Leslie Stein interviewed twenty-nine mystics in order to understand the origin, progression, phasing, emotions, and individual variations of a mystical experience in order to make sense of how it should be addressed, the appropriate analytic attitude in the face of a mystery, the way to work with its content, and its psychological meaning. In doing so, he uncovered that there may be specific development markers that create a proclivity to be receptive to such an experience that has clinical significance for psychoanalysis.