Yale law professor Ian Ayres covers the doctrine of consideration in this segment from his American Contract Law course, originally developed for Coursera. The lecture works through Kirksey v. Kirksey, the classic case in which a widow moves her family sixty miles at her brother-in-law's urging after he promises her a home, only to be evicted later with no legal remedy because the promise lacked bargained-for consideration. Ayres uses the case to distinguish a bare promise from a promise backed by consideration, explaining why the widow's inconvenience in relocating did not count as the kind of exchange contract law requires. The talk is short and focused, aimed at students building up the doctrinal building blocks of offer, promise, and consideration before moving into its substitutes.