John of Rupescissa (born c.1310) is known both for his writings on the apocalypse and for his alchemical works. Prophecy, Alchemy, and the End of Time reunites these two aspects of his writings, which have previously been studied separately. Leah DeVun's analytical investigation exposes the tendency of modern scholarship to divide the disciplines of ‘religion’ and ‘science’ in the study of history. She demonstrates that medieval thinkers were not constrained by such boundaries, and that Rupescissa sought enlightenment from a diverse range of sources including religious texts, natural philosophy and alchemy. These aspects of Rupescissa's learning were inherently connected and inspired him to formulate new ideas. In his prophetic texts he was the first writer to argue that humankind could defeat the coming Antichrist through its own agency and live on earth in the peace that followed. In alchemy, he developed the quintessence, an alcohol-based medicine that the human race could use as a tool to defeat the Antichrist. These advancements are considered as innovations in the history of religion and science respectively. Yet DeVun shows that Rupescissa's ideas were not developed from any radical approach, but through a multidisciplinary reading of well-established texts. DeVun confidently proves that to understand wholly the thought of Rupescissa, his prophetic and alchemical works must be read together. Her coherent and eloquent discussion demonstrates how such an interdisciplinary approach can be successfully achieved.

The book focuses upon three texts by Rupescissa: one relating to the apocalypse entitled Liber ostensor quod adesse festinant tempora and two alchemical works, the Liber lucis and De consideratione quinte essentie omnium rerum. DeVun's approach is to identify Rupescissa's sources and influences in order to explain how he was able to reconcile his apocalyptic ideas with alchemical theory. She begins with a study of his interpretation of the apocalypse, situating his ideas within the context of the history of the Franciscan order (of which he was a member) and demonstrating the influence of key patristic and apocalyptic texts including the writings of Joachim of Fiore. From this foundation she interweaves a discussion of alchemy. Here too Rupescissa was influenced by traditional and popular writings, including texts attributed to Roger Bacon, Arnold of Villanova and Ramon Llull.

DeVun deftly demonstrates how Rupescissa expressed his apocalyptic vision in his alchemical texts. She highlights the use of apocalyptic language in the texts, and convincingly argues that the alchemical imagery used in the works had a profound symbolic meaning. Rupescissa's conception of the quintessence also had religious significance. His quintessence was closely related to Aristotle's celestial fifth element. Yet while Aristotle considered heaven and earth to be wholly separate entities made up of contrasting (incorruptible and corruptible) matter, Rupescissa believed that a piece of the heavenly fifth element could enter the earthly sphere and in the form of a medicine could make humankind incorruptible. This idea developed new meaning for man's relationship with God and Nature. For Rupescissa, man could learn the secrets of alchemy through the divine will of God. Nature was a book to be read for clues and interpreted like the scripture. DeVun argues that Rupescissa formulated a positive apocalyptic vision. His writings provided hope, indicating that humans can arm themselves to resist the coming Antichrist.

Rupescissa's quintessence is considered by many scholars as an innovation in alchemy. It has been indicated as the forerunner to modern medical chemistry, particularly for its influence upon key figures such as Paracelsus. Yet DeVun clearly demonstrates that while Rupescissa is considered an ‘innovator’ in the field of the history of science, his original ideas were developed from long-standing written traditions in alchemy and prophecy. In fact, his writings indicate a fear of change rather than a desire to innovate. Thus the immense influence of Rupecissa's alchemical writings on fifteenth- and sixteenth-century scientific thought can detract from an understanding of how Rupecissa featured in the evolution of scientific and religious thought in the fourteenth century. Medieval alchemy, as the author argues, should not be considered solely as the forerunner of modern chemistry, but as a discipline closely connected with religious thought. To some extent, this book reclaims Rupecissa for the Middle Ages, indicating that his works are as important to the study of medieval thought as they are to an understanding of later scientific progress.

DeVun's reintroduction of spiritualism and religion into the study of alchemy is an important contribution to a subject most commonly associated with the history of chemistry. Historians of alchemy will also welcome the focus on medical alchemy, which is an underresearched area. The book will also appeal to historians of science working in a variety of other disciplines, particularly medicine, astrology and astronomy.