Firstly, philosophy and science are compared by taking into account five aspects: critical attitude towards the assumptions, definitions and terminological rigor, formulation of a theory and its inferential development, control and external support, presence of a holistic approach. Secondly, for each aspect, some reasons that make the ontologies of Knowledge Representation closer to philosophy or closer to science are pointed out. Conclusions are different and not clear-cut. In the discussion of the fifth aspect Nicola Guarino's approach is emphasized and presented in the light of Carnap's notion of explication.