 Does doctrinal analysis implicitly or explicitly rely on some theory of law? It might be understood in a number of ways. It might be understood as the content claim (claim II) that holds that an efficiency criterion identifies the content of the law. The literature contains arguments that virtually every (common law) legal rule is efficient. This claim has both an empirical interpretation that each legal rule induces efficient behavior and a doctrinal interpretation that the prevailing legal rule is identified by its efficiency. The literature, however, has offered scant explanation or justification for the underlying theoretical claim that efficiency identifies the content of these legal norms. On what theory of law does efficiency become a ground of law?