Definition and Key Ideas

Metaphysics is the most abstract branch of philosophy. It’s the branch that deals with the “first principles” of existence, seeking to define basic concepts like existence, being, causality, substance, time, and space.

Within metaphysics, one of the main sub-branches is ontology, or the study of being. These two terms are so closely related that you can often hear people use “metaphysics” and “ontology” interchangeably. Many of the concepts raised in this article are about ontology, because this is one of the most active areas of metaphysics. However, the two concepts are not exactly the same: whereas metaphysics studies the general nature of reality, ontology specifically studies the idea of being. Another way to put this would be to say that ontology asks “what” while metaphysics asks “how,” although this is only a generalization.