Definition
De rationalibus divisis (Latin: "concerning reasonable divisions") is a historical common law writ used to determine and fix the boundaries between lands belonging to two different persons when those lands lay in separate towns or manors. The writ was issued at the instance of a party who claimed that the other had encroached upon his land, and it directed commissioners or officers to go upon the ground and establish the true line of division between the adjoining properties. Because the lands straddled the boundary of two distinct jurisdictions — different towns, manors, or vills — the ordinary local remedies were inadequate, and this writ provided the mechanism for resolving the dispute at a higher level.
The writ belongs to the broader family of boundary-setting remedies in medieval English law and is distinct from actions to try title to land outright. Its purpose was not to determine who owned either parcel in fee but to settle where one holding ended and the other began.
Common Confusion
De rationalibus divisis is sometimes loosely grouped with the writ of perambulation, which similarly involved the physical walking and marking of boundaries. The critical distinction is jurisdictional context: de rationalibus divisis addressed boundaries where the lands lay in different towns or manors, making a single local inquiry impractical. Perambulation was more commonly associated with the re-marking of parish or forest boundaries. Researchers should not treat references to one as interchangeable with the other in historical sources.
Why It Matters in Research
This is an archaic writ with no modern procedural counterpart. Researchers will encounter it almost exclusively in pre-nineteenth-century English legal sources — Year Books, early abridgments, Fitzherbert's Natura Brevium, and histories of English law such as Reeves. It does not appear in American practice as a live writ; colonial and early American courts developed their own boundary dispute procedures, and de rationalibus divisis faded from use long before American law matured.
Two research traps are worth noting. First, because the writ is defined by its jurisdictional trigger — lands in different towns — sources that discuss boundary writs generically may omit it in favor of more common remedies. Researchers tracing the history of boundary adjudication should check sources specifically treating the medieval writ system rather than relying on general property law digests. Second, the Latin phrase varies in spelling and abbreviation across historical sources; older abridgments may truncate or anglicize it, and searches in digitized historical databases should account for variant forms.
The writ is significant for legal historians studying the evolution of real property procedure, the fragmentation of local jurisdiction in medieval England, and the mechanisms by which royal courts extended their reach into disputes that local courts could not efficiently handle. It also illustrates the practical problem that inter-jurisdictional land boundaries posed before unified survey and recording systems existed.
Historical Dictionary Support
Rapalje and Lawrence define the writ concisely as one "to determine the boundaries between the lands of two persons which lay in different towns, where one party complained of encroachment," citing Fitzherbert's Natura Brevium 128 M and Reeves's History of English Law, volume 3 at page 48. These citations point researchers to the two most useful primary and secondary sources for this writ: Fitzherbert as the classic practitioner's guide to the forms of writs, and Reeves as the standard narrative history of English law's procedural development.
The historical dictionaries offer little beyond this bare procedural description. None of the standard sources — Bouvier, Black, or the English law dictionaries — devote substantial analysis to the writ's theoretical foundations or its relationship to broader property doctrine. This reflects the writ's character as a practical procedural tool rather than a conceptually generative legal device. What the historical sources do not supply is any account of how frequently the writ was actually used in practice, how it interacted with other boundary remedies, or when it fell into disuse. For those questions, researchers must go beyond the dictionary literature to the Year Books and the secondary historical scholarship on medieval English procedure.
Jurisdictional Note
De rationalibus divisis is exclusively an English common law writ. It was never adopted as a live procedural instrument in American courts, though American legal historians and property scholars may reference it when tracing the ancestry of modern boundary dispute procedures. Researchers working in English legal history should note that the writ's operation was tied to the specific structure of vill and manor jurisdiction, which has no precise American equivalent.
Encyclopedia Cross-Reference
See: Boundary Disputes (Historical English Procedure); Real Actions (Medieval Writ System)