The Argument from Mental Causation
The Argument from Mental Causation
The third of my arguments is the Argument from Mental Causation. If naturalism is true, even if there are propositional states like beliefs, then these states have to be epiphenomenal, without a causal role. Now careful reflection on rational inference, if we think about it, commits us to the idea that one mental event causes another mental event in virtue of its propositional content.
Now if events are caused in accordance with physical law, they cause one another in virtue of being a particular type of event. A ball breaks a window in
virtue of being the weight, density, and shape that it is in relation to the physical structure of the window. Even if it is the baseball that Luis Gonzalez hit against Mariano Rivera that won the 2001 World Series, its being that ball has nothing to do with whether or not it can break the window now.
So let us suppose that brain state A, which is token identical to the thought that all men are mortal, and brain state B, which is token identical to the thought that Socrates is a man, together cause the belief that Socrates is mortal. It isn’t enough for rational inference that these events be those beliefs, it is also necessary that the causal transaction be in virtue of the content of those thoughts. If anything not in space and time makes these thoughts the thoughts that they are, and if naturalism is true, then the propositional content is irrelevant to the causal transaction that produces the conclusion, and we do not have a case of rational inference. In rational inference, as Lewis puts it, one thought causes another thought not by being, but by being seen to be, the ground for it. But causal transactions in the brain occur in virtue of the brain’s being in a particular type of state that is relevant to physical causal transactions. Only that property of the brain can be relevant to what the brain does, according to a naturalistic account of causation.
What this means is that those forms of substance materialism that accept property dualism invariably render the “mental” properties epiphenomenal. If the physical properties are sufficient to produce the physical effect, then the mental properties are irrelevant unless they really are physical properties “writ large,” so to speak. And mental states that are epiphenomenal cannot participate in rational inference.
Carrier’s account of mental causation clearly presupposes a reductive, rather than a nonreductive, materialism. He writes:
Every meaningful proposition is the content or output of a virtual model (or rather: actual propositions, of actual models; potential propositions, of potential models). Propositions are formulated in a language as an aid to computation, but when they are not formulated, they merely define the content of a nonlinguistic computation of a virtual model. In either case, a brain computes degrees of confidence in any given proposition, by running its corresponding virtual model and comparing it and its output with observational data, or the output of other computations. 15
Now if Carrier had successfully provided a physicalist reduction of intentional states, so that the intentional characteristics could be in causal connection, then perhaps this part of his argument would work. But since the reduction seems to be unsuccessful, the proposed solution to the problem of mental causation must also be a failure.
But more than that, here again we find Carrier explaining one kind of mental activity in terms of another mental activity and then explaining it “naturalistically” by saying “the brain” does it. My argument is, first and foremost, that something exists whose activities are to be fundamentally explained in intentional and teleological terms. In order for talk about the brain to play its proper role in a physicalistic (non-intentional and non-teleological in the final analysis) analysis of mental events, we have to be sure that we are describing a brain that is mechanistic and part of a causally closed physical world. What I wrote in response to Keith Parsons in Philosophia Christi applies here as well: (Parsons had argued that we could simply take all the characteristics that I wanted to attribute to the non-physical mind and attribute them to the brain).
But we should be careful of exactly what is meant by the term “brain.” The “brain” is supposed to be “physical,” and we also have to be careful about what we mean by “physical.” If by physical we mean that it occupies space, then there is nothing in my argument that suggests that I need to deny this possibility. I would just prefer to cal the part of the brain that does not function mechanistically the soul, since, as I understand it, there is more packed into the notion of the physical than just the occupation of space. If on the other hand, for something to be physical (hence part of the brain) it has to function mechanistically, that is, intentional an teleological considerations cannot be basic explanations for the activity of the brain, then Parsons’ suggestion (and Carrier’s as well-VR) is incoherent.16
I think that a many people fail to see the difficulties posed by the arguments from reason because they think they can just engage in some brain-talk (well, the brain does this, the brain does that, etc.) and call that good. I call that the Mr. Brain fallacy. The question should always be, “If we view the brain as a mechanistic system in the full sense, does it make sense to attribute this characteristic to the brain?” Otherwise, I am inclined to say in response, “Interesting fellow Mr. Brain. Remarkable what he can do.” Using brain-talk doesn’t mean that the work of physicalistic analysis has really been done.
15 Carrier, op. cit.
16 Victor Reppert, Causal Closure, Mechanism, and Rational Inference (Philosophia Christi, Series 2, vol. 3. no. 2)