"Metaphysics" is the branch of philosophy that deals with questions of being (ontology). Metaphysics studies both existence itself and the nature of things in existence. Metaphysics examines principles, causality, possibility, necessity, identity, change, becoming, time, space, freedom, substance, and the relationship between the mental and the physical. It asks questions like “What is the nature of that thing that is?” and “Where did that thing that is actually come from?” Basically, it seeks to discover the nature of reality.

In his Metaphysics, a defining work on the discipline, Aristotle identifies metaphysics as focusing on “being as such” (i.e., what it means to be), on first causes (how things come to be), and on what is unchanging. Over the centuries, other philosophers have added new focal points and questions to the study of metaphysics. Thomas Aquinas, for instance, identified metaphysics as a speculative science dealing with things that do not depend on matter or motion for their being or intelligibility, and he focused on questions of essence and existence (and the difference between them), participation, substance and accidents, and matter and form.

Modern philosophers have sometimes discounted metaphysics or shifted its focus, yet many continue to be intrigued by what it means to be.