In the social sciences, an emphasis on ontological and epistemological issues was a major source of debate from approximately 1985 to 2005. Over the past decade and more this, issue has faded from importance. The biggest influence on this change has been the increasing role of mixed methods research, where the key concern is how well the choice of methods meets the research goals -- rather than issues of abstract philosophy.
Ontology is the branch of philosophy that studies the nature of existence or being. It is concerned with questions about what exists and how it exists. Epistemology is the branch of philosophy that studies knowledge and belief. It is concerned with questions about what we know, how we know it, and what we can know. Ontology and epistemology are two of the main branches of philosophy. They are closely related because they both deal with fundamental questions about reality and knowledge. Ontology is concerned with the nature of reality, while epistemology is concerned with how we know what we know.