Definition
Mercis appellatio is a Latin maxim from Roman law meaning, literally, "the designation of merchandise." It encompasses two distinct legal propositions drawn from the Digest of Justinian:
1. Mercis appellatio ad res mobiles tantum pertinet — The term "merchandise" applies to movable things only. Goods, wares, and commodities subject to trade are confined to personal, movable property; immovable property (land and things fixed to land) falls outside the scope of "merchandise."
2. Mercis appellatione homines non contineri — Human beings are not included within the denomination of "merchandise." Persons are categorically excluded from the legal classification of goods or tradeable commodities, even within a legal system that recognized slavery.
Together, these maxims define the outer boundaries of the Roman law concept of merx (merchandise or goods): bounded below by the requirement of movability and bounded above by the exclusion of persons from the category of things.
Common Confusion
The second proposition — that persons are not "merchandise" — may seem paradoxical to a researcher who knows that Roman law permitted slavery and that enslaved persons could be bought and sold. The maxim does not deny that human beings were subject to commercial transactions; it means that the technical legal category of merx, with its specific rules governing commercial obligations, warranties, and trade, did not formally encompass persons. Separate legal frameworks governed transactions involving enslaved individuals. The maxim is a classification rule, not an abolition principle.
Why It Matters in Research
Researchers working in Roman law, civil law tradition, or the history of commercial law will encounter this maxim as a foundational boundary-setting rule for what counts as goods in contractual and trade contexts. Its significance branches in two directions:
First, the movables-only rule (res mobiles tantum) is an ancestor of the goods/land distinction that runs through civil law systems and, in modified form, through common law commercial law. When tracing the intellectual lineage of definitions of "goods" in later codes — including the Uniform Commercial Code's exclusion of real property or the civilian treatment of immovables — this maxim is a useful upstream reference point.
Second, the exclusion of persons maxim has attracted attention in historical and jurisprudential scholarship on slavery and legal personhood. Researchers should be careful not to read the maxim anachronistically as a proto-abolitionist statement. Its function in the Digest is taxonomic, not humanitarian. Overreading it in either direction — as endorsing commodification or as condemning it — misrepresents its doctrinal role.
The maxim appears in secondary sources on Roman commercial law and in treatises on the civil law foundations of Anglo-American commercial doctrine. It is unlikely to appear in common law case law directly, but may surface in scholarly commentary, comparative law materials, and civil law jurisdiction sources.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) presents both propositions together under the heading Mercis appellatio, citing the Digest of Justinian at 50.16.66 and 50.16.207 respectively. Black's treatment is purely definitional — it translates the maxims and provides the Digest citations without commentary on their doctrinal application or historical context. This is characteristic of Black's handling of Roman law maxims in the second edition: faithful transmission, minimal interpretation.
Researchers should note that Black's 2nd Ed. does not address the tension between the second maxim and Roman slavery law, nor does it connect the first maxim forward to later commercial law codifications. Both are genuine gaps for any researcher using Black's as a starting point. The Digest citations (Dig. 50.16.66 and Dig. 50.16.207) are reliable and traceable to Book 50, Title 16 of the Digest — the title De verborum significatione (On the Meaning of Words), which is itself a rich source for Roman legal definitions and a productive area of research for anyone tracing the vocabulary of classical Roman law into later legal traditions.
Jurisdictional Note
This is a Roman law maxim with no direct operative force in common law jurisdictions. Its relevance in modern research is historical and comparative. Civil law jurisdictions descending from Roman law tradition (France, Spain, Louisiana, Quebec) may reflect its substance in statutory definitions of movable property and goods, but the maxim itself is a scholarly reference point rather than an enforceable rule.