What is Metaphysics?
The term "metaphysics" simply means "beyond physics" in the Greek language. The term originated from the ordering found in a standard compendium of Aristotle's works dating from the Middle Ages. This compendium was a Latin translation of all the works attributed to Aristotle that were extant at that time. The ordering of the works was consistent with a list originally compiled by the classical scholar, Andronicus of Rhodes, in about 60 B.C. Andronicus grouped the works by category and arranged them in a particular order of study: first logic, then natural science, then metaphysics, then ethics and politics. Thus, Aristotle's work entitled Metaphysics, as the title suggests, was that work next in order after the works on natural science (including physics), and just before the works on ethics and politics.
Metaphysics consists of 14 books and covers a wide variety of philosophical subjects. However, the central theme seems to be an inquiry into the nature of what Aristotle called "substance." Aristotle defined substance as ultimate reality. He also describes substance as the "substratum of all existing things" which may possess both formal and material reality. In other words, Aristotle's metaphysics deals with what modern philosophers would call "Ontology."
If you search the Internet for a definition of metaphysics you'll find considerable variation in the meanings provided. All definitions include Ontology as a part of metaphysics, but the similarity ends there. For the purposes of this website, I will define metaphysics in the same way that I was taught as an university undergraduate. In my view, the term "metaphysics" encompasses three major philosophical topics as follows:
1) Ontology - the study of being;
2) Epistemology - the study of knowledge, what do we know and how do we know it; and
3) Cosmology - the study of the true nature and structure of the universe (Cosmos).