Subrogation and unjust enrichment in the High Court of Australia
By means of the doctrine of subrogation, one person is substituted for another in the exercise of that other’s rights against a third person. In the classic triangular fact pattern, it arises where a creditor has rights against a debtor, and the plaintiff is subrogated to the rights of the creditor against the debtor. It is a doctrine which admits of many possible explanations. For example, on the view taken by Meagher, Gummow & Lehane, subrogation largely follows a similar pattern in a series of otherwise unconnected islands: they are content to set out the categories, which, for them, are not closed, and to conclude that there are no universally applicable criteria for the intervention of equity in such cases. On another view of subrogation, taken by Hedley, and by Lord Salmon in Orakpo v Manson Investments [1978] AC 95 (HL), there are some relatively loose connections between the specific contexts but only at an abstract level: Hedley argues for a broad general principle that (subject to defences) the plaintiff can exercise whatever rights the creditor would, but for the plaintiff’s payment, have had against the debtor; whilst Lord Salmon argued for an “entirely empirical … principle … that the doctrine will be applied only when the courts are satisfied that reason and justice demand that it should be”.…