[js1138]

Point taken, but the problem of interaction between matter and non-matter is not my invention. I forget who first formally posed the problem, but its been around for centuries, and I don't think it's easily brushed aside.

I think the problem is even more interesting now that physics is dealing with "dark matter" and "dark energy" -- phenomena that defy traditional concepts of what is physical, and yet they exist.

Is anyone prepared to assert that dark matter and energy are non-physical? We know them only because of their subtle and elusive effects on the structure of the universe. How would any hypothetical non-physical substance that interacts with matter differ conceptually from these phenomena? If something interacts with matter, it will come under the perview of physics, regardless of whether it fits traditional concepts of matter.

[AndrewC]

Point taken, but the problem of interaction between matter and non-matter is not my invention.

I think you need to be a little careful with your terms. Matter/non-matter interaction is an everyday thing, I think that what you and many other people might mean is natural/supernatural interaction. That is a completely different question.