This is a compelling and interesting study of Hermetic Protestantism in 17th century America through the figure of Johannes Kelpius, the “philosopher of the forest.” Theologically trained in Europe, Kelpius combined the medieval Book of Nature with biblical scripture as sources of religious authority in a syncretic project which took stock of environmental phenomena as evidence of the divine, especially during a period of climactic upheaval, the “little ice age,” and in a context of perceived decline in the sacrality to be found in institutional Christianity. Grieve-Carlson traces the esoteric currents influencing the developments represented by Kelpius, from Paracelsus’ use of the microcosm-macrocosm analogy, the cosmotheism of Johan Arndt, and the mysticism of Jacob Bohme. Through the lay Hermetic Protestantism of Kelpius, Francis Pastorius, and others, Grieve-Carlson complicates the narrative of Protestant-Enlightenment disenchantment, with these figures continuing to operate under these “elite constructs.” We learn about Kelpius’ wilderness retreat community at Wissahickon, their ecstatic and paranormal experiences such as telepathy and the sighting of luminous orbs, environmental and astronomical observations, as well as their practices of spiritual alchemy. Kelpius continued to have a sizable influence on post-Enlightenment America well into the 19th century.