While I've been excited about the harmony between science and how Witnesses understand biblical anthropology, one Witness friend with whom I shared these findings said I should exercise caution: he feels that only Jehovah knows how mentality actually comes about. I respect this friend greatly, but I could not help but wonder what else accounts for mental states, if we're purely physical and don't have souls. In any event, two possibilities seem viable for me at this time:
1) Mental states could supervene on brain states
2) Mental states are identical with brain states
By supervenience, I simply mean a form of "dependence" such that M (mental states) depends on B (brain states), which is another way of saying that differences in B constitute differences in M (and vice versa). Another term for supervenience is property dualism (e.g., contrasting the physical properties of a painting over against its microphysical properties).
As support for the idea that minds could turn out to be continuous with matter, Anthony Appiah writes:
"We have learned about the properties of matter by seeing what can be made of it: we know that it is the kind of thing that magnets can be made out of, because we have found magnetic substances; we know that it is the kind of thing bacteria can be made out of, because we have found bacteria. Why is it especially hard to accept that it is the kind of thing minds can be made out of? Indeed, since the one thing of which each of us surely has the most extensive direct experience is our own mind, shouldn’t we be puzzled, if we are puzzled by anything, by the nature of matter? How can it be, one might want to ask, that a world made of the sorts of things and governed by the sorts of laws that physicists now believe in should give rise to the astonishing range of experiences that each of us has every day?" (Thinking It Through, page 52).
But Kevin Vanhoozer does not want to reduce mental properties to physical properties. He believes we should maintain some type of distinction between the two. Either way, I believe that physical factors completely explain mental states. Jehovah God created us as completely physical beings.