On the face of it there doesn’t seem to be any issue with saying that mental activity most especially involves the brain.
It would be interesting to see what you think of how Jonathon Haidt deals with these questions in The Righteous Mind, a book I first heard of here. Of course good and evil exist but how do we envision them? I do not imagine evil as the evil eye of Sauron floating over Mordor nor do I think it is the sole property of one fallen angel. But I recognize situations and actions I would call evil and I think you’ll find there is wide spread agreement on what counts as one or the other.
I completely agree that the postumous experiences people claim to have had are mostly rubbish. That doesn’t mean that there can be no life after death, but I don’t see how anyone alive can possibly distinguish between a fantasy, dream or hallucination of such an experience and the real deal. As for the “supernatural” category, I suspect it is a place holder for phenomena people just don’t know what to make of; I wish it was not used as an explanation. To say something is supernatural in origin is just to say one doesn’t have the first clue about it. Nothing wrong with not knowing, but assigning something to the supernatural category for some seems to count as a proper explanation.
I don’t believe religion has anything specific enough to say about the nature of the soul to permit science to rule it out or in. I am agnostic but atheist in regard to a God understood as an entity outside ourselves which creates the entire cosmos and banishes death at will. Still I would say I have or am a soul. Sometimes it seems that rationally I am in charge of everything that is not my soul - including whether to allow that I have one at all. In my capacity as a rational being I do have free will. But I am not in charge of my soul and am not free to fashion my soul in any manner I choose. Rationally I can study the literature on what brings fulfillment but then it is my soul which will agree or disagree with what I read. My soul is the faculty by which I recognize what I need and most long for. Obviously I am not free rationally -nor by any other method- to decide what will fulfill that longing. That would be like my eyes being free to decide to start processing sound waves instead of light.