Other States of Consciousness

Many non-western cultures have a member of their society who is considered to be a healer.  Often times this medicine man may be considered a shaman, meaning that he has the ability to enter into an altered state of consciousness and become part of an alternate reality where he can gain power, and knowledge.  The shaman may enter into  this state of consciousness in order to help others or to further his understanding of the sub-reality.  This state is sometimes referred to as "ecstasy".  Some shamans believe there are distinct levels of consciousness and the shamanic state of consciousness is somewhere near the bottom while our ordinary every-day reality is at the top.  the states in between consist of various stages in which sensory perceptions change.  Sometimes Shamans use different herbal substances are used to induce these experiences.  Some of these drugs are extremely potent.  One, known as ayahuasca, is a  powerful hallucinegen which quite possibly would cause many of us to go insane upon its consumption.  Under its influnce the shaman is able to communicate with spirits of another reality.  It is believed that these spirits are linked to people, animals, and even plants that exist in our ordinary reality.  My question then is this: Do you agree with any of these non-westeren beliefs concerning alternate realities and the use of certain drugs to enter into them or do you  think that many of these ideas are quite rediculous and absurd?  Do you have mixed feelings?