Professor James Gordley opens this volume with a concise history of the legal status of promises. In the central part of the book legal experts examine how twelve modern European legal systems deal with fifteen concrete situations in which a promise may not be enforceable--situations that include gifts, loans, bailments, houses, rewards, and brokerage contracts. Despite differences in legal doctrine, the volume reveals similarities in the results. This is the second completed project of The Common Core of European Private Law launched at the University of Trento.