 It is connection with this that Kant argues, in the second part of the Appendix (“On the Final Aim of the Natural Dialectic of Human Reason” (A669/B697)), that the three highest ideas of reason have an important theoretical function. More specifically, in this section Kant turns from a general discussion of the important (regulative) use of the principle of systematicity, to a consideration of the three transcendental ideas (the Soul, the World, and God) at issue in the Dialectic. As examples of the unifying and guiding role of reason’s ideas, Kant had earlier appealed to the ideas of “pure earth” and “pure air” in Chemistry, or the idea of a “fundamental power” in psychological investigations (cf. A650/B678). His suggestion earlier was that these ideas are implicit in the practices governing scientific classification, and enjoin us to seek explanatory connections between disparate phenomena. As such, reason’s postulations serve to provide an orienting point towards which our explanations strive, and in accordance with which our theories progressively achieve systematic interconnection and unity. Similarly, Kant now suggests that each of the three transcendental ideas of reason at issue in the Dialectic serves as an imaginary point (focus imaginarius) towards which our investigations hypothetically converge. More specifically, he suggests that the idea of the soul serves to guide our empirical investigations in psychology, the idea of the world grounds physics, and the idea of God grounds the unification of these two branches of natural science into one unified Science (cf. A684/B712-A686/B714). In each of these cases, Kant claims, the idea allows us to represent (problematically) the systematic unity towards which we aspire and which we presuppose in empirical studies. In accordance with the idea of God, for example, we “consider every connection in the world according to principles [Principien] of a systematic unity, hence as if they had all arisen from one single all-encompassing being, as supreme and all-sufficient cause” (A686/B714). Such a claim, controversial as it is, illuminates Kant’s view that empirical inquiries are one and all undertaken in light of the rational goal of a single unified body of knowledge. It also points towards the Kantian view, later emphasized in the Transcendental Doctrine of Method, that reason’s theoretical and practical interests ultimately form a higher unity.