Causal Relevance and Nonreductive Physicalism

Causal Relevance and Nonreductive PhysicalismAuthor(s): Jonathan BarrettSource: Erkenntnis (1975-), Vol. 42, No. 3 (May, 1995), pp. 339-362Published by: SpringerStable URL: http://www.jstor.org/stable/20012626 .

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JONATHAN BARRETT

CAUSAL RELEVANCE AND NONREDUCTIVE PHYSICALISM

ABSTRACT. It has been argued that nonreductive physicalism leads to epiphenominal ism about mental properties: the view that mental events cannot cause behavioral effects

by virtue of their mental properties. Recently, attempts have been made to develop accounts of causal relevance for irreducible properties to show that mental properties need not be epiphenomenal. In this paper, I primarily discuss the account of Frank

Jackson and Philip Pettit. I show how it can be developed to meet several obvious

objections and to capture our intuitive conception of degrees of causal relevance. How?

ever, I argue that the account requires large-scale miraculous coincidence for there to be

causally relevant mental properties. I also argue that the same problem arises for two

apparently very different accounts of causal relevance. I suggest that this result does not

show that these accounts, on appropriate readings, are false. Therefore, I tentatively conclude that we have reason to believe that irreducible mental properties are causally irrelevant. Moreover, given that there is at least prima facie evidence that mental proper? ties can be causally relevant, my conclusion casts doubt on nonreductive physicalist theories of mental properties.

1. INTRODUCTION

Nonreductive physicalism is a widely held theory of the relation be? tween the mental and the physical. Its advocates seek a realist and

physicalist account of mental properties, while holding that most are

irreducible to, but in some way dependent upon, physical properties. They face two main problems. First, while eschewing reduction, can the nonreductive physicalist tie the mental closely enough to the physical in order that her theory may be counted as a genuinely physicalist theory? Second, given the claim that all causal phenomena are fundamentally physical, can the nonreductive physicalist secure our conviction that

mental events can cause physical events, notably behavior, by virtue of their mental properties? The latter, the problem of the seeming causal irrelevance of irreducible mental properties, is the topic of this paper.

I begin by making clearer the major commitments of nonreductive

physicalism and argue that irreducible mental properties, if real, cannot be causally relevant to behavior. I suggest a simple account of causal relevance as a solution, but I show it to be inadequate. Second, I argue

Erkenntnis 42: 339-362, 1995.

? 1995 Kluwer Academic Publishers. Printed in the Netherlands.



340 JONATHAN BARRETT

that a related account, due to Frank Jackson and Philip Pettit, solves

the difficulty for the simple account. I develop this account into a fuller

account of causal relevance that accomodates our intuitions about when

particular types of properties are causally relevant. However, I go onto

argue that the Jackson-Pettit account leaves unexplained how distinct

physical properties could each realize a single mental property and

produce a behavioral effect of a particular kind. Finally, I show that

two alternative accounts of causal relevance fall victim to the same

problem. I tentatively conclude that nonreductive physicalism is com?

mitted to causally irrelevant mental properties and hence, on the as?

sumption that mental properties can in fact be causally relevant, that

there is reason to doubt nonreductive physicalist theories of mental

properties.

2. NONREDUCTIVE PHYSICALISM AND THE ARGUMENT

FOR EPIPHENOMENALISM

Nonreductive physicalism arises from the seeming failure of attempts to

show how mental properties could reduce to physical and/or functional

properties.1 If one is committed to physicalism and one wishes to

resist anti-realist (in the Dummett-Putnam sense) theories of mental

properties, then one has to choose between eliminativism about the

mental and a weaker physicalism that settles for something less than

reduction. Nonreductive physicalists take the latter route.

There is no one nonreductive physicalism. However, all nonreductive

physicalists are committed to three claims. The first two are as follows:

(1) Token Identity of Mental and Physical Events. Each mental

event token is identical to some physical event token.

(2) Property Dualism. In general, mental properties are distinct

from physical and/or functional properties.

By themselves, (1) and (2) are too weak to count as a form of physi?

calism, which requires that everything, all objects, events, processes and properties, are at bottom physical; they are either physical or are

in some way composed out of or dependent upon the physical. To meet

this demand, nonreductive physicalists add a third component. Here

they often diverge from one another.2 However, for present purposes we can operate with a very broad statement of this part of their ac?

counts, one which almost all nonreductive physicalists would accept:



CAUSAL RELEVANCE AND NONREDUCTIVE PHYSICALISM 341

(3) Priority of the Physical. Each mental property is either iden?

tical with a particular physical property or else is realized by some class of physical properties (with the emphasis firmly on the latter).

I use the vague term 'realized' deliberately, as a blanket term covering all nonreductive physicalisms.3 The most discussed realization relations are the many types of supervenience. However, since my discussion

applies to any nonreductive physicalism holding (l)-(3), it is unnecess?

ary for us to get into specific details. I will just assume that there is

an appropriate relation of realization, one strong enough to sustain

physicalism and at the same time weak enough to allow for the existence

of mental properties. Typically, the nonreductive physicalist will main?

tain that a given mental property M will be instantiated whenever one

of a class, perhaps an infinite class, of distinct physical properties Pt,. . . ,Pn is itself instantiated. Moreover, no guarantee is given that

these physical properties will be simple properties. Indeed, it is stan?

dardly assumed that they will not be. These physical properties are the

possible realizers of M and when one is instantiated at some place and

time it is the realizer of M at that place and time.

I should add that nonreductive physicalism is not a doctrine that only concerns the relation between the mental and the physical. Nonreduc?

tive physicalist theories have been defended for other kinds of proper? ties. Amongst these are moral properties, color properties, social pro?

perties and biological properties. My main concern will be mental

properties. However, I shall mention the possible application of my conclusions to other cases at various points.

We now turn to the causal relevance challenge. It is widely accepted that mental events can cause physical behavioral events. My believing that there is beer in the fridge causes me to open the fridge and reach inside. However, we want to say more than this. In addition, we are

inclined to think that my believing that there is beer in the fridge causes

my opening the fridge because it was my believing that there was beer in the fridge and not say, because it was the thought I had exactly two

minutes after the oldest camel in the world died.4 That is, sometimes a mental property, one instantiated in a mental cause, is required to

explain why that mental cause produced a certain physical effect. If so, mental properties must be capable of being causally relevant to be




havior. This commitment, it is argued, cannot be secured by nonreduc?

tive physicalism. The argument closely parallels one directed against event dualism

the claim that mental and physical events are distinct. I begin with this

argument, as I consider one of the moves made in response to it in my discussion of the causal relevance objection to nonreductive physi? calism. It runs as follows:

(A) The Closure of Physical Causation. Every physical event is

caused by a physical event.

(B) If mental events are distinct from physical events, mental

events cannot cause behavior.

(C) Mental events can cause behavior.

(D) So, mental events are not distinct from physical events.

Putting aside the unattractive epiphenomenalist reply, the event dualist

might argue that (A), on its most plausible reading, allows that a

physical event can have both a physical and a distinct mental cause

(causal overdetermination). In cases where we think that a mental cause

is operative, such as in the production of behavioral events, we need

only maintain that the particular effect is causally overdetermined by a mental cause and a distinct physical cause to secure mental causation.

So, by denying that (A) entails (B), we block the route to (D), even

while accepting (A) and (C). The normal replies to the overdetermination move are as follows.

First, while overdetermination allows for mental causes, they are never

causally necessary for behavioral events. Had the mental event not

occurred, there still would have been a physical event that would have

been causally sufficient to produce the behavior. However, it seems

mental events often are causally necessary for physical events. If I want

some beer and so move to fridge and remove some, we ordinarily think

that had I not decided that I wanted beer, I would not have behaved

as I did. An event dualist opting for overdetermination cannot confirm

this, except by holding that the occurrence of the relevant physical event

necessitates the occurrence of the particular mental event. However, it

seems very unlikely that our psychology is so bizarrely causally con?

figured. The second problem with overdetermination is that it violates

the plausible methodological principle that the universe is causally con?

servative: events generally do not have more causes than are necessary. This principle requires us to reject hypotheses that postulate widespread




causal overdetermination. Event dualism plus overdetermination is such

a hypothesis. As stated earlier, there is a close parallel between the causation

argument against event dualism and the causal relevance argument

against nonreductive physicalism. We shall be able to exploit this fact

later when we come to see what responses we can make on behalf

of the nonreductive physicalist. The argument against nonreductive

physicalism runs as follows:5

(A) The Closure of Physical Causal Relevance. Physical causes

produce effects by virtue of their physical properties.

(B) Since mental events are physical events, if mental properties are distinct from physical properties, they cannot be causally relevant to behavior.

(C) Mental properties sometimes are causally relevant to be?

havior.

(D) So, mental properties cannot be distinct from physical pro?

perties (hence property dualism and nonreductive physi? calism are false).

Following the event dualist, the nonreductive physicalist might object that (A), on its most plausible interpretation, does not require that

there is just one causally relevant property per cause-effect relation. If we reject that assumption, we cannot get to (D) so easily. The nonre?

ductive physicalist can hold that when mental event c causes behavioral

event e, not only is some physical property P of c's causally relevant

to c's causing e, but so is some mental property M of c's. This is not

overdetermination at the level of causes or events, but at the level of

causally relevant properties. One property is physical and the other is

mental.

It is natural to respond as we did to the event dualist. First, mental

properties are not just causally relevant but are causally necessary for a mental event's producing a behavioral effect. Second, not only should

we believe superfluous causes are rare, but by similar reasoning, we

should believe that superfluous causally relevant properties are rare

too.6 However, these objections succeed only if nonreductive physi? calism really requires property-level overdetermination. It is unclear that it does, as long as the cause has the causally relevant mental

property M by virtue of the same facts F as it has the causally relevant




physical property P. For then, on the relevant reading, the following counterfactuals are true:

Had c not been P (and so F did not obtain), c would not

have been M (because F did not obtain). Had c not been M (and so F did not obtain), c would not

have been P (because F did not obtain).

There is not then overdetermination at the level of causally relevant

properties because, on the relevant reading, the following counterf ac?

tuals are false:

Had c not been P, c would have caused A.

Had c not been M, c would have caused A.

We might object here that the nonreductive physicalist assumes without

warrant that c is P and c is M in virtue of the same facts F. However, claim (3) of nonreductive physicalism points to a solution. It tells us

that c's being M on some occasion is realized by c's having some

physical property. If this is property P, then c is P and c is M in virtue

of the same facts. This is not a full solution however, because we can

ask why we ought to believe that c's being P both realizes c's being M

and is causally relevant to c's causing A. I take it that the nonreductive

physicalist can currently offer no answer. However, in this respect, she

is in the same position as the reductionist. The nonreductive physicalist maintains that c's being M is causally relevant to c's causing some

effect, because the physical realizer of M in c is causally relevant to

the effect. The reductionist differs only in adding that the causally relevant physical property is identical to M. In each case, whether there

is a physical property that fits the bill is a contingent matter; neither

can rule out epiphenomenalism purely by a priori means.

So, the nonreductive physicalist is in a stronger position than the

event dualist. She can avoid overdetermination by making the following kind of claim (from here I use the term 'causally-relevantphy' to indicate

the uncontroversial causal relevance of physical properties and reserve

'causally relevant' for the alleged causal relevance of some irreducible

properties):

Mental property M of c is causally relevant to c's causing A

iff

(a) for some physical property P, c's being P realizes c's




being M and c's being P is causally-relevantphy to c's causing A.7

However, the proposed condition is not sufficient for causal relevance.

Suppose a single physical property of an event realizes each of two

distinct irreducible properties. According to our condition, both irred?

ucible properties are causally relevant to any effect to which their

physical realizer is causally-relevantphy, whereas intuitively we might

only count one of those irreducible properties as the properly causally relevant one. Frank Jackson and Philip Pettit offer the following exam?

ple.8 Suppose Mary lets her aluminum ladder touch the power line.

She is electrocuted and dies. Her ladder's touching the power line

caused her death, because it was a good conductor of electricity. The

physical property actually realizing this in Mary's ladder, its being made

of aluminum, realizes other properties of her ladder as well - its having a certain thermal conductivity, ductility, luster and so on. According to our condition, each of these properties is causally relevant to her

death too. Clearly, we do not want to say this. Therefore, the simple condition introduced is not sufficient for causal relevance.

3 . PROGRAM EXPLANATION

Having identified this problem for the simple account, Jackson and

Pettit have tried to overcome it by developing an account of program

explanation.9 They count an irreducible property as causally relevant to some effect, when there is "invariance of effect under variation of

realization."10 We can see how their account relates to the simple account by stating it as follows:

c's being M is causally relevant to c's causing A iff

(a) for any P, if P is a possible realizer of M, then had c

been P, c's being P would be causally-relevantphy to c's

causing^.

With this account we can dispose of the objection to our initial account.

Returning to Mary's ladder, no matter how her ladder's being a good electrical conductor is realized, that realizer is causally-relevantphy to her ladder's touching the power lines causing her death. However, some possible realizers of her ladder's being a good heat conductor

would not be causally-relevantphy to her death. These are those possible




realizers that do not in addition realize her ladder's being a good electrical conductor. Therefore, only electrical conductivity and not

thermal conductivity are causally relevant to the effect in question. Moreover, the Jackson-Pettit account captures one of the main points of casting explanations in terms of irreducible properties, namely that

doing so allows us to appeal to lawlike generalizations that in many cases are missing at the physical level.

Despite these features, the Jackson-Pettit account needs fine tuning. I will begin with this and then look to more serious difficulties. First, consider cases in which we over-specify the causally relevant property, ones where c's being M is causally relevant to c's causing e, yet we cite

c's being M and A as causally relevant, even though A has no essential

role to play in explaining c's causing e. Suppose Strawberry hits the

ball 410 feet through center field, causing the crowd to go wild. His

swing's being a hitting of a home run explains its causing the crowd's

going wild, let us suppose. It did not matter precisely how he hit a

home run. Now, if I point to his hitting the ball 410 feet, along a certain

parabolic trajectory, at an angle of say 7? to a line running through home plate and the mound, as the causally relevant property, rather

than just his hitting a home run, have I succeeded in explaining his

causing the crowd's going wild? The Jackson-Pettit accounts says that

I have. Any realizer of that property would have caused the crowd to

go wild. Therefore, it is causally relevant to their going wild.

But this answer should not seem quite right. The best explanation of

Strawberry's causing the crowd to go wild is, in the circumstances, that

he hit a home run. By pointing to precisely what Strawberry did, we

seem to have missed the critical factor. We have instead added all sorts

of what are, in the circumstances, irrelevant extra details. However, this is not to say that the precise explanation offered fails completely to specify the causally relevant property of Strawberry's swing. Given

the explanation offered and the background conditions, it follows that

Strawberry hit a home run. Intuitively, our standards for explanation are not so demanding that we must discount explanations that include

some irrelevant information as well as the relevant information.11

This type of case suggests that we need to distinguish what we might think of as the maximally causally relevant properties from those pro?

perties, like in the Strawberry example, which contain the causally relevant property and some irrelevant properties. To accommodate




these intuitions I propose to revise the Jackson-Pettit account to count

conjunctive properties as causally irrelevant:

c's being M is causally relevant to c's causing A iff

(a) for any P, if P is a possible realizer of M, then had c

been P, c's being P would be causally-relevantphy, to c's

causing A.

(b) there is no property M', distinct from M, such that

c's being M' satisfies (a) and c's being M entails (in the

circumstances) c's being M'.

That is, I will take the Jackson-Pettit account not to be an account of

causal relevance in all cases, but only of certain core cases (CRC). Then we get an account o? full causal relevance (CRF) as follows:

(i) if c's being M is CRC to c's causing e, then c's being M

is CRF to c's causing e.

(ii) if c's being M is CRF to c's causing e, then, if c is M', c's being M and M' is CRF to c's causing e.

CRC properties then are what we might think of as the maximally

causally relevant ones. If we were to be more pedantic in our ascriptions of causal relevance than I think we are, these would be the only ones

we would count as causally relevant. CRF is more permissive. It allows as causally relevant any property of the cause that contains the CRC

property as a component. Thus CRC is sufficient for CRF, but, because

of conjunctive properties, not necessary. However, (ii) allows conjunc? tive properties to be counted as causally relevant. Naturally, we might feel disinclined to count all conjunctive properties with an irrelevant

component as causally relevant. But then the burden is on us to show what is so special about irrelevant conjuncts in some cases and not in others. Given the array of cases in which we think that a conjunctive property with an irrelevant conjunct is causally relevant, I am dubious that such a constraint could be articulated. However, even if a con?

straint of this sort were available, it would not undercut the Jackson Pettit account, for we could merely incorporate it into (ii) above.

These revisions might be thought to dissolve a different problem for the causal relevance of mental properties, one distinct from their

purported irreducibility. This is the problem posed by two theses. First, intentional properties are wide. They involve causal/historical relations




to the thinker's environment as well as internal components of the brain

(a view made popular by Putnam-Burge thought experiments). Second,

only properties internal to the brain can be causally relevant to be?

havior.12 The consequence of these two theses is that intentional proper? ties are not CRC, because, at best, only the internal component of an

intentional property could be CRC. The problem is removed, it might seem, because if the internal components of intentional properties can

be CRC, even if the whole intentional property cannot be CRC, the

whole intentional property can be CR^. I do not think this is a solution, because the question arises of whether common sense can be satisfied

with intentional properties with causally irrelevant external compo? nents. The role of the latter is in fixing certain semantic properties of

beliefs and it is unclear that the commonsense view can tolerate these

properties being causally irrelevant. According to that view, it is the

contents of our thoughts that determines our behavior, they do not just ride on the back of internal and apparently largely contentless proper? ties. Without resolving this difficult problem, the causal relevance chal?

lenge posed by externalism about intentional properties and individ?

ualism about psychological explanation survives. This topic is too big to pursue further here.

We have looked at cases in which we specify the causally relevant

property in excessive detail. Now I want to examine cases where we

fail to give enough detail. I use these to argue for a concept of partial causal relevance, one not captured by the Jackson-Pettit account.

We often apparently explain behavior by attributing a de re belief to

the agent. In such cases, it is simply not true that any realizer of a

particular de re belief would produce the behavior we are explaining.13 For instance, suppose I say that Willy is cheering because he believes

that Superman has arrived. If, as seems quite plausible, I am attributing a de re belief to Willy, then it is likely that Willy would behave differ?

ently were the same de re belief realized differently. How Willy behaves

in the actual and in counterfactual situations depends in part upon how

he conceives of Superman. If in the counterfactual situation his belief

is realized so that his conception of Superman differs from the actual

case (Superman qua Clark Kent and not Superman qua Superman), then he might well not cheer. This counts against the necessity of

Jackson and Pettit's account, because it produces cases in which a

different realizer of a de re belief property, one that intuitively is

causally relevant, produces a different behavioral event.




Cases of this sort are very easy to generate. We might say that a

brain state causes my wincing because it is a pain state. However, there are different kinds of pain and I might only wince if I feel a sharp

jabbing pain. If the pain is a gentle throb perhaps, I might merely rub

the affected area. We can realize being in pain in different ways so that

different realizers have different kinds of effects. Nonetheless, being in

pain is still causally relevant. Second, how I behave on the basis of my belief states might depend not just upon the contents of those states, but also upon the means by which I represent those contents. Repre?

senting the information in one way, my believing that there are six

groups of nine children might cause me to utter, "There are fifty-four children." However, if my belief is represented by mental analogs of

Roman numerals, I might not make the same utterance, because I have no idea how to multiply Roman numerals.14 So, the same thought can

be represented in different ways and thereby produce different effects.

Third, there are degrees of believing and desiring. We might say that

I rented "Oklahoma" because I desired that I see "Oklahoma", without

specifing how much I desire to see it. However, were I to desire to see

it, but a little less than I in fact do, I might not rent it at all.

All of these cases work as counterexamples to the Jackson-Pettit account in the same way. The individuation of the relevant mental states

in these examples, while quite fine grained (it succeeds in identifying the

cause), is still too coarse grained (it fails to identify the CRC property). There are kinds of pain and different kinds produce different effects.

Thus, merely to point to being in pain as the causally relevant property is to specify a property that could not possibly satisfy the Jackson-Pettit account.

One view we might take is that commonsense psychology is simply mistaken in these cases. The properties it counts as causally relevant are actually irrelevant, as the Jackson-Pettit account shows. That seems

wrong. First, the counterexamples I have described are not particularly rare cases that can be set aside or given special treatment. Indeed, they are representative of our ordinary practices of psychological explana? tion. Second, it seems overly fussy to require that to specify a causally relevant property one must specify the entire property that fully explains the causal transaction in question. Our normal standards of explanation rarely require such precision. Third and most importantly, these proper? ties do partially explain the production of the effect and are essential to its full explanation. These are reasons to count properties that are




only partially and not fully explanatory in this way as causally relevant

to some degree. Examples from outside of psychology suggest that this

is the natural line to take. Suppose the stereo caused the walls to

collapse because it was playing very loudly. Then it seems natural to

say that it caused the walls to collapse in part because it was playing

loudly. Not only is its playing very loudly causally relevant, but so is

its playing loudly. In contrast, since they have no role to play in the

explanation of the production of the effect, the stereo's being made in

Taiwan and its having a sleek black finish are causally irrelevant. Thus, it seems, our concept of causal relevance includes both full and partial causal relevance. So we need an account of causal relevance that cap? tures both kinds. Therefore, the Jackson-Pettit account is too strong.

In fact the required revisions are straightforward and do not undercut

the central account. We need only add an extra condition to capture

partial causal relevance (CRP):

(iii) c's being M is CRP to c's causing e iff for some property F of c's, c's being F and M is CRC to c's causing c.15

To this point, the Jackson-Pettit account has withstood the pressures we have subjected it to. Moreover, we have been able to revise the

account so that it rather simply captures different degrees of causal

relevance. Thus far then, it is in good shape. In the next section, I will

introduce what I take to be the real problem for the Jackson-Pettit

account.

4. MIRACULOUS COINCIDENCE

Tu2 cases of partial causal relevance we discussed above had a common

reature. The extra property needed to give the core causally relevant

prof? ty was a psychological property, a property that is part of com?

monsense psychology, or at least of philosophical refinements of that

theory. Now I want to look at cases in which commonsense psychology cannot itself supply the extra necessary information to give us the CRC

property. Here is a case in which such a sub-mental difference is crucial. I am

out one cold day. Feeling thirsty and in need of warmth, I stop at a

cafe to buy a hot drink. I do not care greatly whether I get tea, coffee

or hot chocolate. I like them all equally and believe that any one of

them will, on this occasion, satisfy my needs. When asked for my order,




I say, "Coffee please." However, at no point did I form a desire to get coffee specifically, I just desired a hot drink. Plausibly, being my desir?

ing a hot drink is causally relevant to some brain state of mine causing me to say, "Coffee please." However, it might be that for some alterna?

tive physical realizers of that desire, had it been realized by one of

them, I would instead have said, "Tea please", or "Hot chocolate

please." Moreover, it might be that these different possible utterances

of mine result directly from sub-mental physical differences in the

different realizations of my desire. Thus, different realizers produce different behaviors, yet each realizer realizes my desire for a hot drink

and intuitively that desire is causally relevant to my saying, "Coffee

please", in actuality. The case seems perfectly coherent. To explain how sub-mental differ?

ences might lead to different behaviors, we need only suppose, for

example, that the search order or mechanism for hot drink words is

partially dependent on which physical realizer of the desire is in?

stantiated. Indeed, I would have thought that we should in fact expect such cases to arise, given the complexity of our brains and the seeming indifference of commonsense psychology to neurophysiology. However,

my objection here only requires the mere possibility of such cases.

We have a case in which an apparently causally relevant mental

property's effect is realizer dependent and so the property does not

satisfy the Jackson-Pettit test. Now, if troublesome realizers are rela?

tively rare, if say for all but one possible realizer of my desiring a hot

drink I would say, "Coffee please", then maybe there is no problem.

Presumably, the Jackson-Pettit test allows some leeway, even if it does

not explicitly say so. It is widely accepted that where there are lawlike commonsense psychological generalizations, they do not hold without

exception and I see no reason why Jackson and Pettit should not be

allowed to relax their condition in recognition of this. However, to

avoid this reply, let us imagine that there are lots of troublesome

realizers in this case. Then it is not true that any realizer would produce a request for coffee (ceteris paribus).

In that case, it seems to me to be natural to say that the mental

property in question, my desiring a hot drink, is causally irrelevant to

my saying, "Coffee please." Rather it is some physical property, the

physical property that in fact realizes my desiring a hot drink on this

occasion, that is causally relevant. Recall that mere realization by a

causally relevant physical property, unless the realizer is identical to




the realized property, is not sufficient for causal relevance. That is the

simple view we considered and rejected at the outset. This claim might seem to clash with our intuitions about the case. One thing I can say to ease the discomfort is that my desiring a hot drink is still causally relevant to my behavior under the description ordering a hot drink, for

every possible realizer of the desire does cause an ordering of a hot

drink. We could redescribe the case so that this was not so, so that some realizers cause my ordering coffee, some my killing the waiter, and yet others my doing a fine imitation of Madonna. But then it would seem even clearer that no mental property was causally relevant to my

saying, "Coffee please", and that counts as evidence in favor of my

interpretation of the case.

If I am right, the widespread troublesome realizer is not a problem for Jackson and Pettit, for they can plausibly argue that in these cases

the apparently causally relevant property is in fact causally irrelevant.

However, this is where the real problem for them begins. If troublesome

realizers are very common, then rarely, if ever, could an irreducible

mental property be causally relevant. Of course, a nonreductive physi? calist will simply deny that we have reason to believe that they are

common. However, if we look at the nature of nonreductive physi? calism, we quickly find a reason.16 Suppose c causes e and intuitively c's being M is causally relevant to its causing e. Suppose that M on this

occasion is realized by physical property Pi, but that any of properties Pi,. . . ,Pn would have realized M had one of them been present in c.

For M to be causally relevant the Jackson-Pettit account requires that

the presence in c of any otP1,. . . ,Pn would in the circumstances make c cause e. But, given that these realizers have nothing physical/func? tional in common (M is irreducible), we should expect there to be lots

of troublesome realizers for M. Thus, we should expect large scale

mental causal irrelevance.

Now the nonreductive physicalist will deny that we should have this

expectation. That she may do, but she then owes us an explanation of

how a set of physical properties with nothing physical/functional in

common realize a single mental property and produce effects of a

common type. Without such an explanation, we appear to have miracu?

lous coincidence on a large scale. That, I take it, is something we

cannot accept. In other words, if no explanation is forthcoming, then

either the Jackson-Pettit account is too strong or we are forced to

accept widespread mental causal irrelevance.




Can we explain away the apparent coincidence? One way is to view

the irreducible mental property as a dispositional property: a physical

property realizes M just in case it would cause an event of the appropri? ate kind in the appropriate circumstances. However, clearly this is a

reduction and so it is not a move that is open to the nonreductive

physicalist. Indeed, the suggested line is probably going to end up as

a commitment to a form of functionalism, a position which nonreductive

physicalists explicitly reject. How else are we to explain why all these distinct physical properties

produce effects of a common type? David Papineau suggests we employ a selectional explanation.17 All these different properties produce a

common effect because they were selected to do so. Selection here

need not be confined to natural selection, but can also include, for

example, the design of an intelligent agent or the selection that occurs

as part of the developmental process. The last of these is held by

Papineau to be particularly important to the psychological case. In the course of development, he hypothesizes, a neural pathway is strength? ened when its activation produces favorable outcomes and weakened

when its activation yields unfavorable outcomes. It is then no accident

that many different physical properties produce events of common

kinds, because, any available physical property can be recruited to

produce appropriate behavior, subject, of course to the limits of neuro

physiology. Thus, it is unsurprising that the developmental process selects different properties in different organisms and maybe in a single

organism at different times.

That the details of Papineau's selection account are sketchy does not

undercut his argument. All we can reasonably expect is a plausible

story of how different physical properties might produce effects of common kinds. However, even if we allow him this much slack, I do not see that selectional explanation solves our puzzle. He has explained how distinct physical properties might have common effects, but I

thought the task was to explain how distinct physical properties that are possible realizers of a single mental property might have effects of a common kind. An answer to the former question is part of an answer

to the latter, but it is not sufficient by itself. For all Papineau has said, we have no more reason to think that a set of distinct physical properties with a common effect each realizes a common mental property than to

think that they all realize different mental properties or no mental

properties at all. Similarly, he has given us no reason to think that all




the possible realizers of a mental property will all be selected to cause

a common effect.

To see this, consider a number of devices each with a button on it.

When the button is pressed a buzzing sound issues from the device.

Even though these devices might be physically very dissimilar, their common response to having their button pressed can be explained,

perhaps as the result of an inventor's exploration of the different ways of building a buzzer. Such Papineau-style selectional explanations seem

perfectly acceptable in these cases. However, they only explain how

physically different devices produce the same effect. They do not ex?

plain in addition why each of these devices say, is red, or was once

owned by Louis XIV, or is coveted by several antique collectors (or whatever irreducible property you care to pick).

In the psychological case, I suppose Papineau's reply must be that the

distinct physical properties all brought about behavior with favorable

consequences and so were recruited to produce that behavior, because

they each individually realized a certain irreducible mental property. The idea here is that one's beliefs, desires and other mental states are

good indicators of when behaving in a certain way will have positive consequences or will avert negative outcomes. Such a view is initially

plausible. We all like to think that the hard work we put into acquiring new beliefs, checking their veracity, weighing our desires against one

another, discovering what our desires really are and so on is in some

way in our interests. However, this is not sufficient to secure the re?

quired claim. We need, in addition, a possible mechanism that explains the postulated correlation between the presence of certain beliefs and

desires and the beneficial effects of certain behaviors.

The obvious move here is to hold that physical states of types Pi,. . . , Pn, (realizers of mental property M) tend to be caused by environmental states of type C and that M's are recruited as causes of

behavior of type B just in case 2?-ing in conditions C is beneficial. Thus, the occurrance of C fixes both the instantiation of a particular mental

property and the causing of a particular effect by that mental property under its different realizations.

I believe this position is very implausible. There are three big assump? tions it must make. First, it has to assume that environments are rela?

tively static; static enough that C still obtains when the organism pro? duces B. Otherwise, there is no guarantee that 5-ing will be

advantageous to the organism and hence no reason to expect the link




between realizations of M and B-ing to be reinforced. One might

respond that one need not hold that C still obtains, but need only

require that the environment has evolved in a certain way that makes

B-ing beneficial. However, this merely redescribes the difficulty. Now

we have to hold that environments, while not static, evolve in orderly

patterns. But, the rich diversity of everyday experience strongly sug?

gests that this is not so. Environments change quickly and unpre?

dictably. So much so that it looks like it would be pure luck if selectional

processes made the mental fit with behavior in the way Papineau de?

sires.

Second, our account has to assume that the environmental factors

producing the particular mental state are identical to (or very intimately connected with) those environmental factors that bear on the likely value to the organism of producing a certain behavior. However, only one small piece of my current environment will often be salient to my

coming to hold some belief. It would seem extraordinary to claim either

that such a small part of my environment determines the likely value

of future behavior or that those parts of my environment that do

determine this are themselves dependent in some way on that small

part upon which I formed my belief.

Third, the part of the environment that causes a mental state can

itself take many forms. My believing that father has returned might result from seeing him come into the room, from seeing his identical twin come into the room, from hearing banging and cursing downstairs, from reading a letter and so on. It is hard to believe that any of these events favors a single beneficial behavior for the organism.

So, despite Papineau's suggested solution and my developments of

it, the miraculous coincidence problem still remains for the Jackson Pettit account. Furthermore, even if Papineau's selectional explanations can be made to remove the miracle of causally relevant irreducible

properties in psychological cases, there will still be a range of cases

where selectional explanations do not seem to be available. Take color

properties and moral properties for example. If these are irreducible

properties, as many nonreductive physicalists adamantly maintain, and their instantiations are sometimes causally relevant, it is hard to see

what sort of selectional explanation will explain the causal relevance of their various realizers, since these properties do not seem to have been

selected to cause anything. Suppose that Cindy's t-shirt's being white

explains her keeping cool. Seemingly, the t-shirt's being white is claimed




to be causally relevant to Cindy's coolness. Yet nothing, it seems, has selected physical realizations of whiteness to be cooling.

I conclude that Papineau's selectional explanations do not explain away miraculous coincidences in either the psychological case or for

irreducible properties more generally. Consequently, it seems that the Jackson-Pettit account is too strong. It overcame the objection to our

initial simple account of causal relevance by introducing the strong requirement that other possible realizers of a causally relevant irreduc? ible property would have been sufficient to produce the effect in the circumstances. That lead to the miraculous realizers problem. Thus, if there is no way around the miraculous coincidence problem, and I do not see one, either we reject Jackson and Pettit's account or we hold that all irreducible mental properties are causally irrelevant.

5. ALTERNATIVES

If we opt to reject the Jackson-Pettit account, we really need an alterna? tive. Although it is unfortunate for the nonreductive physicalist, there is no obvious alternative to their account. Certainly, there are alternative

accounts, but they seem to me to be most plausible when interpreted to be variants on the Jackson-Pettit account. I will briefly look at two

of these, Jerry Fodor's account in terms of hedged causal laws and Brian LePore and Barry Loewer's counterfactual account.

Fodor has suggested an account of causal relevance that goes some?

thing like as follows:18

c qua F is causally relevant to e qua G iff

(a) c causes e, c is F and e is G,

(b) Fs cause Gs is a (possibly hedged) law.19

The contentious claim here is (b). Fodor has to explain why we should ever expect there to be such laws if we do not believe that mental

properties are reducible. Fodor's account is in terms of a language of

thought (Mentalese). Roughly, to believe that hockey is the thinking man's sport is to stand in the believe relation to a sentence in Mentalese

that means that hockey is the thinking man's sport. Thought processes,

according to Fodor, are computational operations upon syntactic pro?

perties of Mentalese sentence tokens. For example, the inference from

the belief that hockey is the thinking man's sport to the belief that

hockey is a sport requires a computational process that takes as its




input the Mentalese correlate of the former belief and produces as its

output the Mentalese correlate of the latter belief. Thus, the causal

powers of belief- and desire-properties are grounded in the causal

powers of the syntactic properties of their Mentalese correlates and

hence we can explain there being hedged psychological laws in terms

of there being computational laws. Now this account certainly takes a

lot of the apparent magic out of the idea of there being causally relevant

mental properties, but I do not see how it overcomes the problem of miraculous coincidence. Fodor is committed to many-one relations

between ontological levels at at least two points. First, he holds that

many different physical states can realize a single computational pro?

perty. Second, he holds that many different computational states can

realize a single intentional property. I am unsure whether this makes

Fodor a nonreductive physicalist. It will depend upon how exactly he

individuates properties at the computational and intentional levels (for

example, individuation by functional role or by computational role are

normally rejected by nonreductive physicalists). Whatever, for the sake

of argument, let us suppose Fodor is a nonreductive physicalist. In that

case, we are going to have to explain how any realizer of mental

property F will, ceteris paribus, produce a realizer of G, even though the various possible realizers of F have nothing physical and/or compu? tational in common. That is just the miraculous coincidence problem that I have argued that the nonreductive physicalist cannot explain and

there is nothing in the language of thought hypothesis, short of render?

ing it in reductionist terms, that offers any form of solution.

I should add that Fodor is somewhat dismissive of the problem of

mental causal relevance in his claim that hedged psychological laws are

sufficient for mental causal relevance. He argues that our success in

predicting behavior by appeal to mental properties is evidence that there are hedged laws linking mental properties to behavior and that these laws by themselves are grounds for thinking that mental properties can be causally relevant. Of course that is right, but it does not solve the problem for the nonreductive physicalist. Rather it highlights the

difficulty she faces, namely, how can irreducible mental properties be

causally relevant so that there can be hedged psychological laws? To

try to solve this problem solely by appeal to the existence of hedged psychological laws just begs the question.20

I now turn to LePore and Loewer. They have recently defended a

counterfactual account of causal relevance:21




c qua F is causally relevant to e qua G iff

(a) c causes e, c is F and e is G,

(b) were c to be F, c would cause e (or cause e to be G),

(c) were c not F, c would not cause e or e would not be G.

A favorable portrayal of this account requires attention to how (b) and

(c) are to be read. On an uncharitable reading (b) is vacuous: since the

nearest world in which it is satisfied is the actual world, (b) is satisfied

by any property c actually has. I assume LePore and Loewer have in

mind a more interesting reading where we look at a range of cases in

which c is F, including ones where c lacks other properties it has in

actuality. Then not every property of c's will satisfy it, because in a

world in which c lacks the genuinely causally relevant property, c will

not cause e no matter which irrelevant properties it has. If, to satisfy

(c), we require no effect when c lacks only F, we get an intuitively attractive account of causal relevance whereby a property is causally relevant to some effect just in case its presence or its absence makes the

difference between, respectively, the occurrence and non-occurrence of

the effect.22

Whatever other criticisms we might want to make of their view23,

my concern here is only with whether LePore and Loewer's (b) can be

read in such a way that we do not have to consider counterfactual cases

in which the mental property is realized by a different physical property to the one that realizes it in actuality. If it can, then it looks like they can avoid the miraculous coincidence problem, for it would not matter

to them what the effects of alternative realizers are. If it cannot, then

LePore and Loewer's (b) implies sameness of effect across variation in

realization and thereby inherits Jackson and Pettit's problems. Recall that appeal to the effects of alternative realizers was invoked

by Jackson and Pettit to overcome the case in which the causally

relevantphy physical realizer realized more than one property of the

cause, the intuitively causally relevant property and an intuitively caus?

ally irrelevant property. If LePore and Loewer's (b) does not require variation in realizer in the counterfactual cases, then Mary's ladder's

being a good heat conductor will satisfy the condition. If we are to

avoid this property being counted as causally relevant to the ladder's

causing her electrocution when resting on the power lines, it must be

that it does not satisfy LePore and Loewer's (c). There must be an

appropriate reading of (c) on which were Mary's ladder not to be a




good heat conductor, Mary would still be electrocuted. Such a case

would be one in which the actual physical realizer of both the ladder's

electrical conductivity and its thermal conductivity is replaced by a

physical property that realizes only its electrical conductivity and not

its thermal conductivity. It appears that (b) does not require sameness of effect as the realizer

is varied, if we adopt this particular reading of (c). Thus, it does

not seem that LePore and Loewer inherit the miraculous coincidence

problem. In fact, it turns out that they do have the same problem. The

sameness of effect as realizer is varied assumption is not made in (b), but is required in (c) to preclude causally irrelevant properties that are

realized by the causally-relevantphy physical realizer in actuality, the

ladder's thermal conductivity, from being counted as causally relevant.

In the ladder case, we have to assume that there is an alternative

realizer of the causally relevant property, its electrical conductivity, and

not of the irrelevant property, that produces the relevant effect. If we

are to avoid this problem, then it looks as if the sameness of effect as

realizer is varied assumption has to built into (b). Either way, LePore

and Loewer face a miraculous coincidence problem just like Jackson

and Pettit do.

My suspicion here is that the LePore-Loewer account, like the Fodor

account, is best regarded as a variant on the Jackson-Pettit account.

Indeed, to conjecture further, I think that the miraculous coincidence

problem does not reveal that something is wrong with the Jackson

Pettit account or these other accounts. They all seem to be the kinds

of stories one would try to tell to show how irreducible properties could be causally relevant. Rather it strongly suggests that nonreductive

physicalism cannot make sense of the causal relevance of the irreducible

properties it postulates. If this is correct, then it counts against the

appeal of nonreductive physicalism, unless the nonreductive physicalist can show that she can get by with causally irrelevant mental properties. I tried to suggest that she cannot, by appeal to the claim that we

intuitively think that our mental states cause the behavior they do

because they are those states. My belief that it is raining causes me to

put on my hat precisely because it is my belief that it is raining. This sort of consideration has standardly been the reason for taking issues

of mental causal relevance to be important. However, it has always seemed to me to be an appeal to apparent intuition rather than a

clearcut argument. Therefore, in my view, the nonreductive physicalist




has reason to see if she can deny the apparent intuition. That is too

large a task to pursue here.24

NOTES

1 See, for example, Schiffer (1987, pp. 19-47).

2 Until recently, most nonreductive physicalists stated the third part of their account in

terms of a relation of supervenience holding between mental and physical properties. Differences arose over which specific relation of supervenience was required to sustain

physicalism (strong versus weak, local versus global; see Kim, 1984, on supervenience and its varieties). Now, the relation of supervenience is increasingly regarded as being too

weak to sustain physicalism (e.g., Kim, 1989 and Charles, 1992). Stronger nonreductive

physicalisms are now appearing (e.g., Charles, 1992). 3

See Segal and Sober, (1991, pp. 9-10) on mereological supervenience for a discussion

of important constraints on realization in the context of issues of mental causation. The

commitments I attribute to the nonreductive physicalist are actually considerably stronger than some would accept. Some do not require that a particular instantiation of a mental

property must have a definite physical realization. They make the weaker claim that

mental properties of an object as a whole supervene on the physical properties as a whole

of that object. See Worley (1993) for an interesting defence of the causal relevance of

the mental given such a view. I do not intend my arguments in this paper to apply to

this sort of position and it is a substantial further question, which I shall not pursue, whether they could. I am inclined to think that very weak nonreductive physicalist views

are not properly physicalist. Again, that it is not a question that I can deal with here.

See the references in note 2 for some of the arguments for this view. 4

A detailed account of these reasons would sidetrack us hopelessly. One of the fullest

discussions, which links the causal relevance of mental properties to rationality, is Lennon

(1990, pp. 38 and 42-45). I think that the details of Lennon's argument are problematic.

However, they at least indicate the kinds of reasons people have for thinking mental

causal relevance is necessary. See Barrett (1994) for arguments, including a discussion

of Lennon, that a Davidsonian account of rationalizing explanation does not require

causally relevant mental properties. 5 The argument is at least hinted at, and sometimes given a fuller treatment, in, for

example, Fodor (1990), Honderich (1982, 1984), Horgan (1989), LePore and Loewer

(1987, 1989), and Sosa (1984). 6

In attacking dualism, Schiffer (1987, p. 151) makes the related move of arguing that

we should not believe that there are superfluous causal laws. 7

A distinct possibility is that the immediate (i.e. neurological) realizers of mental proper? ties are themselves irreducible and hence non-physical. The claim embodied in the

condition must then be that the ultimate realizers of the mental property are causally

relevantphy. 8 Jackson and Pettit (1990).

9 Jackson and Pettit (1988, 1990, 1992).

10 Jackson and Pettit (1990, p. 205).

11 A particularly compelling example in this respect is due to Segal and Sober (1991, pp.

14-16). The environment caused the struck match to ignite because it contained air, we




might claim. But, in fact it was because it contained oxygen and air is only 30% oxygen.

However, learning this would hardly make us withdraw our original claim. 12

For a careful attempt to state this argument, see Fodor (1987, pp. 27-33). 13

This example was suggested by Brian Loar. 14

This problem is now part of the folklore of artificial intelligence (and partly motivates

connectionist alternatives to classical AI-see McClelland, Rumelhart and Hinton, 1986).

Supposedly, researchers originally thought that the architecture of representation was an

issue secondary to showing how representations are manipulated in thought. Soon how?

ever, it became obvious that the manner of representation adopted affects how easily one can construct an algorithm for a particular kind of reasoning. See, for example, the

debate over analog versus digital representations in discussions of mental imagery (Tye,

1991). 15

There is no danger of this condition counting irrelevant components of conjunctive

properties as CRP, because we stipulated that the Jackson-Pettit account counts conjunc? tive properties as irrelevant. Also, while this condition does count disjunctive properties in preemption cases as CRP, this is not a problem because these properties really are

CRP, though admittedly their importance is not great. 16

This problem is stated in Papineau (1985, 1992); see also Cussins (1992). The argu? ments there are not directed against the Jackson-Pettit account, but they have obvious

application to it. 17

Papineau (1992, pp. 60-68). 18 Fodor (1990). 19

As a side point, the conjunction of (a) and (b) is not sufficient, because (b) might be

true even though Fs do not cause Gs by virtue of being Fs. Contrary to Fodor's account, these Fs are not causally relevant, because we would in principle be able to explain Fs

causing Gs without appeal to Fs or its realizer's causal relevance. This point is due to

Segal and Sober (1991, pp. 4-5). They show how it can be overcome by adding to the

account. 20

My thanks to an anonymous referee for pushing me to discuss Fodor's view more

fully. 21

LePore and Loewer (1987, 1989). The account given in Horgan (1989) is closely related. 22

LePore and Loewer (1989, p. 190). 23

See Barrett (1994) for some other objections to counterfactual accounts of causal

relevance. 24

My thanks to John Dreher, Hartry Field, Janet Levin, Brian Lear and Barry Schein

for their criticisms of a distant ancestor of this paper, to two anonymous referees for

Erkenntnis for their helpful suggestions, and to Gawaine Batchelor and Harry Brighouse for discussions of causal relevance issues.

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Manuscript submitted April 25, 1994 Final version received October 25, 1994

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Causal Relevance and Nonreductive Physicalism

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