Definition
Non ability is a plea asserting that a party lacks the legal capacity or standing to perform a legal act, most commonly the capacity to sue or to be a party to a legal proceeding. The term encompasses both the substantive condition of being legally incapable and the procedural plea by which that incapacity is raised as a defense. Where a plaintiff is alleged to lack the legal status necessary to bring an action — whether by reason of infancy, coverture (historically), attainder, alienage, or some other legal disability — the defendant may plead non ability to defeat the action at the threshold, before the merits are reached.
Common Confusion
Non ability is easily confused with disability in its general sense and with want of capacity as used in contract law. The distinction matters: disability in modern law most often refers to a protected characteristic under civil rights statutes, whereas non ability is a term of pleading rooted in the common law and concerns legal standing to act, not protected status. Similarly, want of capacity in contract law typically addresses the ability to form a binding agreement, while non ability as a plea targets the right to appear and sue in court at all.
Why It Matters in Research
Researchers will encounter non ability almost exclusively in older common law pleading materials, English and early American treatises, and pre-code procedural sources. The term is effectively obsolete in modern practice, having been absorbed by contemporary doctrines of standing, capacity, and real party in interest rules (see, e.g., Federal Rule of Civil Procedure 17 and its state analogs). When reading historical pleadings or digests from the eighteenth or early nineteenth century, non ability functions as a threshold plea akin to what modern practice would call a challenge to capacity or standing. Researchers should be alert to the fact that the conditions giving rise to non ability pleas — particularly coverture and attainder — have been abolished by statute and constitutional amendment in virtually all common law jurisdictions, so the plea's practical scope has been substantially eliminated. The term may appear in historical equity records as well, where the ability of certain parties (corporations, married women, aliens) to invoke the court's jurisdiction was contested by plea before answer. Cross-referencing with pleas in abatement and with the history of legal disability is essential for understanding the procedural landscape in which non ability operated.
Historical Dictionary Support
Burrill's Law Dictionary defines non ability as the "want of ability to do an act in law, as to sue" and identifies it also as "a plea founded upon such cause," citing Cowell. This is a compact but accurate description. The entry captures both dimensions of the term: the underlying legal condition and the formal procedural vehicle for asserting it. Burrill's reliance on Cowell (John Cowell's Interpreter, a seventeenth-century legal glossary) signals that non ability was already an established term of art in early modern English law by the time Burrill compiled his dictionary. Historical sources are consistent on the core meaning but offer little elaboration on the range of circumstances that could ground such a plea or on how courts evaluated and disposed of it. Modern legal dictionaries do not carry the term, which itself reflects the procedural transformation wrought by code pleading and the Federal Rules.
Jurisdictional Note
Non ability as a distinct plea does not survive in modern American or English procedural codes. The substantive concern — whether a party has legal capacity or standing to sue — is addressed in the United States through FRCP 17 (real party in interest and capacity) and equivalent state provisions, and in England through the Civil Procedure Rules. Historical researchers working in pre-code American or English records should treat non ability as a plea in abatement equivalent.