Psyche 9(07): 'The Inadequacy of Materialistic Explanation' by Mark Bradley
Patrick Wilken
PSYCHE: AN INTERDISCIPLINARY JOURNAL OF RESEARCH ON CONSCIOUSNESS
-----------------------------------------------------------------
THE INADEQUACY OF MATERIALISTIC EXPLANATION:
A REVIEW OF JOSEPH LEVINE'S *PURPLE HAZE*
Mark Bradley
Department of Philosophy
University of Leeds
Leeds LS2 9JT
West Yorkshire
U.K.
Copyright (c) Mark Bradley 2003
PSYCHE, 9(07), February 2003
http://psyche.cs.monash.edu.au/v9/psyche-9-07-bradley.html
KEYWORDS: Consciousness, Qualia, Explanatory Gap, Materialism,
Conceivability, Zombies.
REVIEW OF: Joseph Levine. (2001). *Purple Haze: The Puzzle of
Consciousness.* Oxford: Oxford University Press. 204 pp. ś24.50 hbk.
ISBN 0195132351.
ABSTRACT: Purple Haze: The Puzzle of Consciousness, by Joseph Levine,
is reviewed. The position that Levine takes in the current
philosophical debate about consciousness is identified and the general
approach of the essay outlined. I focus on two of the more important
issues in the book - the conceivability argument against materialism,
and the explanatory gap argument against dualism - and argue that
Levine's argument against the former is unconvincing and his diagnosis
of the source of the latter leads him into problems. I suggest a more
promising route.
One of the many problems which the existence of phenomenal consciousness
poses is the task of explaining just how it arises (if it in fact does)
from the biological and thus physical/functional systems from which we
are composed. The idea that there is an epistemic divide between the two
kinds of phenomena was first discussed by Levine in the early eighties
(Levine, 1983) and is now one of the central issues in the philosophy of
mind. Here, in his first monograph, he presents, develops, and defends
this impervious puzzle in a succinct, thoroughgoing, yet comprehensive
survey of the field of which it is part, illustrating convincingly why
the mind-body problem remains just that.
Levine takes a middle ground position between materialism and dualism,
holding that mental properties are realised by physical properties,
whilst acknowledging the fact that we have no clear idea of how this is
so. The aim of the essay is not to provide a positive solution to the
problem, but to show just why it is a problem, why materialist theories
of phenomenal consciousness are inadequate, while defending materialism
from anti-materialist arguments. He covers a lot of ground, discussing
such wide ranging views as functionalism, panpsychism,
representationalism, higher order theory, property dualism, and
eliminativism (each chapter taking its title from the lyric of a Jimi
Hendrix song). The first task is to give an account of materialism,
which he defines negatively as the thesis that only non- mental
properties are instantiated in a basic way, all mental properties being
realised by the instantiation of these basic ones. This would, ofcourse,
be vacuous without an account of what it is for a property to be mental,
so Levine offers the following fairly standard categories: those
properties which are intentional or are directed towards the world (and
which can be subject to intelligent manipulation), and those which are
phenomenally conscious (are "bits of awareness" or qualia). The
motivation for this materialist approach is the commonplace view that
mental properties interact causally with physical properties and vice
versa, and so if mental properties are part of the causal order, they
must themselves be or be realised by physical properties. This vague
ontological picture doesn't really set Levine apart from most of his
contemporaries, it is only when the question of explanatory adequacy is
considered that his views become interesting. He claims that "while we
seem to have some idea how physical objects, or systems, obeying
physical laws, could instantiate rational and intentional properties, we
have no idea. how a physical object could instantiate a subject of
experience, enjoying, not merely instantiating, states with all sorts of
qualitative character" (p.76). To demonstrate his point, he devotes a
chapter to exposing the inadequacies of most of the more recent
reductive accounts of conscious experience, and another to defending the
reality of qualia from the ostrich-head-in-the-sand option of denying
that we actually enjoy any phenomenal experiences at all. Though some of
the more problematic scenarios for a qualia realist which have been
outlined by Dennett (1990) are not discussed, both chapters forcefully
make out the case for the idea that there is something missing from our
physicalistic worldview.
The meat of the book though, is his defence of materialism from the
conceivability argument, and his general argument for the existence of
the explanatory gap. The main obstacle to a purely materialistic
metaphysic, he tells us, is the logical possibility of zombies. From a
complete physical/functional description of a creature that is conscious
(which picks out the lower order properties), we cannot derive by a
priori means only that that creature has conscious experiences (the
higher order properties), so it is conceivable (conceptually possible)
that the physical/functional mechanisms responsible for the nature and
existence of conscious experiences and the experiences themselves could
exist independently of one another. If this is conceptually possible,
then there is a possible world in which this situation is a metaphysical
reality, but then materialism must be false for materialism is the
thesis that all properties are or are realised by non-mental properties.
An obvious response to this is to point out that standard cases of
necessary a posteriori identities such as "water = H20", fall foul of
the same argument, since it is conceptually possible that H20 could have
none of the higher order properties that it in fact has (such as
liquidity, transparency, etc.) Because this is a metaphysical
impossibility (for H20 cannot fail to have the higher order properties
that it in fact has) there must be something wrong with the argument,
and so what must really be going on in this case and the mental-physical
case is that there are two different modes of presentation - two
different concepts - which pick out the same situation. However, this
response cannot account for the fact that in the mental-physical case,
we don't seem to have two different concepts picking out the same
situation, but, rather, two distinct concepts picking out two distinct
properties - a physical one and an experiential one - and no matter how
we try to analyse an identification of the two, we will always be left
with what Smart had called "an irreducibly psychical property" (Levine
also considers arguments from Kripke and Chalmers but the main point is
the same).
The issue can be resolved, thinks Levine, by focusing on a general
question in the theory of meaning - whether or not we have a priori
access to enough information to determine the referent of a term in a
possible world considered as actual. If we think that we have, then we
are what Levine calls "ascriptivists" about that mode of presentation.
When we use a term to refer to something, we have in mind, either
implicitly or explicitly, some description that enables us to pick out
that something in a given possible world. The term "water", for example,
always picks out the substance that has the higher order properties of
actual water, since it is part of the meaning of "water" that it is
liquid, transparent, etc. In other words, "water" always refers to
"watery" stuff. However, if we think that we have very little or no
conceptual content in mind when using such referring terms, we are
"non-ascriptivists" about the mode of presentation. All there is to the
correct application of a term is the appropriate relation of the symbol
to its referent in the actual world, so "water" always refers to H20 in
any given possible world. Using this latter approach, Levine can explain
why we can't derive a priori the higher order properties of something
from its lower order properties (or microproperties) - why we can't
derive liquidity and transparency from the microphysics of H20. We can
conceive of H20 with few or even none of the higher order properties
that it in fact has, since it is conceptually possible that H20 be
opaque in normal conditions, or that it not be capable of being in a
liquid state. This is conceivable because when we refer to H20 with the
term "water", it is not essential that we have any of the properties
that we usually associate with this term in mind. But though such a
situation is conceptually possible, it does not follow that it is
metaphysically possible, for, as already noted, H20 cannot fail to have
the higher order properties that it in fact has (given that the rest of
physics and chemistry remains the same). The same considerations apply
to the mental-physical case. Even if we had a complete
physical/functional theory of consciousness, we could not infer the
nature or existence of the experiential properties which the
physical/functional mechanisms involved give rise to because of the
non-ascriptive character of that mode of presentation. But to infer from
this that the physical and phenomenal are not identical is unwarranted,
and so the conceivability argument is no threat to materialism.
An epistemic problem remains though. Nothing we can say about the
physical/functional basis of consciousness makes it fully intelligible
why conscious states have the particular nature that they have, or why,
indeed, there should be any at all. Though the higher order properties
of water can't be derived from the microphysical properties a priori,
once all the relevant empirical information is complete (physics and
chemistry), there is no sense left in wondering how H20 could have the
higher order properties that it has. This is not so in the
mental-physical case, for even when we have all the relevant empirical
information about the physical/functional basis of phenomenal
consciousness, there still seems to be "genuine, substantive cognitive
significance" (p.83) left to the question of just how such properties
could give rise to phenomenal experiences or qualia. This is due to the
fact that our concepts of qualia are "presentationally thick" - they
serve as their own modes of presentation (are "substantive") and present
themselves as having a specific quality (are "determinate"). This is in
contrast to the "presentationally thin" conceptions we have of other
properties or substances such as water, in which the referring term
involved acts as no more than a label for its referent. But now this
motivates a second conceivability argument. The existence of zombies now
seems possible due to the very fact that there is this kind of
substantive and determinate qualitative residue left which is
unexplained by our physical/functional theories, and so we can conceive
of the existence of a creature which is physically/functionally
identical to a conscious one, but which does not instantiate this
qualitative residue. Levine's response is a desperate one. He simply
denies that this "gappiness" must be explained by a distinction in
properties, telling us that the assumption that it must is based on a
kind of Cartesian model of access to the facts, and that the possibility
that distinct concepts can refer to the same thing must always remain a
live option. I agree, but then Levine's whole argument seems to be, in
the end, little more than a straight denial that distinct concepts must
pick out distinct properties, but that is the very issue which the
distinct property objection targets.
Perhaps the most we can say about the source of the explanatory gap is
that it is due to the nature of the properties involved, and this at
least enables us to avoid an objection which might be raised against
Levine's own diagnosis of the problem. According to Levine, there is an
explanatory asymmetry between the water-H20 case and the mental-physical
case. Given all the relevant empirical information in the former case,
we can't conceive of H20 without its actual higher order properties, but
we can conceive of the relevant physical/functional mechanisms
responsible for phenomenal consciousness without the qualia. Now it
might be objected that even after we have been supplied with all the
relevant empirical information in the water-H20 case, we can still
conceive of H20 without any of its actual higher order properties, or
even with completely different ones, so there is no asymmetry between
the two cases. So either all such cases will involve explanatory gaps
and there is no special threat to materialism from the existence of
qualia, or there are no such cases which involve explanatory gaps, and
so materialism is safe. I think that this shows that the real source of
the explanatory gap is due to the difference in nature of the two kinds
of property involved, the conscious and the non-conscious, and that the
gap exists because we cannot understand how properties of the first kind
can be indentical to, realised by, or interact with, properties of the
second kind. This is the more fundamental problem. There is simply no
need for further explanation of the higher order properties of water
once we have been supplied with all the relevant empirical information
about its microproperties, whether or not we can conceive differently,
because the former properties are captured, in an informative way, by
the same kinds of concepts and principles that capture the latter
properties, and we can immediately see how the microphysical properties
give rise to the higher order properties in terms of these concepts and
principles. The situation is different with qualia. No physical or
functional concept or principle can capture, in a fully informative way,
the unique properties which qualia possess: the specific qualities which
they have as we experience them (why the bark of a dog is experienced as
being different to the miaow of a cat, or why a square of red in a
Mondrian is experienced as being different to a square of yellow which
sits next to it), the general property of being non-spatial - having no
location or spatial constitution, and the bewildering property of being
"bits of awareness", as Levine would have it. These features are
presented as being properties of qualia, not properties of physical or
functional states of the brain, and so they are irreducibly psychical
properties, at least in the epistemic sense. So though it may be
possible to conceive of H20 with very different properties even after
being supplied with all the relevant empirical information about the
microlevel, we are still just conceiving of what we refer to as more
physical and functional properties, and there is no significant
explanatory gap here. But when we conceive of a zombie that instantiates
no conscious properties, or perhaps a simple thermostat which does, we
are thinking about properties that just cannot be made intelligible by
using our physical/functional vocabulary, because such unique qualities
have never had, and it is hard to see how they ever will have, a place
in the physical/functional conceptual scheme. This is where the
explanatory asymmetry comes from, and this is why there is an
explanatory gap.
The ignorance which creates the gap (the "Purple Haze" of the title) is
due, Levine claims, to the nature of our conceptions of qualia. The
substantive and determinate nature of qualitative properties is somehow
cognitively apprehensible to us in an immediate way, and so the problem
also affects our theories of cognition. Not only does qualitative
character need to be explained, but also our cognitive relation to this
character , that is, - our subjectivity. Now it is surprising that there
is no clear statement of whether he thinks that these two related
problems are permanent ones, or merely temporary hitches that future
empirical research or conceptual analysis will resolve. But he has built
on his earlier views in other ways. He has developed his idea of why
epistemic possibility is not sufficient for metaphysical possibility,
and his reason - non-ascriptivism - is a persuasive response to many of
his more recent critics. Also, he now holds that materialism is a
contingent thesis rather than a necessary one, though he doesn't tell us
how this view gets around Kripke's notorious argument to the contrary, -
that contingent identities cannot be strict identities at all. One
further problem for Levine is that the whole idea of the explanatory gap
undermines his own motivation for materialism, since part of accepting
the idea that there is a gap involves acknowledging the fact that we
cannot understand how phenomenal properties can be causally efficacious.
Yet at the very beginning of the book he tells us that it is the very
fact that they are which motivates his position. But he has no better
reason to opt for materialism than interactive dualism, for the dualist
too claims that non-material properties interact in some way with the
material ones, but can't provide an explanation of how they do this
either. If both involve a gap, why settle for ontological monism?
Perhaps the motivation for materialism then, should be something like
ontological economy or simplicity, coupled with the idea that there are
some phenomena which aren't mental - a subset of the physical -, but no
mental phenomena which aren't physical.
Though difficult to follow in places - something which might be expected
given the nature of the arguments involved - this essay is a state of
the art report on the current debate about phenomenal consciousness, and
should be read by anyone wanting to be brought right up to speed with
just where the important problems now lie. Levine has both painstakingly
examined some of the more difficult issues involving conceivability and
possibility, and outlined the conundrums which both materialist and
anti-materialist continue to face. By doing so, he has brought into
focus the need for more rigorous criteria of when to count something as
a property and when to count something as a concept, the issue which now
seems to be central to the mind-body problem.
REFERENCES
Dennett, D. (1990) Quining Qualia. In William Lycan (Ed.), *Mind and
Cognition: A Reader* (pp. 526-536) Blackwell.
Levine, J. (1983) Materialism and Qualia: The Explanatory Gap. *Pacific
Philosophical Quarterly, 64,* 354-61.