This dissertation questions standard renditions in International Relations (IR) about one of its "founding fathers", Hans J. Morgenthau, usually taken to be representative of "classical realism". Emphasising the legal origins of his though, this dissertation argues that what Morgenthau originally meant by "realism" was the introduction of a dose of "reality" into the way inter-state disputes were conceptualised. The "dominant doctrine" of positivist legal formalism detracted from focusing on the underlying distribution of power inherent in any international dispute, and thus also from the "empirical" enforceability of international legal norms. Furthermore, Morgenthau's use of the term "legalism" did not imply, as is commonly held, that international law was irrelevant to the study of international relations, but that it was pernicious to uphold a formalist legal doctine that was only instrumentalised to suit the requirements of one or more superpowers seeking to depoliticise their underlying claims to ideational supremacy