From the Greek ontos and logos. The philosophical or systematic theory of existence (i.e., ‘being’.

One of the major subdivisions of Metaphysics, Ontology investigates the nature of existence. What is the nature of existence? What does it mean for something to be? What is the nature of is-ness?

Ontologies typically fall into one of three categories:

Dualism is by far the most common view in the history of Western Philosophy, but in the late Modern and Post-Modern era it has been surpassed by Materialism (the most common form of Monism).