The Metaphysics of Mental Causation
The Exclusion Problem Revisited, Reconsidered and Resolved
ANDERS STRAND
Ph.D. Thesis in Philosophy
Department of Philosophy, Classics, History of Art and Ideas
Ph.D. Program in Philosophy
Faculty of Humanities
University of Oslo
III
Table of Contents
ACKNOWLEDGMENTS
v
PREFACE
vii
INTRODUCTION
1
The Metaphysics of Mental Causation
PAPER I
47
Immense Multiple Realization
PAPER II
75
Causal Exclusion and the Preservation of Causal Sufficiency
PAPER III
103
Proportionality and the Metaphysics of Causation
PAPER IV
127
Fleshing out the Workings of Realizable Properties
APPENDIX: BIBLIOGRAPHY
151
V
Acknowledgments
First of all, thanks to my supervisor Carsten Hansen for sage advice and detailed
feedback on all aspects of my philosophical work.
Several people were kind enough to read substantial parts of the thesis and offer
helpful comments. They include Eyjólfur Kjalar Emilsson, Øistein Galaaen, Heine
Alexander Holmen, Jon Lindstrøm, Anders Nes, Gry Oftedal, and Iris Oved.
I am grateful to friends and colleagues for discussing issues of relevance to the thesis
with me: Frank Barel, Frode Bjørdal, Panos Dimas, Bengt Ekelberg, Nils RollHansen, Øystein Linnebo, Bjørn Ramberg, Lars Reinholdtsen, and Jim Westin.
For inspiring discussions of philosophy in general, thanks to the gang at NT325.
During my research stay at the Department of Philosophy at Rutgers I benefited from
discussions and courses with some of the leaders in the field. Thanks to Brian
McLaughlin who offered on-leave time to participate in a colloquium on mental
causation, to Dean Zimmerman for late night discussions of relevant issues in
metaphysics, and to Igal Kvart for many and long discussions of probabilistic
accounts of mental causation. Thanks to John Hawthorne, Ted Sider, Jerry Fodor,
Lila Gleitman, Christhopher Peacocke, Ernie Lepore, Jason Stanley, Larry Tempkin
and Derek Parfit for allowing me to sit in on their courses. Special thanks go to my
sponsor Barry Loewer, and to Susan Viola for all her kind help with the practical
aspects of my visit.
Thanks to Chris Saunders for proofreading.
Last, but not least, thanks to my family and friends for encouragement, love and
support.
VII
Preface
The present thesis is submitted in partial fulfillment of the requirements for the
degree Philosophiae Doctor (Ph.D.). It consists of four papers and an introduction that
provides background for, motivates, and summarizes the discussions in the individual
papers.
The first paper is a slightly revised version of “Immense Multiple Realization”
published in Metaphysica: International Journal for Ontology and Metaphysics,
No.1, 2007. I have not revised that published version other than to incorporate crossreferences to the other papers and rephrase some of the formulations. The page
numbering also differs from the published version.
Although the thesis as such comprises four separate papers, I supply crossreferences where appropriate, and pages are numbered consecutively from first to
last. Each paper has its own footnotes and references, however. I’ve also added, as an
appendix, a bibliography of all works referred to and certain other works that have
proved relevant for the discussions in this thesis.
INTRODUCTION
The Metaphysics of Mental Causation
Anders Strand
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Introduction
Exclusion Arguments
The Generalization Argument
Ways Out of the generalized Causal Exclusion Problem
An Obvious Reply and a not-so-obvious Response: The Nomological
Determination Argument
Anyway, is this really Metaphysics..? Reification and Theory-World
Projection
Proportionality, Correlation and External Individuation
Different Kinds of Realizable Properties: Clarifying the Scope of My View
Why not Substantial Dualism?
Terminological and Substantial issues about ‘Reduction’
‘Causation’ in the Mental Causation Debate
Précis of the Individual Papers
1. Introduction
The subject of this thesis is what is known as the causal exclusion argument. In brief,
the causal exclusion argument says that if mental causes are not identical to physical
entities they are excluded from the causal nexus by purely physical causes.
Accordingly, non-reducible mental entities are causally inert. The exclusion argument
forcefully targets non-reductive physicalism. Commonly, non-reductive physicalists
are committed to mind-body dependence or mind-body supervenience, and thereby to
Introduction
2
the existence of a physical base for any mental phenomenon. This physical base puts
the causal efficacy of the mental in jeopardy because it doesn’t leave any causal work
for the mental phenomenon to do. Or so the causal exclusion argument concludes.
One standard response to this argument has been labeled the generalization
argument. In brief the generalization argument says that special science phenomena,
like chemical phenomena, biological phenomena, geological phenomena etc., relate
to the microphysical in a way that is relevantly similar to the way in which mental
phenomena relate to the physical. Consequently, the causal exclusion argument will
render all special science phenomena causally inert. However, since that is an absurd
result there just has to be something wrong with the exclusion argument. Or so the
generalization argument concludes.
Even if correct, this response is not entirely satisfactory. It is desirable to
know exactly what is wrong with the exclusion argument. The generalization
argument provides reasons to deny the conclusion of the argument, whereas a fully
satisfactory response would require an account of exactly how the exclusion
argument fails. In the absence of such a response both philosophers of mind and
philosophy of science in general have reasons to remain perplexed.
One of my goals is to distill the positive content of the causal exclusion
argument. This task is approached in the second and fourth individual papers. Getting
clear on the positive content of the exclusion argument gives us a constraint on nonreductive theories of mind, at least in so far as accounting for mental causation itself
is a constraint on such theories. In the second paper I try to delineate the insight
negatively, especially by criticizing the so-called causal exclusion principle. In the
fourth paper I spell out an exclusion argument that is independent of specific
understandings of causation. I call this the Nomological Determination Argument. I
give a metaphysical account of property realization that answers this argument, and
this account also answers the original causal exclusion argument.
My main aims and conclusions are as follows. In the first paper I argue that
Kim’s reductive account of mental causation conflicts with our standard
understanding of macro causation because it involves a radical revision of our
understanding of mental causation in particular and of the patterns of dependence
The Metaphysics of Mental Causation
3
between macro-causal relata in general. In the second paper I present
counterexamples to the causal exclusion principle, and show that the proponent of the
causal exclusion argument needs a strong, and questionable, version of the principle
of the causal closure of physics in order to establish his or her conclusion. In the third
paper I contrast Yablo’s account of mental causation with an identity-based account,
and argue that the choice of account depends on its merits on issues outside the
specific mental causation debate. Finally, in the fourth paper, I spell out my version
of physical realizationalism on which the causal efficacy of realizable mental
properties and events is compatible with central physicalist tenets.
In this introductory paper I rehearse the central arguments and assumptions of
the debate. Sections 2–4 present the causal exclusion argument, the generalization
argument and different ways of responding to the causal exclusion argument. In
section 5 I discuss the Nomological Determination argument mentioned above, and
also point out the positive account I give in paper IV. Section 6 discusses the worry
that some replies to the causal exclusion argument conflate metaphysical and
explanatory constraints. Sections 7 and 8 address questions regarding the scope of the
view I propose. Sections 9–11 are intended to clarify some of the background
assumptions and concepts employed. Section 12 briefly summarizes the individual
papers. Sections 2 through 6 should give sufficient background for reading the
individual papers. The other sections are primarily intended to tie up loose ends and
clarify my use of central concepts.
People with strong dualistic inclinations might find that I move too far in a
physicalistic, or naturalistic, direction. Finding the right location among all possible
views is of course a task that any philosopher of mind finds both perplexing and
fascinating. What I’ve come to realize more and more strongly – as so often in life –
is that this endeavor is a game of give and take. The call for a sound account of
mental causation forces us in a physicalistic direction, but, as I argue, not further than
the kind of physical realizationalism I propose.
Introduction
4
2. Exclusion Arguments
The physical cause threatens to exclude, and preempt, the mental cause.
This is the problem of causal exclusion.
(Jaegwon Kim 1998, page 37)
Jaegwon Kim has argued forcefully that non-reductive physicalism is committed to
epiphenomenalism for the mental. Epiphenomenalism for the mental is the view that
mental phenomena lack causal powers; that they are causally inert, and thus that they
have no effects. Let us take a look at the background against which this worry arises.
According to standard non-reductive physicalistic theories of mind, like
functionalism and other versions of physical realizationalism, the mental is dependent
on but not reducible to the physical. Typically, the dependence claim is cashed out as
an adherence to mind-body supervenience. Claims of supervenience come in a wide
variety, and there is a huge literature on the subject 1 . Let us confine ourselves to the
following claim about event-supervenience at present.
Event Supervenience: Events of kind M supervene on events of kind P in that
for every occurrence m1 of an event of kind M at time t, an event p1 of kind P
necessarily occurs at t, and whenever an event qualitatively identical to p1
occurs an event qualitatively identical to m1 occurs.
One thing that will be a recurrent point of emphasis is the order of causal and
metaphysical priority between supervenient events and their subvenient bases. Talk of
bases and realizers alone indicates that the order of metaphysical priority is from the
physical to the mental. The idea is that in some sense the physical is more
fundamental than the non-physical entities that supervene on it, or are realized by it.
1
Some relevant discussions of supervenience in relation to the mind-body issue are; Jaegwon Kim’s
“Concepts of Supervenience” and “Psychophysical Supervenience” [Kim 1993a, 1993b], Terence
Horgan’s “From Supervenience to Superdupervenience: Meeting the Demands of a Material World”
[Horgan 1993], Brian McLaughlin’s “Varieties of Supervenience” [McLaughlin 1995], and Paul
Teller’s “A Poor Man’s Guide to Supervenience and Determination” [Teller 1999].
The Metaphysics of Mental Causation
5
This conviction seems to be deeply embedded in the discussion of mental causation.
The question is almost always asked in terms of how the mind can have a place in the
physical world. It’s enough to consider the titles of seminal books like C.D. Broad’s
The Mind and It’s Place in Nature and Jaegwon Kim’s Mind in a Physical World.
On Earth life developed approximately four billion years ago. For a very long
time bacterial and other single-cellular life-forms were the only life-forms. Much later
in the history of our planet, organisms that plausibly can be said to exhibit simple
forms of mentality developed. Because of these facts we have a clear conception of a
physical world devoid of mentality. At the same time, we admittedly have little
experience with mentality in a world devoid of physical phenomena. These two
points alone provide prima facie reasons to think that the physical has metaphysical
priority over the mental in the sense that the physical can exist without the mental, but
not vice versa.
Let’s see how this conforms to the standard understanding of ontological
dependence. Here is the definition of ontological dependence from the Cambridge
Dictionary of Philosophy.
To say that the entities of one sort (the B’s) are ontologically dependent on
entities of another sort (the A’s) means this: no B can exist unless some A exists;
i.e. it is logically or metaphysically necessary that if any B exists, some A also
exists. [Van Cleve 1995, page 192]
The argumentative leap from observed contingent facts about life on our planet to the
claim that an ontological dependence relation obtains is not uncontroversial. Given
the definition of ontological dependence just stated, such a relation requires that there
are no metaphysically possible worlds that exhibit mentality while being devoid of
physical phenomena. That strong claim has been questioned by, among others, Robert
van Gulick in his article “Who’s in Charge Here? And Who’s Doing All the Work?”.
Here’s what he says about the autonomous status of higher-level patterns:
(…) such patterns and their interrelationships can enjoy a substantial degree of
independence from their particular physical instantiations and perhaps even from
physical instantiation altogether. [Van Gulick 1993, page 255]
Introduction
6
The general idea is that higher-level phenomena and mental phenomena in particular,
are ontologically independent of lower-level/physical phenomena if it is
metaphysically possible that these higher-level phenomena could exist in a nonphysical world. Such considerations are tightly related to the question of the modal
scope of mind-body supervenience. I will not go into details on that question, other
than to note that the questions of ontological dependence and metaphysical priority
are disputed 2 .
There is another consideration that might further deflate the belief in physical
priority. Notice that the definition of ontological dependence as proposed by Van
Cleve involves quantification: “no B can exist unless some A exists”. In contrast we
might also wonder whether a particular mental phenomenon is ontologically
dependent on its particular physical realizer. When answering this question, however,
we seem to get the metaphysical priority the other way around. Since the particular
mental phenomenon has its physical realizer as a sufficient condition, it is itself a
necessary condition for the physical realizer. Consequently, the particular physical
realizer could not exist without the mental phenomenon that it realizes 3 .
These are observations that are important to bear in mind. A tentative
conclusion is that a belief in physical priority is common, but not entirely
uncontroversial. Another reason for laying out these considerations is that they
provide a background for an exposition of the causal exclusion argument. The
versions I present here are my renditions of Kim’s supervenience argument, it is
based on the expositions in [Kim 1998] and [Kim 2005]. However, as I understand
Kim, there seem to be two distinguishable versions of the argument. Kim
distinguishes two versions of the argument [Kim 2005, pages 41–45]. One runs
without supervenience as a premise, the other invokes causal closure in a way that
seems to be in principle superfluous. In the following I give my renditions of these
two versions of the argument. The first version, which I here call the Supervenience
Argument, attempts to show that the following three claims are incompatible:
2
Moreover, and as I return to in section 11 of this introduction, my account is compatible with denying
that mental phenomena necessarily have physical realizers.
3
My positive account in the fourth paper relies on this claim being true.
The Metaphysics of Mental Causation
7
1. Non-Reductive Physicalism: Mental events supervene on but are not
identical to physical events.
2. Mental Causation: At least some mental events have physical effects.
3. Causal Exclusion Principle: An effect cannot have more than one
sufficient cause at a time.
The argument can be presented as a reductio on Mental Causation:
The Supervenience Argument
i. Assume Mental Causation for reductio
ii. Non-Reductive Physicalism
iii. By (ii) any mental cause has a physical supervenience base that is
nomologically sufficient for it, this physical base is therefore a sufficient
cause of any effect for which the supervenient mental cause is sufficient.
iv. From (i)-(iii) we know that some physical effects have more than one
sufficient cause.
v. Causal Exclusion Principle: An effect cannot have more than one
sufficient cause at a time.
vi. Contradiction between (iv) and (v).
The supervenience relation is supposed to ensure that we get the problematic
replication of causes stated in step (iii). Step (iii) rests on the claim that the alleged
causal sufficiency of the mental cause is transferred to its physical supervenience
base. This step is the Achilles’ heel of the argument, and it can and should be
questioned 4 .
Consider the standard Kim style visualization:
4
I argue against the validity of this inference in section 4 of paper II. Moreover, Kim alludes to the
causal closure principle in justifying this inference, he says: “We can give relatively informal reasons
for choosing P over M as the cause of P*, but for a general theoretical justification we may appeal to
the causal closure of the physical domain.” [Kim 2005, page 43]
Introduction
8
Fig.1.
M
P
P*
Assuming that M, a mental event, is causally sufficient for P*, and that P is
metaphysically sufficient for M, the idea is that P ipso facto qualifies as a sufficient
cause of P*. As Kim reasons:
If you take causation as grounded in nomological sufficiency, P qualifies as a
cause of P*, for, since P is sufficient for M and M is sufficient for P*, P is
sufficient for P*. [Kim 1998, page 43]
However, and this is a recurrent point of discussion in my thesis, there are reasons to
think that causal sufficiency requires more than nomological sufficiency. This is
reflected in the idea that effects depend counterfactually on their causes, at least in
general 5 . One cannot, therefore, infer that P qualifies as a cause of P* from the fact
that M qualifies and that P necessitates M. The idea is that there are relevantly close
possible worlds in which M occurs and causes P* without P occurring. It is therefore
puzzling when Kim says:
If you choose to understand causation in terms of counterfactuals, again there is
good reason to think that P qualifies: if P hadn’t occurred M would not have
occurred (we may assume without prejudice, that no alternative physical base of
M would have been available on this occasion), and given that if M had not
occurred P* would not have occurred, we may reasonably conclude that if P had
not occurred, P* would not have either. [Kim 1998, page 43, my italics]
The puzzling claim appears in the parenthesis. Multiple realization allows for
scenarios where M can occur without P and still cause P*. In order to establish the
claim that also P qualifies as a cause of P* we need an argument. If one thinks of
5
Counterexamples to the counterfactual analysis of causation, like preemption and overdetermination
cases, are of course also counterexamples to the general claim that causal relations are always
accompanied by relations of counterfactual dependence.
The Metaphysics of Mental Causation
9
multiple realization in terms of ‘same mental state – radically different physical
implementation’ the claim seems quite plausible. In all the possible worlds relevant
for the evaluation of the counterfactual, M will plausibly be realized by P. However,
as I argue in detail in the first of the four individual papers, multiple realization does
not require speculative examples like that 6 . Rather, the different realizers might be
very similar, and share causal potentials to a significant degree.
A better and probably less controversial way of establishing the existence of a
competing cause candidate is by invoking the principle of the causal closure of
physics. Kim does so in [Kim 1998] and also in the so-called second completion in
[Kim 2005, chapter 2]. The causal closure principle says:
4. Causal Closure of Physics: Any physical effect has a sufficient physical
cause at all past times 7 .
It is interesting to reflect on the relation between the argumentative job done by step
(iii) in the Supervenience Argument, and the argumentative job done by the Causal
Closure of Physics in the Causal Exclusion Argument 8 . However, let me first state
the second version, which I label the Causal Exclusion Argument. This is also
formulated as a reductio on Mental Causation.
6
In the first paper I argue that macro-phenomena are immensely multiply realized in determinate
microphysical complexes, and that this creates serious problems for Kim’s positive account of mental
causation. It is interesting to note that the argument in that paper does not rule out so-called creeping
reductions of psychological phenomena to lower-level neurophysiological phenomena. It does,
however, block a sweeping reduction of psychological phenomena to determinate complexes of microphysical phenomena. For this reason I can remain neutral on certain issues in the contemporary debate
on multiple realization. In particular, I can accommodate the arguments presented in [Bechtel and
Mundale 1999] to the effect that fine-grained psychological phenomena can be identified with finegrained neurophysiological phenomena. However, I prefer to adopt a wait-and-see attitude on this
issue. To my knowledge, the concepts of sweeping and creeping reductions were first used by Kenneth
Schaffner in [Schaffner 2002].
7
The principle is often formulated conditionally, as “Any physical effect that has a sufficient cause at a
time has a sufficient physical cause at that time.” This formulation opens for scenarios where physical
effects that lack sufficient causes are still caused by mental causes. For simplicity I use an
unconditional formulation here; as far as I can see it doesn’t beg any questions in the present context. I
use the conditional formulation in my detailed discussion of causal closure in paper II.
8
Kim says about the virtues of an argument using causal closure as an explicit premise:
“Supervenience is not needed as a premise, and the claim that M’s supervenience base P has a valid
claim to be a cause of P* has been bypassed, making it unnecessary to devise an argument for it.”
[Kim 2005, page 44]
Introduction
10
The Causal Exclusion Argument
(i)
Assume Mental Causation for reductio
(ii)
Non-Reductive Physicalism 9
(iii) Causal Closure of Physics
(iv) By (iii) all physical effects have sufficient physical causes, but by (i) and
(ii) some physical effects have additional mental causes.
(v)
Causal Exclusion Principle: An effect cannot have more than one
sufficient cause at a time.
(vi) Contradiction between (iv) and (v).
The causal closure principle directly asserts the existence of a sufficient physical
cause for any physical effect. It does not, however, provide any information on the
particular physical cause. The physical cause might be the realizer of the alleged
mental cause, but the principle itself is silent on this question. On the other hand, the
reasoning in step (iii) of the Supervenience Argument attempts to establish the
physical base of any mental cause as a cause for whatever effect the mental cause
might have. This is a stronger claim, and for that reason more problematic. On the
other hand, step (iii) in the Supervenience Argument is weaker in the sense that it
does not require, like the causal closure principle does, that there is a sufficient
physical cause for any physical effect that has a sufficient cause.
Spelling the arguments and premises out in this way is intended to facilitate
the discussions of different concrete responses. I will in the following section present
one of the most common responses to the causal exclusion argument, namely the socalled generalization argument 10 .
9
Observe that mental-physical supervenience is not used in this version of the argument. The relevant
aspect of non-reductionism is the non-identity claim.
10
The term ‘generalization argument’ was used by Kim in [Kim 1998], I’m not sure where it first
originated with the designation used here.
The Metaphysics of Mental Causation
11
3. The Generalization Argument
If things like statues and baseballs existed, everything they allegedly cause would be
caused by their parts; if statues and baseballs existed, they would be – at best –
wholly causally redundant. This, I argue, leads to their elimination.
(Trenton Merricks 2001 page VII–VIII)
Trenton Merricks uses a causal exclusion argument to argue against the existence of
ordinary macro-objects like statues and baseballs. This is an application of the causal
exclusion argument that many philosophers would take to be a reductio ad absurdum
of the set of premises on which the argument is based.
Indeed, such a reductio has figured as a standard response to exclusionist
worries about mental causation. Roughly, the idea is that if it can be shown that
mental phenomena relate to basic physical phenomena in a way relevantly similar to
the way other special science phenomena relate to basic physical phenomena, then the
causal status of mental phenomena is secured because it would be absurd to deny the
causal status of all special science phenomena. As Jerry Fodor puts it:
If beliefs and desires are as well off ontologically as mountains, wings, spiral
nebulas, trees, gears, levers, and the like, then surely they’re as well off as
anyone could need them to be. [Fodor 1990, page 141]
Where to draw the line for explanatory satisfaction will vary with the context of
inquiry you’re situated in. In Fodor’s context, the generalization argument serves the
purpose of shifting the argumentative burden back to the causal exclusionist.
However, in my context of inquiry, which is an attempt to understand the workings of
mental causation, the generalization argument only serves to widen the scope of the
problem. Rather than providing a positive account that answers the challenge, it only
shows, if correct, that the challenge is even more radical than it appears at first
glance.
Introduction
12
The following claims appear to be just as well established as the four claims
that gave rise to the original causal exclusion problem while giving rise to a broader
scoped analogous higher-level causation problem.
1. Non-reductionism: Higher-level phenomena are not identical to lower-level
phenomena.
2. Higher-level Causation: At least some higher-level causes have microphysical effects.
3. Causal Exclusion Principle: An effect cannot have more than one sufficient
cause at a time.
4. Causal Closure of Microphysics: Any microphysical effect has a sufficient
microphysical cause at any past time 11 .
The result is that the causal efficacy of all higher-level phenomena is put in jeopardy;
a radical conclusion indeed. Here’s the generalized version of the argument:
The Generalized Causal Exclusion Argument
(i)
Assume Higher-Level Causation for reductio
(ii)
Non-reductionism
(iii) Causal Closure of Microphysics
(iv) By (iii) all microphysical effects have sufficient microphysical causes, but
by (i) and (ii) some microphysical effects have additional higher-level
causes.
11
As argued by Scott Sturgeon [Sturgeon 2000, chapter 6], among others, the microphysical domain is
the most plausible candidate for a causally closed domain. I tend to agree with this view, at least when
we allow ourselves to think of nomological determination relations as causal relations. What we have
good reasons to believe is that (the probability of) any microphysical phenomenon will be completely
determined by past micro-physical events and conditions together with the laws of nature. However, as
I try to pinpoint in the second paper of this thesis, there are elements of requiredness, counterfactual
dependence or proportionality accompanying causal relations. If any of these are made into an
essential requirement for causal relations, the claim of microphysical causal closure becomes less
convincing. My tentative view is that we have to differentiate between different kinds of causal
relations, and that the kind of nomological determination we find within the microphysical domain
reasonably counts as one kind of causal determination. That is also why issues raised by the
Nomological Determination Argument, which is discussed in section 5 and in the fourth paper, are of
crucial importance.
The Metaphysics of Mental Causation
(v)
13
Causal Exclusion Principle: Effects cannot have more than one sufficient
cause at a time.
(vi) Contradiction between (iv) and (v)
It is not easy to block this generalized version of the exclusion argument without
thereby denying one of the premises of the original exclusion argument. This is of
course what makes the generalization argument forceful. One might therefore
reasonably expect a better understanding of higher-level causation in general to shed
more light on the mental causation issue 12 .
Status quo is that we have a radical problem in our hands. Is there any higherlevel causal activity whatsoever? What resources are available for us to get to grips
with this problem?
4. Ways Out of the Generalized Causal Exclusion Problem
A philosophical problem has the form: “I don’t know my way about”
(Ludwig Wittgenstein, Philosophical Investigations, paragraph 123)
In order to find a way out of the causal exclusion problem, allow me to contrast two
rather different philosophical camps. Let’s call the first one the exclusionist camp, on
which converge the proponents of the causal exclusion arguments we’ve just
discussed. The other camp brings together non-reductionists that argue for the causal
efficacy of mental phenomena. Let us call these the believers. What are the arguments
in favor of this second position?
Several philosophers have argued that a supervenient event, given certain
constraints, can trump its subvenient event as cause for an effect in question. In other
words, they agree with the exclusionist that there is a state of causal competition that
has to be resolved, but they take the opposite stance regarding the winner. The
12
Importantly, this is not to say that there are no further obstacles to a sound account of mental
causation. For example, externalism might pose problems that are unique for mental phenomena. I
make some remarks on this issue in section 7 of this introduction.
Introduction
14
believers argue that the supervenient entity wins (or at least can win), while the
exclusionists favor the subvenient cause candidate. The line of reasoning behind the
believer’s claim can be based on different but related requirements on causation.
Suggestions figuring in the literature include for example that causes should be
proportional to their effects [Yablo 1992, 1997], and that they should be maximally
correlated with their effects [Williamson 1998]. Peter Menzies has provided
examples where two events supervene on the same event while they differ in their
causal roles [Menzies 1988]. Such examples provide reasons to think that one cannot
reduce higher-level causes to lower-level causes 13 . In addition, the widespread view
that effects depend counterfactually on their causes can be used in an argument
favoring higher-level causes 14 .
In paper II I distinguish between sufficient causes and minimal sufficient
causes, and argue that even if physical effects always have sufficient physical causes
they might have minimal sufficient mental causes too. Minimal sufficient causes are
sufficient causes that do not necessitate other simultaneous sufficient causes for the
same effect. To see how this works, consider an abstract case where C is causally
sufficient for E and A is metaphysically sufficient for C.
Fig.4a.
Minimal sufficient cause
C
E
Metaphysical
necessitation
A
Sufficient cause
The general response is simple; one cannot infer that A is a minimal sufficient cause
from the facts that A is sufficient for C and C is a minimal sufficient cause of E. This
reasoning can be used to block step (iii) in the supervenience argument. Alternatively,
as I do in paper IV, the distinction between sufficient causes and minimal sufficient
causes can be used to separate several different versions of the principle of the causal
closure of physics. Weak versions of causal closure that only claim the existence of a
13
I discuss such examples, and how they can be accommodated within my suggested framework, in
the fourth paper.
14
See e.g. [Loewer 2001] and [Bennett 2003].
The Metaphysics of Mental Causation
15
sufficient physical cause, and not a minimal sufficient physical cause, for any
physical effects are arguably compatible with the existence of minimal sufficient
mental causes for physical effects.
Here’s an abstract example. Suppose that event-type C has three different
realizers: R1, R2 and R3. On a given occasion an instance of C occurs, realized by an
instance of R1, and C causes E. If C is causally sufficient for E on this occasion, then
it is minimal relative to R1. This would be the case if, in the relevant possible worlds,
C occurs without R1 (i.e. realized by either R2 or R3) and E is brought about in those
worlds. Remember our discussion of step (iii) in the supervenience argument, which
involved an inference from the causal sufficiency of the supervenient event to the
causal sufficiency of its subvenient event. It is now clear how this inference fails for
minimal sufficient causes. If C is a minimal sufficient cause for an effect, then none
of its necessitators will be minimal sufficient causes for that effect (apart from C itself
of course) by definition.
Accounts that have certain similarities to this view figure in the literature. A
requirement of proportionality between cause and effect is discussed in detail by
Stephen Yablo [Yablo 1992, 1997]. The requirement of proportionality says that a
cause has to be enough for the effect, but not more than enough, where ‘enough’
roughly means sufficient in the circumstances. ‘Not more than enough’ can be read as
a minimality-constraint on causes. However, his account relies on the claim that
determinables are not causally excluded by their determinates. Yablo’s argument for
this claim is based on a version of the generalization argument. In the following quote
from Yablo ‘passing the exclusion test’ amounts to not being causally excluded by
the exclusion argument:
Almost whenever a property Q is prima facie relevant to an effect, a causally
sufficient determination Q´ of Q can be found to expose it as irrelevant after all.
Applying the argument Q´, Q´´, etc. in turn, it appears that only ultimate
determinates – properties unamenable to further determination – can hope to
retain their causal standing. [Yablo 1992, page 258]
This is intended to show that there must be something wrong with the generalized
causal exclusion argument. The reason is that determinable properties are paradigm
Introduction
16
cases of causally relevant properties. Granting that such cause-candidates don’t
compete for causal influence, the proportionality principle is used to argue that the
determinable can be the cause of an effect in the presence of its determinates. Some
determinable properties are enough for their effects, while their specific determinates
are more than enough for the effect. For certain causal relations involving a
determinable property D it is causally irrelevant what specific determinate D had 15 .
Notice that Yablo’s account has a two step structure: (1) he argues that
determinables and determinates don’t compete for causal influence; and (2) he argues
that a determinable can be the cause of a given effect in the presence of its
determinate. My account differs mainly on the first step, where I flesh out an account
of realization that explains why there is no causal competition between realizable
properties and their realizers. This is done in paper IV. As regards step 2, I invoke the
concept of a minimal sufficient cause which leads to a reformulation of the causal
closure principle in paper II.
A requirement of maximal correlation is a third consideration that can be used
to establish step 2 16 . The statistical concept of a correlation coefficient seems tailormade to pinpoint the issue.
Correlation Coefficient between X and Y:
Corr (X,Y) =
Cov (X,Y)
σX σY
=
E [(X-μX)(Y-μY)]
σX σY
The correlation coefficient between two variables X and Y, Corr (X,Y), is obtained by
dividing the covariance between X and Y by the product of the standard deviations
for X and Y 17 . In this way one gets a measure that is likely to reflect the strength and
direction of the relationship between X and Y. The important point is that the
15
I discuss Yablo’s account in more detail in the third paper.
See [Williamson 1998] for a very good discussion of correlation and the causal relevance of
externally individuated mental phenomena.
17
The standard deviation of X is the square root of the variance of X. Both the standard deviation and
the variance are measures of spread in the distribution of specific values of X. The correlation
coefficient takes values in the range from -1 to 1. My presentation here is based on [Bhattacharyya and
Johnson 1977, chapter 4], which is a standard textbook in statistics.
16
The Metaphysics of Mental Causation
17
measure is sensitive both to high values of X being correlated with high values of Y,
and low values of X being correlated with low values of Y. Even if all high values of
X are correlated with high values of Y, you will not get a very high measure unless
low values of X are correlated with low values of Y 18 . This can be seen more or less
directly from the formula: When X deviates from the expected value μX then Y has to
deviate from its expected value μY to produce an effect on the correlation coefficient.
If low values of X are randomly related to high and low values of Y, this will likely
sum to a null effect on the correlation coefficient. Accordingly, what has to be the
case for a high measure on the correlation coefficient is that high and low values of X
are both correlated with respectively high and low values of Y (positive correlation),
or that high and low values are both correlated with respectively low and high values
of Y (negative correlation).
Surely, a high correlation between two variables does not guarantee a causal
relationship between them. The relation might be spurious, as in cases where both
have a common cause. The important point is that a high score on this measure,
which is often used as a strong indication of causal relations, requires both that low
values of X are correlated with low values of Y and that high values of X are
correlated with high values of Y. The correlation coefficient can be used to illustrate
and argue, in the same way as proportionality and minimality, that a supervenient
event can be the cause of an effect in the presence of its specific realizer/subvenient
event. The idea is that a supervenient event might be better correlated with a given
effect than its subvenient event.
Let us return to our two opposed philosophical camps. According to the
exclusionists any subvenient event causally excludes its supervenient brother on a
given occasion, while the believers offer reasons to causally disregard the subvenient
event in favor of its supervenient brother. Both camps seem to share a background
assumption: they both seem to find sibling rivalry unavoidable in that they find the
18
X and Y could also be negatively correlated, i.e. that high values of X are correlated with low values
of Y and vice versa. This would depend on our choice of random variables (which are functions that
ascribe numerical values to the simple events in the sample space).
Introduction
18
existence of more than one sufficient cause for a given effect untenable 19 . I provide
reasons to question this general dismissal of causal overdetermination in the second
paper of the thesis. I argue that causal overdetermination, in the sense of an effect
having more than one sufficient cause at a time, is completely acceptable as long as
we have a satisfying explanation which tells us why this overdetermination occurs 20 .
In effect, then, we have three choices when faced with the kind of causal
exclusion scenarios discussed here.
(1) Discredit the supervenient entity as cause.
(2) Discredit the subvenient entity as cause.
(3) Accept causal overdetermination; the existence of more than one sufficient
cause for a given effect.
My claim is that if the right kind of realization relation obtains between mental
entities and their physical realizers, then an explanation of why this necessitation
relation holds will also explain why causal overdetermination by mental entities and
their realizers can be acceptable. I spell out a framework within which we can give
such an explanation in the fourth paper.
Still, even if one accepts explainable causal overdetermination one can
distinguish between first and second grade ways of being causally responsible for an
effect. Laying down arguments supporting (1) above we get a range of views saying
that non-reducible higher-level events can be sufficient causes, but only in a weak
sense, they are only causal companions of their more fundamental lower-level
subvenient events. On the other hand, arguments intended to establish (2) give a
range of views according to which the supervenient events are first-grade causes of
given effects because they are proportional to those effects, or better correlated with
those effects, or are minimal sufficient causes relative to those effects. One important
19
With the proviso that Yablo denies competition for causal influence between determinables and
determinates.
20
Notice, however, that Yablo distinguishes between competition for causal influence, which he
denies, and competition for being the cause, which he acknowledges. Whether the other accounts
mentioned above conflicts with the causal closure principle will depend on what version of that
principle one accepts.
The Metaphysics of Mental Causation
19
virtue of the latter view, compared to (2), is that it pays respect to the principle of the
causal closure of physics. Although the supervenient cause is a minimal sufficient
cause of the effect, the subvenient cause is still causally sufficient for the effect. Thus,
the causal self-sufficiency of physics still holds. This result requires that the causal
self-sufficiency principle is not formulated in terms of minimal sufficient causes21 .
It’s time for a few summarizing remarks. If we adopt a non-reductive
physicalist position, which essentially incorporates the claim that mental events are
realized by, but not identical to, physical events, we have the following options. (i)
We can explain the possibility of mental causation in a weak sense if we accept
causal overdetermination. (ii) We can explain the possibility of mental causation in a
robust sense if we find it plausible that mental causes are better correlated with,
proportional to, or minimal relative to their alleged effects. (iii) We can explain
robust mental causation and pay respect to the principle of the causal self-sufficiency
of physics if we both accept causal overdetermination and are able to argue that
mental causes can be minimal sufficient causes for physical effects in the presence of
their causally sufficient physical realizers.
5. An Obvious Reply and a Not-so-obvious Response: The
Nomological Determination Argument
As discussed in the previous section, the causal exclusion argument can be answered
by clarifying its premises and revealing implicit assumptions about causation on
which it relies. This gives room for interesting non-reductive accounts of macrocausation in general, and of mental causation in particular. However, there is another
argument that maintains much of the spirit of the causal exclusion argument but
focuses on nomological determination rather than causation. This argument blocks
21
When we distinguish between sufficient and minimal sufficient causes, we could accept a causal
self-sufficiency principle for physics proclaiming that all physical effects that have a sufficient cause at
a time has a sufficient physical cause at that time, without thereby committing ourselves to the
existence of a minimal sufficient physical cause at that time. See the second paper for a detailed
discussion.
Introduction
20
the kind of response discussed in the previous section. We get the argument by
replacing the causal closure principle in the Generalized Exclusion Argument. The
new premise is:
Physical Determination: All physical events are fully determined by prior
physical events and the laws of nature.
The argument then reads 22 :
The Nomological Determination Argument
(i)
Non-Reductionism: mental phenomena in particular and higher-level
phenomena in general are not identical to physical phenomena.
(ii)
Physical Determination: all physical phenomena are fully determined by
prior physical phenomena and the laws of nature.
(iii) Mental and other higher-level phenomena do not merely overdetermine
physical phenomena.
(iv) From (i)–(iii): mental and other higher-level phenomena are superfluous
for the determination of physical phenomena.
In responding to this argument I propose a Shoemaker-inspired metaphysical account
of the realization relation between properties and between causal relata understood as
property instances. Consider the following visualization:
22
I discuss this argument in more detail in paper IV. See also [Kim 2005] especially pages 17–19 for
some considerations along similar lines. Note that the level-talk is slightly ambiguous. As I think of it,
micro-physical phenomena proper, i.e. micro-physical objects and their properties, are not realizers of
higher-level phenomena. Rather, the realizers of higher-level phenomena are macro-phenomena
individuated in terms of their micro-physical constituents. Consequently, the realizer-realized relation
does not track the constitutive relations between the levels of the micro-macro hierarchy. Rather, the
differences between realizers and the phenomena they realize are cashed out in terms of differences in
modal robustness, specificity, degree of determination etc.
The Metaphysics of Mental Causation
21
Fig.5a.
HL
Synchronic realization
MP
Diachronic determination
MP´
The horizontal arrow indicates a temporally diachronic determination relation
between MP (some microphysical phenomenon) and MP´ (some later occurring
microphysical phenomenon 23 ). The vertical arrow indicates a temporally synchronic
realization relation between MP and HL (some higher-level phenomenon realized by
MP). The dotted line represents the determination relation under present discussion.
The relevance of HL for MP´ depends on the kind of realization relation it
bears to MP. Since HL is synchronically necessitated by MP it qualifies as a
synchronic necessary condition for MP. It might do so in virtue of an unexplained
supervenience relation. On the other hand, it might also do so in virtue of being an
essential part of MP. In the fourth paper I spell out a view where realized propertyinstances are parts of their realizers. The way I do this is inspired by Shoemaker’s
account of property realization. On the view spelled out in paper IV, realizable
properties are sums of causal powers, and realized properties are proper parts of their
realizers. This understanding is used to elaborate an account where realizable causal
relata are qualitative parts of their realizers. The idea is that realized properties are
relevant for what their realizers determine in virtue of being qualitative parts of their
realizers.
I investigate this account in some detail in paper IV, but here is a brief
presentation of the idea of qualitative parthood among causal relata. When causal
relata are analyzed as property instances – as objects having properties at times
represented by [Object, Property, time] – qualitative parthood among causal relata can
be defined as:
23
‘Micro-physical phenomena’ is here meant to include macro-phenomena individuated in terms of all
their micro-physical constituents, so it is not micro in the mereological sense.
Introduction
22
Qualitative Parthood: [O, P, t] is a qualitative part of [O*, P*, t*] if and only
if O=O*, t=t*, and P* is a part of P.
Furthermore, property P* is a part of P if and only if the causal powers constituting P
are part of the causal powers constituting P* 24 .
Having sketched my positive account, I now turn to a worry discussed mainly
in the third paper. The worry concerns the ontological pluralism involved in the idea
that realizable causal relata and their realizers are different existents. How does this
claim fare when confronted with the response that such distinctions are merely
conceptual, and not reflective of metaphysical distinctions?
6. Anyway, is this really Metaphysics..? Reification and
Theory-World Projection
Questions that at bottom relate to the strategy of research, or to the logical relations between
sciences as constituted at a certain time, are commonly discussed as if they were about some
ultimate and immutable structure of the universe.
[Ernest Nagel in The Structure of Science page 364]
As discussed in section 4, the notions of proportionality, correlation and/or minimal
causal sufficiency can be used in replies to the causal exclusion arguments. They also
play an important role in the more technical discussions in the papers that follow.
Very roughly speaking I’ve given the following kind of response: (1) causation is a
modal notion; (2) the modal robustness of the cause is tuned to the modal robustness
of the effect; so modally robust higher-level causes can be causes in the presence of
their realizers; and (3) realizable causes are qualitative parts of their realizers so there
is no problematic overdetermination.
24
If P* is a realizable property it is identified with a sum of causal powers. However, if P* is not itself
a realizable property (and in that sense a fundamental property), P will be part of the sum of causal
powers bestowed by P*.
The Metaphysics of Mental Causation
23
I investigate whether there genuinely are higher-level causes and not the more
modest question whether higher-level causal explanations are heuristically useful.
Given the status quo of the special sciences the importance of such explanations is
beyond doubt. The worry has been that the seemingly all-embracing character of
modern physical science reveals a metaphysics that has no room for higher-level
phenomena like persons, minds, cells, etc. 25 Again we see the intuitive force of the
exclusionist line of reasoning: if the physical domain is causally closed, and
everything else depends on the physical, then reference to non-physical phenomena is
superfluous in giving a complete account of the workings of the world. Consequently,
non-physical phenomena have no role to play and should be metaphysically
discredited on pain of ontological extravagancy.
In response to this line of thought we’ve seen reasons to hold that higher-level
causes are genuine in virtue of being proportional to, better correlated with, and/or
minimal relative to their effects. This gives rise to a worry: are there really different
events corresponding to differences in how tightly we individuate causes? For
example, is something being red and something being scarlet two different events? Is
having an intention to act in a certain way different from being in a specific
neurological state that realizes having that intention? The answer to such questions
will depend on the background metaphysical theory. Moreover, the issues are
problematically entangled. Exclusionist considerations can be used to argue against
the ontological status of determinable and other realizable properties, and thereby
25
Whether this is regarded as a worry or nice prospect varies with who you are talking to. Allow me to
speculate a little on that note. If you have a strong pre-theoretical belief in scientific progress, in the inprinciple completability of physical theory, and maybe also in determinism, you would probably be
more likely to regard this as a nice prospect. This is in contrast to someone who believes in libertarian
free will, and has a concern in conserving the notions of responsibility and punishment. I guess
everyone is a little troubled by the idea that persons don’t exist, but there are different options for
avoiding this stark conclusion. One could, for example, believe in universal fusion and temporal parts.
In that way person-candidates will be available, namely fusions of temporal parts that themselves are
fully decomposable into purely physical parts. As I try to argue in this thesis, it does not follow without
further problematic assumptions from causal self-sufficiency and supervenience that higher-level
phenomena are causally inert. Getting clear on these issues is important because it shows that the
picture is not as polarized as it might seem at first glance. And that a proper account of realization, in
turn, might open the way for more sober reformations of our self-conception, and our
conceptualizations of fellow human beings and social institutions that rely on our self-understanding.
In this way a discussion of the technical-seeming issue of mental causation can have, or should have,
ramifications way outside the philosophical corridors.
Introduction
24
indirectly to argue against the ontological status of coarse-grained events. I address
these issues in the third paper in terms of a discussion of Yablo’s account of mental
causation.
The discussion so far in this introduction has been intended to give sufficient
background for reading the detailed discussions in the ensuing papers. It is also
intended to illuminate some of the connections between the themes and arguments of
the individual papers. The remaining sections of this introduction are intended to
clarify the use of some central concepts and the scope of my account. Sections 7–9
discuss the scope of the view, section 10 discusses different understandings of
reduction and section 11 discusses the concept of causation and causal relata. Section
12 provides a short summary of each paper.
7. Proportionality, Correlation and External Individuation
Cut the pie anyway you like, “meanings” just ain’t in the head!
(Hilary Putnam in Meaning and Reference)
So far we’ve discussed mental causation in light of the view that mental events have
physical necessitators. The arguments against the exclusionists were based on the idea
that the physical realizers can be too specific and therefore modally fragile and thus
less good cause-candidates than their supervenient siblings. This reasoning can also
be put to use in accounting for the causal status of externally individuated mental
events.
Externally individuated mental events are mental events that are partly and
essentially individuated in terms of their externally individuated content 26 . Externally
individuated content is content that depends on the make-up of the world external to
the body of the person who has a thought or concept with that content. The standard
example is from Putnam; see e.g. [Putnam 1973, 1975]. Oscar and Twin-Oscar are
intrinsically identical. However, Twin-Oscar was brought up on Twin-Earth, which is
26
One can think of events like the onset of a belief, the occurrence of a desire, the change in a belief
and so forth here.
The Metaphysics of Mental Causation
25
identical to Earth except for the fact that there’s no water on Twin-Earth. There is,
however, another substance XYZ that plays exactly the same role as water does on
Earth 27 . For this reason Twin-Oscar’s term ‘water’ refers to XYZ while Oscar’s term
‘water’, like ours, refers to H2O. Consequently, Oscar and Twin-Oscar might be
intrinsically identical but have different thoughts. For example, Oscar might have a
thought that there is H20 in the bottle, while Twin-Oscar – being in an intrinsically
identical state – has the thought that there is XYZ in the bottle. Or so the externalist’s
line of reasoning goes.
The externalist, then, makes more fine-grained distinctions between mental
states than someone who thinks that such differences can be fully accounted for in
terms of purely internal differences. Accordingly, the question arises whether such
fine-grained distinctions can make any causal difference. Allow me to suppose that
such fine-grained differences due to external individuation also extend to actions.
Then the action ‘reaching out for a bottle of H2O’ will be a different action from the
action ‘reaching out for a bottle of XYZ’. If such fine-grained events are included
among the relevant effects, it seems externally individuated differences between
mental events will make causal differences. Oscar’s belief that the bottle contained
H2O was partially causally responsible for him reaching out for a bottle of H2O, while
Twin-Oscar’s belief that the bottle contained XYZ was partially responsible for him
reaching out for a bottle of XYZ. Oscar was not reaching for a bottle of XYZ. TwinOscar was not reaching for a bottle of H2O. Accordingly, these are different actions
that have different causes.
When applying the earlier discussed requirements of proportionality and/or
maximal correlation, one has resources to argue that externally individuated mental
events are better cause-candidates than their more rough-grained intrinsic siblings 28 .
Elaborated accounts along these lines are given in [Yablo 1997] and [Williamson
27
It is of course rather strange to say that Oscar and Twin-Oscar can be intrinsically identical when
Oscar is composed of approximately 70% water and Twin-Oscar of approximately 70% XYZ. We can,
however, abstract away from that problem since nothing about the issue hangs on it.
28
And also better than their total realizers, which are conjunctions of purely internal and purely
external events/states. Williamson argues nicely for that claim in [Williamson 1998]. See also [Yablo
1997] for a nice discussion in terms of proportionality.
Introduction
26
1998, 2000]. I don’t discuss this issue in the individual papers, but I find it important
to point out that it can be dealt with by this kind of approach.
8. Different Kinds of Realizable Properties: Getting Clear on the
Scope of My View
In the fourth paper I spell out an account that explains how instances of realizable
properties can be causally efficacious in the presence of their realizers. But what
reasons do we have for thinking that this kind of realization is relevant for the mental
causation problem? And more generally, what kind of properties can be handled by
my account of realization?
Here are three examples of different kinds of realizable properties. The
diversity of such examples serves to make the claim that my account covers a wide
range of properties – a range that also can include mental properties – more
reasonable 29 .
ƒ
Functional properties
ƒ
Determinable properties
ƒ
Average properties
Functional properties are here broadly understood and will of course include mental
properties if functionalism as a theory of mind is correct. Functional properties are
properties that are definable in terms of their functional role. The functional role is
not solely characterized in terms of external input and output (i.e. perceptual and
other causal input and behavioral output). This is exactly the feature that enabled
functionalists to counter the standard arguments against behaviorism. The so-called
ramsification procedure provides a schema for giving functional definitions of mental
29
I’m not confident that this list of realizable properties is exhaustive. However, if other kinds belong
there it will only serve to broaden the scope of my account, at least in so far as we require that the
realizers necessitate the realized properties.
The Metaphysics of Mental Causation
27
predicates that are sensitive also to other mental states 30 . For our present concerns,
the crucial thing to keep in mind is that such functional definitions involve existential
quantification over properties. They are typically of the sort:
Functional Property: O has functional property F if and only if O has some
property X such that X plays functional/causal role CR.
The account of property realization spelled out in the fourth paper covers the relation
between a functional property F and its specific realizer/role-player R. Accordingly,
the causal workings of functional properties fall within the scope of my account.
Determinable properties are properties like red, color, speed, shape etc.
Properties that, on any occasion at which they’re instantiated, are accompanied by an
instance of a determinate property. Examples of such pairs of determinables and
determinates are 31 :
Determinable property
Determinate property
Red
Scarlet
Color
Blue
Speed
75 mph
Shape
Triangular
The standard explication of the determinable-determinate relation can be found in
W.E. Johnson’s Logic [Johnson 1921]. Notice that there are certain obstacles to
defining determinable properties functionally. One might think that a determinable
property could be defined as having some determinate property X such that X
satisfies Ψ, where Ψ could be a functional/causal role. However, mathematical
properties might be determinables, and it is in no way clear that their specific
determinates play any causal role whatsoever. The modest, and reasonable, view is
30
See for example [Lewis 1983].
I use the terms ‘red,’ ‘speed,’ etc. as shorthand for the property designators ‘being red,’ ‘having a
speed,’ etc.
31
Introduction
28
that these categories of realizable properties are separate categories, but that they do
overlap. Yablo’s view that mental properties relate to physical properties as
determinables do to determinates, represents an additional non-reductive view within
the scope of my account.
What I call average properties are less commonly discussed in philosophy, but
they are important in science 32 . What I have in mind are properties defined as the
average of a range of specific properties. Temperature in a gas is a good example.
Temperature in a gas is identified as the average kinetic energy of the molecules in
the gas. Two collections of molecules might have the same average kinetic energy,
while differing in the specific distribution of kinetic energies among their elements.
We can contrast this notion with the determinable-determinate conception. Talking
about temperature, a determinate temperature of exactly 70ºC could be a determinable
of the property designated by ‘having a temperature above 65ºC’. However, we do
not say that a maximally determinate temperature of exactly 70ºC has a specific
kinetic energy distribution KD1 as a further determinate. The fact that a specific KDN
gives rise to the relevant determinate temperature (70ºC) does not make it qualify as a
determinate of that temperature. However, it does qualify as a specific realization of
an average property.
I have presented these kinds of realizable properties – properties that have
other properties as necessitators – in order to make plausible the claim that my
account covers a fairly wide range of properties.
32
For what it’s worth; entering [“disjunctive properties” + science] in Google’s search engine gives
692 hits (23.04.2007), while entering [“average properties” + science] gives 89,300 hits (23.04.2007).
It is also worth mentioning that Frank Arntzenius and John Hawthorne discuss average properties from
a completely different direction [Hawthorne 2006, chapter 7].
The Metaphysics of Mental Causation
29
9. Why not Substantial Dualism?
I find dualism considerably less unbelievable once the materialist alternatives are clearly
articulated. In fact, most days of the week I’m a dualist myself.
But in today’s climate defending dualism is a Herculean, not to say Quixotic, task.
(Dean Zimmerman 2003)
How much of a dualist is one allowed to be if one wants to give a plausible account of
mental causation and one wants to pay respect to the central tenets of the modern
naturalistic worldview? In order to get clear on the range of different non-reductive
positions that can account for mental causation, it will benefit proceedings if we
understand why more radical forms of dualism are doomed to fail in that endeavor.
Let us call someone who denies that mental events have physical necessitators
a substantial dualist 33 . This kind of substantial dualism is quite a strong position. It is
stronger than the view that the mental is metaphysically independent of the physical.
Recall the brief discussion of Van Gulick’s claim regarding the metaphysical
independence of higher-level patterns in section 2. All that is needed for metaphysical
dependence to fail is the existence of a metaphysically possible world where there are
mental phenomena but no physical phenomena. However, the lack of physical
necessitators requires there to be a possible world that is physically identical to the
actual world, but that lacks at least some mental phenomena that occur in the actual
world. Chalmers-style Zombie worlds would be an example 34 .
The difference can be put in terms of different ways of denying metaphysical
mind-body supervenience. Metaphysical mind-body supervenience can be understood
as the combination of two claims: (1) All metaphysically possible worlds that have
mental phenomena also have physical phenomena. (2) All metaphysically possible
worlds that are identical to the actual world in all physical respects are identical also
in all mental respects. Van Gulick suggested denying (1), which amounts to denying
33
Not to be confused with substance dualism. A substantial dualist might be a substance dualist, but he
might also be a property dualist who denies that the mental features of a world are necessitated by the
physical features of that world.
34
See David Chalmers The Conscious Mind [Chalmers 1996], especially chapter 4.
Introduction
30
metaphysical dependence. A substantial dualist, as I define him, is a denier of (2). For
the substantial dualist, the mental features of this world are not metaphysically
necessitated by the physical features of this world. The question, then, is whether this
claim makes the substantial dualist incapable of giving an account of mental
causation.
Assuming that the physical domain is causally self-sufficient, the unavoidable
overdetermination by sufficient physical causes and mental causes seems far less
plausible on this view. The reason is that such overdetermination would be analogous
to standard cases of causal overdetermination, like firing squad cases, where the
overdetermining causes are, or at least can be, independent. The consequence that all
instances of mental causation involve inexplicable overdetermination reveals a
critical instability in positions of this kind. The natural response on behalf of a dualist
is to explain the overdetermination, or try to dissolve his commitment to it. The
explanation of mental-physical causal overdetermination that my non-reductive
physicalist can put forward in terms of the realization relation that obtains between
the overdetermining causes is unavailable to the substantial dualist. Arguably, the
only two options available to the substantial dualist for explaining the
overdetermination are to embrace epiphenomenalism for mental events or reject the
principle of the causal self-sufficiency of physics. Both alternatives come at a high
cost. Epiphenomenalism for mental events runs in the face of our self-conception as
causal agents acting in virtue of mental states and events, like the having of a belief
and the onset of a desire. To reject the causal self-sufficiency of physics is in effect to
deny the in-principle completability of physical theory, without strong independent
argument that commitment is unwarranted in light of contemporary science 35 .
35
John Dupré explicitly denies the causal self-sufficiency (or causal completeness in his lingo) of
physics; according to him there is “no plausible ground for the belief in causal completeness” [Dupré
2001, page 163]. Moreover, he reveals a totally different (compared to what I expressed above)
understanding of where the burden of argument is situated. According to him “the first step in the
argument is to insist that the onus of proof belongs with the determinist” [Dupré 2001, page 163]
where ‘determinist’ is a placeholder for ‘believer in causal completeness’. In my view the predictive
power inherent in modern physical theory provides sufficient support for the claim that the burden of
argument is on the person denying causal self-sufficiency. However, and as I pointed out earlier, the
plausibility of the causal self-sufficiency principle hangs on reading causal sufficiency weakly, i.e. not
as involving proportionality, maximal correlation, or minimality. I speculate here, but Dupré may think
that the burden of argument resides with the believer in causal self-sufficiency because, at least in part,
The Metaphysics of Mental Causation
31
It seems therefore, that a dualist of this brand has to accept one of the
following three controversial claims: (1) the physical domain is not causally selfsufficient; (2) mental events are causally redundant; or, without further explanation,
that (3) any effect of a mental cause is causally overdetermined by that mental cause
and an independent physical cause. This is in contrast to the non-reductionist who
believes in a metaphysical realization relation that explains the metaphysical
necessitation relation between physical and mental events. A moderate nonreductionist should, I claim, hold that the physical domain is causally self-sufficient,
mental events are not causally redundant and the causal overdetermination is
acceptable exactly because the metaphysical realization relation obtains 36 .
10. Terminological and Substantial Issues about ‘Reduction’
There has been a widespread misunderstanding of what reductionism is
that has been prevalent in philosophy of mind for too long.
(John Bickle in A conversation with John Bickle)
The conception of reduction found in philosophy of mind is not unified and clear cut.
Consequently, it might be open to question whether the view I suggest qualifies as
non-reductionist or not. It has, for example, been argued that supervenience itself
entails, or at least leads to, reductionism 37 . On the other hand, reductionism can be
thought of as essentially identity based, in the sense that to reduce one domain to
he thinks causal completeness entails a choice between reductionism and epiphenomenalism for
higher-level phenomena. He says: “In summary, then, causal completeness at the microlevel must
entail reductionism, at the very least in the sense of the supervenience of everything else on the
microphysical. And even supervenience, I claim, is sufficient to deny any real causal autonomy to
higher-structural levels.” [Dupré 2001, page 162] An argument concluding with a stark choice between
a sweeping reductionism and all-embracing epiphenomenalism for all higher-level phenomena
reasonably leads one to question the premises of that argument. In Dupré’s case the radical conclusion
of this kind of causal exclusion argument backfires on the causal completeness/self-sufficiency of
physics. In my view, on the other hand, the exclusion argument diffuses in several ways, and does not
yield the stark conclusion Dupré seems to take for granted.
36
Even an explanation of the necessitation relation, like the one given in paper IV, seems required to
convince the dedicated exclusionist.
37
See footnote 35 above, where Dupré expresses this idea. Kim has also argued, though he later gave
up the idea, that supervenience entails reductionism [Kim 1978].
Introduction
32
another is to establish identities between the phenomena in those domains. What
about the view I suggest here – the view that mental properties are parts of physical
properties (or of the sums of causal powers bestowed by physical properties) – is it
really not reductionistic? Have I been under the spell of a profound and widespread
misunderstanding of what reductionism is?
If the reduction of one domain of properties to another domain of properties
requires establishing identities between the properties in the first domain and
properties in the second domain, then my view is clearly not reductionist. It is by
acknowledging this conception of reduction that I describe my view as non-reductive.
However, contemporary reductionists might respond that this is too strong a
conception of reduction. Moreover, they might respond that it is a conception of
reduction that is problematically detached from actual scientific practice. In this
section I will look at two views on reduction that focus on theory-reduction and
reductive explanation. It is not necessarily the case that the kind of ontological nonreductionism for realizable higher-level phenomena that I favor entails the
impossibility of, say, explaining or predicting higher-level phenomena in terms of
lower-level phenomena. I will briefly discuss such responses in this section, with a
view to clarifying the strength of my claims to be defending a non-reductionist
position. I’ll take a brief look at Ernest Nagel’s theory of theory-reduction, and John
Bickle’s “ruthless” reductionism 38 .
Nagel distinguishes two kinds of reductions: homogeneous reductions and
inhomogeneous reductions. In homogeneous reductions, all the important terms in the
reduced theory are either present in or explicitly definable by the terms in the
reducing theory. This is not the case in inhomogeneous reductions, which, for that
reason, require so-called bridge laws. The nature of bridge laws is expressed by Nagel
in The Structure of Science. Here, what he calls the ‘assumptions’ are the bridge laws;
‘B’ is a theoretical expression in the primary or reducing theory; while ‘A’ is an
expression in the reduced theory.
38
See especially Ernest Nagel’s The Structure of Science [Nagel 1979] and John Bickle’s Philosophy
and Neuroscience: A Ruthlessly Reductive Account [Bickle 2003]
The Metaphysics of Mental Causation
33
The assumptions then are physical hypotheses, asserting that the occurrence of
the state of affairs signified by a certain theoretical expression ‘B’ in the primary
science is a sufficient (or necessary and sufficient) condition for the state of
affairs designated by ‘A’. [Nagel 1979, page 354]
It is important that Nagel does not require the bridge laws to be biconditionals 39 . This
is important because it has been a widespread conception that Nagel-reductions
require biconditional bridge laws. Just look at what Kim says when he discusses
reductionism in philosophy of mind:
Standardly, these correlating bridge laws are taken to be biconditional in form
providing each property in the domain of the theory to be reduced with a
nomologically coextensive property in the reduction base. For mind-body
reduction Nagel’s model requires that each mental property be provided with a
nomologically coextensive physical property, across all species and structure
types. This has made mind-body reductionism – in fact all reductions – an easy
target. [Kim 1998, page 26]
Reasonably, if one drops the requirement of biconditional bridge laws, the prospects
for carrying out reductions will be better. However, derivability of the reduced theory
from the reducing theory plus the bridge laws is a necessary and sufficient condition
for Nagel-reduction, so the question is whether multiple realization is a hindrance to
derivability 40 . These questions have been the subject of debate, and I will not attempt
39
Also in his later article “Issues in the Logic of Reductive Explanations” Nagel allows for conditional
bridge laws, he says: “(…) bridge laws are empirical hypotheses concerning the extensions of the
predicates mentioned in these correspondence rules – that is, concerning the classes of individual
things or processes designated by those predicates. An attribute of things connoted by a predicate in a
reduced law may indeed be quite different from the attribute connoted by the predicates of the reducing
theory; but the class of things possessing the former attribute may nevertheless coincide with (or be
included in) the class of things which possess the property specified by a complex predicate in the
reducing theory.” [Nagel 1998, page 914] Nagel does require the laws of the reduced theory to be
derivable from the reducing theory; biconditional bridge laws would ensure derivability but they are
not necessary. See for example Robert Richardson’s “How not to Reduce a Functional Psychology”
[Richardson 1982] for a discussion of conditional versus biconditional bridge-laws.
40
Nagel clarifies his view in a footnote in The Structure of Science: “(…) the linkage between A and B
is not necessarily biconditional in form, and may for example be only a one-way conditional: If B, then
A. But in this eventuality ‘A’ is not replaceable by ‘B’, and hence the secondary science will not in
general be deducible from a theory of the primary discipline. Accordingly, even if we waive the
question whether a reduction is satisfactory when achieved by augmenting the theory of the primary
science by a new postulate L´ which is empirically confirmed but may contribute next to nothing to the
explanatory power of the initial theory, connectability does not in general suffice to assure derivability.
On the other hand, the condition of derivability is both necessary and sufficient for reduction, since
derivability obviously entails connectivity. The condition of connectability is nevertheless stated
separately, because of its importance in the analysis of reduction.” [Nagel 1979, page 355]
Introduction
34
to determine whether Nagel’s account is compatible with certain kinds of multiple
realization here 41 . Of course, if Nagel-reduction requires biconditional bridge laws
multiple realization rules it out effectively. In that case it is not a viable alternative to
my view. In particular, Nagel reduction of psychology to physical theory will not be
required for a viable account of mental causation.
However, it is important to recognize that there are weaker accounts of
reduction – historically true to Nagel’s own account or not – that can accommodate
multiple realization. Let’s turn to one such contemporary account, namely John
Bickle’s.
At least at one point Bickle and Nagel agree; reductions are explanations, or
collections thereof. As Nagel states it:
Reduction, in the sense in which the word is here employed, is the explanation of
a theory or a set of experimental laws established in one area of inquiry, by a
theory usually though not invariably formulated for some other domain. [Nagel
1979, page 338]
But what are reductions explanations of? For Bickle they are explanations of
phenomena within the domain of the theory to be reduced. For Nagel, on the other
hand, they are explanations of the laws of the reduced theory. In this sense, Bickle’s
view is weaker than Nagel’s. It doesn’t require derivability of the laws of the reduced
theory. If a reducing theory explains all the laws of the reduced theory (aided by
bridge laws) then it will also explain the range of phenomena explainable by the
reduced theory. The converse, however, need not be the case. A science is Bicklereducible if the phenomena constituting its domain of interest can be explained by, for
example, lower-level mechanisms dealt with by a lower-level science. This, however,
does not entail that the laws of the reduced field are explained; they might be, or they
might be reformed, or they might be eliminated on pain of redundancy.
For our concerns, it is important to point out that a proper evaluation of a
Bickle-style reductionistic program will depend on one’s precise notion of
41
Some relevant discussion of reduction and Nagel’s account of reduction, especially as it pertains to
biology, are; [Hull 1974], [Kitcher 1980], [Richardson 1979, 1982], [Ruse, 1974], and [Schaffner
1967, 1974].
The Metaphysics of Mental Causation
35
explanation. It will also depend on how one individuates the objects of explanation 42 .
Depending on how finely or roughly one individuates the explanandum, the concerns
of minimality, proportionality and correlation might favor explainers at different
levels. The reductionist will therefore be committed to certain constraints on the
individuation of the explanandum. Bickle, for example, individuates actions as
precisely described bodily movements.
The view I propose here might actually be compatible with a Bickle reduction
of mentality understood in this way. Whether a Bickle reduction of psychology to
neurophysiology is possible is, at least partly, an empirical question, and the general
metaphysical account I give is not committed on this question. However, if such a
reduction turns out to be impossible, my framework can explain how these nonreducible phenomena can play a causal role in the presence of their realizers. The
issue depends on what kind of explanandum one finds scientifically legitimate.
The argument against Kim that I set out in the first paper attacks the very
strong reductive claim Kim makes about identities between mental properties and socalled micro-based properties based at the fundamental physical level. One might
accept my argument against that strong claim, while still holding that some, or all, of
the phenomena dealt with in higher-level psychology can be Bickle-reducible to, say,
cellular and molecular neuroscience, i.e. can be explained by a lower-level science.
What stance one takes on this question depends on what requirements one puts on
scientific explanations. And, importantly, on what one takes to be the legitimate
objects of scientific explanation.
42
See my “A conversation with John Bickle” for a discussion of this point [Strand 2007]. It becomes
particularly salient in light of the earlier discussion of minimality, proportionality and correlation.
Introduction
36
11. ‘Causation’ in the Mental Causation Debate
The law of causality, I believe, like much that passes muster among philosophers,
is a relic of a bygone age, surviving, like the monarchy,
only because it is erroneously supposed to do no harm.
(Bertrand Russell On the Notion of Cause)
In contrast with Russell, contemporary philosophers of mind seem to find causation
as much of a core notion as ever. Causal theories of perception, of reference, etc. are
popular, and the mental causation problem has perplexed philosophers of mind for
quite some time now. But however assiduous the search for a reductive analysis of
causation has been, it has not yet proved succesful. Moreover, a suspicion that such an
analysis is unavailable is increasingly being aired 43 . Even if the terrain is messy – or
just because the terrain is messy – a few clarifications of my understanding of
causation are in place.
I start out by highlighting the idea that properties play a crucial role: that a
causal explanation is explanatory only if it leads us to see what aspect, feature or
property made the cause bring the effect about. Typically, causes are efficacious in
virtue of their properties, in virtue of their speeds, masses, charges, colors, shapes,
structures etc. This point is reflected in how different sciences present both actual and
hypothesized causal connections. I’ll give a couple of examples.
I take the first from a standard physiology textbook Human Physiology The
Mechanisms of Body Function by Vander, Sherman and Luciano. They note the fact
that axons can regenerate in the peripheral nervous system, something which does not
occur in the central nervous system 44 :
In contrast, severed axons within the central nervous system attempt sprouting,
but no significant regeneration of the axon occurs across the damaged site, and
there are no well-documented reports of significant function return. Either some
basic difference of central nervous neurons or some property of their
43
The collection Causation and Counterfactuals [Collins, Hall and Paul 2004] gives a nice overview
of the present state of the field.
44
An axon, sometimes also called a nerve fiber, is an appendage to the neuron which transmits
electrical signals from the neuron.
The Metaphysics of Mental Causation
37
environment, such as inhibitory factors associated with nearby glia, prevents
their functional regeneration. [Vander, Sherman and Luciano page 181, my
italics]
As they point out in the italicized text, when we look for causes of this observed
phenomenon we look for differences in internal or external properties. Properties are,
so to speak, the locus of causal explanatory interest.
Here is another example, this time from the field of psychoacoustics. The
quote is from the textbook The Science of Sound by Rossing, Moore and Wheeler.
The ability to distinguish between two nearly equal stimuli is often
characterized, in psychophysical studies, by a difference in limen or justnoticeable difference (jnd). Two stimuli will be judged the same if they differ by
less than the jnd.
The jnd for pitch has been found to depend on the frequency, the sound level,
the duration of the tone, and the suddenness of the frequency change. It also
depends on the musical training of the listener and to some extent on the method
of measurement. [Rossing, Moore and Wheeler, page 123]
So whether a subject can perceive a difference in pitch depends causally on the
properties of the sound, and of the auditory abilities/properties of the subject. Again
we see how properties are the locus of causal explanatory interest.
These examples support the common conception that causal relata are
something akin to property exemplifications. Here’s what Chris Swoyer says in his
entry on properties in the Stanford Encyclopedia of Philosophy:
(…) it is worth noting that it is never a single, undifferentiated amorphous blob
of an object (or blob of an event) that makes things happen. It is an object (or
event) with properties. Furthermore, how it affects things depends on what these
properties are. The liquid in the glass causes the litmus paper to turn blue
because the liquid is an alkaline (and not because the liquid also happens to be
blue). The Earth exerts a gravitational force on the moon because of their
respective gravitational masses. [Swoyer 2000, page 18]
Statements like this are not hard to find, and it is safe to say that the standard view is
that causal relata are individuated, at least partly, in terms of the properties they
instantiate or are instances of.
Introduction
38
Another important feature of causation that I put to use in this thesis is that
causal relations, in general, involve a component of counterfactual dependence.
While this focus does not involve a commitment to a counterfactual analysis of
causation it does play a crucial role in the replies to the causal exclusion argument
discussed in section 4 of this introduction.
The notion of a minimal sufficient cause, which I put to use in paper II, says
that a sufficient cause for an effect is minimal if it does not necessitate other
simultaneous sufficient causes for that effect. The intuitive idea is that a minimal
sufficient cause is minimal in that it does not include any causally irrelevant parts or
aspects. Here is one way of illustrating the distinction between a minimal sufficient
cause for E and a simultaneous cause that is sufficient for E but not minimal. Suppose
that C is a sufficient cause for E and that C* has C as a proper part. Reasonably then,
C* is causally sufficient for E, but not minimal. In the same way, if an effect has a
non-minimal sufficient cause C*, then it will be possible to isolate parts or aspects of
C* that are irrelevant for the causing of C. The cause-candidate that is C* minus these
irrelevant parts will then be a minimal sufficient cause of E.
However, as I discussed in section 5 and which is a theme in the fourth paper,
the counterfactual dependence-based replies to the Causal Exclusion argument can be
sidestepped by invoking the Nomological Determination Argument. Answering that
problem therefore requires another approach, as we have seen, and as is elaborated in
paper IV.
12. Précis of the Individual Papers
In the paper “Immense Multiple Realization” I argue that Jaegwon Kim is committed
to identities between all causally efficacious macro-properties – mental properties
included – and so-called micro-based macro-properties based at the fundamental
physical level. This commitment stems from his response to the generalization
argument, which depends on the availability of such identities. This commitment,
however, turns macro-causal relata into very fragile entities; fragile in the sense that
The Metaphysics of Mental Causation
39
the slightest change in some microphysical detail amounts to a change in the macrocausal relata itself. Given this feature, Kim’s account fails to preserve mental
causation as we know it because the counterfactual dependencies naturally backing
up macro-causal claims will be of a radically different nature than commonly
conceived. Unless we are willing to buy into such a revision of our understanding of
macro-causation, we should be suspicious of reductionism as an answer to the
generalized causal exclusion worry.
This finding sparks off a critical scrutiny of the causal exclusion argument, a
task I undertake mainly in the second paper “Causal Exclusion and the Preservation
of Causal Sufficiency”. I argue that causal overdetermination, in the sense of effects
having more than one sufficient cause at a time, is frequent also within the physical
domain. I then attempt to distinguish between acceptable and unacceptable causal
overdetermination. The main idea is that causal overdetermination is acceptable
whenever we have a satisfactory explanation of its occurrence. An unexplained
supervenience relation, for example, does not explain why there are two causes – the
subvenient entity and the supervenient entity – for a given effect. What is required is
a philosophical account that underwrites the supervenience, and thus explains why the
overdetermination cases occur. I give such an account in paper IV. In the second half
of paper II I discuss the principle of the causal closure of physics. I argue that the
distinction between sufficient causes and minimal sufficient causes calls for a greater
level of precision in the discussion and that the most plausible versions of the causal
closure principle are compatible with the causal workings of higher-level entities.
In paper III “Proportionality and the Metaphysics of Causation” I discuss
Yablo’s account of mental causation. My main concern is to investigate the interplay
between a Yablo-style account of mental causation, and metaphysical pluralism for
causal relata. If metaphysical pluralism, in the sense of co-occurring events related by
a determination relation, is true, then Yablo’s proportionality principle is a good
guide for singling out the relevant cause. However, one might question such
pluralism, and consequently deny that there is a non-trivial metaphysical reading of
the proportionality principle. I contrast Yablo’s view with such an alternative, and
point out that these options should be evaluated also on other merits than how they
Introduction
40
account for mental causation. In discussing the issue I provide an argument for the
existence of determinable causal relata that is based on accepting a non-trivial
proportionality principle. I also point out certain problems for the alternative to the
pluralistic view.
In the fourth paper “Fleshing out the Workings of Realizable Properties” I
formulate the Nomological Determination Argument in order to cash out the aspect of
the exclusion worry that seems to be immune to counterfactual dependence-based
responses. I suggest a metaphysical account of property realization, and put this
account to use in answering this aspect of the exclusion worry. The suggested
account of realization is inspired by Shoemaker’s, but is formulated in terms of a
mereology for properties. I also criticize an account of property realization that is
based on a metaphysical understanding of the first-order second-order relation.
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43
PAPER I
Immense Multiple Realization℘
Anders Strand
ABSTRACT
In his latest book Physicalism, or Something near Enough, Jaegwon Kim argues that his
version of functional reductionism offers the most promising way of saving mental
causation. I argue, on the other hand, that there is an internal tension in his position.
Functional reductionism does not save mental causation if Kim’s own supervenience
argument is sound. My line of reasoning has the following steps: (1) I discuss the
supervenience argument and I explain how it motivates Kim’s functional reductionism; (2)
I present what I call immense multiple realization, which says that macro-properties are
immensely multiply realized in determinate micro-based properties; (3) in view of which I
argue that functional reductionism leads to a kind of irrealism for mental properties.
Assuming that Kim’s view partakes of such irrealism, which Kim himself seems to
acknowledge, I argue that his position gets the counterfactual dependencies between macrocausal relata wrong, and, consequently, that it does not give a conservative account of
mental causation. I end the paper with a discussion of some alternative moves which Kim
seems to find viable in his latest book. I argue on the assumption that the supervenience
argument is sound, so my discussion provides additional reasons to critically reevaluate that
argument because it generalizes in deeply problematic ways.
1.
2.
3.
4.
5.
6.
7.
℘
Introduction
Causal Exclusion and Kim’s Functional Reductionism
Immense Multiple Realization (IMR)
Can Micro-based Properties figure in Macro-Causal
Relations?
Token Identity between Instances of Functional Properties
and their Realizers
Mental Properties as Coarse-grained Physical Properties
Conclusion
Thanks to Øistein Galaaen, Carsten Hansen, Brian McLaughlin, and to the audience at the ECAP 5
conference in Lisbon, August 2005, where I presented an earlier version of this paper.
Paper I
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1. Introduction
The view that the mental is dependent on but not reducible to the physical has been
the received view for the last 35 years or so; it is known as non-reductive
physicalism. In analogy with the Cartesian interaction problem, non-reductive
physicalism has some problems with accounting for mental causation. One of these
problems is strikingly brought to the surface by the so-called causal exclusion
argument. Given certain assumptions, non-reducibility leads, it is argued, to
epiphenomenalism for mental properties. Jaegwon Kim’s supervenience argument
is perhaps the most influential version of this argument [Kim 1998, Kim 2005
chapter 2].
Kim argues that non-reducible mental properties are causally excluded by
their subvenient physical properties. On the other hand, we have very strong reasons
for believing in mental causation, so an imperative philosophical task follows in the
wake of Kim’s argument. I call this the mental causation challenge.
The Mental Causation Challenge. If the supervenience argument is sound,
how is mental causation possible?
In this paper I discuss whether Kim’s functional reductionism really gives a
satisfying answer to this challenge.
I start by briefly discussing the supervenience argument and functional
reductionism in order to show that the scope of the proposed reductions is quite
extreme. It turns out that Kim, to avoid a vicious generalization of the
supervenience argument, is committed to reduction base properties based at the
fundamental physical level. I then present the phenomenon of immense multiple
realization (IMR). (IMR) consists in ordinary macro-properties being immensely
multiply realized by properties based at the fundamental physical level. I go on to
discuss the prospects for a reductionist answer to the mental causation challenge.
Immense Multiple Realization
49
There are three reductive strategies for dealing with mental properties, all of which
are discussed by Kim in his latest book [Kim 2005].
(1) Renounce the idea that mental properties are genuine properties and
rephrase talk of mental properties with talk of mental predicates or
property designators.
(2) Identify instances of higher-order mental properties with instances of
physical properties.
(3) Identify mental properties with first-order physical properties.
Kim himself seems to accept (1). He is clearest on this in Mind in a Physical World
where he repeatedly brings this view up:
So it is less misleading to speak of second-order descriptions or designators of
properties or second-order concepts, than second-order properties. [Kim 1998,
page 104]
In short, multiply realizable properties are causally and nomologically
heterogeneous kinds, and this at bottom is the reason for their inductive
unprojectibility and ineligibility as causes. I believe these considerations
strengthen the case made earlier for eschewing the talk of functional properties
in favor of functional concepts and expressions. [Kim 1998, page 110]
(…) multiply realized properties are sundered into their diverse realizers in
different species and structures, and in different possible worlds. To those who
want to hang onto them as unified and robust properties in their own right, this
no doubt comes as a disappointment. But I believe that the conclusion to which
we have been led is inescapable, as long as we accept the causal inheritance
principle and seriously believe in multiple realization. [Kim 1998, page 111] 1
1
Kim’s causal inheritance principle reads: Each instance of M (a realizable property) has exactly the
causal powers of its realizer on that occasion. See [Kim 1998 page 110, Kim 1992 page 18]. This
principle is not uncontroversial, see for example [Shoemaker 2003] for a position that denies the
causal inheritance principle thus formulated. As we will see in section 4 of this paper, the patterns of
counterfactual dependence that involves an instance of a realized property might differ from the
patterns of counterfactual dependence involving the instance of its specific realizer on that occasion.
The existence of such cases would provide reasons to question the causal inheritance principle.
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This view surely has some disappointing consequences; it is hard to see how its
eliminative aspect can be reconciled with the claim that functional reductionism
saves the causal efficacy of mental properties. That disappointment, however,
might have been something we just had to accept, had it not been for a further
problem besetting this view.
In section 4 of this paper I argue that Kim gets the counterfactual
dependencies between macro-causal relata wrong. Allow me to formulate this a
little more precisely. In light of immense multiple realization, Kim’s view deviates
problematically from the standard common-sense and special science understanding
of macro–causal relations. The argument for this claim is the main contribution of
this paper. It is spelled out in sections 3 and 4. In sections 5 and 6 I argue that a
retreat to options (2) or (3) above is unavailable on the assumption that the
supervenience argument is sound. My argumentative strategy in sections 5 and 6
involves reiterating the supervenience argument against the different available
reduction bases. This gives a new argument against disjunctive properties, while the
brief argument against (2) above is similar to arguments given by Terence Horgan
and Sydney Shoemaker [Horgan 1997, Shoemaker 2003]. I end the paper by briefly
discussing an essence-based, or minimal, understanding of physical reduction bases
in section 6.
2. Causal Exclusion and Kim’s Functional Reductionism
A strong desideratum for most philosophers in the mental causation debate is to
reconcile physicalistic commitments, like the causal closure of the physical domain
and mind-body supervenience, with robust mental causation. Robust mental
causation can be contrasted with weaker notions like causal relevance, program
explanation [Jackson & Pettit 1990] and supervenient causation [Kim 1984].
Naively put, mental causation should be genuine causation. Kim thinks his
functional reductionism is the best way of reconciling these desiderata [Kim 2005,
page 148].
Immense Multiple Realization
51
Kim arrives at his functional reductionism mainly out of a concern for
mental causation. The reason he finds functional reductionism attractive in this
respect is twofold [Kim 1998, Kim 2005]. Firstly, he thinks non-reductive
physicalism is unable to explain robust mental causation. 2 Secondly, he argues that
functional reductionism is able to explain this by, as he puts it, “preserving the
mental as part of the physical domain” [Kim 1998, page 120]. The supervenience
argument is used to establish the first part, while the second part has three core
elements: (i) show that mental properties really are functionalizable; (ii) show that
functional reductions really answer explanatory questions; and (iii) show that
functional reductionism really answers the mental causation challenge. My focus is
on (iii) in this paper. Kim’s answer, roughly put, is to locally identify mental
properties with their physical realizers. Local contingent identity claims of this sort
are possible because functional descriptions are non-rigid designators. 3
The supervenience argument, or causal exclusion argument, can be
understood as a reductio against non-reductive physicalism in conjunction with
three other widely held claims. More precisely, it says that the following four
claims are incompatible.
1. Non-Reductive Physicalism: Mental properties supervene on but are not
identical to physical properties.
2. Mental Causation: Mental events are causally efficacious in virtue of their
mental properties.
2
He also argues that substance dualism is unable to answer the mental causation challenge [Kim
2005 chapter 3, Kim 2001]. The contrast between reductionism and non-reductionism as the
concepts are used here is between property identity theories and property dualist (or pluralist)
theories. Eliminativism is the rejection of reductionism and dualism (/pluralism).
3
Non-rigid property designators pick out different properties on different occasions (or in different
worlds). One example of a non-rigid property designator is ‘the color of Kim’s bike’. If we suppose
that mental property designators are non-rigid, we’ve already bought into a weak kind of irrealism
for mental properties. It is not one unique mental property corresponding to a non-rigid mental
property designator, because if there were such a property the designator would indeed be rigid. On
the other hand, it might be the case that a non-rigid mental property designator picks out different
mental properties on different occasions (at different worlds). The question of how much reformism
is involved here deserves more attention.
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3. Exclusion Principle/No Causal Overdetermination: Physical effects that
have mental causes are not causally overdetermined (except for rare cases of
acceptable overdetermination).
4. Causal Closure of the Physical Domain: Every physical effect that
has a sufficient cause at a time has a sufficient physical cause at that
time.
The question whether these claims are compatible has been widely discussed, and
one could reasonably claim that it states the core of the mental causation problem.
Illuminating contributions are e.g. [Burge 1993], [Kim 1998], [Kim 2005], [Rudder
Baker 1993], [Sturgeon 2000], [Van Gulick 1993], and [Yablo 1992]. I will not
examine this discussion in detail. It will suffice for my present concerns to briefly
explain how Kim’s argument is supposed to work.
As mentioned, Kim presents it as a reductio against non-reductive
physicalism. The argument specifically targets the non-reductive claim that mental
properties supervene on physical properties without being identical to those
physical properties. The crux of Kim’s argument is that there is no causal work left
to do for the instantiations of mental properties. Assuming claim 3 and 4 above, we
know that every physical effect that has a sufficient cause has a sufficient physical
cause, and that physical effects that have mental causes are not causally
overdetermined. This contradicts mental causation, because mental properties turn
out to be superfluous for the unfolding of the causal nexus of physical events.
Assuming that the argument is valid, we have the options of rejecting one or
more of the above claims. Eliminativists and reductionists 4 reject non-reductive
physicalism; epiphenomenalists reject mental causation; many non-reductive
physicalists accept causal overdetermination; and some non-reductive physicalists
and substance dualists reject the causal closure of physics.
4
I think of reductionism as identity based, i.e. that it amounts to the claim that mental properties are
identical to physical properties.
Immense Multiple Realization
53
Kim himself opts for reductionism. It is important to be aware that the
properties in the reduction base for an identity based reductionism must be at the
same level as the properties to be reduced. This means that the base property must
be instantiated by the same objects as the reducible property. Reasonably; if two
properties are identical they are instantiated by the same objects. Kim suggests that
the properties in the reduction base will be so-called micro-based macroproperties.
P is a micro-based property just in case P is the property of being completely
decomposable into nonoverlapping proper parts, a1, a2,…, an, such that P1(a1),
P2(a2),…, Pn(an), and R(a1,…, an). [Kim 1998, page 84]
The central feature of these properties is that they are specified in micro-terms. I
think Kim ultimately has, and must have, micro-physics in mind. A property being
micro-based can be understood as the metaphysical analogue to being specified in
micro-terms. A property of a whole can, for example, be specified in terms of its
parts, their properties and the relations between them. Analogously, a property of a
whole can be based at a lower level, namely the level of its parts, their properties
and the relations between them. Such a micro-based property does not, however,
belong to the lower level. It is still a macro-property in the sense that it belongs to
the whole object, and not to proper parts of that object. This is Kim’s notion of a
micro-based macro-property. Assuming this picture we can state the conclusion of
the supervenience argument (CSA) as a dilemma:
(CSA) If the properties at a non-fundamental ontological level supervene on
properties based at a lower, causally more fundamental level, then they are
either identical to those micro-based properties or causally preempted by
them.
This is an entirely general conclusion. Kim’s reductive position is therefore not only
committed to identities between mental properties and micro-based physical
properties, but also to the claim that any broadly physical property (special science
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properties included) is identical to a micro-based physical property based at the
fundamental physical level. 5
Kim’s functional reductionism gives a three-step procedure for establishing
such identities [Kim 1998, pages 98–99 and 110–111]:
a) Give a functional (causal role) description of the property to be reduced.
b) Find the categorical realizer of the causal role (possibly restricted to a
certain kind of organism or context in order to answer multiple realization
worries).
c) Identify the property subject for reduction with the categorical realizer of its
causal role.
All three steps are of course in need of further clarification, and Kim has much
more to say about them, see [Kim 2005]. I focus primarily on whether the identities
envisioned in step c) are possible, and of what kind they might be. Even if it should
turn out, contrary to my arguments, that there are reduction base properties
available, there is still a question whether such identity claims would be well
founded. I will not deal with that question here; see e.g. [Horgan & Tienson 2001]
and [McLaughlin 2001] for discussion.
Another related issue is the claim that a functional construal of mental
properties is sufficient for reductive explanations. In other words, that one can give
reductive explanations of instantiations of functionalized mental properties by
explaining the instantiations of their realizers, see [Kim 2005, chapter 4] and [Kim
1998, pages 111–112]. 6 I think this latter claim has independent interest and
5
According to Ned Block, Kim’s view is subject to the following counterargument [Block 2003]: It
is a genuine metaphysical and scientific possibility that there is no lowest fundamental level of
reality, so our view on mental causation should not commit us on this open question. I think that
Kim is justified in claiming that he is not so committed. Even though he is committed to identities all
the way down he is not committed to the existence of a fundamental level. See [Kim 2003] for his
defense. This, however, does not alter the fact that he is committed to identities between macroproperties and micro-based properties based at the micro-physical level. Moreover, it would, as
Jonathan Schaffer argues, give the physicalist position less bite than ordinarily conceived. See
[Schaffer 2003] for a very nice discussion.
6
Kim asks [Kim 1998, pages 111-112], “Why does a system s instantiate M at t? Because it is
instantiating P1 at t, and P1 is a realizer of M in systems of the kind that s is (…)” adding, a little later
Immense Multiple Realization
55
deserves serious attention. Nonetheless, it is Kim’s metaphysical claims about
property identities that are the subject of the present evaluation, because they are
supposed to answer the mental causation challenge.
3. Immense Multiple Realization (IMR)
The multiple realization argument has posed one of the main challenges for
reductive views on mentality. Kim, however, says,
In my view, functional reductionism of the sort I have discussed, which, unlike
Block and Stalnaker’s type physicalism, is immune to the notorious multiple
realization argument, can also ground mental causation. [Kim 2005, page 148]
I am not convinced Kim’s position is immune to the multiple realization argument.
Or more precisely, I don’t think the view can be immune to what I call immense
multiple realization and answer the mental causation challenge at the same time. 7
This should become clear when we look at the scope and strength of the identity
claims Kim invokes to explain macro-causation in general, and to explain mental
causation in particular.
Kim’s response to Block’s causal drainage argument in [Kim 2005, chapter
2] gives us an inkling of the scope involved. In that chapter (also published as
“Blocking Causal Drainage and other Maintenance Chores with Mental Causation”
in Philosophy and Phenomenological Research, July 2003) Kim states the
in the same paragraph, “It seems to me clear that these are satisfying answers, and that to answer the
explanatory question it is not necessary for functional reductionism to yield general property
identities.”
7
To avoid a possible misunderstanding, I don’t think the species specific reductionism held by
Lewis and Armstrong faces the same problems as Kim’s position. The problems are specific for Kim
because of his reliance on the supervenience argument. Since that argument is a strong motivation
for his mind-body reductionism he cannot help himself to a reduction base of properties taken from,
say, modern neurobiology. On Kim’s view, the reduction base will have to consist of nothing short
of micro-based properties based at the fundamental physical level. If not, there is no way of stopping
a vicious generalization of the supervenience argument. This is the problem that drives him to claim
identities between a macro-property like being water and the total micro-based property of water
[Kim 2005, pages 67–69].
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following principle, which he takes to be “a plausible physicalist principle” [Kim
2005, page 59]:
Macro-micro Supervenience: All intrinsic properties of O, at any level
higher than L, supervene on the total micro-based property of O at level L.
The total micro-based property of an object at a level L is given by a complete
specification of all the objects parts at that level (for example the chemical level),
all the properties of these parts, and all the relations between those parts.8 If this
supervenience claim is correct, as seems plausible, then one can reiterate the
supervenience argument against any supervenient but irreducible intrinsic property
of O. Kim’s way to stop this problematic generalization of the supervenience
argument, which would render special science properties causally inert, is to
postulate identity between ordinary macro-properties of objects and micro-based
properties of those objects.
Kim gives an example of the kind of identities he has in mind in his reply to
Block [Kim 2005, pages 68–69]. I find it illuminating to run through this example
in detail, as it gives us a clear image of the strength and scope of the identities that
are supposed to solve the causal exclusion problem for supervenient macroproperties. Imagine a reduction of the property of being water to the property of
having the total microstructure of water. The first step would plausibly be
something like the following identity claim:
Being water = being composed of water molecules
Water, as picked out by our common sense concept, contains other substances too,
so the macro-property of being water must be understood in a somewhat idealized
sense. I do not think this presents a problem. However, to be a water molecule is a
supervenient macro-property, so in order to be causally efficacious on the reductive
8
Kim explains: “(…) if L is the level of the Standard Model, a total micro-based property of O at
this level would give a complete description of O’s microstructure in terms of the particles and
forces posited in the Standard Model” [Kim 2005, page 59].
Immense Multiple Realization
57
account in question, this property must be identified with a micro-based macroproperty. The obvious candidate is:
Being a water molecule = being composed of two hydrogen atoms and one
oxygen atom in a specified constellation.
But the atoms of contemporary physics are not Democritian; they have parts. The
property of being a hydrogen atom is a supervenient macro-property that must be
identified with a micro-based macro-property in order to be causally efficacious on
the reductive account in question. 9 The obvious candidate now is:
Being a hydrogen atom = being composed of one proton and one electron in
a specified constellation.
Deuterium and tritium are isotopes of hydrogen with different microphysical
constellations of the nucleus; they have respectively one and two additional
neutrons. This fact forces the reductionist to choose between identifying the
property of being hydrogen with a disjunction of micro-based properties or to
disregard other isotopes than protium, which is the most common isotope. 10
Remember that Kim, in order to avoid problematic generalizations of the
supervenience argument, is committed to identities between ordinary macroproperties and micro-based macro-properties based at any level.
9
At this point one might be tempted to object by saying that hydrogen is a natural kind as good as
they come; if things don’t have causal powers by virtue of being hydrogen atoms then we don’t
know what to think anymore. But this intuition just reveals the gist of the generalization argument.
Kim’s response to that argument implies that the property of being hydrogen is causally efficacious
in virtue of being identical to a micro-based property based at a lower level, namely the level of subatomic physics. This consequence follows from (CSA) and the fact that the property of being a
hydrogen atom supervenes on the different more determinate properties of being protium, being
deuterium and being tritium (protium, deuterium and tritium are different isotopes of hydrogen).
10
I.e. you could deny that heavy water is water. Heavy water has the same chemical structure but a
different micro-physical composition. It also has slightly different boiling and freezing points. Heavy
water and semi heavy water (consisting of one regular hydrogen atom (protium), one deuterium atom
and one oxygen atom) occur naturally in regular water. The question seems analogous to the one
about jadeite and nephrite that Kim himself discusses [Kim 2005, pages 57–58]. However, there is a
much stronger similarity relation between the different isotopes of hydrogen; they are all atoms with
one proton in the nucleus.
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Unfortunately, the problem for local reduction is even worse. Imagine the
classical model of the atom. The spatial configurations of the composites of atoms
differ over time, and they differ between different atoms, although these atoms
evidently exhibit the same (or at least similar) chemical properties. Supposing
quantum mechanics, this becomes even more radical. Water molecules can occupy
infinitely many quantum states. 11
The crucial point is that the property of being a hydrogen atom supervenes
on the total micro-based property of the atom, even when that total micro-based
property is specified in terms of the exact quantum state of the atom. Any hydrogen
atom is in one specific quantum state or other, and for each such specific quantum
state, if an object is in it, it is a hydrogen atom. This conforms to the standard
understanding of supervenience that Kim uses. 12 Whether this is reasonably
described as an instance of a realization relation might be up for discussion, but all
we need in order to run the supervenience argument against the macro-property is
that this is an instance of the supervenience relation, and that a causal closure
principle holds for the quantum level. 13 Since Kim accepts both macro-micro
supervenience and the causal closure of microphysics, he is committed to identities
between causally efficacious macro-properties and the kind of extremely specific
micro-based properties just discussed.
11
Barry Loewer makes this point in [Loewer 2001].
The definition of supervenience Kim gives in the same chapter of [Kim 2005, page 33] is
“Supervenience. Mental properties strongly supervene on physical/ biological properties. That is, if
any system s instantiates a mental property M at t, there necessarily exists a physical property P such
that s instantiates P at t, and necessarily anything instantiating P at any time instantiates M at that
time.”
13
Kim seems to accept such a closure principle. He writes, “It is only when we reach the
fundamental level of microphysics that we are likely to get a causally closed domain” [Kim 2005,
page 65].
12
Immense Multiple Realization
59
4. Can Micro-based Properties figure in Macro–Causal
Relations?
Let us examine Kim’s account of macro-causation in light of immense multiple
realization. Granting immense multiple realization, the locality of the property
identities must be pushed to the extreme. This view has two striking consequences.
(1) Irrealism for mental properties. There is nothing that uniquely corresponds to
ordinary mental and other macro-level predicates. Statements about mental
properties have not only physical truth conditions, but truth-conditions that involve
micro-based physical properties stated in micro-physical terms. (2) Macro-events,
granting Kim’s view that events have properties as constitutive parts, 14 turn out to
be extremely fragile. Micro-based properties are extremely specific and any microchange yields a different property. This results in macro-events being extremely
fragile, because these extremely specific micro-based properties are constitutive
parts of the events. As I will argue, it makes the counterfactual dependencies
between macro-causal relata come out wrong. Or maybe a slightly more modest
claim is more reasonable: it makes the counterfactual dependencies between macrocausal relata deviate strongly from the standard understanding in most special
sciences – and indeed from our own common-sense understanding – of the world.
Here are some examples that illustrate the problem. 15
There are properties at the subatomic level that are irrelevant for the
chemical (higher-level) causal activity of molecules. Water dissolves sodium
because the bipolarity of water molecules facilitates their attachment to the Na+ and
CL- ions. If one identifies the property of being bipolar with a total micro-based
property in the way described in section 3, one will lose generality and the
counterfactual dependencies will deviate from the standard conception.
14
See [Kim 1973] and [Kim 1993].
The kind of phenomenon I have in mind is discussed by, among others, Stephen Yablo [Yablo
1992, 1997], Sydney Shoemaker [Shoemaker 2003], and Eric Marcus [Marcus 2005], so the idea is
not novel. However, I don’t think it has been appropriately acknowledged by reductionists motivated
by the causal exclusion problem.
15
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Let me elaborate a little in order to back up these claims. A certain liquid
has the property of being water, and some sodium gets dissolved in that liquid. The
liquid also has a series of different total micro-based properties in the time-interval
through which the dissolving takes place. At a certain time t, right before the
dissolving, two different events take place which, according to the reasoning behind
the causal exclusion argument, compete for causal efficacy. These two events
involve different properties, but the same object and the same time. 16 So we have
the object L, the time t, and the property of being water and the total micro-based
property (TMP).
Macro Cause Candidate: [Water, L, t]
Micro-based Cause Candidate: [TMP, L, t]
It is reasonable that the macro-property of being water supervenes on the totality of
specific total micro-based properties that instances of water might have. This is also
in accordance with the macro-micro supervenience principle Kim accepts [Kim
2005, page 59] that I quoted in section 3 of this paper.
The relations of counterfactual dependence between these two cause
candidates and the effect are arguably as follows. Let’s call the effect E, which is
the dissolving of the sodium in the liquid.
CD1: E depends counterfactually on [Water, L, t]
CD2: E does not depend counterfactually on [TMP, L, t]
CD1 says that if the liquid had not been water at time t, then the effect would not
have followed. CD2 says that it is not the case that if the liquid had not had the total
micro-based property that the liquid actually had at t, then the effect would not have
followed. On the reasonable assumption that counterfactual dependence is
16
Some philosophers might argue that it is not the same object involved in these two events. Such a
position might very well have some plausibility, but I shall ignore it for the nonce.
Immense Multiple Realization
61
indicative of causal relations, this provides reasons to think that it is [Water, L, t]
rather than [TMP, L, t] that is the cause of E.
In general, the truth values of counterfactuals are neither preserved by the
strengthening nor the weakening of the antecedent. The example just discussed
serves as a counterexample to the idea that weakening the antecedent preserves
truth value for counterfactuals. By assumption, being in (TMP) necessitates being
water, but not vice versa. Consequently, not being water necessitates not being in
(TMP), so not being water is a stronger claim than not being in (TMP). This means
that we cannot conclude, without further argument, any counterfactual dependence
between E and [TMP, L, t] from the counterfactual dependence between E and
[Water, L, t].
Neither could one conclude without further argument that E would depend
counterfactually on [Water, L, t] if E depended counterfactually on [TMP, L, t].
Doing so would amount to the so-called fallacy of strengthening the antecedent. 17
The following intuitive example illustrates the fallacy. Suppose that CC1 is true,
CC1: If I had gone to the beach I would have bathed.
Still, CC2, which we get from strengthening the antecedent of CC1, can very well
be false,
CC2: If I had gone to the beach and there were lots of stinging jellyfish
there, I would have bathed.
Consequently, preservation of counterfactual dependence is not guaranteed under
such operations. These observations rule out unsupported inferences from
17
See for example [Lewis 1973, pages 31–32] for a brief discussion of the fallacy. According to
Lewis the general form of the fallacy is given by the following invalid inference pattern [Lewis
1973, page 32]:
(χ → ϕ)
ϕ →Ψ
∴χ → Ψ
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counterfactual claims with general antecedents to claims with strengthened
antecedents, and vice versa. Consequently, one needs additional support for
claiming counterfactual dependencies between effects and the specific realizers of
the cause. In cases like the above example of being water and (TMP), the additional
support seems to go in the opposite direction: the effect does not depend
counterfactually upon the instantiation of the micro-based property (TMP).
One might reply that it is question begging to assume that there are such
coarse-grained effects. The reply would then be that in order to get the
counterfactual dependencies right, both cause and effect must be fine-grained to
similar extents. Returning to our example, the following relation of counterfactual
dependence might be suggested,
CD3: The specific way in which the dissolving of the sodium happened
depends counterfactually on [TMP, L, t].
The prospects for dependencies like CD3 to hold seem better, but there are at least
two problems with this move.
The first is that this move, if it is to save Kim’s account, must work totally
across the board. There are reasons to think this will not be the case. Some effects,
no matter how fine-grained, do not depend counterfactually on all intrinsic aspects
of the cause. It would seem, for example, that effects caused by gravitational forces
do not depend on the specific distribution of other properties among the parts of the
object. Suppose the sun exerts a gravitational force on Earth. This effect depends on
the distance between the mass-centers of the two objects and their respective
masses. But these factors, the masses and distances, can be realized in many
different ways. The objects could for example be made of different materials than
they actually are. If we think of the intrinsic properties of this earth–sun system as
supervenient on the total micro-based property of that system, it is unreasonable to
claim that the macro-properties of mass and distance between the parts this system
instantiates are causally excluded by the subvenient total micro-based property of
the system.
Immense Multiple Realization
63
The second problem is that by fine-graining effects in the extreme way
demanded by such a proportionality principle, one gets into other conflicts with
macro-causation as standardly understood. Such an extreme fine-grainedness of
causal effects conflicts with the common understanding of macro-causation because
it introduces counterintuitive and spurious causal relations. David Lewis has given
an example of such spurious causal relations in [Lewis 1986, page 198]. The
example involves a firing squad of nine soldiers firing at a convict. Lewis discusses
the reasonable claim that each single shot is to be reckoned as a cause of the
convict’s death. To make his counterfactual analysis of causation accommodate this
intuition he considers the idea that the convict’s death is so finely individuated that
each and every shot makes a genuine difference to the effect. This, however, gives
counterintuitive results.
(…) suppose there was a gentle soldier on the firing squad, and he did not
shoot. If the minute difference made by eight bullets instead of seven is enough
to make a different event, then so is the minute difference made by eight
instead of nine. So if the victim’s death is so very fragile that it would not have
occurred without your act, equally it is so fragile that it would not have
occurred without the gentle soldier’s omission. If by reason of fragility the
death depends causally on your act, then equally it depends causally on the
omission. So the gentle soldier caused the death by not shooting, quite as much
as you caused it by shooting! This is a reductio. [Lewis 1986, page 198]
The important point is that extremely fragile causal effects give counterintuitive
results in cases like the one above. In general, as Collins, Hall and Paul write in the
introduction to Causation and Counterfactuals
(…) tightening the individuation conditions for events in this way results in a
landslide of causal connections, too many of them unwanted. [Collins, Hall and
Paul 2004, page 46]
On this background I conclude that the extreme fragility of causal relata implied by
Kim’s property identities rules out a conservative account of macro-causation in
general, and of mental causation in particular.
Summing up this section, the lesson is that the local identities between
ordinary macro-properties and micro-based macro-properties do not do the job they
Paper I
64
are put to within Kim’s framework. The ordinary macro-properties play a causal
role for which highly specific micro-based macro-properties are unsuited. The
(IMR) observation showed that there really is such a radical, and actual, difference
between ordinary macro-properties and the micro-based properties in Kim’s
proposed reduction base.
Taking these problems seriously, can Kim retreat to psycho-physical
property identities between mental properties and more coarse-grained physical
properties? Two different moves are brought up in Kim’s latest book, and he seems
to think of these as possible moves within the framework of his functional
reductionism. In the next two sections I consider and reject these moves by
reiterating the supervenience argument. In closing, at the end of section 6, I
consider an essence-based move that I have not seen in Kim’s own writings.
5. Token Identity between Instances of Functional Properties
and their Realizers
Is it a viable option to identify mental properties with functional properties, while
identifying the instances of these functional properties with instances of their
physical realizers? In chapter two of his latest book Kim suggests something along
these lines:
All we need is identity at the level of instances, not necessarily at the level of
kinds and properties; causation after all is a relation between property or kindinstances, not between properties or kinds as such. [Kim 2005, page 58]
While this bears some resemblance to a Davidsonian token identity theory, within
Kim’s framework it is quite puzzling. As far as I know, Kim holds that events are
property instances, i.e. that they are triples of objects, times and properties [Kim
Immense Multiple Realization
65
1973, Kim 1993], although he at times has expressed doubts about that thesis. 18 It
means that two events, or property-exemplifications, are identical if and only if they
are instances of the same property by the same object at the same time. So identities
at the level of instances can only occur if there are identities at the level of
properties. But Kim seems to be denying this in the above quote. Let’s see how we
can make sense of this apparent inconsistency.
Let me first restate the view in more detail. Suppose that PR is a realizable
second-order property, 19 and that R1 is PR’s realizer at a specific occasion. S is the
structure or object that instantiates the properties, and t is the time of the
instantiations. If we accept that the instantiation relation is a three-place relation we
get the following, where IPR is the instantiation of PR by S at t, and IR1 is the
instantiation of R1 by S at t.
IPR = [S, t, PR]
and
IR1 = [S, t, R1]
In order to get identity between IPR and IR1 there must be identity between PR and
R1, at the level of kinds or properties, which we by assumption do not have. So how
can Kim claim that this is all we need?
Harmony could be achieved by defining the instantiation relation for second
order properties in the following way. The possible realizers for PR are R1, …, Rn,
and the instantiation relation for PR is not IPR = (S, t, PR) as above, but rather
18
He says in the preface to Supervenience and Mind [Kim 1993, page IX]: “In essays 1 and 3, I
formulated and argued for what is now standardly called the ‘property exemplification’ account of
events, and I still think it is a viable approach. However, I am now inclined to think that ontological
schemes are by and large optional, and that the main considerations that should govern the choice of
an ontology are those of utility, simplicity, elegance, and the like.” Kim, on this background, might
want to reconsider his theory of events in light of problems that emerge concerning mental and
special science causation. That would be one way of responding to the argument in this section of
this paper.
19
My use of the terminology of second order properties is consistent with Kim’s here [Kim 1998,
page 20]. In this sense, a second-order property is the property (had by an individual) of having a
first-order property of some kind (e.g. that plays a certain functional role). This conforms to the
standard ramified type-theoretic usage where there is a hierarchy of levels with individuals at the
bottom, then properties, properties of properties and so forth. In addition there is an order hierarchy
at each type level.
Paper I
66
IPR* = [S, t, Ri]
where Ri is one of R1,…, Rn
which gives us the identities at the level of instances that Kim seems to have in
mind
It is important to be a careful here. If we rephrase Kim’s proposal in terms
of property-instances, it runs like this (where R1 is the realizer, the instantiations are
defined as above, and the arrow indicates a causal relation),
(IPR* = IR1)
E
IPR* and IR1 are identical by
assumption
The problem with this idea is that the instance (IPR = IR1) is causally efficacious in
virtue of being an instance of R1, and not in virtue of being an instance of PR. 20
This point has been made earlier by Sydney Shoemaker [Shoemaker 2003,
page 434]. He says that if one claims identity between instances then the standard
causal relevance argument used against Davidson’s token identity view applies.
What we want from an account of mental causation is an understanding of how
mental events are causes in virtue of their mental properties. This is not saved by
claiming that mental events are causes in virtue of being identical to instances of
physical properties. Essentially the same reply has also been made by Horgan in
[Horgan 1997, pages 172–174].
6. Mental Properties as Coarse-grained Physical Properties
A second line of defense Kim seems to find promising consists in identifying
second-order functional properties with disjunctions of their first-order realizers. At
least he hints at this in [Kim 2005], though it has to be said he is highly skeptical in
20
The expression “in virtue of” is a possible source of confusion. What I have in mind is that, in the
circumstances, the fact or event that R1 is instantiated will be causally sufficient for E independently
of the facts that PR is instantiated and that IPR is identical to IR1. Moreover, note that R1 is a
constitutive part of the instantiation, while PR is not.
Immense Multiple Realization
67
[Kim 1998, pages 107–108]. After introducing the suggestion about identity at the
level of instances, which we discussed in the previous section, Kim briefly
discusses the disjunctive approach:
The second option which allows disjunctive kinds is a more conservative
approach and may be more viable as a general solution. On the disjunctive
approach, being jade turns out to be a causally heterogeneous property, not a
causally inert one, and jade turns out to be a causally heterogeneous kind, not a
causally irrelevant one. To disarm Block’s multiple composition argument,
adopting either disjunctive property/kind identities or instance (or token) identities
seems sufficient. [Kim 2005, page 58–59]
There are well-known arguments against disjunctive properties. I will not examine
them here; various versions can be found in [Armstrong 1978 chapter 14, Kim 1998
page 107–109]. But let me note that the standard arguments against disjunctive
properties can be answered by showing that some disjunctive properties have
disjuncts that all stand in similarity relations to each other. Two examples of such
relations are (a), the disjuncts are all realizers of the same functional role; and (b),
the disjuncts are all determinates under the same determinable property. This would
enable one to distinguish between mere disjunctive properties, which lack such a
relation between the disjuncts and therefore are objectionable, and disjunctive
properties that can figure in explanatory generalizations. Nonetheless, there is a
strong causal argument, which can be formulated within Kim’s own framework,
against all disjunctive properties. This argument blocks the appeal to disjunctive
properties as an answer to the (IMR) problem for Kim.
The causal argument against disjunctive properties is analogous to the
original supervenience argument, and it goes like this. The instantiation of a
disjunctive property by an object supervenes on the instantiation of one or more of
its disjuncts by the same object. 21 One can therefore run a supervenience argument
against the causal efficacy of disjunctive properties. Suppose D is a disjunctive
property having D1,…,Dn as disjuncts. Di is the disjunct in virtue of which D is
21
Actually, a disjunctive property could well supervene on the instantiation of exactly one disjunct,
i.e. that the instantiation of two or more disjuncts might preempt the supervenient property from
being instantiated. I will not consider this possibility and its relevance for the causal argument here.
Paper I
68
instantiated at this specific occasion, and E is an alleged effect of the instantiation
of D.
D
Di
E
The instantiation of D is nothing over and above the instantiation of Di, so the fact
that D is instantiated cannot play a causal role over and above the fact that Di is
instantiated. By reasoning along the lines of Kim’s original causal exclusion
argument, the disjunctive property is causally excluded by its disjunct. Kim regards
causal closure of the subvenient domain as an essential premise in the original
causal exclusion argument [Kim 2005, page 65], but the present argument still
applies. The domain of the disjuncts is causally closed relative to the disjunctive
property because whenever there is an effect for which the disjunctive property is
(thought to be) sufficient, there is a causally sufficient disjunct in place. By analogy
to the original causal exclusion argument, disjunctive properties have no causal role
to play and should be excluded from our ontology. 22 The viability of the disjunctive
move would therefore require a working response to the causal exclusion argument
in the first place.
Let us finally consider one last, but perhaps the most promising, attempt to
find a more coarse-grained and thereby better suited physical reduction base. Kim’s
original idea was to identify macro-properties with micro-based macro-properties,
which are defined as follows,
P is a micro-based property just in case P is the property of being completely
decomposable into nonoverlapping proper parts, a1, a2,…, an, such that P1(a1),
P2(a2),…, Pn(an), and R(a1,…, an). [Kim 1998, page 84]
22
Kim accepts the causal criterion of existence, which says that anything that exists has causal
powers, see [Kim 1998, page 119], confer also [Armstrong 1978, Alexander 1920].
Immense Multiple Realization
69
We have seen the problems facing Kim’s proposal in light of immense multiple
realization. What the functional reductionist needs, it seems, is a conception of
micro-based properties that does not include causally irrelevant details. At the same
time, the micro-based property should be of first order, because it will not help, as
we have seen, to make it into a realizable higher-order property. As far as I can see,
the only option left is to relax the requirement of complete decomposition in the
definition of a micro-based property.
Consider our earlier example of the hydrogen atom in section 3. Having
exactly one proton in the nucleus seems to be an essential first-order categorical
property of any hydrogen atom. It is not, however, a micro-based property
according to the definition above. Protium, deuterium and tritium are hydrogen
atoms, but they have different complete decompositions. They even have different
numbers of constitutive parts, and are therefore instantiations of different microbased properties. The present suggestion is to identify the property of being
hydrogen with the property of having exactly one proton in the nucleus.
If one adopts this view one ends up in a situation in which a first-order
determinable property supervenes on a set of determinate first-order properties. The
property of being a hydrogen atom supervenes on the properties of being protium,
of being deuterium and of being tritium. 23 One might therefore worry whether a
new version of the supervenience argument could be targeted against the causal
efficacy of the property of being a hydrogen atom thus understood. However, it is
not reasonable to say that the subvenient domain is causally closed in this case. The
subvenient domain actually includes the supervenient properties themselves since
being protium can be thought of as a conjunctive property having the property of
being hydrogen as a conjunct. We can therefore straightforwardly claim that causal
23
This does not have to be the case though. It will depend on the modal strength of the
supervenience claim and on whether we accept un-instantiated properties. Let’s assume the relevant
supervenience claim holds with nomological necessity. Then the property of having one proton in
the nucleus supervenes on the set of properties: {being protium, being deuterium, being tritium}. If
more isotopes are nomologically possible they would have to be included in the supervenience base,
even though they might not be instantiated in the actual world. Actually, it is possible to synthesize
other – highly unstable – isotopes, for example Hydrogen-4. For such reasons, nomological
supervenience might fail if we reject properties that are not instantiated in the actual world. What uninstantiated properties one would have to include in the supervenience base depends on the modal
strength of the supervenience claim. If supervenience fails, the antecedent of (CSA) will not hold.
Paper I
70
closure does not hold in this case. It is not the case that a domain D of properties is
causally closed relative to a sub-domain of itself. The supervenience argument will
therefore not target this suggestion.
There are, however, other objections. They depend on the strong claim
which says every realizer of a causally efficacious macro-property has a
microphysical essence in common with all the other (possible) realizers. 24 This is
the essentialist aspect of the suggestion. Whether that strong claim holds is up for
further discussion, but it is at least not prima facie obvious that it would. The
received view on biological species for example, is no longer essentialist in this
sense 25 [Ereshefsky, 2006]. There is also a question whether one could accept
relational properties in the reduction base. It might be that relational properties are
best construed as second order properties, namely as the property of standing in
some relation of a certain type, which involves quantification over first-order
relations. If so, one would face the argument from section 5 again. On the other
hand, some reformism might be unavoidable, so one might claim that only mental
properties where the realizers have such a microphysical basis in common are
causally efficacious properties.
7. Conclusion
Functional reductionism conflicts with a conservative understanding of mental
causation. I have argued that the position as stated by Kim fails in its endeavor to
preserve mental causation as it is commonly understood. On the other hand, I have
not claimed that any reformation of our conception of mental causation is out of
question, I have only pointed out that a conservative account is unavailable within
Kim’s framework. It might turn out that the eliminative aspect of functional
reductionism is unavoidable, and that substantial revisions of our understanding of
24
Actually, any higher higher-level causally efficacious and supervenient property must have a
microphysical essence.
25
Michael Devitt has recently questioned this consensus, and argued that essentialism is right, even
for biological species (Devitt, lecture at CUNY, New York 23.02.06).
Immense Multiple Realization
71
macro-causation therefore have to be made. At the same time, these consequences
provide additional reasons to question the supervenience argument, and to critically
examine the status of the four claims that give rise to the problem. There is as yet no
clear route from the supervenience argument to an acceptance of Kim’s functional
reductionism.
REFERENCES
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St. Martins Street, London.
Armstrong, D.M. [1978] A Theory of Universals. Universals and Scientific Realism
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Collins, John, Ned Hall and L.A. Paul (2004) Causation and Counterfactuals, MIT
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Block, Ned [2003] “Do Causal Powers Drain Away?” Philosophy and Phenomenological
Research Vol. LXVII, No. 1.
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Mele, 1993].
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2006 Edition), Edward N. Zalta (ed.), URL =
<http://plato.stanford.edu/archives/spr2006/entries/species/>.
Gillett, Carl and Barry Loewer [2001] (eds.) Physicalism and Its Discontents,
Cambridge University Press.
Heil, John and Alfred Mele [1993] (eds) Mental Causation, Clarendon Press, Oxford.
Horgan, Terence [1997] “Kim on Mental Causation and Causal Exclusion” NOÛS,
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Horgan, Terence & John Tienson [2001[ “Deconstructing New Wave Materialism” in
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___
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[2001] “Lonely Souls: Causality and Substance Dualism”, in Soul, Body, and
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[2003] “Blocking Causal Drainage and Other Maintenance Chores with Mental
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[2005] Physicalism, or Something near Enough, Princeton University
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Lewis, David [1973] Counterfactuals, Basil Blackwell.
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[1986] “Causation” including “Postscripts” in Philosophical Papers vol.2, Oxford
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[1997] “Wide Causation” in NOÛS, Vol. 31, Supplement:
Philosophical Perspectives, 11, Mind, Causation, and World.
PAPER II
Causal Exclusion and the Preservation
of Causal Sufficiency℘
Anders Strand
ABSTRACT
Causal overdetermination, the existence of more than one sufficient cause for an effect, is
standardly regarded as unacceptable among philosophers of mental causation. Philosophers
of mind, both proponents of causal exclusion arguments and defenders of non-reductive
physicalism, seem generally displeased with the idea of mental causes merely
overdetermining their already physically determined effects. However, as I point out below,
overdetermination is widespread in the broadly physical domain. Many of these cases are
due to what I call the preservation of causal sufficiency. We need therefore to be precise
about what unacceptable overdetermination amounts to in order to evaluate the prospects
for a non-reductive account of mental causation. I argue that in order to have a good
understanding of unacceptable overdetermination we should appeal to the notion of a
minimal sufficient cause. In brief, a sufficient cause is minimal if it is sufficient to bring
about the effect, but not more than sufficient. One way a cause could be more than
sufficient for an effect is if its existence necessitates the existence of another (simultaneous)
cause that is also sufficient for the same effect. In the second half of the paper I use this
revised understanding of unacceptable causal overdetermination to show that the validity of
the causal exclusion argument depends on strong readings of the principle of the causal
self-sufficiency of physics. These strong readings can reasonably be questioned by a
believer in non-reductive accounts of mental causation. This puts the burden of argument
back on the causal exclusionist.
1
2
3
4
5
6
℘
Introduction
What’s wrong with the Causal Exclusion Principle?
Minimal Sufficient Causes and the Causal Exclusion Principle
Causal Self-Sufficiency of Physics
Causal Self-sufficiency for Believers in Non-reductive Accounts
of Mental Causation
Conclusion
Thanks to Carsten Hansen, John Hawthorne and Iris Oved.
Paper II
76
1. Introduction
Suppose you’re a non-reductive physicalist about mental states and events. You
think that mental phenomena somehow depend on underlying physical phenomena,
but you don’t believe that mental phenomena are identical to physical phenomena.
Then someone comes along with a version of the highly influential causal exclusion
argument. She notes your commitment to non-identity, and puts the following two
principles on the table:
Causal Exclusion Principle: An effect cannot have more than one sufficient
cause at a time.
Causal Closure of Physics: If a physical effect has a sufficient cause at a
time, then it has a sufficient physical cause at that time.
From this she concludes that you’re committed to epiphenomenalism for mental
states and events. You, as most of us, reasonably think that mental states and events
sometimes have physical effects, so you start to wonder how the tension between
these claims can be resolved. How can physical effects have non-reducible mental
causes in addition to their sufficient physical causes?
In this paper I focus on the interplay between the causal exclusion principle
and the causal closure of physics in the causal exclusion argument. I start by
showing why the causal exclusion principle has to be carefully reformulated. The
label ‘causal exclusion principle’ is due to Jaegwon Kim 1 , whose latest formulation
of the principle I take as the point of departure for my discussion. The plausibility
of the causal exclusion principle depends on certain features of minimal sufficient
causes, especially on the uniqueness of minimal sufficient causes. The discussion
1
See [Kim 1998], and especially chapter 2 of [Kim 2005].
Causal Exclusion and the Preservation of Causal Sufficiency
77
leads to a clarification of the argumentative burden resting on the principle of the
causal closure of physics.
In the second half of the paper I identify several versions of the causal
closure (or self-sufficiency) of physics, and show exactly which of them can
combine with the revised causal exclusion principle in a valid causal exclusion
argument. As it turns out, the non-reductionist 2 can choose between several weaker
versions of the causal closure principle and thereby disarm the causal exclusion
worry. I also provide some grounds for skepticism about the stronger versions of the
causal closure principle.
2. What’s wrong with the Causal Exclusion Principle?
Skepticism about causal overdetermination is expressed with some frequency by
participants in the mental causation debate. But it appears also in other contexts.
Frank Jackson, for example, speaking of the causal efficacy of a disposition
compared to the causal efficacy of its realizer (bonding B) says,
All the causal work is done by bonding B in concert with the dropping. To
admit the fragility also as a cause of the breaking would be to admit a curious,
ontologically extravagant kind of overdetermination. [Jackson 1998, page 92]
Scott Sturgeon reveals a similar intuition when he describes his version of the
overdetermination argument against mental causation, which he himself criticizes
on other grounds [Sturgeon 2000]:
The odd case of such overdetermination is fine. But it must be odd. Thus we
have
No Overdetermination: The physical effects of mental events are not
generally overdetermined.
2
Again, a non-reductionist is here understood as someone who denies the identity between mental
and physical phenomena.
Paper II
78
Jaegwon Kim has turned this skepticism into a general principle reminiscent of
Sturgeon’s No Overdetermination principle just stated. In his latest book Kim
writes:
Exclusion. No single event can have more than one sufficient cause occurring
at any given time – unless it is a genuine case of causal overdetermination.
[Kim 2005, page 41]
This formulation of the principle, given by Kim as part of his latest explication of
the causal exclusion argument,
plays a crucial role in that argument, and is
therefore worthy of critical scrutiny [Kim 2005, chapter 2]. As far as I understand
Kim, the genuine cases of causal overdetermination are analogous to firing squad
cases. These are cases where the overdetermining causes are thought to be
independent and individually sufficient for the effect. I will not quarrel with that
proviso here.
My main concern is to investigate whether the kind of exclusion principle
alluded to in the above quotes can be spelled out in a precise way. The main reason
for taking a closer look at the principle is that the version quoted from Kim above is
subject to certain kinds of counterexamples. I shall grant myself latitude to talk
about an idealized causal exclusionist in this paper. This person would be a
proponent of the causal exclusion principle, and an advocate of the causal exclusion
argument. At points I will make references to Kim and his position, as the main
representative of this line of thought.
Several kinds of counterexamples to the causal exclusion principle were
given by Ted Sider in a brief paper written in response to Trenton Merricks’s
Objects and Persons [Sider 2003, Merricks 2003]. Sider points out that an effect
being causally overdetermined both by a collection of micro-events and by the
macro-event composed by those micro-events is completely acceptable. He gives a
whole range of such examples, all having in common that the competing causes
perfectly coincide. Further examples are effects caused by an object and by an event
involving that object, or an effect caused by a fact and a corresponding event.
Causal Exclusion and the Preservation of Causal Sufficiency
79
In this paper I present another range of counterexamples to the causal
exclusion principle. These are what I call preservation cases. They differ from
Sider’s in that the different cause candidates in preservation cases are both concrete
and do not coincide perfectly 3 .
Imagine a ball hitting a window and causing the window to break. Barring
worries about additional causal conditions, let us suppose that the ball hitting the
window was causally sufficient for the window to break. Now, imagine the object
that consists of all the parts that constitute the ball except for one molecule. The
hitting of the window by this other object seems as likely a candidate for being a
sufficient cause of the breaking as the hitting of the ball itself 4 . This is a case where
an effect has more than one sufficient cause. However, in cases like this it is quite
reasonable to think that the causal sufficiencies of the ball and of its slightly smaller
brother are tightly related 5 . It makes good sense to say that the ball is causally
sufficient for the effect in virtue of having a proper part that is causally sufficient
for that effect. Put slightly differently; the causal sufficiency is preserved through
the (imagined) adding or removal of the molecule.
Here is another example 6 . What causes a uniform tabletop to remain 92 cm
above the floor? The answer is, of course, the legs. Suppose the table has four legs,
and that the four legs are sufficient for keeping the tabletop 92 cm above the floor.
But any combination of three legs would be sufficient for that effect too. In this
example one could remove one arbitrary leg, and get four different but still
sufficient causes for the very same effect. In this case there seem to be four different
minimal sufficient causes for the very same effect. Again we see how the causal
sufficiency is preserved through certain changes of the cause, and through switching
between different cause candidates.
Cases like these are easy to find – actually, they are hard to avoid – and they
show that causes one intuitively regards as sufficient for a certain effect often have
3
If one thinks of facts as abstract objects and events as concrete objects, the relata in the third kind
of example given by Sider will not be coincident in any straightforward sense.
4
Thanks to John Hawthorne for pressing such cases in informal discussion.
5
I allow myself to talk loosely about both objects and events as causes here. The example relies on
the ball itself not being a minimal sufficient cause of the breaking.
6
Thanks to Iris Oved for mentioning this example.
Paper II
80
proper parts that are sufficient for the very same effect 7 . Since neither events nor
objects are identical to any of their proper parts, we have a recipe for generating
innumerable counterexamples to Kim’s causal exclusion principle.
This observation shows that the exclusionist needs some kind of restriction
in the formulation of the principle. He should be able draw a distinction between
this kind of acceptable causal overdetermination and the kind that he thinks should
be disallowed. Kim gives a different formulation of the exclusion principle in the
first chapter of his latest book. Maybe it will be helpful to reflect on that version
here.
Principle of Causal Exclusion: If an event e has a sufficient cause c at t, no
event at t distinct from c can be a cause of e (unless this is a genuine case of
causal overdetermination). [Kim 2005, page 17]
It is hard to tell exactly what Kim has in mind by “distinct from”. But as it is
important to be clear on this, let us consider likely understandings of that
expression.
One reading is spatially distinct from, i.e., that there is no overlap between
the regions at which the events occur. This, however, cannot be what Kim has in
mind. Events are property instances for Kim, so they are located where the
instantiating objects are located. Spatial distinctness is therefore ruled out by the
supervenience thesis Kim attributes to non-reductive physicalists. According to
strong supervenience both the mental supervenient property and the physical base
property are instantiated by the same structure at the same time 8 . They are therefore
instantiated at the same spatial region.
A second option is that “distinct from” just means not identical to. That,
however, makes this second formulation just as vulnerable to our counterexamples
as the earlier formulation. This is clear because no object, nor event, is identical to
any of its proper parts.
7
This will depend on how finely the effect is individuated. I return to that complication later.
Here’s Kim’s definition of mental-physical supervenience: “Supervenience. Mental properties
strongly supervene on physical/ biological properties. That is, if any system s instantiates a mental
property M at t, there necessarily exists a physical property P such that s instantiates P at t, and
necessarily anything instantiating P at any time instantiates M at that time.” [Kim 2005, page 33]
8
Causal Exclusion and the Preservation of Causal Sufficiency
81
A third option is that “distinct from” means mereologically disjoint from. In
other words, two events are distinct if and only if they don’t have any parts in
common. This suggestion blocks most of the counterexamples. Given Kim’s
understanding of events (as property exemplifications), it allows for an effect to be
overdetermined by an event and an object constitutive of that event. It also allows
for the examples I’ve spelled out, where one sufficient cause has another sufficient
cause as a proper part 9 . This interpretation, however, brings the causal exclusionist
into trouble in the following ways.
(1) It allows for a certain range of non-reductive positions, namely positions
on which mental events and their physical realizers are mereologically related 10 . If
such views are tenable they will not be vulnerable to the exclusion argument.
Consequently, the exclusion argument will have a weaker conclusion than the stark
choice between reductive physicalism and epiphenomenalism that Kim concludes
with [Kim 1998, page 46].
(2) If, like Kim, one holds the property exemplification view of events, then
events are analyzed as triples of objects, properties, and times. Taken literally, the
objects, properties, and times can be understood as parts of the events they
constitute. If so, then supervenient events and their bases will be mereologically
related whenever they both have the same object as a constitutive part. On Kim’s
account of mind-body supervenience, supervenient mental property instances and
their physical bases are instantiated by the same object/structure. Mind-body
supervenience would thereby ensure that supervenient events are mereologically
related to their subvenient events and thus can’t be causally excluded by them.
Moreover, this combination of views seems to render the causal exclusion
principle totally uninformative. If we take the analysis of causal relata into property
9
This interpretation also allows for the kind of case that troubles Trenton Merricks in his book
Objects and Persons [Merricks 2003]. Merricks argues against the existence of ordinary macroobjects such as tables and chairs on the ground that they are causally excluded by microphysical
particles arranged tablewise and chairwise. On the mereological disjointness reading of distinct, this
kind of overdetermination would be acceptable because the collection of particles arranged tablewise
and the table would have parts in common. At least, each and every particle itself would have a part
in common with the table, namely the particle itself.
10
I tend to favor such a view myself. I discuss one version in the fourth paper of this thesis. The core
idea relies on a mereology for properties that naturally transfers to a mereology for causal relata
when these are analyzed as triples of objects/structures, properties and times.
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82
exemplifications literally, then all simultaneously occurring causal relata will have a
part in common, namely the time at which they occur. So no simultaneously
occurring events will give rise to problematic overdetermination, because they will
not be mereologically distinct. This is clearly not what Kim has in mind.
One remedy for this problem is of course to give up on the reductive
analysis of causal relata/events into triples of objects, properties, and times. I
suggest, however, that we attempt to keep the focus on causation, and therefore
investigate whether the notion of a minimal sufficient cause can be of use in cashing
out a valid causal exclusion principle.
3. Minimal Sufficient Causes and the Causal Exclusion
Principle
We are trying to find a sound interpretation of the causal exclusion principle. Our
last attempt was promising, but it allowed for a certain range of non-reductive
positions, and combined badly with the view that events/causal relata have objects,
properties, and times as constitutive parts. Can the causal exclusionist do better?
One option would be to focus on the notion of a minimal sufficient cause11 .
Recall the earlier example of the ball smashing a window. Intuitively, its smaller
brother is minimal relative to the ball itself, at least if we stipulate a straightforward
mereological understanding of size. The idea is that the smallest event that is still
sufficient for bringing about the effect is the minimal sufficient cause of that effect.
Let us investigate whether this notion can shed light on what the proper
formulation of the exclusion principle should be. Three tasks present themselves.
11
Sometimes the idea of a minimal cause, or minimal causal account, is understood as an
explanatory notion. We can describe a cause in many different ways. Suppose for example that a
shot causes the apple to fall off Isaac’s head. A minimal causal account would, when minimal is
understood as an explanatory notion, be a description of the cause that just picks out the causally
relevant features of the cause. For example, the direction of the shot is causally relevant, but not its
loudness. So a description such as “the well-aimed and very loud shot caused the apple to fall off
Isaac’s head” will not be minimal (let’s suppose that Isaac was deaf). See [Mackie 1974, pages 260–
265] for a nice discussion of this explanatory notion. The notion of minimality that I discuss in the
text can be thought of as a metaphysical analogue to such an explanatory notion.
Causal Exclusion and the Preservation of Causal Sufficiency
83
(1) We need to know more precisely how to measure the relevant size of events 12 .
(2) We need to find out whether effects always have minimal sufficient causes. (3)
We need to know whether effects always, sometimes, or never have unique minimal
sufficient causes.
The issue about size is complex. Whether an event is smaller than another
event can be understood in several different ways. Here are some candidates:
(i)
A is smaller than B if A is a proper part of B.
(ii)
A is smaller than B if A takes place at a spatiotemporal region that is
a proper subregion of the region at which B takes place.
(iii)
A is smaller than B if A is co-located with B and A is more modally
robust than B.
(iv)
A is smaller than B if the property constitutive of A has an extension
that has the extension of the property constitutive of B as a proper
subset.
Etc.
These candidates all capture the idea of minimality mentioned in the abstract, which
said that a cause is minimal relative to another cause if it is necessitated by that
other cause. The existence of a whole necessitates the existence of its parts;
something happening at region R necessitates the things happening at the proper
subregions of R; a modally fragile event necessitates a coincident but more modally
robust event, etc. 13
It will suffice to restrict the discussion to the first mereological conception
of size. This is not because I find the other notions unpromising, but it will give us a
clearer grasp of the relation, and the points I make apply also if we assume the other
notions 14 .
12
There is no standard conception of event size, so in the following I’ll consider several candidate
stipulations.
13
If one denies mereological essentialism one could hold that the existence of a whole does not
necessitate the existence of all its parts.
14
The relation between some of these notions of size will be important later. Note especially how
(iii) and (iv) might relate to (i) if we have a mereology for properties. Suppose, for example, that we
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When we restrict ourselves to the mereological case, the second question (2)
turns into the question of whether the following claim is true:
Existence of Mereologically Minimal Sufficient Causes: If an effect E has a
sufficient cause C, there are one or more events A1,…, An that are parts of C,
which are causally sufficient for E, and which do not have proper parts that
are causally sufficient for E. 15
This principle seems plausible, but it is not trivial. I’ll spend the next paragraph on a
counterexample. The plausibility of the principle is indicated by the controversial
nature of the existing counterexamples.
In this example I use a purely spatial conception of event size. Assume that
our background metaphysical theory says that objects are gunky and that space-time
is pointy 16 . Suppose further that a minimal (strictly) sufficient cause for E is defined
as the smallest event exactly occurring at a region R*, where region R* contains
region R, and R is a timeslice of E’s past lightcone 17 .
allow events that occupy exactly the same spatiotemporal region to be mereologically related. This is
possible if we have a mereology of properties, because then one event can be a qualitative part of
another event. Here’s one example of qualitative parthood among events: the event of an object
being red at a certain time is a qualitative part of the same object being scarlet at that time. Such
mereological relations between events are parasitic on mereological relations between the properties
that are constitutive of the events. I discuss these issues in more detail in the fourth paper of this
thesis, where a mereological understanding of property realization is put to use in spelling out a nonreductive account of higher-level causation.
15
C might itself be minimal. In that case C will have a part – namely C itself – that doesn’t have
proper parts that are causally sufficient for E.
16
Objects are gunky if all their parts have proper parts, i.e. there are no smallest parts. Space-time is
pointy if the smallest parts of space-time are non-extended space-time points.
17
The past lightcone of E consists of exactly those regions from which it is possible to transmit
signals to E without exceeding the speed of light. A timeslice of the lightcone is an intersection
between the lightcone and some plane of simultaneity. Given relativity theory there will be different
such planes relative to different frames of reference, I allow myself to mostly ignore that
complication here.
Causal Exclusion and the Preservation of Causal Sufficiency
85
Fig.3a.
R*
R
E
R will be a (spatially) closed region, which means that it contains its own closure.
The closure of this region will be the set of points from which E can be reached at
exactly the speed of light. R can be closed since we have assumed a pointy
conception of space. However, we also assumed a gunky conception of objects.
Since events plausibly are located where their constitutive objects are located, and
there cannot be a gunky object that exactly occupies a closed region in pointy space,
there cannot be an event that exactly occupies R. In such an idiosyncratic world
there need not be a minimal sufficient cause of E. For any such region R* there
might be a smaller region R** that still contains R, and the event that occurs exactly
at R** will still qualify as a strictly sufficient cause of E. Consequently one might
get an ever-shrinking series of sufficient causes, having R as their approaching
spatial limit, and there will be no smallest – no minimal – sufficient cause.
So there are certain counterexamples to the general claim that all effects
have one or more minimal sufficient causes. However, since the example rests on
very controversial assumptions, the plausibility of the claim is not seriously altered.
Let us therefore assume its truth for the time being and proceed to consider the third
task: whether effects that have minimally sufficient causes always have unique
minimal sufficient causes.
Uniqueness of Minimal Sufficient Causes: If an effect has a minimal
sufficient cause at a time, then it has a unique minimal sufficient cause at
that time.
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As one might expect from the examples described in section 2, this claim is
arguably false. Recall the case of the table. The different three-leg states are all
equally good candidates for being a minimal sufficient cause, so there’s no
uniqueness there. The same line of reasoning can be applied to the example with the
ball. Suppose you can remove maximum N molecules and still get the same effect,
and that it doesn’t matter which ones you remove. Then there will be a vast number
of minimal sufficient causes for the effect (the number depends on how many
molecules the ball is composed of).
I pointed out in passing that the examples depend on how finely one
individuates the effects. Can this phenomenon give something like uniqueness of
minimal sufficient causes? In other words: might it be the case that maximally
determinate/specific effects always have unique minimal sufficient causes? If so,
we’ll get a version of the causal exclusion principle stating that no maximally
determinate effect has more than one minimal sufficient cause 18 .
One might wonder what such an exclusion principle has to do with mental
causation; do we really have reasons to believe that mental events can be sufficient
causes in this sense? The crucial question is, I claim, whether mental events are
interesting parts of such sufficient causes.
The move we are considering has been a standard move in discussions of
causation. For example, proponents of the counterfactual analysis of causation have
tried to accommodate standard cases of overdetermination, like firing squad cases,
by individuating the effects so finely that all the overdetermining causes come out
as making a difference. In other words: that the effect wouldn’t have happened in
exactly this way had it not been for all the causes 19 .
18
A few words should be said about the determination relation between events. If one thinks of
events as property exemplifications – as triples of objects, properties, and times – then one event E
will determine another event E* if their constitutive objects and times are the same, and the property
constitutive of E is a determinate of the property constitutive of E*. A more general definition of
determination among particulars can be borrowed from Stephen Yablo. He says that (where p and q
are events): “p determines q iff: for p to occur (in a possible world) is for q to occur (there), not
simpliciter, but in a certain way.” [Yablo 1992, page 260] Cashing out this relation in a precise way
is difficult, see [Yablo 1992, pages 260–265] for one way of doing it.
19
See for example [Lewis 1986], [Yablo 1992], and the introduction to [Collins, Hall and Paul 2004]
for discussions.
Causal Exclusion and the Preservation of Causal Sufficiency
87
One way of going extremely determinate is to individuate an effect E in
terms of its micro-physical constituents. This means that any change on the
microphysical level, like replacing, removing or adding a part, or changing some
property of some part, or changing some relation among some parts, will give
another effect. Maybe such finely individuated effects always, or at least in general,
have unique minimal sufficient causes?
If effects are this finely individuated their sufficient causes will have to
include more events. They will have to include all events that potentially could
affect any of the parts or aspects of the effect in the slightest way. It is hard to see
how such sufficient causes can be, at least generally, restricted beyond the totality
of events occurring at a timeslice of the past lightcone of the effect. The past
lightcone is after all defined as the totality of points from which signals can be
transferred to the tip of the cone without exceeding the speed of light.
The framework is now seriously altered. We’re discussing whether
maximally determinate effects can have more than one minimal sufficient cause,
and we now think of sufficient causes as nothing short of timeslices of the past
lightcone of the effect. If these assumptions are correct we can formulate a new
causal exclusion principle:
Causal Exclusion Principle for Maximally Determinate Effects: A
maximally determinate effect cannot have more than one minimal sufficient
cause at any time.
In addition, all other sufficient causes for that effect will have that minimal
sufficient cause as a proper part. This means that preservation might still hold when
we mereologically fuse this minimal cause with additional events outside the
lightcone. Also, preservation will hold if we fuse this cause with different specific
realizers of its parts.
The decision points are now (a), whether the principle is true as it stands,
and (b), whether all (physical) effects are maximally determinate. If nothing short of
total timeslices qualify as sufficient causes for maximally determinate effects, the
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principle seems plausible. The timeslice (or total event exactly occupying it) will
then be a unique minimal sufficient cause 20 . The counter-examples I can think of
rely on quite controversial assumptions. Suppose, for example, that events A and B
stand in a symmetrical necessitation relation, but occur at different locations.
Suppose that both A and B are parts of C, which is the total event occurring at a
timeslice of effect E’s past lightcone at a certain time. Then it seems that both C-A,
which is the proper part of C that lacks A, and C-B, which is the proper part of C
that lacks B, will qualify as different minimal sufficient causes for E.
For the sake of argument, let us give the causal exclusionist the benefit of
the doubt and grant him the causal exclusion principle for maximally determinate
effects. It is still a problem whether all minimal sufficient causes are physical, and
also whether all effects are maximally determinate. In general, what reasons do we
have for thinking that all events are maximally determinate? 21
One might hold that the best reason for thinking so is that any determinate
event causally, and thereby metaphysically, excludes all events of which it is a
determinate 22 . But, as we already have seen , and as I will argue in more detail later,
that issue hangs on whether the effects are maximally determinate. In light of that, it
is question begging to assume that all effects, which themselves are events, are
maximally determinate in order to argue that all events are maximally determinate.
After all, how many non-caused events do we stumble upon? Events, in general, are
effects.
20
This will be relative to a chosen frame of reference. A frame of reference must be chosen if the
timeslice is to be uniquely determined.
21
Here is another way of asking the question. Suppose that you individuate some part of the total
timeslice event causally, i.e. at least partly in terms of it causing the relevant effect E. If this causally
(relationally) individuated event can be multiply realized, then we don’t have to include the
maximally determinate events that take place at this timeslice: it will be enough to include events at
all regions, but not all specific realizers. If that’s right, then a causal exclusion principle might hold,
but it will be up for grabs whether there always is a minimal sufficient physical cause. The idea is
that some part of the minimal total timeslice cause might be a realizable mental event, because it
does not matter what specific physical realizer that mental event had on this occasion. In section 5 of
this paper I give some examples intended to establish the existence of such realizable minimal
sufficient causes. See also the Infection Argument in the third paper of this thesis, which aims to
establish the existence of determinable effects based on Yablo’s proportionality principle for
causation.
22
One reason for thinking that causal exclusion entails metaphysical exclusion is the so-called causal
criterion of existence. The idea is that everything that exists has causal powers. See e.g. [Alexander
1920], [Armstrong 1978] and [Kim 1998, page 119].
Causal Exclusion and the Preservation of Causal Sufficiency
89
It therefore seems to me that the issue has to be judged on independent
grounds. Doing so would take us too far astray from the main concern of this
paper 23 . The principle in its current form is irrelevant for determinable effects, so
events involving modally robust objects such as persons, organisms, and other
ordinary macro-objects, or events involving determinable properties, would all have
to be ruled out of the causal nexus at the outset if this principle is to yield the
exclusionist conclusion. That commitment seems to put the burden of argument
directly on the causal exclusionist.
However, even if it is unreasonable to rule out all determinable effects, it
doesn’t follow that the revised exclusion principle is false. What led us to consider
maximally determinate effects was the question of the uniqueness of minimal
sufficient causes. In order to get the causal exclusion argument going the causal
exclusionist might instead put additional argumentative burden onto the principle of
the causal closure of physics. One version of that principle would guarantee the
existence of a minimal sufficient physical cause for any physical effect that has a
sufficient cause. Clearly, effects can only have one unique minimal sufficient cause;
that follows by definition. We have already discussed reasons to regard minimal
sufficient causes as having priority over causes that are sufficient but not minimal.
Consequently, if there is more than one minimal sufficient cause for a given effect,
mental sufficient causes will be second-rate only if they are not minimal sufficient
causes. Whether they can be minimal is dictated by what version of the principle of
the causal closure of physics one accepts. For these reasons I devote the second half
of this paper to a discussion of the causal closure/self-sufficiency principle, and
whether it allows for interesting accounts of mental causation or not.
23
I address this issue in more detail in the third paper of this thesis.
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90
4. Causal Self-Sufficiency of Physics
In order to formulate a sound causal exclusion argument, the exclusionist needs a
closure principle that combines with the causal exclusion principle in the right way.
It is therefore of great importance to get clear on the strength of the so-called
principle of the causal closure of physics. There are several parameters across
which the strength of the principle may vary. What I aim to establish is that only
certain strong versions of the principle combine in the appropriate way. Moreover,
these strong versions can reasonably be questioned.
First, the domain of the closure principle may vary. Does it concern the
domain of contemporary quantum mechanics or the domain of some future physical
theory? Does it concern micro-physics or physics broadly understood, i.e. as
comprising
also
chemical,
geological,
biological,
neurophysiological
etc.
phenomena? Discussions of these questions can be found in [Crane & Mellor 1990],
[Sturgeon 2000], [Papineau 2001] and, very briefly, in [Kim 2005]. It is surely
important to have a clear conception of what phenomena are included in the microphysical domain. Further work has to be done on this question. Suffice it to note
that macro-phenomena that are identical to mereological sums of micro-phenomena
should themselves be included in the causally closed domain, since these can be
individuated in entirely microphysical terms, and therefore plausibly are caused by
the causes responsible for their constituents. However, there is a question whether
other objects that cannot be individuated in entirely microphysical terms should be
included in the physical domain, and whether such an inclusion might create trouble
for the causal closure principle 24 . These issues become important later in this
section when I evaluate the different versions of the causal self-sufficiency
principle.
24
The kind of phenomena I have in mind will have micro-physical parts, but they will not have all
their microphysical parts essentially. They will therefore not be identical to these parts but rather
realized or constituted by them. These phenomena might not be individuated in entirely
microphysical terms, because it might not be micro-physical facts that determine whether some part
is essential or contingent to them.
Causal Exclusion and the Preservation of Causal Sufficiency
91
Another concern is the modal strength of the principle. If the principle holds,
is it a contingent fact about the actual world? Or maybe it holds with nomological
necessity? Or maybe it holds with metaphysical necessity? I will not be concerned
with these questions either. Suffice it to note that most physicalists intend their
physicalism to be a metaphysically contingent thesis, so they will at least reject the
claim of metaphysical necessity.
I focus on different versions of the causal closure principle in relation to the
distinctions between sufficient causes, minimal sufficient causes, and unique
minimal sufficient causes. The strength of the different versions will vary in
accordance with the different conceptions of causal sufficiency.
Let me first state the closure principle in its strongest form:
Causal Closure of Physics: If A is causally related to B, and B is physical,
then A is physical.
This is the natural understanding of a closure principle, namely that the domain in
question is closed under the relation in question. This principle, however, begs the
question against non-reductive accounts of mental causation. It follows directly that
there cannot be any non-physical events that are causally related to physical events.
In order not to beg the question, one should use a weaker closure principle as
premise in the exclusion argument 25 .
In the most recent formulation by Kim, the causal closure principle reads:
Closure. If a physical event has a cause that occurs at t, it has a physical cause that
occurs at t. [Kim 2005, page 43]
Strangely enough, this formulation of the principle is too weak to do the
argumentative work it is put to. It allows for scenarios where a physical event has
25
However, Kim’s formulation of causal closure in chapter 2 of [Kim 1998] is equivalent to the
principle just stated. He writes: “One way of stating the principle of physical causal closure is this: If
you pick any physical event and trace out its causal ancestry or posterity, that will never take you
outside the physical domain. That is, no causal chain will ever cross the boundary between the
physical and the non-physical.” [Kim 1998, page 40]
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two non-sufficient causes, one mental and one physical, that together make up a
sufficient cause. If the principle is to combine in an argument with the causal
exclusion principle, the causal closure principle should appeal to a conception of
sufficient cause. This justifies a name change for the principle. I suggest labeling the
proper principle the causal self-sufficiency of physics.
(1) Causal Self-Sufficiency of Physics: If a physical event has a sufficient
cause that occurs at t, then it has a sufficient physical cause that occurs at t.
It is by drawing distinctions between different precise versions of this principle that
the following discussion contributes to the debate. In the next section I discuss in
what sense the weaker versions allow for interesting non-reductive accounts of
mental causation. In this section I make the distinctions, and I provide reasons to be
skeptical about the stronger versions of the principle.
As one might expect, the distinctions between sufficient causes, minimal
sufficient causes, and unique minimal sufficient causes give rise to seven other
specifications of the self-sufficiency principle. First I state the strongest versions
that can be used to rule out interesting non-reductive accounts of mental causation:
(2) Strong Unique Minimal Causal Self-Sufficiency of Physics: If a physical
event has a sufficient cause that occurs at t, then it has a unique minimal
sufficient physical cause that occurs at t.
(3) Unique Minimal Causal Self-sufficiency of Physics: If a physical event
has a minimal sufficient cause that occurs at t, then it has a unique minimal
sufficient physical cause that occurs at t.
(4) Weak Unique Minimal Causal Self-sufficiency of Physics: If a physical
event has a unique minimal sufficient cause that occurs at t, then it has a
unique minimal sufficient physical cause that occurs at t.
Causal Exclusion and the Preservation of Causal Sufficiency
93
The following two versions allow for interesting non-reductive accounts of mental
causation, and the same is true of (1) above:
(5) Weak Causal Self-Sufficiency of Physics I: If a physical event has a
minimal sufficient cause that occurs at t, then it has a sufficient physical
cause that occurs at t.
(6) Weak Causal Self-Sufficiency of Physics II: If a physical event has a
unique minimal sufficient cause that occurs at t, then it has a sufficient
physical cause that occurs at t.
The final two versions allow for non-reductive accounts of mental causation only if
uniqueness of minimal sufficient causes fails:
(7) Minimal Causal Self-Sufficiency of Physics: If a physical event has a
sufficient cause that occurs at t, then it has a minimal sufficient physical
cause that occurs at t.
(8) Weak Minimal Causal Self-sufficiency of Physics: If a physical event
has a minimal sufficient cause that occurs at t, then it has a minimal
sufficient physical cause that occurs at t.
I will now consider the plausibility of the stronger versions of the Causal SelfSufficiency principle.
Some physical effects have minimal sufficient causes that are realizable. I’ll
give two examples of this in the following. In light of these examples the
exclusionist might respond that the proper domain of the causal self-sufficiency
principle includes only maximally determinate entities, which are here understood
as entities individuated entirely in terms of their microphysical constituents. The
exclusionist can then either argue that (1) whatever causes a determinable effect
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94
causes its specific realizers/constituents, or that (2) the only relevant effects are
maximally determinate effects.
I’ll consider the first line of exclusionist response here, while I discuss the
second line in paper III. In section 4 of paper III I give two examples that are
intended to illustrate that also maximally determinate physical effects can have
determinable (or realizable) higher level causes. Here, however, I focus on two
examples of physical effects that have determinable (or realizable) causes, and I
discuss the first exclusionist response.
Suppose that the temperature of a gas causes a certain effect, for example
that the temperature of the surroundings increases by two degrees in a certain time.
Call this effect E. Suppose further that the temperature of the gas is equal to the
mean kinetic energy of the molecules in the gas, and call this (MKE). There is also
a specific distribution of kinetic energies among the gas-molecules that gives rise to
the mean kinetic energy, call this specific distribution (SD). (MKE) and (SD) are
both properties that the gas (G) has at time t. Consequently, we have two competing
cause candidates:
[(SD), G, t] →causes E
[(MKE), G, t] →causes E
We know that (SD) entails (MKE), that’s just a question of simple mathematics.
Consequently, if [(MKE), G, t] is sufficient for E, then [(SD), G, t] is too. However,
[(SD), G, t] is, in a certain sense, more than sufficient. It is not a minimal sufficient
cause of E. Rather, it is sufficient for something that might be a minimal sufficient
cause of E, namely [(MKE), G, t]. The point is that the temperature, the average
kinetic energy, is sufficient for the effect. It does not matter what specific
distribution of kinetic energy there is between the gas molecules. The specific
distribution is therefore more than sufficient for the effect, and thus not a minimal
sufficient cause.
Causal Exclusion and the Preservation of Causal Sufficiency
95
Here is another example that is more directly relevant for philosophy of
mind. According to the much-debated view of Benjamin Libet, the duration of
neuronal activations is a plausible candidate for a neuronal basis for awareness. He
says,
I have proposed a completely different option for explaining the 05-sec activity
requirement for awareness: The durations of similar activations may itself be the
basis. That is, when the duration of repetitive similar activations of appropriate
neurons reaches a certain value, then the phenomenon of awareness emerges. The
required duration would be the “neuronal code” for the emergence of awareness.
This option fits with all the presently available evidence. It is, therefore, a viable
option, although it cannot be said to be an adequately proven mechanism. [Libet
2004, page 58–59]
It is interesting to see how this basis is modally robust compared to its specific
realizers. As Libet himself points out, neither the specific frequency nor the number
of pulses is necessary for awareness, in contrast to the duration of activation. In this
way it becomes clear that as long as the activation goes on for the required time,
there could have been alterations in the specific frequency and number of pulses
realizing this specific train of activation. Thus the basis suggested by Libet can be a
minimal sufficient cause in the presence of its causally sufficient (but not minimal)
realizer.
The exclusionist might reply that such determinable effects have maximally
determinate realizers or subvenient properties, and that whatever causes such an
effect causes its determinate/subvenient sibling. This reasoning, however, is a
fallacy when it concerns causal sufficiency. The following inference pattern is
invalid:
I1
A →causally B
INVALID
C → metaphysically B
∴ A →causally C
A cause might be sufficient for the smashing of a window, while not being
sufficient for a specific way in which the smashing might happen. Actually, I think
Paper II
96
there is an under-appreciated point here. Clearly, if A is causally sufficient for B
and B is metaphysically necessitated by C, it does not follow that A is causally
sufficient for C. Here’s another example. A cause might be sufficient for something
being red, but not for it being a specific shade of red. There has been, however, a
tendency to overlook this point in the debate.
Consider the seemingly uncontroversial point Kim makes in the following
quote:
To cause a supervenient property to be instantiated, you must cause its base
property (or one of its base properties) to be instantiated. To relieve a headache,
you take aspirin: that is, you causally intervene in the brain process on which the
headache supervenes. That’s the only way we can do anything about our
headaches. [Kim 1998, page 42-43]
Now, as a general point about causal influence this might be innocent, and correct,
but it is a source of confusion if we are mistakenly led into thinking that it transfers
also to causal sufficiency. Suppose that a cause is sufficient for relieving a
headache. The headache might get relieved in several different ways, and
consequently the sufficient cause does not have to be sufficient for a specific way of
relieving the headache. More generally, let us suppose that a supervenient property
M has the set consisting of P1, P2, and P3 as supervenience base, and that P1 is the
base property instantiated at this occasion. Suppose further that A is causally
sufficient for M. From these facts alone one cannot infer that A is causally
sufficient for P1, since it would be an instance of the earlier invalid schema I1.
The problem is that A, by being causally sufficient for M, reasonably is
causally sufficient for {P1 or P2 or P3}, but A does not have to necessitate either
one of these individually in order to necessitate M; it is enough to necessitate one
disjunct or another. So Kim’s quote should not be read as saying: to be causally
sufficient for a supervenient property getting instantiated is to be causally sufficient
for its specific supervenience base.
Having seen reasons for questioning the stronger versions of the causal selfsufficiency principle, what do non-reductive accounts of mental causation look like
when we assume the weaker versions?
Causal Exclusion and the Preservation of Causal Sufficiency
97
5. Causal Self-sufficiency for Believers in Non-reductive
Accounts of Mental Causation
No matter what version of the causal self-sufficiency of physics one accepts, it
might be that there are mental events that are causally sufficient for the effect in
question. That possibility is only ruled out by the stronger causal closure principle.
Accepting versions (2), (3), and (4) of the causal self-sufficiency principle each
allow for rather idiosyncratic, or just plainly uninteresting, accounts of mental
causation. They are uninteresting because they say that mental events can be
causally sufficient only in virtue of having a purely physical causally sufficient
event as a proper part (which is fused with a causally irrelevant mental event).
These are not worthy accounts of mental causation 26 .
Therefore, I recommend that the non-reductionist who believes in mental
causation accepts version (1), (5), (6), (7) or (8). These versions all allow for the
view that all physical effects have sufficient physical causes, while being silent on
whether all physical effects have minimal or unique minimal sufficient causes.
If the non-reductionist accepts (1),
(1) Causal Self-Sufficiency of Physics: If a physical event has a sufficient
cause that occurs at t, then it has a sufficient physical cause that occurs at t
he can coherently claim that some physical effects (typically actions) have
sufficient mental causes, he can claim that some physical effects have minimal
26
More precisely, such accounts are not worthy because such mental causes would always have
minimal sufficient physical causes as proper parts. Consequently, no purely mental event would be
causally relevant in virtue of being mental. The same problem is not as pressing when it comes to the
later discussion of the lack of minimal sufficient physical causes for certain effects, the reason being
that physical events, in general, are causally relevant as such. Here are tentative definitions of
minimal sufficient mental and physical causes. (1) A minimal sufficient cause is mental if and only if
it has at least one mental part essentially. (2) A minimal sufficient cause is physical if and only if all
its essential parts are physical. An essential part of a cause is here understood as a part without
which the cause would not have the effect in question.
Paper II
98
sufficient mental causes, or he can even claim that some physical effects have
unique minimal sufficient mental causes 27 . None of these claims are in conflict with
(1).
If he accepts (5),
(5): Weak Causal Self-Sufficiency of Physics: If a physical event has a
minimal sufficient cause that occurs at t, then it has a sufficient physical
cause that occurs at t
then he can also coherently claim that some physical effects have sufficient mental
causes, or that some physical effects have minimal sufficient mental causes, or that
some physical effects have unique minimal sufficient mental causes.
If he accepts (6),
(6) Weak Causal Self-Sufficiency of Physics II: If a physical event has a
unique minimal sufficient cause that occurs at t, then it has a sufficient
physical cause that occurs at t
then he can still, as for the two other versions, coherently claim that some physical
effects can have all three kinds of sufficient mental causes.
If uniqueness fails, then the last two versions of the causal self-sufficiency
principle allow for coherent accounts of mental causation. If the non-reductionist
accepts (7),
(7) Minimal Causal Self-Sufficiency of Physics: If a physical event has a
sufficient cause that occurs at t, then it has a minimal sufficient physical
cause that occurs at t
27
A sufficient cause is mental if it has a mental part essentially, and the physical realizer of that
mental part is not essential. Notice that there is an asymmetry here: a cause is physical if and only if
all its essential parts are physical.
Causal Exclusion and the Preservation of Causal Sufficiency
99
then he can claim that some physical effects also have minimal sufficient mental
causes, and also, less interestingly, that they have sufficient mental causes.
If he accepts (8),
(8) Weak Minimal Causal Self-Sufficiency of Physics: If a physical event has
a minimal sufficient cause that occurs at t, then it has a minimal sufficient
physical cause that occurs at t
then he can claim that (at least) some physical effects lack unique minimal
sufficient causes, and that (at least) some of those physical effects have minimal
sufficient mental causes.
8. Conclusion
I have shown, by pointing to so-called preservation cases, that Kim’s latest
formulation of the causal exclusion principle is false. I have discussed various
options which address this flaw. This discussion showed why the causal exclusion
argument depends on strong versions of the principle of the causal closure of
physics. In the second half of the paper I distinguished between several versions of
the causal self-sufficiency principle, and argued that there are independent reasons
to doubt the versions of the causal self-sufficiency of physics that give rise to a
valid causal exclusion argument. My discussion was intended to give us a clearer
grasp on exactly what commitments non-reductive accounts of mental causation
have to make. I think it also gives us a clearer grasp of the commitments
accompanying the causal exclusion argument.
100
Paper II
REFERENCES
Alexander, Samuel [1920] Space, Time and Deity Vol. II, MacMillan & Co. Limited, St.
Martin’s Street, London.
Armstrong, D.M. [1978] A Theory of Universals. Universals and Scientific Realism
Volume 2, Cambridge University Press.
Collins, John, Ned Hall and L.A. Paul [2004] Causation and Counterfactuals MIT
Press.
Crane, Tim & Hugh Mellor [1990] “There is no Question of Physicalism,” Mind, New
series, Vol.99, No.394 (April 1990), pp 185–206.
Jackson, Frank [1998] From Metaphysics to Ethics, Oxford.
Kim, Jaegwon [1998] Mind in a Physical World, MIT Press.
___
[2005] Physicalism or Something near Enough, Princeton University Press.
Lewis, David [1986] “Causation” with postscripts in Philosophical Papers Volume II,
Oxford University Press.
Libet, Benjamin [2004] Mind Time, Harvard University Press.
Mackie, J.L. [1974] The Cement of the Universe, Clarendon Press, Oxford.
Merricks, Trenton [2003] Objects and Persons, Oxford University Press.
Papineau, David [2001] “The Rise of Physicalism” in Carl Gillett and Barry Loewer (eds)
Physicalism and its Discontents, Cambridge University Press.
Sider, Ted [2003] “What’s so bad about Overdetermination?”Philosophy and
Phenomenological Research 67.
Simons, Peter [2003] Parts, a Study in Ontology, Oxford University Press.
Sturgeon, Scott [2000] Matters of Mind, Routledge.
Yablo, Stephen [1992] “Mental Causation,” The Philosophical Review, Vol.101, No.2, pp
245–280.
___
[1997] “Wide Causation,” NOÛS Vol. 31, Supplement: Philosophical Perspectives,
11, Mind, Causation, and World, pp. 251–281.
PAPER III
Proportionality and the
Metaphysics of Causation℘
Anders Strand
ABSTRACT
Stephen Yablo’s account of mental causation consists of three main parts. (i) The claim that
determinables and determinates do not compete for causal influence, as opposed to the
competition for being ‘the cause’ of a certain effect. (ii) The claim that mental properties
relate to physical properties as determinables to determinates. (iii) The proportionality
principle which says that causes are proportional to their effects with regard to how
determinate or fine-grained they are. The proportionality principle thereby explains why
determinables are causes in the presence of their determinates.
In this paper I address a response to Yablo saying that a non-trivial proportionality
principle is a purely explanatory constraint. If so Yablo’s view is but one version of the
uncontroversial view that mental causal explanations play an explanatory role over and above
physical causal explanations. I evaluate whether the proportionality principle is useful as a
guiding principle for the metaphysical question about mental causation: can mental
properties be causally efficacious in the presence of their physical realizers/determinates? I
argue for two conditional claims, both of which throw into relief the commitments of a
Yablo-style account of mental causation. The conditional claims are: (a) if there are
determinable causal relata then there is a plausible metaphysical reading of the
proportionality principle; and (2) if the proportionality principle is a non-trivial metaphysical
principle then there are determinable effects. These two claims provide reasons for thinking
that Yablo’s account of mental causation goes hand in hand with a certain pluralistic view of
causal relata; a view which is under direct attack by the causal exclusion argument. The
crucial issue, therefore, is whether the existence of determinable causal relata and/or the
proportionality principle – understood as a non-trivial metaphysical principle – has
plausibility independently of the mental causation issue.
1.
2.
3.
4.
5.
6.
7.
℘
Introduction
Outline of Yablo’s View
Setting the Stage
Where do Determinable Effects come from? The Infection Argument
The Proportionality Principle: Explanatory or Metaphysical Constraint?
Prospects for the Alternative Token-Identity View
Conclusion
Thanks to Carsten Hansen, Jon Lindstrøm, Anders Nes and Øistein Galaaen.
Paper III
104
1. Introduction
Linda has a desire for fresh air, and she has the belief that opening the window will
provide fresh air. Linda opens the window. When asked why Linda opened the
window, her friend Paul says she opened the window because she had a desire for
fresh air and she believed opening the window would provide fresh air. When asked
what caused Linda to open the window, Paul answers in the same way, that her
having that belief-desire pair caused it. However, Paul and Linda’s neurophysiologyfan-friend John is critical of Paul’s common-sensical explanations. According to
John, Linda opened the window because she was in a complex neurophysiological
state NPS. Further, John says: “being in NPS might realize having that belief-desire
pair on this occasion, but NPS does all the causal work; the belief-desire pair itself is
entirely causally redundant.” Linda is perplexed by the disagreement between Paul
and John, and wonders what kind of argument could possibly settle their dispute.
In this paper I’m interested in a specific line of reasoning on Paul’s behalf.
Suppose Paul says: “Well, NPS surely had something to do with the effect. However,
in general effects depend counterfactually on their causes, so the crucial question is:
would the effect have happened without NPS?” The reasonable answer, Paul claims,
is “yes, the effect would have happened as long as Linda had the relevant beliefdesire pair, and the context was relevantly similar”. As we will soon see, this line of
reasoning is reminiscent of the way Yablo uses his proportionality principle.
There is a counter-response on John’s behalf that creates certain problems for
Paul, and also for Yablo 1 . Suppose John says: “Well, I agree that causal relations in
general are accompanied by relations of counterfactual dependence. However, the
relevant effect is not a coarse-grained event; the relevant effect is this specific
window opening; the window opening that happened at this particular time, at this
1
Another response on John’s behalf is to question the counterfactual dependence aspect of causal
relations, either by denying it or by claiming that “causation” is ambiguous and that the notion relevant
for the exclusion problem is something like “sufficient cause “ or “productive cause” which does not
directly involve counterfactual dependence.
Proportionality and the Metaphysics of Causation
105
particular speed, with Linda’s arms moving along this particular pathway etc. This
effect depends counterfactually on NPS!”
This counter-response opens up a whole new can of worms. Is there more than
one effect occurring here? What are the criteria of individuation for such effects?
What are the relations between these effects? What determines whether one effect is a
legitimate object of explanation in a certain explanatory context? In this paper I focus
on two questions: “Is there more than one effect?” and its sibling: “Why think that
there is more than one effect occurring?” 2
I proceed by presenting Yablo’s view, and then confront his view with the
kind of response voiced by John above. This will lead into a discussion of our reasons
to hold the kind of metaphysical pluralism of events involved in Yablo’s account and
will point to the fact that Yablo’s view only works if we assume, or are able to
independently establish, a certain metaphysical background picture. I point out that a
more sparse metaphysics is the main alternative to Yablo’s view. However, there are
certain costs to such an alternative view, especially as it pertains to the understanding
of causation itself.
First, then, a detailed review of Yablo’s view. Readers already familiar with it
might want to skip this section and jump to section 3.
2. Outline of Yablo’s View
One clarification should be made at the outset. Usually when one singles out a cause
of a given effect one has to choose between different parts of a sufficient cause.
Thinking of INUS conditions might be helpful here. An event is an INUS condition if
it is an insufficient but non-redundant part of a sufficient but unnecessary condition
for a given effect 3 . What INUS condition one picks out as ‘the cause’ on a certain
occasion is a questions of pragmatics. In contrast, the question I discuss in relation to
2
Someone might argue that there is more than one effect because this gives us a coherent story about
mental causation. That, however, is question begging in the present context.
3
See [Mackie 1974] for an analysis of causes as INUS conditions.
Paper III
106
Yablo’s view is whether such INUS conditions belong to a specific level in the
determinable-determinate hierarchy. The question whether the proportionality
principle is a non-trivial metaphysical guide is understood as the question whether
there are such hierarchies of co-occurring cause-candidates related by the
determinable-determinate relation.
The reason I require it to be a non-trivial guide is that one could deny the
existence of such determinable-determinate hierarchies of cause candidates, while
still accepting that the proportionality principle is a metaphysical principle that just
picks out the single cause-candidate occurring at a specific region.
Yablo presented his account of mental causation in his article “Mental
Causation” [Yablo 1992]. He supplemented the view in 1997 in “Wide Causation”
[Yablo 1997], where he also discusses the causal efficacy of externally individuated
mental events. I base my exposition of Yablo’s view on these two articles. According
to Yablo, being proportional to the effect is a requirement on causes. Yablo defines
proportionality as follows, where the Ci’s are alleged causes of a given effect E 4 :
(1) C1 screens C2 off from E if and only if, had C1 occurred without C2, E
would still have occurred.
(2) C is required for E if and only if none of its determinables screens it off,
and C is enough for E if and only if it screens off all of its determinates.
(3) C is proportional to E if and only if it is both required by and enough for
E.
Accordingly, an effect can be caused by a proportional cause C, rather than by the
most determinate cause candidate Ci available. This is the feature that will be of
present interest 5 .
4
The following formulation is from [Yablo 1997]. The standard explication of the determinabledeterminate relation can be found in W.E. Johnson’s Logic [Johnson, 1921]. The relation between the
property of being red and the property of being scarlet is one example; another is the relation between
the property of having a shape and the property of being rectangular.
5
The principle can also be used to disqualify a cause-candidate that is too coarse-grained and thus
disproportional to the effect. This can be used in an attempt to establish that fine-grained-cumexternally-individuated mental events can be causally efficacious. The line of reasoning would be that
Proportionality and the Metaphysics of Causation
107
In addition, Yablo argues that mental properties have physical properties as
determinates. This view provides resources for arguing that, at least in some cases,
instantiations of determinable mental properties are causes rather than the
instantiations of their physical determinates.
Yablo’s intuitive understanding of property determination is stated in his
“guiding principle” for the determination relation [Yablo 1992, page 252]:
( ) P determines Q iff: for a thing to be P is for it to be Q, not simpliciter, but
in a specific way.
More precisely defined, Yablo’s concept of metaphysical determination among
properties is defined in [Yablo 1992, page 252] as:
(∆) P determines Q (P > Q) only if:
(i) necessarily, for all x, if x has P then x has Q; and
(ii) possibly, for some x, x has Q but lacks P.
He points out that this metaphysical understanding of determination captures the joint
idea of supervenience and multiple realization 6 . Accordingly, he is sympathetic to the
non-reductive physicalist’s idea that mental properties are supervenient on, and
multiply realized by, physical properties.
Yablo then uses a generalization-ad-absurdity argument to argue that
determinates don’t causally exclude their determinables. The core idea is that (almost)
whenever you have a cause you can find a more determinate property whose
instantiation is sufficient for the effect in question, and thus that (almost) no apparent
some behavioral effects are so fine-grained that the intentional properties (for example) of a mental
event make a causal difference.
6
He says “Such a view is in fact implicit in the reigning orthodoxy about mind-body relations, namely,
that the mental is supervenient on, but multiply realizable in, the physical. Because neither thesis
concerns determination directly, the point is easily missed that in combination their effect is to portray
mental properties as determinables of their physical realizations.” [Yablo 1992, page 254]
108
Paper III
examples of causal relations are genuinely causal – not even examples that are
commonly taken as paradigmatic. He says 7 :
(…) if even paradigm cases of causal relevance fail the exclusion test, what
passes it? Not much, it turns out. Almost whenever a property Q is prima facie
relevant to an effect, a causally sufficient determination Q’ of Q can be found to
dispose it as irrelevant after all. Applying the argument to Q’, Q’’, etc. in turn, it
appears that only ultimate determinates – properties unamenable to further
determination – can hope to retain their causal standing. [Yablo 1992, page 258]
The view that only ultimate determinates are causally efficacious has been defended,
notably by Armstrong in [Armstrong 1978] 8 . Yablo gives a very brief argument
against that view. The idea is that instances of ultimate determinates incorporate too
much irrelevant detail. For that reason one can abstract away some of the irrelevant
details and get to a determinable property that causally excludes the ultimate
determinate. Accordingly, there will be no causally efficacious properties anywhere.
In other words, the causal exclusion argument generalizes in absurd ways.
For Yablo there is no competition for causal influence between determinables
and their determinates 9 . He puts it nicely by analogy:
Take for example the claim that a space completely filled by one object can
contain no other. Then are even the object’s parts crowded out? No. In this
7
‘Failing the exclusion test’ is to be understood as being causally excluded by another causecandidate. It will suffice to think of the argument given by John in the introduction, where he argued
that NPS causally excluded the belief-desire pair as cause of Linda’s action.
8
For Armstrong [Armstrong 1978] causal relations are instances of second-order relations among
universals. According to Armstrong, determinables are not universals, and it is therefore ruled out that
they can engage in causal relations. He says: “I begin by denying that there are any determinable
universals. All genuine universals are determinates. There are such predicates as ‘coloured’ or ‘red’,
but there is no property, being coloured or being red. To assert that a particular is red is to assert that
the particular has some property, a property which is a member of a certain class of properties: the
class of all the absolutely determinate shades of red. “ [Armstrong 1978, page 117]
9
Notice that there is a possible worry lurking in the background. Examples using color, like the
relation between red and scarlet, can be called intra-categorical determination. This means that the
determinable property and the determinate both belong to the same category (color in the present
example). However, if mental properties relate to physical properties as determinables to determinates
this seems to qualify as cross-categorical determination. It is not entirely clear that the claimed
intuitive lack of causal competition between intra-categorical determinables and determinates naturally
transfers to cases of cross-categorical determination. Reasonably, especially in light of the vivid debate
about mental causation, the claim that there is no causal competition between determinables and their
determinates seems less well established for the cross-categorical determination relation between
mental and physical properties.
Proportionality and the Metaphysics of Causation
109
competition wholes and parts are not on opposing teams; hence any principle
that puts them there needs rethinking. Likewise any credible reconstruction of
the exclusion principle must respect the truism that determinates do not contend
with their determinables for causal influence. [Yablo 1992, page 259]
This claim might appear puzzling in light of his proportionality principle. Isn’t the
principle intended to show that the proportional cause wins in competition with its
determinate and determinable siblings? The idea of one property causally screening
off another property seems itself to motivate causal exclusion. I think that Yablo
would agree that this tension is resolved once we realize the ambiguity in the
expression ‘causal competition’. When discussing the issue one should distinguish
between ‘being the cause’ and ‘causally influencing’. For Yablo, determinables and
determinates do not compete for causal influence, but they do compete for the status
of being ‘the cause’ 10 .
This remark is important because it seems to be physical causal influence or
sufficiency that is claimed to out-compete mental causation. The disagreement over
that issue remains fundamental between Yablo and the causal exclusionist. It
therefore calls out for a positive explanation why there is no competition over causal
influence and sufficiency. The kind of generalization-ad-absurdity argument stated
above doesn’t provide such a positive understanding, and is therefore not fully
satisfactory. Nonetheless, I will not pursue this problem here; I give a positive
account in the fourth paper of this thesis 11 .
The last bit of information we need about Yablo’s view concerns the
determination relation between particulars. It is defined by Yablo in the following
way [Yablo 1992, page 265]:
10
Again the status of being ‘the cause’ is to be interpreted in the way pointed out at the beginning of
this section. I discuss the worry that also this conception of ‘the cause’ is purely pragmatic later in this
paper by contrasting Yablo’s view with an identity based view.
11
If one understands causal sufficiency as a species of nomological sufficiency, the underlying
exclusionist intuition can be cashed out in terms of a nomological determination argument.
Reasonably, if something is nomologically determined by a physical determiner, then additional
mental determination seems entirely superfluous. The general idea behind my response to such an
argument, in the fourth paper, is to show that mental properties relate to their physical realizers as parts
to wholes, and thus that there is no mysterious overdetermination involved whatsoever.
Paper III
110
(δ) p > q only if:
(i)
necessarily, if p exists, then q exists and is coincident with p;
(ii)
possibly, q exists and p does not exist.
Yablo spells out how this relation can obtain by using the notion of essence 12 .
(ε) p > q only if: necessarily, p exists iff q (both) exists and exemplifies the
difference S between its own essence and p’s larger essence.
We now have enough background on Yablo’s position to discuss the response I’m
interested in in this paper. We know how Yablo understands the determination
relation between properties, how he understands the determination relation between
particulars, and we know what he means by proportionality. Let’s turn now to see
how the proportionality principle interacts with the individuation of the relevant
effects.
3. Setting the Stage
Recall the example I gave in the introduction. Linda performed an action: she opened
the window, call this E. Just before she performed that action she was in a certain
neurological state NPS, which by assumption realized her having a certain beliefdesire pair, call the belief-desire pair BDP. According to Paul, who represents the
non-reductionists about mental causation, BDP caused E. John, who represents the
exclusionist, on the other hand, holds that NPS was the real cause of E.
The example can be nicely described in Yablo’s terminology. NPS determines
BDP since everyone who’s in neurophysiological state NPS necessarily is in mental
12
For Yablo an essence is a collection (not the totality) of an object’s essential properties (the
properties it cannot exist without). For example, an object is of a certain kind in virtue of its essence
and the kind properties should therefore not be included in the essence itself. According to Yablo, the
essence is the set of properties of an object that are both essential and cumulative. For details see
[Yablo 1992, pages 261–265].
Proportionality and the Metaphysics of Causation
111
state BDP, and it is possible that someone can be in mental state BDP without being
in neurophysiological state NPS because BDP could have been realized by another
neurophysiological state 13 . The proportionality principle can then kick in as a guide
to answering the question: what was the real cause of E, NPS or BDP?
To find out we ask ourselves: if BDP had occurred without NPS, would E still
have occurred? If the answer is ‘yes’, BDP trumps NPS as the cause of E. If the
answer is ‘no’, NPS trumps BDP as the cause of E. This seems straightforward and
reasonable. One interesting observation, however, is that both Paul’s original
response and John’s counter-response depend on how tightly we individuate the effect
E.
Let us make some further assumptions in order to bring the point out clearly.
Let us assume that E1 is properly described by ‘Linda opened the window’, so E1 is a
coarse-grained event in the sense that E1 would still have occurred even if Linda had
opened the window in a slightly different way. For the sake of illustration, let us
assume that BDP is proportional to E1. Let us also assume that E2 is properly
described by “Linda opened the window by moving her arms along the precise
pathway P at the precise speed S at time t.” E2 is fine-grained in the sense that E2
would not have happened if either the pathway P, the speed S or the time t had been
slightly altered. For the sake of illustration, let us assume that NPS is proportional to
E2.
Allowing ourselves these assumptions we can look for a way of settling the
disagreement between John and Paul by answering the following two questions.
Q1: Is there more than one effect (window-opening) taking place?
Q2: If so, what determines which effect (window opening) is the legitimate
object of explanation in a certain context?
13
I’m here idealizing away from potential problems that might arise with the acceptance of external
individuation of mental states and events. There is also a further complication that I abstract away from
here: BDP might have a mental determinate BDP*, and, as has been argued in [Bechtel and Mundale,
1999], BDP* might not be multiply realizable by physical realizers.
Paper III
112
The idea in Q2 is that it is a metaphysical question whether a cause is proportional to
a given effect, but what effect one takes explanatory interest in is due to pragmatic
concerns. Yablo’s account of mental causation – if it is to have application – arguably
relies on the fact that there are coarse-grained (determinable) behavioral effects
around. On the other hand, it seems clear that most coarse-grained effects have finegrained determinates; in the same way as most coarse-grained causes have finegrained determinates 14 .
At this point it appears that Yablo has, so to speak, passed the problem on.
Even if we grant him the proportionality principle he needs input in the form of
determinable behavioral effects in order to plausibly ascribe causal status to
determinable mental cause-candidates. The question is whether there are determinable
behavioral effects. If there are coarse-grained determinable effects, then the
proportionality principle is arguably an interesting metaphysical principle. Do we
have independent reasons to believe in determinable effects? In the next section I
present an argument, and a couple of other independent reasons, for believing in
determinable effects 15 . I call the argument the Infection Argument, because it is
intended to show that the physical causal nexus gets infected with determinable
causes.
Before we get that far, I’ll briefly introduce what I take to be the main
alternative to Yablo’s view. There is a natural reply to Yablo when he claims that:
Inferring the causal irrelevance of, say, my dizziness, from the causal sufficiency
of its physical basis, is not appreciably better than rejecting the redness as
irrelevant on the ground that all the causal work is accomplished already by its
determinate scarlet. Or, if someone thinks it is better, then she owes us an
explanation of what the metaphysically important difference is between the
cases. [Yablo 1992, page 260]
14
As Yablo himself acknowledges, see for example the quote in section 2 of this paper.
In order to properly situate the argument of section 4: I there argue that some maximally determinate
effects have determinable causes, so I surely don’t deny that possibility. However, in the case of
mental causation, the primary effects are behavioral effects. In order to make it plausible that
behavioral effects can be determinable to an extent that will make Yablo’s argument go through, I
attempt to show in section 4 that the whole causal nexus gets infected with determinable causes. So I
don’t rely directly on cases where some mental phenomenon is causally proportional to some
determinate behavioral effect (for example a behavioral effect individuated in terms of its total
microstructure).
15
Proportionality and the Metaphysics of Causation
113
Why not think that my dizziness just is my being in some physical state? That for
something to be red on a certain occasion just is for it to be scarlet on that occasion?
Why not propose that, in general, the instance of a determinable property and the
instance of its determinate on a specific occasion are identical? I.e. that ‘P being
dizzy’ and ‘P being in the relevant physical state’ are two different descriptions that
pick out the same property instance on a specific occasion 16 . Why think that there is a
plurality of events/property instances up for grabs, all being candidates for causal
status?
Opposing Yablo, philosophers like Cynthia and Graham MacDonald, John
Heil and also Jaegwon Kim 17 hold that there is no such plurality of co-occurring
events [MacDonald & MacDonald 1986, Heil 2003, Kim 1998 & 2005]. Again,
consider one of Yablo’s exclamations.
(…) it would be incredible to treat Socrates’ drinking the poison as irrelevant to
his death, on the ground that his guzzling it was causally sufficient. [Yablo 1992,
page 272]
One natural response, and a response the above-mentioned philosophers would agree
with, is that Socrates’ drinking the poison and his guzzling of it just are the very same
event 18 . So the claim is that these two descriptions pick out the same event, even if
what the descriptions could have depicted differ 19 . For example, if Socrates’ actual
drinking of the poison were relevantly different, then it might have been the case that
‘Socrates drank the poison’ was true, while ‘Socrates guzzled the poison’ was false.
What positive reasons are there for believing, like Yablo, that there are two different
events here; events that in the actual world are co-occurring, and related by a
16
This would require that at least one of them designates non-rigidly.
Kim tends to hold this as a consequence of his supervenience argument, although he leaves more
pluralistic options as alternatives in his latest book [Kim 2005, chapter 2]. See the first paper of this
thesis for a discussion of Kim’s position.
18
The MacDonalds for example, say that: “No one would suppose, however, that an objects
exemplification of a colour, say, red, requires, first, that it be an instance of the property of being red,
and second, that it be a (distinct) instance of a second, related property, viz. that of being coloured. To
be an exemplification of the former just is, in this case, to be an exemplification of the latter, despite
the distinctness of the properties themselves.” [MacDonald and MacDonald 1986, page 149].
19
This relates to the issue of de re and de dicto modal claims, to which I have nothing new to
contribute. See e.g. [Fine, 2005] chapter I2 for a discussion.
17
Paper III
114
determination relation 20 ? In the next section I present one line of argument that
concludes with the existence of determinable effects, based on the assumption that the
proportionality principle is a sound metaphysical principle. If valid, this argument
strengthens Yablo’s position because it turns the assumption about event pluralism
into a consequence of the proportionality principle.
4. Where do Determinable Effects come from? The Infection
Argument
In this section I presuppose the validity of the proportionality principle, understood as
a metaphysical principle, and consider an argument for the existence of determinable
effects based on this assumption. The motivation for doing this is to get clear on
whether Yablo’s view can do without the additional assumption that there are
determinable effects. It would strengthen his view if it could be shown that the
existence of determinable effects follows from the proportionality principle itself.
Consider first the following line of reasoning, which points to the argument
that I call the Infection Argument. Suppose we have a causal chain leading from C1
via C2 to E.
Fig. 4a
C1
20
C2
E
One reason for thinking so is that causal relata are property instances, and that property instances are
partly individuated by the properties of which they are instances. Accordingly, wherever two different
properties are instantiated, there are two different instances. This reason, however, seemingly has no
bite against the token identity theorist just described. Nonetheless, it seems to me that the token
identity theorist will get either an idiosyncratic identity criterion for property instances, or he will have
to rule many properties out of existence.
Proportionality and the Metaphysics of Causation
115
E is a determinate effect. It might for example be the event of some object O having a
determinate acceleration. This determinate acceleration is caused by C2, the event of
some other object entering the gravitational field of O and thereby affecting O with a
certain force. Suppose the force had value 1 and direction Ψ. O is then caused to
accelerate in a determinate way by a force of value 1 with direction Ψ 21 .
However, if the object that entered the gravitational field of O had a slightly
different mass, and a correspondingly different spatial relation to O, it could give rise
to an identical force acting on O. The point is that it is required for E that there is an
object in O’s gravitational field that has some pair of mass and distance to O such that
O is affected by a force with value 1 and direction Ψ. It is not required that this object
has the exact location and the exact mass it actually has. In Yablo’s terminology that
event is more than enough and thus not required 22 .
That, however, is a determinable cause. Surely, that cause is itself a part of the
causal nexus, and has preceding causes. Consequently, it is also a determinable effect.
In this way, the causal nexus gets infected with determinable causes and effects. What
we need to get the ball rolling are cases where a maximally determinate effect is
caused by a determinable cause 23 . In general, this kind of argument has the following
steps:
21
The alert reader might question this claim on the background that the object in question has
conjunctive properties that determine even the precise acceleration. Call the specific acceleration ϕ and
then suppose that the object has some other property, for example a specific shape Ω. The conjunctive
property ϕ&Ω will then determine ϕ in the sense that (i) necessarily, for all x, if x has ϕ&Ω then x has
ϕ, and (ii) possibly, for some x, x has ϕ but lacks ϕ&Ω. This conforms to Yablo’s definition of
determination (Δ in section 2). If conjunctive properties can be determinates of their conjuncts in this
way, it will preclude the Infection Argument. The reason is that a maximally determinate of the effect
will be a conjunction of all the properties instantiated by the object that is involved in the effect-event.
I think the natural reply on Yablo’s and my part is to insist that the relevant locus of causal explanation
is not such a conjunctive determinate. Another way of avoiding this problem is to stipulate, like W.E.
Johnson originally did, that two determinates under the same determinable cannot be co-instantiated.
This would entail that conjunctive properties like ϕ&Ω and ϕ&λ cannot be determinates under the
same determinable, because they can be co-instantiated. However, this requirement has proved
problematic since it also rules out that determinates (in this case determinates of color) like being redlike and being yellow-like can be co-instantiated (by an orange object). Thanks to Anders Nes for
pointing out the complication regarding conjunctive properties in discussion.
22
Again, I reckon that many readers will suspect that this example conflates explanations and
metaphysics. I’m aware of that worry, but the present discussion works on the assumptions that the
proportionality principle is an interesting metaphysical principle and that the existence of determinable
causal relata is up for grabs.
23
To get the argument going we must assume that the existence of determinable cause candidates is up
for grabs. Someone who’s convinced of their non-existence at the outset could, strictly speaking,
Paper III
116
The Infection Argument
1. Assume that the proportionality principle is a metaphysical principle.
2. Observe that some maximally determinate effects are proportional to
determinable causes.
3. Infer from (1) and (2) that some maximally determinate effects have
determinable causes.
4. Invoke the premise that all causal relata have antecedent causes.
5. Conclude that there are determinable effects.
6. Reapply the proportionality principle.
The point of step (6) is that such a reapplication of the proportionality principle will
lead to effects that are more determinable than the ones you get in a one-step
argument from a determinate cause. The infection argument therefore serves as a
plausibility argument for the claim that there are determinable behavioral effects that
are proportional to mental causes.
The crucial step is (2). The earlier example following fig.4a was intended to
back up that step. Here is another example intended to further back up the claim that a
determinate effect might have a determinable cause. In this kind of example,
however, the difference between the different determinables is purely with regard to
the identity of their constituents.
Suppose a ball smashes a window, and that the window’s smashing is
maximally determinate in the sense that any minor change in the microphysical
details of this effect would result in a different event. Suppose further that the ball is
accept the proportionality principle and argue that the maximally determinate cause is proportional;
since it is the only cause-candidate around. This strategy is available since the proportionality principle
adheres to the notion of ‘screening off’ as defined in section 2. Notice, however, that even on such a
view the proportionality principle is not entirely empty. In footnote 21 I briefly discussed conjunctive
properties as determinates of their conjuncts. This is in accordance with Yablo’s definition of
determination, and it also allows for a restricted application of the proportionality principle.
Reasonably, on the kind of view presently discussed, the conjuncts will be genuine properties in
addition to the conjunctive determinates themselves. At least, this claim would be in accordance with
the standard &-elimination rule, i.e. that we can infer from the conjunctive property being instantiated
to the conjuncts being instantiated. The proportionality principle could then be used to decide whether
a conjunct or some conjunctive property of which it is a conjunct is the proper cause of the effect in
question.
Proportionality and the Metaphysics of Causation
117
constituted by a set of qualitatively identical molecules {m1,…,mn} arranged in a
specific manner SA. Then any rearrangement of the molecules that preserves the
structure of SA will result in an object qualitatively identical to the original ball. We
now have several different cause-candidates available: events involving the specific
realization of the ball, and more modally robust events that would survive different
degrees of this kind of rearrangement of the ball’s constituents. Let us look at two
different cause candidates. I am thinking here of an event as a triple of object,
property and time. Property DR is the property of having the determinate
microstructure of the actual ball, while property MR is the more modally robust
property of having a microstructure that is insensitive to the identity of two of the
constituents. This means that one could switch two parts of the ball without affecting
the latter event.
Surely then, however determinate the effect might be, the event involving MR
will be enough for the effect if DR is enough for the effect 24 . Therefore, in this case
the determinable cause-candidate is not screened off by its determinate sibling. This
kind of example is stronger in the sense that determinates that differ from their
determinables only in regard to how modally robust they are when it comes to the
identity of their parts, surely will be enough for any effect for which their specific
determinates are enough. On the other hand, this kind of example is weaker in the
sense that it can only establish the existence of determinable causes that are
determinable in this weak sense.
24
I’m assuming that we don’t individuate effects in terms of what specific causes actually caused
them. If we did, the present discussion would be totally off the point.
Paper III
118
5. The Proportionality Principle: An Explanatory or
Metaphysical Constraint?
Another way of introducing determinable effects is by using the principle of the
indiscernibility of identicals 25 . The idea is that two events are identical only if they
share all properties. However, co-occurring events might fail to share modal
properties, and by that fact qualify as distinct events. Suppose, for example, that two
events H1 and H2 co-occur, but that H2 is more modally robust than H1. By more
modally robust I mean that H2 can survive more intrinsic alterations than H1. The idea
can be illustrated by using possible worlds. H2 is strictly more modally robust than H1
if in all the possible worlds (relative to the actual world) in which H1 occurs H2 also
occurs, and there are some possible worlds in which H2 occurs in which H1 does not
occur.
Here’s an example. The event of some object being red is strictly more
modally robust than the event of the same object being scarlet because the range of
possible worlds (with respect to this object’s color) where the object is red properly
includes the range of possible worlds (with respect to this object’s color) in which the
object is scarlet 26 . Another example would be the relation between the specific
neurophysiological realizer NPS and the belief-desire state BDP in our example.
If we accept such phenomena, i.e. co-occurring events that differ only in
modal respects, the plausible understanding of a non-trivial proportionality principle
is as a metaphysical principle. After all, causation is a modal notion, and it surely has
something to do with counterfactual dependence, even though a reductive
counterfactual analysis has proved problematic 27 . Consequently, in the search for a
cause that is enough, but not more than enough, among such co-occurring events the
proportionality principle is a natural guideline.
25
I.e. that if A and B are identical then they are not discernable in any respect. Whether discernibility
in modal respects counts is admittedly a topic of dispute.
26
The restriction to possible worlds with respect to this object’s color is necessary because there are
possible worlds that are distant in other respects across which the object has the same specific color.
27
See for example [Collins, Paul & Hall] for an up to date discussion.
Proportionality and the Metaphysics of Causation
119
The usefulness of Yablo’s account of mental causation stands and falls with
the existence of determinable causal relata. This is not surprising. If we think that
mental phenomena are determinables that have physical determinates, and we don’t
accept determinable phenomena in our ontology, then mental phenomena are not
included in our ontology. Undeniably, for such a philosopher, the metaphysical
mental causation debate should appear irrelevant anyway; why search for the causal
efficacy of something that just doesn’t exist…?
I have pointed out that the application of the proportionality principle depends
on how the relevant effects are individuated. I also argued for the existence of
determinable coarse-grained effects based on a metaphysical understanding of the
proportionality principle. This, in combination with Yablo’s own arguments, back up
the following two conditional claims:
(1) If there are determinable causal relata, then Yablo’s proportionality
principle is a plausible metaphysical principle of causation.
(2) If Yablo’s proportionality principle is a valid metaphysical principle, then
there are determinable causal relata.
Accepting this, the alternative to a Yablo-style view will be a view that denies both
the proportionality principle as a metaphysical principle, and the existence of
determinable effects. The kind of view I have in mind says that instances of
determinable properties are identical to instances of their determinates, and that
something like the proportionality principle is, at best, only a constraint on causal
explanations 28 . Such a view can indeed preserve many of our intuitions, at least if it
incorporates the view that mental property designators designate non-rigidly. I.e. that
they can pick out different physical determinates at different occasions of use.
The remaining task, then, is to evaluate and compare the virtues and benefits
of these opposing views. Unfortunately, this goes beyond what I can hope to settle
here, where I will limit myself to discussing an apparent conflict between the tokenidentity view and the view that causal relations are accompanied by relations of
28
Alternatively that it is a trivial, or uninformative, metaphysical principle.
Paper III
120
counterfactual dependence 29 . If the reasoning behind the Infection Argument, and
more precisely the idea that some maximally determinate effects don’t depend
counterfactually on determinate causes, is sound, then, on the token-identity view, we
will get a new kind of counterexample to the general claim that causal relations are
accompanied by relations of counterfactual dependence. Let me elaborate.
6. Prospects for the Alternative Token-Identity View
Troublesome counterexamples to the counterfactual analysis of causation have been
on the table for a long time. Preemption and overdetermination cases are the standard
ones. The counterexamples discussed here, however, seem to backfire, not on the
counterfactual dependence aspect of causation, but on the extreme determinacy of the
causal relata. At least, the identity theorist owes us a story about how he can
distinguish between genuine causal relations without counterfactual dependence and
standard cases of spurious causal relations. The challenge is to do this without
ineliminably referring to determinable causal relata. What options are available?
Let’s have a look at a standard case of a spurious causal relation. E and F are
both effects of C, F occurs before E, but F is not a cause of E. The dotted line
represents a spurious causal relation.
Fig. 5a
F
C
E
If E depends counterfactually on C, but not on F, we have a nice explanation of why
C is a cause of E while F is not a cause of E. However, if E does not depend
counterfactually on C, because C is too fine-grained, then this explanation will not be
29
This discussion also adds to the discussion of Kim’s position in paper I.
Proportionality and the Metaphysics of Causation
121
available. So how can our token-identity theorist distinguish between genuine and
spurious causal relations?
She might hold that C is not so modally fragile, or determinate, as I’m
supposing. Like Quine or Davidson 30 , for example, she might hold that token events
are individuated by spatiotemporal location, and thus that events could survive
intrinsic changes as long as the spatiotemporal location was held constant. Causal
relata thus understood, however, are arguably too modally robust, opening for
scenarios where some event occurs at the same spatiotemporal location, and therefore
is identical to the original event, but is intrinsically different in a way that makes it
not cause E. On this view causes will not be sufficient in the circumstances for their
effects. That seems intolerable.
The token-identity theorist might also suggest that C has a modal robustness
proportional to E. Granting that, one can invoke the standard explanation that E
depends counterfactually on C but not on F. However, this is a critically unstable
position. Why think that the unique event occurring at a certain spatiotemporal
position has a modal robustness proportional to some particular effect? If we look at
other effects of C, it seems extremely likely that the different effects will require
different degrees of modal robustness, and thus that the claim that there is only one
event occurring is undermined.
I think the best approach is to hold that causal relata must be mediated by
causal mechanisms and that the existence of such mediating mechanisms is what
distinguishes between genuine and spurious causal relations. This appears to solve
the problem in so far as there actually are such mediating mechanisms. In standard
macro-causal relations there typically will be, but it seems to be an open question
whether such mechanisms bottom out when we let the time-intervals between their
elements approach zero. If they don’t bottom out, all causal relations will be
mediated by mechanisms, and the response works.
If they bottom out however, the token identity theorist needs to give an
account of the distinction between genuine and spurious causal relations at this
30
See [Quine 1985] and [Davidson 1985] for a discussion of the identity criterion for events.
Paper III
122
fundamental level 31 . Doing so in terms of counterfactual dependence seems difficult
as long as the extreme determinacy of the relata creates divergences between the
causal relations and the relations of counterfactual dependence.
One alternative might be to hold that the elements in these fundamental
mechanisms are picked out by fundamental act-terms in our best theory 32 . By doing
so, one could explain the difference between genuine and spurious relations at the
fundamental level by pointing out which act-terms figure in the best (or final) theory.
Such a view does not have to be committed on whether these acts can be given a
common analysis in terms of, for example, counterfactual dependence. An approach
along these lines seems viable. But there are problems to it.
First, it seems likely that act-terms of this type will be dispositional, and as
such partly individuated in terms of their effects. If so, the analysis seems to require
an independent account of causation. Then the previous difficulty re-occurs; how do
this without relying on the idea that effects depend counterfactually on their causes?
Second, it is a challenge to analyze macro causes this way, since complex
causes will not typically have designators that are fundamental within one’s theory. I
don’t have an argument directly against such an analysis, but as long as such an
analysis is lacking I think that the pluralist has the upper hand. The reason for this
suspicion is that most higher-level causal relata, as ordinarily conceived, are not
individuated in terms of their fundamental constituents, and it seems likely that it is
acts involving these fundamental constituents that are the ones picked out in such a
developed theory.
Finally, the attractiveness of such a position depends on our choice of
metaphysical background picture; a choice which should also be guided by a range of
other concerns. What I have in mind are general metaphysical issues such as
modality, personal identity, vagueness etc. Though unsettled, this discussion at least
shows that crucial decision points in the mental causation debate depend on topics
seemingly independent of this specific debate.
31
‘Fundamental level’, as used in this context, means fundamental in the sense that we’re talking about
the smallest temporal parts of a causal chain. It is not fundamental in the sense that the mechanisms
involve micro-phenomena while the mediated causal relation relates macro-phenomena.
32
Thanks to Øistein Galaaen for pushing the idea about fundamental act-terms in discussion.
Proportionality and the Metaphysics of Causation
123
The choices, as I’ve argued, are between higher-level and mental causation in
a pluralistic world, and a reductive understanding of mental causation within a
metaphysically sparse position acknowledging only maximally determinate
phenomena. This sparse position will get counterfactual dependencies between
macro-causal relata that diverge substantially from our common understanding.
However, there are candidate analyses on which this problem can be handled. These
views, however, should be judged on their merits also outside this particular
discussion. Such an evaluation has not been given here.
This is how the issue looks from a purely metaphysical point of view.
Adopting the pluralistic view, as I suggest, some interesting tasks in the wake of this
discussion are to figure out how much higher-level causation there is, and whether,
pace Yablo, mental phenomena really can be accommodated within his picture. The
first task I take to be a mainly empirical task, while the second calls for further
philosophical scrutiny.
7. Conclusion
I have argued that Yablo’s account of mental causation, which relies on the
proportionality principle and the claim that mental cause-candidates are more
proportional to behavioral effects than the competing physical cause-candidates,
works within a metaphysical picture that acknowledges co-occurring causal relata that
differ in modal robustness. In order to account for mental causation, the account
requires that the relevant effects have a modal robustness such that they depend
counterfactually on the mental cause-candidate rather than on the physical
determiners of the mental cause candidate. The Infection Argument provided reason
to think that determinable effects are indeed real occurrents, and that they are
legitimate objects of explanation. Still, this might not convince someone who doesn’t
share the background metaphysical view they rely on. I pointed out such an
alternative view. My arguments have not been conclusive. In the end, therefore, when
124
Paper III
choosing among these alternatives one should also keep track of their score on more
general metaphysical issues.
REFERENCES
Armstrong, David [1978] Universals and Scientific Realism Volume II: A Theory of
Universals, Cambridge University Press.
Bechtel, Bill & Jennifer Mundale [1999] “Multiple Realizability Revisited: Linking
Cognitive and Neural States” Philosophy of Science, Vol.66, pp. 175–207.
Collins, John, Ned Hall and L.A. Paul [2004] Causation and Counterfactuals MIT Press.
Davidson, Donald [1985] “Reply to Quine on Events” in Actions and Events: Perspectives
on the Philosophy of Donald Davidson, edited by E. Lepore and B. McLaughlin,
Basil Blackwell.
Fine, Kit [2005] Modality and Tense Clarendon Press, Oxford.
Heil, John [2003] From an Ontological Point of View, Clarendon Press, Oxford.
Johnson, W.E. [1921] Logic Part 1, Cambridge University Press.
Kim, Jaegwon [1998] Mind in a Physical World MIT Press.
___
[2005] Physicalism, or Something near Enough Princeton University Press.
MacDonald, Cynthia and Graham MacDonald [1986] “Mental Causes and Explanation
of Action” in The Philosophical Quarterly, Vol.36, No.143, Special Issue: Mind,
Causation and Action, April 1986, pp. 145–158.
Mackie, J.L. [1974] The Cement of the Universe: A Study of Causation Clarendon Press.
Quine, W.V.O. [1985] “Events and Reification” in Actions and Events: Perspectives on the
Philosophy of Donald Davidson, edited by E. Lepore and B. McLaughlin, Basil
Blackwell.
Yablo, Stephen [1992] “Mental Causation” The Philosophical Review, Vol.101, No.2, April
1992, pp. 245–280.
___
[1997] “Wide Causation” in NOÛS Vol.31, Supplement: Philosophical Perspectives,
11, Mind, Causation, and World, 1997, pp. 251–281.
PAPER IV
Fleshing out the Workings of
Realizable Properties℘
Anders Strand
ABSTRACT
In this paper I spell out a view on which the causal efficacy of non-reducible but physically
realizable mental and special science properties respects central physicalistic commitments.
These commitments are (i) the causal self-sufficiency of the physical domain, and (ii) the
rejection of unacceptable causal overdetermination. In reply to the so-called causal exclusion
argument, non-reductive accounts of mental causation typically rely on causation involving
an element of counterfactual dependence. However, there is a crucial aspect of the
exclusionist line of argument that is not answered by this kind of reply, and this often
manifests itself in claims like: there is no causal work to do for mental properties, or mental
properties can’t merely overdetermine their effects. I attempt to distill this aspect in an
argument called the Nomological Determination Argument. The main difference between it
and the Causal Exclusion argument is that it is not answered by the standard counterfactual
dependence based anti-exclusionist reply. Following this, the paper examines a response to
the Nomological Determination Argument. I reason in three steps: (1) I argue that a
metaphysical understanding of realizable second-order properties as properties generated or
constituted by quantification over first-order properties does not explain how second-order
properties can be efficacious in the presence of their first-order realizers. (2) I suggest a
mereological understanding of the metaphysical relation between realizable properties and
their realizers. (3) I show that this relation explains how the workings of physically realizable
properties are compatible with the physicalist commitments stated above.
1
2
3
4
5
6
7
8
9
℘
Introduction
The Nomological Determination Argument
Second-Order Properties and their Causal Standing
Type-theory, Orders and Nominal Definitions
A Mereological Account of Property Realization
Responding to the Exclusion Arguments
Causal Powers and Hume’s Principle
Further Considerations on Realization and Causation
Conclusion
Thanks to Lars Reinholdtsen, Øystein Linnebo, Carsten Hansen and Anders Nes.
Paper IV
128
1. Introduction
Non-reductionists about mentality have faced a forceful line of reasoning from the
proponents of so-called exclusion arguments. I call such proponents exclusionists.
The discussion is standardly carried out in terms of causal exclusion, the exclusionist
typically arguing that mental phenomena are causally redundant because all
behavioral effects have physical causes that fully explain their occurrence. The nonreductionist typically responds by pointing out that causation involves requiredness,
i.e., that causes in general are required for their effects. This is often coined in terms
of the effect depending counterfactually on the cause. The idea is that counterfactual
dependence is a hallmark of causation. The response says that behavioral effects
typically depend counterfactually on their mental cause candidates rather than on the
physical realizers of these mental cause candidates 1 .
I will not go into the details of this dispute here. Suffice it to note that the
disagreements on this issue between exclusionists and non-reductionists tend to
culminate in disagreements about the nature of causation. Causation is a topic that is
still lively debated, so when culminating on this issue the dispute tends to remain
unresolved 2 .
However, a crucial aspect of the worry voiced by the causal exclusion
argument can be stated in terms of a Nomological Determination Argument. Doing so
renders the argument immune from lack of clarity concerning the nature of causation.
Responding to this reformulated argument will therefore require a different approach.
Carving out space for such a response – and formulating one version of it – is the
main purpose of this paper.
1
Examples of this kind of response are [Yablo 1992], [Williamson 1998], [Loewer 2001], and
[Bennett 2003].
2
In particular there are troublesome counterexamples to the counterfactual analysis of causation, like
preemption, overdetermination and trumping cases. See e.g. [Collins, Hall, and Paul 2004] for up to
date discussions.
Fleshing out the Workings of Realizable Properties
129
2. The Nomological Determination Argument
Causal exclusion arguments standardly apply the principle of the causal closure of
physics as a premise. This principle says that all physical effects that have a sufficient
cause at a time have a sufficient physical cause at that time 3 . This opens for the kind
of counterfactualist response mentioned in the introduction, and which is elaborated
in more detail in the main introduction to this thesis and also in paper II. However, as
from the exclusionist’s point of view the counterfactual dependence based response
doesn’t get to the heart of the matter. I propose formulating a nomological
determination argument which instead of focusing on the causal closure, or causal
self-sufficiency, of the physical domain, focuses on its self-determination 4 .
Physical Determination: All physical phenomena are determined by prior
physical phenomena and the laws of nature.
Accepting this claim is to accept physical determinism, which is a strong and
controversial claim. However, the argument runs just as smoothly if we replace
Physical Determination with Physical Probability:
Physical Probability: The probabilities of all physical phenomena are
determined by prior physical phenomena and the laws of nature.
This latter claim reasonably gains much wider acceptance, and will get enough
philosophers and scientists onboard for the argument to have wide interest. This
should be kept in mind, because I’ll allow myself to phrase the discussion in terms of
3
See the second paper of this thesis for a detailed discussion of the causal closure (or causal selfsufficiency) principle, and its role in the causal exclusion argument.
4
For the record, one might hold that mental phenomena are causally relevant while irrelevant for the
nomological determination of physical phenomena. I aim, however, to establish a stronger position in
this paper. It should also be noted that this kind of self-determination, or completeness, principle has
been used in exclusion arguments earlier. See for example Papineau’s discussion of the “Causal
Argument for Physicalism” in [Papineau 2001, pages 9–13] where he discusses a completeness
principle saying “All physical effects are fully determined by law by prior physical occurrences.”
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Physical Determination for expository reasons. Before presenting the argument, I’ll
make a few conceptual clarifications.
By ‘physical’ I mean microphysical phenomena and natural phenomena that
are wholly individuated in terms of their microphysical constituents. This includes
elementary particles, their properties, and the relations between them. It also includes
macro-objects in so far as these macro-objects have microphysical constituents as
their smallest parts, and have all their microphysical constituents essentially 5 . For
illustration, imagine a familiar macro-object like a table. A table has a certain microstructure at a certain time, which is a certain constellation of a set {SA} of atoms.
Assume that this constellation has all its parts essentially. This specific constellation
of {SA} will then count as physical on the present understanding. If you think the
table is identical to this specific constellation of {SA}, then the table will also count
as physical. If you think the table only is realized by, or perhaps supervenient on, this
specific constellation the table will not be physical in this narrow sense.
The level talk I engage in is not to be understood mereologically in the sense
found in for example Oppenheim and Putnam [Oppenheim and Putnam, 1958]. If
understood mereologically it seems straightforward how higher-level objects can be
causally relevant even if micro-physics is causally closed; they are causally relevant
in virtue of having causally efficacious micro-physical parts. The question of the
causal relevance and/or efficacy of higher-level properties might still prove
problematic, though the account of property realization I give later in this paper will
shed important light on that issue. Eschewing this mereological conception of levels
for now, the present talk of levels is to be understood in terms of a realization
relation. For illustration, suppose you deny the table is identical to the specific
constellation of {SA}. Then the table will be at a higher-level than the specific
5
Entities that are functionally individuated, and which have contingent parts, will not count as physical
in this narrow sense. The motivation for operating with such a narrow understanding is that the
physical domain understood in this way is the best candidate for a self-determined domain. If we
include entities that have microphysical parts contingently, there might not be anything in the physical
domain that determines whether such an object retains its identity through changes of its parts.
Accordingly, a domain that includes such entities might not be totally self-determined.
Fleshing out the Workings of Realizable Properties
131
constellation of {SA}. What is more, the table will be so in virtue of being realized by
that specific constellation 6 .
A final clarification: it is an assumption of the later discussion that causal
relata are something like property instances. For example, causal relata are not bare
objects, but objects having certain features. This is a common assumption in the
debate, and I take it onboard here without further questioning 7 .
The Nomological Determination Argument goes like this:
The Nomological Determination Argument
(i)
Mental phenomena in particular and higher-level phenomena in
general are not identical to physical phenomena.
(ii)
Physical Determination: all physical phenomena are fully
determined by prior physical phenomena and the laws of nature.
(iii)
Mental and other higher-level phenomena do not merely
overdetermine physical phenomena.
(iv)
From (i) - (iii): mental and other higher-level phenomena are irrelevant
for the determination of physical phenomena.
As I argue later in this paper, this argument is flawed. However, establishing a
position from which to reveal the details of the flaw will bring us through discussions
of properties and their designators, and specifically of the metaphysical nature of the
realization relation among properties. As I will argue, the way to respond to the
Nomological Determination Argument is to show that the relation between mental
and other realizable higher-level phenomena on the one hand and physical
6
In general, I hold that object A realizes object B if and only if A and B share all proper parts and B is
strictly more modally robust than A with respect to their parts. B is strictly more modally robust than A
with respect to their parts if and only if for all parts, if it essential to B then it is essential to A and there
are parts that are contingent to B but essential to A. The account of realization presented later in this
paper does not concern objects, but properties and property instances.
7
I discuss this assumption in section 11 of the introduction to this thesis.
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phenomena on the other hand is tight enough to ensure and explain the relevance of
the realizable phenomena 8 .
I approach this task by first focusing on property realization as it is sometimes
cashed out in terms of the order hierarchy between properties. On this view secondorder properties are realized by first-order properties, and second-order properties are
generated by quantification over first-order properties. I point out that understanding
the metaphysical relation between first and second-order properties in analogy with
the order relations between their designators lends plausibility to the exclusion
argument. I then argue that this analogy is mistaken, and that getting to the
metaphysical nature of the realization relation requires another account. Finally I
argue that a slightly revised version of Sydney Shoemaker’s metaphysical account of
property realization disarms the Nomological Determination Argument.
3. Second-order Properties and their Causal Standing
In general, a property is of second order if and only if it is (partly) defined by
quantification over first-order properties. One example is functional properties
defined by quantification over structural properties. Object O has functional property
P if and only if it has some structural property S that plays a certain causal role. In my
view, and as I argue later in this section, this order hierarchy applies to propertydesignators and not to properties themselves 9 .
However, some of the proponents in the mental causation debate seem to have
an understanding of the metaphysical realization relation that is based on this order-
8
There are certain other ways to block the argument. Note that I speak of phenomena throughout the
argument. This is done in order to get maximal generality, but at the same time it blurs the type-token
distinction. One could hold that mental properties are distinct from physical properties while mental
tokens (e.g. events) are identical to physical events, as is argued by for example Davidson [Davidson
1980] and the MacDonalds [MacDonald and MacDonald 1986]. This would enable one to argue that
premise (i) concerns types (properties), while premise (ii) concerns tokens (events), and thus that the
argument equivocates. I allow myself to put this remark in a footnote since I hold that the relevant
tokens are individuated partly in terms of the types they are tokens of. In other words; I hold that token
identity requires type identity. This alternative response to the argument is thereby blocked.
9
I’m assuming a realist understanding of properties throughout this discussion.
Fleshing out the Workings of Realizable Properties
133
hierarchy. Here are a couple of examples. Kim, for example, talks about second-order
properties being generated by quantification over other properties:
Second-order properties therefore are second-order in that they are generated by
quantification – existential quantification in the present case – over the base
properties. [Kim 1998, page 20]
Ned Block talks about second-order properties being constituted by quantification
over other properties:
What it is for a property to be second order is naturally defined long the following
lines: a second order property is a property that is constituted by having some other
properties – first order properties – that bear a certain relation to one another. First
order properties are not so constituted, so the very idea of a second order property
being identical to a first order property is contradictory. [Block forthcoming, page
12]
In so far as this is meant to give an account of the metaphysical relation between, for
example, functional properties and their realizers it lends plausibility to the exclusion
worry. The reason for this is that this relation doesn’t explain how the second-order
properties are efficacious in the presence of their realizers. It seems to be the case that
the realizers themselves would be sufficient for the relevant effects independently of
the second-order property being instantiated.
Such a misbelief in the causal efficacy of second-order properties has proved
compelling 10 . Frank Jackson, for example, says the following:
Consider, to illustrate the point, a fragile glass that shatters on being dropped
because it is fragile, and not (say) because of some peculiarity in the way it was
dropped. Suppose that it is a certain kind of bonding B between the glass molecules
which is responsible for the glass being such that if dropped, it breaks. Then the
dispositional property of being fragile is the second-order property of having some
first-order property or other, bonding B as we are supposing, that is responsible for
the glass being such as to break when dropped. And the first-order property,
bonding B, is the categorical basis of the fragility. But then it is bonding B,
together with the dropping, that causes the breaking; there is nothing left for the
second-order property (second-order in the sense of being the property of having a
property), the disposition itself, to do. All the causal work is done by bonding B in
10
I’ll just talk about second-order properties in the following, because that’s standard in the debate.
Analogous reasoning would, however, apply also to properties of higher orders.
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concert with the dropping. To admit the fragility also as a cause of the breaking
would be to admit a curious, ontologically extravagant kind of overdetermination.
[Jackson 1998, pages 91-92]
The same worries about causal redundancy and extravagant overdetermination can be
found in Kim’s supervenience argument [Kim 1998, 2005]. A crucial premise in that
argument is the so-called exclusion principle:
Exclusion: No single event can have more than one sufficient cause occurring at
any given time – unless it is a genuine case of causal overdetermination. [Kim
2005, page 42]
The plausibility of a general denial of the causal efficacy of second-order properties
depends on how one understands the metaphysical relation between second-order
properties and their realizers. If the relation between realizable properties and their
realizers is such that it explains why the realizer is sufficient for the realized property,
and also how the realized property can be efficacious in the presence of its realizer,
we would have an answer to the exclusion argument as targeted against realizable
properties.
Before sketching an alternative understanding of the realization relation, I will
provide some further reasons to be skeptical to a metaphysical understanding of the
first-order second-order relation. I do this by a brief discussion of the order hierarchy
as it figures in ramified type theory. The main point of this discussion is that the order
of a property is relative to the conceptual scheme of its designator, and therefore not a
good guide to the metaphysical nature of the property and its relations to other
properties.
One way of framing the issue is to ask whether the definitions of second-order
properties are nominal definitions or real definitions. That is, are definitions that
involve quantification over lower-order properties definitions of property-designators
or of properties themselves? The use of terms like ‘generation’ and ‘constitution’
indicates that the authors quoted above intend to give real definitions of the properties
themselves and their metaphysical essence. On the other hand, as I emphasize in the
Fleshing out the Workings of Realizable Properties
135
next section, the order hierarchy as stated in ramified type theory is best understood
as a hierarchy of property-designators.
4. Type theory, Orders and Nominal Definitions
Type theory was introduced in order to avoid formal paradoxes like Russell’s
paradox. Type theory can be used to impose a level-hierarchy on properties that
places individuals at the bottom, first-level properties are properties of individuals,
second-level properties are properties of first-level properties, and so forth. This
structure blocks Russell’s paradox. In order to avoid semantic paradoxes, like the liar
paradox, one can introduce a ramified type theory. In such a framework there is an
order hierarchy for each type level. For example at type level 1 we have:
First-order
Predicates defined by quantification over individuals
alone.
Second-order
Predicates defined by quantification over individuals
and over the referents of first-order predicates.
Third-order
Predicates defined by quantification over individuals,
and over the referents of first and second-order
predicates.
.
.
.., and so on
This additional structure can be used to handle the liar paradox. Consider the
proposition stated by the sentence “This proposition is false.” Within a ramified typetheoretic framework this sentence is interpreted as saying: “There is a proposition of
order n, which this sentence states, and which is false.” This proposition is itself of
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order n + 1, and consequently there is no proposition of order n stated, and the
sentence is false. This is how the contradiction is resolved 11 .
The crucial point is that the order relations are conceptual relations between
the predicates in our theory, and there are restrictions on definitions that are
introduced in order to avoid paradoxes. Moreover, these conceptual relations do not
directly reflect the metaphysical nature of the relations between the properties picked
out by those predicates.
Here’s an illustration. Suppose we have a structure, a very simple world W,
inhabited by an object and a property instantiated by that object. The symbol ‘W’
denotes the world, ‘a’ denotes the object, ‘I’ denotes the instantiation relation
between the object and the property, and ‘F’ denotes the property. The dotted arrows
represent the relations of denotation.
Fig.4a.
W
a
I
F
Now we can introduce a new term G by definition:
G(x) ↔ ∀F (F(x))
The referent of ‘G’ is truly predicated of an individual if and only if any first-order
predicate is truly predicated of that individual. Since the semantic structure for this
theoretic language is so simple, it consists of W and its inhabitants, the only candidate
for the semantic value of G is the property already denoted by ‘F’. The metaphysical
11
To see how Russell himself resolves this and other paradoxes see [Russell 1908], especially pages
240–241. The liar paradox is a semantic paradox, in contrast to Russell’s paradox which is a formal
paradox.
Fleshing out the Workings of Realizable Properties
137
status of this property is of course not altered by the type theoretic definitional
relations between the terms ‘F’ and ‘G’. This example is very simple, and the point
therefore seems trivial, but we will later see its importance in more complex cases.
Actually, moving back and forth between first and second-order property
designators can be done, in general, by the following procedure. ‘P’ is a second-order
property-designator and Y is a variable over properties.
∀x (Px ↔ ∃Y(Yx & Y=P)
In this way we can generate second-order designators for properties that have a firstorder designator. However, it is hard to see how the existence of such a procedure
should affect the metaphysical nature of properties and the relations between them.
The reasonable conclusion is that the order-relations as defined in ramified
type theory are relations between property-designators, and that properties themselves
belong to the order hierarchy only in virtue of having designators of a certain order.
What order a property has is therefore relative to the conceptual scheme of its
designator 12 .
Let’s return to the main line of reasoning. I hope I have made a convincing
case for the claim that the order hierarchy among properties is relative to our
conceptual scheme, and that the metaphysical account of the realization relation
between properties is up for philosophical grabs. I now sketch such a metaphysical
account of property realization that can be shown to disarm both the Nomological
Determination Argument and the Causal Exclusion Argument 13 .
12
Gödel, in his “Russell’s Mathematical Logic” [Gödel 1951], distinguishes between a constructivist
conception of “notions” and a realist conception of “concepts,” and says “(…) any two different
definitions of the form α (x) = φ (x) can be assumed to define two different notions α in the
constructivist sense. For concepts, on the contrary, this is by no means the case, since the same thing
may be described in different ways.” [Gödel 1951 page 137] This is in analogy with the difference I’m
pointing out between property designators and properties. Thanks to Øystein Linnebo for bringing this
reference to my attention.
13
In so far as one accepts the standard requiredness/counterfactualist response to the causal exclusion
argument, the further points I make in response to the Nomological Determination Argument serve to
explain why the standard response works.
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5. A Mereological Account of Property Realization
I suggest a Shoemaker inspired theory of property realization 14 . Shoemaker’s view
was presented in a context where Shoemaker himself set out to explain a conflation
between lower and higher-order relations between predicates, and the metaphysical
realization relation between properties. He did this in order to reply to George
Bealer’s argument against functionalism [Bealer, 1997].
Shoemaker’s account of property realization says that
(…) property X realizes property Y just in case the conditional powers bestowed
by Y are a subset of the conditional powers bestowed by X (and X is not a
conjunctive property having Y as a conjunct). [Shoemaker 2003a, page 432]
According to Shoemaker a causal power is conditional if it can only be activated or
manifested if the object has certain other properties. One example is that a knife
shaped object has a causal power to cut wood conditionally upon being made of a
suitable material [Shoemaker 2003b, pages 212–213].
Shoemaker holds that properties are individuated by – but not identical to –
the sets of causal powers they bestow. Based on the realization relation just stated,
one can argue, as Shoemaker very briefly does [Shoemaker 2003a, page 433], that an
instance of a realizable property is the cause of a certain effect in the presence of its
realizer if the causal powers responsible for that effect belong to the causal powers
bestowed by the realized property, which is a subset of the causal powers bestowed
by the realizing property.
In this way there is no overdetermination in the sense of there being
overdetermining causal powers at play. However, there is overdetermination by
properties. Both the realized property and the realizer might qualify as sufficient
14
In presenting his view in “Realization and Mental Causation” [Shoemaker 2003] Shoemaker
acknowledges Michael Watkins for having pointed out the idea. Just a few days before submission of
this thesis (August 2007) I came to know that Shoemaker is publishing a new book on physical
realization [Shoemaker August 2007]. Not having access to this book, I’ve based my discussion mainly
on [Shoemaker 2003].
Fleshing out the Workings of Realizable Properties
139
causes for the given effect. This gives rise to a worry that the realizable properties
still are causally superfluous; why think that there corresponds a genuine property to
such a subset of the causal powers bestowed by another property?
There are promising answers to this question. In particular one might hold that
such subsets have associated properties only if they are related to certain kinds of
effects by law. Still, however, the overdetermination by properties remains. Whether
this represents a problem or not is up for discussion. It might be that this framework,
and the explanation of why the overdetermination occurs that it provides, is
satisfactory. However, I think it is worthwhile to consider whether an identification of
realizable properties with sums of causal powers is viable 15 . If it is, it would
effectively block the worry that realizable properties are causally excluded by the
causal powers that individuate them. Let us call this suggestion the restricted identity
claim.
If one accepts the restricted identity claim, the realization relation among
properties can be reformulated in mereological terms. The suggested view says that
the metaphysical realization relation between properties is a part–whole relation
among sums of causal powers.
Property Realization: Property P realizes property Q if and only if Q is a
part of P or Q is a part of the sum of causal powers bestowed by P. 16
This realization relation gives rise to an analogous realization relation for property
instantiations, which are the kind of entities that commonly are taken to be causal
relata. The view says that an instance of property P realizes an instance of property Q
if and only if property P realizes property Q.
15
When talking about the identification of properties with causal powers I prefer to talk about sums of
causal powers because sets are commonly understood to be abstract entities.
16
One might require Q to be a proper part of P, but since it seems harmless to allow that properties
realize themselves, I formulate the definition in terms of parthood. If the realizer itself is a realized
property then Q will be a part of P; if not, Q will be a part of the sum of causal powers bestowed by P.
The reason for not committing to a reductive analysis of properties in terms of sums of causal powers
is based on circularity worries, since there is ineliminable reference to properties in causal power
ascriptions.
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We get a more precise way of spelling out this latter relation if we identify
property instances with triples that have the instantiating object, the property and the
time of instantiation as constitutive parts. Property instances can then be represented
by [Object, Property, time].
Realization among Property Instances: Property instance [O, P, t] realizes
property instance [O*, Q, t’] if and only if O = O*, t = t’, and P realizes Q.
In the case where P is a realized property, Q will be a part of P if P realizes Q. In such
cases we can talk about qualitative parthood among property instances.
Qualitative Parthood among Property Instances: Property instance [O, P, t]
is a qualitative part of property instance [O*, Q, t’] if and only if O = O*, t =
t’, and P is part of Q.
Let’s put this account to work.
6. Responding to the Exclusion Arguments
In fleshing out how this mereological relation between realizable properties and their
realizers, and between their instances, disarms the Nomological Determination
Argument I’ll be talking in mereological terms. I shall also be using Venn diagrams
to illustrate parthood relations. Events are taken to be property instances.
Suppose that we are interested in the determiner at time t of an event E, and
that two events are candidates: Di, which is an instance of a realizable property D, and
Ri, which is an instance of a realizer property R. According to the mereological
Fleshing out the Workings of Realizable Properties
141
account of property realization, the relation between D and R is that the former is a
part of the latter 17 . Di is a qualitative part of Ri. For illustration, consider figure 6a:
Fig.6a.
Ri
Di
E
In figure 6a, the instantiation of R determines E (in the circumstances) if the
instantiation of D determines E (in the circumstances). So we have two non-identical
determiners, but in cases like this there is no competition. The mereological
realization relation explains why the overdetermination by properties is completely
acceptable in this kind of case. The causal powers responsible for the effect constitute
a sum. In this case D is identical to that sum, and the instantiation of R is sufficient
for E because it has this sum as a part 18 . Parts and wholes do not compete in this
game, much in the same way as objects related as part and whole don’t compete for
spatial locations.
The only competition is for the status of being a minimal determiner. Much in
the same way as the only spatial competition between proper parts of objects and the
objects themselves is for exact location. As illustration 6a shows, instances of
realizable properties can be minimal determiners compared to their realizers, in the
sense of their being proper parts of their realizers.
The only overdetermination that appears within this framework is the
overdetermination by a whole and its parts, i.e. by a sum of causal powers and a
bigger sum of causal powers. Since the bigger sums – the sums associated with the
17
If R is not itself a realizable property D will be a proper part of the sum of causal powers that
individuates R.
18
Again, in the case where R is not itself a realized property the sum of causal powers bestowed by R
has D as a part.
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fundamental realizers – qualify as sufficient causes in virtue of including the relevant
causal powers, there is no conflict with the principle of the self-determination of the
physical domain. The discussion of the principle of the causal self-sufficiency of
physics in paper II concluded that weak versions of that principle were compatible
with the causal efficacy of non-reducible mental properties. The present account
fleshes out this claim in more detail. Instances of physical properties are sufficient for
the determination of future physical events, but they are sometimes more than
sufficient. Sometimes physical events have minimal determiners that are instances of
higher-level realizable properties. This kind of response, therefore, pays respect both
to the idea that realizable causes don’t merely overdetermine their effects, and to the
principles of the causal closure and the self-determination of the physical domain.
In the last two sections of this paper, I (1) address the worry that instances of
causal powers are problematic cause-candidates since they are partly defined in terms
of their effects, and (2) discuss how the suggested view accounts for multiple
realization and scenarios where the same realizer realizes different properties.
7. Causal Powers and Hume’s Principle
What I here call Hume’s principle is the claim that causes and effects are contingently
related. There appears to be a conflict between Hume’s Principle and the idea that
causal powers are causes. This is so because causal power designators are
conceptually related to effect designators. Citing causal powers directly in causal
explanations can therefore be explanatorily problematic. In response to this worry I’ll
run an argument in the spirit of Davidson’s argument in “Actions, Reasons and
Causes” [Davidson 1980a].
In brief, Davidson’s argument says that even though reasons for an action are
seemingly logically related to the action, reasons can be causes of actions. The
observation is simple: reasons and actions themselves are not ipso facto logically
related even if their descriptions might be logically, or conceptually, related. In
Davidson’s words,
Fleshing out the Workings of Realizable Properties
143
The truth of a causal statement depends on what events are described; its status as
analytic or synthetic depends on how the events are described. [Davidson 1980,
page 14]
Suppose that A caused B and that we describe A as ‘the cause of B’, this does not
change the fact that A caused B. Rather, by describing A in this way we use a
description that renders the explanation uninformative. But uninformative truths are
still truths.
The same reasoning transfers to relations between property designators.
Causal powers are partially defined by reference to effects. Citing an instance of a
causal power as a cause will therefore typically result in an explanation where
explanans and explanandum are conceptually related. However, this conceptual
relation is contingent on the choice of description, and does not directly reflect the
metaphysical relation between the cause and effect. In particular it doesn’t reveal any
partially conceptual, or logical, component to the causal relation.
There is a tradeoff between citing realized properties and their realizers in
causal explanations. If one is interested in a cause that is required for the relevant
effect, this interest favors the realized property. On the other hand, citing the specific
realizer can be better if, for example, one is interested in understanding a specific
causal mechanism. A realizable property might have different realizers all of which
would lead to the same effect via different mechanisms. In such cases the realized
property instance would be the cause of this effect, but it will often be desirable to
know the details of the realizers and mechanisms. The crucial point is that the account
of property realization suggested here ensures the efficacy of the realized property in
the presence of the specific realizers.
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8. Further Considerations on Realization and Causation
The following Venn diagram illustrates and explains multiple realization:
Fig.8a
Property P1
constituted by a set
CP1 of causal powers
Property P2
constituted by a set
CP2 of causal powers
Functional mental
property M constituted
by a set CP3 of causal
powers
The diagram shows how multiple realization scenarios are accommodated within the
present account of realization. All the realizers of a realizable property have some
causal powers in common and those common powers constitute the realized property.
This simply reflects the idea behind multiple realization: the same causal role but
different intrinsic natures.
More important for my present concerns is, so to speak, the inverted
phenomenon. It consists in the very same realizer giving rise to different dispositions.
Because this kind of case helps illustrate the idea of minimal causes and determiners
put to use earlier, I want to spend some time discussing it in this section.
There appear to be scientifically important causal regularities that can only be
framed by reference to powers and dispositions. One example concerns the difference
in causal potentials between the electrical conductivity of copper and the opacity of
copper, both of which have the same realizer 19 . It is a virtue for an account of
realization if it can accommodate such cases. The opacity and electrical conductivity
of metals serves as an example for Frank Jackson.
19
To my knowledge this point was originally made by Peter Menzies [Menzies 1988].
Fleshing out the Workings of Realizable Properties
145
The basis for the different dispositional properties of opacity and conductivity is,
roughly, the way free electrons permeate the metal; nevertheless, an explanation
in terms of a metal’s opacity is clearly not the same as one in terms of its
conductivity. [Jackson 1998, page 92]
One advantage of the present view is that it easily explains the difference between
such explanations. The next Venn diagram shows such a multiple disposition
scenario:
Fig.8b
Set of causal powers
constituting property C
Set of causal powers
constituting disposition D1
Set of causal powers
constituting disposition D2
Here we have a set of causal powers that constitute a certain property. Two different
subsets of this set constitute two different dispositions. The two different explanations
refer to different dispositions, despite the very same realizer realizing both
dispositions 20 .
A denial of the causal efficacy of realizable properties, on the other hand,
leads to explanatory problems, as in the following example from Robert Van Gulick:
Consider a simple example involving non-mental properties. Imagine we are
preparing a chemical mixture TTT that becomes explosive when its molecular
configuration is altered by successive heating and cooling, call the relevant
configuration BAM. Imagine further that TTT turns blue when and only when it
goes into the BAM configuration. A match is dropped into the blue BAM TTT and
it explodes. Question: Was the blueness of the TTT into which the match was
dropped causally potent or epiphenomenal with respect to producing an explosion?
It seems clear that it was epiphenomenal. The TTT’s being blue and its
exploding were both causal consequences of its being BAM, but its exploding was
not a consequence of its being blue. [Van Gulick 1993, page 244]
20
See Peter Menzies’ paper “Against Causal Reductionism” [Menzies 1988] for a nice discussion of
such cases, and their relation to the issue of reducing higher-level causal relations to lower-level ones.
146
Paper IV
On the view developed here, we can account for this kind of case. Recall figure 8b.
Take blueness to be D1, explosiveness to be D2 and BAM to be C. One of the
assumptions of Van Gulick’s case is that blueness and BAM are perfectly correlated
for TTT, which results in the counterfactual dependencies coming out “wrong”.
However, we can distinguish between blueness and BAM here in virtue of what
causal powers are activated, and thus explain why the counterfactual dependencies
are as they are, and why they don’t track the causal relations in this special case.
Moreover, it seems confused to say, as van Gulick does, that the TTT being blue was
a causal consequence of its being BAM. On the view defended here the relation
between them isn’t causal; they are realized by the same realizer on this occasion.
9. Conclusion
I’ve presented a metaphysical account of realization that arguably answers both the
Nomological Determination Argument and the Causal Exclusion Argument. The
account involves identifying realizable properties with sums of causal powers. It is a
question worthy of closer examination whether the kind of account I’ve given here
works without making this restricted identity claim. The relation between properties
and the sets of causal powers that individuate them, on Shoemaker’s account, will
have to be of a nature that prohibits causal competition between realizable properties
and the sums of causal powers that individuate them. The account I give here assumes
that the restricted identity claim holds, but it might be possible to retreat to
Shoemaker’s original position. Nonetheless, the view spelled out here shows how a
metaphysical account of realization can be put to use in answering all aspects of the
exclusion problem.
Fleshing out the Workings of Realizable Properties
147
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