The Disputationes adversus astrologos are, measured by their size, the opus magnum of the renaissance philosopher Giovanni Pico della Mirandola. During the last months of his life Pico worked frantically on this treatise that aims at the complete refutation of astrology. The present book represents an important contribution to the understanding of the difficult Disputationes against the astrologers. It contains an edition of the first four books of this treatise, which consider the theological, cosmological, and philosophical arguments against astrology and lay the foundation for Pico's own cosmological conception of the world. The edition is accompanied by a face-to-face German translation and many explanatory notes. The large introduction examines life and work of Giovanni Pico, content and structure of the Disputationes, and sheds light on the complex textual tradition of the posthumously printed last work of Giovanni Pico.