ABSTRACT. Posner affirms that even if the goal of contract law is to promote efficiency rather than to enforce promises as such, enforcing the parties' agreement insofar as it can be ascertained may be a more efficient method of attaining this goal than rejecting the agreement when it appears to be inefficient. Schwartz and Scott contend that contract law has neither a complete descriptive theory, explaining the law that is, nor a complete normative theory, explaining the law that should be. Katz maintains that the growth of electronic commerce reflects changes in the relative importance of various institutional transaction costs such as the costs of information and of searching for contractual partners.