This is the definitive study of John Dee and his intellectual career. Originally published in 1988, this interpretation is far more detailed than any that came before and is an authoritative account for anyone interested in the history, literature and scientific developments of the Renaissance, or the occult. John Dee has fascinated successive generations. Mathematician, scientist, astrologer and magus at the court of Elizabeth I, he still provokes controversy. To some he is the genius whose contributions to navigation made possible the feats of Elizabethan explorers and colonists, to others an alchemist and charlatan. Thoroughly examining Dee's natural philosophy, this book provides a balanced evaluation of his place, and the role of the occult, in sixteenth-century intellectual history. It brings together insights from a study of Dee's writings, the available biographical material, and his sources as reflected in his extensive library and, more importantly, numerous surviving annotated volumes from it.