The philosophical position named  ‘physicalism‘
maintains that nothing exists except the kinds of things that are explicitly
referred to in the basic laws of physical science (particles, masses, charges,
fields) and aggregates of such basic physical things. Physicalism also maintains
that nothing happens except in strict accord with the laws of physics. Thus,
the forthright physicalist must insist that two souls united by love is nothing
but swarms of particles and fields acting in strict accord with equations found
in physics textbooks.  

Kim’s book centers on the relation
between the thesis of physicalism and its greatest historical challenge, the
existence of the mental — the ‘mental’ being a philosophical catchphrase for
minds and their ‘contents’, such as thoughts and feelings. (This usage of
‘mental’ extends to the proprietary states and processes introduced by
psychologists.) Physicalism, being a thesis about everything, must include the
mental; it must hold that the mental, like everything else, is nothing but
particles behaving in accord with physical law. However, there are different
and opposed positions among physicalists on how best to characterize
physicalism’s hold on the mental. Nevertheless, there is a bare minimal
requirement for being any kind of physicalist regarding the mental: one must
agree that the mental at least supervenes on the physical; that means
that the physical properties of a thing fully determine all its other
properties, including its mental properties.  Thus, given the supervenience of
the mental on the physical, if one created a molecule by molecule exact
physical duplicate of a person, one would thereby have done all that was
required to create an exact mental duplicate of that person. Such is
supervenience, clearly a minimal requirement of any theory going by the name of
‘physicalism’. Beyond supervenience, however, there are different forms of
physicalism.

All physicalists agree that there
are no nonphysical minds floating around and that mental states and events are
physical states and events — presumably brain states. The dispute comes with
the properties that physical and mental ‘things’ have. Pretend that the
c-fibers of my brain fire when and only when I feel a pain. It may then be easy
to accept the idea that the feeling of the pain and the firing of the c-fibers
are one and the same event. However, the property a person may have of feeling
a pain does not at all seem the same kind of property she has when
having a brain firing c-fibers. Even if our physical properties determine
all our mental properties, as supervenience and minimal physicalism require, it
may still be plausible to deny that the mental properties are ("at
bottom") physical properties. (By the way, the assumption that there are
two different sets of properties that can be studied separately is very welcome
to many who wish to maintain the autonomy of psychology; and it is plausible to
those who just can’t imagine doing what psychology does by consulting physics
texts, no matter how ‘complex’ the physical processes.) 

We now reach Kim’s central concern
in this book: There are two opposed types of physicalism that attempt to answer
the question of how mental and physical properties relate to each other. Reductive
physicalism holds that mental properties can be identified with, or reduced
to, physical properties, that mental properties are nothing but physical
properties.  Nonreductive physicalism believes in supervenience without
reduction, it asserts that while, of course, the mental supervenes on the
physical, mental properties cannot be identified with or reduced to physical
properties.  Recently, the reductive brand of physicalism has lost its earlier
popularity to the nonreductive brand. This change of theoretical fortune is due
to the increasing realization that it is highly improbable that there is a well
defined set of purely physical properties which are identical to the mental
properties, because those mental properties can be possessed by things of such
divergent physical natures as people, snails, Martians, and computers. The
property of, say, having a memory cannot be the same as the property of being
in any one kind of physical state, for while both I and a snail may remember
something, we do not share any one physical property that could underlie both
of our memories; the memory state we share supervenes on different physical
properties in our two cases and cannot therefore be identical to either one of
them.

(To further clarify the idea of
supervenience, and thereby, the philosophical position of nonreductive physicalism,
compare the relation between the physical and mental properties of a person to
the relation between the aesthetic and physical properties of an art object:
the aesthetic properties of an art object are fully determined by its physical
properties, but those aesthetic properties are clearly not reducible or
identical to its physical properties: To make a beautiful painting ugly you
must change it physically, but its beauty is not something that can be reduced
to or identified with its pigments and edges. Nonreductive physicalists hold
that the relation between the physical and mental properties of a person are
like the relation between the physical and aesthetic properties of a painting
in that the mental properties of a person supervene on the physical properties
of his body (brain) — the physical properties fully determine the mental
properties — but the latter cannot be identified with, or reduced to, the
former.)

The refutation of nonreductive
physicalism is the main task of Kim’s book.  I will caricature his argument
here.  To begin, suppose that that someone’s thinking that she won the lottery
caused her to feel good. We have, then, a case in which one mental event caused
another:  The thought caused the feeling. Note that this causal relation surely
holds in virtue of the fact that he two mental states have the mental properties
they do: the first state’s being of the kind it is causes the second, it’s
being of the kind of state it is.. Surely, Kim insists, this sort of thing
happens all the time.  So far, there seems no problem; but, we proceed.  If,
as all physicalists agree, the mental supervenes on the physical, then the
feeling could not have existed unless it was being determined to exist by some
physical state which may be called its "supervenience base’.  Name the
physical supervenience base of the feeling — presumably a brain state — ‘F’. 
Now we seem to have a problem!  What is the cause of the feeling?  The thought
or its supervenience base F?  It is true that we began by assuming that the
thought caused the feeling, but if the feeling’s physical supervenience base F
exists, so does the feeling — whether or not the thought existed to do its
causal work. We cannot say that the thought and F are both partial causes, for
they are not related as partial causes, as are the spark and the oxygen that
result in a fire.  Nor are they related like the stab and the shot that cause
the ‘overdetermined’ death. Except for cases of partial causes and
overdetermination, nothing can have two causes — that which causes something
is all that causes it. The thought qua thought loses any claim to
being the cause of the feeling.  Now note another implication of physicalism:
If physicalism is true, then every event that has a cause, has a physical cause
— since, as was stated in the first paragraph, physicalism asserts that
everything behaves in accordance with the laws of physics.  Thus, call the
physical cause of F,  ‘T’. (Presumably, T is the physical — presumably neural
— supervenience base of the thought that one has won the lottery.)  Now, it
seems clear that if the thought causes the feeling, it does so by
causing the physical supervenience base of the feeling, F.  But now the
question is: What is the cause of F — the thought or T?  As before, there is
no question of partial causes or overdetermination.   There seems to be only
one way out of this dilemma: We need recognize that the thought that one won
the lottery is identical to the instanced property of being T and the instanced
property of being the good feeling is  identical to the instanced property of
being F, and the  first event is the cause of the second.  But nonreductive
physicalism makes this solution impossible!   Thus, if sometimes, mental events
are causes, if we feel good because of something we thought, nonreductive
physicalism must be rejected.  That leaves us with  at least three options. 
First, we can become eliminativists by rejecting the reality of mental events,
denying the very existence of such things as beliefs and feelings; Kim rejects
that as being inconsistent with our experience. Second, we can become
epiphenomenalists, denying that mental events ever cause anything; but Kim
considers the reality of mental causation ‘non-negotiable’.  Given such
alternatives, Kim thinks we must accept reductive physicalism.

Kim develops this argument and
meets various objections.  He shows that dualism is even in worse shape for
dealing with problems of "mental causation’ — while illuminating the
concept of causation itself. He further develops his ideas concerning
reduction.  Finally, he assesses the prospects for physicalism and reaches the
conclusion that it is almost correct, failing to account for the immediate
objects of awareness.

This book is not written for those not already well
familiar with the issues, vocabulary, and techniques of contemporary, analytic
philosophy of mind; the general reader will get little out of it.  Much of it
will be familiar to those who have kept up with Kim’s previous work, but many
of these same readers will be grateful for the further clarification and
development. I was not happy with the relative lack of response to various
alternative positions, such eliminativism, anomalous monism, and even
epiphenomenalism.  I feel that Kim also offered excessively short shrift to
global supervenience and possible considerations stemming from Quine’s doctrine
of the indeterminacy of translation.

© 2005 Alan N.
Sussman

Alan N.
Sussman received his Ph.D. in philosophy from the University of Chicago. He has
published a few papers, including one in The Journal of Philosophy. He taught
philosophy at various colleges and universities in the US and Africa. At
present he teaches part time at Truman College, Chicago. His philosophical
interests are primarily in philosophy of mind.

Categories: Philosophical