Definition
DIVERSITY carries two distinct legal meanings that operate in entirely separate areas of law. Researchers must distinguish them carefully, as the historical sources cover only one while modern practice centers on the other.
1. Diversity of citizenship (federal jurisdiction). The condition in which adverse parties to a lawsuit are citizens of different U.S. states (or one is a foreign national), conferring subject-matter jurisdiction on federal district courts under Article III of the Constitution and, by statute, 28 U.S.C. § 1332. To invoke diversity jurisdiction, complete diversity must exist — no plaintiff may share state citizenship with any defendant — and the amount in controversy must exceed the statutory threshold (currently $75,000). This is the dominant modern legal use of the term.
2. Diversity (criminal pleading, historical). A common law plea in bar of execution, entered by a condemned prisoner who claimed to be a different person from the one attainted. The issue raised — identity, not guilt — was tried immediately by a jury. Conviction on the attainder was already established; the only question was whether this prisoner was that person. The plea is effectively obsolete.
Common Language
Modern common usage (Wiktionary): The quality of being diverse or different; variety; in contemporary usage, often refers to equal-opportunity inclusion across demographic groups.
Historical common usage (Webster's 1913): A state of dissimilitude or unlikeness; multiplicity of difference; variety of kind.
The gap between common and legal meaning is sharp in two directions. The common modern sense of "diversity" — demographic representation and inclusion — has no bearing on either legal usage. The jurisdictional sense turns on citizenship difference between parties, a narrow technical condition with nothing to do with variety or social inclusion. The historical pleading sense turns on identity, not difference in any ordinary sense at all.
Common Confusion
Three uses of "diversity" circulate in legal contexts and are easily conflated:
— Diversity of citizenship (jurisdictional diversity) is the federal court basis for hearing disputes between citizens of different states. This is the operative meaning in modern federal civil procedure.
— Diversity (criminal plea) is the historical identity plea described above. It appears in Blackstone and early pleading treatises but has no modern procedural equivalent. Encountering the term in pre-twentieth-century criminal law sources almost certainly means this plea, not citizenship jurisdiction.
— Diversity in the social/institutional sense — diversity of workforce, bench, bar, or jury pool — is a policy and constitutional concept addressed in equal protection and antidiscrimination law. It is not a term of art in the jurisdictional sense and should not be read as one.
Core Elements
For diversity jurisdiction (the modern usage), the doctrine has two required components:
Complete diversity of citizenship. Every plaintiff must be a citizen of a different state from every defendant. Citizenship for individuals is determined by domicile. Citizenship for corporations is determined by both state of incorporation and principal place of business. Unincorporated associations present complications courts have resolved inconsistently.
Amount in controversy. The claim must exceed the statutory threshold (currently $75,000, exclusive of interest and costs) as set by Congress under 28 U.S.C. § 1332. Aggregation rules govern multi-claim and multi-party cases.
Why It Matters in Research
The historical plea of diversity appears in the Law Mind corpus primarily in materials drawn from Blackstone's Commentaries and early English and American criminal pleading treatises. Researchers working in pre-nineteenth-century criminal procedure will encounter it in that context. It is a dead doctrine for all practical purposes, but its presence in foundational sources means it cannot be ignored when reading historical criminal law materials.
The jurisdictional meaning dominates every modern source. The Law Mind Civil Procedure corpus contains substantial treatment of diversity jurisdiction's requirements, traps, and limits. The complete diversity rule — not present in the constitutional text but established by long-standing doctrine — is a frequent source of confusion in multi-party litigation research. Researchers should also note that Congress can and has modified diversity jurisdiction by statute (e.g., the Class Action Fairness Act of 2005 altered the complete diversity requirement for certain class actions), so the statutory framework must be checked alongside the doctrinal rules.
The two meanings do not bleed into each other in any source, but the single word "diversity" appearing without context in an older treatise or encyclopedia entry should prompt the researcher to identify which usage is intended before proceeding.
Historical Dictionary Support
Black's Law Dictionary (both editions) and Rapalje & Lawrence treat diversity exclusively as the criminal pleading plea. This is a significant gap: the historical dictionaries do not address diversity of citizenship at all, despite federal diversity jurisdiction existing since the Judiciary Act of 1789. The omission reflects the focus of those dictionaries on common law pleading doctrine rather than federal statutory jurisdiction, and it means researchers relying solely on historical dictionary sources for "diversity" will receive an incomplete — and potentially misleading — picture of the term's legal importance.
Both Black's editions reproduce the Blackstone citation (4 Bl. Comm. 396) nearly verbatim, suggesting the criminal pleading definition was transmitted from Blackstone without independent development. Rapalje & Lawrence dispatch the term with a cross-reference to "collateral," offering no independent analysis.
Jurisdictional Note
Diversity of citizenship jurisdiction is exclusively a federal doctrine; state courts have no counterpart requirement. Significant variation exists in how courts assess corporate citizenship, citizenship of LLC members, and the citizenship of class members under the Class Action Fairness Act. Researchers working on multi-party or class action matters should not assume the standard complete diversity rule applies without checking the specific statutory and procedural framework governing that case type.
Encyclopedia Cross-Reference
Diversity Jurisdiction — 28 USC 1332, Complete Diversity, and Amount in Controversy (The Law Mind Civil Procedure & Evidence Encyclopedia) [civpro_3]