The
Decretum
Gratiani

Discover fragments of a 13th-century canon law text preserved in an early modern book on ancient medicine.

A Hidden Manuscript

When Western Libraries sent a 16th century edition of the Aetii Medici Graeci for restoration, two leaves of the Decretum Gratiani were discovered serving as pastedowns inside its front and back covers. Preserved for seven centuries, these manuscript fragments are witnesses to the evolving traditions of medieval canon law and legal commentary.

Discovery & Provenance

Western’s edition of the Aetii Medici Graeci was printed in Basel, Switzerland in 1542. Translated into Latin by Janus Cornarius, the work preserves the medical knowledge of Aetius of Amida, a 6th-century Byzantine physician who synthesised the works of earlier Greek physicians like Galen and Soranus.

The book was donated to Western University in the early 20th century as part of the Hannah Collection on the History of Science and Medicine.

The pastedowns containing the Decretum Gratiani are roughly 200 years older than the book itself, dating to the early 13th century.

Who was Gratian?

Gratian (c. 1100-1150 CE) was a medieval jurist and canon lawyer for the Catholic Church. He was the first canonist to teach canon law in an academic setting. He taught at schools in Bologna, Venice, and Rome before being elevated to the office of Bishop of Chiusi, Tuscany. Contemporary scholarship knows little else about him as an individual.

Key Highlights

Published the Concordia Discordantium Canonum (now known as the Decretum Gratiani) around 1140 CE.
Known for being the first to apply the scholastic method to resolve canonical contradictions.

Historical Context

Prior to the creation of the Decretum Gratiani (c. 1140 CE), the medieval world of Western Europe was mired in a profound crisis of legal authority. The Catholic Church, which was rapidly centralising power, found itself in a confusing legal landscape characterised by a chaotic mass of contradictory regulations. This fragmented and deeply inconsistent legal heritage consisted of legal canons derived from papal decretals, Church councils (both universal and local), patristic writings (such as those of St Augustine and St Jerome), and secular laws from Germanic rulers, all issued in vastly different contexts over the course of a thousand years.

Gratian was the first canonist to embark upon an enterprise of synthesis intended to harmonise the methodology of Roman law with the discordant canons of the Catholic Church. Gratian is credited with elevating canon law to a distinct juridical science and his Decretum is widely considered a foundational text in the study of canon law, as it was the first treatise in the West to systematically coordinate and synthesise over a millenium of diverse texts.