Elizabethan England's most famous natural philosopher John Dee recorded his reflections on the natural world, the practice of natural philosophy, and the apocalypse in a series of conversations with angels, which have long been an enigmatic facet of his life and work. This book makes extensive use of Dee's library and annotations to clarify this mystery by providing a detailed analysis of these conversations. Professor Harkness contextualizes Dee's angel conversations within the natural, philosophical, religious, and social contexts of his time, arguing that the conversations represent a continuing development of John Dee's earlier concerns and interests. This book will appeal to those with an interest in the history of science, students of religion, and everyone who approaches the new millennium with a wary eye.