Many common-law practitioners should be familiar with the competing theories on how to conceptualise the law of unjust enrichment.

Is the law still confined to an 'unjust factors' approach as recently reiterated by Lord Sumption in Test Claimants in the FII Group Litigation v HMRC [2012] 2 AC 337 [162] (UKSC).

It is necessary, as the law presently stands, to bring the facts within one of the categories of case in which the law recognises that the recipient's retention of the money would be unjust.

Or should the late Peter Birks approach of an 'absence of basis' being the foundation of an unjust enrichment claim be given more merit? (See his 2005 book, Unjust Enrichment.) The approach seems to be rather successful in other jurisdictions such as the German courts.

META: I do not feel this is a question of opinion per se. This is serious academic discussion on a developing area of law, which imho should be the primary focus of discussion on Law.SE, and not questions on substantive answers/legal solutions to specific problems.

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    I don't know anything about this area of law, but as a comment on the question itself, I wonder if it would be more objectively answerable if you ask: "Based on case law precedents, which approach is more likely to succeed?"
    – Dom
    Jun 2, 2015 at 18:08
  • German and English (Common) law are entirely different legal traditions and what works in one would be a poor guide as to what works in the other.
    – Dale M
    Jul 13, 2015 at 4:07
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    I want to comment to visibly support the notion that more Law.SE questions should deal with theoretical, academic, and developing areas of law. Jan 3, 2016 at 15:17

1 Answer 1


Some arguments hold that "unjust factors" has founded on a vague conceptualization of unjust enrichment situations, as occurs at the beginning of all areas of practice.

"Absence of basis" reasoning presents a specific condition by which determination can occur. A 'basis' can exist, or not, and when present the basis derives from rights that – ideally – have definition external to the matter of the case.

If "Absence of basis" reasoning comes to take the primary position in arguments, then "unjust factors" arguments can remain as supportive or secondary matters of the claim. Conversely, saying there exists "unjust factors" but not arguing that an "absence of basis" exists... could seem contradictory.

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