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Philosophy
-- Robert A. Wilson
- Three classic philosophical issues about the
mind
- From materialism to mental science
- A detour before the naturalistic term
- The philosophy of science
- The mind in cognitive science
- A focus on folk psychology
- Exploring mental content
- Logic and the sciences of the mind
- Two ways to get biological
The areas of philosophy that contribute to and
draw on the cognitive sciences are various; they include the
philosophy of mind, science, and language; formal and philosophical
logic; and traditional metaphysics and epistemology. The most
direct connections hold between the philosophy of mind and the
cognitive sciences, and it is with classical issues in the
philosophy of mind that I begin this introduction (section 1).
I then briefly chart the move from the rise of materialism as the
dominant response to one of these classic issues, the mind-body
problem, to the idea of a science of the mind. I do so by
discussing the early attempts by introspectionists and behaviorists
to study the mind (section 2). Here I focus on several problems
with a philosophical flavor that arise for these views, problems
that continue to lurk backstage in the theater of contemporary
cognitive science.
Between these early attempts at a science of the mind and
today's efforts lie two general, influential philosophical
traditions, ordinary language philosophy and logical positivism. In
order to bring out, by contrast, what is distinctive about the
contemporary naturalism integral to philosophical contributions to
the cognitive sciences, I sketch the approach to the mind in these
traditions (section 3). And before getting to contemporary
naturalism itself I take a quick look at the philosophy of science,
in light of the legacy of positivism (section 4).
In sections 5 through 7 I get, at last, to the mind in cognitive
science proper. Section 5 discusses the conceptions of mind that
have dominated the contemporary cognitive sciences, particularly
that which forms part of what is sometimes called "classic"
cognitive science and that of its connectionist rival. Sections 6
and 7 explore two specific clusters of topics that have been the
focus of philosophical discussion of the mind over the last 20
years or so, folk psychology and mental content. The final sections
gesture briefly at the interplay between the cognitive sciences and
logic (section 8) and biology (section 9).
i. The Mental-Physical Relation
The relation between the mental and the physical
is the deepest and most recurrent classic philosophical topic in
the philosophy of mind, one very much alive today. In due course,
we will come to see why this topic is so persistent and pervasive
in thinking about the mind. But to convey something of the topic's
historical significance let us begin with a classic expression of
the puzzling nature of the relation between the mental and the
physical, the MIND-BODY PROBLEM.
This problem is most famously associated with RENÉ DESCARTES, the preeminent
figure of philosophy and science in the first half of the
seventeenth century. Descartes combined a thorough-going
mechanistic theory of nature with a dualistic theory of
the nature of human beings that is still, in general terms, the
most widespread view held by ordinary people outside the hallowed
halls of academia. Although nature, including that of the human
body, is material and thus completely governed by basic principles
of mechanics, human beings are special in that they are composed
both of material and nonmaterial or mental stuff, and so are not so
governed. In Descartes's own terms, people are essentially a
combination of mental substances (minds) and material substances
(bodies). This is Descartes's dualism. To put it in more
commonsense terms, people have both a mind and a body.
Although dualism is often presented as a possible solution to
the mind-body problem, a possible position that one might adopt in
explaining how the mental and physical are related, it serves
better as a way to bring out why there is a "problem" here at all.
For if the mind is one type of thing, and the body is another, how
do these two types of things interact? To put it differently, if
the mind really is a nonmaterial substance, lacking physical
properties such as spatial location and shape, how can it be both
the cause of effects in the material world -- like making bodies
move -- and itself be causally affected by that world -- as when a
thumb slammed with a hammer (bodily cause) causes one to feel pain
(mental effect)? This problem of causation between mind and body
has been thought to pose a largely unanswered problem for Cartesian
dualism.
It would be a mistake, however, to assume that the mind-body
problem in its most general form is simply a consequence of
dualism. For the general question as to how the mental is related
to the physical arises squarely for those convinced that some
version of materialism or PHYSICALISM must
be true of the mind. In fact, in the next section, I will suggest
that one reason for the resilience and relevance of the mind-body
problem has been the rise of materialism over the last
fifty years.
Materialists hold that all that exists is material or physical
in nature. Minds, then, are somehow or other composed of
arrangements of physical stuff. There have been various ways in
which the "somehow or other" has been cashed out by physicalists,
but even the view that has come closest to being a consensus view
among contemporary materialists -- that the mind
supervenes on the body -- remains problematic. Even once
one adopts materialism, the task of articulating the relationship
between the mental and the physical remains, because even physical
minds have special properties, like intentionality and
consciousness, that require further explanation. Simply proclaiming
that the mind is not made out of distinctly mental substance, but
is material like the rest of the world, does little to explain the
features of the mind that seem to be distinctively if not uniquely
features of physical minds.
ii. The Structure of the Mind and Knowledge
Another historically important cluster of topics
in the philosophy of mind concerns what is in a mind. What, if
anything, is distinctive of the mind, and how is the mind
structured? Here I focus on two dimensions to this issue.
One dimension stems from the RATIONALISM
VS. EMPIRICISM debate that reached a high point in the
seventeenth and eighteenth centuries. Rationalism and empiricism
are views of the nature of human knowledge. Broadly speaking,
empiricists hold that all of our knowledge derives from our
sensory, experiential, or empirical interaction with the world.
Rationalists, by contrast, hold the negation of this, that there is
some knowledge that does not derive from experience.
Since at least our paradigms of knowledge -- of our immediate
environments, of common physical objects, of scientific kinds --
seem obviously to be based on sense experience, empiricism has
significant intuitive appeal. Rationalism, by contrast, seems to
require further motivation: minimally, a list of knowables that
represent a prima facie challenge to the empiricist's global claim
about the foundations of knowledge. Classic rationalists, such as
Descartes, Leibniz, Spinoza, and perhaps more contentiously KANT, included knowledge of God, substance,
and abstract ideas (such as that of a triangle, as opposed to ideas
of particular triangles). Empiricists over the last three hundred
years or so have either claimed that there was nothing to know in
such cases, or sought to provide the corresponding empiricist
account of how we could know such things from experience.
The different views of the sources of knowledge held by
rationalists and empiricists have been accompanied by
correspondingly different views of the mind, and it is not hard to
see why. If one is an empiricist and so holds, roughly, that there
is nothing in the mind that is not first in the senses, then there
is a fairly literal sense in which ideas, found in the
mind, are complexes that derive from impressions in the
senses. This in turn suggests that the processes that constitute
cognition are themselves elaborations of those that constitute
perception, that is, that cognition and perception differ only in
degree, not kind. The most commonly postulated mechanisms governing
these processes are association and similarity,
from Hume's laws of association to feature-extraction in
contemporary connectionist networks. Thus, the mind tends to be
viewed by empiricists as a domain-general device, in that
the principles that govern its operation are constant across
various types and levels of cognition, with the common empirical
basis for all knowledge providing the basis for parsimony here.
By contrast, in denying that all knowledge derives from the
senses, rationalists are faced with the question of what other
sources there are for knowledge. The most natural candidate is the
mind itself, and for this reason rationalism goes hand in hand with
NATIVISM about both the source of human
knowledge and the structure of the human mind. If some ideas are
innate (and so do not need to be derived from experience), then it
follows that the mind already has a relatively rich, inherent
structure, one that in turn limits the malleability of the mind in
light of experience. As mentioned, classic rationalists made the
claim that certain ideas or CONCEPTS
were innate, a claim occasionally made by contemporary nativists --
most notably Jerry Fodor (1975) in his claim that all
concepts are innate. However, contemporary nativism is more often
expressed as the view that certain implicit knowledge that we have
or principles that govern how the mind works -- most notoriously,
linguistic knowledge and principles -- are innate, and so not
learned. And because the types of knowledge that one can have may
be endlessly heterogeneous, rationalists tend to view the mind as a
domain-specific device, as one made up of systems whose
governing principles are very different. It should thus be no
surprise that the historical debate between rationalists and
empiricists has been revisited in contemporary discussions of the
INNATENESS OF LANGUAGE, the MODULARITY OF MIND, and CONNECTIONISM.
A second dimension to the issue of the structure of the mind
concerns the place of CONSCIOUSNESS among
mental phenomena. From WILLIAM JAMES's
influential analysis of the phenomenology of the stream of
consciousness in his The Principles of Psychology (1890)
to the renaissance that consciousness has experienced in the last
ten years (if publication frenzies are anything to go by),
consciousness has been thought to be the most puzzling of mental
phenomena. There is now almost universal agreement that conscious
mental states are a part of the mind. But how large and how
important a part? Consciousness has sometimes been thought to
exhaust the mental, a view often attributed to Descartes. The idea
here is that everything mental is, in some sense, conscious or
available to consciousness. (A version of the latter of these ideas
has been recently expressed in John Searle's [1992: 156]
connection principle: "all unconscious intentional states
are in principle accessible to consciousness.")
There are two challenges to the view that everything mental is
conscious or even available to consciousness. The first is posed by
the unconscious. SIGMUND
FREUD's extension of our common-sense attributions of belief
and desire, our folk psychology, to the realm of the unconscious
played and continues to play a central role in PSYCHOANALYSIS. The second arises from the
conception of cognition as information processing that has been and
remains focal in contemporary cognitive science, because such
information processing is mostly not available to
consciousness. If cognition so conceived is mental, then most
mental processing is not available to consciousness.
iii. The First- and Third-Person Perspectives
Occupying center stage with the mind-body problem
in traditional philosophy of mind is the problem of other
minds, a problem that, unlike the mind-body problem, has all
but disappeared from philosophical contributions to the cognitive
sciences. The problem is often stated in terms of a contrast
between the relatively secure way in which I "directly" know about
the existence of my own mental states, and the far more
epistemically risky way in which I must infer the existence of the
mental states of others. Thus, although I can know about my own
mental states simply by introspection and self-directed reflection,
because this way of finding out about mental states is peculiarly
first-person, I need some other type of evidence to draw
conclusions about the mental states of others. Naturally, an
agent's behavior is a guide to what mental states he or she is in,
but there seems to be an epistemic gap between this sort of
evidence and the attribution of the corresponding mental states
that does not exist in the case of self-ascription. Thus the
problem of other minds is chiefly an epistemological
problem, sometimes expressed as a form of skepticism about the
justification that we have for attributing mental states to
others.
There are two reasons for the waning attention to the problem of
other minds qua problem that derive from recent
philosophical thought sensitive to empirical work in the cognitive
sciences. First, research on introspection and SELF-KNOWLEDGE has raised questions
about how "direct" our knowledge of our own mental states and of
the SELF is, and so called into question
traditional conceptions of first-person knowledge of mentality.
Second, explorations of the THEORY OF
MIND, ANIMAL COMMUNICATION, and SOCIAL PLAY BEHAVIOR have begun to examine
and assess the sorts of attribution of mental states that are
actually justified in empirical studies, suggesting that
third-person knowledge of mental states is not as limited as has
been thought. Considered together, this research hints that the
contrast between first- and third-person knowledge of the mental is
not as stark as the problem of other minds seems to intimate.
Still, there is something distinctive about the first-person
perspective, and it is in part as an acknowledgment of this, to
return to an earlier point, that consciousness has become a hot
topic in the cognitive sciences of the 1990s. For whatever else we
say about consciousness, it seems tied ineliminably to the
first-person perspective. It is a state or condition that has an
irreducibly subjective component, something with an
essence to be experienced, and which presupposes the existence of a
subject of that experience. Whether this implies that there are QUALIA that resist complete characterization
in materialist terms, or other limitations to a science of the
mind, remain questions of debate.
See also
In raising issue i., the mental-physical
relation, in the previous section, I implied that materialism was
the dominant ontological view of the mind in contemporary
philosophy of mind. I also suggested that, if anything, general
convergence on this issue has intensified interest in the mind-body
problem. For example, consider the large and lively debate over
whether contemporary forms of materialism are compatible with
genuine MENTAL CAUSATION, or,
alternatively, whether they commit one to EPIPHENOMENALISM about the mental (Kim
1993; Heil and Mele 1993; Yablo 1992). Likewise, consider the fact
that despite the dominance of materialism, some philosophers
maintain that there remains an EXPLANATORY
GAP between mental phenomena such as consciousness and any
physical story that we are likely to get about the workings of the
brain (Levine 1983; cf. Chalmers 1996). Both of these issues, very
much alive in contemporary philosophy of mind and cognitive
science, concern the mind-body problem, even if they are not always
identified in such old-fashioned terms.
I also noted that a healthy interest in the first-person
perspective persists within this general materialist framework. By
taking a quick look at the two major initial attempts to develop a
systematic, scientific understanding of the mind -- late
nineteenth-century introspectionism and early twentieth-century
behaviorism -- I want to elaborate on these two points and bring
them together.
Introspectionism was widely held to fall prey to a problem known
as the problem of the homunculus. Here I argue that
behaviorism, too, is subject to a variation on this very problem,
and that both versions of this problem continue to nag at
contemporary sciences of the mind.
Students of the history of psychology are familiar with the
claim that the roots of contemporary psychology can be dated from
1879, with the founding of the first experimental laboratory
devoted to psychology by WILHELM WUNDT in
Leipzig, Germany. As an experimental laboratory, Wundt's
laboratory relied on the techniques introduced and refined in
physiology and psychophysics over the preceding fifty years by HELMHOLTZ, Weber, and Fechner that paid
particular attention to the report of SENSATIONS. What distinguished Wundt's as a
laboratory of psychology was his focus on the data
reported in consciousness via the first-person perspective;
psychology was to be the science of immediate experience and its
most basic constituents. Yet we should remind ourselves of how
restricted this conception of psychology was, particularly relative
to contemporary views of the subject.
First, Wundt distinguished between mere INTROSPECTION, first-person reports of
the sort that could arise in the everyday course of events, and
experimentally manipulable self-observation of the sort that could
only be triggered in an experimental context. Although Wundt is
often thought of as the founder of an introspectionist methodology
that led to a promiscuous psychological ontology, in disallowing
mere introspection as an appropriate method for a science of the
mind he shared at least the sort of restrictive conception of
psychology with both his physiological predecessors and
his later behaviorist critics.
Second, Wundt thought that the vast majority of ordinary thought
and cognition was not amenable to acceptable first-person
analysis, and so lay beyond the reach of a scientific psychology.
Wundt thought, for example, that belief, language, personality, and
SOCIAL COGNITION could be studied
systematically only by detailing the cultural mores, art, and
religion of whole societies (hence his four-volume
Völkerpsychologie of 1900-1909). These studies
belonged to the humanities (Geisteswissenshaften) rather
than the experimental sciences (Naturwissenschaften), and
were undertaken by anthropologists inspired by Wundt, such as BRONISLAW MALINOWSKI.
Wundt himself took one of his early contributions to be a
solution of the mind-body problem, for that is what the data
derived from the application of the experimental method to
distinctly psychological phenomena gave one: correlations between
the mental and the physical that indicated how the two were
systematically related. The discovery of psychophysical laws of
this sort showed how the mental was related to the physical. Yet
with the expansion of the domain of the mental amenable to
experimental investigation over the last 150 years, the mind-body
problem has taken on a more acute form: just how do we get all that
mind-dust from merely material mechanics? And it is here that the
problem of the homunculus arises for introspectionist psychology
after Wundt.
The problem, put in modern guise, is this. Suppose that one
introspects, say, in order to determine the location of a certain
feature (a cabin, for example) on a map that one has attempted to
memorize (Kosslyn 1980). Such introspection is typically reported
in terms of exploring a mental image with one's mind's
eye. Yet we hardly want our psychological story to end there,
because it posits a process (introspection) and a processor (the
mind's eye) that themselves cry out for further explanation. The
problem of the homunculus is the problem of leaving undischarged
homunculi ("little men" or their equivalents) in one's
explanantia, and it persists as we consider an elaboration
on our initial introspective report. For example, one might well
report forming a mental image of the map, and then scanning around
the various features of the map, zooming in on them to discern more
clearly what they are to see if any of them is the sought-after
cabin. To take this introspective report seriously as a guide to
the underlying psychological mechanisms would be to posit,
minimally, an imager (to form the initial image), a
scanner (to guide your mind's eye around the image), and a
zoomer (to adjust the relative sizes of the features on
the map). But here again we face the problem of the homunculus,
because such "mechanisms" themselves require further psychological
decomposition.
To be faced with the problem of the homunculus, of course, is
not the same as to succumb to it. We might distinguish two
understandings of just what the "problem" is here. First, the
problem of the homunculus could be viewed as a problem specifically
for introspectionist views of psychology, a problem that was never
successfully met and that was principally responsible for the
abandonment of introspectionism. As such, the problem motivated BEHAVIORISM in psychology. Second, the
problem of the homunculus might simply be thought of as a challenge
that any view that posits internal mental states must
respond to: to show how to discharge all of the homunculi
introduced in a way that is acceptably materialistic. So construed,
the problem remains one that has been with us more recently, in
disputes over the psychological reality of various forms of GENERATIVE GRAMMAR (e.g., Stabler 1983); in
the nativism that has been extremely influential in post-Piagetian
accounts of COGNITIVE DEVELOPMENT
(Spelke 1990; cf. Elman et al. 1996); and in debates over the
significance of MENTAL ROTATION and the
nature of IMAGERY (Kosslyn 1994; cf.
Pylyshyn 1984: ch.8).
With Wundt's own restrictive conception of psychology and the
problem of the homunculus in mind, it is with some irony that we
can view the rise and fall of behaviorism as the dominant paradigm
for psychology subsequent to the introspectionism that Wundt
founded. For here was a view so deeply indebted to materialism and
the imperative to explore psychological claims only by reference to
what was acceptably experimental that, in effect, in its purest
form it appeared to do away with the distinctively mental
altogether! That is, because objectively observable behavioral
responses to objectively measurable stimuli are all that could be
rigorously explored, experimental psychological investigations
would need to be significantly curtailed, relative to those of
introspectionists such as Wundt and Titchener. As J. B. Watson said
in his early, influential "Psychology as the Behaviorist Views It"
in 1913, "Psychology as behavior will, after all, have to neglect
but few of the really essential problems with which psychology as
an introspective science now concerns itself. In all probability
even this residue of problems may be phrased in such a way that
refined methods in behavior (which certainly must come) will lead
to their solution" (p. 177).
Behaviorism brought with it not simply a global conception of
psychology but specific methodologies, such as CONDITIONING, and a focus on phenomena,
such as that of LEARNING, that have
been explored in depth since the rise of behaviorism. Rather than
concentrate on these sorts of contribution to the interdisciplinary
sciences of the mind that behaviorists have made, I want to focus
on the central problem that faced behaviorism as a research program
for reshaping psychology.
One of the common points shared by behaviorists in their
philosophical and psychological guises was a commitment to an
operational view of psychological concepts and thus a
suspicion of any reliance on concepts that could not be
operationally characterized. Construed as a view of scientific
definition (as it was by philosophers), operationalism is
the view that scientific terms must be defined in terms of
observable and measurable operations that one can perform. Thus, an
operational definition of "length," as applied to ordinary objects,
might be: "the measure we obtain by laying a standard measuring rod
or rods along the body of the object." Construed as a view of
scientific methodology (as it was by psychologists),
operationalism claims that the subject matter of the sciences
should be objectively observable and measurable, by itself a view
without much content.
The real bite of the insistence on operational definitions and
methodology for psychology came via the application of
operationalism to unobservables, for the various feelings,
sensations, and other internal states reported by introspection,
themselves unobservable, proved difficult to operationalize
adequately. Notoriously, the introspective reports from various
psychological laboratories produced different listings of the basic
feelings and sensations that made up consciousness, and the lack of
agreement here generated skepticism about the reliability of
introspection as a method for revealing the structure of the mind.
In psychology, this led to a focus on behavior, rather than
consciousness, and to its exploration through observable stimulus
and response: hence, behaviorism. But I want to suggest that this
reliance on operationalism itself created a version of the problem
of the homunculus for behaviorism. This point can be made in two
ways, each of which offers a reinterpretation of a standard
criticism of behaviorism. The first of these criticisms is usually
called "philosophical behaviorism," the attempt to provide
conceptual analyses of mental state terms exclusively in terms of
behavior; the second is "psychological behaviorism," the research
program of studying objective and observable behavior, rather than
subjective and unobservable inner mental episodes.
First, as Geach (1957: chap. 4) pointed out with respect to
belief, behaviorist analyses of individual folk psychological
states are bound to fail, because it is only in concert with many
other propositional attitudes that any given such attitude has
behavioral effects. Thus, to take a simple example, we might
characterize the belief that it is raining as the tendency to utter
"yes" when asked, "Do you believe that it is raining?" But one
reason this would be inadequate is that one will engage in this
verbal behavior only if one wants to answer truthfully,
and only if one hears and understands the
question asked, where each of the italicized terms above refers to
some other mental state. Because the problem recurs in
every putative analysis, this implies that a
behavioristically acceptable construal of folk psychology is not
possible. This point would seem to generalize beyond folk
psychology to representational psychology more generally.
So, in explicitly attempting to do without internal mental
representations, behaviorists themselves are left with mental
states that must simply be assumed. Here we are not far from those
undischarged homunculi that were the bane of introspectionists,
especially once we recognize that the metaphorical talk of
"homunculi" refers precisely to internal mental states and
processes that themselves are not further explained.
Second, as Chomsky (1959: esp. p. 54) emphasized in his review
of Skinner's Verbal Behavior, systematic attempts to
operationalize psychological language invariably smuggle in a
reference to the very mental processes they are trying to do
without. At the most general level, the behavior of interest to the
linguist, Skinner's "verbal behavior," is difficult to characterize
adequately without at least an implicit reference to the sorts of
psychological mechanism that generate it. For example, linguists
are not interested in mere noises that have the same physical
properties -- "harbor" may be pronounced so that its first syllable
has the same acoustic properties as an exasperated grunt -- but in
parts of speech that are taxonomized at least partially in terms of
the surrounding mental economy of the speaker or listener.
The same seems true for all of the processes introduced
by behaviorists -- for example, stimulus control, reinforcement,
conditioning -- insofar as they are used to characterize complex,
human behavior that has a natural psychological description (making
a decision, reasoning, conducting a conversation, issuing a
threat). What marks off their instances as behaviors of the
same kind is not exclusively their physical or behavioral
similarity, but, in part, the common, internal psychological
processes that generate them, and that they in turn generate.
Hence, the irony: behaviorists, themselves motivated by the idea of
reforming psychology so as to generalize about objective,
observable behavior and so avoid the problem of the homunculus, are
faced with undischarged homunculi, that is, irreducibly mental
processes, in their very own alternative to introspectionism.
The two versions of the problem of the homunculus are still with
us as a Scylla and Charybdis for contemporary cognitive scientists
to steer between. On the one hand, theorists need to avoid building
the very cognitive abilities that they wish to explain into the
models and theories they construct. On the other, in attempting to
side-step this problem they also run the risk of masking the ways
in which their "objective" taxonomic categories presuppose further
internal psychological description of precisely the sort that gives
rise to the problem of the homunculus in the first place.
See also
Given the state of philosophy and psychology in
the early 1950s, it is surprising that within twenty-five years
there would be a thriving and well-focused interdisciplinary unit
of study, cognitive science, to which the two are central. As we
have seen, psychology was dominated by behaviorist approaches that
were largely skeptical of positing internal mental states as part
of a serious, scientific psychology. And Anglo-American philosophy
featured two distinct trends, each of which made philosophy more
insular with respect to other disciplines, and each of which served
to reinforce the behaviorist orientation of psychology.
First, ordinary language philosophy, particularly in Great
Britain under the influence of Ludwig Wittgenstein and J. L.
Austin, demarcated distinctly philosophical problems as soluble (or
dissoluble) chiefly by reference to what one would ordinarily say,
and tended to see philosophical views of the past and present as
the result of confusions in how philosophers and others come to use
words that generally have a clear sense in their ordinary contexts.
This approach to philosophical issues in the post-war period has
recently been referred to by Marjorie Grene (1995: 55) as the
"Bertie Wooster season in philosophy," a characterization I suspect
would seem apt to many philosophers of mind interested in
contemporary cognitive science (and in P. G. Wodehouse). Let me
illustrate how this approach to philosophy served to isolate the
philosophy of mind from the sciences of the mind with perhaps the
two most influential examples pertaining to the mind in the
ordinary language tradition.
In The Concept of Mind, Gilbert Ryle (1949: 17)
attacked a view of the mind that he referred to as "Descartes'
Myth" and "the dogma of the Ghost in the Machine" -- basically,
dualism -- largely through a repeated application of the objection
that dualism consisted of an extended category mistake: it
"represents the facts of mental life as if they belonged to one
logical type or category … when they actually belong to
another." Descartes' Myth represented a category mistake because in
supposing that there was a special, inner theater on which mental
life is played out, it treated the "facts of mental life" as
belonging to a special category of facts, when they were simply
facts about how people can, do, and would behave in certain
circumstances. Ryle set about showing that for the range of mental
concepts that were held to refer to private, internal mental
episodes or events according to Descartes' Myth -- intelligence,
the will, emotion, self-knowledge, sensation, and imagination -- an
appeal to what one would ordinarily say both shows the dogma of the
Ghost in the Machine to be false, and points to a positive account
of the mind that was behaviorist in orientation. To convey why
Ryle's influential views here turned philosophy of mind away from
science rather than towards it, consider the opening sentences of
The Concept of Mind: "This book offers what may with
reservations be described as a theory of the mind. But it does not
give new information about minds. We possess already a wealth of
information about minds, information which is neither derived from,
nor upset by, the arguments of philosophers. The philosophical
arguments which constitute this book are intended not to increase
what we know about minds, but to rectify the logical geography of
the knowledge which we already possess" (Ryle 1949: 9). The "we"
here refers to ordinary folk, and the philosopher's task in
articulating a theory of mind is to draw on what we already know
about the mind, rather than on arcane, philosophical views or on
specialized, scientific knowledge.
The second example is Norman Malcolm's Dreaming, which,
like The Concept of Mind, framed the critique it wished to
deliver as an attack on a Cartesian view of the mind. Malcolm's
(1959: 4) target was the view that "dreams are the activity of the
mind during sleep," and associated talk of DREAMING as involving various mental acts,
such as remembering, imagining, judging, thinking, and reasoning.
Malcolm argued that such dream-talk, whether it be part of
commonsense reflection on dreaming (How long do dreams last?; Can
you work out problems in your dreams?) or a contribution to more
systematic empirical research on dreaming, was a confusion arising
from the failure to attend to the proper "logic" of our ordinary
talk about dreaming. Malcolm's argument proceeded by appealing to
how one would use various expressions and sentences that
contained the word "dreaming." (In looking back at Malcolm's book,
it is striking that nearly every one of the eighteen short chapters
begins with a paragraph about words and what one would say with or
about them.)
Malcolm's central point was that there was no way to
verify any given claim about such mental activity
occurring while one was asleep, because the commonsense criteria
for the application of such concepts were incompatible with saying
that a person was asleep or dreaming. And because there was no way
to tell whether various attributions of mental states to a sleeping
person were correct, such attributions were meaningless. These
claims not only could be made without an appeal to any empirical
details about dreaming or SLEEP, but
implied that the whole enterprise of investigating dreaming
empirically itself represented some sort of logical
muddle.
Malcolm's point became more general than one simply about
dreaming (or the word "dreaming"). As he said in a preface to a
later work, written after "the notion that thoughts, ideas,
memories, sensations, and so on 'code into' or 'map onto' neural
firing patterns in the brain" had become commonplace: "I believe
that a study of our psychological concepts can show that [such]
psycho-physical isomorphism is not a coherent assumption" (Malcolm
1971: x). Like Ryle's straightening of the logical geography of our
knowledge of minds, Malcolm's appeal to the study of our
psychological concepts could be conducted without any knowledge
gleaned from psychological science (cf. Griffiths 1997: chap. 2 on
the emotions).
Quite distinct from the ordinary language tradition was a second
general perspective that served to make philosophical contributions
to the study of the mind "distinctive" from those of science. This
was logical positivism or empiricism, which developed in Europe in
the 1920s and flourished in the United States through the 1930s and
1940s with the immigration to the United States of many of its
leading members, including Rudolph Carnap, Hans Reichenbach,
Herbert Feigl, and Carl Hempel. The logical empiricists were called
"empiricists" because they held that it was via the senses and
observation that we came to know about the world, deploying this
empiricism with the logical techniques that had been developed by
Gottlob Frege, Bertrand Russell, and Alfred Whitehead. Like
empiricists in general, the logical positivists viewed the sciences
as the paradigmatic repository of knowledge, and they were largely
responsible for the rise of philosophy of science as a distinct
subdiscipline within philosophy.
As part of their reflection on science they articulated and
defended the doctrine of the UNITY OF
SCIENCE, the idea that the sciences are, in some sense,
essentially unified, and their empiricism led them to appeal to PARSIMONY AND SIMPLICITY as grounds for
both theory choice within science and for preferring theories that
were ontological Scrooges. This empiricism came with a focus on
what could be verified, and with it scepticism about
traditional metaphysical notions, such as God, CAUSATION, and essences, whose instances
could not be verified by an appeal to the data of sense experience.
This emphasis on verification was encapsulated in the verification
theory of meaning, which held that the meaning of a sentence was
its method of verification, implying that sentences without any
such method were meaningless. In psychology, this fueled
skepticism about the existence of internal mental representations
and states (whose existence could not be objectively verified), and
offered further philosophical backing for behaviorism.
In contrast to the ordinary language philosophers (many of whom
would have been professionally embarrassed to have been caught
knowing anything about science), the positivists held that
philosophy was to be informed about and sensitive to the results of
science. The distinctive task of the philosopher, however, was not
simply to describe scientific practice, but to offer a rational
reconstruction of it, one that made clear the logical
structure of science. Although the term "rational
reconstruction" was used first by Carnap in his 1928 book
The Logical Construction of the World, quite a general
epistemological tract, the technique to which it referred came to
be applied especially to scientific concepts and theories.
This played out in the frequent appeal to the distinction
between the context of discovery and the context of
justification, drawn as such by Reichenbach in Experience
and Prediction (1938) but with a longer history in the German
tradition. To consider an aspect of a scientific view in the
context of discovery was essentially to raise psychological,
sociological, or historical questions about how that view
originated, was developed, or came to be accepted or rejected. But
properly philosophical explorations of science were to be conducted
in the context of justification, raising questions and making
claims about the logical structure of science and the concepts it
used. Rational reconstruction was the chief way of divorcing the
relevant scientific theory from its mere context of discovery.
A story involving Feigl and Carnap nicely illustrates the
divorce between philosophy and science within positivism. In the
late 1950s, Feigl visited the University of California, Los
Angeles, to give a talk to the Department of Philosophy, of which
Carnap was a member. Feigl's talk was aimed at showing that a form
of physicalism, the mind-brain identity theory, faced an empirical
problem, since science had little, if anything, to say about the
"raw feel" of consciousness, the WHAT-IT'S-LIKE of experience. During the
question period, Carnap raised his hand, and was called on by
Feigl. "Your claim that current neurophysiology tells us nothing
about raw feels is wrong! You have overlooked the discovery of
alpha-waves in the brain," exclaimed Carnap. Feigl, who was
familiar with what he thought was the relevant science, looked
puzzled: "Alpha-waves? What are they?" Carnap replied: "My dear
Herbert. You tell me what raw feels are, and I will tell you what
alpha-waves are."
Of the multiple readings that this story invites (whose common
denominator is surely Carnap's savviness and wit), consider those
that take Carnap's riposte to imply that he thought that one could
defend materialism by, effectively, making up the science to fit
whatever phenomena critics could rustle up. A rather extreme form
of rational reconstruction, but it suggests one way in which the
positivist approach to psychology could be just as a priori and so
divorced from empirical practice as that of Ryle and Malcolm.
See also
The philosophy of science is integral to the
cognitive sciences in a number of ways. We have already seen that
positivists held views about the overall structure of science and
the grounds for theory choice in science that had implications for
psychology. Here I focus on three functions that the philosophy of
science plays vis-à-vis the cognitive sciences: it provides
a perspective on the place of psychology among the sciences; it
raises questions about what any science can tell us about the
world; and it explores the nature of knowledge and how it is known.
I take these in turn.
One classic way in which the sciences were viewed as being
unified, according to the positivists, was via reduction. REDUCTIONISM, in this context, is the view
that intuitively "higher-level" sciences can be reduced, in some
sense, to "lower-level" sciences. Thus, to begin with the case
perhaps of most interest to MITECS readers, psychology was held to
be reducible in principle to biology, biology to chemistry,
chemistry to physics. This sort of reduction presupposed the
existence of bridge laws, laws that exhaustively
characterized the concepts of any higher-level science, and the
generalizations stated using them, in terms of those concepts and
generalizations at the next level down. And because reduction was
construed as relating theories of one science to those of another,
the advocacy of reductionism went hand-in-hand with a view of EXPLANATION that gave lower-level sciences
at least a usurpatory power over their higher-level
derivatives.
This view of the structure of science was opposed to EMERGENTISM, the view that the
properties studied by higher-level sciences, such as psychology,
were not mere aggregates of properties studied by lower-level
sciences, and thus could not be completely understood in terms of
them. Both emergentism and this form of reductionism were typically
cast in terms of the relationship between laws in higher- and
lower-level sciences, thus presupposing that there were, in the
psychological case, PSYCHOLOGICAL LAWS in
the first place. One well-known position that denies this
assumption is Donald Davidson's ANOMALOUS
MONISM, which claims that while mental states are
strictly identical with physical states, our descriptions of them
as mental states are neither definitionally nor nomologically
reducible to descriptions of them as physical states. This view is
usually expressed as denying the possibility of the bridge laws
required for the reduction of psychology to biology.
Corresponding to the emphasis on scientific laws in views of the
relations between the sciences is the idea that these laws state
relations between NATURAL KINDS. The
idea of a natural kind is that of a type or kind of thing that
exists in the world itself, rather than a kind or grouping that
exists because of our ways of perceiving, thinking about, or
interacting with the world. Paradigms of natural kinds are
biological kinds -- species, such as the domestic cat (Felis
domesticus) -- and chemical kinds -- such as silver (Ag) and
gold (Au). Natural kinds can be contrasted with
artifactual kinds (such as chairs), whose members are
artifacts that share common functions or purposes relative to human
needs or designs; with conventional kinds (such as
marriage vows), whose members share some sort of conventionally
determined property; and from purely arbitrary groupings of
objects, whose members have nothing significant in common save that
they belong to the category. Views of what natural kinds are, of
how extensively science traffics in them, and of how we should
characterize the notion of a natural kind vis-à-vis other
metaphysic notions, such as essence, intrinsic property, and causal
power, all remain topics of debate in contemporary philosophy of
science (e.g., van Fraassen 1989; Wilson 1999).
There is an intuitive connection between the claims that there
are natural kinds, and that the sciences strive to identify them,
and scientific realism, the view that the entities in
mature sciences, whether they are observable or not, exist and our
theories about them are at least approximately true. For realists
hold that the sciences strive to "carve nature at its joints," and
natural kinds are the pre-existing joints that one's scientific
carving tries to find. The REALISM AND
ANTIREALISM issue is, of course, more complicated than
suggested by the view that scientific realists think there are
natural kinds, and antirealists deny this -- not least because
there are a number of ways to deny either this realist claim or to
diminish its significance. But such a perspective provides one
starting point for thinking about the different views one might
have of the relationship between science and reality.
Apart from raising issues concerning the relationships between
psychology and other sciences and their respective objects of
study, and questions about the relation between science and
reality, the philosophy of science is also relevant to the
cognitive sciences as a branch of epistemology or the theory of
knowledge, studying a particular type of knowledge, scientific
knowledge. A central notion in the general theory of knowledge is
JUSTIFICATION, because being justified
in what we believe is at least one thing that distinguishes
knowledge from mere belief or a lucky guess. Since scientific
knowledge is a paradigm of knowledge, views of justification have
often been developed with scientific knowledge in mind.
The question of what it is for an individual to have a justified
belief, however, has remained contentious in the theory of
knowledge. Justified beliefs are those that we are entitled to
hold, ones for which we have reasons, but how should we understand
such entitlement and such reasons? One dichotomy here is between
internalists about justification, who hold that having
justified belief exclusively concerns facts that are "internal" to
the believer, facts about his or her internal cognitive economy;
and externalists about justification, who deny this. A
second dichotomy is between naturalists, who hold that
what cognitive states are justified may depend on facts about
cognizers or about the world beyond cognizers that are uncovered by
empirical science; and rationalists, who hold that
justification is determined by the relations between one's
cognitive states that the agent herself is in a special position to
know about. Clearly part of what is at issue between internalists
and externalists, as well as between naturalists and rationalists,
is the role of the first-person perspective in accounts of
justification and thus knowledge (see also Goldman 1997).
These positions about justification raise some general questions
about the relationship between EPISTEMOLOGY
AND COGNITION, and interact with views of the importance of
first- and third-person perspectives on cognition itself. They also
suggest different views of RATIONAL
AGENCY, of what it is to be an agent who acts on the basis of
justified beliefs. Many traditional views of rationality imply that
cognizers have LOGICAL OMNISCIENCE,
that is, that they believe all the logical consequences of their
beliefs. Since clearly we are not logically omniscient, there is a
question of how to modify one's account of rationality to avoid
this result.
See also
At the outset, I said that the relation between
the mental and physical remains the central, general issue in
contemporary, materialist philosophy of mind. In section 2, we saw
that the behaviorist critiques of Cartesian views of the mind and
behaviorism themselves introduced a dilemma that derived from the
problem of the homunculus that any mental science would seem to
face. And in section 3 I suggested how a vibrant skepticism about
the scientific status of a distinctively psychological science and
philosophy's contribution to it was sustained by two dominant
philosophical perspectives. It is time to bring these three points
together as we move to explore the view of the mind that
constituted the core of the developing field of cognitive science
in the 1970s, what is sometimes called classic cognitive
science, as well as its successors.
If we were to pose questions central to each of these three
issues -- the mental-physical relation, the problem of the
homunculus, and the possibility of a genuinely cognitive science,
they might be:
- What is the relation between the mental and the physical?
- How can psychology avoid the problem of the homunculus?
- What makes a genuinely mental science possible?
Strikingly, these questions received
standard answers, in the form of three "isms," from the nascent
naturalistic perspective in the philosophy of mind that accompanied
the rise of classic cognitive science. (The answers, so you don't
have to peek ahead, are, respectively, functionalism,
computationalism, and representationalism.)
The answer to (a) is FUNCTIONALISM,
the view, baldly put, that mental states are functional states.
Functionalists hold that what really matters to the identity of
types of mental states is not what their instances are made of, but
how those instances are causally arranged: what causes them, and
what they, in turn, cause. Functionalism represents a view of the
mental-physical relation that is compatible with materialism or
physicalism because even if it is the functional or causal
role that makes a mental state the state it is, every
occupant of any particular role could be physical. The
role-occupant distinction, introduced explicitly by Armstrong
(1968) and implicitly in Lewis (1966), has been central to most
formulations of functionalism.
A classic example of something that is functionally identified
or individuated is money: it's not what it's made of
(paper, gold, plastic) that makes something money but, rather, the
causal role that it plays in some broader economic system.
Recognizing this fact about money is not to give up on the idea
that money is material or physical. Even though material
composition is not what determines whether something is money,
every instance of money is material or physical: dollar bills and
checks are made of paper and ink, coins are made of metal, even
money that is stored solely as a string of digits in your bank
account has some physical composition. There are at least
two related reasons why functionalism about the mind has
been an attractive view to philosophers working in the cognitive
sciences.
The first is that functionalism at least appears to support the
AUTONOMY OF PSYCHOLOGY, for it claims
that even if, as a matter of fact, our psychological states are
realized in states of our brains, their status as
psychological states lies in their functional
organization, which can be abstracted from this particular material
stuff. This is a nonreductive view of psychology. If
functionalism is true, then there will be distinctively
psychological natural kinds that cross-cut the kinds that are
determined by a creature's material composition. In the context of
materialism, functionalism suggests that creatures with very
different material organizations could not only have mental states,
but have the same kinds of mental states. Thus
functionalism makes sense of comparative psychological or
neurological investigations across species.
The second is that functionalism allows for
nonbiological forms of intelligence and mentality. That
is, because it is the "form" not the "matter" that determines
psychological kinds, there could be entirely artifactual creatures,
such as robots or computers, with mental states, provided that they
have the right functional organization. This idea has been central
to traditional artificial intelligence (AI), where one ideal has
been to create programs with a functional organization that not
only allows them to behave in some crude way like intelligent
agents but to do so in a way that instantiates at least some
aspects of intelligence itself.
Both of these ideas have been criticized as part of attacks on
functionalism. For example, Paul and Patricia Churchland (1981)
have argued that the "autonomy" of psychology that one gains from
functionalism can be a cover for the emptiness of the science
itself, and Jaegwon Kim (1993) has argued against the coherence of
the nonreductive forms of materialism usually taken to be implied
by functionalism. Additionally, functionalism and AI are the
targets of John Searle's much-discussed CHINESE ROOM ARGUMENT.
Consider (c), the question of what makes a distinctively mental
science possible. Although functionalism gives one sort of answer
to this in its basis for a defense of the autonomy (and so
distinctness) of psychology, because there are more functional
kinds than those in psychology (assuming functionalism), this
answer does not explain what is distinctively
psychological about psychology. A better answer to this
question is representationalism, also known as the
representational theory of mind. This is the view that mental
states are relations between the bearers of those states and
internal mental representations. Representationalism answers (c) by
viewing psychology as the science concerned with the forms these
mental representations can take, the ways in which they can be
manipulated, and how they interact with one another in mediating
between perceptual input and behavioral output.
A traditional version of representationalism, one cast in terms
of Ideas, themselves often conceptualized as images, was held by
the British empiricists John Locke, George Berkeley, and DAVID HUME. A form of representationalism,
the LANGUAGE OF THOUGHT (LOT) hypothesis, has more recently been
articulated and defended by Jerry Fodor (1975, 1981, 1987, 1994).
The LOT hypothesis is the claim that we
are able to cognize in virtue of having a mental language,
mentalese, whose symbols are combined systematically by
syntactic rules to form more complex units, such as thoughts.
Because these mental symbols are intentional or representational
(they are about things), the states that they compose are
representational; mental states inherit their intentionality from
their constituent mental representations.
Fodor himself has been particularly exercised to use the
language of thought hypothesis to chalk out a place for the PROPOSITIONAL ATTITUDES and our folk
psychology within the developing sciences of the mind. Not all
proponents of the representational theory of mind, however, agree
with Fodor's view that the system of representation underlying
thought is a language, nor with his defense of folk
psychology. But even forms of representationalism that are less
committal than Fodor's own provide an answer to the question of
what is distinctive about psychology: psychology is not mere
neuroscience because it traffics in a range of mental
representations and posits internal processes that operate on these
representations.
Representationalism, particularly in Fodoresque versions that
see the language of thought hypothesis as forming the foundations
for a defense of both cognitive psychology and our commonsense folk
psychology, has been challenged within cognitive science by the
rise of connectionism in psychology and NEURAL NETWORKS within computer science.
Connectionist models of psychological processing might be taken as
an existence proof that one does not need to assume what is
sometimes called the RULES AND
REPRESENTATIONS approach to understand cognitive functions: the
language of thought hypothesis is no longer "the only game in
town."
Connectionist COGNITIVE MODELING of
psychological processing, such as that of the formation of past
tense (Rumelhart and McClelland 1986), face recognition (Cottrell
and Metcalfe 1991), and VISUAL WORD
RECOGNITION (Seidenberg and McClelland 1989), typically does
not posit discrete, decomposable representations that are
concatenated through the rules of some language of thought. Rather,
connectionists posit a COGNITIVE
ARCHITECTURE made up of simple neuron-like nodes, with activity
being propagated across the units proportional to the weights of
the connection strength between them. Knowledge lies not in the
nodes themselves but in the values of the weights connecting nodes.
There seems to be nothing of a propositional form within such
connectionist networks, no place for the internal sentences that
are the objects of folk psychological states and other subpersonal
psychological states posited in accounts of (for example) memory
and reasoning.
The tempting idea that "classicists" accept, and connectionists
reject, representationalism is too simple, one whose implausibility
is revealed once one shifts one's focus from folk psychology and
the propositional attitudes to cognition more generally. Even when
research in classical cognitive science -- for example, that on KNOWLEDGE-BASED SYSTEMS and on BAYESIAN NETWORKS -- is cast in terms of
"beliefs" that a system has, the connection between "beliefs" and
the beliefs of folk psychology has been underexplored. More
importantly, the notion of representation itself has not been
abandoned across-the-board by connectionists, some of whom have
sought to salvage and adapt the notion of mental representation, as
suggested by the continuing debate over DISTRIBUTED VS. LOCAL REPRESENTATION
and the exploration of sub-symbolic forms of representation within
connectionism (see Boden 1990; Haugeland 1997; Smolensky 1994).
What perhaps better distinguishes classic and connectionist
cognitive science here is not the issue of whether some form of
representationalism is true, but whether the question to which it
is an answer needs answering at all. In classical cognitive
science, what makes the idea of a genuinely mental science
possible is the idea that psychology describes representation
crunching. But in starting with the idea that neural representation
occurs from single neurons up through circuits to modules and more
nebulous, distributed neural systems, connectionists are less
likely to think that psychology offers a distinctive level of
explanation that deserves some identifying characterization. This
rejection of question (c) is clearest, I think, in related DYNAMIC APPROACHES TO COGNITION, since
such approaches investigate psychological states as dynamic systems
that need not posit distinctly mental representations. (As
with connectionist theorizing about cognition, dynamic approaches
encompass a variety of views of mental representation and its place
in the study of the mind that make representationalism itself a
live issue within such approaches; see Haugeland 1991; van Gelder
1998.)
Finally, consider (b), the question of how to avoid the problem
of the homunculus in the sciences of the mind. In classic cognitive
science, the answer to (b) is computationalism, the view
that mental states are computational, an answer which integrates
and strengthens functionalist materialism and representationalism
as answers to our previous two questions. It does so in the
way in which it provides a more precise characterization
of the nature of the functional or causal relations that exist
between mental states: these are computational relations
between mental representations. The traditional way to spell
this out is the COMPUTATIONAL THEORY OF
MIND, according to which the mind is a digital computer, a
device that stores symbolic representations and performs operations
on them in accord with syntactic rules, rules that attend
only to the "form" of these symbols. This view of computationalism
has been challenged not only by relatively technical objections
(such as that based on the FRAME
PROBLEM), but also by the development of neural networks and
models of SITUATED COGNITION AND
LEARNING, where (at least some) informational load is shifted
from internal codes to organism-environment interactions (cf.
Ballard et al. 1997).
The computational theory of mind avoids the problem of the
homunculus because digital computers that exhibit some intelligence
exist, and they do not contain undischarged homunculi. Thus, if
we are fancy versions of such computers, then we can
understand our intelligent capacities without positing undischarged
homunculi. The way this works in computers is by having a series of
programs and languages, each compiled by the one beneath it, with
the most basic language directly implemented in the hardware of the
machine. We avoid an endless series of homunculi because the
capacities that are posited at any given level are typically
simpler and more numerous than those posited at any higher level,
with the lowest levels specifying instructions to perform actions
that require no intelligence at all. This strategy of FUNCTIONAL DECOMPOSITION solves the
problem of the homunculus if we are digital computers, assuming
that it solves it for digital computers.
Like representationalism, computationalism has sometimes been
thought to have been superseded by either (or both) the
connectionist revolution of the 1980s, or the Decade of the Brain
(the 1990s). But as with proclamations of the death of
representationalism, this notice of the death of computationalism
is premature. In part this is because the object of criticism is a
specific version of computationalism, not computationalism per se
(cf. representationalism), and in part it is because neural
networks and the neural systems in the head they model are both
themselves typically claimed to be computational in some sense. It
is surprisingly difficult to find an answer within the cognitive
science community to the question of whether there is a univocal
notion of COMPUTATION that underlies
the various different computational approaches to cognition on
offer. The various types of AUTOMATA
postulated in the 1930s and 1940s -- particularly TURING machines and the "neurons" of MCCULLOCH and PITTS, which form the intellectual
foundations, respectively, for the computational theory of mind and
contemporary neural network theory -- have an interwoven history,
and many of the initial putative differences between classical and
connectionist cognitive science have faded into the background as
research in artificial intelligence and cognitive modeling has
increasingly melded the insights of each approach into more
sophisticated hybrid models of cognition (cf. Ballard 1997).
While dynamicists (e.g., Port and van Gelder 1995) have
sometimes been touted as providing a noncomputational alternative
to both classic and connectionist cognitive science (e.g., Thelen
1995: 70), as with claims about the nonrepresentational stance of
such approaches, such a characterization is not well founded (see
Clark 1997, 1998). More generally, the relationship between
dynamical approaches to both classical and connectionist views
remains a topic for further discussion (cf. van Gelder and Port
1995; Horgan and Tienson 1996; and Giunti 1997).
See also
Much recent philosophical thinking about the mind
and cognitive science remains preoccupied with the three
traditional philosophical issues I identified in the first section:
the mental-physical relation, the structure of the mind, and the
first-person perspective. All three issues arise in one of the most
absorbing discussions over the last twenty years, that over the
nature, status, and future of what has been variously called
commonsense psychology, the propositional attitudes, or FOLK PSYCHOLOGY.
The term folk psychology was coined by Daniel Dennett
(1981) to refer to the systematic knowledge that we "folk" employ
in explaining one another's thoughts, feelings, and behavior; the
idea goes back to Sellars's Myth of Jones in "Empiricism and the
Philosophy of Mind" (1956). We all naturally and without explicit
instruction engage in psychological explanation by attributing
beliefs, desires, hopes, thoughts, memories, and emotions to one
another. These patterns of folk psychological explanation are
"folk" as opposed to "scientific" since they require no special
training and are manifest in everyday predictive and explanatory
practice; and genuinely "psychological" because they posit the
existence of various states or properties that seem to be
paradigmatically mental in nature. To engage in folk psychological
explanation is, in Dennett's (1987) terms, to adopt the INTENTIONAL STANCE.
Perhaps the central issue about folk psychology concerns its
relationship to the developing cognitive sciences. ELIMINATIVE MATERIALISM, or eliminativism, is
the view that folk psychology will find no place in any of the
sciences that could be called "cognitive" in orientation; rather,
the fortune of folk psychology will be like that of many other folk
views of the world that have found themselves permanently out of
step with scientific approaches to the phenomena they purport to
explain, such as folk views of medicine, disease, and
witchcraft.
Eliminativism is sometimes motivated by adherence to
reductionism (including the thesis of EXTENSIONALITY) and the ideal of the unity
of science, together with the recognition that the propositional
attitudes have features that set them off in kind from the types of
entity that exist in other sciences. For example, they are
intentional or representational, and attributing them to
individuals seems to depend on factors beyond the boundary of those
individuals, as the TWIN EARTH arguments
suggest. These arguments and others point to a prima facie conflict
between folk psychology and INDIVIDUALISM (or internalism) in
psychology (see Wilson 1995). The apparent conflict between folk
psychology and individualism has provided one of the motivations
for developing accounts of NARROW
CONTENT, content that depends solely on an individual's
intrinsic, physical properties. (The dependence here has usually
been understood in terms of the technical notion of SUPERVENIENCE; see Horgan 1993.)
There is a spin on this general motivation for eliminative
materialism that appeals more directly to the issue of the how the
mind is structured. The claim here is that whether folk psychology
is defensible will turn in large part on how compatible its
ontology -- its list of what we find in a folk psychological mind
-- is with the developing ontology of the cognitive sciences. With
respect to classical cognitive science, with its endorsement of
both the representational and computational theories of mind, folk
psychology is on relatively solid ground here. It posits
representational states, such as belief and desire, and it is
relatively easy to see how the causal relations between such states
could be modeled computationally. But connectionist models of the
mind, with what representation there is lying in patterns of
activity rather than in explicit representations like propositions,
seem to leave less room in the structure of the mind for folk
psychology.
Finally, the issue of the place of the first-person perspective
arises with respect to folk psychology when we ask how people
deploy folk psychology. That is, what sort of psychological
machinery do we folk employ in engaging in folk psychological
explanation? This issue has been the topic of the SIMULATION VS. THEORY-THEORY debate, with
proponents of the simulation view holding, roughly, a "first-person
first" account of how folk psychology works, and theory-theory
proponents viewing folk psychology as essentially a third-person
predictive and explanatory tool. Two recent volumes by Davies and
Stone (1995a, 1995b) have added to the literature on this debate,
which has developmental and moral aspects, including implications
for MORAL PSYCHOLOGY.
See also
Although BRENTANO's
claim that INTENTIONALITY is the "mark of
the mental" is problematic and has few adherents today,
intentionality has been one of the flagship topics in philosophical
discussion of the mental, and so at least a sort of mark of that
discussion. Just what the puzzle about intentionality is and what
one might say about it are topics I want to explore in more detail
here.
To say that something is intentional is just to say that it is
about something, or that it refers to something.
In this sense, statements of fact are paradigmatically intentional,
since they are about how things are in the world. Similarly, a
highway sign with a picture of a gas pump on it is intentional
because it conveys the information that there is gas station ahead
at an exit: it is, in some sense, about that state of affairs.
The beginning of chapter 4 of Jerry Fodor's
Psychosemantics provides one lively expression of the
problem with intentionality:
I suppose that sooner or later the physicists will
complete the catalogue they've been compiling of the ultimate and
irreducible properties of things. When they do, the likes of
spin, charm, and charge will perhaps appear upon
their list. But aboutness surely won't; intentionality
simply doesn't go that deep. It's hard to see, in face of this
consideration, how one can be a Realist about intentionality
without also being, to some extent or other, a Reductionist. If the
semantic and the intentional are real properties of things, it must
be in virtue of their identity with (or maybe of their
supervenience on?) properties that are themselves neither
intentional nor semantic. If aboutness is real, it must be
really something else. (p. 97, emphases in original)
Although there is much that one could take
issue with in this passage, my reason for introducing it here is
not to critique it but to try to capture some of the worries about
intentionality that bubble up from it.
The most general of these concerns the basis of
intentionality in the natural order: given that only special parts
of the world (like our minds) have intentional properties, what is
it about those things that gives them (and not other things)
intentionality? Since not only mental phenomena are intentional
(for example, spoken and written natural language and systems of
signs and codes are as well), one might think that a natural way to
approach this question would be as follows. Consider all of the
various sorts of "merely material" things that at least seem to
have intentional properties. Then proceed to articulate why each of
them is intentional, either taking the high road of specifying
something like the "essence of intentionality" -- something that
all and only things with intentional properties have -- or taking
the low road of doing so for each phenomenon, allowing these
accounts to vary across disparate intentional phenomena.
Very few philosophers have explored the problem of
intentionality in this way. I think this is chiefly because they do
not view all things with intentional properties as having been
created equally. A common assumption is that even if lots of the
nonmental world is intentional, its intentionality is
derived, in some sense, from the intentionality of the
mental. So, to take a classic example, the sentences we utter and
write are intentional all right (they are about things). But their
intentionality derives from that of the corresponding thoughts that
are their causal antecedents. To take another often-touted example,
computers often produce intentional output (even photocopiers can
do this), but whatever intentionality lies in such output is not
inherent to the machines that produce it but is derivative,
ultimately, from the mental states of those who design, program,
and use them and their products. Thus, there has been a focus on
mental states as a sort of paradigm of intentional state, and a
subsequent narrowing of the sorts of intentional phenomena
discussed. Two points are perhaps worth making briefly in this
regard.
First, the assumption that not all things with intentional
properties are created equally is typically shared even by those
who have not focused almost exclusively on mental states as
paradigms of intentional states, but on languages and other public
and conventional forms of representation (e.g., Horst 1996). It is
just that their paradigm is different.
Second, even when mental states have been taken as a
paradigm here, those interested in developing a "psychosemantics"
-- an account of the basis for the semantics of psychological
states -- have often turned to decidedly nonmental systems of
representation in order to theorize about the intentionality of the
mental. This focus on what we might think of as
proto-intentionality has been prominent within both Fred
Dretske's (1981) informational semantics and the biosemantic
approach pioneered by Ruth Millikan (1984, 1993).
The idea common to such views is to get clear about the grounds
of simple forms of intentionality before scaling up to the case of
the intentionality of human minds, an instance of a research
strategy that has driven work in the cognitive sciences from early
work in artificial intelligence on KNOWLEDGE
REPRESENTATION and cognitive modeling through to contemporary
work in COMPUTATIONAL NEUROSCIENCE.
Exploring simplified or more basic intentional systems in the hope
of gaining some insight into the more full-blown case of the
intentionality of human minds runs the risk, of course, of focusing
on cases that leave out precisely that which is crucial to
full-blown intentionality. Some (for example, Searle 1992) would
claim that consciousness and phenomenology are such features.
As I hinted at in my discussion of the mind in cognitive science
in section 5, construed one way the puzzle about the grounds of
intentionality has a general answer in the hypothesis of
computationalism. But there is a deeper problem about the grounds
of intentionality concerning just how at least some mental
stuff could be about other stuff in the world, and computationalism
is of little help here. Computationalism does not even pretend to
answer the question of what it is about specific mental states
(say, my belief that trees often have leaves) that gives them the
content that they have -- for example, that makes them about
trees. Even if we were complicated Turing machines,
what would it be about my Turing machine table that
implies that I have the belief that trees often have leaves?
Talking about the correspondence between the semantic and syntactic
properties that symbol structures in computational systems have,
and of how the former are "inherited" from the latter is well and
good. But it leaves open the "just how" question, and so fails to
address what I am here calling the deeper problem about the grounds
of intentionality. This problem is explored in the article on MENTAL REPRESENTATION, and particular
proposals for a psychosemantics can be found in those on INFORMATIONAL SEMANTICS and FUNCTIONAL ROLE SEMANTICS.
It would be remiss in exploring mental content to fail to
mention that much thought about intentionality has been propelled
by work in the philosophy of language: on INDEXICALS AND DEMONSTRATIVES, on theories
of REFERENCE and the propositional
attitudes, and on the idea of RADICAL
INTERPRETATION. Here I will restrict myself to some brief
comments on theories of reference, which have occupied center stage
in the philosophy of language for much of the last thirty
years.
One of the central goals of theories of reference has been to
explain in virtue of what parts of sentences of natural languages
refer to the things they refer to. What makes the name "Miranda"
refer to my daughter? In virtue of what does the plural noun "dogs"
refer to dogs? Such questions have a striking similarity to my
above expression of the central puzzle concerning intentionality.
In fact, the application of causal theories of reference (Putnam
1975, Kripke 1980) developed principally for natural languages has
played a central role in disputes in the philosophy of mind that
concern intentionality, including those over individualism, narrow
content, and the role of Twin Earth arguments in thinking about
intentionality. In particular, applying them not to the meaning of
natural language terms but to the content of thought is one way to
reach the conclusion that mental content does not
supervene on an individual's physical properties, that is, that
mental content is not individualistic.
GOTTLOB FREGE is a classic source for
contrasting descriptivist theories of reference, according to which
natural language reference is, in some sense, mediated by a
speaker's descriptions of the object or property to which she
refers. Moreover, Frege's notion of sense and the distinction
between SENSE AND REFERENCE are often
invoked in support of the claim that there is much to MEANING -- linguistic or mental -- that goes
beyond the merely referential. Frege is also one of the founders of
modern logic, and it is to the role of logic in the cognitive
sciences that I now turn.
See also
Although INDUCTION,
like deduction, involves drawing inferences on the basis of one or
more premises, it is deductive inference that has been the
focus in LOGIC, what is often simply
referred to as "formal logic" in departments of philosophy and
linguistics. The idea that it is possible to abstract away from
deductive arguments given in natural language that differ in the
content of their premises and conclusions goes back at least to
Aristotle in the fourth century B.C. Hence the term "Aristotelian
syllogisms" to refer to a range of argument forms containing
premises and conclusions that begin with the words "every" or
"all," "some," and "no." This abstraction makes it possible to talk
about argument forms that are valid and invalid, and
allows one to describe two arguments as being of the same
logical form. To take a simple example, we know that any
argument of the form:
All A are B.
No B are C.
No A are C.
is formally valid, where the
emphasis here serves to highlight reference to the preservation of
truth from premises to conclusion, that is, the validity, solely in
virtue of the forms of the individual sentences, together with the
form their arrangement constitutes. Whatever plural noun phrases we
substitute for "A," "B," and "C," the resulting natural language
argument will be valid: if the two premises are true, the
conclusion must also be true. The same general point applies to
arguments that are formally invalid, which makes it
possible to talk about formal fallacies, that is,
inferences that are invalid because of the forms they
instantiate.
Given the age of the general idea of LOGICAL FORM, what is perhaps surprising
is that it is only in the late nineteenth century that the notion
was developed so as to apply to a wide range of natural language
constructions through the development of the propositional
and predicate logics. And it is only in the late twentieth
century that the notion of logical form comes to be appropriated
within linguistics in the study of SYNTAX. I focus here on the developments
in logic.
Central to propositional logic (sometimes called "sentential
logic") is the idea of a propositional or sentential
operator, a symbol that acts as a function on propositions
or sentences. The paradigmatic propositional operators are symbols
for negation ("~"), conjunction ("&"), disjunction ("∨"),
and conditional ("→"). And with the development of formal
languages containing these symbols comes an ability to represent a
richer range of formally valid arguments, such as that manifest in
the following thought:
If Sally invites Tom, then either he will say
"no," or cancel his game with Bill. But there's no way he'd turn
Sally down. So I guess if she invites him, he'll cancel with
Bill.
In predicate or quantificational logic, we
are able to represent not simply the relations between
propositions, as we can in propositional logic, but also the
structure within propositions themselves through the introduction
of QUANTIFIERS and the terms and
predicates that they bind. One of the historically more important
applications of predicate logic has been its widespread use in
linguistics, philosophical logic, and the philosophy of language to
formally represent increasingly larger parts of natural languages,
including not just simple subjects and predicates, but adverbial
constructions, tense, indexicals, and attributive adjectives (for
example, see Sainsbury 1991).
These fundamental developments in logical theory have had
perhaps the most widespread and pervasive effect on the foundations
of the cognitive sciences of any contributions from
philosophy or mathematics. They also form the basis for much
contemporary work across the cognitive sciences: in linguistic
semantics (e.g., through MODAL LOGIC,
in the use of POSSIBLE WORLDS
SEMANTICS to model fragments of natural language, and in work
on BINDING); in metalogic (e.g., on FORMAL SYSTEMS and results such as the CHURCH-TURING THESIS and GÖDEL'S THEOREMS); and in artificial
intelligence (e.g., on LOGICAL REASONING
SYSTEMS, TEMPORAL REASONING, and METAREASONING).
Despite their technical payoff, the relevance of these
developments in logical theory for thinking more directly about DEDUCTIVE REASONING in human beings is,
ironically, less clear. Psychological work on human reasoning,
including that on JUDGMENT HEURISTICS,
CAUSAL REASONING, and MENTAL MODELS, points to ways in
which human reasoning may be governed by structures very different
from those developed in formal logic, though this remains an area
of continuing debate and discussion.
See also
By the late nineteenth century, both evolutionary
theory and the physiological study of mental capacities were firmly
entrenched. Despite this, these two paths to a biological view of
cognition have only recently been re-explored in sufficient depth
to warrant the claim that contemporary cognitive science
incorporates a truly biological perspective on the mind. The
neurobiological path, laid down by the tradition of physiological
psychology that developed from the mid-nineteenth century, is
certainly the better traveled of the two. The recent widening of
this path by those dissatisfied with the distinctly nonbiological
approaches adopted within traditional artificial intelligence has,
as we saw in our discussion of computationalism, raised new
questions about COMPUTATION AND THE
BRAIN, the traditional computational theory of the mind, and
the rules and representations approach to understanding the mind.
The evolutionary path, by contrast, has been taken only
occasionally and half-heartedly over the last 140 years. I want to
concentrate not only on why but on the ways in which evolutionary
theory is relevant to contemporary interdisciplinary work on the
mind.
The theory of EVOLUTION makes a
claim about the patterns that we find in the biological
world -- they are patterns of descent -- and a claim about
the predominant cause of those patterns -- they are caused by the
mechanism of natural selection. None of the recent debates
concerning evolutionary theory -- from challenges to the focus on
ADAPTATION AND ADAPTATIONISM in Gould
and Lewontin (1979) to more recent work on SELF-ORGANIZING SYSTEMS and ARTIFICIAL LIFE -- challenges the substantial
core of the theory of evolution (cf. Kauffman 1993, 1995; Depew and
Weber 1995). The vast majority of those working in the cognitive
sciences both accept the theory of evolution and so think that a
large number of traits that organisms possess are adaptations to
evolutionary forces, such as natural selection. Yet until the last
ten years, the scattered pleas to apply evolutionary theory to the
mind (such as those of Ghiselin 1969 and Richards 1987) have come
largely from those outside of the psychological and behavioral
sciences.
Within the last ten years, however, a distinctive EVOLUTIONARY PSYCHOLOGY has developed as a
research program, beginning in Leda Cosmides's (1989) work on human
reasoning and the Wason selection task, and represented in the
collection of papers The Adapted Mind (Barkow, Cosmides,
and Tooby 1992) and, more recently and at a more popular level, by
Steven Pinker's How the Mind Works (1997). Evolutionary
psychologists view the mind as a set of "Darwinian algorithms"
designed by natural selection to solve adaptive problems faced by
our hunter-gatherer ancestors. The claim is that this basic
Darwinian insight can and should guide research into the cognitive
architecture of the mind, since the task is one of discovering and
understanding the design of the human mind, in all its
complexity. Yet there has been more than an inertial resistance to
viewing evolution as central to the scientific study of human
cognition.
One reason is that evolutionary theory in general is seen as
answering different questions than those at the core of the
cognitive sciences. In terms of the well-known distinction between
proximal and ultimate causes, appeals to
evolutionary theory primarily allow one to specify the latter, and
cognitive scientists are chiefly interested in the former: they are
interested in the how rather than the why of the
mind. Or to put it more precisely, central to cognitive science is
an understanding of the mechanisms that govern cognition,
not the various histories -- evolutionary or not -- that produced
these mechanisms. This general perception of the concerns of
evolutionary theory and the contrasting conception of cognitive
science, have both been challenged by evolutionary psychologists.
The same general challenges have been issued by those who think
that the relations between ETHICS AND
EVOLUTION and those between cognition and CULTURAL EVOLUTION have not received their
due in contemporary cognitive science.
Yet despite the skepticism about this direct application of
evolutionary theory to human cognition, its implicit application is
inherent in the traditional interest in the minds of other
animals, from aplysia to (nonhuman) apes. ANIMAL NAVIGATION, PRIMATE LANGUAGE, and CONDITIONING AND THE BRAIN, while
certainly topics of interest in their own right, gain some added
value from what their investigation can tell us about
human minds and brains. This presupposes something like
the following: that there are natural kinds in psychology that
transcend species boundaries, such that there is a general way of
exploring how a cognitive capacity is structured, independent of
the particular species of organism in which it is instantiated (cf.
functionalism). Largely on the basis of research with non-human
animals, we know enough now to say, with a high degree of
certainty, things like this: that the CEREBELLUM is the central brain structure
involved in MOTOR LEARNING, and that the LIMBIC SYSTEM plays the same role with
respect to at least some EMOTIONS.
This is by way of returning to (and concluding with) the
neuroscientific path to biologizing the mind, and the three classic
philosophical issues about the mind with which we began. As I hope
this introduction has suggested, despite the distinctively
philosophical edge to all three issues -- the mental-physical
relation, the structure of the mind, and the first-person
perspective -- discussion of each of them is elucidated and
enriched by the interdisciplinary perspectives provided by
empirical work in the cognitive sciences. It is not only a priori
arguments but complexities revealed by empirical work (e.g., on the
neurobiology of consciousness, or ATTENTION and animal and human brains) that
show the paucity of the traditional philosophical "isms" (dualism,
behaviorism, type-type physicalism) with respect to the
mental-physical relation. It is not simply general, philosophical
arguments against nativism or against empiricism about the
structure of the mind that reveal limitations to the global
versions of these views, but ongoing work on MODULARITY AND LANGUAGE, on cognitive
architecture, and on the innateness of language. And thought about
introspection and self-knowledge, to take two topics that arise
when one reflects on the first-person perspective on the mind, is
both enriched by and contributes to empirical work on BLINDSIGHT, the theory of mind, and METAREPRESENTATION. With some luck,
philosophers increasingly sensitive to empirical data about the
mind will have paved a two-way street that encourages
psychologists, linguists, neuroscientists, computer scientists,
social scientists and evolutionary theorists to venture more
frequently and more surely into philosophy.
See also
Acknowledgments
I would like to thank Kay Bock, Bill Brewer, Alvin
Goldman, John Heil, Greg Murphy, Stewart Saunders, Larry Shapiro,
Sydney Shoemaker, Tim van Gelder, and Steve Wagner, as well as the
PNP Group at Washington University, St. Louis, for taking time out
to provide some feedback on earlier versions of this introduction.
I guess the remaining idiosyncrasies and mistakes are mine.
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