Metaphysics & Ontology
The philosophical study of the fundamental nature of reality, being, and existence, encompassing the classification of entities, properties, and relations.
Metaphysics is a fundamental branch of philosophy concerned with the first principles of things, including abstract concepts such as being, knowing, substance, cause, identity, time, and space. The term derives from the ancient Greek ta meta ta physika, referring to Aristotle's untitled works collected after his physical treatises. Ontology, a core sub-discipline, specifically investigates the nature of existence, categorizing what kinds of things exist and how they relate to one another.
Modern metaphysics intersects deeply with theoretical physics, cognitive science, formal logic, and information theory. Within the Aevum Encyclopedia, this category houses comprehensive analyses of classical debates alongside contemporary formal ontologies, mereology, and metaphysical semantics.
- Ontology (from Greek ὄν, "being" + λόγος, "study")
- The philosophical inquiry into the nature of being, existence, and reality, often structured as a formal taxonomy of entities and their hierarchical relations.
Core Branches & Subdisciplines
The field is traditionally divided into several interlocking domains. Each contains thousands of peer-reviewed entries, historical analyses, and formal models.
Ontology
Study of being, existence, and categorization of entities.
Theory of Universals
Nominalism vs. Realism: Do abstract properties exist independently?
Modality
Necessity, possibility, possible worlds, and counterfactuals.
Identity & Change
Persistence through time, mereology, and the Ship of Theseus paradox.
Causation & Laws
Determinism, counterfactual dependence, and natural necessity.
Space & Time
A-series vs B-series, eternalism, presentism, and relationalism.
Featured Entries Editor's Selection
What Is It Like to Be a Bat?
Ned Block · Qualia & Phenomenal Consciousness · 12 min readPossible Worlds Semantics & Modal Realism
David Lewis · Modality · 18 min readMereological Nihilism: Only Simples Exist
Peter van Inwagen · Ontology · 14 min readMetaphysical Grounding & Ontological Dependence
Fine, Schaffer, Rosen · Structure · 21 min readRecent Contributions
Primary References & Bibliography
- Aristotle. Metaphysics (c. 340 BCE). Translated by W.D. Ross.
- Kant, I. Critique of Pure Reason (1781/1787). A & B Editions.
- Quine, W.V.O. "On What There Is" (1948). Ontological Relativity.
- Lewis, D. On the Plurality of Worlds (1986). Blackwell.
- Sider, T. (2011). Oxford University Press.
- Aevum Editorial Board. "Guidelines for Metaphysical Taxonomy v4.2" (2024).