The problem of the soul

[Angrboda]

That's very reminiscent of Popper's Third World, which many see as a problem.  If there's a world where one kind of stuff interacts, and a second world where a different kind of stuff interacts, then there must be a third world where world one stuff and world two stuff are able to interact.  I tend to see the problems inherent in such a view arguing strongly for monism.  However, in a monist world, a lot of God stuff wouldn't happen.

Not every problem is a defeater though. As a common objection to dualism it is really and argument from ignorance and or incredulity. If the only positions we can reasonably hold are those without unresolved problems then we could not reasonably hold any positions.

It might also be a question of infinite regress or a mereological issue. I don't know. I hadn't considered your objection previously. I'm not sure it's necessarily so. I'll have to give it some thought.