When does the law permit you to change your mind and reverse a decision you have made? In this masterful book, one of the foremost authorities on American contract law considers the general principles and legal rules that bear on this question. Drawing on many fields--contracts, torts, property, trusts, wills, agency, and even family law and procedure--E. Allan Farnsworth identifies and discusses six such principles. Using real legal cases as well as an array of nonlegal sources ranging from Rousseau and Martin Luther to Shirley MacLaine and Willie Nelson, Farnsworth illustrates the importance of the principles that govern the irrevocability of a commitment (as by a promise) and the irreversibility of a relinquishment (as by a gift) or preclusion (as by prescription). He discusses deficiencies in the law--such as the preoccupation with the reliance principle, the neglect of other principles, the propensity to find promise, and the tendency toward legal paternalism--and offers suggestions to eliminate anomalies, correct shortcomings, and further the rationalization of the legal concepts that pertain to regretted decisions.