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Merkur shows the existence of a more or less continuous tradition of psychoactive Western religion. Various separate threads of mystic techniques have sometimes come together to form an approach to the mystic altered state that is based on rational reflection, together with short-session use of visionary plants, rather than continuous long-term meditation.
This book associates a seemingly overlooked tradition of short-session meditation with the use of psychoactive, visionary plants. The use of psychoactives enables a more rationality-oriented approach and obviates the need to constantly meditate for long-term periods. This entheogen-using, short-session, rational form of mysticism is being increasingly recognized throughout Western history. Meditation, psychoactives, and rational thinking can be and historically have been brought together to augment each other.
Merkur helps entheogen researchers focus not only on revealing the presence of particular plants in mystic-state practices, but also on the traditions of using the plants in a shared religious framework and reflecting on the experiences produced by the visionary plants. The field of mysticism greatly needs such coverage of the important and challenging semi-secret tradition of not only entheogen use, but entheogen use combined with rational mysticism and short-session meditation.
I don't think Merkur is claiming that the mystics who combine these approaches claim that every aspect of mystic experiencing is entirely rationally explainable and conceptually tangible; the vision of the transcendent cosmic throne may still include a certain aspect that is, in a way, beyond the reach of complete, direct conceptualization.
Despite the seemingly entrenched assumptions that mysticism is inherently slow and laborious, drug-free, and non-rational, rational short-session meditation forms an effective alternative tradition or alternative view of what approach makes sense. This proposal contradicts the dominant assumptions about the techniques and conventions of mysticism: the assumption, perhaps misguided, that mysticism ideally should not use psychoactives, is not rationality-oriented, and must be conducted for extended, endlessly long meditation periods. In some semi-obscured traditions that are recently coming to light, these approaches have come together naturally and effectively.
This seems similar to the "lightning-bolt" short-path variety of Buddhist meditation technique as portrayed by James Arthur in Mushrooms and Mankind, which points out that Vajrayana was created by combining Tantric Buddhism and the native Bon shamanism of Tibet. The approach Merkur describes also seems equivalent to the evident visionary-state experiencing on tap in the Hellenistic mystery-religions, in which a person commonly undergoes a moderate number of limited-duration initiations to achieve spiritual purification and mental transformation, reshaping the mind's conception of the self by the encounter with transcendent experiencing.
Merkur, as psychologist, contrasts the experience of loss of the sense of personal freedom, which he portrays as being conventional mysticism, with a supposedly different experience of a psychoactive rational mysticism that involves panic attacks. However, I'd point out that the loss of the sense of being a metaphysically free agent is integral to a mystic-state panic attack. When the psychoactive perspective and self-sense, combined with rational analysis about our assumption of personal sovereign agency, suspends the sense of wielding metaphysically free power, that is the very cause and central vortex of the panic attack. The self-commanding part of the mind panics because the mind perceives the lack of metaphysical freedom and self-control, and sees the mind's vulnerable dependence on the mysterious uncontrollable arising of personal control-thoughts, like discovering that one's controllership is dependent on whatever happens to come up from an underground spring in a cave.
Merkur uses the Psychology interpretive paradigm, but that would be strengthened by a stronger Philosophy of Metaphysics background, including the philosophy of time and responsible control agents. The book doesn't really explain what the union with God experience, or the vision of the invisible transcendent controller on the cosmic throne above one's personal controllership level, would be like for a modern entheogenic rational mystic.
Merkur reveals the occasional conjunction of Western religion and psychoactives, and also a kind of rationality which I would call, with Ken Wilber, "vision-logic" or visionary rationality.
Fortunately, this book does not depend on identifying mystic sacraments as any one visionary plant. There is consensus in the field of the entheogen theory of religion that it is more important to identify scriptural allusions to psychoactives, and find how psychoactives were combined with meditation and visionary rationality, than to identify the main and minor entheogens used. The important point is to recognize the terms "sacrament" or "manna" as meaning visionary plants.
Subsections include The Necessity of Vision; Philo's Meditative Practices; Other Varieties of Ecstasy in Philo; The Contemplative Practice of Aristotle; Discursive Meditations in Islam; Bernard on Intellectualist Mysticism; Bernard on Trance-Based Mysticism; Death and Resurrection at Sinai; Maimonides on Meditation, and others.
Merkur provides essential coverage of primary religious experiencing at the origin and heart of Judeo-Christianity, providing highly valuable contributions that help to discovering the semi-suppressed tradition and history of entheogens in Western religion, as well as expanding our expectations about the nature of mystic experiencing. This book is a step toward covering entheogens casually as just one part, not especially novel or controversial, of a system of philosophy and religion.
This scholarly book is clear, organized, and presents a focused and well-supported thesis -- an excellent source for researchers to cite. Merkur is a clear writer who states where he's headed, states why he's covering subjects, and summarizes what he has established.
An invaluable, much needed, must-have contribution to research in the history of mysticism, theory of mystic-state insight and experiencing, and the entheogen theory of religion.