The human mind could be penetrated by outside forces. Not only by God—who is sometimes depicted as going inside people, “probing their kidneys and heart” to find out what they’re really thinking—but by various sorts of “spirits.” Some of them were benign, but others were wicked spirits dispatched by Satan to take over. They were like bacteria; you couldn’t see them, but once they got inside of you they would take charge, making you think and do things against your will. So the Bible and other texts from the same period contain prayers specifically designed to ward off these evil spirits. That’s part of what I meant by semipermeable. You couldn’t stop God from entering your mind, but sometimes you could head off a wicked angel.
The idea of our minds being subject to causal influences from other non-physical entities has been 'on my mind' lately. The Christian doctrine of inspiration only tells us that some text has been inspired if and only if God 'moves' that person to write those words. What we mean by 'move' is left largely unanalyzed. The most plausible way to analyze the idea is by coming up with a causal thesis about God's thoughts causing the writers thoughts. How might this work?
As I commented the other day, God and human persons are souls/minds, concrete non-physical entities. God is omnipresent. Consequently, God is present at every location I am present. If concrete non-physical objects have causal powers, then God can directly cause the thoughts that take place in my mind and the sentences that express those thoughts.
Some philosophers argue that God cannot be literally at every location because if something is a soul, then it is not spatially located (Hoffman and Rosenkrantz, The Divine Attributes, 40). However, if I am a soul, I am located with my body. If my soul's being co-located with my body is coherent, then God being located at (or with) every location is coherent.
The view that a concrete non-physical entity cannot be spatially located also leads to the the mind-body interaction problem. Scantily, (i) A soul and a body interact only if they both have spacial location. (ii) If a soul does not have spacial location, then it cannot causally interact with the body. The problem arises if one accepts (ii) as a necessary truth. Again, there is good reason to reject (ii). God is plainly able to cause all sorts of physical events not least of which is the power to cause physical entities to come into existence. If this is possible, then mind-body interactions are possible and (ii) is false. So, if both God and human persons are non-physical concrete entities and spatially located, then God can cause happenings in the souls of human souls.
Of course, if one does not believe in the existence of the human soul, divine voices in the head cannot be the communication of an existent divine being. For Krugel's part, no human being is a soul. Rather, his sense of self is a 'fiction':
We tend to think that there is some central part of our brains that acts as a clearinghouse, processing all the outside sensory data that come into our heads via our eyes and ears and so forth and then deciding what to think and how to respond. The problem with this picture is that scientists cannot find anything physical in the brain that seems to act as the clearinghouse. In physiological terms, there is no “I myself”; such an entity seems to be a mental construct, something human beings evolved over millions of years but which has no independent, physical reality. This “I myself” is not, we believe, identical to our bodies or our brains—we have a body and a brain, but the possessor of these things is somehow conceived to be separate from them, some fictional owner, me. This, as far as most neuroscientists are concerned, is simply a mental construct. Science doesn’t need an “I myself” to explain what goes on in our brains, but apparently we do.
Consequently, Krugel argues that revelation (the divine voice) cannot be any more than a hallucination: "I like the definition of hallucination recently proposed by a neuropsychiatrist; it’s not something false, he wrote, but a “sensory experience which occurs in the absence of corresponding external stimulation of the relevant sensory organ.” This, I think, is what some biblical texts are talking about. The person thinks he’s seeing or hearing something, but it seems to work a little like a dream. "
Krugel's argument depends on the following premise: "Scientists cannot find anything physical in the brain" so, "there is no 'I myself'; such an entity seems to be a mental construct, something human beings evolved over millions of years but which has no independent, physical reality." It should be clear that a soul is not physical and so not discoverable through scientific observation. But one should not think that this entails it is not there. It simply does not follow from not being able to see something that it does not exist. Laws of logic, numbers, souls, propositions and any number of other entities are not observable since they are not physical. We would not, however, want to deny their existence. Of course, some do, and they talk about useful fictions in the same way Krugel talks about selves. The point is that one cannot assert the non-existence of some entity based on an assumption that everything is physical. This clearly begs the question.