The author describes three successive scholarly views of mystical experience. An earlier generation saw mysticism as a single, pure, contentless awareness of ultimate reality, forming the basis for a perennial philosophy. Later scholars distinguished several recurring types of mystical experience across traditions. Most recently, the "diversity view" emphasizes differences so strongly that it denies any common experience or perennial philosophy, stemming from a growing awareness that experience is deeply mediated and organized by one's belief system.
The classic approach to mysticism emphasizes its unity, pointing to striking parallels in the language used by mystics from different cultures who were unknown to each other. It concludes that they describe the same experience, presenting mysticism as involving a state of consciousness found in virtually all religions, recognizably the same in each, and acknowledged as the highest goal of the religious quest.