Change and continuity in the law of unjust enrichment

• Jurisdiction: South Africa
• Citation: 2019 Acta Juridica 469
• Date: 24 December 2019
• Pages: 469-492
• Published date: 24 December 2019

469

Change and continuity in the law of

unjust enrichment

HELEN SCOTT*

The past decade has seen a marked rise in unjust enrichment scepticism

across the common-law world. Some argue that the ‘at the expense of’

element in particular has been over-generalised and that the restitution

of unjust enrichment should be principally conned to cases of

deliberate conferral by the plainti. Others go further and argue that

the law of unjust enrichment itself does not exist insofar as ‘unjust

enrichment’ is neither a cause of action nor a consideration of justice

capable of justifying restitution. This essay oers a tentative response to

these arguments, defending a performance-based analysis of core Kelly

v Solari-type cases but questioning whether the continued existence

of the subject really depends on the tight normative unity that its

critics demand. At the same time, the essay considers the ways in which

legal history, comparative law and legal theory have acted as drivers

of change in this context, examining the phenomenon of change and

continuity in private law with reference to these developments.

I INTRODUCTION

At rst glance the law of unjust enrichment seems remarkably resistant

to change. The common law has recognised a claim for the recovery

of a mistaken payment for centuries;1 its civil-law counterpart, the

condictio indebiti, can reasonably be said to be approaching its 2000th

* BA (Hons) LLB (Cape Town) BCL MPhil DPhil (Oxon); Tutorial Fellow

at Lady Margaret Hall, Professor of Private Law in the Faculty of Law, University

of Oxford, and Honorary Research Associate in the Department of Private Law,

University of Cape Town.

1 Moses v Macferlan (1760) 2 Bur r; Kelly v Solari (1841) 9 M & W 54. The

defendant’s husband, having insured his life with the A insurance company, omitted

to pay the quarterly premium due under the policy and died shortly afterwards.

One of the company’s employees advised its directors that the policy had lapsed.

However, when the defendant claimed under the policy some months later the

directors authorised payment in full. The company sought to recover this payment.

Recovery was held to turn on whether the directors had been genuinely mistaken

as to their liability to pay, or whether the money had been paid intentionally, the

directors meaning to waive all inquiry into their liability.

2019 ACTA 469

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470 PRIVATE LAW IN A CHANGING WORLD

birthday.2 Continuity on this scale suggests that the category is in

some sense immutable, presumably because it is founded on some

unshakeable moral principle. But rst impressions are misleading.

On the one hand, unjust enrichment itself is much younger than

some of its components. In the civilian context it is reasonable to

date its birth to the rst half of the seventeenth century, making it

the youngest in the obligations family by several millennia. In the

common-law world, on the other hand, it is a child of the twentieth

century. Moreover, its boundaries are far from immutable: not

only do they dier between jurisdictions; they are also contested

within individual legal systems. Scholars of common-law unjust

enrichment disagree about its taxonomy: over the course of the

past decade it has been argued that the ‘at the expense of’ element

in particular suers from over-generalisation and that it should be

principally conned to cases of deliberate conferral by the plainti.

Even the core of the subject is controversial: recently it has been

argued that unjust enrichment plays no role in justifying restitution

in the central case of Kelly v Solari. In other words, the claim has

been made that unjust enrichment is not a subject at all. Far from

immutable, then, unjust enrichment turns out to be in a state of ux.

In this essay I seek to investigate the phenomenon of change in

private law with reference to these developments: in particular, I will

consider the ways in which legal history, comparative law and legal

theory have acted as drivers of change in this context. I will begin

by briey describing the terms of these debates, as well as their

implications for the South African law of unjustied enrichment,

before weighing the force of the various arguments and presenting

my own view. Finally, I will oer some more general reections on

change and continuity in the law of unjust enrichment. In all of

this I hope to pay tribute to Danie, whose ground-breaking work

on enrichment liability has always been characterised by a deep

knowledge of and sensitivity to legal history and comparative law,

and to celebrate his great contribution to the development of the

subject, both in South Africa and around the world.

2 The second-century jurist Pomponius appears to have discussed the recovery

of an indebitum solutum quite extensively in Book 22 of his Commentary on Sabinus.

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