the mit press emergence contemporary readings in philosophy and science apr 2008

Emergence

Emergence: Contemporary Readings in Philosophy and Science
edited by Mark A. Bedau and Paul Humphreys
A Bradford Book
The MIT Press
Cambridge, Massachusetts
London, England
( 2008 Massachusetts Institute of Technology
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Library of Congress Cataloging-in-Publication Data
Emergence : contemporary readings in philosophy and science / edited by Mark A. Bedau and
Paul Humphreys.
p. cm.
‘‘A Bradford book.’’
Includes bibliographical references and (p. ) index.
ISBN 978-0-262-02621-5 (hardcover : alk. paper) — ISBN 978-0-262-52475-9
(pbk. : alk. paper)
1. Emergence (Philosophy) 2. Science—Philosophy. I. Bedau, Mark. II. Humphreys, Paul.
Q175.32.E44E44 2007
501—dc22 2007000949
10987654321
Contents
Preface ix
Acknowledgments xi

Sources xiii
Introduction 1
I Philosophical Perspectives on Emergence 7
Introduction to Philosophical Perspectives on Emergence
1 The Rise and Fall of British Emergentism 19
Brian P. McLaughlin
2 On the Idea of Emergence 61
Carl Hempel and Paul Oppenheim
3 Reductionism and the Irreducibility of Consciousness 69
John Searle
4 Emergence and Supervenience 81
Brian P. McLaughlin
5 Aggregativity: Reductive Heuristics for Finding Emergence 99
William C. Wimsatt
6 How Properties Emerge 111
Paul Humphreys
7 Making Sense of Emergence 127
Jaegwon Kim
8 Downward Causation and Autonomy in Weak Emergence 155
Mark A. Bedau
9 Real Patterns 189
Daniel C. Dennett
II Scientific Perspectives on Emergence 207
Introduction to Scientific Perspectives on Emergence
10 More Is Different: Broken Symmetry and the Nature of the Hierarchical Structure
of Science 221
P. W. Anderson
11 Emergence 231
Andrew Assad and Norman H. Packard
12 Sorting and Mixing: Race and Sex 235

Thomas Schelling
13 Alternative Views of Complexity 249
Herbert Simon
14 The Theory of Everything 259
Robert B. Laughlin and David Pines
15 Is Anything Ever New? Considering Emergence 269
James P. Crutchfield
16 Design, Observation, Surprise! A Test of Emergence 287
Edmund M. A. Ronald, Moshe Sipper, and Mathieu S. Capcarre
`
re
17 Ansatz for Dynamical Hierarchies 305
Steen Rasmussen, Nils A. Baas, Bernd Mayer, and Martin Nillson
III Background and Polemics 335
Introduction to Background and Polemics
18 Newtonianism, Reductionism, and the Art of Congressional Testimony 345
Stephen Weinberg
19 Issues in the Logic of Reductive Explanations 359
Ernest Nagel
20 Chaos 375
James P. Crutchfield, J. Doyne Farmer, Norman H. Packard, and Robert S. Shaw
21 Undecidability and Intractability in Theoretical Physics 387
Stephen Wolfram
vi Contents
22 Special Sciences (Or: The Disunity of Science as a Working Hypothesis) 395
Jerry Fodor
23 Supervenience 411
David Chalmers
24 The Nonreductivist’s Troubles with Mental Causation 427
Jaegwon Kim

Annotated Bibliography 447
About the Authors 455
Index 459
Contents vii

Preface
Thirty years ago emergence was largely ignored in philosophy and science. Its ethos
ran counter to the reductionist views of the time, and it seemed to invoke mystical
and unexplainable levels of reality. Things have changed. Emergence is now one of
the liveliest areas of research in both science and philosophy. This activity holds out
great promise for understanding a wide variety of phenomena in ways that are intrigu-
ingly different from more traditional approaches. The reason for this change is compli-
cated, but it results in part from developments in a number of vigorous and successful
research programs within complexity theory, artificial life, physics, psychology, sociol-
ogy, and biology. In parallel, although often driven by independent developments in
the philosophy of science and the philosophy of mind, philosophers have been devel-
oping new conceptual tools for understanding emergent phenomena.
This book covers the principal approaches to emergence found in contemporary phi-
losophy and science. All of the chapters are contemporary classics that either have
played a significant role in the development of thinking about emergence or capture
and refine widely held pretheoretical positions on emergence. They originally were
published in widely scattered and intellectually diverse sources. This volume for the
first time collects them all in one easily accessible place. We have included selections
that represent most, if not all, of the major contemporary approaches to emergence.
However, in emphasizing the interactions between the philosophical and scientific
approaches to emergence, we are striking out deliberately in a particular direction. For
entirely understandable reasons, much of the recent philosophical literature on emer-
gence, not to mention the broader public’s attention, has been motivated by an inter-
est in whether specifically mental features, such as consciousness, emerge from brain
states and properties. We have included selections from that tradition, but we believe

that progress in understanding emergence will be helped by a familiarity with work in
areas outside psychology and the philosophy of mind. By understanding how emer-
gent phenomena occur and are represented in physics and artificial life, for example,
those with a philosophical interest in the subject can acquire a broader perspective on
what is peculiar to emergence. Conversely, the abstractness and conceptual clarity
characteristic of philosophy can provide a much broader perspective from which scien-
tists can see connections with kinds of emergence that lie outside their own disciplines.
And so this collection has a variety of intended audiences. It aims to be informative
to both philosophers and scientists, but we also hope that many others, including stu-
dents, will find the selections helpful and thought provoking. Most of the chapters can
be understood by an intelligent reader who is not an expert in the specific discipline
represented by a given author, and the third section can be used as a reference source
on somewhat more specialized topics. Although we believe that our ordering provides
a natural progression of ideas within each section, readers with different backgrounds
no doubt will find it natural to begin with different sections. Our part introductions
put the chapters into context, explain how they are connected, and pose some key
questions for further exploration. The chapters in this book form only the tip of the
iceberg of the emergence literature in contemporary philosophy and science, and fur-
ther reading material is listed in the bibliography. Those who wish to use the collection
as the basis for a course or seminar on emergence in some specific area easily can sup-
plement our readings with more specialized and technical material.
Above all, we have endeavored to include selections that provide constructive and
useful methods for understanding emergence. Throughout the introductions, we have
posed questions, many of them currently lacking definitive answers. We hope that
readers who work through this book will be well positioned to advance and eventually
solve those problems.
Our book has an associated Web site containing supplementary material. Among
other things, the site contains links to software including flocking and schooling sim-
ulations, the Game of Life, and self-organizing systems, as well as links to other reputa-
ble sites on emergence. We encourage readers to download and experiment with the

simulations because many aspects of emergence have an essentially dynamic compo-
nent that can only be understood through firsthand experience. The site also contains
links to some classic publications that are now in the public domain, and updates
about important new publications on emergence will be added periodically. As new
resources arise over time, the site will grow and evolve. The Web site can be found at:
/>Mark A. Bedau
Paul Humphreys
x Preface
Acknowledgments
The editors would like to thank a number of friends and colleagues from whom we
have received valuable assistance while developing this anthology. For organizing the
Paris conference on emergence where we met and learned of our shared perspective,
we thank: Anouk Barberousse, Jacques Dubucs, and Philippe Huneman. For feedback
on contents: Andreas Hutteman, Jenann Ismael, Sandy Mitchell, Norman Packard,
and Bill Wimsatt. For secretarial help: Kathy Kennedy and Amanda Waldroupe. For fi-
nancial support at a critical final stage: Stillman Drake funds from the Dean of Faculty
at Reed College. Mark Bedau would like to thank colleagues at ProtoLife Srl, Reed Col-
lege, the Santa Fe Institute, and the European Center for Living Technology for valu-
able and enjoyable discussions on emergence and related topics. Paul Humphreys
would also like to thank members of the Institute d’Histoire et de Philosophie des
Sciences et des Techniques (Paris) and of the Keswick Society for extensive discussions
on emergence, complexity, and related topics.

Sources
Grateful acknowledgment is made to the following publishers and authors:
1. ‘‘The Rise and Fall of British Emergentism’’ by Brian P. McLaughlin, from Emergence
or Reduction?: Essays on the Prospects of Nonreductive Physicalism, edited by Beckerman,
Flohr, and Kim. Copyright ( 1992 by Walter de Gruyter GmbH & Co. Reprinted by
permission of Walter de Gruyter GmbH & Co. and Brian P. McLaughlin.
2. ‘‘On the Idea of Emergence’’ by Carl Hempel and Paul Oppenheim, from Aspects of

Scientific Explanation and other Essays in the Philosophy of Science by Carl Hempel. Copy-
right ( 1965 by the Free Press. Reprinted by permission of the University of Chicago
Press.
3. ‘‘Reductionism and the Irreducibility of Consciousness’’ by John Searle from The
Rediscovery of the Mind. Copyright ( 1992 by the MIT Press. Reprinted by permission
of the MIT Press and John Searl.
4. Excerpt from ‘‘Emergence and Supervenience’’ by Brian P. McLaughlin, from Intel-
lectica 25 (1997), edited by Rosenthal. Copyright ( 1997 by Intellectica. Reprinted by
permission of Intellectica and Brian P. McLaughlin.
5. ‘‘Aggregativity: Reductive Heuristics for Finding Emergence’’ by William C. Wim-
satt, from Philosophy of Science 64(4): Suppl.2: S372–S384 (1997), edited by Dickson.
Copyright ( 1997 by the University of Chicago Press. Reprinted by permission of the
University of Chicago Press and William C. Wimsatt.
6. ‘‘How Properties Emerge’’ by Paul Humphreys, from Philosophy of Science 64 (1997).
Copyright ( 1997 by the Philosophy of Science Association. All rights reserved.
Reprinted by permission of the author.
7. ‘‘Making Sense of Emergence’’ by Jaegwon Kim from Philosophical Studies 95 (1999) ,
edited by Cohen. Copyright ( 1999 by Springer Science and Business Media.
Reprinted by permission of Springer Science and Business Media and Jaegwon Kim.
8. ‘‘Downward Causation and Autonomy in Weak Emergence’’ by Mark A. Bedau,
from Principia Revista Internacional de Epistemologica 6 (2003), edited by Dutra.
Copyright ( by Principia Revista Internacional de Epistemologica. Reprinted by permis-
sion of Principia Revista Internacional de Epistemologica and Mark A. Bedau.
9. Excerpt from ‘‘Real Patterns’’ by Daniel C. Dennett from The Journal of Philosophy 87
(1991), edited by Smylie. Copyright ( 1991 by the Journal of Philosophy, Inc.
Reprinted by permission of the Journal of Philosophy, Inc. and by Daniel C. Dennett.
10. ‘‘More is Different’’ by P. W. Anderson from Science 177 (1972), edited by Ken-
nedy. Copyright ( 1972 by the American Association for the Advancement of
Science. Reprinted by permission of the American Association for the Advancement
of Science and P. W. Anderson.

11. Excerpt from ‘‘Emergent Colonization in an Artificial Ecology’’ by Andrew Assad
and Norman H. Packard from Towards a Practice of Autonomous Systems 9 Systems: Pro-
ceedings of the First European Conference on Artifical Life, edited by Varela and Bourgine.
Copyright ( 1992 by the MIT Press. Reprinted by permission of the MIT Press, Andrew
Assad, and Norman H. Packard.
12. Excerpt from Micromotives and Macrobehavior by Thomas C. Schelling. Copyright (
1978 by W.W. Norton & Company, Inc. Reprinted by permission of W.W. Norton &
Company, Inc. and Thomas C. Schelling.
13. ‘‘Alternative Views of Complexity’’ by Herbert Simon from The Sciences of the Arti-
ficial, third edition. Copyright ( 1996 by the MIT Press. Reprinted by permission of
the MIT Press.
14. ‘‘The Theory of Everything’’ by Robert B. Laughlin and David Pines, from Proceed-
ings of the National Academy of Sciences 97 (2000). Copyright ( 2000 by the National
Academy of Sciences. Reprinted by permission of the National Academy of Sciences
and David Pines.
15. ‘‘Is Anything Ever New? Considering Emergence’’ by James Crutchfield, from Com-
plexity: Metaphors, Models, and Reality, edited by Cowan, Pines, and Meltzer. Copyright
( 1999 by Westview Press. Reprinted by permission of Basic Books, a member of
Perseus Books, LLC and James Crutchfield.
16. ‘‘Design, Observation, Surprise! A Test of Emergence’’ by Edmund M. A. Ronald,
Moshe Sipper, and Mathieu S. Capcarre
`
re from Artificial Life 5 (1999). Copyright (
1999 by the MIT Press. Reprinted by permission of the MIT Press, Edmund M. A.
Ronald, Moshe Sipper, and Mathieu S. Capcarre
`
re.
17. ‘‘Ansatz for Dynamical Hierarchies’’ by Steen Rasmussen, Nils A. Baas, Bernd Mayer,
and Martin Nillson from Artificial Life 7 (2001). Copyright ( 2001 by the MIT Press.
Reprinted by permission of the MIT Press, Steen Rasmussen, Nils A. Baas, Bernd Mayer,

and Martin Nillson.
18. ‘‘Newtonianism, Reductionism, and the Art of Congressional Testimony’’ by
Stephen Weinberg from Nature 330 (1987), edited by Campbell. Copyright ( 1987
xiv Sources
by Nature Publishing Group. Reprinted by permission of Nature Publishing Group and
Stephen Weinberg.
19. Excerpt from Teleology Revisited and Other Essays in the Philosophy and History of
Science by Ernest Nagel. Copyright ( Sidney Nagel and Hackett Publishing Company,
Inc. Reprinted by permission of Hackett Publishing Company, Inc. All rights reserved.
20. ‘‘Chaos’’ by James P. Crutchfield, J. Doyne Farmer, Norman H. Packard, and Robert
S. Shaw, from Scientific American 255 (1986), edited by Rennie. Copyright ( 1986 by
Scientific American. Reprinted by permission of Scientific American, James P. Crutchfield,
J. Doyne Farmer, Norman H. Packard, and Robert S. Shaw.
21. ‘‘Undecidability and Intractability in Theoretical Physics’’ by Stephen Wolfram
from Physical Review Letters 54 (1985), edited by Basbas, Brown, Sandweiss, and Schuh-
mann. Copyright ( 1985 by the American Physical Society. Reprinted by permission
of the American Physical Society and Stephen Wolfram.
22. ‘‘Special Sciences, or the Disunity of Science as a Working Hypotheses’’ by Jerry
Fodor from Synthese 28 (1974), edited by Hendricks, Symons, and van Benthem. Copy-
right ( 1974 by Springer Science and Business Media. Reprinted by permission of
Springer Science and Business Media and Jerry Fodor.
23. Excerpt from ‘‘Supervenience’’ by David J. Chalmers, from The Conscious Mind: In
Search of a Fundamental Theory. Copyright ( 1996 by David J. Chalmers. Reprinted by
permission of Oxford University Press, Inc. and David J. Chalmers.
24. ‘‘The Nonreductivist’s Troubles with Mental Causation’’ by Jaegwon Kim, from
Mental Causation, edited by Heil and Mele. Copyright ( 1993 by Oxford University
Press. Reprinted by permission of Oxford University Press, Inc. and Jaegwon Kim.
Sources xv

Introduction

Emergence relates to phenomena that arise from and depend on some more basic phe-
nomena yet are simultaneously autonomous from that base. The topic of emergence is
fascinating and controversial in part because emergence seems to be widespread and
yet the very idea of emergence seems opaque, and perhaps even incoherent. The topic
has special urgency today because of the burgeoning attention to emergence in con-
temporary philosophy and science.
This book examines how emergence is treated in contemporary philosophy and
science, and one of our goals is to facilitate informed discussions between these com-
munities. Less insular discussions should clarify what the main categories of emergence
are thought to be today, and how well they apply to the paradigm cases considered in
contemporary philosophy and science. We hope that the eventual outcome will be an
understanding of emergence that is both philosophically rigorous and useful in empir-
ical science.
This general introduction to the book gives some examples of apparent emergent
phenomena, calls attention to a few methodological subtleties, and then highlights
some central open questions about emergence that the chapters in this book collec-
tively address. The first section covers contemporary philosophical perspectives on
emergence. Part II covers today’s scientific perspectives on emergence. The last group
of chapters collects contextual and background material from both philosophy and
science. Each section’s introductory essay discusses the chapters’ unifying themes
and issues.
One of the best ways to get a feel for emergence is to consider widely cited core
examples of apparent emergent phenomena. The examples involve a surprising variety
of cases. One group concerns certain properties of physical systems. For example, the
liquidity and transparency of water sometimes are said to emerge from the properties
of oxygen and hydrogen in structured collections of water molecules. As another ex-
ample, if a magnet (specifically a ferromagnet) is heated gradually, it abruptly loses
its magnetism at a specific temperature—the Curie point. This is an example of physi-
cal phase transitions, which often are viewed as key examples of emergence. A third
example involves the shape of a sand pile. As grains of sand are added successively

to the top of the pile, the pile forms a conical shape with a characteristic slope, and
successive small and large avalanches of sand play an important role in preserving
that shape. The characteristic sand pile slope is said to emerge from the interactions
among the grains of sand and gravity.
Life itself is one of the most common sources of examples of apparent emergence.
One simple case is the relationship between a living organism and the molecules that
constitute it at a given moment. In some sense the organism is just those molecules,
but those same molecules would not constitute an organism if they were rearranged
in any of a wide variety of ways, so the living organism seems to emerge from the
molecules. Furthermore, developmental processes of individual organisms are said to
involve the emergence of more mature morphology. A multicellular frog embryo
emerges from a single-celled zygote, a tadpole emerges from this embryo, and eventu-
ally a frog emerges from the tadpole. In addition, evolutionary processes shaping bio-
logical lineages also are said to involve emergence. A complex, highly differentiated
biosphere has emerged over billions of years from what was originally a vastly simpler
and much more uniform array of early life forms. The mind is a rich source of potential
examples of emergence. Our mental lives consist of an autonomous, coherent flow of
mental states (beliefs, desires, memories, fears, hopes, etc.). These, we presume, some-
how emerge out of the swarm of biochemical and electrical activity involving our neu-
rons and central nervous system.
A final group of examples concerns the collective behavior of human agents. The or-
igin and spread of a teenage fad, such as the sudden popularity of a particular hairstyle,
can be represented formally in ways similar to a physical phase transition, and so seem
to involve emergence. Such phenomena often informally are said to exhibit ‘‘tipping
points.’’ Another kind of case is demonstrated in a massive traffic jam spontaneously
emerging from the motions of individual cars controlled by individual human agents
as the density of cars on the highway passes a critical threshold. It is interesting to
speculate about whether the mechanisms behind such phenomena are essentially the
same as those behind certain purely physical phenomena, such as the jamming of
granular media in constricted channels.

The chapters in this book are full of many other examples of apparent emergent phe-
nomena. These examples can serve as useful guides against which to test an account of
emergence. However, testing accounts with these examples is not always simple. Every-
thing else being equal, it would count in favor of a theory of emergence if it could ex-
plain how all these examples do involve emergence. But there is no guarantee that the
best theory will classify all these examples as genuine cases of emergence. When we fi-
nally understand what emergence truly is, we might see that many of the examples are
only apparent cases of emergence. Indeed, one of the hotly contested issues is whether
there are any genuine examples of emergence.
2 Introduction
Identifying the genuine examples of emergence is possible only given an appropriate
definition of emergence, but as the chapters in this book amply illustrate, the proper
characterization of emergence still is contested. Finding appropriate definitions or
theories of emergence with indisputable instances has obvious consequences for the
scientific legitimacy of emergence. One of the most important differences between
contemporary accounts of emergence and their precedents is that the earlier accounts
quickly became metascientific because the examples used to illustrate emergence
tended to be phenomena such as life that at the time were well beyond the realm of
serious scientific understanding. Nowadays, we know much more about complex phe-
nomena like life, so many of the plausible candidates for emergence now are well un-
derstood by science. Any adequate definition of emergence would take these into
account in the sense that at least some of these examples should be included under
the definition in a clear naturalistic fashion. Fashioning such a definition, however,
involves an inescapable back-and-forth process, hinted at above. Definitions and
theories may be sharpened to account for more examples, but also candidate examples
may be abandoned because they fail to fit an otherwise convincing theory. In a similar
way, we must be prepared to abandon some of our preconceptions and background
beliefs about emergence if a persuasive and detailed theory of emergence calls them
into question.
One small caveat is needed here. Hunting for emergence is an exciting sport, but the

claim that something is emergent should be made with care and supported with per-
suasive evidence. Indeed, some of the articles reprinted in this collection ultimately
are quite skeptical about emergence and argue that emergent phenomena, if they exist
at all, are likely to be uncommon. One should not lightly abandon nonemergent,
reductionist approaches that have been successful in many areas of science and philos-
ophy. At the same time, one also should note that many of the conceptions of emer-
gence developed and defended in this book are consistent with many common forms
of reductionism.
The study of emergence is still in its infancy and currently is in a state of consider-
able flux, so a large number of important questions still lack clear answers. Surveying
those questions is one of the best ways to comprehend the nature and scope of the
contemporary philosophical and scientific debate about emergence. Grouped together
here are some of the interconnected questions about emergence that are particularly
pressing, with no pretense that the list is complete.
1. How should emergence be defined? A number of leading ideas appear in different
definitions of emergence, including irreducibility, unpredictability, conceptual nov-
elty, ontological novelty, and supervenience. Some definitions combine a number of
these ideas. We should not presume that only one type of emergence exists and needs
definition. Instead, different kinds of emergence may exist, so different that they fall
under no unified account. Emergent phenomena might well come in fundamentally
Introduction 3
different types that should be distinguished along various dimensions. A further issue
is whether emergence should be defined only relative to a theory, or a level of analysis,
or a system decomposition. The controversy about how to define emergence is exacer-
bated by the casual way that terms such as ‘‘emergence’’ and ‘‘emergent’’ often are
used. At least two separate issues are important here: controversies about the proper
definition of emergence, and controversies about the proper way to test and evaluate
definitions of emergence. Perhaps the proper definition of emergence can be attained
only in the context of a comprehensive theory of emergence, resulting in a definition
that is implicit rather than explicit. Another possibility is that the concept of emer-

gence is best characterized by a cluster of features such as novelty, holism, irreducibil-
ity, and so on, but that the features drawn from the cluster differ from case to case, and
that what counts as novel, for example, differs with different subject matters. Given the
high level of uncertainty about how to properly characterize what emergence is, it
should be no surprise that many other fundamental questions remain unanswered.
2. What ontological categories of entities can be emergent: properties, substances, pro-
cesses, phenomena, patterns, laws, or something else? Within the literature on emer-
gence, different authors say that different categories of entities are emergent. There
should be no presumption that these different categories are mutually exclusive; it
could be that emergence applies to many or even all of them. But it is important to be
clear about which of these candidates is under discussion in any given context. Emer-
gence in one of these categories sometimes entails emergence in another, but that is
not always the case. For example, it seems clear that emergent laws can link nonemer-
gent properties, whereas a genuinely new emergent property would seem to require
new, and probably emergent, laws.
3. What is the scope of actual emergent phenomena? This question partly concerns
which aspects of the world can be characterized as emergent. The examples of apparent
emergence above show the prevalence of the claim that emergence captures something
distinctive about consciousness and about other aspects of the mind. Another com-
mon idea is that emergence is one of the hallmarks of life. But examples of apparent
emergent phenomena also include the behavior of human social organizations and of
nonhuman social organizations. In addition, certain kinds of physical aggregations are
commonly cited as examples of emergent phenomena. The question of the scope of
emergence also concerns the question of how widespread emergence is. For example,
many contemporary philosophers think that emergence is a rare and special quality
found only in extremely distinctive settings, such as human consciousness. Others
think that emergence is quite common and ordinary, applying to a myriad of complex
systems found in nature. For those who think that nothing is truly emergent, the ques-
tion still arises whether this state of affairs is simply an accident or whether the very
idea of emergence is incoherent.

4 Introduction
4. Is emergence an objective feature of the world, or is it merely in the eye of the beholder?
Does emergence characterize only models or descriptions or theories of nature, or does
it apply also to nature itself? Is emergence only a function of how something is
described or viewed or explained? Question 4 is connected to the issue of whether
emergence is defined only relative to a theory or model or representation. Some main-
tain that emergent phenomena are real features of the world, while others maintain
that emergence is merely a result of our imposing certain kinds of representation on
the world, or a result of our limited abilities to comprehend correctly what the world
is like. Candidates for emergent phenomena in the real world include the physical pro-
cess called spontaneous symmetry breaking. A simple case of this can occur when a uni-
form body of liquid has a flat surface. If the bottom of the liquid is heated uniformly
and sufficiently, the fluid breaks up into a field of different convection cells in which
the liquid continually cycles between the bottom and top of the fluid. An example
of emergence that might reflect merely our limited ability to understand the world is
the stable patterns that emerge in John Conway’s Game of Life. If the Game of Life is
initialized with the now-famous R-pentomino pattern of 5 active cells, it takes 1103
iterations of the rules to arrive at a final stable pattern. The discovery of this final pat-
tern occurred only after the game was implemented on a computer; exploring the rules
of the game ‘‘by hand’’ was insufficient.
5. Should emergence be viewed as static and synchronic, or as dynamic and diachronic, or
are both possible? This is a major division between accounts of emergence. In syn-
chronic emergence, the emergent feature is simultaneously present with the basal fea-
tures from which it emerges. By contrast, in diachronic emergence, the base precedes
the emergent phenomenon which develops over time from them. If mental phenomena
emerge from neural phenomena, this is generally thought to be synchronic, there
being no time gap between a recollection of one’s fifteenth birthday and the brain
state that gives rise to the memory. The development of the traffic jam over time is a
good candidate for a diachronically emergent pattern. Discussions in the philosophical
literature usually focus on synchronic emergence, while those in the scientific litera-

ture often concern diachronic emergence. A further question about diachronic emer-
gence is whether and how it applies to both discrete and continuous systems.
6. Does emergence imply or require the existence of new levels of phenomena? A great
many discussions of emergence use the terminology levels, with the levels having
three characteristic features. First, the hierarchy of levels has no precisely defined order,
but instead is determined implicitly by the organizational complexity of objects. These
levels tend to coincide with the domains of individual sciences. Second, each level
is assumed to contain at least one kind of object and one kind of property that is
not found below that level. Third, at each level kinds exist that have novel causal
powers that emerge from the organizational structure of material components. Pressing
Introduction 5
questions thus include whether this framework of levels corresponds to an objective
hierarchy in the world, whether appeal to these levels is useful or misleading, and
whether there are clear criteria to identify the levels.
7. In what ways are emergent phenomena autonomous from their emergent bases? Emer-
gent phenomena are Janus faced; they depend on more basic phenomena and yet
are autonomous from that base. Therefore, if emergence is to be coherent, it must in-
volve different senses of dependence and independence. A number of different kinds of
autonomy have been discussed in the literature, including the ideas that emergent
phenomena are irreducible to their bases, inexplicable from them, unpredictable from
them, supervenient on them, and multiply realizable in them. In addition, emergent
phenomena sometimes are thought to involve the introduction of novel concepts or
properties, and functionally characterized properties sometimes are thought to be espe-
cially associated with emergent phenomena. Another important question about the
autonomy of emergent phenomena is whether that autonomy is merely epistemo-
logical or whether it has ontological consequences. An extreme version of the merely
epistemological interpretation of emergence holds that emergence is simply a sign of
our ignorance. One final issue about the autonomy of emergent phenomena concerns
whether emergence necessarily involves novel causal powers, especially powers that
produce ‘‘downward causation,’’ in which emergent phenomena have novel effects on

their own emergence base. One of the questions in this context is what kind of down-
ward causation is involved, for the coherence of downward causation is debatable.
The chapters in this book provide a variety of perspectives on possible ways to con-
struct answers to these questions. Many of the questions are discussed at greater length
in the introductions to the book’s three sections, where the central themes treated in
the individual chapters are highlighted.
Emergence seems to arise in many of the most interesting complexities in the world
we inhabit, but it is simultaneously palpable and confusing, as the questions above re-
flect. New advances in contemporary philosophy and science, many of which this
book collects, now are converging to enable new progress on these questions, so emer-
gence is a topic ripe for new clarifications, unifications, and other creative conclusions.
This book’s chapters illuminate these questions from many perspectives to help readers
with framing their own answers.
6 Introduction
I Philosophical Perspectives on Emergence