That branch of philosophy that studies the most general categories and concepts presupposed in descriptions of ourselves and the world.
Examples are causality, substance, ontology , time , and reality.
Metaphysical questions have a very broad scope. Whereas the chemist might investigate particular substances, the metaphysician asks what it means to be a substance, and whether there is one basic substance, or many. Metaphysical questions can become the subject of more specialized philosophical inquiry. We can ask whether our actions are subject to causality, which gives rise to the problem of free will . And the question of whether our mental experiences involve a separate substance from body is a major issue in the philosophy of mind.