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Albumasar – De magnis coniunctionibus

In twelfth-century Western Europe, the study of astrology gained momentum as Moorish universities translated Arabic works about astronomy into Latin. Among the most popular of these texts was the writing of renowned ninth-century Muslim astronomer, Abu Maʻshar (Latinised as "Albumasar").  

Albumasar argued that astronomical changes could influence events, both good and bad, on earth. In Kitāb al-qirānāt (the Book of Conjunctions), he advocated an astrological interpretation of history based on the conjunctions of Saturn and Jupiter. According to his work, every 240 to 480 years, a holy prophet visits earth and a new religion or philosophy begins. Therefore, no human institution, including monarchies and religions, can ever hold a permanent state. This was a revolutionary way of thinking about causality; it offered an alternative to the traditional understanding of divine sovereignty, kingly authority and human free will. 

Albumasar’s conjunction theory took root throughout medieval Europe and influenced several European philosophers including Roger Bacon and Pico della Mirandola. His influence on the French cardinal and astrologer Pierre d’Ailly is particularly noteworthy. D’Ailly studied Albumasar’s astrological ideas in an attempt to balance divine sovereignty and human free will. When the Great Schism (1378-1417) in the Catholic Church occurred, d’Ailly perceived it as a sign that ecclesiastical reform was necessary because in the context of Albumasar’s conjunction theory, he believed that the schism was an omen for the arrival of the Antichrist. As a solution, the cardinal ardently advocated conciliarism and encouraged the establishment of the Council of Constance, which ended the schism and resulted in the election of Pope Martin V.

This item, entitled De magnis coniunctionibus in Latin, is a first edition translation by John of Seville from 1489. Latin translations of the text solidified Albumasar as a key link in the transmission of knowledge between ancient and medieval philosophers. Indeed, Richard Lemay, a leading historian in medieval astrology, argued that Albumasar’s work is how the world came to know of Aristotle’s theories on nature.

Considered the greatest astrologer of the Abbāsid court in Baghdad, Albumasar’s works made a significant contribution to the field of astrology throughout Persia and subsequently in Europe and Byzantium through translations. The Arcadian Library also holds the earliest known edition of Kitāb al-qirānāt in the original language from the 10th century.

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Pingree, D., 2011. Abū Maʻsar, Encyclopædia Iranica. [Online] Available at: [Accessed on 21 March 2019).

Hockey, T. et al (eds.), 2007. The Bibliographical Encyclopedia of Astronomers. New York: Springer.

Smoller, L. A., 1994. History, Prophecy, and the Stars: The Christian Astrology of Pierre d’Ailly, 1350-1420. Princeton, NJ: Princeton University Press.