Yale law professor Ian Ayres continues his American Contract Law course with a lecture on nominal consideration and its historical substitutes. He walks through the doctrine of consideration as a gatekeeper for enforceable promises, then turns to the seal, the formal wax or symbolic mark that once let parties bind themselves without any bargained exchange. Ayres explains how courts treated sealed instruments as evidence of deliberate intent to contract, and how the Model Written Obligation Act tried to modernize that function by letting a signed writing itself substitute for consideration. The lecture traces why these formalities mattered before consideration hardened into doctrine, and what functions they served that bargained-for exchange does not. Drawn from Ayres' Coursera course American Contract Law I, the talk runs about fourteen minutes and assumes some familiarity with the consideration requirement covered in earlier sessions.