 Austin’s importance to legal theory lies elsewhere—his theorizing about law was novel at four different levels of generality. First, he was arguably the first writer to approach the theory of law analytically (as contrasted with approaches to law more grounded in history or sociology, or arguments about law that were secondary to more general moral and political theories). Analytical jurisprudence emphasizes the analysis of key concepts, including “law,” “(legal) right,” “(legal) duty,” and “legal validity.”  Though analytical jurisprudence has been challenged by some in recent years (e.g., Leiter 2007, Leiter and Etchemendy 2021, Postema 2021 [Other Internet Resources]), it remains the dominant approach to discussing the nature of law. Analytical jurisprudence, an approach to theorizing about law, has sometimes been confused with what the American legal realists (an influential group of theorists prominent in the early decades of the 20th century) called “legal formalism”—a narrow approach to how judges should decide cases. The American legal realists saw Austin in particular, and analytical jurisprudence in general, as their opponents in their critical and reform-minded efforts (e.g., Sebok 1998: pp. 65–69). In this, the realists were simply mistaken; unfortunately, it is a mistake that can still be found in some contemporary legal commentators (see Bix 1999, 903–919, for documentation).