This study deals with problems in social sciences in general and in sociology in particular resulting from forgetting about ontology in the discussions concerning the philosophy of social sciences. The study focusses on the concept of paradigm in order to show how ontological, epistemological and methodological conventional rules establish the understanding of science. In the study, the significance of ontolological assumptions that are the basis of other assumptions of the paradigm is emphasized. Then, problems that occur due to isolated epistemology are taken into consideration. Finally, the cognitive and sociological reasons for epistemolgy without ontology are analysed. The ultimate aim of the study is to focus on the significance of the concept of scientific paradigm and to indicate that despite all sociological dynamics, ontology as a scientific requirement can not be ignored.