Ontology (25-Volume): Encyclopedia of All Known Conceptions of Reality and Existence

Encyclopedia of Ontology: The Study of Being, Existence, and Reality

A reference on all known conceptions of reality and existence across civilizations, sciences, and emerging technological futures.

The Purpose of Ontology

Metaphysics, ontology, and epistemology are deeply interdependent branches of philosophy, each addressing a different but inseparable dimension of human inquiry. Ontology, often regarded as a core part of metaphysics, investigates what exists and the fundamental categories of being, while metaphysics examines the broader nature, structure, and principles of reality, including causation, space, time, identity, and possibility.

Epistemology complements these inquiries by asking how we can know what exists, what justifies our beliefs about reality, and what limits constrain human knowledge. Any ontological claim about the existence of objects, minds, universals, or God presupposes epistemological assumptions regarding evidence, perception, reason, or testimony, while epistemological theories themselves often depend upon metaphysical and ontological views concerning the nature of truth, consciousness, and reality.

Together, the three disciplines form a unified philosophical framework: ontology asks what exists, metaphysics asks what reality is like, and epistemology asks how we know it. Their continuous interaction has shaped philosophical thought from ancient Greek, Indian, and Chinese traditions to contemporary debates in science, artificial intelligence, and the philosophy of information.

The Encyclopedia of Ontology provides a comprehensive exploration of being, existence, reality, identity, substance, causation, and the fundamental structure of the world. It examines how different philosophical traditions, religious systems, scientific theories, and contemporary disciplines have addressed the question: What exists?

Ontology is among the oldest branches of philosophy and forms the metaphysical foundation upon which epistemology, logic, ethics, theology, science, mathematics, and social theory are built. This encyclopedia traces the historical evolution of ontological thought from ancient civilizations to contemporary debates concerning artificial intelligence, virtual realities, information systems, and cosmology.

Volume I: Foundations of Being: History, Concepts, and Classical Ontologies

Synopsis

Volume I introduces the fundamental questions of ontology:

What does it mean to exist?
What kinds of things exist?
Is reality composed of substances, processes, relations, or events?
Are universals real?
What is the difference between appearance and reality?

The volume surveys the historical development of ontological inquiry across ancient, medieval, and early modern traditions while introducing the principal concepts that continue to shape metaphysical debates.

Outline

Part A. Introduction to Ontology

Nature and Scope of Ontology
Being and Existence
Reality and Appearance
Categories of Being
Substance and Attribute
Identity and Difference
Essence and Existence
Ontological Commitment

Part B. Ancient Origins

Ontological Ideas in Ancient Egypt
Mesopotamian Conceptions of Reality
Vedic Ontologies
Upanishadic Conceptions of Being
Jain Ontology
Buddhist Ontology
Chinese Conceptions of Reality
Confucian Ontology
Daoist Ontology

Part C. Greek Foundations

Pre-Socratic Ontology
Parmenides and Being
Heraclitus and Becoming
Atomism
Socrates and Reality
Plato’s Theory of Forms
Aristotle’s Categories
Substance in Aristotle
Hellenistic Ontologies

Part D. Medieval Ontologies

Augustine
Neoplatonism
Islamic Ontology
Avicenna
Averroes
Jewish Metaphysics
Scholastic Ontology
Thomas Aquinas
Universals Debate

Part E. Early Modern Ontology

René Descartes
Substance Dualism
Spinoza’s Monism
Leibniz’s Monadology
Locke and Substance
Berkeley and Idealism
Hume and Identity
Kant and the Conditions of Being

Part F. Fundamental Ontological Debates

Monism
Dualism
Pluralism
Materialism
Idealism
Realism
Anti-Realism
Essentialism
Nominalism

Volume II: Structures of Reality: Categories, Relations, and Metaphysical Systems

Synopsis

Volume II investigates the architecture of reality itself. It examines the categories through which existence is understood and explores the entities, relations, properties, processes, and structures that constitute the world.

The volume bridges classical metaphysics with contemporary analytic ontology and philosophy of science.

Outline

Part B. Substance and Property

Substance Theory
Bundle Theory
Properties
Relations
Tropes
Dispositions
Powers Ontology

Part C. Identity and Persistence

Personal Identity
Numerical Identity
Qualitative Identity
Persistence Through Time
Endurantism
Perdurantism
Essential Properties
Accidental Properties

Part D. Space, Time, and Reality

Nature of Space
Nature of Time
Presentism
Eternalism
Four-Dimensionalism
Space-Time Ontology
Temporal Parts
Change and Permanence

Part E. Causation and Dependence

Causation
Determinism
Indeterminism
Necessity
Contingency
Grounding
Dependence Relations
Emergence

Part F. Possibility and Modal Reality

Modal Ontology
Possible Worlds
Necessity and Possibility
Counterfactuals
Modal Realism
Modal Anti-Realism
Fictional Entities
Imaginary Objects

Part G. Contemporary Metaphysical Systems

Process Ontology
Structural Realism
Ontic Structural Realism
Event Ontology
Relational Ontology
Information Ontology
Naturalized Metaphysics

Synopsis

Volume III explores how ontology functions in modern intellectual life. It examines ontological questions arising in science, technology, social theory, law, medicine, environmental studies, and artificial intelligence.

The volume demonstrates that ontology is not merely an abstract philosophical discipline but a framework shaping how contemporary societies classify and understand reality.

Outline

Part A. Scientific Ontologies

Ontology of Physics
Matter and Energy
Quantum Ontology
Fields and Particles
Cosmological Ontology
Biological Ontology
Species and Natural Kinds
Systems Ontology

Part B. Mind and Consciousness

Mind-Body Problem
Consciousness
Mental States
Intentionality
Self and Personhood
Phenomenology
Embodied Existence
Cognitive Ontology

Part C. Social Ontology

Social Reality
Institutions
Collective Intentionality
Social Kinds
Race and Ontology
Gender Ontology
Cultural Ontology
Political Ontology

Part D. Language and Conceptual Reality

Names and Existence
Reference
Meaning and Reality
Linguistic Ontology
Conceptual Schemes
Hermeneutic Ontology
Narrative Identity

Part E. Applied Ontologies

Legal Ontology
Medical Ontology
Economic Ontology
Educational Ontology
Environmental Ontology
Urban Ontology
Organizational Ontology

Part F. Information and Digital Ontologies

Information as Being
Computational Ontology
Data Ontology
Knowledge Representation
Semantic Web Ontologies
Digital Objects
Virtual Reality
Metaverse Ontology

Part G. Artificial Intelligence and Future Reality

Machine Ontology
Artificial Agents
Human-AI Relations
Algorithmic Entities
Autonomous Systems
Synthetic Persons
Posthuman Ontology
Future Ontologies

Part H. Global and Comparative Ontologies

African Ontologies
Indigenous Ontologies
Buddhist Concepts of Being
Jain Concepts of Reality
Confucian Ontology
Daoist Ontology
Islamic Ontology (Contemporary)
Latin American Ontologies
Comparative Ontology
Planetary Ontology

The Modern ontology has become a meeting ground for metaphysics, science, religion, mathematics, information science, anthropology, ecology, and artificial intelligence.

Volume IV: Metaontology

Metaontology examines the nature and methodology of ontology itself.

Topics:

What is an ontological question?
How are ontological disputes settled?
Quantification and existence
Ontological commitment
Ontological parsimony
Ockham’s Razor
Conceptual engineering
Carnap–Quine debates
Deflationary ontology
Neo-Aristotelian ontology

Metaontology increasingly functions as the “philosophy of ontology.”

Volume V: Fundamental Ontology

Associated especially with Martin Heidegger.

Topics:

Being versus beings
Dasein
Temporality
Being-in-the-world
Ontological difference
Authenticity
Historicity
Care (Sorge)

This tradition influenced existentialism, hermeneutics, and continental philosophy.

Volume VI: Ontology of Mathematics

Questions include:

Do numbers exist
Are mathematical objects discovered or invented?
What is the ontological status of infinity?

Topics:

Platonism
Mathematical realism
Fictionalism
Structuralism
Set-theoretic ontology
Category-theoretic ontology
Infinity
Abstract objects
Mathematical Philosophy

Topics:

Numbers
Geometrical Objects
Structures

Question: Do mathematical entities exist independently of human thought?

Volume VII: Religious and Sacred Ontologies

Most encyclopedias treat these only historically, but they deserve systematic treatment.

Topics:

Divine Being
God and existence
Creation
Angels
Souls
Spiritual entities
Sacred space
Sacred time
Eschatological realities

Comparative sections:

Hindu ontology
Buddhist ontology
Jain ontology
Christian ontology
Islamic ontology
Jewish ontology
Indigenous sacred ontologies

Volume VIII: Ecological Ontology

A rapidly growing field.

Topics:

Nature and existence
Ecological being
Deep ecology
Gaia hypothesis
More-than-human worlds
Environmental realism
Animal ontology
Plant ontology
Ecosystem ontology

Key question: What kinds of entities constitute the living world?

Volume XI: Ontology of Technology

Increasingly important since the twentieth century.

Topics:

Technological objects
Machines
Artifacts
Infrastructure
Digital entities
Technological mediation
Cybernetic systems
Autonomous technologies

Links strongly to AI and information science.

Volume X: Information Ontology

One of the fastest-growing ontological fields.

Topics:

Information as reality
Informational structures
Digital existence
Data objects
Semantic entities
Computational worlds
Virtual entities
Digital twins

Associated with contemporary philosophers such as Luciano Floridi.

Ontology of Artificial Intelligence

Potentially an entire section by itself.

Topics:

Artificial agents
Machine personhood
Synthetic minds
Artificial consciousness
Computational existence
Autonomous systems
Robot ontology
Hybrid human-machine entities
Digital selves

Questions include: Can a machine genuinely exist as a person?

Greatly expanded in recent decades.

Topics:

Institutions
Money
Corporations
Governments
Nations
Social facts
Collective intentionality
Social identities

Associated with the work of John Searle.

Ontology of Culture

Topics:

Traditions
Myths
Symbols
Rituals
Collective memory
Heritage
Civilizational identities
Cultural artifacts

This area connects ontology with anthropology and history.

Ontology of Personhood

A major interdisciplinary field.

Topics:

Human person
Selfhood
Identity
Consciousness
Embodiment
Gender
Agency
Moral personhood
Posthuman personhood

Ontology of Death and Non-Existence

Often overlooked but philosophically central.

Topics:

Death
Nothingness
Absence
Negation
Non-being
Extinction
Void
Annihilation

Beginning with Parmenides, debates over non-being have remained central to ontology.

Comparative Civilizational Ontologies

Instead of treating traditions merely as historical chapters, compare their ontological assumptions.

Indic Ontologies

Brahman
Ātman
Dharma
Karma
Prakriti
Purusha

Chinese Ontologies

Dao
Qi
Yin-Yang
Heaven and Earth

African Ontologies

Vital force
Ancestors
Communal being
Relational existence

Indigenous Ontologies

Animism
Kinship cosmologies
Land-based realities
Multi-species worlds

Future Ontology

Topics:

Posthuman existence
Space civilization ontology
Extraterrestrial intelligence
Virtual civilizations
Simulated realities
Planetary consciousness
Synthetic life
Digital immortality

Central question: What kinds of beings may exist in the future that do not exist today?

Volume XII: Ontology’s Deep Structure

Most treatments organize ontology around entities (things that exist). A more comprehensive approach organizes it around the major dimensions of being.

Ontology of Being

Fundamental questions:

What is being?
Why is there something rather than nothing?
Is existence a property?
Can non-being be thought?

Core entries:

Being
Existence
Non-Existence
Becoming
Reality
Presence
Absence
Nothingness
Possibility
Actuality

This becomes the deepest layer of the encyclopedia.

Ontology of Categories

Every civilization classifies reality differently.

Core entries:

Categories
Substance
Attribute
Relation
Event
Process
State
Object
System
Structure

Cross-links:

Aristotle → Categories

Buddhism → Processes

Modern Physics → Fields

Information Science → Structures

Ontology of Objects

Questions:

What is an object?
When does an object begin and end?
Are objects fundamental?

Subdivisions:

Physical Objects

Stones
Mountains
Rivers
Organisms
Artifacts

Abstract Objects

Numbers
Sets
Laws
Propositions

Social Objects

Nations
Corporations
Universities
Money

Digital Objects

Files
Databases
Avatars
Digital Identities

Ontology of Properties

A surprisingly vast area.

Topics:

Universals
Particulars
Tropes
Qualities
Powers
Capacities
Dispositions

Question: Do redness, beauty, or intelligence exist independently of things?

Ontology of Relations

Many modern philosophers argue relations are more fundamental than objects.

Topics:

Relations
Networks
Dependencies
Interactions
Systems
Structures

Cross-links:

Quantum Physics

Systems Theory

Ecology

Social Networks

Artificial Intelligence

Ontology of Process

Instead of asking what things are, process philosophers ask what things become.

Key figures:

Heraclitus
Alfred North Whitehead
Henri Bergson

Topics:

Process
Becoming
Change
Flux
Development
Evolution

This is increasingly influential in biology and ecology.

VOLUME XIII: Ontology of Nature

Cosmological Ontology

Topics:

Universe
Multiverse
Space
Time
Matter
Energy
Dark Matter
Dark Energy

Geological Ontology

Topics:

Earth Systems
Landscapes
Geological Time
Planetary Processes

Biological Ontology

Topics:

Life
Organism
Species
Evolution
Ecosystems

VOLUME XIV: Ontology of Life

One of the oldest unresolved questions.

Topics:

Living Being
Organism
Vitalism
Emergence
Biological Individuality
Species

Question:

What distinguishes life from non-life?

VOLUME XV: Ontology of Mind

Perhaps the largest contemporary area.

Topics:

Consciousness
Self
Mind
Thought
Experience
Intentionality
Agency
Free Will

Cross-links:

Psychology

Neuroscience

Artificial Intelligence

Phenomenology

VOLUME XVI: Ontology of Human Existence

Distinct from philosophy of mind.

Topics:

Personhood
Identity
Embodiment
Mortality
Freedom
Meaning
Alienation
Authenticity

Major traditions:

Existentialism
Phenomenology
Religious Anthropology

VOLUME XVII: Ontology of Society

An enormous field today.

Topics:

Institutions
Law
Property
Markets
Governments
Nations
Communities
Social Roles

Question:

Are societies real entities or merely collections of individuals?

VOLUME XVIII: Ontology of Culture

Topics:

Myth
Ritual
Tradition
Language
Symbols
Collective Memory

This links ontology with anthropology and history.

VOLUME XIX: Ontology of Knowledge

An area often separated into epistemology but ontologically important.

Topics:

Knowledge as Entity
Information
Meaning
Truthmakers
Facts

Question:

Do facts exist independently of minds?

VOLUME XX: Ontology of Values

Often neglected.

Topics:

Goodness
Beauty
Justice
Rights
Duties

Question:

Do values exist objectively?

This connects ontology with ethics and aesthetics.

VOLUME XXI: Ontology of Religion

One of the oldest forms of ontology.

Topics:

God
Divine Being
Soul
Spirit
Angels
Demons
Sacred Reality
Afterlife

Comparative sections:

Hindu Ontology
Buddhist Ontology
Christian Ontology
Islamic Ontology
Indigenous Ontologies

VOLUME XXII: Ontology of Language

Topics:

Meaning
Reference
Signs
Symbols
Texts
Narratives

Question: What kind of thing is a word?

VOLUME XXIII: Ontology of Artificial Entities

Likely to become one of the largest future sections.

Topics:

Artificial Agents
Robots
Virtual Persons
Digital Minds
Synthetic Consciousness
Autonomous Systems

Question:

Can an artificial entity possess genuine existence?

VOLUME XXIV:Ontology of Virtual Worlds

A field barely imaginable before the late twentieth century.

Topics:

Virtual Reality
Augmented Reality
Metaverse
Digital Twins
Online Communities
Simulated Worlds

Question:

Are virtual entities less real than physical entities?

VOLUME XXV: Ontology of the Future

Potentially the encyclopedia’s most distinctive contribution.

Space Ontology

Extraterrestrial Life
Planetary Civilizations
Cosmic Intelligence

Posthuman Ontology

Cyborgs
Human Enhancement
Mind Uploading
Synthetic Biology

Existential Ontology

Long-Term Future
Human Survival
Civilizational Persistence

Speculative Ontology

Simulated Universes
Alternate Realities
Artificial Worlds
Unknown Forms of Being

Sarvarthapedia Knowledge Web: Master Philosophical Nexus

Metaphysics

Central Question:

What is the fundamental nature of reality?

See also:

Ontology
Epistemology
Being
Reality
Existence
Substance
Identity
Causation
Space
Time
Possibility
Necessity

Ontology

Central Question:

What exists?

See also:

Metaphysics
Being
Existence
Reality
Categories
Objects
Properties
Relations
Processes
Events
Identity

Epistemology

Central Question:

How do we know what exists?

See also:

Knowledge
Belief
Truth
Justification
Evidence
Rationality
Perception
Experience
Testimony
Skepticism

Foundational Triangle

Metaphysics ↔ Ontology

Ontology ↔ Epistemology

Epistemology ↔ Metaphysics

Reality ↔ Existence ↔ Knowledge

Being ↔ Truth ↔ Justification

Being and Existence Cluster

Being

Core Hub

See also:

Existence
Reality
Becoming
Presence
Absence
Essence
Identity
Substance
Non-Being

Existence

See also:

Being
Reality
Actuality
Possibility
Necessity
Ontological Commitment
Categories of Being

Reality

See also:

Appearance
Truth
Objectivity
Existence
Being
Metaphysics
Realism

Non-Being

See also:

Nothingness
Absence
Negation
Becoming
Possibility

Becoming

See also:

Change
Process
Time
Evolution
Emergence

Categories of Reality Cluster

Substance

See also:

Essence
Property
Object
Identity
Aristotle
Substance Theory

Property

See also:

Universals
Tropes
Qualities
Powers
Attributes

Relation

See also:

Networks
Structures
Dependencies
Systems
Social Reality

Event

See also:

Process
Change
Time
Causation

Process

See also:

Becoming
Event
Evolution
Process Ontology
Emergence

Objects and Entities Cluster

Object

Master Classification Hub

See also:

Physical Objects
Abstract Objects
Social Objects
Digital Objects
Properties
Identity

Physical Objects

See also:

Matter
Organism
Space
Time
Physics

Abstract Objects

See also:

Numbers
Sets
Logic
Mathematics
Universals

Social Objects

See also:

Institutions
Money
States
Law
Collective Intentionality

Digital Objects

See also:

Data
Algorithms
Virtual Reality
Artificial Intelligence
Information

Identity and Persistence Cluster

Identity

See also:

Difference
Personhood
Self
Persistence
Essence

Personal Identity

See also:

Self
Consciousness
Memory
Embodiment
Narrative Identity

Persistence

See also:

Time
Change
Endurantism
Perdurantism

Essence

See also:

Substance
Essentialism
Identity
Existence

Space, Time, and Cosmos Cluster

Space

See also:

Time
Cosmology
Matter
Universe
Space-Time

Time

See also:

Change
Becoming
Persistence
History
Eternity

Universe

See also:

Cosmological Ontology
Matter
Energy
Space
Time

Cosmological Ontology

See also:

Universe
Multiverse
Dark Matter
Dark Energy
Planetary Ontology

Causation and Modal Reality Cluster

Causation

See also:

Determinism
Explanation
Change
Dependence
Emergence

Necessity

See also:

Possibility
Modal Ontology
Essentialism
Laws of Nature

Possibility

See also:

Possible Worlds
Counterfactuals
Future Ontologies
Non-Being

Modal Ontology

See also:

Possible Worlds
Necessity
Possibility
Fictional Entities

Mind and Consciousness Cluster

Mind

See also:

Consciousness
Self
Intentionality
Thought
Experience

Consciousness

See also:

Mind
Self
Phenomenology
Cognitive Ontology
Artificial Consciousness

Self

See also:

Personal Identity
Consciousness
Agency
Embodiment

Intentionality

See also:

Meaning
Representation
Mind
Knowledge

Human Existence Cluster

Personhood

See also:

Self
Identity
Consciousness
Rights
Moral Agency

Freedom

See also:

Agency
Determinism
Responsibility
Existentialism

Mortality

See also:

Death
Meaning
Human Existence
Religion

Authenticity

See also:

Existentialism
Selfhood
Freedom
Human Condition

Knowledge and Reality Cluster

Knowledge

Bridge Node Between Ontology and Epistemology

See also:

Truth
Belief
Justification
Facts
Information

Truth

See also:

Reality
Facts
Knowledge
Correspondence
Realism

Facts

See also:

Truthmakers
Reality
Knowledge
States of Affairs

Information

See also:

Knowledge
Data
Computation
Information Ontology

Mathematics and Abstract Reality Cluster

Mathematical Objects

See also:

Numbers
Sets
Infinity
Structures
Abstract Objects

Infinity

See also:

Mathematics
Cosmology
Possibility
Abstract Reality

Structuralism

See also:

Mathematical Structures
Information Ontology
Ontic Structural Realism

Society and Culture Cluster

Social Reality

See also:

Institutions
Collective Intentionality
Social Kinds
Political Ontology

Institution

See also:

Law
Government
Property
Organizations

Culture

See also:

Myth
Ritual
Tradition
Symbols
Collective Memory

Civilization

See also:

Culture
Religion
Knowledge Systems
Historical Ontologies

Religion and Sacred Reality Cluster

Divine Being

See also:

God
Sacred Reality
Theology
Religious Ontology

Soul

See also:

Mind
Personhood
Afterlife
Consciousness

Sacred Reality

See also:

Myth
Ritual
Divine Being
Religious Experience

Comparative Religious Ontologies

See also:

Hindu Ontology
Buddhist Ontology
Christian Ontology
Islamic Ontology
Indigenous Ontologies

Nature and Life Cluster

Life

See also:

Organism
Evolution
Biological Ontology
Emergence

Organism

See also:

Species
Ecology
Biological Individuality

Ecology

See also:

Environment
Systems Theory
Process Ontology
Planetary Ontology

Evolution

See also:

Change
Emergence
Life
Biological Ontology

Information and Digital Reality Cluster

Information Ontology

See also:

Data
Knowledge
Computation
Digital Reality

Computation

See also:

Algorithms
Artificial Intelligence
Information Processing

Digital Reality

See also:

Virtual Reality
Metaverse
Digital Objects
Simulated Worlds

Virtual Reality

See also:

Digital Reality
Simulation
Artificial Environments

Artificial Intelligence Cluster

Artificial Intelligence

Master Future-Oriented Hub

See also:

Machine Ontology
Artificial Agents
Knowledge Representation
Human-AI Relations

Artificial Agents

See also:

Agency
Autonomous Systems
Machine Learning

Synthetic Persons

See also:

Personhood
Consciousness
Artificial Intelligence
Posthuman Ontology

Knowledge Representation

See also:

Logic
Information
Semantic Systems
Epistemology

Comparative Ontologies Cluster

Indian Ontologies

See also:

Brahman
Ātman
Dharma
Karma
Nyāya
Vedānta

Buddhist Ontologies

See also:

Emptiness
Impermanence
Dependent Origination
Process Ontology

Chinese Ontologies

See also:

Dao
Qi
Yin-Yang
Confucian Reality

African Ontologies

See also:

Vital Force
Communal Being
Ancestors
Relational Reality

Indigenous Ontologies

See also:

Animism
Land-Based Knowledge
Ecological Reality
Sacred Geography

Future and Speculative Ontology Cluster

Posthuman Ontology

See also:

Human Enhancement
Cyborgs
Synthetic Persons
Digital Minds

Space Ontology

See also:

Extraterrestrial Life
Planetary Ontology
Cosmology
Future Civilizations

Simulated Reality

See also:

Virtual Reality
Information Ontology
Artificial Worlds

Future Ontologies

See also:

Posthumanity
Artificial Intelligence
Planetary Futures
Unknown Forms of Being

Ultimate Sarvarthapedia Reality Web

First-Order Nodes

Being
Existence
Reality
Knowledge

Second-Order Nodes

Substance
Object
Property
Relation
Process
Event

Third-Order Nodes

Mind
Life
Society
Culture
Mathematics
Religion
Information

Fourth-Order Nodes

Artificial Intelligence
Digital Reality
Virtual Worlds
Posthumanity
Planetary Existence

Integrative Principle

Being → Existence → Reality

Reality → Knowledge → Truth

Objects → Relations → Systems

Life → Mind → Society → Culture

Information → Computation → Artificial Intelligence

Humanity → Technology → Future Forms of Being

This network allows every Sarvarthapedia article on metaphysics, ontology, and epistemology to connect horizontally across disciplines and vertically from foundational concepts of being to the most advanced questions concerning digital, artificial, and future realities.