Metaphysics is a branch of philosophy that investigates the most general features of reality: what exists, what kinds of things exist, and how they are related. Its central questions concern being, identity, change, causation, possibility, space, time, and the relationship between mind and matter. Unlike epistemology, which primarily examines knowledge and justification, metaphysics asks what reality is like, although the two fields frequently overlap. It is not necessarily an inquiry into supernatural things: many metaphysical theories concern ordinary objects, scientific entities, and the structure of the physical world.
Origins and historical development
The name derives from the Greek expression ta meta ta physika, conventionally translated as “the things after the physics.” It originated as a designation for writings by Aristotle arranged after his works on nature. The title did not initially mean a study of something beyond physical reality, although it later acquired that association. Aristotle described related inquiries as “first philosophy” and the study of “being qua being”—being considered simply as being.
In ancient Greece, thinkers debated whether reality was fundamentally changing or unchanging, unified or plural. Plato distinguished intelligible Forms from the changing sensible things that participate in them. Aristotle instead developed accounts of substance, form, matter, potentiality, and actuality that explained both stability and change.
Medieval Islamic, Jewish, and Christian philosophers extended these debates to existence, essence, creation, and divine attributes. Early modern thinkers developed competing systems: René Descartes distinguished thinking substance from extended substance, while Gottfried Wilhelm Leibniz proposed a universe of simple substances called monads. Immanuel Kant challenged attempts to establish knowledge of things beyond possible experience while investigating the conditions that make experience possible.
Comparable questions occur outside the European tradition. Schools associated with Hinduism debate selfhood and ultimate reality; Buddhist traditions examine dependent arising and challenge permanent selves. Applying the label “metaphysics” across traditions requires attention to differences in terminology and intellectual aims.
Being, objects, and properties
Ontology studies what exists and the categories into which existing things fall. Some philosophers use “ontology” almost interchangeably with metaphysics; others treat it as one part of a broader discipline that also investigates dependence and explanation.
A basic issue concerns the distinction between particular things and their properties. Two objects may both be red: do they share a single universal property, or is each redness particular to its object? Universals are repeatable characteristics that different things can instantiate. Nominalism rejects universals, although nominalist theories differ in how they explain resemblance and general classification.
Another question concerns abstract entities, such as numbers, sets, and propositions. Their apparent lack of spatial location and causal powers distinguishes them from ordinary concrete objects. Philosophers disagree about whether abstract entities exist independently, depend on minds, or can be eliminated from a satisfactory account of reality.
Mereology, the study of parts and wholes, asks when several things compose a further object. A related debate concerns whether a statue and the lump of material constituting it are one thing or two, given that the material could survive changes that destroy the statue.
Identity, change, space, and time
Identity concerns what makes something the same thing rather than merely similar to another. Persistence presents a puzzle: an object can change its properties while apparently remaining itself. Some theories hold that an object is wholly present at each time it exists; others understand it as extending through time with different temporal parts.
Personal identity asks what makes a person at one time identical to a person at another. Proposed accounts emphasize bodily continuity, psychological continuity, or other conditions. These questions differ from questions about personality or social identity.
Metaphysical accounts of space and time ask whether they exist independently of objects or consist in relations among objects and events. Contemporary debates engage with relativity and its treatment of spacetime. Presentism maintains that only present things exist, whereas eternalism holds that past, present, and future things all exist. These positions concern existence, not simply how time feels or how clocks measure it.
Causation, possibility, and freedom
Causation concerns how events or entities produce, determine, or make a difference to others. Accounts analyze it through regularities, counterfactual dependence, processes, powers, or interventions. A central difficulty is distinguishing genuine causal relationships from coincidental correlations.
Modality concerns possibility and necessity. Something may be logically possible yet excluded by the laws of nature; metaphysical possibility is often treated as another relevant standard. Possible worlds provide a framework for analyzing these distinctions, but philosophers disagree about whether worlds are concrete realities, abstract representations, or useful theoretical devices. Modal logic formalizes reasoning about necessity and possibility without settling those ontological questions.
Free will raises questions about agency and alternatives. Compatibilists hold that freedom can coexist with determinism, understood as the fixing of subsequent events by prior conditions and laws. Incompatibilists deny this compatibility. Indeterminism alone does not establish freedom, since randomness need not amount to control.
Mind, science, and method
Metaphysics overlaps with philosophy of mind in examining whether mental phenomena are physical, nonphysical, or fundamental in some other way. Physicalism maintains, broadly, that reality is wholly physical or dependent on the physical; dualist and idealist theories offer alternatives.
Metaphysical inquiry uses argument, conceptual analysis, thought experiments, and comparison of competing explanations. Work in philosophy of science also examines the implications of scientific theories for objects, laws, and causal structure.
Critics question whether some metaphysical disputes exceed available evidence or merely reflect linguistic choices. Responses include restricting inquiry to scientifically informed questions or defending its role in clarifying assumptions that scientific investigation itself leaves open.