In the still growing literature on the history of Logical Empiricism, the Kantian roots of some of the movements' core ideas and its relationship with neo-Kantianism have been discussed frequently. A case in point is Michael Friedman's analysis of the debates between Hans Reichenbach and Moritz Schlick during the year 1920, after which Reichenbach—prematurely, to Friedman's mind—abandoned his relativized a priori conception of space and time in favor of a straighter empiricist approach, mainly in order to force issue with neo-Kantian critics of general relativity. More recently, these primarily historical investigations have been supplemented by two systematic projects according to which the relativized a priori, if conceived against the backdrop of the mathematics of the day, contains the seeds for a better understanding of modern physics and permits a defense of scientific philosophy against some of the classical criticisms by Quine, Kuhn, and others. While Friedman, through this Kantian turn, intends to maintain core insights of the Logical Empiricist tradition, Ryckman challenges the authority of Reichenbach and Schlick in matters of the 'special and the general theories of relativity and elaborates a different approach that departs from an alternative Kant-inspired tradition centering around the pertinent works of Ernst Cassirer and Hermann Weyl.