Definition
Causa turpis (Latin: "base cause" or "shameful cause") is a doctrine in contract and obligation law holding that a cause or consideration grounded in immorality or illegality is void and unenforceable. Where the underlying basis of a contract or transaction is causa turpis, courts will refuse to aid either party — not to punish the parties, but because courts decline to lend their authority to agreements rooted in conduct contrary to public morals or law.
The doctrine operates as a complete bar to enforcement. A party cannot sue to recover on a contract, nor typically to recover money or property already transferred under it, when the foundation of the agreement is turpis — base, vile, or illegal. This connects to the broader maxim ex turpi causa non oritur actio: no right of action arises from a shameful cause.
Common Confusion
Causa turpis is often encountered alongside causa mortis and causa consideration in research, and the Latin structure invites conflation. These are unrelated concepts. Causa mortis describes a gift made in anticipation of death (see ENCYCLOPEDIA CROSS-REFERENCE below). Causa turpis describes a corrupt or immoral basis for an obligation. The shared word causa means only "cause" or "reason" — the modifier (mortis, turpis) carries all the legal weight. Researchers encountering causa in historical sources should identify the full phrase before drawing conclusions about the doctrine being discussed.
Causa turpis also should not be conflated with failure of consideration. Failure of consideration means a valid, lawful consideration simply was not performed. Causa turpis means the consideration itself was illegal or immoral from the outset — a more fundamental defect that ordinarily bars any recovery whatsoever, including restitution.
Why It Matters in Research
The phrase appears most frequently in historical sources — equity treatises, early common law reports, and civil law commentaries — and its direct invocation in modern American case law is relatively sparse. Researchers may find causa turpis cited as the Latin foundation for what modern courts express as the illegality defense or the in pari delicto doctrine. Knowing the Latin phrase unlocks older treatise discussions that modern keyword searches will miss entirely.
The companion maxim quoted in Black's — causa vaga et incerta non est causa rationabilis ("a vague and uncertain cause is not a reasonable cause") — appears in legal sources as a distinct proposition about certainty of consideration, not about immorality. These two maxims appear in proximity in historical texts but address different problems. Conflating them in research leads to doctrinal error.
In civil law jurisdictions and in international commercial arbitration sources, causa turpis retains more active doctrinal life than in Anglo-American common law, where the same policy is typically expressed through illegality, public policy, and in pari delicto analysis. Researchers working across civil and common law traditions should trace both the Latin doctrine and its functional equivalents in each system.
Historical equity sources, particularly Chancery materials, use the doctrine to explain why courts of conscience would deny relief even where the legal right was technically established. The moral dimension is deliberate: turpis implies not merely illegality but a quality of baseness or indecency that offends the court's conscience.
Historical Dictionary Support
Black's Law Dictionary defines causa turpis as a "base (immoral or illegal) cause or consideration" and pairs it with the Coke maxim on vague and uncertain causes. The entry is brief, consistent with Black's treatment of Latin maxims as reference anchors rather than doctrinal expositions.
Black's entry does not address the relationship between causa turpis and in pari delicto, the procedural question of whether recovery is barred in full or only partially, or the civil law origins of the doctrine. Researchers should treat the Black's entry as a starting point and consult equity and contract treatises for substantive depth. The doctrine's Roman law roots — turpis causa in Roman contract theory rendering stipulations void — give it a longer doctrinal history than Black's brief entry suggests.
Jurisdictional Note
In American common law, causa turpis is not typically invoked by name in modern opinions; courts instead apply illegality and in pari delicto doctrine to reach the same result. Civil law jurisdictions, including Louisiana, and systems derived from Roman law traditions more frequently use the causa framework explicitly. Researchers working in Louisiana law should be attentive to the civil law meaning of causa generally, which differs structurally from common law consideration doctrine.
Encyclopedia Cross-Reference
The Law Mind Property Law Encyclopedia: Personal Property — Gifts (Inter Vivos, Causa Mortis — Delivery, Intent, Acceptance) [property_133] — relevant for distinguishing causa turpis from causa mortis and understanding how "causa" functions differently across legal contexts.