A branch of metaphysics concerned with the nature of things (i.e., with ‘being’) or the subject of existence. It differentiates between reality and appearance, and investigates the various ways in which entities belonging to different logical categories (e.g., numbers, physical objects) may be said to exist. It is sometimes confused with epistemology, another branch of metaphysics concerned with knowing and knowledge (i.e., ‘becoming’). Ontology was revived in the early 20th century by Edmund Husserl (1859-1938) and others who promoted the study of existentialism and phenomenology. Subsequently, it became a defining feature of analytic philosophy through the writings of people like William Van Orman Quine (1908-2000).
See Appearance-reality distinction, Developmental epistemology, Dualism, Hermeneutics (and phenomenology), Monism