Johann Heinrich Alsted, professor of philosophy and theology at the Calvinist academy of Herborn, was a man of many facets. A deputy to the famous Synod of Dort and the greatest encyclopaedist of his age, he was also a pioneer of Calvinist millenarianism and a devoted student of astrology, alchemy, Lullism, and the works of Giordano Bruno. This intellectual biography opens up unexpected perspectives on the central European Reformed tradition as a whole and provides an invaluable introduction to many of the central ideas, individuals, and institutions in this neglected area of intellectual history.