 For Wundt, it is only the sciences that have methodologies by which to synthesize our representations, sensible as well as “processed”, into “facts” or “pieces of” knowledge (Erkenntnisse). Hence, while strictly speaking he is committed to considering psychology (i.e., physiological psychology and VP) a part of philosophy, he usually speaks of them as distinct enterprises. This is because psychology is hybrid, adapting scientific methodologies to its particular aims; in this sense psychology, although part of philosophy, synthesizes facts, just like the  sciences.[47]  By contrast, philosophy’s pure task is universal, operating over all scientific domains; it is, he writes, “the general science whose task it is to unify the general pieces of knowledge yielded by the particular sciences into a system free of contradiction” (SP I: 9). Philosophy’s positive role, therefore, is not to provide the foundations of science, nor can it ever “step into the role of a particular science” (cf. Kusch 1995: 129); rather it is “to take in every case the already secured results of those sciences as its foundation”, and organize them into a single, overarching system by determining their points of connection (PP I: 8; 6). Wundt calls this side of philosophy Prinzipienlehre or “doctrine of principles”. By contrast, its negative or critical role is to regulate the sciences in accord with the imperative of consistent systematicity. In short, it has no constitutive but merely a regulative role vis-à-vis the sciences. Thus, when we return to the philosophical as opposed to the scientific aspect of psychology’s hybrid structure, we see that this aspect consists in its aim (as opposed to its method) of explaining rules of genesis, connection, and separation of those mental representations with an epistemic character. Wundt calls this psychological contribution to philosophy Erkenntnislehre or “doctrine of knowledge” (i.e., the theory of the coming-to-be of knowledge). This explanation then provides to philosophy the scientific foundation for its pure  task.[48]