R2d § 86
Promise for Benefit Received
A promise made in recognition of a benefit previously received by the promisor from the promisee is binding to the extent necessary to prevent injustice. The promise is not binding if the promisee conferred the benefit as a gift or for other reasons the promisor has not been unjustly enriched, or if the value of the promise is disproportionate to the benefit.
Professor's notes
Elements: (1) a promise made in recognition of a benefit previously received is binding to the extent necessary to prevent injustice; (2) NOT binding if (a) the benefit was conferred as a gift or no unjust enrichment occurred, OR (b) the value promised is disproportionate to the benefit.
Webb v. McGowin operationalizes the rule: life saved at grave personal cost is a material benefit; subsequent promise enforceable.
Mills v. Wyman shows the limit: care for an adult son confers no benefit on the father (no enrichment to him), so the father's subsequent promise fails.
Common misunderstanding: students collapse § 86 with § 90. § 90 protects reliance on a forward-looking promise; § 86 enforces a backward-looking promise for past benefit. Different time, different rationale.
Cases that operationalize this rule
Section 86 codifies the material-benefit rule that Webb v. McGowin anchors. It enforces a subsequent promise to pay for a benefit conferred without prior bargain: provided the benefit was substantial, the promisee did not act gratuitously, and the promised amount is not disproportionate. The doctrine is the principal exception to the past-consideration bar of Mills v. Wyman.