Metaphysics is the philosophical study of how things are, how they exist, how things “be.” Aristotle wrote the “physics” which was his description of the natural world (plants, animals, etc.) and he wrote a series of other, related topics which went beyond the natural world. In the sequence of books, these later ones went “after the physics” or “meta physics” so the name stuck. The philosophical study of metaphysics should not be confused with the occult and odd spiritual books in that funny section of the used bookstore. Instead, metaphysics is heavy philosophy.
Metaphysics studies “being” in the sense of an action………such as running, sleeping, jumping, and being. Aristotle, and those after him, explored how things are being. It’s very conceptual, and difficult to diagram, so it’s especially difficult our minds today, since we’ve all grown up learning by viewing pictures.
Metaphysics took several forms, but has been largely dismissed in philosophy. Most modern philosophers do not study metaphysics, thinking it not relevant to today’s discussions. Modern philosophy and science focuses not on how things “be” but rather focus on “what”………they define what a thing is by it’s characteristics and properties, such as how much it weighs, how fast it runs, what color it is, etc. These things are the object’s essence. So most modern philosophers study essences, not existences.
However, Thomas Aquinas made an extremely important distinction. He separated essence and existence, pointing out that even if we know all of an object’s characteristics (essence), we still have not explained it’s ongoing, continual cause of being. So Thomas makes a distinction between essence and existence. All created things have both existence and essence, but to Thomas, existence preceeds essence. In a logical sense, we must explain being before we can explain characteristics.
So because modern philosophy has no formal explanation existence preceeding essence, their explanations of essences has no foundation, and we end up with a series of messes in philosophy.
The trouble is that metaphysics is very difficult. If you want to see just how difficult, find Aquinas’ tiny book (it’s an article, really) called On Being and Essence. But regardless of the difficulty, we would all be better off if we understood metaphysics.