Definition
A diagrammatic representation, arranged in the form of a tree, used in civil and canon law to display degrees of kinship and the lines of descent or consanguinity between persons. The arbor civilis mapped family relationships visually — branches representing generational steps, the trunk or root representing the common ancestor — to assist in calculating how closely two individuals were related for purposes of inheritance, succession, and restrictions on marriage.
The device served a practical computational function: determining whether a potential heir stood within the degree of relationship required to inherit, or whether two persons proposing to marry were within the prohibited degrees of consanguinity or affinity.
Why It Matters in Research
Researchers encountering arbor civilis in historical sources are almost always working in one of two contexts: the law of descent and inheritance, or the ecclesiastical law of marriage impediments. Understanding which context applies shapes how the surrounding material should be read.
The arbor civilis belonged specifically to the civilian and canonical tradition. English common law developed its own system of counting degrees of kinship — one that differed importantly from the Roman civil law method used in the arbor civilis. The civil law counted each generation as one degree between the common ancestor and each of the two persons being compared. The common law counted differently, measuring degrees along the line of descent rather than through the common stock. A researcher who does not account for this divergence will misread degree calculations in historical documents, particularly pre-seventeenth-century materials.
Bracton's use of this diagrammatic tree, referenced in Burrill, places the arbor civilis squarely in the early English reception of Roman legal concepts. Bracton drew on civilian sources extensively, and his tree diagram was a direct borrowing from that tradition. However, later English common law practice did not adopt the civilian counting method wholesale, creating a fault line in sources: texts influenced by Bracton or canon law use the civil law counting; later common law texts use the common law counting. Both may use tree imagery without flagging which method underlies the calculation.
In ecclesiastical court records and pre-Reformation marriage impediment cases, arbor civilis diagrams or references to them are routine. Researchers working in those collections should expect to encounter the term and should understand that the degrees shown reflect canon law computation, not common law.
Hale's History of the Common Law, cited by Burrill at page 335, is an accessible starting point for understanding how these two systems related and diverged in English legal history.
Historical Dictionary Support
Burrill is the primary historical dictionary source for this term in the Law Mind corpus. His entry is characteristically terse but accurate: he identifies the arbor civilis as a figure or table in the shape of a tree, used to show degrees of relationship and the course of descents, and he credits both Hale and Bracton as authorities. The Bracton reference is particularly valuable — it anchors the term in one of the foundational texts of English legal history and confirms that the device was known and used in England, even though it derived from civilian sources.
What Burrill's entry does not develop — and what researchers should supply from context — is the distinction between the arbor civilis (the civil law tree) and the arbor consanguinitatis as used in canon law. The two are closely related and often treated as equivalent, but the canonical tree was adapted specifically for determining marriage prohibitions and had its own elaborated form in ecclesiastical jurisprudence. Burrill collapses these without drawing the distinction, which is appropriate for a general law dictionary but insufficient for specialized research in either Roman law or ecclesiastical law.
No other Law Mind shelf dictionary provides a competing or supplementary entry for this term.
Jurisdictional Note
The arbor civilis as an operative legal tool belongs to the Roman civil law tradition and to canon law. It has no direct functional counterpart in modern American or English common law, though the underlying question — how degrees of kinship are calculated — remains live in inheritance and intestacy contexts. Modern statutory schemes in common law jurisdictions define their own counting methods, typically in probate codes or domestic relations statutes, and do not use the arbor civilis form.