A currently popular view among legal positivists is that law is a social construction. Many of the same legal philosophers also argue that before one can study law empirically, one needs to know what it is. At the heart of this paper is the claim that these two propositions are inconsistent. It presents the following dilemma: if law is a social construction like all other social constructions, then legal philosophers have to explain what philosophers have to contribute to understanding it. Studies of social constructions are typically conducted by historians, sociologists, and others, who explain them (and what they are) on the basis of empirical data. If, as legal philosophers claim, conceptual clarification must precede empirical work, then it follows that the lack of conceptual work on the nature of other social constructions renders suspect all empirical work on them. To avoid such a radical conclusion, legal philosophers may argue instead that law is a social construction of a special kind. But to say that is to undermine the premise with which the argument began. Moreover, this response to the dilemma collapses what is now taken to be what separates legal positivism from natural law theory, thus undermining the motivation for this view. I conclude the essay by offering a different solution to the dilemma by suggesting that it shows that the fundamental debates of legal philosophy are not conceptual but political.