l v i i i I N T R O D U C T I O N T O V O L U M E 1 4 (Doc. 351). Heinrich Zangger, on behalf of Romain Rolland, asked for the details of the text in which Einstein “opposes Kant” (Doc. 331). But in his reply to Berliner (Doc. 351), Einstein played down his opposition by pointing out that he had essen- tially only written a review of Alfred Elsbach’s book and that, given that Elsbach was a neo-Kantian, “some commentary generally referring to Kantian doctrine was unavoidable.” Given that he felt “insufficiently competent in purely philosophical topics,” Einstein declined to expand on them in Berliner's journal Die Naturwissenschaften.[25] Nevertheless, in the course of criticizing both Kant and even more so the neo- Kantians, Einstein spelled out an epistemological position containing his own blend of realism, holism, and reflections on the role of the a priori as compared to conventional concepts in physics. In his review, Einstein 1924n (Doc. 321), Einstein argued that Elsbach does not do justice to Kant. Indeed, in his attempt to reconcile Kant with relativity theory, Elsbach had suggested that even though there exist concepts and statements that play an a priori role at any given moment in the development of science, these concepts can change in the future. Furthermore, Elsbach argued, what the a priori concepts are has to be uncovered by interpreting the science of the day. Einstein countered that this conception of the a priori does not do justice to Kant and his fol- lowers. Their project, Einstein stated, had always been “to locate those a priori (i.e., not deducible from experience) concepts and relations that must be at the basis of every science because without them science is not conceivable at all. […] If one does not consider this goal achievable, one probably should not call oneself a ‘Kan- tian.’” In his view, Elsbach had proposed to weaken what it is to be a priori to an extent that amounts to giving up on the very idea of a priori concepts.[26] Einstein argued that there are then only two options: either claim that “relativity theory goes against reason,” or give up on Kant’s notion of a priori concepts. Einstein, in order to retain the opposition between Kantianism and relativity the- ory, not only criticized Elsbach’s interpretation of Kant, but also Kant himself. He argued that the most problematic part about Kant was the granting of a “special place” to spatio-temporal concepts, in contrast to other concepts. In a letter to Ernst Cassirer (Doc. 200), Einstein made the same point regarding the claim that causal- ity is an a priori notion, but in a more flamboyant fashion: “Aren’t the notions of cow and donkey also a priori?” Einstein’s wrestling with Kant and his opposition to the unchanging a priori dated back many years. He had read Kant’s Critique of pure reason at the age of thirteen, under the guidance of Max Talmey,[27] and had taken a course on Kant with August Stadler at age eighteen in his first year at the ETH (see Vol. 1, Doc 28). In 1918, he had written to Max Born that he was reading Kant’s Prolegomena and