Definition
Cosas comunes (Spanish: "common things") is a concept from Spanish civil law denoting things that by their nature are open to the equal and common enjoyment of all persons and incapable of reduction to private ownership. The category encompasses resources such as air, the sea, and the water of running streams — things whose use is shared universally and which no individual or sovereign may appropriate exclusively.
The concept is the Spanish-law counterpart to the Roman law category of res communes, and carries substantially the same meaning: things that exist outside the bounds of property law not because they are ownerless in the ordinary sense, but because their nature makes private dominion incompatible with their public character.
Common Language
Modern common usage (Wiktionary): "Cosas comunes" translates literally as "common things" or "shared things" in everyday Spanish, used generally to mean objects, topics, or attributes held in common by a group.
Historical common usage (Webster's 1913): No direct entry. "Common" in Webster's 1913 carries meanings including "belonging to many" or "public," with "commons" referring to land open to shared use by a community.
The gap between ordinary usage and legal meaning is specific and important: in everyday Spanish, "cosas comunes" might describe any shared items, from household goods to conversational topics. The legal term is a formal category of property jurisprudence, not merely a description of shared use. It denotes things incapable of private ownership as a matter of law — a structural feature of the property system, not a practical arrangement subject to change.
Common Confusion
Cosas comunes should not be confused with closely related but distinct categories in Spanish and civil-law property systems:
— Res nullius (things belonging to no one) are ownerless but capable of acquisition through occupation. Cosas comunes are not ownerless — they belong to all — and cannot be acquired privately.
— Bienes públicos (public property) are owned by the state and administered for public use. Cosas comunes are not owned by the state; they are outside ownership entirely.
— Common property in Anglo-American law typically refers to co-ownership arrangements (joint tenancy, tenancy in common) — a completely different concept. Researchers encountering "common things" in translated Spanish or Mexican legal materials should not read Anglo-American co-ownership doctrine into the term.
Why It Matters in Research
This term appears primarily in sources dealing with Spanish colonial law, Mexican law, and Western water rights — not in general Anglo-American common law materials. Its significance in the Law Mind corpus is concentrated in two areas.
First, California and the Southwest: The leading American case engaging cosas comunes doctrine is Lux v. Haggin (Cal. 1886), a foundational water rights decision that turned in part on the character of running water under Spanish and Mexican law as it existed before California statehood. Researchers working on riparian rights, prior appropriation, or the transition from Spanish/Mexican land tenure to American property law will encounter this term in that context. The doctrine mattered because pre-statehood land grants and water uses were evaluated against the law in force at the time — and under that law, running water was a cosa común, not subject to prior private appropriation.
Second, water law genealogy: The classification of running water as a cosa común (and its Roman-law ancestor, res communes) is the conceptual root from which Anglo-American riparian rights doctrine partially descended. Understanding cosas comunes clarifies why early California courts treated water differently than courts in eastern states, and why the shift to prior appropriation doctrine was treated as a break from received law rather than a continuation of it.
Trap for researchers: Do not assume that because something was classified as a cosa común under Spanish or Mexican law, it remains legally inalienable under American law. The transition to American sovereignty altered the applicable legal framework. The historical classification matters for resolving pre-statehood rights; it does not automatically constrain post-statehood legislation.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) provides a compact but adequate entry, correctly identifying cosas comunes as the Spanish-law equivalent of the Roman res communes and listing air, the sea, and running water as the canonical examples. The entry cites Hall's Mexican Law and Lux v. Haggin — both appropriate anchors for this doctrine in the American legal context.
What Black's does not address: the internal distinctions within Spanish property classification that surrounded cosas comunes — including bienes públicos, bienes comunes del pueblo (things common to the people of a municipality), and realengo (crown lands). These distinctions mattered in land grant litigation and are not recoverable from the Black's entry alone. Researchers needing the full taxonomy should consult Hall's Mexican Law directly or period treatises on Spanish colonial law.
No other dictionary in the current Law Mind shelf provides an entry for this term, reflecting its status as specialized vocabulary for a specific historical and jurisdictional context rather than general Anglo-American common law.
Jurisdictional Note
This term is operative primarily in states whose legal history includes Spanish or Mexican sovereignty — California, Texas, New Mexico, Arizona, and other parts of the Southwest. Its relevance in those jurisdictions is historical rather than contemporary: it bears on the interpretation of pre-statehood grants, water rights, and land titles. Researchers outside that geographic and historical context are unlikely to encounter it.