Definition
An action for the simple (single) amount — that is, a civil action in Roman law seeking recovery of the exact value of the loss or debt claimed, without multiplication or penalty. The phrase distinguishes this form of action from actions carrying enhanced or penal remedies (actio in duplum, actio in triplum, actio in quadruplum), where the defendant's liability could be doubled, trebled, or quadrupled depending on the circumstances, such as denial of liability or aggravated conduct.
In Roman procedural law, whether a plaintiff recovered in simplum or in a multiplied amount depended on the nature of the claim, the stage at which the action was brought, and, critically, whether the defendant contested the claim. Certain delicts (civil wrongs) imposed penal multiples as a matter of course; others defaulted to simple recovery unless the facts warranted enhancement.
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Common Confusion
ACTIO IN SIMPLUM vs. ACTIO IN DUPLUM / TRIPLUM / QUADRUPLUM: These terms form a family and are often encountered together in Roman law sources. Researchers should treat actio in simplum as the baseline — the measure against which penalty actions are defined. An action described in historical sources simply as "penal" or "mixed" almost certainly carries a multiplied remedy; actio in simplum signals the absence of that penalty element. The distinction is procedural and substantive simultaneously: it affects both the measure of recovery and the character of the action as penal or remedial.
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Why It Matters in Research
This term surfaces almost exclusively in sources dealing with Roman law or in common law treatises that draw on Roman procedural categories to explain the logic of penalty and damages doctrine. Researchers will encounter it most often in:
— Discussions of Roman delict and the distinction between remedial and penal actions, where actio in simplum anchors the scale.
— English equity and common law treatises from the 17th through 19th centuries that borrowed Roman taxonomies to explain forfeiture, bond penalties, and double-recovery provisions.
— Historical commentary on the law of usury, furtum (theft), and damnum injuria datum, where Roman sources specified whether recovery ran in simplum or a multiple.
The primary navigational trap is that the term rarely appears alone in historical sources. It is definitionally comparative — its meaning is only fully intelligible against its counterparts (duplum, triplum, quadruplum). A researcher who encounters it without context should immediately locate the surrounding discussion of those paired terms to understand which multiplied action the author is contrasting it against and why.
Burrill's entry is skeletal, pointing only to the Institutes (Justinian's Institutes, 4.6.21–22), which address the taxonomy of actions including penal, mixed, and simple forms. Researchers relying solely on Burrill risk underestimating the doctrinal freight the term carries in its original Roman context.
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Historical Dictionary Support
Burrill's Law Dictionary provides the only entry among the Law Mind shelf sources and is minimal: "An action for the thing," with a citation to Justinian's Institutes 4.6.21–22. The entry captures the core meaning but sacrifices context entirely. It does not explain the relationship to multiplied actions, nor does it identify the circumstances under which Roman law permitted or required simple rather than penal recovery.
No other Law Mind shelf dictionaries carry an entry for this term, which is consistent with its status as a term of art within Roman law scholarship rather than a working term in common law practice. Its appearance in common law dictionaries at all reflects the 18th- and 19th-century tradition of treating Roman categories as foundational to a complete legal education.
The Institutes passage Burrill cites (4.6.21–22) is genuine and does address the classification of actions by their measure of recovery, distinguishing actions that restore only the loss from those that impose additional penalty. That primary source remains the authoritative starting point for any substantive research on this term.
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Jurisdictional Note
Actio in simplum is a term of Roman civil law and does not operate as a living doctrinal category in any common law jurisdiction. It appears in civilian and mixed-law jurisdictions (Louisiana, Quebec, South Africa, Scotland) primarily in historical and comparative legal scholarship. Researchers working in those jurisdictions may find the concept structurally relevant to discussions of delictual remedies and penalty clauses.
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