 For Kant, too, the term, “function”, is always connected to the categories’ spontaneity and their synthetic activity; further, he holds that true cognition (Erkenntnis) can only occur if the synthesis in question “schematizes” representations given in intuition (cf. Young 1992; Friedman 1992, 2000). By contrast, Natorp understands all concepts as functional, i.e., as categorial, since all of them, including the concepts of space and time, are thought-operations serving to unify a  manifold.[27]  As we saw above, Natorp rejects any notion of intuition as a passive faculty receptive of a given sensible manifold (cf. Natorp 1912c: 201). Instead, he interprets intuition as itself an act of synthesis, i.e., as a generation of unity. He argues that a critical account of knowledge is not justified in presupposing some object conceived as existing radically independent of mind, and which then somehow affects it via intuition: to do so would be tantamount to an intolerable “metaphysicism” (Natorp 1912c: 202). Rather, Natorp claims to find in the first Critique itself the basis for his view that intuition is not a factor “alien to thought [denkfremd]”, but that it merely signifies a different aspect of thinking, viz. that aspect in which a fully spatio-temporally determined object, rather than merely a law, is thought (Natorp 1912c: 204; Natorp 1910c: 2–3). This “fulfillment [Vollzug]” of objective thought 