This chapter illustrates several distinct strategies for appropriating epistemic principles from contemporary currents in the philosophy of science which are evident in the work of the influential legal theorists Carl Schmitt, Hans Kelsen and Hermann Heller (even, in the case of Schmitt, where such an affinity is explicitly denied). Despite the variety of their approaches, each emphasized the same common nexus through which these principles were most readily adapted: the problem of indeterminism. This chapter analyzes Schmitt’s debt to a conception of causality developed by the physicist-philosopher Johannes von Kries, and shows how, despite his own best effort, Schmitt was not able to stand outside of a paradigmatic framework proper to the philosophy of science in his attempt to harness indeterminism for political-theoretical ends. It then shows how Kelsen came to see his previous reliance on neo-Kantian epistemology as untenable by examining the letters he exchanged with Vienna Circle philosopher Otto Neurath on the subject of causality. The chapter concludes by detailing Heller’s prescient critique of both Schmitt’s and Kelsen’s state conceptions, offering a perspective that allows us to appreciate the paradigmatic epistemological assumptions that these two otherwise opposed legal theorists shared in common.