Ontology is a branch of metaphysics which studies being. Ontology is concerned with the ultimate nature of being, and of all reality in general.
The process of studying ontology generally consists of describing being as well as determining how reality may be organized and categorized, and how different types of beings relate to one another. The term “an ontology” refers to the things counted as being in a metaphysical system. Generally, an ontology is a list of things that exist — the “furniture of the universe” as it is sometimes put.
Differences in ontology among philosophers generally deal with whether or not there are non-physical entities, and whether those things can be counted as being, existing, both or neither. Examples of candidates for ontological status as non-physical being include the mind, mathematical objects and universals.
Philosophers who do work on ontology are referred to as ontologists. The following are some of the prominent ontologists discussed on this site: