The present volume offers the first critical edition of the Hebrew text of the two versions of Ibn Ezra's Book of the World, accompanied by an English translation and a commentary. These twin treatises represent the first Hebrew work, unique in medieval Jewish science, to discuss the theories and techniques of historical and meteorological astrology that had accumulated from Antiquity to Ibn Ezra's time, on the basis of Greek, Hindu, Persian, and Arabic sources. This volume also incorporates the first critical edition, translated and annotated, of Masha allah's Book on Eclipses, a work dealing with mundane astrology whose Hebrew translation was ascribed to Ibn Ezra, as well as a study of three brief texts in which Ibn Ezra conveyed his own opinion about mundane astrology.