A comment from Keith Parsons, and a reply from Vallicella

Keith Parsons: Vic, I thought that I didn't really understand your view, and now I'm sure I understand even less than I thought I did. You say that mind is not(ordinary) matter, nor is it a Cartesian soul, but it is a tertium quid thatexits in space and, indeed, is found in the brain, but it has weird"soulish" properties such as the ability to exercise libertarian free will.

VR: I'm not dogmatic about what the nature of the soul. My main point is that there are a lot of varieties of dualism out there, and "Cartesianism" is only one of them. I haven't seen any good arguments that I know of for the claim that the soul doesn't occupy space, so I don't see why it couldn't. And some people define matter as "whatever occupies space." So on that definition of matter I'm a materialist, or at least I don't have any arguments on hand against materialism thus defined. (Maybe someone else has some). In William Hasker's The Emergent Self he mentions Cartesian dualism, Swinburne's version of dualism from The Evolution of the Soul, Eleonore Stump's Thomistic dualism, and his own emergent dualism, according to which the soul is generated by the brain like a magnetic field. I'd argue that even Cartesianism isn't nearly as silly as people like Dennett make it out to be, and there are other forms of dualism besides. In fact some positions that go by the name of materialism, such as the view of Lynne Rudder Baker, are in fact somewhat questionably materialist in my view.

Am I right so far? Now, by denying that mind is constituted of ordinary matter, I assume you mean that it is not constituted of quarks and leptons. But since mind interacts with ordinary matter, there must be an exchange of energy (mediated by photons, or other bosons, perhaps?), and I assume some sort of conservation laws apply (or not? Does mind create energy ex nihilo?).

VR: There seems to be no reason to suppose that the mind couldn't produce energy, since it is outside the ordinary system of causation, and the laws apply only within that system. On the other hand, that is a question I'm inclined to leave open.

If so, then it looks as though mind does obey some of the"ordinary" laws of matter. On the other hand, if there is no energy exchange between mind and matter, then it looks as though the interaction problem is just as intractable as it was for Descartes. Am I just being obtuse here, missing obvious points? Thanks for your patience.

Keith

As I said in my book, without putting some meat on the bones of the "problem of interaction," I think it's an overrated objection. On the face of things, anything could interact with anything. Theists already believe that the entire physical universe was created by a nonphysical being. So if non-physical/physical interaction is somehow impossible, then we've got a great argument for atheism that I don't hear atheists using very often. But if theism is true, why couldn't God create a physical universe with doors, so to speak.

Bill Vallicella addressed this on his blog, and I reproduce his comments here:

An Inconclusive Argument Against Dualist Interactionism

One can be a substance dualist in the philosophy of mind without being an interactionist. And one can be an interactionist without being a substance dualist. (Exercise for the reader: explain why both assertions are true.)

But suppose you are a latter-day Cartesian: you are both a substance dualist and an interactionist: you believe that mind and body are distinct (kinds of) substances and you also believe that some mental events cause physical events and some physical events cause mental events. You will be taxed by some with a supposedly insurmountable difficulty: how can there be mind-body and body-mind causation if mind and body are radically different kinds of substance?

There are benighted souls who think this objection is decisive against Cartesian dualism. They are mistaken.

To show that the objection is not decisive it suffices to set forth a theory of causation that would allow mental events to cause physical events (and vice versa) even if a mental event is construed as an irreducibly mental substance's instantiation at a time of a mental property and a physical event is construed as an irreducibly physical substance's instantiation at a time of a physical property.

Well, a regularity theory of causation would do the trick, would it not? Suppose we say that:
Event-token e1 causes event-token e2 if and only if (i) e1 temporally precedes e2, and (ii) e1 and e2 are tokens of event-types E1 and E2 respectively such that every tokening of E1 is followed by a tokening of E2.

On this Hume-inspired theory (sans the contiguity condition), causation is just regular succession. If this is the correct theory of causation, then there is nothing problematic about mental events causing physical events, and vice versa.

Of course, if you think that causation must involve the transfer of some physical quantity such as energy or momentum, then of course substance-dualist interactionism is out. But there is nothing in the very idea of substance-dualist interactionism to render it incoherent. It all depends on how causation is understood.

Suppose one adopted a counterfactual analysis along the lines of: c causes e =df had c not occurred, e would not have occurred. There is nothing here to rule out substance-dualist interactionism.