Definition
Latin: "The reason is open" or "the cause is plain." A formulaic Latin phrase used in legal writing to signal that the rationale or basis for a statement, rule, or conclusion has already been made clear — either from what preceded it or from the circumstances themselves. It functions as a shorthand acknowledgment that no further explanation is required because the reason is self-evident from context.
The phrase appears in two primary forms:
1. CAUSA PATET — The reason is open, obvious, plain, clear, or manifest. Used as a standalone declaration in legal texts and instruments to indicate that the grounds for a proposition are apparent without elaboration.
2. CAUSA PATET EX PRAEMISSIS — The reason is plain from the premises. A more specific variant asserting that the rationale follows necessarily from what has already been stated or established.
A related but distinct phrase, CAUSA SCIENTIAE PATET (the reason of the knowledge is evident), carries a narrower technical meaning in Scots law practice, appearing in witness depositions to attest that the basis for a witness's knowledge is apparent from the deposition itself.
Common Confusion
CAUSA PATET should not be confused with CAUSA MORTIS or CAUSA in its standalone sense. CAUSA alone translates broadly as "cause," "reason," or "case" and appears in dozens of distinct Latin legal maxims. CAUSA PATET is not a statement about the nature of a legal cause but a stylistic declaration about the self-evidence of reasoning. Researchers encountering CAUSA in old instruments should read the full phrase before assuming meaning.
Why It Matters in Research
This term is primarily a research navigation problem rather than a substantive legal concept. Encountering CAUSA PATET in a primary source — a deed, pleading, or treatise — signals that the author considered the point already established. For researchers reconstructing the logic of an old instrument or argument, this phrase is a structural marker, not a legal conclusion. It tells you to look backward in the document, not forward, for the operative reasoning.
The phrase is largely confined to early modern English legal literature. Its primary reference point in the historical dictionaries is Perkins's treatise (Perkins on Conveyancing), a widely circulated English work from the sixteenth century. Researchers working in property law, conveyancing, or early common law pleading are the most likely to encounter it.
The CAUSA SCIENTIAE PATET variant is jurisdiction-specific to Scots law and appears in a deposition context. Researchers working with Scottish court records or comparative common law sources should treat this as a distinct technical term with procedural significance — it is not merely stylistic but attests to the basis of a witness's knowledge, which has evidentiary implications. Do not carry the English usage into Scottish materials or vice versa.
Because the phrase signals self-evidence rather than asserting a substantive rule, it is easy to misread as meaningful legal content. In context, it typically means the author declined to state the obvious. Modern researchers should resist inferring more from the phrase than is there.
Historical Dictionary Support
Black's and Burrill's entries are in close agreement. Both translate the phrase identically and anchor it to the same source — Perkins, chapter one. Burrill adds the companion phrase CAUSA PATET EX PRAEMISSIS with a citation to Perkins chapter three, and uniquely identifies the CAUSA SCIENTIAE PATET variant from Scots practice. Black's omits the Scottish variant entirely.
Neither dictionary offers substantive analysis beyond translation and attribution. This is appropriate given the phrase's nature as a formulaic expression rather than a doctrine. Researchers should not expect depth in historical sources on this term; both dictionaries treat it as a glossary entry rather than a concept requiring extended treatment.
What the historical dictionaries do not address is the phrase's disappearance from modern legal writing. It survived in Latin legal literature through the early modern period but does not appear in contemporary drafting or judicial opinions. Its presence in a document is itself a dating signal.
Jurisdictional Note
CAUSA SCIENTIAE PATET is a term of Scots law procedure with no direct English common law equivalent. Researchers should not assume that the English and Scottish usages of the root phrase are interchangeable. The Scottish variant carries specific evidentiary weight in deposition practice that the English formulaic usage does not.
Encyclopedia Cross-Reference
For the related doctrine of CAUSA MORTIS, which shares the root term but concerns an entirely distinct legal concept in property law: The Law Mind Property Law Encyclopedia, property_133: Personal Property — Gifts (Inter Vivos, Causa Mortis — Delivery, Intent, Acceptance).