Roger of Hereford’s Judicial Astrology: England’s First Astrology Book?


The twelfth century saw a large number of Arabic texts on natural philosophy translated into Latin for the first time. Many of these texts were astrological, and had originally been translated into Arabic in the eighth and ninth centuries, shortly after the rise of Islam, from original Greek, Persian and Indian sources. Knowledge of astrology in Western Europe prior to the twelfth century was limited, although the need for Christians to calculate the date of Easter meant that an understanding of solar and lunar cycles was important, leading to the development of the science of computus, taught in secular cathedral schools, which were the main centres of learning in England in the twelfth century. One school with a reputation for scientific learning was the cathedral school at Hereford, and this research focuses on a text of a teacher there, Roger of Hereford, who compiled the newly-translated Arabic material on astrology into a single book, Judicial Astrology.

By the thirteenth century, astrology had become an established part of the curriculum taught in newly-established universities across Europe, and included studying works by Arabic astrologers that had been translated into Latin. What has not been researched in detail until now, though, is how astrology was taught in that century between the translation of Arabic texts and its establishment as part of the quadrivium in universities, and a detailed examination of Roger’s seminal book.

This thesis examines his Judicial Astrology in detail, analysing the astrological techniques used, identifying Roger’s sources, and looking at his teaching methods.

This thesis sets the context within which astrological texts were translated, and provides an analysis of every extant manuscript of Judicial Astrology. The conclusion examines Roger’s claim that he compiled the first astrology book in England, and asks whether it still stands as a usable text today.





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Mitchell, Christopher J. , “Roger of Hereford’s Judicial Astrology: England’s First Astrology Book?,” Centre for English Local History Theses and Papers, accessed September 29, 2022,