Jaegwon Kim’s essay “Lonely Souls: Causality and Substance Dualism” comes from a philosopher who operates out of the physicalist tradition. Unlike some in that tradition, however, he has been very serious about pressing difficulties for otherwise popular forms of physicalism in the area of mental causation. In this paper he presents some problems for dualism in the area of mental causation. He reconsiders the familiar objection to Descartes’ dualism that dualism is untenable because we cannot see how something nonphysical can interact with something physical. As Kim points out, this is often presented with no or almost no supporting argumentation. However, Kim does supply some argumentation to put some meat on the bones of the familiar objection, by generating what he calls the pairing problem.
Kim maintains that a spatial framework is necessary for the existence of a causal relationship amongst objects. If two rifles are fired and two people are killed, what criteria would lead us to correctly pair the causes and effects? The answer, says Kim, is the spatial relationships between deadly bullets and the victims. Kim also points out that lack of a spatial relation between a suspect and the victim is often sufficient to ground an alibi in a murder case. But since souls are not spatial, spatial pairing relationships between souls and matter cannot exist. Kim considers the possibility that souls have spatial locations, but he finds some difficulties with that idea as well, but he thinks this is problematic as well. We need to locate souls at a particular point in space, and claims that it would beg the question to locate the souls in the brain. Second, he argues that to locate souls in space would require that not more than one soul could occupy a location in space, that is, something like the impenetrability of matter would have to obtain. But he asks, if this is so, “why aren’t such souls just material objects, albeit of a very special, and strange kind?” And he thinks the soul found in a geometrical point could not have a structure capable of accounting for the rich mental life that humans have. Finally, he is suspicious of any solutions to the problem dictated by “dualist commitments.” He says “We shouldn’t do philosophy by first deciding what conclusions we want to prove, and then posit convenient entities and premises to get us where we want to go.”
First of all, it needs to be made clear just what it is for something to be a material thing. The book makes it evident that the concept of “materiality” and “matter” need to be made clearer than they are. This is especially imperative for Christians who want to go as far as possible in accommodating their faith to “materialism.” Orthodox materialism is a corollary of philosophical naturalism, and is typically committed to at least this: that the physical order is causally closed, and that whatever other states exist supervene on the physical; that is, there cannot be a difference without a physical difference. But what is more, physicalism is committed to the idea that the physical order is mechanistic, that is, purposive explanations cannot be basic-level explanations at the physical level. If the material is defined in this way, then it seems to me that something could have a spatial location, and it could also possess impenetrability, and still not be material in the orthodox sense. It could still be the case that the mental is sui generis and fundamental, and one of Foster’s dualist theses would still be true.