This book provides a uniquely detailed case study of the origins of millenarianism within the vast opera of one of its earliest and most influential Calvinist exponents: the Herborn encyclopedist Johann Heinrich Alsted (1588-1638). The young Alsted, it emerges, looked forward not to the millennium of Apocalypse 20 but to a brief, final period of enhanced illumination described in a poorly understood central European tradition of astrological, alchemical, spiritualist, and generally 'occult' prophetic speculation. It was the disasters following the Bohemian Revolt of 1618 which forced Alsted to recast these expectations as the more exclusively scriptural expectation of a literal millennium; and the material for this revision was found in a protracted dispute over the millennium between senior theologians in Herborn and Heidelberg and a little-known work on the conversion of the Jews by one of the figures most probably behind the composition of the Rosicrucian manifestos. Based on study of the full range of Alsted's works, his diverse sources, and widely dispersed manuscript material, the result is the first English book on 17th-century continental millenarianism and the first monograph in any language exclusively devoted to the origins of the doctrine within mainstream Protestantism.