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William F. Vallicella's discussion on:

C.J. Ducasse
On Mind-Body Interaction, Conservation of Energy, and the Closure of the Physical Domain

    Discussion from http://maverickphilosopher.powerblogs.com/posts/1131235741.shtml

A standard objection to interactionist substance dualism is that mind-body interaction violates the principle of the conservation of energy. In my opinion, anyone who finds this objection decisive is not thinking very hard. Let's consider what C. J. Ducasse once said on the topic:

. . . The objection to interactionism that causation, in either direction, as between psychical [mental] and physical events is precluded by the principle of the conservation of energy (or of energy-matter) is invalid for several reasons.

A. One reason is that the conservation which that principle asserts is not something known to be true without exception but is . . . only a defining-postulate of the notion of a wholly closed physical world, so that the question whether psycho-physical or physico-psychical causation ever occurs is (but in different words) the question whether the physical world is wholly closed. And that question is not answered by dignifying as a "principle" the assumption that the physical world is wholly closed.

B. Anyway, as C. D. Broad has pointed out, it might be the case that whenever a given amount of energy vanishes from, or emerges in, the physical world at one place, then an equal amount of energy respectively emerges in, or vanishes from that world at another place.

C. And thirdly, if "energy" is meant to designate something experimentally measurable, then "energy" is defined in terms of causality, not causality in terms of transfer of energy. That is, it is not known that all causation, or, in particular, causation as between psychical and physical events, involves transfer of energy. (Curt Ducasse, "In Defense of Dualism" in Sidney Hook, ed., Dimensions of Mind, Collier 1961, pp. 88-89)

I will now proceed seriatim through these points, supplying my own interpretation of them.

Ad (A). Any physicalist worth his salt will uphold the causal closure of the physical domain. That is just part (though not the whole) of what it means to be a physicalist. Borrowing from Jaegwon Kim, the principle may be stated thusly: Any physical event that has a cause at time t, has a physical cause at t. You QM enthusiasts out there will please note that this does not imply that every physical event has a cause. Note also that Kim's formulation seems to allow for irreducibly mental events as causes of physical events. But if a physical event e is a sufficient cause of a physical event f, then any mental cause m of f will just be epiphenomenally along for the ride, if you catch my drift. In other words, m won't do any work.

Adding to Kim's formulation the notion that physical causes are sufficient for their physical effects yields a robust notion of causal closure. Robustly understood, the causal closure of the physical domain amounts to the thesis that all the causal work that gets done in the physical domain is done by physical events; if there are any irreducibly mental events, they don't do any work in the physical domain.

Ducasse's first argument, then, may be understood as follows. Appeal to conservation of energy is equivalent to appeal to causal closure of the physical. But one who objects to interactionist dualism on this basis begs the question against it by assuming the truth of a principle (causal closure) that immediately entails the falsity of interactionism.

The objection from conservation/closure is therefore not decisive against the interactionist. It would be decisive if the closure principle were known to be true. But that would be tantamount to knowing that physicalism is true. But we don't know it to be true. Of course, physical science proceeds by searching for physical causes. That is the kind of game it plays. Its procedure is methodologically naturalistic. But there is a logical gap between methodological and substantive naturalism.

Ad (B). I don't find Ducasse's second point all that impressive. Assume conservation of energy. Then, if causation involves transfer of energy, and some mental events are causally efficacious in the physical domain, then energy must enter the physical domain at some point, call it the locus of interaction. Does this violate conservation of energy? Only if it is assumed that energy does not vanish at some other point. Since this is logically possible, the objection is not decisive. In other words, there could be a net conservation of energy or matter-energy in a system in which energy arose and vanished in different places.

Ad (C). Assume the causal closure of the physical domain. One could still be an interactionist dualist by denying that mental-physical causation involves transfer of a physical magnitude such as energy. Of course, if we know that every instance of causation is an instance of energy transfer, then of course we know (via some simple inferences) that mental-physical causation is impossible. But we don't know this. Therefore, to object to interactionism on the ground that all cauasation involves energy transfer is to beg the question against the interactionist.

Note the difference between the first and third objections. The first objection begs the question against the interactionist by assuming that it is known that the physical domain is causally closed. The third objection begs the question by assuming that it is known that causation always involves energy transfer.

It looks like we ought to distingish between the interactionist who accepts a transfer theory of causation but rejects causal closure, and the interactionist who accepts causal closure but rejects a transfer theory of causation.

Ducasse also alludes to the following point. Isn't transfer itself a causal notion? How then can causation be analyzed in terms of transfer? Even if every instance of causation were an instance of energy transfer, that would not entail that causation consists in energy transfer. But this is a subtle point best reserved for a separate post.


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