Moritz Schlick’s work shaped Logical Empiricism and thereby an important part of philosophy in the first half of the 20th century. A continuous thread that runs through his work is a philosophical diagnosis of the ‘great errors in philosophy’: philosophers assume that there is intuitive knowledge/knowledge by acquaintance. Yet acquaintance, it is not knowledge, but an evaluative attitude. In this paper I will reconstruct Schlick’s arguments for this conclusion in the light of his early practical philosophy and his reading of (...) Schopenhauer’s The World as Will and Idea. Having the historical roots of Schlick’s position in view will put us in a position to explore and question its presuppositions. (shrink)