Plain-language explanation.
Metaphysics is the branch of philosophy that investigates the fundamental nature of reality — what exists, what it is made of, and how things relate to one another. It addresses questions that go beyond what science can directly test: What is time? Do we have free will? What makes something the same thing over time?
Core concepts and standard treatment.
Core metaphysical topics include ontology (the study of what exists — universals vs particulars, substance, properties), philosophy of time (eternalism vs presentism), personal identity (psychological continuity theory vs biological criterion), causation (Hume's regularity theory, counterfactual accounts), and free will (compatibilism, libertarianism, hard determinism).
Deeper theory, debates and edge cases.
Advanced metaphysics engages with modal logic and possible worlds (Kripke, Lewis), trope theory and bundle theory, grounding and fundamentality, quantum mechanics and its metaphysical implications (many-worlds interpretation), philosophy of mathematics (Platonism vs nominalism), and the metaphysics of social kinds (race, gender, institutions).
How it is applied in practice.
At the metaphysics researcher and philosophy professor level, scholars publish in Mind, Philosophical Review, and Analysis; contribute to Stanford Encyclopedia of Philosophy articles; engage in analytic/continental metaphysics debates; supervise PhD research on causation, modality, or consciousness; and apply metaphysical frameworks to philosophy of science and cognitive science debates.