Definition
Natura Brevium (Latin: "the nature of writs") is the title given to two distinct English legal reference works, both collecting and explaining the original writs available in the common law courts. The name refers specifically to:
1. Old Natura Brevium (O.N.B.): An anonymous collection of original writs compiled during the reign of Edward III (1327–1377), accompanied by brief comments and explanations. This is the earlier of the two works and is cited in historical legal literature as "O. N. B."
2. Fitzherbert's Natura Brevium (F.N.B. or Fitzh. Nat. Brev.): A later and more comprehensive treatise compiled by Sir Anthony Fitzherbert during the reign of Henry VIII (1509–1547). This work superseded the Old Natura Brevium in practical use and became the standard reference for writ practice in the English common law tradition. It is cited as "F. N. B." or "Fitzh. Nat. Brev."
Both works belong to the genre of abridgments and registers that guided practitioners in selecting and drafting the proper original writ to commence an action. Because each form of action at common law required the correct writ, these compilations were essential working tools for medieval and early modern English lawyers.
Common Confusion
The two works sharing the name Natura Brevium are routinely conflated in older legal writing and citations. When a historical source cites "Natura Brevium" without further qualification, the researcher must determine from context and date which work is meant. Fitzherbert's version (F.N.B.) is cited far more frequently in substantive legal argument; citations to the Old Natura Brevium tend to appear in discussions of writ history rather than in precedential analysis. The abbreviations "O. N. B." and "F. N. B." are the reliable distinguishing markers, but not all historical authors used them consistently.
Why It Matters in Research
Researchers encounter Natura Brevium citations most often in one of two contexts: historical analysis of the English forms of action, or citation-tracing in early American common law sources that inherited English writ practice. Several traps attend both contexts.
First, the citation ambiguity problem is real and consequential. Pre-nineteenth-century English and American treatises sometimes cite "Nat. Brev." without specifying which work, and the two texts are not interchangeable. Fitzherbert's version is substantially more authoritative and analytically developed; assuming a citation refers to it when the Old Natura Brevium is intended (or vice versa) can distort understanding of the point being made.
Second, these works are keys to understanding abolished procedure. The writs catalogued in both texts — novel disseisin, mort d'ancestor, darrein presentment, and dozens of others — were the procedural backbone of English common law before the reforms of the nineteenth century. A researcher working with pre-reform English cases or with early American common law materials will encounter frequent references to writs that no longer exist as live procedural tools. Natura Brevium provides the original descriptive framework for those writs, making it indispensable as a reference when parsing what a historical court was actually deciding.
Third, American reception varies. Some early American jurisdictions adopted English writ practice wholesale and thus treated Fitzherbert's Natura Brevium as persuasive authority; others moved quickly to code pleading and rendered the work obsolete. The date at which a given jurisdiction transitioned away from common law forms of action determines how long Natura Brevium citations remained relevant in that jurisdiction's legal writing.
Fourth, the corpus researcher should note that Bouvier's Law Dictionary treats the two works as a lineage — Old giving way to New — while Black's focuses primarily on distinguishing them by name. Neither dictionary provides the full bibliographic detail needed to locate the texts themselves; researchers who need the actual text of Fitzherbert's Natura Brevium should consult the original printed editions or modern historical reprints separately.
Historical Dictionary Support
Black's Law Dictionary (both the first and second editions) defines Natura Brevium consistently: an ancient collection of original writs from the time of Edward III, with the editorial note distinguishing it from Fitzherbert's later work. The entries are nearly identical across editions, which reflects the purely historical status of the term — it had no living procedural significance by the time Black's was compiled, and no updating was needed.
Bouvier's Law Dictionary adds useful context absent from Black's: it situates the succession explicitly, noting that Fitzherbert's work arose in the reign of Henry VIII and thereafter caused the earlier compilation to be known as the "Old" Natura Brevium. Bouvier cites Byrne for this account, a point worth noting since the citation chain back to Byrne is not independently verifiable from the dictionary entry alone.
A meaningful gap in all three sources: none of them explains the substantive content of either work with any detail. A researcher who encounters a citation to a specific writ in Natura Brevium will not find it explained in these dictionary entries; the dictionaries confirm what the works are, not what they contain. For the substance, the works themselves — or a treatment such as Maitland's historical lectures on forms of action — must be consulted directly.
Jurisdictional Note
Fitzherbert's Natura Brevium was an English work and its direct authority was always confined to English common law jurisdictions. American courts in the colonial and early republic periods occasionally cited it as evidence of the common law tradition, but its relevance diminished sharply as American jurisdictions reformed pleading. It retains significance today only in historical and comparative legal scholarship.