The paper discusses some conceptual issues which arise in the context of economic analysis of legal rules. It is argued in the paper that there does not seem to be any appropriate justification for the almost exclusive preoccupation of economic analysis of law with the normative criteria of efficiency. The paper also argues that on the basis of the results of law and economics literature which have been obtained regarding the efficiency of laws, rules and doctrines of common law the claim that efficiency constitutes a unified explanation for common law is not easy to maintain.