Here is a question that I want to ask all my fellow naturalists, those who believe that only the natural exists. Why is it that there are no supernatural beings? Though it may be the case that none exist, is there a reason that none exist?
I believe there are several possible answers to this question, but I'd like to hear yours. Below are some possibilities I've thought of from my readings in philosophy:
1. Spirits are logically impossible. I think it's fairly well-established that consciousness is really nothing more than an emergent phenomenon from physical stuff. If that's what consciousness is, an emergent physical property, then no non-physical entity could have consciousness. Therefore there could be no mind without a body (a spirit). Richard Carrier has suspicions towards the logical possibility of spirits as well. He writes:
[I]f God has no location, then by definition there is no location at which God exists. And if there is no location at which God exists, then God exists nowhere, which entails that God does not exist. For the proposition "there is nowhere that God exists" is literally synonymous with "God does not exist." From any intelligible definition of being, in order for anything to exist, it must exist somewhere--even if that somewhere is everywhere, or some location other than space.
2. The concept of a spirit is meaningless. This is the position held by most verificationists. They believe that any proposition that does not refer to something that is at least possibly observable is meaningless. A spirit, as a non-physical entity (as defined by believers) means nothing. Of course a statement that means nothing could not rightly be said to be true. Though verificationism is now considered passe amongst most philosophers, it still has notable proponents such as Crispin Wright, Michael Martin, Kai Nielsen, Daniel Dennett, and others.
3. An Indexical understanding of "Real" coupled with conceptual problems with Dualism renders the spiritual unreal. David Kellogg Lewis proposed the idea that the word "real" is an indexical term, and things which we call real are merely those things that we actually or potentially can interact with. Things that are not real are things that we cannot even potentially interact with.
Now remember that as I jump to a seemingly unrelated subject. How can a spirit have any effect on the physical or interact with it in any way if the two have no point of contact (a spirit, being nonphysical, cannot possibly have a point of contact with the physical)? Maybe it can't.
From those two conjectures it follows that spirits cannot be real. To be "real" a spirit has to interact with the world around us in some way. But a spirit cannot interact with the world because there is no point of contact between the two.
Now, I don't take much of the above too seriously. These all seem to me like nothing more than hunches which stand every chance of being wrong. What are your answers?