Definition
Onerari non is a Latin pleading formula meaning "ought not to be charged." It is the name given to a plea in an action of debt by which the defendant denies liability — asserting, in effect, that he should not be burdened with the obligation the plaintiff seeks to enforce. The phrase functions as the opening words of the plea, giving the plea its identifying name in the same way that other pleas take their names from their characteristic Latin or Law Latin commencement.
The plea stands as the debt-action counterpart to the actio non, a parallel formula used in other forms of action. Where the actio non (literally, "ought not to have this action") challenges the plaintiff's right to bring the suit at all, the onerari non more specifically denies that the defendant should bear the charge or obligation at issue.
Common Confusion
Onerari non and actio non both function as general traverses or special pleas at common law, and both are named after their opening Latin formula. The distinction is one of context: actio non appears across a broader range of actions, while onerari non was the proper form specifically in actions of debt. Burrill notes explicitly that onerari non was "substituted in some cases" for the actio non, which confirms the terms are related but not interchangeable. Researchers encountering either formula in historical pleadings should note the form of action before assuming equivalence.
Why It Matters in Research
This term will appear almost exclusively in pre-codification common law pleading records, treatises, and practice manuals — roughly from the medieval period through the mid-nineteenth century, when code pleading reforms (beginning with New York's Field Code of 1848 and spreading across American jurisdictions) swept away the formal system of common law pleading in which such Latin formulas had operative significance. A researcher encountering "onerari non" in a case report or pleading record from this period is seeing the formal commencement of a defendant's plea in debt, not a passing reference.
The practical trap: because onerari non and actio non are so similar in function, historical indexes and digests do not always cross-reference them reliably. A search for one may miss cases indexed under the other. Researchers working in early English or American debt litigation should search both formulas, as well as their anglicized descriptions ("ought not to be charged," "ought not to have this action") to capture the full range of sources.
The term also signals the procedural posture of the case. A plea of onerari non was a formal defensive plea on the merits of the debt obligation — distinct from a plea in abatement (which attacked the form of the action) and from a demurrer (which admitted the facts but denied legal sufficiency). Recognizing this posture helps a researcher quickly locate the defendant's substantive argument in historical records where procedural structure controls document organization.
No meaningful modern survival: onerari non has no functional equivalent in contemporary civil procedure. Under the Federal Rules of Civil Procedure and equivalent state codes, the defendant simply denies liability in an answer. The Latin formula carries no operative weight in any current American jurisdiction.
Historical Dictionary Support
All three source dictionaries agree on the core meaning without variation: onerari non is a plea in an action of debt, named for its opening words, by which the defendant asserts he ought not to be charged. Black's first and second editions reproduce the definition identically, suggesting the entry was not revised between editions — consistent with the term's status as a historical relic by the time both editions appeared (1891 and 1910, respectively).
Burrill adds the most useful detail, identifying the specific substitution relationship between onerari non and actio non, and citing Stephen's Principles of Pleading (Appendix, Note 69) as authority. Stephen's Pleading was a leading treatise on common law pleading in the early nineteenth century, and his appendix notes documented variant forms of standard pleas. Burrill's cross-reference to actio non (marked "q.v." — "which see") confirms that researchers encountering either term should consult both.
What the historical dictionaries collectively omit is any doctrinal analysis of when onerari non was required versus when actio non would suffice, or what consequences flowed from using the wrong form. That question — procedurally significant in its time — must be pursued in the pleading treatises directly: Chitty on Pleading, Stephen on Pleading, and Gould on Pleading are the primary sources.
Encyclopedia Cross-Reference
No Law Mind Encyclopedia entry directly addresses common law debt pleading or onerari non. The matching entries returned (non-solicitation agreements, non-disclosure agreements, non-compete enforceability) share no subject matter with this term and are not cross-referenced here.