Isn’t pantheism the same thing as atheism?

[Ferrocyanide]

Great post.  I think the mystics believe that free will means agency, and that agent (the soul) is outside of the material world and therefore not bound by it. 

In this scenario, the agency of the soul is either

A) not caused by anything else - it is a first order cause in and of itself, owing to its divine nature.
B) The agency is caused by some sort of "non-material" framework, and subject to the same 4 possibilities you mention above.  In other words, declaring the soul's agency to be non-material gains you nothing.

The problem with A) is that there is plenty of evidence that choices ARE correlated with the material nature of the brain.

If they want to believe that the soul is outside of this universe, we can explore that possibility.
1. Since the brain is the organ that controls the rest of the organs, this means that the soul has to interact with the brain.
2. The way to interact with atoms is to give some energy to them. So, energy is being transfer from the soul to the brain, from Universe A to Universe B. This is something that should be measurable.
3. The soul has to read the data inputs. It needs to read the visual input, the sound input, touch input, heat sensor, cold sensor and more.
I think this also means energy is being transfer from the soul to the brain.
4. We would have to believe that for some reason, a soul is being plugged into the brain somehow.
Whenever a fetus is being developed in Universe B, a soul needs to be develop in Universe A. At the right moment, a contact is made.
5. Are there other souls? A soul for the hand, a soul for the eyeball?
6. How does a human soul find the human fetus? What if it accidentally plugs into a cat fetus?
7. If there is a soul, it reduces the processing burden from the brain. Perhaps most of the brain is useless. Perhaps all brain functions can be transferred to the soul.
What’s the point of having the brain being connected to the spinal cord and having nerves? The soul should be able to connect directly to the entire body.