Reduction and Elimination in Philosophy and the Sciences

No Bridge within Sight
Daniel Wehinger, Innsbruck, Austria
1 The explanatory gap
In his 1983 paper „Materialism and Qualia: The Explanatory
Gap“, Joseph Levine states that there is – the title
already says it – an „explanatory gap“ between the physical
and the mental. Neuroscience has revealed many of
the processes that take place in our brains when we engage
in mental activities. Nevertheless, it is still kind of a
mystery why, say, pain feels the way it does. Having
learned which neural processes give rise to the experience
of pain we are still left asking why and how they do so.
Phenomenal properties, i.e. mental properties with a distinct
phenomenal feel such as being in pain, cannot, so it
seems, be fully explained in physical terms. There is a gap
here. As a result, it seems perfectly conceivable that there
is a world which is physically indiscernible from ours but
lacking any phenomenal properties – the zombie world.
This scenario was forcefully elaborated by David Chalmers
in his “The Conscious Mind” (1996, 94-99). Chalmers
draws explicitly dualist conclusions from the problem of the
explanatory gap and the resulting conceivability of the
zombie world. He claims that in addition to the lots and lots
physical properties such as being six feet tall or weighing
100 pounds there are also some mental properties that
cannot be reduced to the physical, namely the phenomenal
properties introduced above. Therefore, physicalism is
false and a dualism of properties must be assumed. It is
this kind of dualism – property dualism – that I will be dealing
with in the following.
Now, property dualism as such of course doesn’t
close the gap between the mental and the physical. It is
rather a possible conclusion from it. Chalmers, however,
claims that his theory provides him with the tools
necessary for building a bridge. He aims at solving the
“hard problem”: the question of how phenomenal
properties arise from the physical. (Chalmers 1995) This,
according to Chalmers, cannot be done by appeal to
physical facts. “[I]nstead, we have to look for a “Y-factor,”
something additional to the physical facts that will help
explain consciousness. We find such a Y-factor in the
postulation of irreducible psychophysical laws.” (Chalmers
1996, 245) These laws are expected to be general and
simple, i.e. they do not correlate particular types of neural
processes (e.g. the firing of C-fibers) with particular types
of phenomenal properties (e.g. the experience of pain).
They rather have to be conceived of as the fundamental
underlying laws that explain these correlations. A look at
physics tells us that there are only a few fundamental
physical laws. The same can be expected in the case of
consciousness. (Chalmers 1996, 214-215) From the
conceivability of the zombie scenario and other arguments
for dualism, Chalmers concludes that the fundamental
properties these laws invoke cannot be physical. They
rather have to be phenomenal or protophenomenal, i.e.
constituting phenomenal properties. And, just as is the
case with fundamental psychophysical laws, only a few
fundamental phenomenal or protophenomenal properties
are to be expected. (Chalmers 1996, 126-127) By now we
don’t know these fundamental phenomenal or
protophenomenal properties. It is the task of a future
science of consciousness to discover them. A
systematization of the correlations between types of neural
processes and types of phenomenal properties should
guide us there. And after many years of long, hard work
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we shall eventually come to know the fundamental
psychophysical laws and the fundamental phenomenal or
protophenomenal properties that underlie these
correlations. The arisal of consciousness will then be
explained and there will be no mystery left.
2 Why Bennett is not a dualist
In an unpublished draft of August 2006 called “Why I am
Not a Dualist” Karen Bennett criticizes Chalmers view. Her
aim is to establish thereby that the Chalmers-style dualist
is not any better off than the physicalist: It is just as difficult
for her to solve the hard problem as it is for the physicalist.
Taking into account additional criteria such as ontological
economy, the unification of science and so forth, physicalism
wins. (Bennett unpublished, 24)
Bennett puts forward two arguments to support her
view. The first argument focuses on the dualist’s research
strategy. The dualist believes that scientific investigation
will one day reveal how phenomenal properties arise from
the physical. On her way there she uses exactly the same
scientific methods and tools as the physicalist: “Both will
do a lot of serious neuroscience, and both will pay
attention to introspective phenomenology in order to get a
better understanding of ‘phenomenal space’. Both will run
a lab, employ postdocs, and apply for NSF funding.”
(Bennett unpublished, 12) Nevertheless, the dualist is sure
that there will never be a fully satisfying explanation of
phenomenal properties in physical terms. That is, the
dualist assumes that the physicalist cannot in principle
close the explanatory gap. This a priori prediction is
rendered suspect by the fact that the dualist expects
important insights from the scientific investigation of
consciousness: “If the dualist thinks that scientific research
can uncover hitherto unsuspected truths about the
fundamental laws governing psychophysical connections,
why should she not also think that it can uncover hitherto
unsuspected truths about the physical?” (Bennett
unpublished, 13) There’s a real tension here, Bennett
remarks: “The more you can see how research in the
cognitive sciences can tell us how consciousness arises
from the physical, the less secure you should be in your
intuition that no purely physicalist story could ever work.”
(Bennett unpublished, 14)
In her second argument Bennett puts her finger on
the dualist’s claim that her theory allows her to close the
gap between the physical and the mental. Bennett
stresses the fact that “[a]ny dualist who accepts the burden
to systematize the macro-correlations [i.e. the correlations
between certain types of neural processes and certain
types of phenomenal properties] is committed to
something in the ballpark of protophenomenalism.”
(Bennett unpublished, 14) The generation of our everyday
phenomenal properties cannot be explained by appeal to
themselves. Rather, it must be assumed that the few
fundamental properties out of which our conscious life is
woven are quite unlike the phenomenal properties we
know and had therefore better be called protophenomenal
properties. (Bennett unpublished, 15) “Systematizing the
relationship between the physical and the phenomenal”,
Bennett goes on, “is a matter of figuring out what those
elements [or properties] are, and what general laws govern