RITES, TRANCES, HALLUCINOGENS

So much is anthropological observation; how it happens — what enables the shaman to achieve such a trance-like state — is another. Is it possible that the shaman is swept away by nothing other than his own passion? Or could it be that he is practising some kind of self-hypnosis? Or else, did they (also) use certain hallucinogenic plants to trigger, facilitate or accelerate the process?