Temporal lobe epilepsy & religious experience.

[The Grand Nudger]

William James discusses this sort of thing at length in Varieties.

James has an interesting reply to the question of mystical experiences being caused by epilepsy or abnormal brain activity. His answer is, "so what?" He urges us to judge the content of the experience rather than the cause. If you have a high fever and see a bunch of pink elephants dance around on your wall paper, the content of the experience is bankrupt of meaning. Go ahead and ignore it.

However, if the same fever causes some cosmic vision that has meaning to you, why not take that experience seriously? Especially if it empowers you in some way. James is a pragmatist, so that sort of thing is his main focus. "How useful is such an experience to one who has it?"

Plenty of objections to this approach, of course, but I am fascinated by James's take on things.

 Neopaganism is all in on this approach, and shamanism may be it's oldest advocate.  It's the value of the religious ideation that explains a persons conformative behaviors, not the truth of the contents as described.  I think that's perfectly workable when it comes to how a person looks at or approaches life in general - but at some point, the contents of the vision hit the brick wall of reality - as no one is drum circling dinner onto their plates, or drawing down the goddess to hold up a wobbly table - but we do organize our families and our communities in a collective normative effort to that effect.

You're giving short shrift to seeing pink elephants dancing on wallpaper, btw, man. Hallucinogenic rituals are ubiquitous to human culture. We knew about drugs and fevers and exhaustion before we knew about wheels. As for inducement, a nun in lifelong prayer and a shaman in a lodge and a ghost spirit-fingering our brain and a researcher with drugs or a cattle prod are all equivalently engaged. It would only be those states that occurred without such active administration by an intentional agent that could qualify as natural, as opposed to artificial. We're basically swirling the drain of how people (or gods) have figured out ways to take advantage of abnormal brain states generally caused by damage or malfunction, in nature.