Abstract This contribution examines the epistemological foundations of legal monism, as theorized by the Vienna School of Jurisprudence and its leading proponents, in particular on the basis of its crucial elements: the Grundnorm, the hierarchy of norms, and the unity of the law. Subsequently, the theory of legal monism will be discussed and defended against dualism and pluralism by assessing its plausibility and explanatory power in describing the trigonal relationship between national law, European Union law, and public international law.
