Metaphysics is the branch of philosophy concerned with explaining the nature of the world. It is the study of being or reality.[1] It addresses questions such as: What is the nature of reality? Is there a God? What is man's place in the universe? A central branch of metaphysics is ontology, the investigation into what categories of things are in the world and what relations these things bear to one another. The metaphysician also attempts to clarify the notions by which people understand the world, including existence, objecthood, property, space, time, causality, and possibility.

To call one a metaphysician in this traditional, philosophical sense indicates nothing more than his or her interest in attempting to discover what underlies everything. Old materialists, who said that there is nothing but matter in motion, and current naturalists, who say that everything is made of lifeless, non-experiencing energy, are just as much to be classified as metaphysicians as are idealists, who maintain that there is nothing but ideas, or mind, or spirit.

A commonly employed, secondary, popular, usage of metaphysics includes a wide range of controversial phenomena believed by many people to exist beyond the physical. Popular metaphysics relates to two traditionally contrasted, if not completely separable, areas, (1) mysticism, referring to experiences of unity with the ultimate, commonly interpreted as the God who is love, and (2) occultism, referring to the extension of knowing (extrasensory perception, including telepathy, clairvoyance, precognition, retrocognition, and mediumship) and doing (psychokinesis) beyond the usually recognized fields of human activity.

The academic study of the occult (literally hidden) has been known as psychical research and, more recently, parapsychology. Both New Age and New Thought emphasize mysticism and its practical, pragmatic application in daily living, but New Thought discourages involvement in occultism.