Definition
The Decretum Gratiani — also known simply as the Decretum — is a foundational compilation of ecclesiastical (church) law assembled around 1140–1151 by Gratian, a monk and legal scholar associated with Bologna. It is the oldest and first in order of the collections that together form the Corpus Juris Canonici, the body of Roman canon law that governed the Western Church and, in significant respects, secular legal institutions across medieval Europe. The work organized and harmonized centuries of conflicting church decrees, papal pronouncements, conciliar decisions, and patristic writings into a systematic legal text. Its full original title, Concordia Discordantium Canonum (Harmony of Discordant Canons), describes its method: Gratian presented opposing authorities and then offered resolutions, making the work at once a legal code and a work of jurisprudence.
The Decretum is divided into three principal parts: the first addresses sources of law and the clergy; the second presents hypothetical cases (causae) resolved through canonical analysis; the third concerns liturgical and sacramental matters.
Common Confusion
The Decretum Gratiani is not a papal document. It was the private scholarly work of a monk, not an official act of the papacy or any church council. Despite its enormous authority in ecclesiastical courts, it never received formal papal promulgation — a fact with real legal and historical consequences. Researchers should also not conflate the Decretum with the later Decretales (specifically the Decretales Gregorii IX, issued 1234), which are papal constitutions collected under Gregory IX. The Decretum predates and is distinct from those later official collections, though both form part of the Corpus Juris Canonici. The two are sometimes loosely grouped under the label "canon law sources" in older English legal histories, which can obscure this important distinction.
Why It Matters in Research
Researchers encountering ecclesiastical jurisdiction, the canon law of marriage, inheritance disputes touching church courts, or the legal framework of medieval English ecclesiastical institutions will find the Decretum Gratiani operating as a background authority throughout pre-Reformation English legal history. Blackstone referenced it in the Commentaries (1 Bl. Comm. 82), and it surfaces in early equity and probate contexts where canon law principles migrated into English practice.
The date given in historical dictionaries — 1151 — is now questioned by modern scholars, who place the composition closer to 1140, with a second recension sometime thereafter. Researchers using the 1151 date in period sources should treat it as conventional rather than established. The Decretum was never "enacted" in any modern sense, which means arguments about its authority in English ecclesiastical courts depend on reception history, not formal adoption.
For corpus researchers, the Decretum is most likely to appear by name in treatises on ecclesiastical law, historical surveys of canon law's influence on equity, and discussions of marriage law before the Reformation. It appears rarely by its full Latin title in English common law sources; more often it is referenced obliquely through discussions of "canon law" or "the canonists." Bouvier cites Kaufmann's edition of Mackeldey's Civil Law as a useful secondary guide, which remains a practical starting point for understanding the Decretum's place in the larger canonical system.
Historical Dictionary Support
Black's (both editions) and Burrill agree closely, drawing on the same authorities: Blackstone's Commentaries and Reeve's History of English Law. All three describe Gratian as a "Benedictine monk of Bologna," though modern scholarship more often identifies him simply as a Bolognese monk or canonist, with his order uncertain. Bouvier aligns on the core characterization — oldest collection, part of the Corpus Juris Canonici — and adds Butler's Horae Juridicae as a reference. None of the historical dictionary sources engage with the Decretum's internal structure, its three-part division, or its methodological significance as a harmony of conflicting authorities. That gap matters: understanding why the Decretum was transformative requires knowing that Gratian did not merely compile but analyzed, and that analytical method influenced legal education well beyond canon law.
Rapalje & Lawrence contain no substantive entry, directing readers elsewhere without elaboration.
Jurisdictional Note
The Decretum Gratiani had direct legal authority in English ecclesiastical courts prior to the Reformation and informed areas of law — particularly marriage, legitimacy, and testamentary matters — that the common law courts later absorbed. Its authority in England was effectively terminated by the break with Rome under Henry VIII, though its influence on equity and probate jurisprudence persisted in attenuated form. In civil law jurisdictions with continuous canonical traditions, the Decretum's historical authority and interpretive legacy are more directly traceable.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Canon Law; Corpus Juris Canonici; Ecclesiastical Courts