Die Frage "Was ist?" bei Hermann Cohen und Franz Rosenzweig

The philosophical question "what is?" plays different roles in the work of Cohen and Rosenzweig. According to Cohen, it expresses the authentic meaning of the Socratic concept, which has its methodical-transcendental foundation in the Platonic Idea as answer, since it gives an account of the concept. So Cohen turns the question into an epistemological problem, because it ultimately refers to the necessary condition of knowledge. In contrast, Rosenzweig sees in the "what is?" question grounds to condemn the "old" philosophy founded on the identity of being and thought. In his view, the question is the original sin of the "philosophy of the All", which has always reduced everything to something completely different by means of the altering word "is" in the "is"-question. Nevertheless, with regard to the "what is?" question, it is possible to detect a kind of agreement between the two philosophers: namely, Rosenzweig opposes a claim of ontological reduction that Cohen also rejects.