I have always struggled with the concepts of soul and spirit. I am a mind program running in a meat computer, powered by burning sugar.
I watched a friend's brain degrade during the first minutes of a stroke, alerted those around me, and saw it come back to full capacity after we quickly got her to a hospital. I have seen several people suffer seizures, and have seen the brain reboot itself slowly afterward. I ached inside when my grandmother, a world traveler, a violist, a researcher, turned into that woman who could not speak, who yelled in the afternoons about how awful it all was, and watched nothing but Law & Order in the evenings. I have seen brains broken.
But I believe the brain only holds the mind, that the mind's functions are the essence of a person. Personality and character, hopes and fears, wit and wisdom, these are merely contained by neurons, as words convey meaning and significance using only 26 letters (in English).
I believe that sapience is the "image of God" and that He cares enough to ensure nobody will be lost to oblivion once they have begun to exist. I even believe His free offer of salvation is extended to sapient AI (self-experiencing, rational, tool-and-language-using), if we manage to make such a thing.
(In Christian theology, salvation from oblivion and salvation from Hell are two entirely different things. Everyone is saved from oblivion due to being "in the image of God", but are then judged for every bit of entropy they brought into a once-perfect creation. By accepting Jesus's sacrifice in their place, a person asks for their character to be absolved from harm they have done to others. In addition, their character is supernaturally enhanced by the Holy Spirit dwelling in their heart (like a Trill symbiote), to be motivated by love for all people from then onward. But, also like a Trill bonded pair, the person can still choose to hurt and to hate, hence godhatesfags.com.)
(My thoughts on this subject have been heavily influenced by an Isaac Asimov story about a man who finds himself mentally resurrected by a god-like being who wishes only to die.)