The received view has it that Hans Reichenbach and his friends of the Berlin Group worked close together with the more prominent Vienna Circle. In the wake of this view, Reichenbach was often treated as a logical positivist – despite the fact that he decisively opposed it. In this chapter we follow another thread. We shall show the “third man”– besides Reichenbach and Walter Dubislav – of the Berlin Group, Kurt Grelling, as a man who could grasp the academic trends (...) of the time faster than anybody else, who was better informed about logic and philosophy of nature than his two prominent colleagues and thus, could better delineate, although tentatively, central threads of research of the Berlin Group. Grelling did this on several occasions, but most ostensibly in the last years of his life when he was focused on problems of formal ontology. On the basis of this analysis, we shall see that in the early 1920s, Reichenbach too was led by a project in ontology of science that he elaborated together with the psychologist Kurt Lewin. Moreover, Reichenbach’s later philosophy of nature was also shaped by this project. We present this direction of philosophy of science as a “road less travelled” which, however, if revived, can point to a new direction that will more closely connect philosophy and science. (shrink)