Scholarly approaches to mysticism include typologies of mysticism and the explanation of mystical states. Since the 19th century, mystical experience has evolved as a distinctive concept. It is closely related to "mysticism" but lays sole emphasis on the experiential aspect, be it spontaneous or induced by human behavior, whereas mysticism encompasses a broad range of practices aiming at a transformation of the person, not just inducing mystical experiences. There is a longstanding discussion on the nature of so-called "introvertive mysticism." Perennialists regard this kind of mysticism to be universal. A popular variant of perennialism sees various mystical traditions as pointing to one universal transcendental reality, for which those experiences offer the proof. The perennial position is "largely dismissed by scholars" but "has lost none of its popularity". Instead, a constructionist approach became dominant during the 1970s, which states that mystical experiences are mediated by pre-existing frames of reference, while the attribution approach focuses on the (religious) meaning that is attributed to specific events. Some neurological research has attempted to identify which areas in the brain are involved in so-called "mystical experience" and the temporal lobe is often claimed to play a significant role, likely attributable to claims made in Vilayanur Ramachandran's 1998 book, Phantoms in the Brain. In mystical and contemplative traditions, mystical experiences are not a goal in themselves, but part of a larger path of self-transformation. Typologies of mysticism Early studies Lay scholars of the nineteenth and twentieth centuries began their studies on the historical and psychological descriptive analysis of the mystical experience, by investigating examples and categorizing it into types. Early notable examples include William James in "The Varieties of Religious Experience" (1902); the study of the term "cosmic consciousness" by Edward Carpenter (1892) and psychiatrist Richard Bucke (in his book Cosmic Consciousness, 1901); the definition of "oceanic feeling" by Romain Rolland (1927) and its study by Freud; Rudolf Otto's description of the "numinous" (1917) and its studies by Jung; Friedrich von Hügel in The Mystical Element of Religion (1908); Evelyn Underhill in her work Mysticism (1911); Aldous Huxley in The Perennial Philosophy (1945). R. C. Zaehner – natural and religious mysticism R. C. Zaehner distinguishes between three fundamental types of mysticism, namely theistic, monistic, and panenhenic ("all-in-one") or natural mysticism. The theistic category includes most forms of Jewish, Christian and Islamic mysticism and occasional Hindu examples such as Ramanuja and the Bhagavad Gita. The monistic type,