 I begin with the three positive claims that correspond to the disambiguation of Posner’s positive claim and the two claims that flow from economic methodology. Claim (I), the explanatory claim, asserts that common law legal rules induce efficient behavior. Claim (II), the content claim, asserts that the criterion of efficiency determines the content of the law. A positivist might understand this claim as a claim about the content of the rule of recognition. Claim (III), the doctrinal claim, states that the criterion of efficiency rationalizes prevailing legal rules and institutions. This doctrinal claim is weaker than the content claim; the latter asserts either that efficiency causes the content of the law or that it justifies it. The doctrinal claim, by contrast, asserts only that efficiency makes sense of the legal materials.