In my opinion, prerequisite to a 'soul' is the idea of substance dualism. That there is some kind of non-physical substance with no physical attributes that is separate from the physical energy/matter that we can see and interact with all the time. This makes things pretty difficult to begin with as by definition we are unable to attribute any 'physical' ideas to this substance: Can it move? Is it divisible? Are some bigger than others? etc. The moment we even attempt to attribute physical characteristics to it, such as by attributing size here:
I agree because we exist in a physical universe, we will want to describe physical attributes to the non-physical.
Even the term "substance" is misleading in that sense. Can the soul "move", I would say yes, it can move through the physical space. Look at the nde, the people with this experience describe the soul above the body watching the scene, sometimes watching loved ones, etc..,
Divisible; can one soul occupy multiple bodies? Maybe... Can one battery power multiple lights? I couldn't give a solid answer here though.
Bigger / smaller; I think that's the wrong question. Containing more or less energy is probably the better question, some people are narcissistic and small minded, and there are mother Teresa types who devote their lives to the betterment of others... So, ya, some may have more energy, more developed, different emotional focus.
we are attributing physical characteristics to it, and suddenly it's no longer a non-physical substance. If it's no longer a non-physical substance then surely it becomes tangible and measurable, which begs the question why have we never been able to interact with, measure or produce any evidence of it??
I wasn't describing physical attributes, but more like "processing power".
The only way to escape this issue is to concede that it is a completely non-physical substance, that 'lies beyond science' and the physical plane, in which case its entire existence is predicated on the fact that it defies investigation, which is incredibly fishy. As Ceist's video above demonstrates, almost all previous thought functions of the soul have been replaced by naturalistic processes in the brain, and the concept of a soul is now largely an emotional crutch.
Not substance, energy, maybe energy field would be better... It does not lie beyond science, though it is nearly impossible to study an energy field that is intelligent and not necessarily interested in being studied, at least in the sense of in a laboratory detected by equipment.
I would note, that with all of our sciences combined, can only explain about 3% of the composition of the universe... Darkmatter, dark energy, etc... Completely defies our capacity to explain. Even a universally applicable definition of gravity defies science (though we have an explanation that is useful enough for our purposes)
Yes, the processes of the brain have been described quite accurately... But it's more of an interface between the body and the soul.