Yale law professor Ian Ayres opens his American Contract Law course with Hamer v. Sidway, the classic nineteenth century case about an uncle's promise to pay his nephew for giving up drinking, swearing, and gambling until age twenty one. Ayres uses the case to introduce the doctrine of consideration, explaining why the court found the nephew's forbearance to be a legally sufficient bargained-for exchange rather than a mere gift. He walks through the New York Court of Appeals reasoning, addressing the common objection that giving up vices benefited the nephew rather than costing him anything. The lecture is drawn from Ayres' Coursera course and sets up the foundational question the rest of the course returns to: what makes a promise enforceable. It runs thirteen minutes and functions as a compact case study rather than a full survey of contract doctrine.