Guido Bonatti

Definition

Guido Bonatti of Forli (c. 1207 – c. 1296 CE) was a 13th-century Italian astrologer who served Emperor Frederick II, Ezzelino da Romano, Guido da Montefeltro, and the city of Florence. His *Liber Astronomiae* (compiled c. 1277, copied widely, first printed in Augsburg in 1491) is the fullest medieval-Latin astrological compilation. It leans heavily on the Arabic-Persian tradition — Sahl, Maʿshar, Masha'allah, Al-Biruni, ʿUmar al-Tabari — to bring natal, horary, electional, and mundane practice together in one work.

In Tradition

In the medieval Latin and traditional-revival line, Bonatti is the chief Latin compiler who drew the Arabic astrological tradition together. His *Liber* sorts the inherited material into Tractates: universal principles, the judicial divisions (nativities, horary, electional, revolutions), and the history of mundane great conjunctions. The "146 Considerations" of Tractate V remain the standard set of horary preconditions — the points to weigh before judging a question (paraphrased here from the Project Hindsight Vol VII / Zoller translation, copyrighted-modern).

In Practice

Traditional astrologers today read Bonatti for an orderly, continuous account of medieval-Arabic doctrine: the temperament of each planet and the meaning of each planetary pairing in conjunction (Vol XI Tractate III), a catalogue of each house ruler placed in each house, the 146 horary Considerations, and the mundane technique that tracks the triplicity-shift of the great conjunctions. His material on the Lots, dignities, the almuten — the planet with the strongest overall claim on a point — and reception fed straight into Lilly's English horary in *Christian Astrology* (1647). Reading Bonatti through Project Hindsight (the Zoller, Hand, and Schmidt translations, copyrighted-modern), you treat the Latin original as public domain and the English as loose paraphrase only.

Historical Origin

Bonatti was born in Forli c. 1207 and died c. 1296. He worked in Bologna, Florence, and Forlì, and at the courts of Frederick II and Ezzelino da Romano. The *Liber Astronomiae* survives in the Venice 1506 and Basel 1550 incunabula and in numerous manuscripts; the standard modern translations are Project Hindsight (Robert Zoller, Vols VII–VIII; Robert Hand, Vol XI Part III; Robert Schmidt as editor) and the Dykes 2007 single-volume condensation. Dante refers to him in *Inferno* XX.118. Holden treats him as the dominant figure of the 13th-century Latin Arabic-mediated tradition.

Further Reading

• Guido Bonatti, Liber Astronomiae
• Robert Zoller (trans.), Bonatti on Basic Astrology (Project Hindsight Vol VII)
• James H. Holden, A History of Horoscopic Astrology