Definition
Formido periculi (Latin: "fear of danger") is a civil law maxim expressing the apprehension of threatened harm or peril as a recognized legal condition. In its classical usage, the phrase captures the psychological state of a party who acts—or is excused from acting—under a reasonable fear that danger to person, property, or legal rights is imminent or probable. It appears most often in discussions of duress, necessity, and the justifications available to parties who take protective action in anticipation of harm rather than in direct response to it.
The concept is closely associated with the broader civil law treatment of fear (metus) as a vitiating factor in contracts and legal obligations. Where formido periculi is established, it may excuse delay, justify preemptive action, or support a claim that consent was not freely given.
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Why It Matters in Research
This is a pure civil law maxim with narrow but specific applications in historical legal writing. Researchers are most likely to encounter it in treatises and early American common law commentary—particularly in Kent's Commentaries on American Law, the single source cited across all historical dictionaries for this term. The citation to 1 Kent, Comm. 23 is consistent across every entry and functions as the effective anchor text for the phrase in American legal literature.
The term rarely appears in modern case law or statutory materials. If you encounter formido periculi in a historical document, the surrounding context will almost always concern one of three doctrinal questions: (1) whether fear excuses non-performance of a legal duty; (2) whether anticipatory action taken to avert danger was justified; or (3) the civil law foundations of duress or metus as a defense to contractual obligation.
Researchers working in equity, early American jurisprudence, or conflict of laws should note that Burrill's adds a second citation—Huber de Jure Civili, lib. 3, c. 7, sec. 4—drawing the term directly to Ulrik Huber's civilian jurisprudence. This connection signals that formido periculi was understood by early American legal writers as a civil law import, not a common law term of art, and should be traced through that literature accordingly.
Do not expect this phrase to yield useful results in modern full-text legal databases. It is a research artifact of the civil law tradition as filtered through early American treatise writing. Its doctrinal substance has been absorbed into modern discussions of duress, coercion, and necessity without the Latin label.
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Historical Dictionary Support
All three source dictionaries—Black's (first and second editions) and Burrill's—give the same terse translation: "fear of danger," with citation to Kent. The uniformity is itself informative: it suggests that by the time these dictionaries were compiled, the phrase had settled into a standard reference rather than an actively contested or developed doctrine. None of the entries attempt to expand the definition beyond the Latin meaning, and none offer case law.
Burrill's entry is marginally the richer of the three, adding the Huber citation and thus preserving the civil law lineage that Black's omits. This is characteristic of Burrill's general method—more attentive to civilian and historical sources—and researchers working on the doctrinal genealogy of duress or necessity in American law will find Burrill's the more useful starting point here.
What the historical dictionaries collectively miss: they do not discuss the relationship between formido periculi and metus (fear as a vitiating factor in Roman and civil law), nor do they draw the connection to contemporaneous equity doctrine on duress. A researcher relying only on these entries would have the phrase identified but not its functional doctrinal context.
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Jurisdictional Note
Formido periculi is not a term of art in any modern American jurisdiction's statutory or case law. Its relevance is confined to historical and comparative legal research, particularly in jurisdictions with civil law influence (Louisiana, Quebec) or in scholarship tracing the civil law foundations of American equity and contract doctrine.
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