Definition
A person appointed to hear and decide a controversy between parties. The term carries two distinct senses in legal usage:
1. General sense: A neutral third party selected by disputing parties to resolve their dispute — synonymous in modern usage with arbitrator or referee.
2. Roman law sense: A judge appointed by the praetor to decide cases classified as bona fidei (good faith) actions, with authority to judge according to principles of equity (ex aequo et bono). Distinguished from the judex, who was bound to apply strict law without discretionary departure.
A third, now largely obsolete, distinction once drawn in English legal writing: an arbiter was said to be bound by rules of law and equity, whereas an arbitrator could proceed entirely on personal judgment, constrained only by the standard of a reasonable, sound-minded person. This distinction has not survived into modern practice.
Common Language
Modern common usage (Wiktionary): A person appointed or chosen by parties to determine a controversy; also, more broadly, any person or object having the power of judging or determining without limitation.
Historical common usage (Webster's 1913): A person appointed by parties to determine a controversy; also, any person whose power of deciding and governing is unrestricted.
The gap between common and legal meaning is narrow but meaningful in one direction: ordinary English uses arbiter expansively — a fashion arbiter, an arbiter of taste — to describe anyone with dominant authority over a subject. Legal usage is narrower and more formal, designating a specific role in dispute resolution. A researcher encountering arbiter in a legal source should not import the popular sense of unchecked authority; the legal context almost always implies a structured, appointment-based function.
Common Confusion
ARBITER vs. ARBITRATOR: These terms are functionally interchangeable in modern law, but historical sources draw a sharp distinction that trips up researchers reading older materials. Classical legal dictionaries — Cowell, followed by Blackstone-era commentators — held that an arbiter was bound by law and equity, while an arbitrator exercised unfettered personal discretion bounded only by reason. Bouvier expressly acknowledges this distinction and then immediately notes it is not observed in modern law. Black's reproduces the distinction without clearly signaling its obsolescence. Researchers should not assume that a historical source using arbiter rather than arbitrator is making a substantive point about the scope of the decision-maker's authority — the distinction may be purely terminological or merely archaic.
ARBITER vs. JUDEX (Roman law): In Roman law contexts, the arbiter and the judex were formally distinct. The judex applied ius strictum; the arbiter applied equity. This distinction matters when reading civil law sources or comparative law materials but has no operative significance in common law jurisdictions.
Why It Matters in Research
The primary research trap with arbiter is the artificial arbiter/arbitrator distinction preserved in historical dictionaries. Black's (both editions) and Burrill reproduce this distinction earnestly, and a researcher relying on those sources alone might conclude that a historical document using arbiter carries a specific legal meaning — namely, that the decision-maker was constrained by law — that the document's author may not have intended at all. Bouvier is the more reliable guide here: it quotes the distinction and then flags that it has collapsed in practice.
In Roman law research, arbiter is a technical term of art and the distinction from judex is genuine and substantive. The Institutes of Justinian (4.6.30–31) address this directly, and Burrill's citation of Brissoni confirms the Roman law pedigree. Researchers working in civil law, comparative law, or early American legal history (which drew more heavily on civil law in certain jurisdictions, particularly Louisiana) should treat the Roman law sense as operative.
Modern arbitration materials — statutes, rules of arbitral institutions, case law — use arbitrator almost exclusively. Arbiter appears occasionally in judicial opinions as a stylistic variant or in the general sense of a person with authority to decide, not as a term of art distinguishing that person from an arbitrator. Do not read modern judicial use of arbiter as invoking the historical distinction.
The Rapalje & Lawrence source included in the source material does not contain a relevant entry for arbiter — the excerpt provided concerns appurtenant rights and aquagium — and should not be treated as authoritative on this term.
Historical Dictionary Support
Black's (1st and 2nd editions) and Burrill are in agreement on the Roman law definition and cite consistent authority (Justinian's Institutes 4.6). All three reproduce the arbiter/arbitrator distinction drawn from Cowell without resolving whether it retains operative force.
Bouvier is uniquely candid: it states the distinction and then cites Russell on Arbitrators for the proposition that the distinction is not observed in modern law. This is the most practically useful note in the historical sources and is the one most likely to be overlooked by a researcher who reads only Black's.
Burrill adds value for Roman law research, citing both the Institutes and Brissonius, giving the term its civil law grounding in more detail than the other dictionaries provide.
None of the historical dictionaries squarely address the modern American arbitration framework that emerged through the Federal Arbitration Act era. They are useful for understanding terminology in pre-twentieth-century materials but should not be read as describing the law of arbitration as it now operates.
Jurisdictional Note
In Louisiana and other jurisdictions with civil law heritage, the Roman law distinction between arbiter and judex retains some analytical relevance in historical legal materials. In all common law jurisdictions, arbiter and arbitrator are interchangeable in modern usage, and no substantive legal consequence turns on the choice of term.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Arbitration — History and Foundations; Alternative Dispute Resolution