BLUEMOON
The Moon can sometimes appear bluish because of atmospheric conditions, but the
expression “once in a blue Moon” refers to a month during which two full moons
occur—one at the beginning and the other near the end of the month. This happens
only once every few years.
BONATTI, GUIDO
The astrologer Guido Bonatti was born in Cascia, Italy, although his birthdate is
unclear. We know he was in the Italian cities of Ravenna and Bologna, in 1223, and
in Forli by 1233. He was advisor to Frederick II Hohenstaufen, the Holy Roman
Emperor. In 1259, Bonatti entered the service of the tyrant Ezzelino III da Romano,
and the following year he became astrologer to Count Guido di Montefeltro. Bonatti
was the author of the Liber astronomicussometime after 1282. He died in 1297. In His-
tory of Magic and Experimental Science(1923), Lynn Thorndike reports that Dante put
Bonatti in the eighth circle of his Inferno: “Vedi Guido Bonattià”—Inferno, XX, 118.
Bonatti was a well known and influential man in his day and still highly
regarded in Forli and Bologna. He was an aristocrat, an adviser to the mighty, and a
learned man. The chroniclers of the day—Giovanni Villani, Fossi, Salimbene di
Adam—took note of him. The Annales of Forlireport that he played a prominent part
in the defense of Forli in 1282 by Guido Montefeltro against a large force sent by Pope
Martin IV. Despite the high regard he was held in during his lifetime (which contin-
ues in Bologna and Forli to this day, where Guido Bonatti has the status of a kind of
local hero), there are few reliable details about his life. The date of his birth is a mys-
tery. The year of his death is debated; Thorndike thinks it closer to 1300 than 1297.
Bonatti is said to have ended his life as a Franciscan monk.
Bonatti’s role in the spread of astrology in western Europe in the thirteenth
century was an important one. The twelfth century saw the western Christian world
suddenly become obsessed with Arabic Science (called the “New Science”). Astrology
played a central role in this New Science. The transmission of Arabic astrology to the
Latin West and a renewal of interest in both Greek and Arabic astrology among the
Byzantines led to translation projects, principally in Spain and Sicily, where transla-
tors worked avidly and prolifically to make Arabic astrological texts available to the
Latins. The thirteenth century saw the widespread assimilation of this recently
acquired astrological science and to ecclesiastical opposition to it. Astrology was con-
demned by the church in 1210, 1215, and 1277. These multiple condemnations show
that no one was listening. Instead of giving up astrology, western Europeans were prac-
ticing it and comparing the many texts circulating in western Europe.
Bonatti’s Liber astronomicusis an outstanding exemplar of the thirteenth-cen-
tury dissemination and assimilation in Christian western Europe of Arabic astrology.
It is a Summa of astrology based upon the author’s collection, collation, comparison,
and application of the existing Latin translations available to him. Bonatti was a prac-
ticing astrologer. In his day, his reputation was good.
THEASTROLOGYBOOK [91]
Bonatti, Guido