Unlike the priest, who is a socially inducted and initiated member of a recognized religious organization, the shaman is one who, as a consequence of a completely personal psychological crisis, has gained a certain power of his or her own. Whereas the priest is concerned with integrating the individual into a firmly ordered and well-established social context, the shaman seeks the release of his or her own wild genius, where that may lead. Almost invariably, an overwhelming mental crisis is part of the vocational summons. Indeed, for the seeker of shamanic wisdom, it is a fine line between mystical initiation and psychological breakdown.
Yet, though this crisis may resemble a mental breakdown, it cannot be dismissed as one. For it is not a pathological but a normal event for the gifted mind in these societies, the realization and intuition of a level of spiritual depth that gives the world a sacred character. By following the solitary vision, the shaman breaks not with the other traditions of his tribe but with the comparatively trivial attitude toward the spirit realm that seems to satisfy the majority. In seeking this most difficult path, the shaman becomes a master of death and resurrection, of health and well-being.
-- Wade Davis, Shadows in the Sun