WHAT SHOULD WE EXPECT FROM A THEORY OF CONSCIOUSNESS?
Patricia Smith Churchland
University of California San Diego
Within the domain of philosophy, it is not
unusual to hear the claim that most questions
about the nature of consciousness are essentially
and absolutely beyond the scope of science,
no matter how science may develop in the
twenty-first century. Some things, it is
pointed out, we shall never ever understand,
and consciousness is one of them (Vendler
1994, Swinburne 1994, McGinn 1989, Nagel
1994, Warner 1994). One line of reasoning
assumes that consciousness is the manifestation
of a distinctly non-physical thing, and hence
has no physical properties that might be
explored by techniques suitable to physical
Dualism, as this view is known,
is still to be found among those within the
tradition of Kant and Hegel, as well as among
some with religious convictions. Surprisingly,
however, strenuous foot-dragging is evident
even among philosophers of a materialist
conviction. Indeed, one might say that it
is the philosophical fashion of the 90's
to pronounce consciousness unexplainable,
and to find the explanatory aspirations of
neurobiology to be faintly comic if not rather
pitiful. The very word, "reductionism"
has come to be used more or less synonymously
where scientistm apparently means "applying
scientific techniques to domains where they
McGinn, perhaps the most unblushing
of the naysayers, insists that we cannot
expect even to make any headway on the problem.
(p. 114) Ironically perhaps, here we are
at a conference in honor of Dr. Herbert Jasper
who was a great pioneer in moving neuroscience
forward on this problem, and where results
will be presented allegedly showing additional
progress on the problem. Because I am quite
optimistic about future scientific progress
on the nature of consciousness, my aim here,
as a philosopher, is to address the most
popular and influential of the skeptical
arguments, and to explain why I find them
unconvincing. Thus the overall form of the
paper is negative, in the sense that I want
to show why a set of naysaying arguments
fail. The positive part of the story derives
from the actual progress being made on the
topic, but I shall leave it to my neuroscience
colleagues to present the data and details
on that. Section II will focus on skeptical
arguments raised essentially in protest to
reductionist programs, and Section III will
examine a range of skeptical arguments arising
from consideration of what we do not yet
II REDUCTIONISM -- SHOULD WE EXPECT AN EXPLANATION
As a framework for my discussion, I shall
first characterize the notion of scientific
reduction, as we understand it from examples
in the history of science. In its starkest
description, a reduction is an explanation
of some macrolevel phenomenon in terms of
the organization and constituents of some
lower level microphenomenon. That is, the
macro properties are discovered to be the
outcome of the nature of the elements at
the microlevel, together with their dynamics
and interactions. In the classic examples,
this means that the causal powers of the
macro phenomenon are explained as a function
of the dynamics and causal powers of the
micro phenomenon. Is the function a simple
function -- such as that the "whole
is nothing but the sum of the parts"?
Virtually never. Summation is a supremely
simple function, and macro properties such
as temperature in a gas, or reflection of
light or being a visible spark or inheriting
red hair are anything but simple functions
of their causally potent underlying structures.
What does the history of science
reveal about reductive explanations that
might be helpful in understanding the issue
before us? Let me t ry to answer this by
briefly discussing three cases. The first
concerns the discovery that we could identify
temperature in a gas as the mean kinetic
energy of its constituent molecules. This
then permitted coherent, unified explanation
of temperature phenomena such as conduction,
of why temperature and pressure are related
in the way they are, of why heated things
expand. The first success with gases allowed
the extension of the explanatory framework
to embrace liquids and solids, and eventually
plasmas and even empty space. As a theory,
it was far more successful than the caloric
theory, which postulated a subtly compressible
fluid as increasing in volume when a things
temperature increases. Substances differ
in the rate at which caloric can flow through
them, and at which they can acquire or lose
caloric. The explanation of the nature of
light can be seen as another successful example
of scientific reductionism. In this instance,
the macro theory (optics) came to be seen
as explainable in terms of micro theory (theory
of electromagnetic radiation); visible light
turned out to be EMR, along with X-rays,
utlraviolet rays, radio waves, and so forth.
Note also that here, as elsewhere, further
questions always remain to be answered, and
hence there is a sense in which the reduction
is typically incomplete.
If the overarching mysteries
are resolved, however, that is usually sufficient
for scientists to consider an explanation
-- and hence a reduction -- to be essentially
in place. Reductions can be very messy, in
the sense that the mapping of properties
from micro to macro can be one: many or even
many: many, rather than the ideal, 1:1. While
the case of light reducing to EMR is relatively
clean, the case of phenotypic traits and
genes is far less clean. Genes, as we now
know, cannot be counted on to be single stretches
of DNA, but may involved distinct segments
of DNA. Additionally, a given gene may participate
in different macro properties as a function
of prior conditions. (Kitcher 1984)
Nevertheless, many molecular
biologists see their explanatory framework
as essentially reductive in character, mainly
because a causal route from base-pair sequences
to traits such as Huntington's disease can
be traced or at the very least, sketched
in outline. The details can be expected to
be filled out as experimental results come
in. On the other hand, the lack of a clean
line has prompted some philosophers, for
example Philip Kitcher, to propose that perhaps
these messy cases are best thought of not
genuinely reductive. I view that as essentially
a semantic recommendation, which promises
some clarity in understanding, but which
also has the drawback that in fact most scientists
view molecular biology as impressive instance
of reductive explanation -- incompleteness,
messiness, and complexity notwithstanding.
I am inclined to stick with the word 'reduction',
despite the complications in the biological
domain, because there is really nothing suitable
to take its place, and because linguistic
inertia is usually a sign that current usage
is in fact useful. Given this general characterization
of reduction and reductionism, I shall now
address five skeptical problems.
1. SHOULD WE EXPECT CONSCIOUSNESS TO "GO
One difficulty, according to the skeptics,
is that if consciousness is reduced to neuronal
activities, then we are landed in the absurd
position of saying that my pains, tastes
and so forth are not real. (Searle, 1993)
This worry is, in my view, based on misinformation
concerning what reductions in science do
and do not entail. The short answer to the
topic question, therefore, is "No: pains
will not cease to be real just because we
understand the neurobiology of pain."
That is, a reductive explanation of a macro
phenomenon in terms of the dynamics of its
microstructural features does not mean that
the macro phenomenon is not real or is scientifically
disreputableor somehow explanatorily unworthy
or redundant. Even after we achieved an explanation
of light in terms of EMR, theory of optics
continues to be useful, to discover new things.
Nobody thinks light is not real, as result
of Maxwell's equations. Rather, we think
we understand more about the real nature
of light than we did before 1873.
Light is real, no doubt
about it. But we now see visible light as
but one segment of a wider spectrum that
includes x-rays, ultraviolet, and radio waves.
We can now explain a whole lot at the macro
level that we were unable to explain before,
such as why a beam of light passed through
a narrow slit shows a two-smudge interference
pattern. Somewhat similar comments can be
made concerning the aftermath of the reductive
achievement of statistical mechanics.
Temperature is taken
to be a real property, and the study of the
macro level itself remains in good standing.
Thermodynamics continues to be capable of
revealing new and interesting scientific
truths, despite the existence of statistical
mechanics, and indeed it is well-aided by
its undergirding. Sometimes, however, hitherto
respectable properties and substances do
turn out to be unreal. The caloric theory
of heat, for example, did not survive the
rigors of science, and caloric fluid turned
out not to be real. The theory was explanatorily
problematic, especially when it had to address
this problem: if heat from rubbing is to
be explained by release of caloric in the
spaces between the atoms, it should run out
after a while. But, oddly for the theory,
rubbing can be continued indefinitely and
the heat does not stop being produced. If
anything, rubbed things get hotter the longer
they are rubbed. The molecules-in-motion
approach could explain this quite simply:
macro motion is translated into micro motion.
Caloric theory also stumbled
in its energy calculations for steam engines.
On the caloric accounting, some caloric had
to have disappeared by the end of a period
of steam-engine activity, but the data proved
otherwise. The molecules-in-motion theory
got the accounting correct, because it claimed
that the micro motions (heat) were transformed
into macromotions -- movement of the engine
wheel. In the end, caloric fluid was no match
for molecular motion as an approach to thermal
phenomena. Theories range themselves on a
spectrum of how little or how much of the
macro theory comes to be modified as a result
of increasing explanatory reach of the micro
theory. Revision of hypotheses is a major
hallmark of science and how it makes progress,
so it is no surprise to see revision as reductive
macro-micro progress is made. The degree
of revision required will obviously vary
from case to case, and will depend on how
the facts fall out. What will be the fate
of our current conception of 'consciousness'
as we discover more about the nature of the
brain will depend on the facts of the matter
and the long-term integrity of current macrolevel
concepts. (See P. M. Churchland 1994)
Some revisions to the
concept of consciousness, as it stood circa
1950, are already in evidence owing to the
impact of data on core beliefs about consciousness.
The discovery by Sperry and his colleagues
concerning the effects of commissurotomy
did, I think, make it evident that unity
in conscious experience has a lot to do with
connections in brain wiring, and hence was
not a kind of transcendental necessity. Research
on sleep and dreaming revealed that there
was far more dreaming going on the introspection
was led to believe, and that even in matters
of dream content, considerations of learning
and "neural housekeeping" probably
play at least as important a role as conflict-resolution
or wish-fulfillment. In addition, the regularity
in nightly cycles of behavioral state and
their control brain stem mechanisms such
as the locus ceruleus and the giant neurons
on the pons strongly implicate a neurobiological,
rather than a psychological explanation.
The discoveries concerning
the biological parameters of dreaming has
been critical in shifting our understanding
away from a Freudian or Jungian conception
of the nature and significance of dreaming
to a more biologically based conception.
(E. g. Hobson, 1988) Blindsight constitutes
another phenomenon where research revealed
something very disruptive to our a priori
assumptions: conscious, deliberate behavior
could be based on visual signals of which
the subject had no visual experience (Weiskrantz
1986, 1997). Initially, many philosophers
found this so counter-intuitive as to be
a violation of rationality itself, though
it has now become accepted as s puzzling
phenomenon whose empirical basis can be studied.
Of comparable significance
is the discovery that even in perception,
introspective data can mislead us concerning
the nature of the psychological processes
involved. There are many examples here, but
perhaps an especially dramatic one is the
finding that in visual perception, only a
tiny area (about 2 degrees) of the visual
field is foveated and hence perceived in
crisp detail at any given moment. Saccades,
made about every 300 msec, and neuronal integration
of signals across saccadic movement, contribute
to the illusion full-field detail. Additionally,
a whole range of data from neurology -- from
anosognosia to the amnesias to Balint's syndrome
-- showed that conscious belief structures
are not organized strictly according to the
canons of logic.
The possibility that
conscious experience may well be an assortment
of various capacities flying in loose formation
is now uncontroversial, but a mere twenty
years ago it seemed outrageous. By the 1990's,
it has been generally acknowledged that quite
different phenomena, such as (a) perceptual
awareness, (b) something like metacognition
(knowing that you do not know how many second
cousins you have) and (c) knowing that you
want to convert your bonds to stocks, may
be subserved by rather different neurobiological
mechanisms. In sum, the short answer to the
lead question, "should we expect consciousness
to go away?" is this: "No."
The various phenomena we group together as
conscious phenomena will not, of course,
go away. Nevertheless, we may come to conceptualize
them in somewhat different -- and perhaps
even very different -- ways.
2. SHOULD WE EXPECT CONSCIOUSNESS TO BE EMERGENT?
As a prelude to warning neuroscience off
the topic, we are often told that consciousness
is an emergent property. But what does it
mean to call a property 'emergent'? On one
version, it means that there can be no explanation
of that property in micro terms. Consequently,
if it is then claimed that consciousness
cannot be explained because it is emergent,
that simply comes to this obviously circular
hypothesis: consciousness cannot be explained
because it cannot be explained.
To avoid the circularity,
some (Broad 1951, Popper 1978) have suggested
a more careful meaning of 'emergent': if
a property is emergent, then it cannot be
predicted from knowledge of the microproperties.
For example, it is alleged that even if you
did know all the microproperties of water,
you could not predict that it would be wet.
If the macroproperty cannot be predicted
from knowledge of the micropoperties, the
story goes, then science will never be able
to explain it as the outcome of microproperties.
This view tends to see prediction and explanation
as two sides of the same coin.
Philosophers have objected
to this on grounds that prediction and explanation
are not in fact complementary, as the metaphor
implies. It is generally considered that
physics does have an explanation for the
wetness of water, whether or not anyone could
have predicted it from the micro properties.
Additionally, there is a logical reason why
predictability does not work very well as
a criterion for eventual explainability:
the very same ideas that support the hunch
that something cannot be explained are invoked
to support the premise that no one could
predict the macro property even if they knew
the microstructure. Thus there is a circularity
here as well. Broad thought it would help
if you took the predictor to be an archangel,
and others have suggested an omnipotent god
might serve in that role. Thought-experiments
that depend on agreeing what a very smart
archangel might or might not be able to predict
tend to lack credibility and certainly lack
consensus, and I confess I do not find them
very helpful as a index of anything.
Perhaps the most sophisticated
argument on this approach is owed to the
Australian philosopher Frank Jackson (1982).
In sum, Jackson's idea was that there could
exist someone, call her Mary, who knew everything
there was to know about how the brain works
but still did not know what it was to see
the color green (suppose she lacked "green
cones and wiring", to put it crudely.)
This possibility Jackson took to show that
qualia (the visual experience itself) are
therefore not explainable by science. That
is, if qualia were just patterns of neural
activity, then if Mary knows what neural
activity allegedly constitutes having a visual
experience of green, then she should know
what green qualia are like. There are various
weaknesses in this argument, but the main
problem with the argument is that to experience
green (have green qualia), certain wiring
has to be in place in Mary's brain, and certain
patterns of activity have to obtain. Since,
by Jackson's own hypothesis, she does not
have that wiring, then presumably the relevant
activity patterns in visual cortex are not
caused and she does not experience green.
Her knowing all of the relevant neurobiology
(not unlike Broad's imagined archangel) presumably
involves propositional knowledge, and probably
the learning is widely distributed in the
Who would expect her
visual cortex -- V4, let us suppose -- would
be activated in the "green qualia"
pattern just by virtue of her propositional
(linguistic) knowledge about activity patterns
in V4? Not me, anyhow. Jackson's argument
has to assume that either knowing the neurobiology
of "green qualia" somehow will
bring about experiencing green qualia or
that qualia are not scientifically approachable.
But both alternatives are probably false.
I suppose knowing the neurobiology of "green
qualia" could somehow or other bring
about experiencing green qualia, but I see
no reason to expect that it should. Via channels
bypassing the color circuits, Mary can have
propositional knowledge, including the knowledge
of what her own brain lacks in terms of "green-qualia-wiring".
As Paul Teller (1992) puts it, the subjectivity
of the experience is just the having of the
experience, not some ineffable kind of knowledge.
Nothing whatever follows about whether science
can or cannot explain qualia. Within neuroscience,
there is a useful and nonmystical notion
of emergence: a property is emergent if it
is a network property -- if it is the outcome
of the intrinsic properties of the neurons,
together with the way they interact. In this
less metaphysical sense, the rhythmicity
of the stomatogastric ganglion of the lobster
is an emergent property.
(Selverston and Moulins 1987) One reason
to prefer this more neutral meaning of "emergent"
is that it leaves open the question of whether
a property is emergent because it is an explainable
network property, or because it is an unexplainable
nonphysical property. (See Bechtel and Richardson
1993 for a general discussion of these issues.
3. SHOULD WE EXPECT THAT I COULD KNOW WHAT
This question is most pointedly raised in
the context of the inverted spectrum problem,
and I shall address it in that form. To illustrate,
consider the possibility that your color
experiences (color qualia) might be systematically
inverted relative to mine; e. g. where you
see red, I see green, and so on. Noting that
there could be systematic behavioral compensation
that would cover experiential differences,
skeptics have urged that even looking inside
would be unavailing . Allegedly, no conceivable
test could ever reveal similarity or inversion
in our color experiences. The lesson we are
invited to draw is that consciousness is
intractable scientifically because inter-subjective
comparisons are impossible. Some philosophers
think that this is not merely a problem about
what we can and cannot know, but evidence
that consciousness is a metaphysically different
kind of thing from brain activity. In addressing
this issue, I shall make one assumption:
that conscious experiences are in some systematic
causal connection to neuronal activity. That
is, they are not utterly independent of the
causal events in the brain.
To deny the assumption
is to slide into a version of dualism known
as "psycho-physical parallelism",
meaning that mental events and physical events
are completely independent of each other
causally, and just happen, amazingly enough,
to run in parallel "streams". Normal
human color vision is known to depend three
cone types, each of which is tuned to respond
to light of particular wavelengths. Cone
inputs are coded by color-opponent cells
in the retina and lateral geniculate nucleus,
and project to double-opponent cells in the
parvocellular-blob pathways of the cortex.
Cells in cortical area V4 appear to code
for color regardless of wavelength composition
of the light from the stimulus, and appear
to subserve the perceptual phenomenon known
as color constancy. Lesions to the cortical
area known as V4 result in achromatopsia
(loss of all color perception), in humans
and monkeys. Also relevant to behavioral
determinations of differences in experience
is the fact that the relations between hue,
chroma (saturation) and value (lightness)
define an asymmetric solid (Munsell color
quality space). This implies that radical
differences in perception should be detectable
behaviorally, given suitable tests. That
is, "A is more similar to B than to
C" relations between colors are defined
over the Munsell quality space, and if there
is red/green inversion, the similarity relations
to yellow, orange, pink etc. will not remain
Given the progress to
date, it seems likely that the basic neurobiological
story for color processing can be unraveled.
For similar reasons, it looks likely that
the basic story for touch discrimination
and its mechanisms in the somatosensory thalamus
and cortex can also be unraveled. For example,
it seems evident that if someone lacks "green"
cones, or lacks "red/green opponent
cells, or lacks a V4, they will not experience
the visual perception of green. Comparable
circuitry and comparable behavioral discriminations
seem to be presumptive of comparable experiences;
that is, comparable qualia. (Clark 1993)
The skeptic, however, insists that no data
-- not behavior, not anatomy, not physiology
-- could ever reveal qualia inversion. Incidentally,
what is at issue here is not that minor differences
in such things as hue or brightness might
go undetected, but that even huge differences,
such as red/green inversions or brightness/dullness
inversion, might be in principle absolutely
undetectable. To approach this matter somewhat
indirectly, let us first consider a vivid
example where it is evident that a perceptual
inversion is likely detectable, namely, inverted
"shape" qualia. Could Alphie have
"straight qualia" whenever Betty
has "curved qualia" (and vice versa)
and the difference be absolutely undetectable?
In this example, because two modalities --
vision and touch -- can access the external
property, it seems easier to agree that together,
behavioral data and wiring data permit us
to make a reasonable determination of similarity
and differences. That is, the problem is
not essentially less tractable than determining
whether two people digest food in the same
way or wherther two cats in free fall right
themselves in the same way.
Much the same is usually
conceded for pleasure/pain inversion, and
within vision, of near/far inversion in stereopsis.
Random dot streograms are already a very
reliable determinant of (a) whether a subject
has stereopsis at all, and (b) whether there
is an inversion between two subjects. If
we factor in data from "near/far"
cells in V1, then insisting upon absolute
undetectability begins to look unreasonable.
It seems a bit like insisting that it is
absolutely undetectable whether the universe
was created five minutes ago, complete with
all its geological records, its fossil records,
history books, and my memories etc.
Skepticism carried to
that extreme just ceases to be scientifically
intersting, and becomes philosophical in
the pejorative sense of the term. In the
case of "shape inversion", the
skeptic can remain a skeptic by going one
of two ways, neither of which helps his sweeping
anti-reductionist defense: (1) no qualia
-- not shape, not temperature, not pain not
any qualia-- can be compared across subjects,
even to a degree of probability. They are
one and all, absolutely incomparable. For
all I could ever know, you might experience
the color red when I experience pain. (2)
The neurobiology of shape qualia (rough/smooth,
etc.) can be compared, and perhaps even the
neurobiology of stereopsis, but color vision
is different. The first appears to depend
only on an anti-reductionist resolve, without
any independent argument. In that case, we
really are looking at a circular argument.
The only escape from the circle is to fall
into the embrace of dualism -- and worse,
of the deeply implausible psycho-physical
parallelism rendition of that already implausible
doctrine. The second makes a major concession
so far as qualia in general are concerned.
Having conceded that some qualia are scientifically
approachable, the skeptic no longer shields
subjectivity as such, but only subjectivity
for certain classes of experience, namely
color vision. This looks far less powerful
that the original position, and it starts
the skeptic down a slippery slope. For having
made this concession, it now becomes easier
for the reductionist to push hard on the
point that comparisons in receptor properties,
wiring properties, connectivity to motor
control, and so forth, will augment -- as
it already does -- behavioral data, and allow
us to compare capacities across individuals.
And similar arguments can be made for other
single modality experiences: stereopsis,
sound, pain, temperature, feeling nauseous,
feeling dizzy etc. That is, as long as awareness
of color has a causal structure in the brain
-- as long as it is not a property of soul-stuff
utterly detached from all causal interaction
with the brain -- data from psychology (e.
g. the color-hue relationships ) and neuroscience
(tuning curves for the three cone types in
the retina, wiring from the retina to cortex
and intracortically) predicts that big differences
in color perception will correlate with big
differences in wiring and in neuronal activity.
In the context of a more detailed knowledge
of the brain in general, rough comparisons
between individuals ought to be achievable,
subject to the usual qualifications unavoidable
in any science. (For a more thorough examination
of this matter, see Austen Clark's outstanding
book Sensory Qualities, 1993).
4. SHOULD WE EXPECT EXPLANATIONS OF WHAT
IS GOING ON IN SOMEONE'S MIND, MOMENT BY
The question of how detailed a theory has
to be in order to count yielding an explanation
is not straightforward, and varies with the
motivations for wanting an explanation. The
desire to control a phenomenon, or to predict
exactly what will happen next, may require
more detail that the desire to grasp the
general go of it. Thus we basically do understand
the weather, but because it is a complex
dynamical system with many variables, we
cannot predict exactly where a tornado will
form or where within inches or even kilometers
it will move once formed. On the other hand,
sometimes good intervention in a phenomenon
can be achieved with minimal understanding,
as when lithium salts werefound to bring
manic-depression under control but almost
nothing was understood about how this was
achieved. The complexity of the human nervous
system makes detailed, moment-to-moment prediction
highly unlikely. Additionally, intervention
in the system to obtain the data on the relevant
parameters, perhaps neuron by neuron, would
change the basic conditions and frustrate
the prediction. Certainly at this stage we
have no non-invasive technology at the neuronal
level of resolution to achieve that end.
The same, however, is
true of predicting exactly where Tony Gwynn
will hit a baseball. Measurements to obtain
the data will change the data, and there
are too many variables to compute. As a practical
matter, therefore, thought-by-thought monitoring
looks unlikely. Consequently, I suspect that
determining from his neuronal profile, moment
by moment, whether someone will choose a
Ford Bronco or a Chevy Yukon is not a reasonable
goal for the near future, though for all
one can be sure now, advances in technology
may improve predictions.
As with predicting the weather,
data does narrow the range of possible outcomes,
and together certain general assumptions,
reasonably close predictions are possible.
Predicting such matters as attentional shifts
or coming to a decision may well be possible,
just as one can make a very good guess where
Gwynn will hit if you know Gwynn's batting
history, the strengths and weaknesses of
team in the field, the pitcher's repertoire
and his history in this game, and who is
5. SHOULD WE EXPECT A REDUCTION ROM THE BEHAVIORAL
LEVEL DIRECTLY TO THE NEURONAL LEVEL?
Nervous systems appear to have many levels
of organization, ranging in spatial scale
from molecules such as serotonin, to dendritic
spines, neurons, small networks, large networks,
areas, and systems. Although it remains to
be determined empirically what exactly are
the functionally significant levels, it is
unlikely that explanations of macro effects
such as perceiving motion will be explained
directly in terms of the most micro level.
More likely, high-level network effects will
be the outcome of smaller networks, and those
effects in turn of the participating neurons
and their interconnections, and those in
turn of the properties of protein channels,
neuromodulators and neurotransmitters, and
so forth. One misconception about the reductionist
strategy dubs it as seeking a direct explanatory
bridge between highest level and lowest levels.
This idea of "explanation-in-a-single-bound"
does stretch credulity, but neuroscientists
are not remotely tempted by it. In contrast,
the view I am advocating here prefers to
predict that reductive explanations will
proceed step-wise from highest to lowest,
always agreeing of course that the research
should proceed at all levels simultaneously.
(Churchland and Sejnowski 1992)
III USING IGNORANCE AS PREMISE
Perhaps the most common argument of those
skeptical of neurobiological progress consists
in stressing what we do not know, and using
this as a basis for arguing about what we
cannot know. McGinn, for example, repeatedly
insists that the problem of how the brain
could generate consciousness is "miraculous,
eerie, even faintly comic" (p.
99). Finding the problem difficult, he concludes,
"This is the kind of causal nexus we
are precluded from ever understanding, given
the way we have to form our concepts and
develop our theories." (P. 100). McGinn
is by no means alone here. Fodor too thinks
he can already tell that the question is
unanswerable -- not just now, not just given
what we know so far, from unanswerable ever.
Vendler mocks the ambitions of neuroscience
by saying that it is obvious, from, the nature
of sensation, that our sensing selves "are
in principle beyond what science can explain."
That we are trying to unravel the mystery
is, in Vendler's view, a consequence of the
overweening assumption that there are no
questions science cannot answer. In general,
what substantive conclusions can be drawn
when science has not advanced very far on
a problem? Not much.
One of the basic skills
we teach logic students is how to recognize
and diagnose the range of nonformal fallacies
that can undermine an ostensibly appealing
argument: what it is to beg the question,
what a non sequitur is, and so on. A prominent
item in the fallacy roster is argumentum
ad ignorantiam -- argument from ignorance.
The canonical version of this fallacy uses
ignorance as the key premise from which a
substantive conclusion is drawn. The canonical
version looks like this: We really do not
understand much about a phenomenon P. (Science
is largely ignorant about the nature of P.)
Therefore: we do know that:
(1) P can never be explained or (2) Nothing
science could ever discover would deepen
our understanding of the phernomenon P. or
(3) P can never be explained in terms of
properties of kind S.
In its canonical version,
the argument is obviously a fallacy: none
of the tendered conclusions follow, not even
a little bit. Surrounded with rhetorical
flourish, much brow furrowing and hand-wringing,
however, versions of this argument can hornswoggle
the unwary. From the fact that we do not
know something, nothing very interesting
follows -- we just don't know. Nevertheless,
the temptation to suspect that our ignorance
is telling us something positive, something
deep, something metaphysical or even radical,
is ever-present. Perhaps we like to put our
ignorance in a positive light, supposing
that but for the Profundity of the phenomenon,
we would have knowledge. But there are many
reasons for not knowing, and the specialness
of the phenomenon is, quite regularly, not
the real reason. I am currently ignorant
of what caused an unusual rapping noise in
the woods last night. Can I conclude it must
be something special, something unimaginable,
something.... alien ... other-worldly? Evidently
not. For all I can tell now, it might merely
have been a raccoon gnawing on the compost
bin. Lack of evidence for something is just
that: lack of evidence. It is not positive
evidence for something else, let alone something
of a humdingerish sort. That conclusion is
not very glamorous perhaps, but when ignorance
is a premise, that is about all you can grind
out of it. Now if neuroscience had progressed
as far on the problems of brain function
as molecular biology has progressed on transmission
of hereditary traits, then of course we would
be in a different position. But it has not.
The only thing you can conclude from the
fact that attention is mysterious, or sensorimotor
integration is mysterious, or that consciousness
is mysterious, is that we do not understand
the mechanisms. Moreover, the mysteriousness
of a problem is not a fact about the problem,
it is not a metaphysical feature of the universe
-- it is an epistemological fact about us.
It is about where we are in current science,
it is about what we can and cannot understand,
it is about what, given the rest of our understanding,
we can and cannot imagine. It is not a property
of the problem itself. It is sometimes assumed
that there can be a valid transition from
"we cannot now explain" to "we
can never explain" , so long as we have
the help of a subsidiary premise, namely,
"I cannot imagine how we could ever
explain..." . But it does not help,
and this transition remains a straight-up
application of argument from ignorance. Adding
"I cannot imagine explaining P"
merely adds a psychological fact about the
speaker, from which again, nothing significant
follows about the nature of the phenomenon
Whether we can or cannot
imagine a phenomenon being explained in a
certain way is a psychological fact about
us, not an objective fact about the nature
of the phenomenon itself. To repeat, it is
an epistemological fact -- about what, given
our current knowledge, we can and cannot
understand. It is not a metaphysical fact
about the nature of the reality of the universe.
Typical of vitalists generally, my high school
biology teacher argued for vitalism thus:
I cannot imagine how you could get living
things out of dead molecules. Out of bits
of proteins, fats, sugars -- how could life
itself emerge? He thought it was obvious
from the sheer mysteriousness of the matter
that it could have no solution in biology
or chemistry. He assumed he could tell that
it would require a Humdinger solution. Typical
of lone survivors, a passenger of a crashed
plane will say: I cannot imagine how I alone
could have survived the crash, when all other
passengers died instantly. Therefore God
must have plucked me from the jaws of death.
Given that neuroscience is still very much
in its early stages, it is actually not a
very interesting fact that someone or other
cannot imagine a certain kind of explanation
of some brain phenomenon.
Aristotle could not imagine
how a complex organism could come from a
fertilized egg. That of course was a fact
about Aristotle, not a fact about embryogenesis.
Given the early days of science (500 BC),
it is no surprise that he could not imagine
what it took many scientists hundreds of
years to discover. I cannot imagine how ravens
can solve a multi-step problem in one trial,
or how temporal integration is achieved,
or how thermoregulation is managed. But this
is a (not very interesting) psychological
fact about me. One could, of course, use
various rhetorical devices to make it seem
like an interesting fact about me, perhaps
by emphasizing that it is a really really
hard problem, but if we are going to be sensible
about this, it is clear that my inability
to imagine how thermoregulation works is
au fond, pretty boring. The "I-cannot-imagine"
gambit suffers in another way. Being able
to imagine an explanation for P is a highly
open-ended and under-specified business.
Given the poverty of delimiting conditions
of the operation, you can pretty much rig
the conclusion to go whichever way your heart
desires. Logically, however, that flexibility
is the kiss of death. Suppose someone claims
that she can imagine the mechanisms for sensorimotor
integration in the human brain but cannot
imagine the mechanisms for consciousness.
What exactly does this difference amount
to? Can she imagine the former in detail?
No, because the details are not known.
What is it, precisely,
that she can imagine? Suppose she answers
that in a very general way she imagines that
sensory neurons interact with interneurons
that interact with motor neurons, and via
these interactions, sensorimotor integration
is achieved. Now if that is all "being
able to imagine" takes, one might as
well say one can imagine the mechanisms underlying
consciousness. Thus: "The interneurons
do it." The point is this: if you want
to contrast being able to imagine brain mechanisms
for attention, short term memory, planning
etc., with being unable to imagine mechanisms
for consciousness, you have to do more that
say you can imagine neurons doing one but
cannot imagine neurons doing the other. Otherwise
one simply begs the question. To fill out
the point, consider several telling examples
from the history of science.
Before the turn of the
twentieth century, people thought that the
problem of the precession of the perihelion
of Mercury was essentially trivial. It was
annoying, but ultimately, it would sort itself
out as more data came in. With the advantage
of hindsight, we can see that assessing this
as an easy problem was quite wrong -- it
took the Einsteinian revolution in physics
to solve the problem of the precession of
the perihelion of Mercury. By contrast, a
really hard problem was thought to be the
composition of the stars. How could a sample
ever be obtained? With the advent of spectral
analysis, that turned out to be a readily
solvable problem. When heated, the elements
turn out to have a kind of fingerprint, easily
seen when light emitted from a source is
passed through a prism. Consider now a biological
example. Before 1953, many people believed,
on rather good grounds actually, that in
order to address the copying problem (transmission
of traits from parents to offspring), you
would first have to solve the problem of
how proteins fold. The former was deemed
a much harder problem than the latter, and
many scientists believed it was foolhardy
to attack the copying problem directly.
As we all know now, the
basic answer to the copying problem lay in
the base-pairing of DNA, and it was solved
first. Humbling it is to realize that the
problem of protein folding (secondary and
tertiary) is still not solved. That, given
the lot we now know, does seem to be a hard
problem. What is the point of these stories?
They reinforce the message of the argument
from ignorance: from the vantage point of
ignorance, it is often very difficult to
tell which problem is harder, which will
fall first, what problem will turn out to
be more tractable than some other. Consequently
our judgments about relative difficulty or
ultimate tractability should be appropriately
qualified and tentative.
Guesswork has a useful
place, of course, but let's distinguish between
blind guesswork and educated guesswork, and
between guesswork and confirmed fact. The
philosophical lesson I learned from my biology
teacher is this: when not much is known about
a topic, don't take terribly seriously someone
else's heartfelt conviction about what problems
are scientifically tractable. Learn the science,
do the science, and see what happens. When
McGinn says we have been working on the problem
of consciousness for a long time, he seems
surprisingly innocent of what it takes to
even begin to study the brain basis for the
phenomenon. Whereas groundbreaking discoveries
in astronomy could be made with a crude telescope,
as when Galileo discovered the moons of Jupiter,
Figuring out how neurons do what they do
requires high-level technology. And that,
needless to say, depends on immense infrastructural
science; on cell biology, advanced physics
and twentieth century chemistry. It requires
sophisticated modern notions like molecule
and protein, and modern tools like the light
microscope and the electron microscope.
Most importantly, making
progress in how brains work depended on understanding
electricity. This is because what makes brain
cells special is their capacity to signal
one another by causing micro changes in each
others' electrical state. Living as we do
in an electrical world, it is sobering to
recall that as late as 1800, electricity
was typically considered deeply mysterious
and quite possibly occult. Only after discoveries
by Ampere and Faraday at the dawn of the
19th century was electricity clearly understood
to be a physical phenomenon, behaving according
to well-defined laws, and capable of being
harnessed for practical purposes. Finally,
consider Vendler's admonition: we cannot
expect to solve all problems, answer all
questions. Let's agree with him -- some questions
may never be answered. What follows from
that so far as this problem -- the problem
of the neurobiology of consciousness -- is
concerned? Absolutely nothing. Suppose this
problem is really very hard. What follows
from that? Nothing. We cannot tell, from
the vantage point of ignorance, that a given
problem cannot be solved. Problems do not
come with the information "I am unsolvable"
pinned to their shirts.
Given the current state of cognitive science
and neuroscience, it is reasonable to expect
we shall understand more about the nature
of consciousness as more is revealed about
how in general the brain works (Llinas and
Pare 1996). In particular, with increased
understanding of the nature of sensory systems,
attentional mechanisms, short term memory,
working memory, dreaming, imagery, planning
and so forth, probably the neurobiology of
consciousness will come into focus (Crick
1993; Paul M. Churchland 1994, 1996). Clearly,
we need to understand in detail the role
of back projections (re-entrant signaling)
in such phenomena as filling-in and complex
pattern recognition (Edelman 1992).
We need to understand
the meaning of the physiological data on
binocular rivalry (Leopold and Logothetis
1996), as well as the significance of neuropsychological
phenomena such as illusions of body-image
and confabulation (Gazzaniga and LeDoux 1978;
Ramachandran et al. 1996). Undoubtedly there
will be many surprises along the way, and
some discoveries may cause us to reconceptualize
the very problem itself. Though each the
of the skeptical arguments considered here
command powerful intuitive appealing and
for that reason alone must be taken seriously,
none commands significant credence once examined
and analyzed. That they are flawed does not,
of course, show that neuroscience will in
fact be successful in expanding our understanding
of consciousness, only that the skeptics
conclusions regarding the mere possibility
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Patricia Smith Churchland
Born: July 16, 1943
Permanent Resident U.S.A.
Married: Paul M. Churchland, Ph. D.
Children: Mark M. Churchland (1972)
Anne K. Churchland (1974)
Address: Philosophy Department 0119
University of California San Diego
La Jolla CA 92093
Fields Of Specialization
Philosophy of Neuroscience
Philosophy of Mind
Philosophy of Science
University of British Columbia, 1961-65,
University of Pittsburgh, 1965-66, M.A.
Oxford University, 1966-69, B. Phil.
Assistant Professor, University of Manitoba,
Associate Professor, University of Manitoba,
Visiting Member, Institute for Advanced Study,
Full Professor, University of Manitoba, 1983-84
Full Professor, University of California,
San Diego, 1984 -
Academic Awards And Grants
Woodrow Wilson Fellow, 1965-66
British Council Fellow, 1966-67
Canada Council Fellow, 1967-69
Canada Council Research Grant, 1975-76
Woodrow Wilson Faculty Development Award,
Social Sciences and Humanities Research Council
Leave Fellowship, 1979-80
Social Sciences and Humanities Research Council
Research (SSHRC) Grant, 1979-80.
University of Manitoba SSHRC Research Grant,
University of Manitoba SSHRC Research Grant,
Philosopher's Annual (one of ten best articles)
SSHRC Research Time Stipend, 1981-83
Rh Institute Research Grant for Outstanding
Contributions to Inter-Disciplinary Research
and Scholarship, 1981
SSHRC Department of International Relations
Soc. Sc. & Hum. Research Council Leave
Soc. Sc. & Hum. Research Council Research
UCSD Senate Research Grant 1984-84
UCSD Senate Research Grant 1985-86
UCSD Senate Research Grant 1986-87
USCD Senate Research Grant 1987-88
National Science Foundation (NSF) Research
James S. McDonnell Research Grant 1988-89
Faculty Research Lecture Award (UCSD) 1988
Chancellor's Associate Award (UCSD) 1988
James S. McDonnell Research Grant 1989-90
UCSD Senate Research Grant 1990-91
Adjunct Professor, Salk Institute, 1989-
UC President's Fellowship in the Humanities
MacArthur Foundation Research Fellow, 1991-96
Elected, Academy of Humanism, 1993
Honorary Doctor of Letters, University of
Neurophilosophy: Toward a Unified Science
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The Computational Brain. (1992) P. S. Churchland and
T.J. Sejnowski. Cambridge, Mass.: The
_____Italian Translantion, Il Cervello Computazionale
(1995) il Mulino: Bologna
Neurophilosophy and Alzheimer's Disease. (1992) Ed. by Y. Christen and
P. S. Churchland. Berlin:
The Mind-Brain Continuum (1996). Ed. R. R. Llinas and
P. S. Churchland. MIT Press.
On the Contrary : Critical Essays 1987-1997.
(1998 ). Paul M. Churchland and Patricia
S. Churchland. MIT
‘The Mind-brain problem’ (with Paul M. Churchland).
In: The Brain of Homo Sapiens. Vol. 4 of Frontiere della
Biologica (Istitutio della Enciclopedia Italiana
Trecanni). (French and English edition also
forthcoming.) Ed. By E.
Bizzi, P. Calissano and V. Volterra.
‘The Brain-built self’. Ars Electronica.
‘Computation and the brain’ (with Rick Grush)(1998)
. In: The MIT Encyclopedia of Cognitive Science. MIT
‘What can we expect from a theory of consciousness?”
(1998) In: Advances in neurology: Vol 77.
Consciousness: At the Frontiers of Neuroscience. Eds. H. Jasper, L. Descarries, V. Castellucci,
Philadeplphia: Lippincott-Raven. 19-32.
Recent work on consciousness: Philosophical,
Empirical andTheoretical . Seminars in Neurology. 17: 101-108.
(With Paul M. Churchland).
Reprinted inCognitive Studies: Bulletin of
the Japanese Cognitive Science Society..
'Brainshy: Nonneural theories of conscious
experience.' (1997). In: Consciousness -- Papers for Tucson II. Edited
by S. Hameroff, J. Laukes et al.
'Toward a neurobiology of the mind."
(1996) In: The Mind-Brain Continuum. Ed. by Llinas and Churchland.
Cambridge, MA: MIT Press. 281-303.
'The Hornswoggle Problem' (1996) Journal of Consciousness Studies. 3:402-8.
'Machine Intelligence'. (1995)
P. M. Churchland and P. S. Churchland.
Aniversary volume of Scientific American.
'Gaps in Penrose's Toiling'. (1995)
R. Grush and P. S. Churchland. Journal of Consciousness Studies.
(1995) In: Conscious Experience. Ed. by T. Metzinger. Berlin: Schoningh-Verlag.
'Feeling Reasons', (1995). In: Decision-Making and the Brain. Ed. by A. R. Damasio, H. Damasio and
Christen. Berlin: Springer-Verlag.
(1995) Reprinted in Mind and Brain in the 21st Century. Edited by C. Maar. Berlin:
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P. S. Churchland Ed. by R. N.
McCauley. Oxford: Blackwells.
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Ed, by T.
Metzinger. Berlin: Schoningh Verlag.
'Intertheoretic-reductionism: A neuroscientist's
field-guide.' (reprinted from 1991). In:
Nature's Imagination. Ed. by
John Cornwell. Oxford: Oxford University
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is Wrong'. (1994).
P.S. Churchland and V.
S. Ramachandran. In Dennett and
His Critics. Ed. Bo Dahlbom.
Reprinted in Vancouver Studies
in Cognitive Science. (1994).
Ed. S. Davis and K. Akins. Oxford:
'A Critique of Pure Vision'. (1994).
P. S. Churchland, V. S. Ramachandran, and
T. J. Sejnowski. In Large-scale
Neuronal Theories of the Brain. Ed.
C. Koch. Cambridge, Mass.: MIT
'Consciousness and the
and Theoretical Issues'. (1994).
I. Farber and P. S.
Churchland In The Cognitive Neurosciences.
Ed. Michael Gazzaniga. MIT Press.
'Could a Machine Think?' Paul Churchland
and Patricia Churchland. Reprinted in Thinking
Virtual Persons. Ed. E. Dietrich Academic
'Inter-theoretic reduction: A neuroscientist's
field guide' (reprinting) Paul Churchland
and Patricia Churchland. in:
The Mind-Body Problem: A guide to the current
debate. Ed. by R. Warner and T Szubka. Oxford:
'Can Neuroscience Teach us Anything About
Consciousness?' P. S. Churchland (1993) Presidential
Pacific Division of the American Philosophical
Association. In Proceedings of the APA.
'Introduction: Neurophilosophy and
Alzheimer's Disease'. (1992).
Introduction to Neurophilosophy and
Alzheimer's Disease. Ed. Y. Christen
and P. S. Churchland.
'Aristotle on Memory'.
(1992). Patricia Smith Churchland and
Georgios Anagnostopoulos. For The
Encyclopedia of Learning and Memory.
General Editor, L. Squire.
'Silicon brains'. (1992). T.
J. Sejnowski and P. S. Churchland.
Byte, October, 1992.
'Computation in the Age of Neuroscience'.
(1992). T. J. Sejnowski
and P. S. Churchland . The New
Computation. Ed. D. Hillis. MIT Press.
'Intertheoretic reduction: A neuroscientist's
field guide'. (1991). Paul M.
and Patricia S. Churchland. Seminars
the Neurosciences. 2: 249 - 256.
_____Reprinted in Neurophilosophy and
Alzheimer's Disease (1991). Ed. Y.
Christen and P. S. Churchland.
_____Reprinted in Modelos Cognitivos de la
Mente: Investiga-cion Interdicplinaria
en Ciencia Cognitiva.
(1992) Ed. J. L. Diaz and E. Villanueva.
Universidad Nacional Autonoma de Mexico
'Our Brains, Ourselves: Reflections
on Neuroethical Questions'. (1991).
In Bioscience and Society. Ed. D.J.
Roy, B. E. Wynne, and R. W. Old. Wiley
'Is neuroscience relevant to philosophy?'.
(1990). In Canadian Philosophers.
Ed. D. Copp. University of
_____Reprinted as 'Les Neurosciences
Concernent-Elles La Philosophy?'
(1991). In: Philosophie De L'Esprit Et
Sciences Du Cerveau. Ed. Jean-Noel Missa.
Librarie Philosophique J. Vrin. (Paris)
'What is computational neuroscience?'
(1990). With T.J. Sejnowski and C.
Koch. In Computational
Neuroscience. Ed. E. Schwartz.
Cambridge, Mass.: MIT Press.
'Could a machine think? Recent arguments
and new prospects'. (1990).
With P.M. Churchland. Scientific
_____Reprinted in The Intentionality of Machines.
Ed. E. Dietrich. Oxford: Blackwells.
'Neural representation and neural computation'.
(1989). With T.J. Sejnowski.
In Biological Computation and
Mental Representation. Ed. L.
Nadel. Cambridge, Mass.: MIT Press,
_____Reprinted in Philosophy of mind and
action theory (1991). Ed. James
Tomberlin, Ridgeview Publishing:
_____Reprinted in From Reading to Neurons.
(1989). Ed. A. Galaburda. Cambridge,Mass.:
'Brain and cognition'. (1989).
With T. J. Sejnowski. Foundations of
Cognitive Science. Ed. M. Posner.
Cambridge, Mass.: MIT Press.
'From Descartes to neural networks'.
(1989). Scientific American 261: 118.
'Reductionism and the neurobiological basis
of consciousness'. (1988). In
Consciousness in Contemporary
Science. Ed. A. M. Marcel and E. Bisiach.
Oxford: Oxford University Press, 273-304.
'The significance of neuroscience
for philosophy'. (1988).
Trends In Neurosciences, 11: 304-307.
'Replies to Corballis and to Bishop'.
(1988). Biology and Philosophy 3, 393-402.
'Computational neuroscience'. (1988).
T.J. Sejnowski, C. Koch, and P. S.
_____Reprinted in Encyclopedia of Neuroscience
_____Reprinted in Connectionist Modeling
and Brain Function: The Developing
Interface. C. R. Olson.
Cambridge, Mass.: MIT Press.
'Perspectives on cognitive neuroscience'.
(1988). P. S. Churchland and T. J.
Sejnowski. Science 242:741-745.
_____Reprinted in From Molecules To Minds.
(1990). Ed. Katrina Kelner, American
Association for the
Advancement of Science.
_____Reprinted in Perspectives on Cognitive
Neuroscience. (1991). Ed. Lister
and Weingartner. Oxford:
Oxford University Press. 3-23.
'Epistemology in the age of neuroscience'.
(1987). The Journal of Philosophy,
'Replies to Commentaries on Neurophilosophy'.
(1986). Inquiry, 29, 241-272.
(This issue of Inquiry is devoted
to a symposium on Neurophilosophy.)
'Psychology and the study of the mind-brain:
Reply to Carr, Brown, and Sudevan'. (1984).
'Stalking the wild epistemic engine'.
(1983). With P. M. Churchland.
Nous, 17, 5-18. (Symposium for
American Philosophical Association, Western
Division, Chicago, March 1983.)
_____Reprinted in Mind and Cognition.
(1990). Ed. W. Lycan. Oxford:
'Consciousness: The transmutation of a concept'.
(1983). Pacific Philosophical Quarterly
'Content: Semantic and information-theoretic'.
(1983). With P. M. Churchland
The Behavioral and Brain
'Is the visual system as smart as it looks?'
(1983). In Proceedings of the Philosophy
of Science Association,
SymposiaVol 2. 541-552.
'Ojemann's data: Provocative
but mysterious'. (1983).
The Behavioral and Brain Sciences 6,
'Dennett's instrumentalism: A
frog at the bottom of the
mug.' (1983). The Behavioral
and Brain Sciences 6,
'Mind-brain reduction: New light
from the philosophy of
science'. (1982). Neuroscience 7, 1041-1047.
'Is determinism self-refuting?' (1981).
Mind 90, 99-101.
'On the alleged backwards referral
of experiences and its
relevance to the mind-body
Philosophy of Science. 165-181.
'How many angels?' (1981). The Behavioral
and Brain Sciences 4, 236.
'Functionalism, qualia and intentionality'.
(1981). With P. M. Churchland.
Philosophical Topics 12, 121-145.
_____Reprinted in Mind, Brain, and
Function. (1982). Ed. R. Shahan and
J. Biro. Norman, OK: University of
'The timing of sensations: Reply to
Libet'. (1981). Philosophy of
'A perspective on mind-brain research'.
(1980) The Journal of Philosophy
_____Reprinted in The Philosopher's Annual.
(1981). Ed. D. L. Boyers, R. Grim and
T. J. Saunders.
Ridgeview California: Ridgeview Publishing
'Language, thought, and information processing'.
(1980). Nous 14, 147-170.
'Neuroscience and psychology: Should the
labor be divided?' (1980). The
Behavioral and Brain Sciences 3,
'Fodor on language learning'. (1978).
Synthese 38, 149-159.
'The virtuosity of the sensory cortex and
the perils of common sense'. (1978).
With P.M. Churchland. The
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Review of Philosophy and the Brain by J.
Z. Young. (1987). Nature
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Review of Mind and Brain, ed. J. Eccles.
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Review of Human Inference: Strategies
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by Richard Nisbett and Lee
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Society for Neuroscience
Philosophy of Science Association
American Philosophical Association
Society for Philosophy and Psychology
President, 1984-85, Society for Philosophy
Board of Governors, Philosophy of Science
Program Committee 1984, Philosophy of Science
Board of Governors, Canadian
Philosophical Association 1978-1980.
President, American Philosophical
Association - Pacific Division.
Chair of Executive Board, Institute for Neural
Computation (UCSD) 1994 -- __
Cognitive Science 1986-88
Journal of Cognitive Neuroscience
Visions; Channel 4, London January
Nightwatch; (Charlie Rose) CBS, February
Bill Moyers; April, 1990
KCET, Los Angeles (Discovery Channel)
; November 1990
RTBF, Charleroi (Belgium) Odyssey of
the Spirit (first and sixth broadcast.) Recorded
April 1991, for
PBS - New York: AI and Neural Nets
Channel 4 London - The Mind/Brain (April
CNN - Changing our Minds (series on
environmental issues) (1994) repeated
on TBS (1994)
Discovery Channel -- The
Brain: Our Universe Within
PBS -- The Human Quest (1995)