 Neo-Kantianism, it is often said, was the dominant current of late nineteenth-century German academic philosophy. While true, this statement is uninformative, since the label conveys no clear doctrinal content. Given the widespread perception that philosophy had become discredited by the untenable claims of the German Idealists, the various neo-Kantian schools shared a conviction that Kant—on some interpretation of his sobriety—could give philosophy a respectable and genuine task again, now that it had awakened from its long post-Hegelian hangover (cf. Natorp 1918a: 4–6; Dussort 1963; Schnädelbach 1983a, 1983b; Köhnke 1986; Philonenko 1989; Sluga 1976: 28). The label therefore does not necessarily signify a revival of Kant’s doctrines (much less of Kant-scholarship for its own  sake[6]  ), but rather, as Natorp himself puts it, philosophizing in the spirit of Kant (Natorp 1918a: 7). But what does that mean? For the Marburg School, Kant’s great idea, “the central notion with respect to which one must relate, understand, and evaluate everything else in Kant” is the transcendental method (Natorp 1912c: 194; cf. Cassirer 1925: 288). This method constitutes “the unshakeable guideline of our whole philosophizing” (Natorp 1912c: 196). Why? Because the transcendental method anchors philosophy in facts (eminently the fact of mathematical physics), of which philosophy is to establish the conditions of possibility or justification (Rechtsgrund) (Natorp 1912c: 197; 196). By limiting itself to this task of justification, philosophical reason keeps itself from ascending into the aether of speculation. At the same time, by discovering the source of scientific objectivity (and thus of rational objectivity generally), i.e., by “clearly exhibiting the law [of objectivity] in its purity”, philosophy “secures science [and rational activity generally] in its autonomy and preserves it from alien distraction” (Natorp 1912c: 197–198). Transcendental philosophy in the Kantian spirit, then, is doubly “critical”, checking itself against metaphysical excesses, on the one hand, but also rigorously formulating the ideal grounds of the sciences, on the other (Natorp 1912c: 198; cf. Poma 1997, ch. 3, 4). At the same time, the Marburg School finds in the critical philosophy an idealistic bulwark against the empiricism epitomized by Mill.