Do Causal Powers Drain Away?
Ned
Block
No one has contributed as much to our understanding
of the problems of mental causation in recent years as Jaegwon Kim. We non-reductive materialists must face up to
the serious difficulties he has raised for our position.[1]
In this note, I will discuss one
issue concerning the main argument of Mind in a Physical World (Kim,
1998), the Causal Exclusion Argument.
The issue is whether it is a consequence of the Causal Exclusion
Argument that all macro level causation (that is, causation above the level of
fundamental physics) is an illusion, with all of the apparent causal powers of
mental and other macro properties draining into the bottom level of
physics. I will argue that such a
consequence would give us reason to reject the Causal Exclusion Argument. But there is also a stronger challenge, the
charge that, if there is no bottom level of physics, the Causal Exclusion
Argument has the consequence that “causal powers would drain away into a bottomless
pit and there wouldn’t be any causation anywhere.” (81--page numbers
that are not attributed to other works are to Kim, 1998)
The Causal Exclusion Argument
To begin, I will describe what I
take the Causal Exclusion Argument to be.
When one event causes another, some properties are causally efficacious
and others are not. If the singer breaks
the glass (Dretske, 1988, p. 79) by shrieking “Peace and quiet”, we may suppose
that the intensity and frequency of the sound are causally efficacious but not
its meaning. And we may suppose that the
causation depends on the thickness and tensile strength of the glass, but not
the place of its manufacture or the name of its owner. If the cause causes in virtue of its property
F and the effect is caused in virtue of property F* of the effect, we can
represent this as
FÞF*
Let the (putatively) causally relevant properties in the a case of one mental event token causing another be mental properties M and M*. That is, MÞM*. (This is a premise in a reductio.) Let physical property P be the supervenience base of M and physical property P* the supervenience base of M*. Then (Kim assumes and I concur) PÞP*. (We could assume Davidsonian events, in which case it is a single event e that has both properties M and P, and a different single event e* that has both M* and P*. We could equally suppose that the event that has property M is distinct from the event that has property P. I won’t presuppose either scheme. I will follow Kim in framing the discussion in terms of an instance of one property causing an instance of another, e.g. an instance of F causes an instance of F*. The intended meaning is that an instance of F causes an instance of F* in virtue of the former having F and the latter having F*. I will usually leave out the phrase ‘instance of’ where the sense is obvious, saying just that F causes F*.) We could diagram the situation as follows:
MÞM* PÞ P*
Double
arrows indicate causation, single arrows indicate supervenience. (An
instance of) mental property M causes (an instance of) mental property
M*, physical property P causes
physical property P*, M supervenes on P and M* supervenes on P*. The MÞM* causal relation is
putative—it is a premise in a reductio that Kim will reject.
Figure 1
Kim’s argument begins by alleging a tension in our
thinking about how (the instance of) M* comes to be. It is (putatively) caused by (the instance
of) M and determined by P*. How can
these both be true? Kim says that there
is a problem because M and P* can each be used to offer complete and
independent explanations of M*. Of
course, the non-reductive materialist who accepts causation at many levels
should not recognize any tension. The
non-reductive materialist thinks that every property above the level of basic
physics has “horizontal” causal relations (at the same level) and vertical
determination (from a lower level). And
these explanations are not completely independent, since the property that M
supervenes on (viz. P) is the property that produces P*. In any case, Kim does not rest anything on
this alleged tension. It is a way-station
that he uses to justify the claim that M can only cause M* by causing P*, a
claim that I will not question. Thus we
have the situation diagrammed in Figure 2:
M
(putatively) causes M*, P causes P*, M supervenes on P, M* supervenes on
P*, and—here is the new feature—M (putatively) causes P*
Figure 2
Now we have a more plausibly problematic tension: we have two different causally sufficient properties competing for the causation of P*, namely M and P. The crux of the Causal Exclusion Argument is Kim’s claim that P pre-empts M. To use a metaphor that Kim uses in a slightly different context,[2] P does all the causal work, so there is nothing left over for M to do. Mental causation, Kim says, is threatened. But why does the causal work done by P exclude that done by M? Perhaps the thought would be that if there is a sufficient physical cause and a sufficient mental cause, then each does 100% of the work, and so more work is being done than there is to do. But if causation derives from causal law and if there are causal laws at different levels that specify sufficient causes, then we cannot “add up” work in this way.
(Famously, not all laws are causal laws. For example, the Wiedemann-Franz Law is a correlational law: electrical and thermal conductivity are correlated but changes in one do not cause changes in the other. But some laws are causal laws. Those are the ones that underwrite causal efficacy of properties on one way of thinking about causation that I will appeal to. I will not attempt to say what distinguishes the causal from the non-causal laws.)
Let us call the principle that sufficient causation at one level excludes sufficient causation at another level the Exclusion Principle. The rest of this paper is a critique of the Exclusion Principle.
Overdetermination
Kim entertains the
“overdetermination” view, that M and P are both sufficient causes. He says, “…consider a world in which the
physical cause does not occur and which in other respects is as much like our
world as possible. The overdetermination
approach says that in such a world, the mental cause causes a physical
event—namely that the principle of causal closure of the physical domain does
not hold.” (45) He adds,
uncontroversially, that the failure of causal closure is not an acceptable
conclusion.
Problem
1: Kim supposes that on the overdetermination view, a world in which the
physical cause does not occur and which in other respects is as much like our
world as possible is a world in which the mental cause does nonetheless occur.
Though I cannot go into the matter here, some supervenience doctrines but not
others will preclude such a world. I
don’t see a way of choosing among these supervenience doctrines. (See
McLaughlin, 1997.) If there is no fact of the matter as to which of these
supervenience doctrines holds, there is no fact of the matter of whether the
closest non-P world contains the instance of M.
Problem
2: Going along with Kim’s assumption that (assuming overdetermination) the
closest non-P world is one that nonetheless contains the instance of M, why
should we suppose that the closest world in which the instance of P does not exist
is a world in which causal closure no longer holds? Cain slew Abel by strangling him--let us
suppose. This causal sequence was
implemented by molecular trajectories, including the molecules of all or parts
of Cain and Abel. Cain and Abel might
have had a merely micro-physically different diet for the previous ten
years--that is, a diet of food that was not different from their actual food in
a way that anyone could notice, but merely consisted of different tokens
composed of different molecules—the same types of carbohydrates and proteins
but different tokens of those types.
Molecules in the food we eat and air we breathe are constantly replacing
the molecules in a human body. If Cain
and Abel had eaten these different token molecules for ten years, they would
have been composed mainly of different molecules. If Cain and Abel had eaten these different
token molecules, the strangling would have occurred just the same, but the
molecules involved would have been different.
Further, the strangling would have caused the death even if the
molecular realizations had been different, so long as the difference wasn’t
significant at the macro level. So a
world in which the molecular implementer of an event (token), e, does not exist
can be a world in which e exists but is implemented differently. Kim says “we may assume, without prejudice,
that no alternative physical base…would have been available on this
occasion.” (43) But although there are worlds in which there
is no alternative physical base, Kim owes us a reason for thinking the world in
which there is no alternative physical base (in which causal closure fails) is
closer than one in which it doesn’t fail but M is implemented differently (or M
doesn’t exist at all).
I said that the strangling would have occurred just
the same even if its perpetrator and victim had been composed of different
molecules. On second thought, I am not
sure whether that particular strangling would have occurred. I don’t claim to know how to identify token
events across possible worlds.
Cross-world identification of token events arose because of the way Kim
puts his point. He says “…consider a
world in which the physical cause does not occur and which in other respects is
as much like our world as possible. The
overdetermination approach says that in such a world, the mental cause causes a
physical event.” But the
overdetermination approach is committed to no such thing (for reasons already
mentioned and in addition) since the overdetermination approach need not countenance
cross-world identity of token events.
If we are to stipulate cross-world identification of
token events, it would be natural for non-reductivists to resist the idea that
a world in which the molecules are different is a world in which that strangling
does not exist, but is rather replaced by a different strangling. If we non-reductivists are to countenance
cross-world identification of token events, we should not say that token events
have microphysical individuative conditions.
There is a lawlike relation between hurricanes and damage. Hurricane Edna caused damage. But the molecules of air and debris and their
trajectories might have been different—e.g. they would have been different if
there had been distinct nitrogen and oxygen molecules that moved in exactly the
same way as the actual nitrogen and oxygen molecules. Winds in the days before the storm might have
blown in air from somewhere else.
Alternatively, there might have been a micro difference that made a
macro difference, e.g. if there had been more moisture in the air. And even with this alternative molecular
realization of Edna it might have caused similar damage (Lepore and Loewer
1987). If you think there are lawlike
relations at many levels, and you think laws have something to do with
individuation of events and properties, you have some reason to endorse event
individuation at levels other than the physical.[3]
The Exclusion Principle and the Problem of Causal Powers Draining Away
The Exclusion Principle leads to
problems about causal powers draining away.
Kim discusses a number of such problems, including the following
two. First, it is hard to believe that
there is no mental causation, no physiological causation, no molecular
causation, no atomic causation but only bottom level physical causation. Second, it is hard to believe that there is
no causation at all if there is no bottom level of physics. I will usually concentrate on the second, but
many of the points I make transfer to the first in an obvious way.
There is some reason to think that
the hypothesis that there is no bottom level of elementary particles is an open
question from the point of view of the core of contemporary physical
theory. (The no bottom level view is
suggested by Nobel laureate Hans Dehmelt.
See Dehmelt, 1989,) Of course, it
is incompatible with the Standard Model of eighteen elementary particles (six
quarks (the constituents of atomic nuclei), six leptons (including electrons
and neutrinos) and six bosons (including photons)), but there is little reason
to think the Standard Model will persist, as many elementary particle
physicists concede (The Economist, 2000; see also Wilczek, 1996; Walker,
1996). Glanz (2001) describes interviews
with scientists from “a dozen institutions in Germany, Japan, Russia, and the
United States” (p. A1), quoting “theorists” as saying that the Standard Model
“is unlikely to represent natural law at its most fundamental level”, and that
recalcitrant data may be explained by “the possibility that particles believed to
be elementary and indivisible are made of smaller entities…” (p. A21) The
hypothesis that there is no bottom level—that matter is infinitely divisible,
with different properties at each level—appears to be an open question, not a
mere philosopher’s possibility like the possibility that the world was created
5 seconds ago complete with the evidence of an ancient provenance. (I mean ‘open question’ to contrast with
‘merely skeptical question’.)
If there is no bottom level, and if every (putatively) causally efficacious property is supervenient on a lower “level” property (Call it: “endless subvenience”), then (arguably) Kim’s Causal Exclusion Argument would show, if it is valid, that any claim to causal efficacy of properties is undermined by a claim of a lower level, and thus that there is no causation. (Block, 1990, p. 168) This is not a proof, but nonetheless assuming it for the moment, we get the following refutation. It is an open question whether there is or is not a bottom level, but it is not an open question whether there is any causation. It may be an open question whether cigarette smoking causes cancer but it is not an open question whether anything ever causes anything. So something is wrong with Kim’s Causal Exclusion Argument.
Here is a slightly different way of putting it. Consider
The Anti-Reductionist Conditional: If there is no bottom
level, then cancer never causes suffering or death
Suppose
that a lawyer for the R.J. Reynolds, the tobacco company and Johns Manville,
the manufacturer of asbestos uses Kim’s
Causal Exclusion Argument to argue for the Anti-Reductionist Conditional, and
uses that to argue that his clients needn’t pay damages. His argument is this:
given the Anti-Reductionist Conditional, his clients’ guilt depends on an open
question in physics. That is, given the
Anti-Reductionist Conditional and the fact that it is an open question in
physics whether there is a bottom level, it is an open question whether
anything causes anything and therefore whether cancer ever causes death. I hope we all agree that the lawyer’s
argument should be rejected. It is
incompatible with our causal-explanatory practice (cf. Burge, 1993) to regard
the fact that it is an open question in physics whether there is a bottom level
as showing that it is an open question whether cancer ever causes death. (Note: I don’t say that no result in
elementary particle physics could possibly challenge our causal-explanatory
practice.)
But perhaps you think that it is the
Anti-Reductionist Conditional rather than the Causal Exclusion Argument that
should be rejected. I have been assuming
the plausible idea that endless subvenience and the undermining of each level
by the one below shows there is no causation.
But perhaps you are suspicious of the step from the claim that causation
at each level is undermined by the level below it to the claim that there is no
causation. Whether this reasoning is valid depends (you may object) on an open
question involving infinitary reasoning, which we can take to be in the domain
of philosophical logic. But the argument
can easily be modified to accommodate this objection. Consider
The Conservative Anti-Reductionist Conditional: If there is no bottom
level, and if the issue in philosophical logic concerning infinitary reasoning
turns out as I suggested, then cancer never causes death.
And
if the Causal Exclusion Argument were really valid, the Conservative
Anti-Reductionist Conditional could also be used to get the tobacco and
asbestos companies off the hook. The
lawyer’s reasoning would be the same as before except that the issue of whether
cancer ever causes death would now be said to depend on two open
questions, one in physics, the other in philosophical logic.
Someone might reply on Kim’s behalf
that the mere possibility of no bottom level can’t be used against the Causal
Exclusion Argument. Imagine someone
arguing that the mere possibility that the world was created 5 seconds ago with
all the evidence of an ancient age undermines rational belief that cancer ever
causes death. What is the difference
between the skeptical conditional “If there is no past beyond 5 seconds ago,
then cancer never causes death” and the Conservative Anti-Reductionist
Conditional?
Answer: Perhaps it is metaphysically possible that
there is no past beyond five seconds ago, but it is not an open question. The
claim that there is no past beyond five seconds ago is a skeptical claim—unlike
the claim that there is no bottom level of physics. A second and related difference is that our
ordinary inductive practice that establishes and justifies our continued belief
that cancer causes death really would be stymied by the assumption that
there is no past beyond five seconds ago.
But it is not stymied by the assumption of no bottom level. Indeed, prior to the atomic theory of matter,
the belief that matter is infinitely divisible (though not the belief in
different fundamental properties at each level) is reputed to have been as much
part of the educated person’s lore as today’s belief that matter is not
infinitely divisible.
In short, if there is no bottom
level and if there is endless subvenience, then Kim’s Causal Exclusion Argument
would yield absurd results. The Exclusion Principle (that causally sufficient
properties at one level exclude causally sufficient properties at another
level) is to blame and should be rejected.
Even if there is subvenience only down to elementary particle physics,
there is a problem of causal powers draining down that far. Kim does not contest the possibility of there
being no bottom level (81), but he does reject one form of endless subvenience.
Let us now turn to his discussion of that issue.
The Ambiguity of ‘Level’
Kim starts with a version of the
Causal Exclusion Argument that depends on two ideas, the notion of
inter-theoretic level (macro-level vs. micro-level) and the realization
relation—the relation between second order properties and the first order
properties they invoke. Dormitivity in
one sense of the term is the property of having some first order property that
causes sleep.[4] The first order property is the realizer of
the second order property of dormitivity.
The version of the Causal Exclusion Argument Kim begins with is
concerned with the issue of whether second order properties are causally
efficacious with respect to the effects they are defined in terms of. This argument is directed towards a viewpoint
that says that mental properties (and properties of some other special
sciences) are functional properties, a species of second order property.[5] Kim’s response brings in the idea that the
realization relation does not track the micro-macro relation, that is that
orders don’t track levels. The reader
would be forgiven for wondering what all this has to do with the Causal Exclusion
Argument in the form in which I am discussing it here. The version of the Causal Exclusion Argument
I am talking about here does not appeal to orders or to realization but rather
to supervenience. Supervenience of the
mental on the physical is a basic tenet of materialism—one that is shared by
Kim’s reductionism and his anti-reductionist but materialist opponent-- whereas
functionalism about the mental is not.
(And I accept supervenience but not functionalism mainly because of
failure of functionalism with respect to consciousness. Kim may have the same view.) So I have been
ignoring the realization version of the Causal Exclusion Argument in favor of
the supervenience version. And I will
consider only the supervenience version of Kim’s defense against causal powers
draining away.
“In general, supervenient
properties and their base properties are instantiated by the same objects and
hence are on the same level. This again
is a simple consequence of the concept of supervenience: Socrates’ goodness
supervenes on his honesty, generosity, courage and wisdom, and it is the same
person, Socrates, who instantiates both these subvenient virtues and the
supervenient goodness. So the microphysical, or mereological, supervenience
does not track the micro-macro hierarchy any more than the realization relation
does; the series of supervenient properties, one mereologically supervenient on
the next, when we go deeper and deeper into the micro, remains at the same
level in the micro-macro hierarchy, just as the properties ordered by the
realization relation stay at the same level.
This means that the supervenience argument, [that is, the supervenience
version of the Causal Exclusion Argument, which is the version discussed here—N.B.]
which exploits the supervenience relation, does not have the effect of emptying
macro-levels of causal powers and rendering familiar macro-objects and their
properties causally impotent. (86)
Kim’s defense against the line of
thought I am advocating here (mentioned briefly in Block, 1990) is that there
is no problem of the causal powers of mental properties draining to the causal
powers of the properties of cells, molecules, atoms or elementary particles,
for these properties are all properties of the same thing, Socrates, and are therefore
on the same level. He is using a notion
of level keyed to objects. On his notion
of level, the level of a property depends on what it is a property of. Properties of Socrates are on one level,
properties of Socrates’ cells are on another level, properties of Socrates’
molecules are on another level, and so on.
But there is another notion of level, which is keyed to relations
among properties. The following is
plausible: Socrates’ pain supervenes on his neurological properties and his
neurological properties supervene on the biochemical properties of his brain, and the
biochemistry of his brain supervenes on the atomic-physical properties of his
brain, and the atomic physics of his brain supervenes on the
elementary-particle properties (if there are elementary particles) of his
brain. The family of mental properties
can be used to characterize the level of psychology, the family of neurological
properties can be used to characterize the level of neuroscience, the family of
elementary particle properties can be used to characterize the level of
elementary particle physics. These
distinct branches of science and their associated families of properties
plausibly form a supervenience hierarchy, as Kim acknowledges. (“the series of supervenient
properties, one mereologically supervenient on the next, when we go deeper and
deeper into the micro”) No mental difference without a
neurological difference. No neurological
difference without a bio-chemical difference.
No bio-chemical difference without a difference in atomic physics. No difference in atomic physics without an
elementary particle difference. And we
can define a notion of level unlike Kim’s that is keyed to branches of
science. On Kim’s notion of level, if
the object of study is Socrates, the psychological, neurological, bio-chemical,
atomic physics and elementary particle physics properties of Socrates are all
at the same level, despite belonging to different branches of science. On the notion of level I am suggesting (what
Kim calls ‘order’), Socrates’ mental properties are at one level, his
physiological properties are at another level and his atomic properties are at
still another level.
But does the Causal Exclusion Argument depend on the
verbal issue of what one chooses to mean by level’? This question leads to another: how is Kim’s
notion of level supposed to be relevant to the Causal Exclusion Argument? My view is:
Kim’s notion of level is not relevant to the most significant version of
the Causal Exclusion Argument. If you
look back at the argument, you will see that at least in my rendition of it,
the word ‘level’ does not occur. The
relevant premises are that M putatively causes M*, P causes P*, that M
supervenes on P and M* supervenes on P* and that M and M* are mental and P and
P* physical. To the extent that the
argument generalizes to other cases involving levels, the relevant notion of
level is one in which the mental and the physical are distinct levels, even if
they both apply to Socrates.
Of course, Kim may say that that is
just his point: just as the mental and the physical are at the same level, so
in other cases what appear to be different levels are the same, e.g. the
temperature of a gas and the properties of its molecules are both properties of
the gas and thus at the same level in Kim’s sense. But my point is that the problem of causal
efficacy draining away remains even if the draining is from mental properties
of Socrates to neurological properties of Socrates to bio-chemical properties
of Socrates, etc. Kim’s reasoning may
show that causal powers don’t drain from big entities (Socrates) to smaller
entities, Socrates’ parts (particles in his body), but that isn’t relevant to
the issue of causal powers of mental properties draining into the causal powers
of properties of particle physics.
Whether there is a sense of level in which this hierarchy of properties
are at the same level is beside the point.
I’m not sure that Kim would dispute this point. For at the end of his discussion of levels, he says: “Granted that both the supervenient properties and their base properties are properties of the same objects and hence belong to the same ontological level, there still is the problem of intralevel causal exclusion. What we have shown is only that the causal exclusion problem is not an interlevel problem. I will return to this issue in my next lecture.” (87)
So no doubt he would regard the issue I am
raising as the intralevel problem. But
what has been gained in moving from thinking of the problem as an interlevel
problem in Kim’s sense of level to thinking of it as an intra-level
problem?
I suppose that I should concede that
at least Kim has plugged the causal drain from people to cells to molecules to
elementary particles. But that is a
Pyrrhic victory given that the draining issue concerning properties rather than
things remains.
Micro-based Properties
Kim returns to the intralevel issue in the last few pages
of the book. The discussion is
compressed and I am not sure I have got it right. The reply depends on the notion of a
micro-based property. Intuitively,
micro-based properties are “properties of a whole that are characterized in
terms of its microstructure”. (82) More
exactly, P is a
micro-based property º P is the property of being
completely decomposable into non-overlapping parts a1…an such that P1(a1)…Pn(an) & R(a1…an). Here is how micro-based properties figure
into the reply:
…the case of micro-based properties is not at all
parallel to the case of supervenient psychological properties. In the latter case the physical base
properties, presumably certain neurobiological properties, are at the same
level as the psychological properties: they are both had by human beings and
other sentient creatures. This is part
of what generates the problem about mental causation: the causal role of a
mental property had by me is threatened with preemption by another property, a
neural property, also had by me. My
causal powers seem fully explicable not only in terms of but also as
the causal powers of my neural/biological/physical properties. Difficulties of this sort do not arise for
micro-based properties in relation to their constituent properties because the
former do not supervene on the latter taken individually or as a group. Rather, they supervene on specific
mereological configurations involving these micro-properties—for a rather
obvious and uninteresting reason: they are identical with these
micro-configurations…
It follows then that we must grant novel causal powers to micro-based properties at higher levels—novel in the sense that these causal powers are not had by any lower-level properties that constitute them. And, as we saw, the supervenience argument does not apply to them, and their causal roles are not threatened by the supervenience argument. (117-118)
As I read Kim, he
is saying that what stops the draining down of causal efficacy is reaching micro-based properties in the
downward hierarchy. Note that Kim’s
reply doesn’t hinge on whether that downward hierarchy is intra-level or
inter-level in his sense of ‘level’. His
earlier reply (claiming that even if causal powers drain from Socrates’ mental
properties to Socrates’ physical properties, still they are both properties of
Socrates and hence at the same level) seems to play no role here.
What
is it supposed to be about micro-based properties that block the drain? First note that micro-based properties do supervene
on “specific mereological configurations” of micro-properties, as indicated in
Figure 3:
Micro-based
property M-B causes micro-based property M-B*. M-B supervenes on specific mereological
configuration SMC, M-B* supervenes on specific mereological configuration
SMC*
Figure 3
The geometry is exactly the same as in Figure 1. The only difference is that the subvenient property is a specific mereological configuration
of properties rather than a single
property. As Kim notes, the supervenient
property therefore has causal properties not possessed by any single
member of the subvenient configuration.
But why should that make a difference to the draining of causal
powers? Even assuming that we are happy
with the distinction between configurations of properties and individual properties,
does it matter whether the causal powers of the supervenient level drain away
to configurations of properties rather than individual properties?
As I
understand Kim, the answer is that the key feature of micro-based properties is
that they are (always?) identical with the micro-configurations. If water = H2O, a mereological
configuration par excellence, there is no worry about the causal
efficacy of water (that is the property of being water) draining down to H2O—if
H2O is efficacious, so is water, since identicals are
indiscernible. Kim’s view is that mental
concepts—at least concepts of properties that don’t involve consciousness—are
functional concepts. These concepts
specify an occupant of the role.[6] And the properties that occupy the role are
supposed to be micro-based properties.
And those micro-based properties are identical to mereological
configurations of lower level properties.
So the causal efficacy of the mental (outside of consciousness) does
indeed drain down to the physiological, but the physiological doesn’t drain
down any further—at least not in any sense that makes the physiological
inefficacious-- because of an identity between the physiological and the next
“level” down, say the biochemical. And
the biochemical doesn’t drain down any further because of an identity between
the biochemical and say the atomic-physical.
The mental is causally unreal, but the physiological is causally real
and the draining stops there.
Multiple
Composition
But
why can’t micro-based properties be micro-based in alternative ways? Why isn’t jade an example of a micro-based
property, micro-based in both calcium magnesium silicate (nephrite) and sodium
aluminum silicate (jadeite)? Recall that
P is a micro-based property º P is the property of being completely
decomposable into non-overlapping parts a1…an s.t. P1(a1)…Pn(an) & R(a1…an). So
my question is: why can’t a micro-based property have more than one such
decomposition? Perhaps it is a
stipulation about the meaning of ‘micro-based property’ that alternative
composition is precluded. Perhaps the
decision to regard a property as micro-based is a decision to regard
alternative decompositions as variants of a single property. But that stipulation simply changes the terms
of the debate to one about micro-based properties—when and where they
exist. To the extent that there is
multiple decomposition, micro-based properties (that fit this stipulation) will
be hard to find. (I will not use this
stipulation below.)
As I see
Kim’s picture, he recognizes four classes of properties. First, we have functional properties that are
properties in name only, being better construed as concepts or
designators. Second, we have supervenient
properties, third, micro-based properties and fourth basic properties that
don’t supervene on anything and aren’t properties of things that have
parts. Mental properties (that do not
involve consciousness) are functional, that is not genuine properties on a
causal criterion of properties, but rather merely nominal properties, what Kim
calls “designators”, that pick out (on the basis of their role) the properties
of the next lower level, which are themselves micro-based. The mental (again outside of consciousness)
is therefore not causally efficacious “on its own” but the micro-based
properties picked out by mental designators are.
Here is an
example of how the mental might look on Kim’s picture. Thought is a property in name only; there is
no science of thought. But thought in
humans is micro-based in human physiology, and these human physiological
properties are causally efficacious.
Thought properties are functionally analyzable, hence they are “mere
designators” picking out micro-based physiological properties. Pain is like
thought in lacking causal efficacy, but unlike thought, pain is not
functionally analyzable. Pain is
inefficacious because supervenient on the physiological, but the physiological
properties that pain supervenes on in humans are micro-based and hence themselves
causally efficacious. Micro-based physiological properties prevent the causal
efficacy of the mental from draining very far.
These are examples of (1) functional properties (2) non-functional but
nonetheless supervenient properties and (3) micro-based properties.
My
doubts about this picture center on the worry just mentioned concerning
multiple decomposition. Micro-based
properties are supposed to prevent draining away for both supervenient and
functional properties, but Kim’s plugging the draining with micro-based
properties depended on assuming identities (such as ‘water =H2O’) and multiple
composition will preclude such identities.
That there is a problem here will not be news to Kim since he says that
the topic of multiple realization cannot be fully treated in this book. In the hope of drawing him out a bit further,
I will say more about what I take the problem to be.
The
Fragmentation Strategy
One can
object to a putative case of multiple decomposition by objecting to the multiple
or to the decomposition. Suppose
it is alleged that upper level property U has multiple decompositions in two
(and only two) lower level specific mereological configurations, properties L1
and L2. An objector may say that U is identical to the single
disjunctive property whose disjuncts are L1 and L2 rather
than saying that U decomposes separately into L1 and into L2. Kim does not smile on this viewpoint,
regarding disjunctive properties as properties in name only. The obvious alternative to multiple
decomposition for Kim is to say that it isn’t that a single property U can be
composed in two ways, but rather there are two different upper level
properties, say U* and U**, one of which is identical to L1 and the
other of which is identical to L2.
This is Kim’s standard strategy, fragmenting the macro level. But what is the rationale for avoiding
multiple decomposition by fragmenting the macro level? Is it an empirical hypothesis? A metaphysical thesis?
Kim
(1992) considers a possible law:
“Sharp
pains administered at random intervals cause anxiety reactions”. Suppose this generalization has been well
confirmed for humans. Should we expect on
that basis that it will hold also for Martians whose psychology is
implemented (we assume) by a vastly different physical mechanism?...The reason the
law is true for humans is due to the way the human brain is “wired”; the
Martians have a brain with a different wiring plan, and we certainly should not
expect the regularity to hold for them just because it does for humans.
...“Pains cause anxiety reactions” may turn out to possess no more unity as a
scientific law than does “Jade is green.” (Kim, 1992, p. 16)
The thought behind this passage seems to be that where there are multiple decompositions, there are different laws. And where there are different laws there are different kinds. Let us test this idea against some specific examples.
The
rigidity of a rigid body has a role in laws of motion, for example the
conservation of angular momentum. This
law explains for example why leaning while riding a bicycle causes it to
turn. Rigid bodies have a number of
decompositions, for example in a crystalline substance like diamond ( a solid)
and in an amorphous substance like glass (a supercooled liquid). So rigidity appears to be both causally
efficacious and multiply constituted—an affront to the fragmentation
strategy.
Laws at
the level of these different molecular structures explain the conditions under
which a rigid body ceases to be rigid.
Amorphous substances deform and break differently from crystalline
substances. But when not deformed,
rigidity in both appears to be causally efficacious in the same way according
to the same laws of motion.[7] The law of conservation of angular momentum
only applies to a rigid body while it remains rigid. Laws of the particles that make up the rigid
body are more accurate in that they predict and explain what will happen when
rigid bodies cease to be rigid. And the
micro laws are more general in that they apply to particles whether or not they
make up rigid bodies. I suppose that an
advocate of Kim’s view will say that the fact that there are more accurate and
more general laws at the level of particles would undermine the law of
conservation of angular momentum of rigid bodies as a causal law, but this claim
remains to be justified.
The same
issue arises in other cases of laws of ensembles, for example laws of heat and
temperature. An input of heat into a
closed system containing a gas causes the pressure of the gas to go up. Nonetheless, there is a finite probability of
a decrease in pressure due to a coincidence about the positions and velocities
of the particles. In principle, a more
accurate prediction could be based on the behavior of individual particles. The
fragmentation strategy would seem to dictate that temperature and heat are not
causally efficacious. And a similar
upshot attaches to the fact that temperature and heat appear to have one
realization in solids, another in gases, another in plasmas and another in
vacuums. (See Churchland, 1986 and
Blackburn, 1993.) But the claim that
heat and temperature properties are not causally efficacious remains to be
justified.
Water= H2O,
it is said, but this is just shorthand.
Actually water has a more complex structure of rings of H2O
molecules with varying numbers of loose H2O molecules in their
centers. Thus there is some variation
from water molecule to water molecule, depending on the number of loose
molecules within the ring. According to
the fragmentation strategy in the form I am considering, being water wouldn’t
be a causally efficacious property because more accurate predictions could in
general be obtained on the basis of the properties of individual molecules
rather than on the ensemble property water.
And the molecular laws would be more general as well since they would
apply to molecules other than H2O molecules.
A normal human brain and its “entantiomorph”, i.e. its perfect reflection (as if in a mirror) obey the same neurological laws, if there are neurological laws. But the molecules of the two brains are enantiomorphs of one another and thus are chemically different--e.g. they rotate polarized light in opposite directions and interact differently with a variety of dissymmetric molecules. So the neurological laws that are the same in the two brains are purely internal laws. Melatonin pills will have different effects on the two brains (we may suppose) and melatonin pills will have the same effect on one brain that enantiomorphic metalatonin pills will have on the other. (The entantiomorph of the key doesn’t fit the lock but the enantiomorph of the key fits the enantiomorph of the lock.) The laws of the internal operation of the brains are the same, but the parts that constitute the two types of brain are significantly different. A brain and its enantiomorph will behave differently under some circumstances, but the overlap in their behavior appears to have nomological unity. Why is this nomological unity undermined by the fact that there are in principle more accurate and more general predictions at the molecular level?
The
problem for Kim could be put in the following way: Suppose we have good reason to believe all of
the following:
- UaÞUb is a causal law
- Ua has alternative decompositions in
mereological configurations L1 and L2
- L1 and L2 participate in
different laws.
Ua would appear to be both multiply constituted
and causally efficacious in violation of the fragmentation strategy. If L1 and L2
participate in different laws, that counts against regarding Ua as
simply identical to the disjunction of L1 and L2, for the
disjunction of L1 and L2 would not be a genuine property
(from Kim’s perspective). But the option
of regarding Ua as fragmenting into Ua* and Ua**
would seem unpalatable (though perhaps not to Kim) because of the fact that Ua
itself participates in a causal law. Kim
seems to regard the nomological claims of L1 and L2 as
undercutting the nomological claims of Ua—that seems the upshot of
the point of view behind the fragmentation
strategy. The idea would be that
the separate laws of L1 and L2 show that there are no
real laws of Ua but only similar laws of L1 and L2. That is, rather than the law ‘UaÞUb’, Kim would
suppose (on this interpretation) that there are two laws, ‘L1ÞUb’ and ‘L2ÞUb’. If this is
Kim’s view, he owes us a rationale for it.
Suppose
that the rationale is just that this point of view solves problems of mental
causation (and other analogous problems).
But there is another point of view that has an equal claim to solving
problems of mental causation: the point of view that recognizes causal efficacy
at many levels and does not regard them as competing. And this latter point of view also avoids the
problem of causal powers draining away.
In short,
Kim uses the fragmentation strategy to shore up the Exclusion Principle, but
the fragmentation strategy remains to be justified. The Exclusion Principle (and the Causal
Exclusion Argument that depends on it) appears to yield conclusions that
conflict with our explanatory practice.
This conflict entitles us—and causes us--to reject the Causal Exclusion
Argument until these justifications are provided.[8]
References
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Blackwell: Oxford
Block, Ned, 1990, “Can the
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Block, Ned, 1997,
“Anti-Reductionism Slaps Back”, Philosophical Perspectives 11, Mind,
Causation and World, 107-132
Burge, Tyler, 1979.
“Individualism and the Mental.” Midwest
Studies in Philosophy 4: 73-121
Burge, Tyler, 1993. “Mind-body Causation and Explanatory
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Dehmelt, Hans, 1989. ‘Triton,.. electron,.. cosmon ...: An
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Reduction” Philosophy and Phenomenological Research 52, 1-26. Reprinted in Kim’s Supervenience and Mind,
Cambridge: Cambridge University Press, 1993, 309-336
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“Postscripts on Mental Causation”, Chapter 18 of Supervenience and Mind,
Cambridge University Press: Cambridge, 358-367
Kim, Jaegwon, 1998, Mind
in a Physical World: An Essay on the Mind-Body Problem and Mental Causation. MIT Press: Cambridge
McLaughlin, Brian, “Supervenience,
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“The Secret Heart of a Quark,” New Scientist February 17, p. 17.
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