Definition
A Latin term meaning strength, virtue, force, or efficiency. In legal usage, *vigor* (rendered *vtgor* in some historical typographic conventions) denotes the operative force or inherent efficacy of a legal instrument, rule, or authority — the quality by which a law, document, or provision acts of its own power to produce legal effect.
The term appears most commonly in the phrase *proprio vigore* ("by its own force"), describing a legal instrument, statute, or provision that operates independently, without need of external support, supplementary authority, or judicial construction to give it effect.
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Common Language
Modern common usage (Wiktionary): *Vigor* denotes physical strength, energy, or active force in a person or thing.
Historical common usage (Webster's 1913): *Vigor* — "Active strength or force of body or mind; capacity for exertion, physical or intellectual; force; energy."
The gap between common and legal usage is narrow but specific. In ordinary English, vigor describes a quality of living things or active effort. In law, it is transferred to instruments and rules themselves — a statute has *vigor* not because it strains but because it carries legally operative force independent of any actor's will. The phrase *proprio vigore* crystallizes this distinction: the law acts; no one needs to act for it.
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Common Confusion
The archaic spelling *vtgor* reflects pre-modern Latin typography in which the letter *u* was rendered as *v* in certain manuscript and print traditions. Researchers encountering this form in older digests, abridgments, or reprinted dictionaries should treat it as identical to *vigor*. It is not a separate term.
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Why It Matters in Research
Researchers working with early English and Anglo-American legal sources will encounter *vtgor* or *vigor* almost exclusively in Latin maxims and brocard collections rather than as a standalone doctrinal term. The critical phrase to recognize is *proprio vigore*, which appears in historical case law and treatises to signal that a document, statute, or rule is self-executing — that it requires no further act to bring it into legal operation.
This distinction carries real doctrinal weight in several contexts: whether a treaty operates domestically without implementing legislation, whether a constitutional provision is self-executing, or whether a deed or conveyance passes title without delivery or enrollment. When a historical source says an instrument operates *proprio vigore*, it is making an affirmative claim about legal sufficiency — a claim researchers should flag and trace, because courts and commentators did not always agree on which instruments qualified.
The typographic variation (*vtgor* vs. *vigor*) can confuse keyword searches in digitized historical sources. Searching only for the modern spelling may miss relevant passages in early printed materials. When working in corpus sources drawn from pre-18th century texts, both forms should be searched.
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Historical Dictionary Support
Black's Law Dictionary (2nd Ed., Supplemental) gives the entry concisely: "Strength; virtue; force; efficiency. *Proprio vigore*, by its own force." This is representative of how historical legal dictionaries treat the term — as a Latin gloss with its primary legal utility located entirely in the *proprio vigore* construction. No historical dictionary in the standard shelf significantly elaborates beyond this, which accurately reflects the term's function: it is a building block for maxims rather than a freestanding legal concept with its own doctrine.
The inclusion of "virtue" in the definition is worth noting. In classical and early modern Latin, *virtus* and *vigor* overlapped in meaning, both connoting intrinsic operative capacity. The conflation in Black's reflects this classical usage rather than any technical legal distinction between strength and virtue as separate concepts.
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Encyclopedia Cross-Reference
See Law Mind Encyclopedia: *Self-Executing Provisions*; *Latin Maxims in Anglo-American Law*.
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