Technical issues regarding souls:
- As Kwayera mentioned, identical twins start off as a single zygote. Do two seperate souls simply occupy the one zygote at once? Does a single soul split into two? Does a second soul simply appear at the time of spliting?
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Split brain cases are troublesome for those arguing for a unitary immaterial mind/soul. In many documented cases the seperate hemispheres, after having the corpus collosum severed, exhibit contrary goals and aims, e.g. the right hand will try to pick a blue shirt out of the wardrobe while the left hand picks a green shirt, or one hand does up a zipper while the other hand undoes it. In other words the hemispheres seem to lack unity, as though there are now
two persons coinhabiting one body. I am unsure how this phenomenon can be explained with recourse to 'the soul'.
- Neurological syndromes due to focal damage are also problematic. E.g. it is possible to loose colour vision, or the ability to recognise faces, or the ability to acknowledge the 'left side of the world', or one's social inhibitions. Note, then, that
physical lesions can create major deficits in a person's experienced world. Essentially, all the things which seem to make a person a person, e.g. memories, beliefs, capacity for reason, temperament, moral conscience and so forth, seem to be susceptible to erasure by means of physical damage. Thus any theory of the soul which views such human capacities as
dependent on the soul needs to be able to explain how such physical lesions can entirely interupt these supposedly 'immaterial' capacities.