The short canonical tract entitled De ratione matrimonii, dating to the late eighth or early ninth century, offers straightforward rules on marriage drawn from a variety of authoritative texts. Its enduring appeal is evinced by the survival of at least twenty-three manuscript witnesses from the early ninth to the twelfth century, uninfluenced by important developments regarding marriage within Christian society during that period. Despite its potential to shed light on fundamental thoughts on the topic of marriage within Christian society between the eighth and twelfth centuries, this short tract has escaped the close attention of modern scholars. This article, due to be published in Traditio 81 (2026), presents the tract, describes its context and character and provides its first critical edition with an English translation. An examination of the text reveals its dependence on a peculiar version of the Irish Collectio canonum Hibernensis, offering insights into the development of this important early medieval canonical collection. In addition, the tract is a rare example of a set of pragmatic guidelines for early medieval societies, through its focus on practical rather than doctrinal norms about starting, living in, and ending a marriage. The study of the mostly fragmentary witnesses to the text not only sheds light on medieval concerns about rightful marriage but also reveals the conscious editorial choices made by individual scholars and copyists throughout this period.
