Crazy causal mechanisms and impossible laws

In Psychosemantics the primary argument against the claim that the Putnamian twins constitute a counterexample to the thesis that the causal powers of mental states are locally supervenient runs thus. If the properties of being an H-particle and being a T-particle affected the causal powers of whatever particle had them, then the causal powers of a particle would depend on the orientation of Fodor's dime. For the causal powers of a particle to depend upon the

orientation of Fodor's dime, there would have to be a causal m echanism or a fundam ental law of nature to m ediate the dependency. But there aren't any such mechanisms or laws, for if there were, Fodor's dime would be able to causally influence every particle in the universe, something that it clearly cannot do. In short, to claim that the property of being an H-particle and that of being a T- particle affects causal powers is to postulate "crazy causal mechanisms" or "impossible laws". To hold that the psychological states of the twins differed in their causal powers would similarly be to postulate crazy causal mechanisms or impossible causal laws. If the psychological states of the twins differed in their causal powers, then the causal powers of such states would depend upon the character of the environment in which the individual who had them existed. For there to be such a dependency relationship there would have to be some mediating mechanism, a mechanism that enabled the character of an individual's environment to affect the causal powers of his psychological states without affecting his physiology.

But there is no such mechanism; you can't affect the causal

pow ers of a person's m ental states w ithout affecting his physiology. That's not a conceptual claim or a metaphysical claim, of course. It's a contingent fact about how God made the world. God made the world such that the mechanisms by which environmental variables affect organic behaviours run via their effects on the organism's nervous system, or so, at least, all the physiologists I know assure me. (1987, p. 40).

How should we respond to this argument? Fodor's thought (as evidenced by the above quoted passage) seems to be that it is a mistake to hold that there is a dependency relationship between the character of an individual's environment and the causal powers of his psychological states, because such a view leads to the absurd conclusion that changes in an individual's environment can cause changes in the causal powers of his psychological states without having any effects on his physiology. A first problem with this is that the supposedly absurd upshot is not obviously absurd. Certainly there are plenty of examples from outside psychology where the causal powers of a thing change due to changes in the environment

w ithout the entity in question undergoing any internal physical changes. For example, I have the power to lift Fang. That I have this power depends partly on the character of the world external to me, in particular on how heavy Fang is. Had Fang been twice his weight then, given how I am internally, I wouldn't have the power to lift him. The world could change in such a way that, without causing any internal changes in me, I lost my power to lift Fang and thus underwent a change in my causal powers. This would happen if Fang underwent a spurt of growth that pushed him to twice his present weight.GO Perhaps there is a psychological analogue to such a case.

Causal powers are powers to produce effects in the world. These effects are often at some distance from the power-bearing individual in question. Moreover, they are often described and individuated in terms of relational properties that are fixed by distant facts in the world. Consequently, it is not at all surprising that a thing's causal powers could change without it undergoing any intrinsic physical change; for the change in causal powers could be brought about by changes in the external world. To say this is not to make such changes in causal powers miraculous, mysterious or inexplicable. Nor is it to sever the connection between the physical and the causal powers of things, for the kinds of distant changes, and changes in relational properties, that can affect causal powers will always be the products of physical changes in the world. For example, my losing the power to lift Fang is a result of a physical change in the world, namely, a change in his size and weight, even though it is not the result of a change in my intrinsic physical properties.

It might be objected that my causal powers haven't changed at all in this case as the maximum weight that I can lift will have remained unchanged. In response, I would say that certain of my causal powers have remained unchanged, but my powers with respect to lifting Fang are not among them. How we describe and individuate effects will influence how we describe and individuate causal powers. And how we describe and individuate effects is an interest relative matter. Given my interests and purposes it makes good practical sense to describe and individuate effects in terms of the individual objects involved so that my lifting Fang at tl is an event of the same type as my lifting him at t2, despite the fact that his size and weight has changed between these two points in time. Thus, when Fang grows too heavy for me, I can no longer cause an effect of a type that I could once bring about with ease.

It is important to realise that to hold that there could be a psychological analogue of the example of my losing the power to lift Fang isn't to contradict what Fodor's physiologist friends assure him. Of course an environmental event can't cause a behavioural event without affecting the individual in question's physiology. But the events the possibility of which the externalist envisages are events of a different kind from such behavioural events, for they are constituted by a stable, pre-existing state's undergoing a change in certain of its dispositional properties. If this sounds unconvincing consider my power to lift Fang. Intuitively the event of my lifting Fang is a fundamentally different kind of event from that of my losing my power to lift Fang. The latter event, unlike the former, involves a change in my dispositional properties and can take place w ithout my undergoing any internal physical change. The physiologist does not mean to rule out the possibility of such events, but only the possibility of events of the first sort. In other words, the physiologist only means to rule out the possibility of such events as that of my lifting Fang in response to an event in the environment without my undergoing any internal physiological change.

A second objection to Fodor's argument is that to view the psychological states of the twins as diverging in their causal powers is not thereby to commit oneself to the allegedly absurd consequence that he describes. Davies expresses the point in the following m anner.

Now, a typical consequence of externalism is that, if a

neurophysiological twin of an actual subject had been set in a

different environment then our actual taxonomy would not have applied in the counterfactually imagined environment to classify the twin in the same way as the actual subject is classified. In that

sense, he would have been psychologically different from the

actual subject. But it does not follow from this that a way of

making the actual subject psychologically different in those ways

is by changing his environment now. Still less does it follow

from the externalist claim about the counterfactual environment,

that we can make the subject psychologically different now

To see this consider the case of the Putnamian twins. Oscar's water thoughts are water thoughts (as opposed to twater thoughts) not just because he lives in a watery world, but because he stands in a certain complex causal relationship to water, or because he has a history in which certain causal interactions with water figure. The standard intuition is that these causal relationships are such that they would not be overridden were Oscar transported to Twin Earth.^^ His being on Twin Earth and interacting with twater wouldn't be enough to make any of his thoughts twater thoughts. Similarly, were Oscar2 transported to Earth, the thoughts resultant of his interactions with water, and those underlying his utterance of sentences containing the word "water", would not be water thoughts; rather they would be twater thoughts.

However, a qualification is needed here. The standard intuition also has it that were a transported Oscar to hang around Twin Earth long enough, his "water" thoughts would eventually become twater thoughts for he would eventually become embedded in a twatery world and a linguistic community that used the word "water" to

mean twater . This raises the possibility of a transplanted Oscar being

neurophysiologically identical to one of his previous selves yet having thoughts that diverged in their causal powers from their earlier counterparts. But this isn't quite an instance of the "absurd" consequence that Fodor accuses the externalist as being commited to. For in the period intervening between Oscar's having water thoughts and his having twater thoughts there is an awful lot of causal interaction between Oscar and the Twin Earth environment (and in particular between him and the linguistic community on Twin Earth). Without such causal interaction he would not have become sufficiently embedded in the Twin Earth environment to be capable of having any twater thoughts. Thus this case is very different to that where a particle changes from being an H-particle to being a T-

This would appear to be accepted by Fodor, as is indicated when he says:

although I've heard it su ggested that m ental states construed nonindividualistically are easily bruised and don't 'travel', the contrary assumption would in fact seem to be secure. The standard intuition about 'visiting ’ cases is that if, standing on Twin Earth, I say "That’s water" about a puddle of XYZ, then what I say is false . Which it wouldn't be if I were speaking EnglishZ.

particle (and thus from engaging in H-particle interactions to engaging in T-particle interactions) as a result of a change in the orientation of Fodor's dime. This is because in this case the change isn't the consequence of a complex history of causal interactions between the particle in question and Fodor's dime.

These two objections to Fodor's first major argument against the claim that the psychological states of the Putnamian twins diverge in their causal powers are hardly conclusive. However, I do think they serve to dent his argument somewhat. What is needed is a detailed examination of the nature of causal powers that does justice to the intuition that a thing's causal powers are determined by its intrinsic physical nature, yet explains that and how there can be differences between the causal powers of distinct things (and changes in a particular thing's causal powers) in the absence of intrinsic physical differences (and changes). This is a task that I will put off until section 5.6. In the meantime I will turn my attention to Fodor's second argument, an argument that appears in 'A Modal Argument for Narrow Content'.

5.5 A modal argument

It will be helpful to recall the putative counterexample presented by the case of the Putnamian twins to Fodor's supervenience claim. It runs thus. Oscar has thoughts which have the property of being water thoughts in virtue of his causal relations to water (or his having a history in which certain significant causal interactions with water figure). The corresponding thoughts of Oscar2 are not water thoughts, for Oscar2 does not bear the appropriate causal relations to water; rather they are twater thoughts. In virtue of its etiology, the behaviour caused by Oscar's water thoughts is water behaviour, whereas that caused by Oscar2's twater thoughts is not water behaviour but, rather, twater behaviour. A consequence of this difference between their respective behavioural effects is that Oscar's water thoughts have the power to cause water behaviour, a power that his twins twater thoughts do not have; and Oscar2's twater thoughts have the power to cause twater behaviour, a power that his twins corresponding thoughts do not have. Given its concern with explaining behaviour under its intentional description, this

difference in causal powers is one that should be recognised by scientific psychology, hence Fodor's supervenience claim is mistaken.

It will also be helpful to distinguish a second, related version of the putative counterexample/ objection. It runs thus. In virtue of the causal connections he bears to water, the thoughts that Oscar expresses with sentences containing the word "water" are water thoughts. Thus Oscar has the power to think water thoughts. This is a causal power that Oscar2 does not have, as the thoughts that he expresses with sentences containing the word "water" are twater thoughts. What he has is the power to think twater thoughts. Thus the twins differ in their causal powers, and given that psychology is concerned with explaining behaviour by reference to its intentional causes, this is a difference in causal powers that should be recognised by scientific psychology.

In 'A Modal Argument for Narrow Content', Fodor responds to these putative counterexamples.®^ He begins by describing a schema which both cases fit, and naming it "schema S". Schema S is as follows. C l and C2 are a pair of causes, and El and E2 are their respective effects:

C l differs from C2 in that Cl has cause property CPI where C2 has cause property CP2.

El differs from E2 in that El has effect property EPl and E2 has effect property EP2.

The difference between Cl and C2 is responsible for the difference between El and E2 in the sense that, if Cl had had CP2 rather than CPI, then El would have had EP2 rather than EPl; and if C2 had had CPI rather than CP2, E2 would have had EPl rather than EP2. (1991, p. 9).

The first of the putative counterexamples fits schema S in this way: Cl is a thought of Oscar and C2 is a corresponding thought of his twin. CPI is the property of being a water thought and CP2 the

'A Modal Argument for Narrow Content' is a highly technical paper. Consequently, my discussion of it is also highly technical, especially by my standards. For some different, but equally technical, responses to Fodor's reasoning see Peacocke (1994), and Baker (1995).

property of being a twater thought. El and E2 are instances of behaviour of Oscar and his twin respectively. EPl is the property of being water behaviour and EP2 is the property of being twater behaviour.

And the second putative counterexample fits S in this way: C l is Oscar and C2 Oscar2. CPI is the property of being causally connected to water and CP2 is the property of being causally connected to twater. El and E2 are Oscar's and his twin's corresponding thoughts respectively. EPl is the property of being a water thought and EP2 is the property of being a twater thought.

Fodor argues that not every instance of schema S is a bona fide case of a divergence in causal powers. That is, not every instance of S is a case 'where the difference between having CPI and having CP2 is a difference in causal power in virtue of its responsibility for the difference between El and E2'. This raises the question of whether the putative counterexamples are bona fide cases. He formulates a condition that he thinks that any instance of schema S of a certain type (a type that the putative counterexamples belong to; see footnote 6) must satisfy if it is to be bona fide. He then argues that the putative counterexamples fail to satisfy this condition, and thus the threat that they pose to the supervenience claim evaporates.^^

The necessary condition that Fodor presents (a condition that he labels condition C) is essentially this: the difference between having CPI and having CP2 is a difference in causal power in virtue of its

It is important to get clear on the following point. In the case where an instance of S fails to meet the necessary condition, Fodor is not thereby commited to concluding that the causes in question agree in their causal powers. Rather, all he is committed to is rejecting the claim that C l has different causal powers than C2 in virtue of CPI's responsibility for El's having EPl rather than EP2 (or in virtue of CP2’s responsibility for E2's having EP2 rather than EPl). It may well be that CPI (or CP2) is responsible for some other property of El (or E2) in virtue of which Cl's causal powers diverge from those of C2. Or it might be that Cl (or C2) has some other property not shared by its counterpart which affects its causal powers. Indeed, argues Fodor, any two causes that differ in some contingent property will thereby diverge in their causal powers due to the possibility of constructing a machine for detecting that property. The cause that has the contingent property in question will have the power to cause a detector of that property to go into the positive state, a power which its counterpart (which doesn't have the property) will not have.

responsibility for the difference between El's having EPl and its having EP2 only when this difference between the effects is nonconceptually related to the difference between the causes. Thus if there is a conceptual relationship between having CPI (rather than CP2) and having effects that have EPl (rather than EP2) so that to

have EPl (rather than EP2) just is to be caused by something with