n the year s following the completion of Das Prinzip der Wissenschaft in1908, Hägerström wrote and published several works, among them “Botanisten och filosofen” (1908/1910, reprinted 1957),2 “Kritiska punkter i värdepsykologien” (1910), his inaugural lecture Om moraliska föreställningars sanning (1911)3, and Till analysen af det empiriska själfmedvetandet (printed 1910, published posthumously 1945).The purpose of this Chapter is primarily to provide a positive account of Hägerström’s philosophy of science.This task will accomplished by means of an analysis of the aforementioned works, in which it will be shown how Hägerström parted from subjectivism and what effects this development had on his scientific research.The working hypothesis is that the final break with subjectivism and idealism occurred when Hägerström became professor of practical philosophy at the University of Uppsala in 1911. For instance, in Hägerström’s inaugural lecture there is the theory, on the one hand, of rejecting the possibility of basing the science of ethics and morals on purely suba ca l l f o r s c i e n t i f i c p u r i t y 170 The Leading Principle: The Necessity of a Doctrine of Knowledge1 part i i i , chapter 1 I 1 See, e.g.,Hägerström,“Botanisten och filosofen” (1910), p.58.Where Hägerström asks “Is a philosophical doctrine of knowledge superfluous?” My translation. Swedish: “Är filosofisk kunskapslära överflödig?” 2 There are two editions of this text, one extensive version dating from1908 (published posthumously in Filosofi och vetenskap 1957) and one abridged version published 1910. I have chosen to use 1908 edition, since it is more comprehensive than the stylistically more enjoyable, but abridged, edition of 1910. If I refer directly to the 1910 edition it will be referred to as: “Botanisten och filosofen” (1910). 3 English translation: Hägerström, “On the Truth of Moral Propositions,” in Philosophy and Religion.