Metaphysics is a major branch of philosophy that examines the most fundamental questions about reality and existence. Rather than concentrating only on what can be directly observed or measured, metaphysical inquiry asks what it means for something to exist, what kinds of things may exist, how objects and identities persist through change, how causes relate to effects, and how mind and matter may be connected. Major areas of metaphysical inquiry include ontology, causation, space and time, identity, possibility and necessity, and the relationship between free will and determinism. The term is historically associated with works of Aristotle that came to be placed “after the Physics,” although metaphysics later developed into a broad field concerned with the underlying structure and nature of reality.