IDEM PER IDEM - The Law Mind Legal Dictionary

IDEM PER IDEMAuthored

The Law Mind • 1022 words

Definition

Latin: "the same for the same." A logical fallacy in legal argument or reasoning in which a proposition is explained or illustrated by restating it in equivalent terms — offering nothing that genuinely advances the analysis. An argument or illustration is idem per idem when it merely substitutes one formulation of an idea for another without adding new substance, proof, or clarification. The phrase functions as a critical label: to call an argument idem per idem is to expose it as circular or tautological.

The concept appears most often in the context of contract consideration, pleading, and logical sufficiency of legal argument. In contract law, it describes a purported consideration that is actually just a restatement of the promise itself — no independent element is provided that could support enforcement. More broadly, it applies whenever a court or advocate identifies that a cited authority, example, or illustration adds nothing to the question at hand because it simply mirrors the original proposition.

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Common Language

Modern common usage (Wiktionary): Not independently defined; recognized as a Latin phrase meaning "the same for the same" or "the same by means of the same."

Historical common usage (Webster's 1913): Not separately defined; treated as a Latin expression equivalent to a circular statement or tautology in general discourse.

The gap between ordinary and legal usage is one of application rather than meaning. In common language the phrase gestures vaguely at redundancy or repetition. In legal usage it is a precise critical term — invoking it identifies a specific analytical defect: that a proposed illustration, consideration, or argument imports no new element and therefore cannot do the logical or legal work being asked of it.

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Common Confusion

IDEM PER IDEM vs. IDEM SONANS: These two Latin phrases share the prefix and appear in close proximity in historical dictionaries, which has led to their occasional conflation. They are entirely unrelated. Idem sonans ("sounding alike") is a doctrine of name misspelling in pleadings and indictments — substantive law governing the sufficiency of names in legal instruments. Idem per idem is a logical and argumentative concept with no connection to names or phonetics. Researchers encountering either phrase in historical sources should confirm which term is actually at issue.

IDEM PER IDEM vs. CIRCULAR REASONING (PETITIO PRINCIPII): The two concepts overlap but are not identical. Circular reasoning (begging the question) assumes a conclusion within its premises. Idem per idem is narrower: it specifically identifies the use of an illustration or supposed additional element that turns out to be nothing more than a restatement of what is already before the court. The phrase is used to dismiss a purported contribution — an analogy, authority, or consideration — as adding no independent analytical value.

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Why It Matters in Research

Researchers are most likely to encounter idem per idem in two contexts: judicial opinions criticizing inadequate argument or illustration, and contract law discussions of consideration. In the consideration context, courts and treatise writers use the phrase to flag an exchange in which one side's "consideration" is simply a rephrasing of the obligation already owed — functionally, the promise is being used to support itself. This connects directly to the doctrine of illusory promises and the sufficiency of consideration.

In historical sources, the term appears without extensive elaboration precisely because its meaning was treated as self-evident to a legally trained reader. Bouvier and Rapalje both define it in a single sentence and immediately pivot to adjacent Latin maxims — a pattern that can mislead modern researchers into thinking the concept is less significant than it is. The phrase does real work in judicial reasoning even when it appears only briefly.

Searches in historical corpora may not surface the term reliably because it often appears mid-sentence as a qualifying label rather than as a headword or keyword of the dispute. Boolean searches for "idem per idem" should be supplemented by searches for "circular" and "tautolog-" in the same doctrinal neighborhoods.

The maxim appended in several sources — Idem semper antecedenti proximo refertur ("the same is always referred to its next antecedent," Co. Litt. 685) — is a separate principle of grammatical construction in legal instruments, governing pronoun reference. It is not a sub-rule of idem per idem; its proximity in historical dictionaries is alphabetical, not conceptual.

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Historical Dictionary Support

All four source dictionaries define idem per idem in nearly identical language: "the same for the same; an illustration of a kind that really adds no additional element to the consideration of the question." This uniformity suggests the definition was well-settled and that compilers were drawing from a common tradition rather than independently reasoning through the concept.

None of the historical sources elaborate on the doctrinal significance of the phrase in contract or pleading law, or provide examples from reported cases. Bouvier pivots immediately to idem sonans; Rapalje does the same. Black's first and second editions reproduce the same sentence and add the Co. Litt. maxim without connecting it analytically. This uniform brevity across four dictionaries spanning several decades indicates that the term was treated as a logical term of art requiring no doctrinal development — it was assumed the reader would know where to apply it.

What the historical dictionaries collectively miss is any guidance on distinguishing idem per idem from related logical defects, and any explanation of how courts actually deployed the phrase in opinions. Researchers relying solely on these sources will have the Latin translated but little practical guidance on application.

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Jurisdictional Note

Idem per idem is a common law logical concept rather than a jurisdiction-specific rule. It appears across English and American courts wherever Latin maxims were in active use. Its application in consideration doctrine is more prominent in English common law sources; American courts have largely addressed the same problem through the plain-English vocabulary of illusory promises and circular consideration without always invoking the Latin phrase.

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IDEM PER IDEMmain

Black's Law Dictionary • 1891

The same for the An illustration of a kind that really same. adds no additional element to the considera- tion of the question.

IDEM PER IDEMmain

Rapalje & Lawrence • 1888

- The same for the same. An illustration of a kind that really adds no additional element to the consideration of the question. Idem semper antecedenti proximo refertur (Co. Litt. 685): "The same" is always referred to its next antecedent. IDEM SONANS.-Sounding alike. The courts will not set aside proceedings on account of the misspelling of names, provided the variance is so trining as not to mislead, or the name as spelt ne idem sonans, as Lawrance instead of Law-nce, Reynell for Reynolds, Beneditto for Benedetto. 1 Cromp. and M.806; 1 Chit. 659, 6 Price 2; 2 Taunt. 401. See VARIANCE. IDEM SONANS, (when name is). 2 N. H. 557, 558; 7 Wheel. Am. C. L. 50; 16 East 110.

IDEM PER IDEMmain

Bouvier's Law Dictionary • 1928

The same for the same. An illustration of a kind that really adds no additional element to considera- tion of the question. IDEM SONANS (Lat.). Having the same sound. In indictinents and pleadings, when a name which it is material to state is wrong- ly spelled, yet if it be idem sonans with that proved, it is sufficient. The following have been held to be idem sonans, Segrave for Seagrave; 2 Stra. 889; Whyneard for Winyard; Russ. & R. 412; Benedetto for Beneditto; 2 Taunt. 401; Keen for Keene; Thach. Cr. Cas. 67; Deadema for Diadema; 2 Ired. N. C. 346; Hutson for Hudson; 7 Mo. 142; Coonrad for Conrad; 8 Miss. 291; Gibney for Giboney: 81 Tex. 422; Allen for Allain; 144 Ill. 32; Emerly for Emley; 1 Tex. Civ. App. 695; Johnston for John- son; 50 Kan. 420; Busse for Bosse; 86 Tex. 336; Chambles for Chambless; 28 Ala. 53; Conly for Conolly; 2 Greene (Iowa) 88; Usrey for Usury; 10 Ala. 370; Faust for Foust; 163 U. S. 452; Bubb for Bopp; 39 Pa. 429; Heckman for Hackman; 88 id. 120; Shaffer for Shafer; 29 Kan. 337; Woolley for Wolley; 21 Ark. 462; Penryn for Pennyrine; 14 Md. 121; Barbra for Barbara; 52 Kan. 35; Isreal B. for Is- rael B.; 32 Tex. Cr. Rep. 637; Alwin for Alvin; 50 Ill. App. 202; Helmer for Hill- mer; 34 Tex. Cr. Rep. 415; July for Julia; id. 1; Elliott for Ellett; 85 Tenn. 171; Chegawgequay for Chegawgoquay: 75 Mich. 289; Kealiber, Keoliher, Kelliher, Kellier, Keolhier, Kelhier, all sufficient for Kealiher; 81 Me. 531; Luckenbough for Luckenbach; 78 Ia. 101; Rooks for Rux; 83 Ala. 79. The rule seems to be that if names may be sounded alike without doing violence to the power of letters found in the various orthography, the variance is imma- terial; 27 Tex. App. 30; 1 Whart. Cr. L. 309; 1 Bish. Cr. Proc. § 688; 28 Am. Rep. 435. Whether or not the names are idem sonantia was held a question for the jury, where the name was laid Darius C (pro- nounced in Dorset dialect D'rius) and it was in fact Trius; 2 Den. Cr. Cas. 231; 3 Russ. Cr. Sharsw. ed. 317. See 6 Ala. N. S. 679; 147 Mass. 414. In the following cases the variances there mentioned were declared to be fatal; McCarn for McCann; Russ. & R. 351; Shakspeare for Shakepear; 10 East 83; Calver for Calvert and Day for Dax ; 2 Cr. & M. 189; Moores for Mohr; 55 Mo. App. 325; Mulette for Merlette; 100 Ala. 42; Siemson for Simonson ; 21 S. W. Rep. (Mo.) 510; Bart for Bartholomew; 29 II. 508: Comyns for Cummins; 24 III. 602; Grautis for Gerardus; 4 Cow. 148; Henry for Harry; 21 Ill. 535; Jeffery for Jeffries; 1 Hempst. 299; Byerly for Byrly; Baldw. 83. The same principle applies to words as well as names, and a verdict is not vitiated by misspelling if the words are idem sonans, as mrder for murder, turn for term, too for two; but a verdict for damages was void when given for impunitive damages, or when a burglar was found guilty of bergel- lery, or where the defendant was found guity instead of guilty, there being no such words as the last three in English; 2 Tex. App. 487; id. 504; 4 id. 527; 36 Tex. 152. See, generally, 3 Chitty, Pr. 231, 232; 4 Term 611; 3 B. & P. 559; 3 Campb. 29; 6 M. & S. 45; 2 Ν. Η. 557; 7 S. & R. 479; 3 Cai. 219; 1 Wash. C. C. 285; 4 Cow.148; 3 Stark. Ev. § 1678; 4 U. S. App. 524; 143 Ill. 634; 24 Alb. L. J. 444; 27 Am. St. Rep. 785; 13 L. R. A. 541; Harris, Identification, Ch. III.

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