The comparative study of mysticism began in the mid-19th century, with the development of the modern meaning of the word, which had begun to be used as a substantive, with the classification of “mystics” in the 17th century. This differed from the traditional Greek Christian use of the adjective mystikos, to qualify rituals, scriptures, sacraments, and theology as “mystical” contexts of the human encounter with the Divine. This modern shift highlighted the personal experience of ultimate Reality, rather than the sociocultural context. Certain individuals claimed to encounter the Divine or spiritual realities more directly, separate from traditional mediums of religious experience. The study of this phenomenon tended in the early 20th century to focus on the psychology and the phenomenology of the personal experience, generally described as an altered state of consciousness with specific characteristics, processes, stages, effects, and stimulants. This emphasis on common features influenced the development of perennialist and traditionalist theorists, who saw evidence of the same experiential origin, fundamental principles, or epistemology among major world religions. Some essentialist views of mysticism argued that a pure consciousness-experience of undifferentiated unity or non-duality is the core feature of all mysticism, in contrast to other religious experiences. Reaction to these positions led to contextualist or constructivist views of mysticism, which presume the sociocultural character of mysticism. In its most extreme form, the contextualist perspective suggests that all mystical experiences among traditions are different, given diverse socio-religious categories that overdetermine the experience. In turn, some critical scholarship has proposed qualifications to contextualism within the context of a general acceptance of many of its tenets, even among many theorists with essentialist tendencies.
Up to the late 20th century, much scholarship in the area tended to downplay the sociocultural features of mysticism, emphasizing the psychological dynamics and an individual, disembodied, and radically transcendent ideal. This brought into question the relationship of morality to mystical experience and raised concerns about the status of entheogens—the use of psychoactive drugs in religious contexts. Interest in the comparative study of mysticism has also extended into the area of neuroscience, where researchers explore electro-chemical brain states associated with mystical experience, in proposing evidence of a mystical neurological substrate. But the essentialist/contextualist debate also moved the comparative study of mysticism beyond issues of epistemology, consciousness-states, ontology, and cognitive neuroscience, broadening the field to include other aspects of religious experience. Some studies have brought feminist concerns to bear on the discussion, insofar as women’s mysticism has been overshadowed and even repressed by men, and was seen to preclude legitimate experiential possibilities of a more embodied character. Related scholarship in history and depth psychology has focused creatively on the nature and significance of erotic elements of mysticism in comparative studies, with special attention to associated physical phenomena and their transformative dynamics. Similarly, more embodied features of comparative mysticism are the subject of transpersonal psychology, which draws on many humanistic disciplines and supports participatory approaches to the field. Transpersonal psychology remains open to claims that the ego can be transcended in movements into higher states of being that ideally involve personal/spiritual enhancement and integration. Also, some more recent proponents of new comparative theology advocate methods that engage the scholar in specific beliefs or practices of another tradition, and include subsequent clarification and elaboration of one’s own perspective in light of such comparative study, in exploring phenomena related to comparative mystical experience.