Abū Ma’͑šar’s Great Introduction to Astrology (mid-ninth century) is the most comprehensive and influential text on astrology in the Middle Ages. In addition to presenting astrological doctrine, it provides a detailed justification for the validity of astrology and establishes its basis within the natural sciences of the philosophers. These two volumes provide a critical edition of the Arabic text; a facing English translation, which includes references to the divergences in the twelfth-century Latin translations of John of Seville and Hermann of Carinthia (Volume 1); and the large...