 But while the fact that philosophy is at least partly determined by contingent cultural factors undercuts necessity and progress, it also opens the door for a reconceptualization of the “essence” of philosophy. In his Einleitung in die Philosophie [Introduction to philosophy] (1914) Windelband reflects on the fact that everyday life, culture, and science do already contain general concepts of the world. These concepts form the initial content of philosophical reflection (1914: 6). But the business of philosophy only takes off when these initial concepts, and the assumptions that are baked into them, become unstable and collapse. An experience of shock and unsettling prompts philosophy to question, rethink, and critically assess the concepts and ideas of everyday life and science. In this process of critical assessment, philosophy strives to purify these concepts and ideas, and to connect them into a coherent, unified system. According to Windelband, in this process of conceptual reorganization, a rational necessity exerts itself. The “vigorous and uncompromising rethinking of the preconditions of our spiritual life” creates certain philosophical problems “with objective necessity” (1914: 8).