According to Hartmann an unbiased philosophical inquiry moves through the three main stages of phenomenological aporetic and theoretical development The first stage is descriptive and requires the systematic collection of all the available evidence relevant to whatever is under scrutiny More often than not descriptions end up in conflicting theses often in the form of aporias More than anybody else Hartmann rehabilitates the value of aporias for two recent evaluations of Hartmann’s aporetic method see Schlittmaier 2011 and Rescher 2011 Aporias themselves are informative and should not be forced to disappear by fiat decisions such as an a priori assumption on the overall consistency of reality or the assumption that we have a direct transparent access to reality The last phase of the philosophical method consists in using as few metaphysical assumptions as possible for the systematic coordination of the outcomes from the first two phases E S Metaphysical assumptions are necessary for the task of incorporating aporias into a framework able to make sense of them Since metaphysical assumptions are not directly supported by descriptive data it is advisable to keep them to a minimum or to assume the weakest possible metaphysical assumptions An original way of distinguishing between ontology and metaphysics underlies the third stage of theoretical development Ontology for Hartmann deals with what can be subsumed under at least partially representable categories see Section 3 below Two main consequences follow from this view of ontology firstly ontology is primarily a theory of categories in the sense that all ontological distinctions have the form of categories AIntro1 and secondly science in all its branches is the most successful and powerful ally of ontology More precisely for Hartmann science is ontological in all its ramifications G37a This is rather at odds with the mainstream view of science as an eminently epistemological affair This is one of the issues on which Hartmann firmly departs from the Kantian—to be precise the NeoKantian—legacy The claim that the main orientation of science is ontological immediately entails that scientific categories are further specifications and subdivisions of ontological categories In other words the contact with science is a characteristic feature of the theory of categories and therefore of ontology AIntro1 The philosopher’s task is to unfold the first and most general articulations of the theory of categories while scientists deal with their subsequent further specifications