This is a Q & A blog post by our Visiting Scholar in Philosophy, William Lane Craig.
Big fan of your work Dr. Craig. My question is about what specifically ties the soul to the physical mind of a person. You’ve spoken in the past about how to be human is to be a body/soul composite, the spirit and the physical mechanisms of the universe working in tandem. The spirit or mind makes a willful decision, which acts upon the physical brain and performs physical actions in our reality.
What would you say ties the spirit or mind specifically to a single body or brain? Why can any human mind only act upon the physical body it’s been “assigned” to, for lack of a better term, and not some other collection of matter and particles?
Thank you, and God bless.
William Lane Craig’s Response
The problem you raise here, Jacob, is known in the philosophical literature as “the causal pairing problem.” As explained by Jaegwon Kim, the problem is how to explain the causal connection between a particular cause and a particular effect. In the case of physical substances, a causal connection between two events exists in virtue of their spatial relations, such as their spatial orientation and the path along which a causal chain between them lies. But assuming that the soul, being immaterial, is not spatially located, the causal connection between mental events and physical events is said to be inexplicable.
To illustrate the problem, we’re invited to imagine two souls, A and B, who are in the same mental state, for example, willing to lift the left arm of one’s body. If souls are not spatially located in their respective bodies, then there seems to be no explanation why A’s willing causes A’s arm to rise rather than B’s arm. One cannot say that the explanation lies in the fact that the body in question is A’s body, for the reason it is A’s body is because of A’s causal connection to it, so that such an explanation would be viciously circular. Dualism thus seems unable to explain the pairing of mental causes with their physical effects.
Kim’s causal pairing problem involves two claims: (1) causation requires pairing relations connecting a cause to its effect and (2) there are no such relations for minds because they are not spatially located. Both of these claims may be challenged.
With regard to (2), dualists who hold that souls do exist spatially in or throughout their bodies will be unfazed by Kim’s objection, since souls meet successfully the condition for being causally connected to their effects. The objection does remain relevant for dualist-interactionists who think that souls do not have spatial locations. But then the question becomes why we should think that only spatial relations can pair a cause with its effect. Prima facie this seems overly restrictive.
As for (1) the claim assumes that there must be some pairing relation that connects causes and their effects. Why think this? Kim does not say. Bailey, Rasmussen and Van Horn speculate, “We have a guess as to the underlining [sic] reasoning for thinking that there must be a pairing relation: pairing is required because the satisfaction of a generality condition is necessary for causation,” for example,
"(GC) Necessarily, if A and B share all of their qualitative properties, then A is no more qualified to count as the cause of C than B is."
Now Kim presupposes the truth of event causation, the view that causal relations hold only between events. But many dualist-interactionists embrace agent causation, the view that agents bring about effects by means of their actions. Bailey et al. contend that libertarian causal agency constitutes an exception to any generality condition like (GC) stipulating that qualitatively indistinguishable causes (like souls) cannot have different effects:
"It’s common for immaterialists about human persons to think that a person can enjoy agent causal powers that allow her to choose an action among a range of alternative actions. The idea is that no property instantiated prior to the time of the agent’s action fixes exactly which action she performs. . . . We think such immaterialists would happily grant in addition that indistinguishable agents would (or at least could) have the same causal capacities. Now consider a world in which two persons, Tim and Tom, are exactly similar in all respects. . . . Suppose that Tim and Tom each have the same two options available to them—to cause A or to refrain from causing A. If Tom happens to cause A while Tim refrains, then we have a situation in which GC fails. The reason is that Tom and Tim are indistinguishable and yet Tom counts as the cause of A, whereas Tim does not."
If libertarian free agents are causes of effects, then a soul could be the cause of a particular physical effect even though nothing distinguishes it qualitatively from another soul. Gregory Ganssle concludes that “Kim’s argument will work only against those versions of dualism that do not include an agent-causation view. Any position that involves this kind of agency will be immune from Kim’s argument.”
Intriguingly, since Kim’s argument is meant to hold for immaterial mental substances in general, there should be a theological version of it, which has been called the divine causal pairing problem. The challenge here is to explain, given God’s transcendence of space, why His mental events are causally connected with certain events in the physical world rather than others.
Fortunately, it’s difficult even to state the pairing problem for God’s causal activity in a way that does not appear a bit silly. For example, Ganssle writes, “If we need some relation to be present to link cause and effect, we will need a link between God’s willing and its effect. God wills that the Red Sea part. What makes it the case that this results in the parting of the Red Sea rather than the Mediterranean Sea?” It is bewildering how such a question can even be posed with respect to an omnipotent being Whose volitions are inevitably fulfilled. The will of such a being is indefectible—necessarily, it is linked to its effect. It is metaphysically impossible that God wills the parting of the Red Sea and the Mediterranean parts instead. So, while for some physical causes such as a rock’s hitting and breaking a window, “the spatiotemporal relation is sufficient to map the cause to a particular effect,” says Ganssle, “It is possible that, when God acts, it is the direct object of his volition that maps the cause to the intended effect.” Indeed, necessarily, whatever God wills shall be done, on Earth as it is in heaven.
 Jaegwon Kim, Physicalism, or Something Near Enough (Princeton: Princeton University Press, 2005), pp. 78–88.
 As Andrew M. Bailey, Joshua Rasmussen, and Luke Van Horn, “No pairing problem,” Philosophical Studies 154 (2011): 349-60, point out, Kim’s claim entails that the initial cosmological singularity featured in the standard Big Bang model could not possibly have been caused, given that the singularity is thought to represent the beginning of the existence of space.
 Plantinga protests, “Is it really clear that in any case of causation, there must be this factor X that pairs up event A with event B, that makes it the case that A is the cause of B? . . . why must we suppose that there is such a factor X? Consider the similar and oft-asked question about identity over time. What is it that makes it the case that object A at time t is identical with object B at some earlier time t*? . . . Many answers have been proposed, but none seems to work. And perhaps the right answer to the question is: there isn’t anything (anything else, so to speak) that makes it the case that A is identical with B. Identity doesn’t have to supervene on other properties. Couldn’t it be the same in the case of causation?” (Alvin Plantinga, “Materialism and Christian Belief,” in Persons: Human and Divine, ed. Peter van Inwagen and Dean Zimmerman [Oxford: Oxford University Press, 2007], p. 132).
 Bailey, Rasmussen, and Van Horn, “No pairing problem,” p. 354.
 Gregory E. Ganssle, “Divine Causation and the Pairing Problem,” in Divine Causation, ed. Gregory E. Ganssle (London: Routledge, 2022), p. 272.
 Ganssle, “Divine Causation and the Pairing Problem,” p. 269. Bailey, Rasmussen, and Van Horn, “No pairing problem,” p. 351, earlier noted this consequence of Kim’s objection.
 Ganssle, “Divine Causation and the Pairing Problem,” p. 274.
 As Mullins and Byrd remind us, “Classical Christian theology is . . . committed to God’s infallible causal power. God’s causal power is infallible in that, if God wills or causes some state of affairs x, then it is not possible for x to fail to obtain. This is sometimes captured by saying that if God intentionally acts to bring about some state of affairs, then that state of affairs is hypothetically necessary” (R.T. Mullins and Shannon Eugene Byrd, “Divine Simplicity and Modal Collapse: A Persistent Problem,” European Journal for Philosophy of Religion [forthcoming]). So, in answer to the question, “What is that factor X in the case of alleged divine causation?” Plantinga answers, “here there appears to be an easy answer. According to classical theism, it’s a necessary truth that whatever God wills, takes place. . . . So what is it that makes it the case that God’s intentions cause what they cause? To ask that question is like asking, ‘What is it that makes an equiangular triangle equilateral?’ The answer is (broadly) logical necessity; it’s necessary that whatever God wills comes to be, just as it’s necessary that every equiangular triangle be equilateral” (Plantinga, “Materialism and Christian Belief,” p. 133).
 Ganssle, “Divine Causation and the Pairing Problem,” p. 276.