How do you prove the law? In American jurisprudence, the question has an odd, somewhat discordant sound. With respect to the proof of facts, there is an elaborate body of doctrine, with an equally elaborate body of accompanying scholarly commentary, describing the process for establishing the acceptability of propositions in adjudication. By contrast, there are no explicit rules of evidence for proving claims about the law. Nor does the law directly speak of the admissibility or significance of various considerations for proving legal claims. Nor does the law ordinarily discuss standards of proof for questions of law. Nor does the law openly consider the assignment of burdens of proof for questions of law. The entire language of evidentiary proof, so elaborately constructed for questions of fact, is largely absent from the American legal system with respect to questions of law. This work makes an articulate case for the importance examining law just as we do facts. It explores range of important issues about evidence, presumptions, and burdens of proof and demonstrates their relevance to questions of law just as they are to questions of fact. As lawyers and judges and legal subjects confront uncertainty about what the law is, they can and should, Lawson argues, be guided by the same kinds of considerations and structures and doctrines long used to make determinations about uncertain questions of fact.