  There are other important, and more substantive, respects in which the Commentary was at the vanguard of Kant scholarship. The dominant trend in the interpretation of Kant’s theoretical philosophy throughout most of the nineteenth century had been the physio-psychological reading advanced by such figures as Schopenhauer, Jakob Fries, Friedrich Beneke, Jürgen Bona Meyer, Helmholtz, and of course Lange (Beiser 2018, 64–72, 81–84; 2014, 209–11, 460–63). According to this tradition, Kant’s main goal in the Critique was the discovery of the causal mechanisms underlying perception. Kant’s conception of the a priori was accordingly understood as referring to innate or ingrained properties of the psychological subject that played an active role in the construction of perception and acquisition of empirical knowledge. The first to break decisively with this tradition was probably Hermann Cohen. Cohen (1871) highlighted the epistemological side of Kant’s project—his interest in justifying various claims to knowledge. Accordingly, Cohen interpreted the a priori as referring to the logical, rather than psychological, conditions of knowledge (1871, 208). In this respect, Cohen’s influence on the Commentary was decisive. Vaihinger insists at the outset that Kant’s “philosophy is, in the first instance, epistemology [Erkenntnistheorie]” (1881–92, 1:8).