As we have seen from our reading of Descartes’ Meditations, there is at least one powerful argument for dualism. But the view also faces some problems.
There are strong reasons for dualists to be interactionist dualists. After all, we often think that there are causal relations between physical and mental events. We say that I walked to the coffee pot because of my desire for coffee, that I pulled by hand away because I felt a burning sensation, that I felt a burning sensation because the burner on the stove was hot. These kinds of examples indicate that, ordinarily, we often think that mental events are caused by physical events, and that physical events are caused by mental events.
One of the oldest problems for dualism is to explain how this can be so. As Kim asks,
“can we make sense of the idea that an immaterial soul can be in causal commerce with a material body, and that my immaterial mind can causally influence the physicochemical processes going on in my material brain?” (73)
Why this seems to be a difficult problem; the model of ‘billiard ball’ causation. The idea that causal connections between material and immaterial things is ‘inconceivable.’ Why this argument works as well against epiphenomenalist dualism as against interactionist dualism.
A reply on the part of the dualist: not all causation fits the billiard ball model. Perhaps causation is a basic and inexplicable relation, or perhaps, as Kim suggests, it can be analyzed as “constant conjunction.” Why this analysis would seem to make causal relations between material and immaterial things possible.
This response seems to show that the dualist’s problems explaining mental causation, even if they pose some difficult questions for dualism, don’t by themselves show that dualism is false. But there are two ways of strengthening this argument against dualism, which we will now consider.
The idea that every physical event has a physical cause. Why this seems plausible; if there are some events which have mental causes but not physical causes, why hasn’t science found any yet?
Why this argument works (if at all) against interactionist but not epiphenomenalist dualism. The idea of causal overdetermination.
Kim presents (in pp. 76-90 of the selection you read) a distinct argument against dualism, which tries to show that causation only makes sense if the causal relations in question hold between two things located in space. The problem he discusses for dualism is called the ‘pairing problem.’ A way into the pairing problem via the example of the two gun shots (pp. 78-9).
Here is one way to present the problem, in terms of mind-to-body causal interactions: imagine that you and I both, at the same time, have a desire to raise our hand. According to the dualist, these two desires are both non-physical events. Suppose that after having these desires, my hand goes up, and so does yours. Now, it seems very clear that my desire caused by hand to go up, and your desire caused your hand to go up; my desires lack direct control over your bodily movements, and vice versa. But the question is: how can the dualist explain this fact? Why, according to the dualist, is my desire the cause of my hand going up, rather than the cause of your hand going up? Recall the answer we gave to the analogous question in the case of the two gun shots: we can trace a continuous chain of causes, or continuous chain of spatial locations, which connects cause to effect. But this kind of answer seems not to be available to the dualist who thinks of mental phenomena like desires as located outside of space.
As Kim says, this is not really a problem about how immaterial things could be causally related to material things; it is a problem about how things which are not spatially located could enter into causal relations at all. Kim discusses (80-84) how to raise substantially the same ‘pairing problem’ for causal relations between immaterial souls. The moral, Kim thinks, is that
“In general, causal relations between physical objects or events appear to depend crucially on their spatiotemporal relations to each other.” (86)
If this is true, this rules out all major views which locate the mental outside of space and time -- whether the dualist is interactionist, epiphenomenalist, or parallelist. (It would leave untouched a view on which mental events never cause, or are caused by, anything, whether mental or physical.)
Two replies for the dualist: