Lionel Smith, ‘Defences and the Disunity of Unjust Enrichment’

This paper was given at a conference on defences in the law of unjust enrichment. For over thirty years, the question has been lurking in the common law whether there is a single cause of action in unjust enrichment, or rather multiple causes of action with broadly similar features. Is unjust enrichment a unity, governed by a single principle albeit with many manifestations? Or, is it a general idea that describes a range of principles with different normative contents? The paper aims to answer this question. In the common law, the question has often been asked (but rarely answered) in terms of whether unjust enrichment is a single cause of action, or includes multiple causes of action. The paper approaches this question by way of an analysis, informed by comparative law, of what exactly ‘cause of action’ means. The intermediate conclusion is that the phrase includes three distinct concepts: the facts that generate a claim; the general norm that creates a claim when those facts exist; and the particular claim that exists between the parties. On this view, it is argued that unjust enrichment includes multiple causes of action. A project for the common law is to better understand what unifies and what differentiates those causes of action.

Smith, Lionel, Defences and the Disunity of Unjust Enrichment (January 24, 2015), ch 2 in A Dyson, J Goudkamp, and F Wilmot-Smith, eds, Defences in Unjust Enrichment (Oxford, Hart, 2016).

First posted 2015-12-01 06:46:42

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