0521830117 cambridge university press paul churchland oct 2005

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Paul Churchland
For over three decades, Paul Churchland has been a provocative and controversial philosopher of mind and philosopher of science. He is most famous as
an advocate of “eliminative materialism,” whereby he suggests that our commonsense understanding of our own minds is radically defective and that the
science of brain demonstrates this (just as an understanding of physics reveals
that our commonsense understanding of a flat and motionless earth is similarly
false). This collection offers an introduction to Churchland’s work, as well as a
critique of some of his most famous philosophical positions. Including contributions by both established and promising young philosophers, it is intended
to complement the growing literature on Churchland, focusing on his contributions in isolation from those of his wife and philosophical partner, Patricia
Churchland, as well as on his contributions to philosophy as distinguished from
those to Cognitive Science.
Brian L. Keeley is an Associate Professor of Philosophy at Pitzer College in
Claremont, California. His research has been supported by the National Science Foundation, the National Institute for Mental Health, the McDonnell
Project for Philosophy and the Neurosciences, and the American Council of
Learned Societies. He has published in the Journal of Philosophy, Philosophical
Psychology, Philosophy of Science, Biology and Philosophy, and Brain and Mind.

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Contemporary Philosophy in Focus
Contemporary Philosophy in Focus offers a series of introductory volumes
to many of the dominant philosophical thinkers of the current age. Each volume consists of newly commissioned essays that cover major contributions of
a preeminent philosopher in a systematic and accessible manner. Comparable
in scope and rationale to the highly successful series Cambridge Companions
to Philosophy, the volumes do not presuppose that readers are already intimately familiar with the details of each philosopher’s work. They thus combine
exposition and critical analysis in a manner that will appeal to students of philosophy and to professionals as well as to students across the humanities and
social sciences.

forthcoming volumes:
Ronald Dworkin edited by Arthur Ripstein
Jerry Fodor edited by Tim Crane
Saul Kripke edited by Alan Berger
David Lewis edited by Theodore Sider and Dean Zimmermann
Bernard Williams edited by Alan Thomas
published volumes:
Stanley Cavell edited by Richard Eldridge
Donald Davidson edited by Kirk Ludwig
Daniel Dennett edited by Andrew Brook and Don Ross
Thomas Kuhn edited by Thomas Nickles
Alasdair MacIntyre edited by Mark Murphy
Hilary Putnam edited by Yemina Ben-Menahem
Richard Rorty edited by Charles Guignon and David Hiley
John Searle edited by Barry Smith
Charles Taylor edited by Ruth Abbey

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Paul Churchland
Edited by

BRIAN L. KEELEY
Pitzer College

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cambridge university press
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo
Cambridge University Press
The Edinburgh Building, Cambridge cb2 2ru, UK

Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521830119
© Cambridge University Press 2006
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.
First published in print format
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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.

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Contents

Preface

page ix

brian l. keeley
Acknowledgments
List of Contributors

1 Introduction: Becoming Paul M. Churchland (1942–)

xiii
xv
1

brian l. keeley
2 Arguing For Eliminativism

32

jos´e luis berm´
udez
3 The Introspectibility of Brain States as Such

66

pete mandik
4 Empiricism and State Space Semantics

88

jesse j. prinz
5 Churchland on Connectionism

113

aarre laakso and garrison w. cottrell
6 Reduction as Cognitive Strategy

154

c. a. hooker
7 The Unexpected Realist

175

william h. krieger and brian l. keeley
8 Two Steps Closer on Consciousness

193

daniel c. dennett
Index

211

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Preface

Philosophy is, among other conceptions no doubt, a human quest for comprehension, particularly self-comprehension. Who am I? How should I
understand the world and myself? It is in this context that the philosophical importance of Paul M. Churchland (PMC) is most evident. For three
decades and counting, PMC has encouraged us to conceive of ourselves
from the “Neurocomputational Perspective” – not only as a minded creature, but also as minded due to our remarkable nervous system. Our brains,
ourselves. This represents a unique and interesting way to approach this
hoary philosophical enquiry.
However, his lasting intellectual contribution as we enter a new millennium is not so much some particular way of seeing ourselves, but rather
his unwavering belief that we are capable of perceiving the world and ourselves in ways very different from the norm. PMC has made a career as
a sort of Patron Saint of Radical Re-conceptualization. Again and again
he argues that we do not have to see ourselves in ordinary and well-worn
terms. Copernicus had us throw out our commonsense framework of a flat,
motionless Earth, wandering planets, and a sphere of fixed stars and showed
us how to see the night sky with new eyes. PMC urges us to consider the
possibility that many more such conceptual revolutions await us, if only we
would give them a fair hearing.
The invocation of Copernicus is fitting. PMC is a philosopher of mind
whose intuitions and ideas are primarily informed by science and the philosophy of science. As he put it in the preface to his 1989 A neurocomputational
perspective: The nature of mind and the structure of science, “The single most
important development in the philosophy of mind during the past forty
years has been the emerging influence of philosophy of science. . . . Since
then it has hardly been possible to do any systematic work in the philosophy of mind, or even to understand the debates, without drawing heavily on
themes, commitments, or antecedent expertise drawn from the philosophy
of science” (xi). Whereas for many, philosophy of psychology (or philosophy of cognitive science) is primarily a branch of philosophy of mind, PMC

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sees it as a branch of philosophy of science; that is, as the exploration into
the unique philosophical problems raised in the context of the scientific
study of the mind/brain.
In the pages of this collection of papers, a number of Paul Churchland’s
contemporaries explore and assess his contributions to a variety of discussions within philosophy. The various authors will discuss his views both
with an eye toward explicating his sometimes counterintuitive (and therefore often provocative) positions and another toward critiquing his ideas.
The result should be a deeper appreciation of his work and his contribution
to the present academic milieu.
In addition to a number of articles over the years, there have been a
small number of book length works and collections on the philosophy of
Paul Churchland (jointly with that of his wife, Patricia). Notable among
these has been McCauley’s 1996 collection, The Churchlands and their critics

(McCauley 1996), which brings together a number of philosophers and scientists to comment critically on various aspects of their philosophy along
with an informative response by the Churchlands. A very accessible, shortbut-book-length exploration is Bill Hirstein’s recent On the Churchlands
(Hirstein 2004). While both of these are recommended to the reader interested in learning more about Churchland’s philosophy, the present volume
attempts to be different from, while at the same time being complementary
to, this existing literature.
As with Hirstein’s volume, the present collection attempts to be accessible to the nonexpert on the neurocomputational perspective. But unlike
it, we do so from the multiple perspectives of the contributors and cover
a wider array of topics. Where Hirstein’s volume has the virtue of a single
author’s unified narrative, the present volume has the virtue of a variety of
perspectives on the philosopher at hand.
The McCauley volume is also a collection of papers by various authors,
but the goal there is explicitly critical; whereas in the present volume, the
critical element is strongly leavened with exegetical ingredients. All the
authors here spend a good amount of space spelling out Churchland’s position before taking issue with it. Also, the explicit target here is to understand
the work of Paul Churchland as a philosopher. Because Churchland works in
the highly interdisciplinary field of Cognitive Science and spends much of
his time engaging neuroscientists of various stripes, it is often useful to consider his contributions to the world as a cognitive scientist. While a laudable
endeavor, that is not the approach taken here. Here we are attempting to
come to grips with Churchland’s contribution to the philosophical realm,
although this should not be taken as devaluing his contributions elsewhere.

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xi

Finally, other secondary literature dealing with the work of Paul
Churchland – including the two volumes discussed previously – often consider his work as of a piece with that of his wife, Patricia Churchland. That
is not the approach here. Instead, we have set our sights on the work of
Paul, although his wife’s work is discussed as is necessary to understand
Paul’s philosophical insights. While their work is clearly interdependent at
a very deep level – often Paul’s work is the yin to Pat’s yang – each is a clear
and cogent thinker in his and her own right. To avoid having it seem that
Pat acts as the mere handmaiden to Paul’s work (or vice versa), we primarily
deal with Paul’s work here.1
Brian L. Keeley, Pitzer College
Note
1. Although see Note 1 of Chapter one for more on the difficulties of separating
the discussion of either philosopher from that of the other.

Works Cited
Churchland, P. M. (1989). A neurocomputational perspective: The nature of mind and
the structure of science. Cambridge, MA, The MIT Press (A Bradford Book).
Hirstein, W. (2004). On the Churchlands. Toronto, Thomson Wadsworth.
McCauley, R. N., Ed. (1996). The Churchlands and their critics. Philosophers and their
critics. Cambridge, MA, Blackwell Publishers Ltd.

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Acknowledgments

Approximately a decade ago, I was sitting in Pat and Paul Churchland’s hot
tub – yes, the rumors are true: West Coast philosophy does occur under
such conditions. I asked Paul to reveal to me the key to a successful career
in philosophy. “Get other people to write about you,” is my memory of

his response. Although this advice might seem as useful as “Buy low; sell
high,” to a graduate student spending his days writing about this or that
philosophical figure, it did convey an important message about how one
needs to think about one’s future scholarship. That out-of-the-classroom
lesson explains in part why I took on the project of editing this book. It
offers me the chance to pay back in a very appropriate way the debt for this
and many other lessons Paul has taught me over the years.
Much of what I learned about Paul’s work came not from him, but
through my contact with Pat Churchland. She was one of the two chairs of
my Ph.D. dissertation committee; and, as a member of her Experimental
Philosophy Lab, and in countless classrooms, office hours, talk receptions,
and so on, I have learned from Pat not only how to be a scholar and philosopher, but quite a lot about how her and Paul’s views have developed over
a long, fruitful career. I would not have had the confidence to undertake a
volume like this if it were not for her influence.
I owe a big debt of gratitude to the contributors to this volume who
hung in there, despite the seemingly slow process.
Bill Bechtel was, as always, an early and indefatigable supporter of my
own work in general, and this volume in particular. Carrie Figdor read over
portions of my contributions and offered valuable feedback.
I should acknowledge the financial support the McDonnell Project in
Philosophy and the Neurosciences, as directed by Kathleen Akins, while I was
working on this collection. The group of scholars she gathered together
for that project resulted in the initial contributors to this volume.
Some of the early work of my Chapter was carried out while I was in
residence as a Fellow of the Center for Philosophy of Science at the University
of Pittsburgh. The members of the Center, along with the faculty, staff,
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Acknowledgments

and students of the History and Philosophy of Science Department there,
deserve my thanks for both a pleasant as well as edifying four months in
Fall 2003. I should thank Sandy Mitchell (not incidentally, the other of the
two chairs of my Ph.D. dissertation) in particular.
Finally, my thanks goes to my friends and colleagues at Pitzer College
for their continuing support of faculty scholarship, specifically in the form
of several awards from the Research & Awards Committee and the granting
of my sabbatical leave in Fall 2003.

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Contributors

jos´e luis bermudez
is Professor of Philosophy and Director of the
´
Philosophy-Neuroscience-Psychology program at Washington University
in St. Louis. He is the author of The Paradox of Self-Consciousness, Thinking
without Words, and Philosophy of Psychology: A Contemporary Introduction.
garrison w. cottrell is Professor of Computer Science and Engineering
at the University of California, San Diego. His main research interest is in
building working models of cognitive processes using neural networks. His
most recent work has been on understanding face and object processing.
His work has been published in Journal of Neuroscience, Nature, Philosophical Psychology, Psychological Science, and the Journal of Cognitive Neuroscience,
among others.
daniel c. dennett is University Professor and Director of the Center
for Cognitive Studies at Tufts University. His most recent awards are the
Barwise Prize, presented by the American Philosophical Association’s Committee on Philosophy and Computers, the Bertrand Russell Society Award
for 2004, and Humanist of the Year, 2004, from the American Humanist Association. He is the author of many books, including most recently,
Freedom Evolves and Sweet Dreams: Philosophical Obstacles to a Science of
Consciousness.
c. a. hooker holds a Chair of Philosophy at the University of Newcastle,
Australia. He is a Fellow of the Australian Academy of Humanities. He
has published eighteen books and more than one hundred research papers,
including Reason, Regulation and Realism: Toward a Naturalistic, Regulatory
Systems Theory of Reason, and A Realistic Theory of Science.

brian l. keeley is Associate Professor of Philosophy at Pitzer College in
Claremont, CA. He is a member of the McDonnell Project in Philosophy and the Neurosciences and has recently been awarded a Charles A.
Ryskamp Fellowship from the American Council of Learned Societies. He

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has published a number of papers, including two in Journal of Philosophy:
“Making Sense of the Senses: Individuating Modalities in Humans and
Other Animals” and “Of Conspiracy Theories.”
william h. krieger is a Lecturer in Philosophy at the California State
Polytechnic University, Pomona. He is the author of a forthcoming book
on philosophical and archaeological explanation: Can There Be a Philosophy
of Archaeology? Processual Archaeology and the Philosophy of Science. He is also
a field director at Tell el-Farah, South Archaeological Excavations.

aarre laakso is a Postdoctoral Fellow in Psychology at Indiana University, Bloomington. His research concerns links between psychology and
philosophy, such as cognitive architectures and the nature of psychological
explanation, spatial representation and reference, and language acquisition
and nativism. His work has appeared in Philosophical Psychology, Psycoloquy,
Metapsychology, and Behavioral and Brain Sciences.
pete mandik is Associate Professor of Philosophy and Coordinator of the
Cognitive Science Laboratory at William Paterson University. He is a member of the McDonnell Project in Philosophy and the Neurosciences. His
work has appeared in Cognition and the Brain: The Philosophy and Neuroscience
Movement and he is an editor of Philosophy and the Neurosciences: A Reader.
jesse j. prinz is Associate Professor of Philosophy at the University of
North Carolina at Chapel Hill. He has research interests in the philosophy
of cognitive science, philosophy of language, and moral psychology. His
books include Furnishing the Mind: Concepts and Their Perceptual Basis, and
Gut Reactions: A Perceptual Theory of Emotion.

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Introduction: Becoming Paul M.

Churchland (1942–)
BRIAN L. KEELEY

The goal of this chapter is two-fold. First, I will present an overview of
the philosophical vision of Paul M. Churchland (PMC). This will help
situate the more detailed, and necessarily narrower, discussions of the other
authors in this volume. Second, the more substantive goal here is to show
that Paul Churchland’s views have not developed in a vacuum. While he has
clearly developed his own unique view of the philosophical terrain, he is not
without his influences – influences that he in no way attempts to hide. His
work is a unique blend of ideas encountered as a nascent philosopher. The
philosophers I will be discussing are not always so well known to today’s
students of philosophy, so there is value in considering how these views of
the preceding generation are being passed on within the work of one of
today’s more influential philosophers of mind and science.
I will begin by sketching Paul Churchland’s personal biography. After
getting the basic facts on the table, I will turn to the three philosophers
whose influence on PMC are my foci: Russell Hanson, Wilfrid Sellars, and
Paul Feyerabend. Each of these thinkers made philosophical contributions
that are reflected in the work of PMC. Next, I will show how all three of
these thinkers contributed to the philosophical position most closely associated with Churchland, namely “Eliminative Materialism.” My comments
critical of Churchland’s version of eliminative materialism are meant to set
the stage for the rest of this volume’s contributions, as this philosophical
framework is at the core of PMC’s view of science, the mind, and the science
of the mind.

PERSONAL HISTORICAL OVERVIEW
PMC was born a Canadian and earned a B.A. from the University of British
Columbia, and in 1969, he was awarded a Ph.D. in Philosophy from the
University of Pittsburgh. There, he wrote a dissertation under the direction

of Wilfrid Sellars. He spent the first 15 years of his career at the University
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of Manitoba, taking advantage of its relative isolation to further develop
his own approach to the ideas to which he was exposed during his graduate
education. In addition to a number of important early papers on eliminative
materialism and the status of commonsense reasoning, he published his first
two books. The first is his still-insightful monograph, Scientific Realism and
the Plasticity of Mind (1979). Here, he lays out his views on the nature of
scientific process and how it is based in the cognitive capacities of adult,
human scientists.
His second book, Matter and Consciousness (1984, revised and updated
1988; translated into five languages), has become one of the most popular textbooks in the philosophy of mind. (Rumor has it that this book is
the all-time bestseller for the Bradford Books imprint of the MIT Press;

quite an impressive achievement given the competition from the likes of
Jerry Fodor, Dan Dennett, Stephen Stich, and Fred Dretske, to name only
a few.) Matter and Consciousness provides an introduction to the Churchland worldview; how the problems of the philosophy of mind are to be
approached from a perspective developed out of the neural sciences. The
book is an important step in PMC’s development because it contains the first
sustained discussions of contemporary neuroscience and how these theories
and discoveries provide grist for the traditional philosophical mill.
Several of PMC’s early papers were co-authored with his perennial partner in crime: his wife, Patricia Smith Churchland. Starting early in their
respective careers, these two have worked closely together; a more-thanthree-decades-long collaboration so close that it is often difficult to determine who is ultimately responsible for this or that idea.1
In 1984, the Churchlands moved to the institution with which they
would become most closely associated: the University of California, San
Diego (UCSD).2 There, he fell in with the then-burgeoning Connectionist (a.k.a. Parallel Distributed Processing (PDP)) movement in cognitive
science. According to the proposals of this group, the mind is best understood as a computational system formed of networks of simple processing
units. The units are modeled on neurons (in that they sum inputs analogously to the behavior of dendrites and either “fire” or not in a process
akin to a paradigmatic neuron’s either producing an action potential down
its axon or not). While other models of the mind made use of languagelike units (say, formal symbols in a “language of thought” (Fodor 1975)),
the PDP approach was intended to present a “sub-symbolic” alternative to
such theories of mind in that the fundamental units are vectors of activation
across networks of neuron-like entities (cf., Smolensky 1988; Clark 1989).
The two-volume bible of this approach came out of the San Diego–based

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PDP Research Group two years later (McClelland and Rumelhart 1986;
Rumelhart and McClelland 1986).
From this point forward, the science of connectionism and what came
to be known more generally as “computational neuroscience” became the
main source of scientific theories and ideas used by Churchland to present
his new theory of mind. His next two major works explore how to apply
the insights resulting from thinking of the mind as a neural net to a variety of problems within philosophy: A Neurocomputational Perspective: The
Nature of Mind and the Structure of Science (1989) and The Engine of Reason,
The Seat of the Soul: A Philosophical Journey into the Brain (1995, translated
into six languages). A collection of papers by Paul and Pat, separately and
together, has also been published (Churchland and Churchland 1998).
As of the writing of this chapter, Paul is still as productive as ever and
continues his career as Professor of Philosophy at UCSD.

INFLUENCES
The question of influences on a thinker is necessarily irresolvable in any
final way. The influence of some – Socrates, Plato, Hume, Kant – are so wide
ranging that there is little value in trying to pick out their specific contributions to any given philosopher. Anyone with a reasonably strong background
in philosophy can see their influences on most who followed them. Two
clear influences on PMC whose ubiquity, even in a very short span of time,
is wide ranging are W. V. O. Quine and Thomas Kuhn. Quine’s promotion of naturalized epistemology opened the way for the highly naturalized
approach that PMC has undertaken.3 Kuhn’s post-positivist exploration of
the dynamics of theory change within science places a strong emphasis on

the psychological processes of individual human scientists. This foreshadows PMC’s own concerns with the scientist as learning machine and the
human learner as a kind of scientist. That said, it seems as though it is practically impossible for philosophers to avoid reading Quine and Kuhn these
days, so spotting these influences is less than earth shattering.
In what follows, I will concentrate on three philosophers – Russell
Hanson, Wilfrid Sellars, and Paul Feyerabend – all of whose work is clearly
reflected in the mature philosophy of Paul Churchland. Furthermore, their
work is sometimes overlooked by recent generations of philosophers,4 such
that, while reading Churchland, it may be unclear what is his unique contribution and what he takes from those upon whose shoulders he stands.
While he is clearly influenced by these thinkers, it is not fair to say that he is

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merely parroting them. With each influence, he accepts some aspects of the
proffered theory and weaves those ideas into a tapestry of his own making.
He clearly rejects some elements as misguided or otherwise wrongheaded.
It is instructive to undertake an investigation into such a personal history

of ideas because it reveals decisions on the part of Churchland as to what
component ideas to embrace and which to leave by the wayside.

HANSON
Norwood Russell Hanson (1924–67) is not so well known today, in part
because he did his most important philosophical work in the years after
the disillusionment with Logical Positivism but before the rise of some
of the more popular post-positivist approaches to philosophy of science,
such as found in the work of Lakatos and Kuhn. Therefore, his oeuvre
gets short shrift. This is a shame because Hanson’s work is an important
stepping-stone from the positivist dreams of Carnap, Ayer, and others to
the contemporary work of philosophers such as PMC.
One belief that Hanson and PMC share is that philosophy of science is
best done with a solid understanding of the practice of science. Large chunks
of Hanson’s work in philosophy of science involve detailed discussion of
the minutia of science and its practice. In the introduction to his landmark
Patterns of Discovery,5 Hanson writes,
The approach and method of this essay is unusual. I have chosen not to
isolate general philosophical issues – the nature of observation, the status of
facts, the logic of causality, and the character of physical theory – and use the
conclusions of such inquiries as lenses through which to view particle theory
[in physics]. Rather the reverse: the inadequacy of philosophical discussions
of these subjects has inclined me to give a different priority. Particle theory
will be the lens through which these perennial philosophical problems will
be viewed. (1958: 2)

As a result of this novel approach, a significant portion of Hanson’s book
contains a fairly detailed discussion of then-current particle microphysics.6
Decades later, it would be PMC’s books that would be filled with the details
of science. The reason for this is not mere “scientism” on the part of Hanson

and Churchland (despite what some critics might believe (Sorell 1991)).
Instead, their reason is that it is in the practice of science – particularly of new
and unsettled disciplines – that one finds the most interesting philosophical

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problems and often the material for their solution. What Hanson wrote of
particle physics in 1958 would be equally true of the neural and cognitive
sciences of the 1980s: “In a growing research discipline, inquiry is directed
not to rearranging old facts and explanations into more elegant formal patterns, but rather to the discovery of new patterns of explanation. Hence
the philosophical flavour of such ideas differs from that presented by science masters, lecturers, and many philosophers of science” (1958: 2). Like
Kuhn, Hanson stressed the importance of studying how science is actually conducted (and not how it is mythologized after the fact). It is in the
practice of actual science that one finds explanatory genesis. For Hanson,
the chosen source was particle physics; for Churchland, it is computational
neuroscience.
So, what image of science did Hanson get from this detailed look

at physics and how did it differ from that of his allegedly misinformed
predecessors? First, Hanson argued that one of the central tenets of Logical Positivism – the distinction between the context of discovery and the
context of justification – was a nonstarter. According to the dogma Hanson
sought to challenge, there are two different aspects to the formation of new
theories. The first aspect, the context of discovery, is the often-mysterious
process of the creation of new hypotheses. How does a scientist generate a new hypothesis? The second, the context of justification, is the more
structured and logical process of determining whether a given hypothesis
is correct. Given a hypothesis, how does a scientist figure out whether it is
correct?
The classic illustrative example of this distinction is Friedrich Kekul´e’s
famous description (years after the event) of how he came to discover the
chemical structure of benzene (Kekul´e 1890/1996). As he describes it, the
idea that the benzene molecule had a ring structure came to him as he was
dozing next to a fire during an evening break from trying to work out a
solution to this structural problem. Having arrived at this proposal, “. . . I
spent the rest of the night working out the consequences of the hypothesis”
(34). Thus, while the creative process through which the hypothesis was
generated seems relatively mysterious (it just came to him while he napped),
that process is distinct from the more rigorous (and fully conscious) process
of working out the logical consequences of the idea in order that it may be
tested.
The work done by this distinction in the positivist story is the demarcation of a division of labor within the study of the scientific method. The
context of discovery, with its apparently irrational intuitive leaps and the

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like, is the purview of psychologists. The logic of the context of justification is not so unconstrained and willy-nilly, and this is where philosophy
of science must necessarily dig in and set the rules. The creative aspect of
discovery is, in essence, rule-breaking whereas the justification process is
essentially rule-driven. Philosophy of science, according to the positivists,
has the goal of determining what those rules should be.
While such a division of labor offers a neat and clean picture of the
scientific process and a clear role for philosophical inquiry, Hanson argued
that it is simply not an accurate portrayal of the scientific process. The
only way one might come to believe it is the correct picture would be
by concentrating too much on such cleaned up “text book” examples as
Kekul´e’s. Instead, when one looks at how science is actually done, it is
revealed that the discovery of explanatory patterns is not only tractable and
interesting, it is perhaps the most interesting part of the scientific method:
“The issue is not theory-using, but theory-finding; my concern is not with
the testing of hypotheses, but with their discovery. Let us examine not how
observation, facts and data are built up into general systems of physical
explanation, but how these systems are built into our observations, and our
appreciation of facts and data” (1958: 3).
The idea that theories are “built into our observations” brings us to
Hanson’s most lasting contribution to philosophy of science: the thesis

that scientific observation is inescapably “theory-laden” (to use the term
he introduces into the philosophical lexicon in Hanson (1958: 19–24); see
also Hanson (1971: 4–8). Positivist dogma held that an essential component of the logic of justification is the claim that the process of observation is independent of our theorizing about the world. After working out
the empirical consequences of a particular hypothesis, we evaluate it by
observing the world and determining whether its predictions obtain. On
the positivist view, in order to be an arbiter of theory evaluation, observation
must, in principle, be independent of theory. Again, the merely psychological (the physiology of perception) is distinct from the philosophical (the
interpretation of observations as evidence either for or against a particular
theory).
Hanson again rejects this simplifying distinction, arguing that observation cannot be so cleanly separated from theory: “The color-blind chemist
needs help from someone with normal vision to complete his titration
work – whether this someone be another chemist, or his six-year-old son,
does not matter. But, now, are there any observations that the latter, the
child, could not make?” (1971: 4). Hanson’s answer is “yes.”

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After citing a passage from Duhem (1914: 218) that foreshadows the
claim he wants to propose, Hanson asks what is presupposed by an act of
genuine scientific observation. The ability to sense is one thing.
Knowledge is also presupposed; scientific observation is thus a ‘theory-laden’
activity. . . . Brainless, photosensitive computers – infants and squirrels
too – do not make scientific observations, however remarkable their signalreception and storage may be. This can be no surprise to any reader of this
book. That the motion of Mars is retrograde, that a fluid’s flow is laminar,
that a plane’s wing-skin friction increases rapidly with descent, that there
is a calcium deficiency in Connecticut soil, that the North American water
table has dropped – these all concern observations which by far exceed
the order of sophistication possible through raw sense experience. Nor are
these cases of simply requiring physicobiological ‘extensions’ to the senses
we already have; for telescopes, microscopes, heat sensors, etc., are not sufficient to determine that Mars’ motion is retrograde, that blood poisoning
is settling in, that volcanic activity is immanent. Being able to make sense
of the sensors requires knowledge and theory – not simply more sense signals. (Understanding the significance of the signal flags fluttering from the
bridge of the Queen Elizabeth does not usually require still more flags to be
flown!) (1971, 5).

This inseparable intermixing of theory and observation is central to
Hanson’s thought. Along with the importance of engaging actual scientific
practice, the theory-ladenness of observation becomes a foundation stone
in PMC’s philosophy as well. We will turn to where PMC parts company
with Hanson later, following a discussion of his affinities with the two other
philosophers considered here.

SELLARS
Wilfrid Sellars (1912–1989), son of philosopher Roy Woodward Sellars
(1880–1973), taught at the University of Minnesota and Yale, before finally
settling at the University of Pittsburgh, where he supervised a doctoral

thesis by Paul Churchland.7
According to Sellars (1960/1963),
The aim of philosophy, abstractly formulated, is to understand how things
in the broadest possible sense of the term hang together in the broadest
possible sense of the term. Under “things in the broadest possible sense” I

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include such radically different items as not only “cabbages and kings”, but
numbers and duties, possibilities and finger snaps, aesthetic experience and
death. To achieve success in philosophy would be, to use a contemporary
turn of phrase, to “know one’s way around” with respect to all these things,
not in that unreflective way in which the centipede of the story knew its way
around before it faced the question, “how do I walk?”, but in that reflective
way which means that no intellectual holds are barred. (1)

This is to say that Sellars sees the academic discipline of Philosophy as not
so much asking the “Big Questions” as asking the “Broad Questions.” It is
that which stitches together all of our various understandings of the world –
those provided by the natural and social sciences, those of the humanities,
as well as those of ordinary humans just grappling with their multifarious
worlds – into a coherent, unified conception of the world. By “unified,” we
should not think of anything akin to a classical reductionist picture in which
every legitimate form of explanation should eventually be translated into
some single language (cf., deVries and Triplett 2000: 114–16). Instead, there
will likely be many different understandings, with philosophy providing
the intellectual resources for understanding how they, as he says, “hang
together.”8
During his long career, Sellars made a number of contributions to philosophy, quite a few of which had an impact on the work of his apprentice.
The first I will note is a key distinction Sellars draws in the ways that
we humans understand ourselves, referred to earlier. Sellars distinguishes
two “images” or very general philosophical frameworks for understanding
human activity. The first is the manifest image – the embodiment of our
commonsense understanding of human behavior, including our own personal behavior. Sellars (1960/1963) characterizes “. . . the manifest image of
man-in-the-world as the framework in terms of which man encountered
himself – which is, of course, when he came to be man” (6). This image
is not pre-theoretical in the sense of being unreflective. Rather this is the
image of oneself achieved upon taking oneself as an object of understanding;
what humans got when they first realized that they, too, were something
that required understanding, in addition to all the other confusing aspects
of the world, including other animals, the weather, the night sky, etc.9 Furthermore, it is a framework in which the basic ontological category is that
of “persons.” In the manifest image, everything understood is understood
in terms of being a kind of person. As deVries and Triplett (2000) put it, “It
is our refined commonsense conception of what the world and ourselves
are and how they interact” (190).

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The manifest image is contrasted with what Sellars calls the scientific
image. This is the image of our self and the world provided by the explicit
theorizing of post-Enlightenment science. There is a strong “what-yousee-is-what-you-get” element in Sellars’ conception of the manifest image.
He cites Mill’s inductive method as central to the method of the manifest
image; such explanation is generated by noting the correlations of observed
events in the world (1960/1963: 7). In contrast, what demarcates the method
of the scientific image is its method of hypothesis and the postulation of
the unobserved and the unobservable in the service of explanation. The
fundamental ontology of the manifest image (persons) is directly observable
to everyone; indeed if all one had was the manifest image, persons are all
one would ever see. By contrast, the fundamental ontology of the scientific
image, say that provided by contemporary physics, is one of unobservable
atomic elements, atomic forces, and the like.10
What is the relationship between these two images? They are often

taken to be opposed to one another. As one striking example, one line of
thought derives from taking the scientific perspective on humans themselves and seeing them not as persons in the sense of the manifest image
but rather as a collection of abstract, scientific entities (cell assemblies,
molecules, expressed DNA, quarks, what have you): “Even persons, it is
said (mistakenly, I believe), are being ‘depersonalized’ by the advance of the
scientific point of view” (Sellars 1960/1963: 10). This is “mistaken” because
he takes the goal of philosophy to be explanation in the broadest sense; he
sees both images as essential to a full understanding of humans, the world,
and the place of humans in the world. He likens the relationship between
the two to be that of the different component images of a stereoscopic diagram. Properly viewed through a pair of stereoscopic lenses, the two images
combine to provide an image with dimensions lacking in either component
image on its own.11
Sellars’ notion of these two different images of ourselves and the world
around us show up in PMC’s career-long concern with what have come
to be known as “folk theories.” Folk theories are what they sound like: the
commonsense theories possessed by the average person. In particular, PMC
is concerned with folk psychology, our commonsense theory of animal (most
important, human) thought and behavior.12 While PMC accepts Sellars’
distinction between the two images, how he treats the relationship between
these two images represents perhaps his largest break from his dissertation
advisor, but that will addressed in the following section.
Another contribution Sellars made to contemporary philosophy –
the contribution he is likely best known for today – is his attack on

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