I can see there has been much dialogue/posts since then, and I want to take the time to read them more carefully....Don't want to sound like I'm picking on Wood so anyone can answer this.
How can you have confidence the Shaman's report of the otherside of the glacier is real and not some mere hallucination brought on by an altered state of consiousness? Much like the so-called after-life experience of the clinically dead who "go down the tunnel to the light" may be a manifestation of the oxygen starved brain, according to some researchers. The shaman "reality" of the spirit world may not be reality at all rather an elaborate fantasy (interpretation) which emerges from a physical part of our brain wiring which has long since gone dormant in ordinary humans.
....but regarding your post above from this AM, .... don't feel picked on.....but do find it curious that science and the Shamanic tradition is/can be seen as antithetical. Despite that we elect leaders on this side of the pond that can't or won't, surely the rest of us can hold two seemingly contradictory thoughts at the same time....if not only for the sport of it.
It was the very serious science of comparative anthropology in the hands of the emminent Harvard Scholar Mircea Eliade that connected the dots of world shamanic traditions. Seeing the practice/tradition as being essentially the same whether chasing reindeer, iguanas or saber tooth tigers. Again, the same serious science has the mega drug companys sending young hardy ethnologists into the jungle to pick the brains of the last living shamans as to their unique plant knowledge so bucks can be made if not a life or two enhanced or saved.
As to:
How can you have confidence the Shaman's report of the otherside of the glacier is real and not some mere hallucination brought on by an altered state of consiousness?
Like anything else it is rational to appraise the efficacy of the tradition and practitioner,....diplomas on the wall, recommendations from those you trust, effect on your own life, etc.
If I can quote Ishtar:
I'm thinking that the I Ching is undisputably the oldest book on the planet, if you include those inscribed heat cracked turtle shells. It is, to this day, a very accessable membrane between worlds unseen and ours, as how to proceed in Ordinary Reality in the spirit/model of the "superior man". If you are game, this could be a non threatening way to "dabble" in the Shamanic.The only way to really find out about what shamanism really is, is to try it. It’s an experiential process. It’s not a set of beliefs or a dogma or god you have to believe in and worship on Sundays
I've been using it for 40 years, it has helped me navigate the politics of graduate school, buisiness, investments as well as steer me towards my lovely mate. No need to pay any attention to my own experience... but you might want to take in into consideration the billions of Chinese who have sworn by it for the last (ducumented) 2500yrs.