Passage:
In private law jurisprudence, the theoretical grounding of claims arising from unjustified enrichment has historically divided civilian and common law traditions. In English common law, the law of restitution was long subsumed under the procedural fiction of 'implied contract' or quasi-contract, tracing back to the landmark eighteenth-century decision in Moses v. Macferlan. Under this framework, liability was rationalized through an imputed promise to repay, thereby anchoring restitutionary relief within the familiar architecture of assumpsit. It was not until the late twentieth century, following the foundational scholarship of Robert Goff and Gareth Jones and the judicial repudiation of the implied contract theory in Lipkin Gorman v. Karpnale Ltd, that English law formally recognized unjustified enrichment as an independent source of obligations distinct from contract and tort. Even with this recognition, however, English law adopted an 'unjust factors' methodology. Under this approach, a claimant must identify a specific, recognized substantive reason—such as mistake of fact, duress, failure of consideration, or undue influence—rendering the defendant's retention of a benefit unjust, rather than demonstrating a general absence of legal cause.
Conversely, Scots law, operating as a mixed legal system deeply rooted in the Romanist civilian tradition, historically approached enrichment through a unitary conceptual structure. Drawing directly on the Justinian Digest and institutional writers such as Lord Stair and John Erskine, Scots jurisprudence categorized enrichment claims not through transactional fictions of implied agreement, but through distinct civilian actions: the condictiones (such as the condictio indebiti for recovery of payments made in error, and the condictio causa data causa non secuta for transfers where the anticipated future basis failed) and the actio de in rem verso. Rather than searching for an idiosyncratic 'unjust factor,' the Scots civilian approach historically evaluated whether an enrichment occurred 'sine causa'—that is, without a recognized legal ground or justification. Under the sine causa model, once an enrichment at the claimant's expense is established, retention is prima facie impermissible unless the defender can establish an extant juridical basis, such as a valid contract, statutory authorization, or donative intent.
Statement:
According to the passage, prior to the late twentieth century, English common law rationalized restitutionary liability through the legal fiction of an imputed promise to repay rather than recognizing unjustified enrichment as an independent category of obligation.
Answer: Answer