 In both the Leibniz book and Das Erkenntnisproblem, then, Cassirer interprets the development of modern thought as a whole from the perspective of the basic philosophical principles of Marburg neo-Kantianism: the idea that philosophy as epistemology (Erkenntniskritik) has the articulation and elaboration of the structure of modern mathematical natural science as its primary task; the conviction that, accordingly, philosophy must take the “fact of science” as its starting point and ultimately given datum; and, most especially, the so-called “genetic” conception of scientific knowledge as an ongoing, never completed synthetic process (see below). From a contemporary point of view, Cassirer’s history may therefore appear as both “Whiggish” and “triumphalist,” but it cannot be denied that his work is, nevertheless, extraordinarily rich, extraordinarily clear, and extraordinarily illuminating. Cassirer examines an astonishing variety of textual sources (including both major and minor figures) carefully and in detail, and, without at all neglecting contrary tendencies within the skeptical and empiricist traditions, he develops a compelling portrayal of the evolution of “modern philosophical idealism” through Kant which, even today, reads as extremely compelling and acute.