Definition
A Latin term of legal argumentation meaning "put" or "suppose." Used in legal reasoning to introduce a hypothetical or stated premise — essentially, "given that" or "assuming that." When a court or advocate employs *posito*, they are stipulating a condition or factual assumption for the sake of argument, then drawing a legal conclusion from it.
The term appears most commonly in the maxim *posito uno oppositorum, negatur alterum* — "one of two opposite positions being affirmed, the other is denied." This is a principle of logical necessity: where two propositions are mutually exclusive, the affirmation of one entails the negation of the other. It is a maxim of legal logic rather than a rule of substantive law.
Common Confusion
*Posito* should not be confused with *positum*, which carries similar grammatical roots but appears in different doctrinal contexts. Neither term should be conflated with the English procedural concept of "position" in the sense of a party's legal stance, though the conceptual lineage is related. *Posito* is a term of logical form, not of substantive pleading or procedure.
Why It Matters in Research
Researchers working in early English case law, particularly in the Year Books and the early modern reporters, will encounter *posito* embedded in argument sections — often introduced by counsel or recorded in the voice of a judge presenting a hypothetical. It is rarely a term of art carrying its own doctrinal weight; rather, it is a rhetorical and logical marker that signals the structure of the argument being made.
The maxim *posito uno oppositorum, negatur alterum* has particular importance: in historical legal sources, it appears as a shorthand for what modern lawyers would recognize as the principle of non-contradiction applied to legal positions. When encountered in a reporter, it usually signals that the court or advocate is collapsing an opponent's position by showing its logical incompatibility with a conceded premise. Understanding this function prevents misreading the passage as a statement of substantive law.
Because *posito* appears almost exclusively in Latin-language legal argument, it is largely absent from post-18th century common law sources as English displaced Latin in pleading and judicial reasoning. Researchers should not expect to find it in modern materials. Its presence is a reliable indicator that the surrounding text is from pre-1730 English legal literature or from sources deliberately drawing on that tradition.
The cross-reference in Burrill to Coke's argument in 2 Leonard 176 and to Keilwey 68 places *posito* firmly in the late Year Book and early reporter tradition. Researchers using these reporters should be alert to the distinction between the prefatory *posito* (marking a hypothetical) and the substantive legal rule that follows from it — the two are logically connected but textually distinct.
Historical Dictionary Support
Burrill is the primary historical authority available for this term. His entry is brief but precise: he supplies the Latin sense (put, suppose), identifies the logical structure of the maxim *posito uno oppositorum, negatur alterum*, and cites 3 Rolle's Reports 422 as authority. The entry does not attempt to elevate the term beyond its function as a logical marker.
No substantive disagreement exists among historical sources on this term because it is primarily a term of Latin legal logic rather than a disputed doctrine. What historical dictionaries tend to underserve is the *practical* function of *posito* in argumentation — Burrill records what it means but does not explain how it operates rhetorically in the reporters. Researchers should treat the term as a structural signal within an argument, not as a self-contained legal rule.