This is the first edition ever of Moerbeke's Latin translation of Ptolemy s celebrated astrological handbook, known under the title Tetrabiblos or Quadripartitum (opus). Ptolemy s treatise (composed after 141 AD) offers a systematic overview of astrological science and had, together with his Almagest, an enormous influence up until the 17th century. In the Latin Middle Ages the work was mostly known through translations from the Arabic. William of Moerbeke s translation was made directly from the Greek and it is a major scholarly achievement manifesting not only Moerbeke s genius...