Abstract-Western psychotherapy and indigenous shamanic healing systems have both used psychoactive drugs or plants for healing and obtaining knowledge (called "diagnosis" or "divination" respectively). While there are superficial similarities between psychedelic-assisted psychotherapy and shamanic healing with hallucinogenic plants, there are profound differences in the underlying worldview and conceptions of reality. Four paradigms are reviewed: (1) psychedelic psychotherapy within the standard Western paradigm-here the drug is used to amplify and intensify the processes of internal self-analysis and self-understanding; (2) shamanic rituals of healing and divination, which involve primarily the shaman or healer taking the medicine in order to be able to "see" the causes of illness and know what kind of remedy to apply; (3) syncretic folk religious ceremonies, in which the focus seems to be a kind of community bonding and celebratory worship; and (4) the "hybrid shamanic therapeutic rituals," which incorporate some features of the first two traditions. There are two points in which the worldview of the shamanic and hybrid shamanic ceremonies differs radically from the accepted Western worldview: (1) the belief and assumption (really, perception) that there are multiple realities ("worlds") that can be explored in expanded states of consciousness; and (2) the belief that "spirits," the beings one encounters in dreams and visions, are just as real as the physical organism.
Keywords-hallucinogens, psychedelics, psychotherapy, shamanism, states of consciousnessBy way of introducing a comparative overview of the role of psychoactive drugs in psychological healing practices, a brief personal note might be permitted. As a psychologist, I have been involved in the field of consciousness studies, including altered states induced by drugs, plants and other means, for over 35 years. In the 1960s I worked at Harvard University with Timothy Leary and Richard Alpert, doing research on the possible therapeutic applications of psychedelic drugs, such as LSD and psilocybin (Leary, Metzner & Alpert 1964). During the 1970s the focus of my work shifted to the exploration of nondrug methods for the transformation of consciousness, such as those found in Eastern and Western traditions of yoga, meditation and alchemy (Metzner 1971). I also studied intensively the newer psychotherapeutic methods, many deriving from the work of pioneers such as Wilhelm Reich, that involve deep altered states induced by breathwork and bodywork. During the 1980s I came into contact with the work of Michael Harner , 1973), Joan Halifax (1982), Peter Furst (1976, 1972, Terence and Dennis McKenna (1975) and others, who have studied shamanic teachings and practices around the globe. These shamanic traditions involve non-ordinary states of consciousness induced by a variety of methods including ingesting hallucinogenic plants, but also drumming, fasting, wilderness vision questing, use of sweat