What is the Explanatory
Association for the Scientific Study of
Berlin June 8 2009
What is the Gap? Title 1
The Problem is that we are All
The „explanatory gap‟ is
supposed to be some
problem left after we have
done the scientific work on
I say there is no real problem
here. We only think there is
because we can‟t stop
ourselves thinking as
So the problem isn‟t some
business left unfinished by
normal science, but simply
that we aren‟t scientific
What is the Gap? All dualists 2
1 The explanatory gap
2 The philosophical stories
3 The gap diagnosed
4 What causes intuitive dualism?
(a) Ingrained culture
(b) Natural-born dualism
(c) The antipathetic fallacy
(d) Aspirations of transparency
(e) Can‟t merge the files
What is the Gap? Plan 3
Mind-Brain Scientific Identities
Modern materialists say that conscious
states are (realized by, supervene on)
brain states, just as water is H2O or heat is
We have an everyday kind (pain, colour
vision, water, heat) and it turns out to be
the same as some scientific kind (C-fibres,
V-8 activity, H2O, molecular motion).
What is the Gap? 1 Explanatory gap 4
Joe Levine pointed out that
even so the mind-brain
cases strike us quite
differently from the
Even after we are shown all
the evidence, we go on
asking „why are C-fibres
felt as pains (or as
anything at all)?‟—but we
don‟t go on asking „why is
What is the Gap? 1 Explanatory gap 5
Derivations from Physics
Most philosophers think that Levine‟s explanatory
contrast arises because we can derive
water/heat etc facts from the physical facts, in a
way we can‟t derive pain/seeing red etc facts.
For example, enough knowledge of atomic
chemistry allows you to see that H2O must be
water, but no knowledge of brain processes will
allow you to see that C-fibres must feel like pain.
What is the Gap? 2 Philosophical stories 6
Moreover, most philosophers hold that this
contrast is due to the differing ways we think
about physical (water, heat) and conscious
(pain, seeing red) kinds.
In the former case we pick out the kinds
descriptively, as „the liquid which is
odourless/colourless/etc . . .‟, „the quantity that
co-varies with pressure, . . .‟, etc.
But in the latter case we think of the kinds more
directly, in terms of what they feel like (imagine
having a pain or seeing something red).
What is the Gap? 2 Philosophical stories 7
Jackson and Chalmers drew
our attention to this
special way of thinking
about conscious states
and to how they meant
that no amount of
physical knowledge will
allow you to infer
phenomenal facts so
conceived from the
What is the Gap? 2 Philosophical stories 8
Underivability and the Gap
Jackson and Chalmers tried to argue from this
underivability to the falsity of materialism about
But even philosophers who don‟t think that this
works as an argument against materialism still
think that the underivability is the reason we
have the feeling of an explanatory gap.
What is the Gap? 2 Philosophical stories 9
Underivable ≠ Unexplained
The feeling of a gap may well have something to do with
phenomenal concepts, as we‟ll see. But it is unlikely
lack of derivability per se is the issue.
For one thing, there seem to be plenty of other cases
where we can‟t derive identities from the physical facts,
yet don‟t feel explanatorily challenged.
For example, when scientists first concluded that water =
H2O, it wasn‟t because they could derive odourlessness,
colourlessness, etc from atomic structure—they certainly
couldn‟t—but simply because they knew that water and
H2O were found in the same places at the same time.
Yet this didn‟t leave them puzzled about why water =
What is the Gap? 2 Philosophical stories 10
Nothing left Unexplained
Anyway, what exactly is supposed
to be left unexplained when I
believe an identity that I can‟t
derive from the physical facts?
„Why a = b?‟ But identities need
no explanation. (Cf Mark
Twain = Samuel Clemens.)
„Why pains, say, have certain
causes and effects?‟ But that
can be explained, given the
„Why I should believe pain is C-
fibres firings?‟ But that too can
be explained, by reference to
the correlational evidence.
What is the Gap? 2 Philosophical stories 11
The reason we feel there is an
explanatory gap is simply that
we can‟t help thinking of the
mind-brain relation in dualist
Even after we are shown all the
evidence, and accept that mind
and brain are fully correlated,
we go on thinking of conscious
feelings as something extra to
brain processes, some further
part of reality that is additional
to the brain.
What is the Gap? 3 Gap diagnosed 12
Obvious Questions, Given Dualism
Insofar as we succumb to these dualist
intuitions, it is of course unsurprising that
we should think there remains something
to be explained.
Why do certain physical processes (but
presumably not others) give rise to extra
Why do they give rise to these feelings
rather than others?
What is the Gap? 3 Gap diagnosed 13
Look at How we Talk
Some of you may be surprised to learn that you
are closet dualists. But think of the following
Certain brain processes 'give rise to„, or 'generate„,
or 'yield„, or 'cause„, or 'are correlated with'
All these phrases presuppose dualism.
Fire may give rise to/generate/yield/cause/
correlate with . . . smoke. But H2O doesn't give
rise to/generate/yield/cause/correlate with . . .
water. It is water.
What is the Gap? 3 Gap diagnosed 14
Philosophical zombies strike us all as
intuitively possible—beings physically just
like us but with no feelings.
But they shouldn‟t if we were clear-headed
materialists. How could there be a brain
with C-fibres firing but no pain?
That would be like thinking it is possible to
have Samuel Clemens without Mark
What is the Gap? 3 Gap diagnosed 15
OK—the analogy is not perfect—in the Samuel Clemens
case there is a sense he might indeed not have been
Mark Twain—he mightn‟t have written „Tom Sawyer‟
etc—that is, he mightn‟t have satisfied the descriptions
we associate with the concept „Mark Twain‟.
But in the mind-brain case we don‟t think of pain in terms of
descriptions, so we can‟t be having any analogous
descriptive thought when we think that C-fibre firings
might not have been pains.
So the only explanation of why we think zombies are
possible is that we think of the pains as distinct from the
C-fibres, and therefore as possibly dissociable from
them, even if perfectly correlated in the actual world.
What is the Gap? 3 Gap diagnosed 16
Good Theories and Bad Intuitions
Unlike Kripke, I don‟t think this is
a big problem for physicalism.
There are plenty of other cases
where we find it difficult
intuitively to accept what
theoretically we know to be
(The earth moves, space is non-
Euclidean, there is no moving
„now‟, the macroscopic
universe splits with every
quantum interaction, my status
is lower than I think it is, . . .)
What is the Gap? 3 Gap diagnosed 17
We simply need to recognize that
our thinking is split.
At an intuitive level, we can‟t help
feeling that the mind is
separate from the brain—and
so intuitively feel an
„explanatory gap‟—why does
the brain give rise to the extra
But at a theoretical level we
should insist that there is just
one thing there—the pains are
the C-fibres firing—and so no
remaining need to explain why
that thing is itself.
What is the Gap? 3 Gap diagnosed 18
Why are we all in the grip of an intuition of distinctness?
One possibility is that this is simply how we are brought up
to think. Our culture has long been dualist, and even
after exposure to science we can‟t help slipping back into
the traditional dualist perspective.
Maybe. But this implies that, if our culture were to embrace
mind-brain materialism, dualist intuitions will dissolve.
Some may be happy with this implication. (Stephen Yablo:
„Am I the only one who feels the intuition of zombies to
be vulnerable in this way?‟)
But I suspect that there is something more structural
pushing us towards dualism, something that won‟t be
removed just by a simple change of culture.
What is the Gap? 4a Culture 19
Paul Bloom thinks there is
indeed a more structural
reason for our persistent
We have different mental
modules for thinking
about intelligent agents
(„theory of mind‟) and
about physical objects
Because of this, we treat
items as either mental or
physical but not both.
What is the Gap? 4b Natural dualists 20
This offers a plausible account of why
we find it so easy to think of
persons switching bodies, as in
many fables and fictions.
But it doesn‟t look like the whole story
about mind-brain dualism.
(a) We have different modules for
thinking about organisms and
physical objects, yet don‟t
intuitively resist the idea that
animal bodies are just physical.
(b) We use theory of mind to think
about all intentional states, not
just conscious feelings, yet don‟t
intuitively resist the idea that non-
conscious intentional states
(aims, standing beliefs) are just
What is the Gap? 4a Natural dualists 21
The Antipathetic Fallacy
For many years I ascribed the
intuition of dualist distinctness
to what I called the
„antipathetic fallacy‟ (cf
Ruskin‟s „pathetic fallacy‟).
Consider what happens when we
entertain an identity like pain =
phenomenally on the l.h.s.
Since we imagine the pain on the
l.h.s., but not the right, we are
inclined to conclude that the
r.h.s. „leaves out‟ the pain, and
only talks about its physical
What is the Gap? 4c Antipathetic fallacy 22
The Antipathetic Fallacy
This is of course a fallacy—that we don‟t activate the pain
on the r.h.s. doesn‟t mean we don‟t refer to it. But it is a
very seductive fallacy. (Cf McGinn: „How can
technicolour phenomenology arise from soggy grey
But again it doesn‟t look as if this can be the whole story.
Consider a claim like „pain = what happened in the
dentist yesterday‟. Even if we don‟t imagine the pain on
the r.h.s., we don‟t here automatically feel the r.h.s. only
talks about the accompaniments of pain, rather than the
feeling itself (Pär Sundström).
It looks as if it is physical concepts on the r.h.s. that makes
us unhappy about the identity, not just non-phenomenal
What is the Gap? 4c Antipathetic fallacy 23
Aspirations of Transparency
Consider this line of thought:
“When we think of conscious states phenomenally, in terms
of what they are like, we are in such direct contact with
them that all their essential properties should be
transparent to us. But such phenomenal thinking does
not reveal conscious states to be physical. So they can‟t
Some philosophers are prepared to defend this as a
serious argument. But that‟s not the issue here, so
much as whether this line of thought accounts for our
persistent dualist intuitions.
Maybe that is part of it. But it‟s not clear that it will have
much influence on people who have not reflected at
length on the mind-body issue.
What is the Gap? 4d Aspirations transparency 24
Merging the Files
One popular account of what
happens when we accept an
identity claim a=b is that we
„merge the files‟.
Where we used to have two „files‟
for „a‟ and „b‟ respectively,
each containing a number of
property ascriptions, we
reorganise our mental
architecture so as to end up
with one file containing the
union of these property
What is the Gap? 4e Merging files 25
Merging the Files
Andrew Melnyk has suggested
that the source of our
persistent dualist intuition is
that we can‟t merge files
associated with (imagistic)
phenomenal concepts and
(symbolic) physical concepts.
A nice idea, though one that calls
for further support from
research on the architecture of
What is the Gap? 4e Merging files 26
1 There is no reason why there should be just one
cause for the persistent intuition of
distinctness. Perhaps the different causes
affect different people to different degrees.
2 In any case, it is clear that nearly all of us find
ourselves slipping into dualist thinking when
we are not vigilant.
3 The right response to the explanatory gap is not
to seek out further explanations, but simply to
try harder to be clear-headed materialists.
What is the Gap? 5 Conclusions 27