an astonishingly novel kind of argument for dualism. The argument is couched in theological terms, but that was merely for purposes of clarity and forcefulness (in the17th century, using God to explain one’s argument was impec- cable rhetoric). Descartes asked us to con- sider whether it was at leastpossiblethat God could destroy one’s body while leaving one’s mind intact. If it was possible then of course God could perform the feat if He wished.
But nothing can be separated from itself! So if it is merely possible that God could sunder mind from body, then they must already be different things. So, anyone who thinks that, say, a consciousness persisting after bodily death is even so much as a bare possibil- ity already thinks that consciousness is not a physical phenomenon. This argument is valid, but it has a little flaw: how do we know that what we think is possible is truly so? Many are the mathematicians labouring to prove theorems which will turn out to be unprovable (think of the centuries-long effort to square the circle) – what do they think they are doing? Nonetheless, it is a highly interesting revelation that the mere possibility of dualism (in the sense consid- ered here) entails that dualism is true.
Cartesian dualism also included the doc- trine of mind-body interaction. This seems like common sense: when someone kicks me, that causes me to feel pain and anger, and then it is my anger that makes me kick them back. Causation appears to run from body to mind and back again. But as soon as Descartes propounded his theory of mind, this interaction was seen to be deeply problematic. One of Descartes’ aristocratic female correspondents, the Princess Elisa- beth of Palatine, asked the crucial question:
“How can the soul of man determine the spirits of the body, so as to produce voluntary actions (given that the soul is only a thinking substance)?” (from a letter of May16 4 3). It’s a fair question and Descartes’ only answer was that the mind-body union was instituted and maintained by God and was humanly
incomprehensible. The Princess allowed her- self less thanfullysatisfied with this reply.
It was also noticed that Descartes’ dual- ism conflicted with the emerging under- standing of the conservation of certain physical quantities. Descartes himself only accepted that the total amount, but not direction, of motion was conserved. Thus the mind’s ability to wiggle the pineal gland (where Descartes posited the seat of the soul) would redirect motion without vio- lating natural law. But it was soon discov- ered that it was momentum – or directed motion – that is conserved, and thus the mind-induced motion of the pineal gland would indeed contradict the laws of nature (one might try to regard this as a fea- ture rather than a bug, because at least it makes Descartes’ theory empirically testable in principle).
In addition to the ontological aspect of his views, Descartes had some interesting insights into the phenomenological side of consciousness. For Descartes, the elements of conscious experience are what he called
‘ideas’ (Descartes pioneered the modern use of this term to stand for mental items), and every idea possesses two kinds of reality:
formal and objective. The formal reality of something is simply what it is in itself, whereas the objective reality is what, if any- thing, it represents (so, the formal reality of a picture of a horse is paper and paint; a horse is the objective reality). Though Descartes is often pilloried as one who believed that we are only ever conscious of our own ideas, it is far from clear that this is Descartes’
position. It is possible to read him instead as a precursor of modern representational theories of consciousness [see Chapter 3], in which it is asserted that, although con- sciousness essentially involves mental rep- resentation, what we are conscious of is not the representations themselves but their content (rather in the way that although we must use words to talk about things, we are not thereby always talking about words). Descartes says that ‘there cannot be any ideas which do not appear to represent some things . . . ’ (Meditation3), and perhaps this suggests that even in cases of illusion
a brief history of the philosophical problem of consciousness 1 9 Descartes’ view was that our experience is
of the representational content of the ideas and that we do not, as it were, see our own ideas.
Finally, because Descartes is often misrep- resented as denigrating bodily feelings and emotions in favour of pure reason, it is worth pointing out that he developed a sophisti- cated account of the emotions which stresses both their importance and the importance of the bodily feelings which accompany them (16 4 9/19 8 5). Descartes – perhaps con- tra Aristotle – strenuously denied that the mind was ‘in’ the body the way a pilot is in a ship, for the intimate connection to the body and the host of functionally significant feelings which the body arouses in the mind in the appropriate circumstances meant that the mind-body link was not a mere commu- nication channel. Descartes declared instead that the mind and body formed a ‘substan- tial union’ and that emotional response was essential to cognition.
Despite the fact that if one is willing to endorse a dualism of mind and body then Descartes’ interactive version seems to be the most intuitively reasonable, the difficulties of understanding how two such entirely distinct realms could causally inter- act created an avid market for alternative theories of the mind-body relation. Two broad streams of theory can be discerned, which I label, not altogether happily, ide- alist and materialist. Idealists regard mind or consciousness as the fundamental exis- tent and deny the independent existence of the material world; its apparent reality is to be explained as a function of mental- ity. Materialists cannot follow such a direct route, for they have great difficulty in out- right denying the existence of mind and generally content themselves with in some way identifying it with features of matter.
The asymmetry in these positions is inter- esting. Idealists can easily assert that the material world is all illusory. Materialists fall into paradox if they attempt the same strat- egy – for the assertion that mind is illu- sory presupposes the existence of illusions, which a
