Seminar on History and Philosophy of Science

Abstract: In Europe in the sixteenth century, astrologers made several types of predictions. They predicted weather or other potential natural disasters for the upcoming year, they determined the most propitious days for undertaking journeys, going to war, getting married, or laying the foundation for a new building, and they cast horoscopes for wealthy patrons. In the casting of horoscopes, determining the length of a client's life was common practice. For, according to the wisdom of the ancient astronomer Claudius Ptolemy, knowing the future enabled one to adequately prepare one's soul for the calamitous or fortunate. The medieval process for this calculation involved two technical terms which had been transliterated from Arabic-Latin translations of the twelfth and thirteenth centuries: the hyleg and alcocoden. Indeed, astrological texts of Arabic origin formed the majority of astrological manuscripts available to Latin scholars and were considered an authoritative source of astrological knowledge for centuries. However, humanist-led reforms of astronomy and astrology in the sixteenth century involved critiques not just of the language of Latin translations of Arabic astrological texts, but also of practices perceived as "Arabic" in origin. This paper examines the tensions between anti-Arab prejudices and astrological reform in Valentine Naibod's discussion of calculating the length of life. This discussion appears on Naibod's commentary on the most popular medieval treatise on astrology (also of Arabic origin), Alcabitius's Introduction to Astrology.