Definition
A Roman civil law term for a person placed in charge of a commercial establishment — typically a shop or store — and authorized to conduct buying and selling on behalf of a principal. The institor was, in modern terms, a commercial agent with actual authority to transact business within the scope of the appointment.
Burrill's definition captures the full scope: the institor could be fixed to a particular place of business (a taberna, or shop), or could operate without a fixed location but with authority to buy and sell generally. In either form, the defining feature was the grant of authority to act commercially on behalf of another, binding that principal to third parties who dealt with the institor in good faith.
The corresponding legal action — the actio institoria — allowed third parties who had contracted with an institor to compel the principal to perform or pay. This was a praetorian remedy, available because the institor, often a slave or person without independent legal standing, could not be sued directly for obligations incurred within the scope of the appointment.
Common Confusion
INSTITOR vs. EXERCITOR: The exercitor was a counterpart figure in maritime commerce — the person who fitted out and operated a ship for trade. The actio exercitoria ran against the ship's operator for contracts made by the ship's master (magister navis). Researchers should not conflate the two: institor governs land-based commercial agency; exercitor governs maritime operations. Both actions were praetorian and share structural similarities, but they arise from distinct commercial contexts and different titles in the Digest.
INSTITOR vs. PROCURATOR: The procurator was a general agent or manager of affairs, typically appointed by an absent principal to manage property or litigation. The institor's authority was specifically commercial and transactional — buying and selling — while the procurator's mandate was broader and often personal. The distinction matters in historical sources because the actio institoria did not extend to the procurator's acts, which required separate analysis under the actio quasi institoria or the general law of mandate.
Core Elements
The institor relationship had three operative elements recognized in the civil law:
1. Appointment (praepositio): The principal must have placed the institor in charge — expressly or by conduct — with authority to buy and sell. Without appointment, the actio institoria did not lie.
2. Commercial scope: The institor's acts binding the principal were those within the scope of the appointment. Acts outside that scope did not bind the principal under the institoria actio, though other remedies might apply.
3. Third-party reliance: The action protected those who dealt with the institor within the apparent scope of the appointment. The emphasis on third-party protection anticipates modern apparent authority doctrine.
Why It Matters in Research
INSTITOR is primarily a Roman law and civil law term. Researchers will encounter it most often in three contexts:
First, in early agency law scholarship and treatises. Story on Agency — cited directly in both Black's and Burrill's — uses the institor as a foundational historical reference point for the development of common law agency principles. Story's treatment (§§ 8, 426) is a key node for understanding how civilian concepts fed into Anglo-American agency doctrine in the nineteenth century. Researchers tracing the intellectual genealogy of apparent authority or respondeat superior will find this term at the root.
Second, in Scots law sources. Bell's Commentaries (cited in Black's 2nd Ed.) discusses institorial power in the context of Scottish commercial law, which received Roman law influence more directly than English common law. The Law Mind corpus's Scottish materials may use institor and institorial power as live terms rather than historical curiosities.
Third, in comparative and historical legal scholarship. Any corpus material engaging with Roman commercial law, the Digest, or the praetorian actions will use institor as a technical term. Burrill's definition, drawn directly from the Digest (14.3.18) and Heineccius, is the most precise starting point for understanding what the sources mean.
Researchers should note that institor does not appear in common law cases as operative legal vocabulary — it functions as a scholarly and comparative reference, not a pleading or statutory term in English or American law.
Historical Dictionary Support
Black's (1st and 2nd editions) and Burrill's converge on the core meaning but differ usefully in depth. Black's gives a compressed definition — "a clerk in a store; an agent" — that is accurate but thin. Burrill's is substantially richer, drawing on the Digest text directly and distinguishing between the fixed-location and at-large forms of the institor's authority. For research purposes, Burrill's is the more useful entry.
Black's 2nd Ed. adds significant value by including the derivative terms INSTITORIA ACTIO and INSTITORIAL POWER, making explicit the remedial structure that gives the institor concept its legal significance. The cross-reference to Story on Agency in both Black's and Burrill's confirms that nineteenth-century common lawyers treated the institor as the civilian ancestor of the commercial agent, not merely an antiquarian curiosity.
None of the historical dictionaries address the institor's relationship to the actio exercitoria or to quasi-institorial liability — gaps that matter for researchers working with fuller Roman law sources or comparative treatments.
Jurisdictional Note
The institor as a legal category has no operative role in modern American or English common law. It remains a live concept in civil law systems and in Scots law. Researchers using Law Mind materials on Roman law, Louisiana law, Quebec law, or Scottish commercial law may encounter institor as a functional rather than merely historical term.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Agency (Historical Development); Roman Law (Commercial Actions); Respondeat Superior (Origins)