If we have a soul...
And that is one big gigantic if.
But, for the sake of discussion, if we do have a soul, then there must be some sort of mechanism for information to flow from the brain to the soul, and from the soul to the brain.
The question is, what would that mechanism be, and how would we test it?
The way I see it is this (note - massive speculation follows): If there is a reality outside the physical reality, then it seems like this reality would be a subset of the outer reality. Basically, the fabric of spacetime, within which our reality is defined, would be contained within the outer reality. In order to find evidence of the outer reality affecting this reality (beyond the big bang) we need to look for events that have no apparent cause. Perhaps a possible area to look for such events would be apprently random quantum events, such as the spontaneous appearance of particle/antiparticle pairs.
If a quantum event were to pass information to the brain, it would need to either affect the firing of neurons, or the chemical structure of RNA and neurotransmitters.
For the sake of discussion, let's call any flow of information from the soul to the brain a spiritual event. If a spiritual event occurs, then it would cause neurons to fire, or a change in certain chemical components of the brain. It seems that either of these processes would result in electrons being forced into a higher state, then going back to a lower state, thus causing the release of a photon (any physics experts please feel free to correct me if I get some basic physics wrong). Thus, one way to look for evidence of a spiritual event would be to try to detect extra photon emission from the brain during a period when a spiritual event would be expected.
In pubmed I came upon one study claiming to detect photon emission during a laying-on of hands ritual, which I guess would be related to this idea. I frankly doubt the reliability of such a study, but it is a start. Here is the link for the abstract:
http://www.ncbi.nlm.nih.gov/entrez/q...883&query_hl=1
My question is this, in what other places, or with what methods, would we look for evidence to detect a flow of information from the soul to the brain. Or, more generally, how would we detect any influence of the outer reality on this reality.
If one were to examine all possible routes of information transfer, and find zero evidence of the occurrence of the expected events, then that would be evidence in favor of the argument that this reality is all there is.