Ontology
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Ontology is the philosophical study of
being Existence is the state of having being or reality in contrast to nonexistence and nonbeing. Existence is often contrasted with essence: the essence of an entity is its essential features or qualities, which can be understood even if one do ...
. It is traditionally understood as the subdiscipline of
metaphysics Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of ...
focused on the most general features of
reality Reality is the sum or aggregate of everything in existence; everything that is not imagination, imaginary. Different Culture, cultures and Academic discipline, academic disciplines conceptualize it in various ways. Philosophical questions abo ...
. As one of the most fundamental concepts, being encompasses all of reality and every
entity An entity is something that Existence, exists as itself. It does not need to be of material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is Lif ...
within it. To articulate the basic structure of being, ontology examines the commonalities among all things and investigates their classification into basic types, such as the
categories Category, plural categories, may refer to: General uses *Classification, the general act of allocating things to classes/categories Philosophy *Category of being * ''Categories'' (Aristotle) *Category (Kant) *Categories (Peirce) *Category (Vais ...
of
particular In metaphysics, particulars or individuals are usually contrasted with ''universals''. Universals concern features that can be exemplified by various different particulars. Particulars are often seen as concrete, spatiotemporal entities as opposed ...
s and
universals In metaphysics, a universal is what particular things have in common, namely characteristics or qualities. In other words, universals are repeatable or recurrent entities that can be instantiated or exemplified by many particular things. For exa ...
. Particulars are unique, non-repeatable entities, such as the person
Socrates Socrates (; ; – 399 BC) was a Ancient Greek philosophy, Greek philosopher from Classical Athens, Athens who is credited as the founder of Western philosophy and as among the first moral philosophers of the Ethics, ethical tradition ...
, whereas universals are general, repeatable entities, like the color ''green''. Another distinction exists between
concrete Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
objects existing in
space and time In physics, spacetime, also called the space-time continuum, is a mathematical model that fuses the three dimensions of space and the one dimension of time into a single four-dimensional continuum. Spacetime diagrams are useful in visualizing ...
, such as a tree, and abstract objects existing outside space and time, like the number 7. Systems of categories aim to provide a comprehensive inventory of reality by employing categories such as
substance Substance may refer to: * Matter, anything that has mass and takes up space Chemistry * Chemical substance, a material with a definite chemical composition * Drug, a chemical agent affecting an organism Arts, entertainment, and media Music * ' ...
,
property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right to consume, alter, share, re ...
,
relation Relation or relations may refer to: General uses * International relations, the study of interconnection of politics, economics, and law on a global level * Interpersonal relationship, association or acquaintance between two or more people * ...
, state of affairs, and
event Event may refer to: Gatherings of people * Ceremony, an event of ritual significance, performed on a special occasion * Convention (meeting), a gathering of individuals engaged in some common interest * Event management, the organization of eve ...
. Ontologists disagree regarding which entities exist at the most basic level.
Platonic realism The Theory of Forms or Theory of Ideas, also known as Platonic idealism or Platonic realism, is a philosophical theory credited to the Classical Greek philosopher Plato. A major concept in metaphysics, the theory suggests that the physical w ...
asserts that universals have objective existence, while
conceptualism In metaphysics, conceptualism is a theory that explains universality of particulars as conceptualized frameworks situated within the thinking mind. Intermediate between nominalism and realism, the conceptualist view approaches the metaphysical ...
maintains that universals exist only in the mind, and
nominalism In metaphysics, nominalism is the view that universals and abstract objects do not actually exist other than being merely names or labels. There are two main versions of nominalism. One denies the existence of universals—that which can be inst ...
denies their existence altogether. Similar disputes pertain to
mathematical object A mathematical object is an abstract concept arising in mathematics. Typically, a mathematical object can be a value that can be assigned to a Glossary of mathematical symbols, symbol, and therefore can be involved in formulas. Commonly encounter ...
s,
unobservable An unobservable (also called impalpable) is an entity whose existence, nature, properties, qualities or relations are not directly observable by humans. In philosophy of science, typical examples of "unobservables" are the force of gravity, causa ...
objects assumed by scientific theories, and moral facts.
Materialism Materialism is a form of monism, philosophical monism according to which matter is the fundamental Substance theory, substance in nature, and all things, including mind, mental states and consciousness, are results of material interactions. Acco ...
posits that fundamentally only
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...
exists, whereas
dualism Dualism most commonly refers to: * Mind–body dualism, a philosophical view which holds that mental phenomena are, at least in certain respects, not physical phenomena, or that the mind and the body are distinct and separable from one another * P ...
asserts that
mind The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances ...
and matter are independent principles. According to some ontologists, objective answers to ontological questions do not exist, with perspectives shaped by differing linguistic practices. Ontology employs diverse methods of inquiry, including the analysis of
concepts A concept is an abstract idea that serves as a foundation for more concrete principles, thoughts, and beliefs. Concepts play an important role in all aspects of cognition. As such, concepts are studied within such disciplines as linguistics, psy ...
and
experience Experience refers to Consciousness, conscious events in general, more specifically to perceptions, or to the practical knowledge and familiarity that is produced by these processes. Understood as a conscious event in the widest sense, experience i ...
, the use of
intuition Intuition is the ability to acquire knowledge without recourse to conscious reasoning or needing an explanation. Different fields use the word "intuition" in very different ways, including but not limited to: direct access to unconscious knowledg ...
s and
thought experiment A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is ...
s, and the integration of findings from
natural science Natural science or empirical science is one of the branches of science concerned with the description, understanding and prediction of natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer ...
.
Formal ontology In philosophy, the term formal ontology is used to refer to an ontology defined by axioms in a formal language with the goal to provide an unbiased (Problem domain, domain- and application-independent) view on Reality#Western philosophy, realit ...
investigates the most abstract features of objects, while Applied ontology utilizes ontological theories and principles to study entities within specific domains. For example,
social ontology Social ontology is a branch of ontology. Ontology is the philosophical study of being and existence; social ontology, specifically, examines the social world, and the entities that arise out of social interaction. A primary concern of social ontolo ...
examines basic concepts used in the
social sciences Social science (often rendered in the plural as the social sciences) is one of the branches of science, devoted to the study of society, societies and the Social relation, relationships among members within those societies. The term was former ...
. Applied ontology is particularly relevant to
information Information is an Abstraction, abstract concept that refers to something which has the power Communication, to inform. At the most fundamental level, it pertains to the Interpretation (philosophy), interpretation (perhaps Interpretation (log ...
and
computer science Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
, which develop conceptual frameworks of limited domains. These frameworks facilitate the structured storage of information, such as in a college database tracking academic activities. Ontology is also pertinent to the fields of
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
,
theology Theology is the study of religious belief from a Religion, religious perspective, with a focus on the nature of divinity. It is taught as an Discipline (academia), academic discipline, typically in universities and seminaries. It occupies itse ...
, and
anthropology Anthropology is the scientific study of humanity, concerned with human behavior, human biology, cultures, society, societies, and linguistics, in both the present and past, including archaic humans. Social anthropology studies patterns of behav ...
. The origins of ontology lie in the
ancient period Ancient history is a time period from the beginning of writing and recorded human history through late antiquity. The span of recorded history is roughly 5,000 years, beginning with the development of Sumerian cuneiform script. Ancient h ...
with speculations about the nature of being and the source of the universe, including ancient Indian, Chinese, and
Greek philosophy Ancient Greek philosophy arose in the 6th century BC. Philosophy was used to make sense of the world using reason. It dealt with a wide variety of subjects, including astronomy, epistemology, mathematics, political philosophy, ethics, metaphysic ...
. In the modern period, philosophers conceived ontology as a distinct academic discipline and coined its name.


Definition

Ontology is the study of being. It is the branch of
philosophy Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational an ...
that investigates the nature of
existence Existence is the state of having being or reality in contrast to nonexistence and nonbeing. Existence is often contrasted with essence: the essence of an entity is its essential features or qualities, which can be understood even if one does ...
, the features all entities have in common, and how they are divided into basic
categories of being In ontology, the theory of categories concerns itself with the ''categories of being'': the highest ''genera'' or ''kinds of entities''. To investigate the categories of being, or simply categories, is to determine the most fundamental and the br ...
. It aims to discover the foundational building blocks of the world and characterize
reality Reality is the sum or aggregate of everything in existence; everything that is not imagination, imaginary. Different Culture, cultures and Academic discipline, academic disciplines conceptualize it in various ways. Philosophical questions abo ...
as a whole in its most general aspects. In this regard, ontology contrasts with individual sciences like
biology Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...
and
astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
, which restrict themselves to a limited domain of entities, such as living entities and celestial phenomena. In some contexts, the term ''ontology'' refers not to the general study of being but to a specific ontological theory within this discipline. It can also mean an inventory or a conceptual scheme of a particular domain, such as the ontology of genes. In this context, an inventory is a comprehensive list of elements. A conceptual scheme is a framework of the key concepts and their relationships. Ontology is closely related to
metaphysics Metaphysics is the branch of philosophy that examines the basic structure of reality. It is traditionally seen as the study of mind-independent features of the world, but some theorists view it as an inquiry into the conceptual framework of ...
but the exact relation of these two disciplines is disputed. A traditionally influential characterization asserts that ontology is a subdiscipline of metaphysics. According to this view, metaphysics is the study of various aspects of fundamental reality, whereas ontology restricts itself to the most general features of reality. This view sees ontology as general metaphysics, which is to be distinguished from special metaphysics focused on more specific subject matters, like
God In monotheistic belief systems, God is usually viewed as the supreme being, creator, and principal object of faith. In polytheistic belief systems, a god is "a spirit or being believed to have created, or for controlling some part of the un ...
,
mind The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances ...
, and value. A different conception understands ontology as a preliminary discipline that provides a complete inventory of reality while metaphysics examines the features and structure of the entities in this inventory. Another conception says that metaphysics is about real being while ontology examines possible being or the concept of being. It is not universally accepted that there is a clear boundary between metaphysics and ontology. Some philosophers use both terms as synonyms. The etymology of the word ''ontology'' traces back to the
ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
terms (, meaning ) and (, meaning ), literally, . The ancient Greeks did not use the term ''ontology'', which was coined by philosophers in the 17th century.


Basic concepts


Being

Being, or
existence Existence is the state of having being or reality in contrast to nonexistence and nonbeing. Existence is often contrasted with essence: the essence of an entity is its essential features or qualities, which can be understood even if one does ...
, is the main topic of ontology. It is one of the most general and fundamental concepts, encompassing all of
reality Reality is the sum or aggregate of everything in existence; everything that is not imagination, imaginary. Different Culture, cultures and Academic discipline, academic disciplines conceptualize it in various ways. Philosophical questions abo ...
and every
entity An entity is something that Existence, exists as itself. It does not need to be of material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is Lif ...
within it. In its broadest sense, being only contrasts with non-being or nothingness. It is controversial whether a more substantial analysis of the concept or meaning of being is possible. One proposal understands being as a property possessed by every entity. Critics argue that a thing without being cannot have properties. This means that properties presuppose being and cannot explain it. Another suggestion is that all beings share a set of essential features. According to the Eleatic principle, "power is the mark of being", meaning that only entities with
causal Causality is an influence by which one Event (philosophy), event, process, state, or Object (philosophy), object (''a'' ''cause'') contributes to the production of another event, process, state, or object (an ''effect'') where the cause is at l ...
influence truly exist. A controversial proposal by philosopher
George Berkeley George Berkeley ( ; 12 March 168514 January 1753), known as Bishop Berkeley (Bishop of Cloyne of the Anglican Church of Ireland), was an Anglo-Irish philosopher, writer, and clergyman who is regarded as the founder of "immaterialism", a philos ...
suggests that all existence is mental. He expressed this
immaterialism Subjective idealism, or empirical idealism or immaterialism, is a form of philosophical monism that holds that only minds and mental contents exist. It entails and is generally identified or associated with immaterialism, the doctrine that m ...
in his slogan "to be is to be perceived". Depending on the context, the term ''being'' is sometimes used with a more limited meaning to refer only to certain aspects of reality. In one sense, being is unchanging and permanent, in contrast to becoming, which implies change. Another contrast is between being, as what truly exists, and
phenomena A phenomenon ( phenomena), sometimes spelled phaenomenon, is an observable Event (philosophy), event. The term came into its modern Philosophy, philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be ...
, as what appears to exist. In some contexts, being expresses the fact that something is while
essence Essence () has various meanings and uses for different thinkers and in different contexts. It is used in philosophy and theology as a designation for the property (philosophy), property or set of properties or attributes that make an entity the ...
expresses its qualities or what it is like. Ontologists often divide being into fundamental classes or highest kinds, called ''
categories of being In ontology, the theory of categories concerns itself with the ''categories of being'': the highest ''genera'' or ''kinds of entities''. To investigate the categories of being, or simply categories, is to determine the most fundamental and the br ...
''. Proposed categories include substance,
property Property is a system of rights that gives people legal control of valuable things, and also refers to the valuable things themselves. Depending on the nature of the property, an owner of property may have the right to consume, alter, share, re ...
,
relation Relation or relations may refer to: General uses * International relations, the study of interconnection of politics, economics, and law on a global level * Interpersonal relationship, association or acquaintance between two or more people * ...
, state of affairs, and
event Event may refer to: Gatherings of people * Ceremony, an event of ritual significance, performed on a special occasion * Convention (meeting), a gathering of individuals engaged in some common interest * Event management, the organization of eve ...
. They can be used to provide systems of categories, which offer a comprehensive inventory of reality in which every entity belongs to exactly one category. Some philosophers, like
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
, say that entities belonging to different categories exist in distinct ways. Others, like
John Duns Scotus John Duns Scotus ( ; , "Duns the Scot";  – 8 November 1308) was a Scottish Catholic priest and Franciscan friar, university professor, philosopher and theologian. He is considered one of the four most important Christian philosopher-t ...
, insist that there are no differences in the mode of being, meaning that everything exists in the same way. A related dispute is whether some entities have a higher degree of being than others, an idea already found in
Plato Plato ( ; Greek language, Greek: , ; born  BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
's work. The more common view in contemporary philosophy is that a thing either exists or not with no intermediary states or degrees. The relation between being and non-being is a frequent topic in ontology. Influential issues include the status of
nonexistent objects In metaphysics and ontology, nonexistent objects are a concept advanced by Austrian philosopher Alexius Meinong in the 19th and 20th centuries within a " theory of objects". He was interested in intentional states which are directed at nonexiste ...
and why there is something rather than nothing.


Particulars and universals

A central distinction in ontology is between particular and universal entities. Particulars, also called ''individuals'', are unique, non-repeatable entities, like
Socrates Socrates (; ; – 399 BC) was a Ancient Greek philosophy, Greek philosopher from Classical Athens, Athens who is credited as the founder of Western philosophy and as among the first moral philosophers of the Ethics, ethical tradition ...
, the
Taj Mahal The Taj Mahal ( ; ; ) is an ivory-white marble mausoleum on the right bank of the river Yamuna in Agra, Uttar Pradesh, India. It was commissioned in 1631 by the fifth Mughal Empire, Mughal emperor, Shah Jahan () to house the tomb of his belo ...
, and
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
. Universals are general, repeatable entities, like the color ''green'', the form ''circularity'', and the virtue ''courage''. Universals express aspects or features shared by particulars. For example,
Mount Everest Mount Everest (), known locally as Sagarmatha in Nepal and Qomolangma in Tibet, is Earth's highest mountain above sea level. It lies in the Mahalangur Himal sub-range of the Himalayas and marks part of the China–Nepal border at it ...
and
Mount Fuji is an active stratovolcano located on the Japanese island of Honshu, with a summit elevation of . It is the highest mountain in Japan, the second-highest volcano on any Asian island (after Mount Kerinci on the Indonesian island of Sumatra), a ...
are particulars characterized by the universal ''mountain''. Universals can take the form of properties or relations. Properties describe the characteristics of things. They are features or qualities possessed by an entity. Properties are often divided into essential and accidental properties. A property is essential if an entity must have it; it is accidental if the entity can exist without it. For instance, ''having three sides'' is an essential property of a triangle, whereas ''being red'' is an accidental property. Relations are ways how two or more entities stand to one another. Unlike properties, they apply to several entities and characterize them as a group. For example, ''being a city'' is a property while ''being east of'' is a relation, as in "
Kathmandu Kathmandu () is the capital and largest city of Nepal, situated in the central part of the country within the Kathmandu Valley. As per the 2021 Nepal census, it has a population of 845,767 residing in 105,649 households, with approximately 4 mi ...
is a city" and "Kathmandu is east of
New Delhi New Delhi (; ) is the Capital city, capital of India and a part of the Delhi, National Capital Territory of Delhi (NCT). New Delhi is the seat of all three branches of the Government of India, hosting the Rashtrapati Bhavan, New Parliament ...
". Relations are often divided into internal and external relations. Internal relations depend only on the properties of the objects they connect, like the relation of resemblance. External relations express characteristics that go beyond what the connected objects are like, such as spatial relations. Substances play an important role in the history of ontology as the particular entities that underlie and support properties and relations. They are often considered the fundamental building blocks of reality that can exist on their own, while entities like properties and relations cannot exist without substances. Substances persist through changes as they acquire or lose properties. For example, when a tomato ripens, it loses the property ''green'' and acquires the property ''red''. States of affairs are complex particular entities that have several other entities as their components. The state of affairs "Socrates is wise" has two components: the individual ''Socrates'' and the property ''wise''. States of affairs that correspond to reality are called ''
fact A fact is a truth, true data, datum about one or more aspects of a circumstance. Standard reference works are often used to Fact-checking, check facts. Science, Scientific facts are verified by repeatable careful observation or measurement by ...
s''. Facts are truthmakers of statements, meaning that whether a statement is true or false depends on the underlying facts. Events are particular entities that occur in time, like the
fall of the Berlin Wall The fall of the Berlin Wall (, ) on 9 November in German history, 9 November 1989, during the Peaceful Revolution, marked the beginning of the destruction of the Berlin Wall and the figurative Iron Curtain, as East Berlin transit restrictions we ...
and the first moon landing. They usually involve some kind of change, like the lawn becoming dry. In some cases, no change occurs, like the lawn staying wet. Complex events, also called ''processes'', are composed of a sequence of events.


Concrete and abstract objects

Concrete objects are entities that exist in space and time, such as a tree, a car, and a planet. They have causal powers and can affect each other, like when a car hits a tree and both are deformed in the process. Abstract objects, by contrast, are outside space and time, such as the number 7 and the set of
integer An integer is the number zero (0), a positive natural number (1, 2, 3, ...), or the negation of a positive natural number (−1, −2, −3, ...). The negations or additive inverses of the positive natural numbers are referred to as negative in ...
s. They lack causal powers and do not undergo changes. The existence and nature of abstract objects remain subjects of philosophical debate. Concrete objects encountered in everyday life are complex entities composed of various parts. For example, a book is made up of two covers and the pages between them. Each of these components is itself constituted of smaller parts, like
molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...
s,
atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
s, and
elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons. As a c ...
s.
Mereology Mereology (; from Greek μέρος 'part' (root: μερε-, ''mere-'') and the suffix ''-logy'', 'study, discussion, science') is the philosophical study of part-whole relationships, also called ''parthood relationships''. As a branch of metaphys ...
studies the relation between parts and wholes. One position in mereology says that every collection of entities forms a whole. According to another view, this is only the case for collections that fulfill certain requirements, for instance, that the entities in the collection touch one another. The problem of material constitution asks whether or in what sense a whole should be considered a new object in addition to the collection of parts composing it. Abstract objects are closely related to fictional and intentional objects. Fictional objects are entities invented in works of
fiction Fiction is any creative work, chiefly any narrative work, portraying character (arts), individuals, events, or setting (narrative), places that are imagination, imaginary or in ways that are imaginary. Fictional portrayals are thus inconsistent ...
. They can be things, like the
One Ring The One Ring, also called the Ruling Ring and Isildur's Bane, is a central plot element in J. R. R. Tolkien's ''The Lord of the Rings'' (1954–55). It first appeared in the earlier story '' The Hobbit'' (1937) as a magic ring that grants the ...
in
J. R. R. Tolkien John Ronald Reuel Tolkien (, 3 January 1892 – 2 September 1973) was an English writer and philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was the Rawlinson ...
's book series
The Lord of the Rings ''The Lord of the Rings'' is an Epic (genre), epic high fantasy novel written by English author and scholar J. R. R. Tolkien. Set in Middle-earth, the story began as a sequel to Tolkien's 1937 children's book ''The Hobbit'' but eventually d ...
, and people, like the
Monkey King Sun Wukong (, Mandarin pronunciation: ), also known as the Monkey King, is a literary and religious figure best known as one of the main characters in the 16th-century Chinese novel ''Journey to the West''. In the novel, Sun Wukong is a monk ...
in the novel
Journey to the West ''Journey to the West'' () is a Chinese novel published in the 16th century during the Ming dynasty and attributed to Wu Cheng'en. It is regarded as one of the Classic Chinese Novels, great Chinese novels, and has been described as arguably the ...
. Some philosophers say that fictional objects are abstract objects and exist outside space and time. Others understand them as artifacts that are created as the works of fiction are written. Intentional objects are entities that exist within
mental states A mental state, or a mental property, is a state of mind of a person. Mental states comprise a diverse class, including perception, pain/pleasure experience, belief, desire, intention, emotion, and memory. There is controversy concerning the exact ...
, like
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous syste ...
s,
belief A belief is a subjective Attitude (psychology), attitude that something is truth, true or a State of affairs (philosophy), state of affairs is the case. A subjective attitude is a mental state of having some Life stance, stance, take, or opinion ...
s, and
desire Desires are states of mind that are expressed by terms like "wanting", "wishing", "longing" or "craving". A great variety of features is commonly associated with desires. They are seen as propositional attitudes towards conceivable states of affa ...
s. For example, if a person thinks about the
Loch Ness Monster The Loch Ness Monster (), known affectionately as Nessie, is a mythical creature in Scottish folklore that is said to inhabit Loch Ness in the Scottish Highlands. It is often described as large, long-necked, and with one or more humps protrud ...
then the Loch Ness Monster is the intentional object of this
thought In their most common sense, the terms thought and thinking refer to cognitive processes that can happen independently of sensory stimulation. Their most paradigmatic forms are judging, reasoning, concept formation, problem solving, and de ...
. People can think about existing and non-existing objects. This makes it difficult to assess the ontological status of intentional objects.


Other concepts

Ontological dependence is a relation between entities. An entity depends ontologically on another entity if the first entity cannot exist without the second entity. For instance, the surface of an apple cannot exist without the apple. An entity is ontologically independent if it does not depend on anything else, meaning that it is fundamental and can exist on its own. Ontological dependence plays a central role in ontology and its attempt to describe reality on its most fundamental level. It is closely related to metaphysical grounding, which is the relation between a ground and the facts it explains. An
ontological commitment Ontology is the philosophical study of being. It is traditionally understood as the subdiscipline of metaphysics focused on the most general features of reality. As one of the most fundamental concepts, being encompasses all of reality and every ...
of a person or a theory is an entity that exists according to them. For instance, a person who believes in God has an ontological commitment to
God In monotheistic belief systems, God is usually viewed as the supreme being, creator, and principal object of faith. In polytheistic belief systems, a god is "a spirit or being believed to have created, or for controlling some part of the un ...
. Ontological commitments can be used to analyze which ontologies people explicitly defend or implicitly assume. They play a central role in contemporary metaphysics when trying to decide between competing theories. For example, the
Quine–Putnam indispensability argument The Quine–Putnam indispensability argument is an argument in the philosophy of mathematics for the existence of Abstract and concrete, abstract mathematical objects such as numbers and sets, a position known as mathematical platonism. It was ...
defends
mathematical Platonism Mathematical Platonism is the form of realism that suggests that mathematical entities are abstract, have no spatiotemporal or causal properties, and are eternal and unchanging. This is often claimed to be the view most people have of numbers. ...
, asserting that numbers exist because the best scientific theories are ontologically committed to numbers. Possibility and necessity are further topics in ontology. Possibility describes what can be the case, as in "it is possible that
extraterrestrial life Extraterrestrial life, or alien life (colloquially, aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically conclusively detected. Such life might range from simple forms ...
exists". Necessity describes what must be the case, as in "it is necessary that three plus two equals five". Possibility and necessity contrast with actuality, which describes what is the case, as in "
Doha Doha ( ) is the capital city and main financial hub of Qatar. Located on the Persian Gulf coast in the east of the country, north of Al Wakrah and south of Al Khor (city), Al Khor and Lusail, it is home to most of the country's population. It ...
is the capital of
Qatar Qatar, officially the State of Qatar, is a country in West Asia. It occupies the Geography of Qatar, Qatar Peninsula on the northeastern coast of the Arabian Peninsula in the Middle East; it shares Qatar–Saudi Arabia border, its sole land b ...
". Ontologists often use the concept of
possible world A possible world is a complete and consistent way the world is or could have been. Possible worlds are widely used as a formal device in logic, philosophy, and linguistics in order to provide a semantics for intensional and modal logic. Their met ...
s to analyze possibility and necessity. A possible world is a complete and consistent way how things could have been. For example,
Haruki Murakami is a Japanese writer. His novels, essays, and short stories have been best-sellers in Japan and internationally, with his work translated into 50 languages and having sold millions of copies outside Japan. He has received numerous awards for hi ...
was born in 1949 in the actual world but there are possible worlds in which he was born at a different date. Using this idea,
possible world semantics A possible world is a complete and consistent way the world is or could have been. Possible worlds are widely used as a formal device in logic, philosophy, and linguistics in order to provide a semantics for intensional and modal logic. Their met ...
says that a sentence is possibly true if it is true in at least one possible world. A sentence is necessarily true if it is true in all possible worlds. The field of
modal logic Modal logic is a kind of logic used to represent statements about Modality (natural language), necessity and possibility. In philosophy and related fields it is used as a tool for understanding concepts such as knowledge, obligation, and causality ...
provides a precise formalization of the concepts of possibility and necessity. In ontology,
identity Identity may refer to: * Identity document * Identity (philosophy) * Identity (social science) * Identity (mathematics) Arts and entertainment Film and television * ''Identity'' (1987 film), an Iranian film * ''Identity'' (2003 film), an ...
means that two things are the same. Philosophers distinguish between qualitative and numerical identity. Two entities are qualitatively identical if they have exactly the same features, such as perfect identical twins. This is also called ''exact similarity'' and ''indiscernibility''. Numerical identity, by contrast, means that there is only a single entity. For example, if Fatima is the mother of Leila and Hugo then Leila's mother is numerically identical to Hugo's mother. Another distinction is between synchronic and diachronic identity. Synchronic identity relates an entity to itself at the same time. Diachronic identity relates an entity to itself at different times, as in "the woman who bore Leila three years ago is the same woman who bore Hugo this year". The notion of identity also has a number of philosophical implications in terms of how it interacts with the aforementioned necessity and possibility. Most famously, Saul Kripke contended that ''discovered identities'' such as "Water is H2O" are necessarily true because "H2O" is what's known as a
rigid designator In modal logic and the philosophy of language, a term is said to be a rigid designator or absolute substantial term when it designates (picks out, denotes, refers to) the same thing in ''all possible worlds'' in which that thing exists. A designato ...
.


Branches

There are different and sometimes overlapping ways to divide ontology into branches. Pure ontology focuses on the most abstract topics associated with the concept and nature of being. It is not restricted to a specific domain of entities and studies existence and the structure of reality as a whole. Pure ontology contrasts with applied ontology, also called domain ontology. Applied ontology examines the application of ontological theories and principles to specific disciplines and domains, often in the field of science. It considers ontological problems in regard to specific entities such as
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...
,
mind The mind is that which thinks, feels, perceives, imagines, remembers, and wills. It covers the totality of mental phenomena, including both conscious processes, through which an individual is aware of external and internal circumstances ...
,
number A number is a mathematical object used to count, measure, and label. The most basic examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual numbers can ...
s,
God In monotheistic belief systems, God is usually viewed as the supreme being, creator, and principal object of faith. In polytheistic belief systems, a god is "a spirit or being believed to have created, or for controlling some part of the un ...
, and cultural artifacts.
Social ontology Social ontology is a branch of ontology. Ontology is the philosophical study of being and existence; social ontology, specifically, examines the social world, and the entities that arise out of social interaction. A primary concern of social ontolo ...
, a major subfield of applied ontology, studies social kinds, like
money Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are: m ...
,
gender Gender is the range of social, psychological, cultural, and behavioral aspects of being a man (or boy), woman (or girl), or third gender. Although gender often corresponds to sex, a transgender person may identify with a gender other tha ...
,
society A society () is a group of individuals involved in persistent social interaction or a large social group sharing the same spatial or social territory, typically subject to the same political authority and dominant cultural expectations. ...
, and
language Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...
. It aims to determine the nature and essential features of these concepts while also examining their mode of existence. According to a common view, social kinds are useful constructions to describe the complexities of social life. This means that they are not pure fictions but, at the same time, lack the objective or mind-independent reality of natural phenomena like elementary particles, lions, and stars. In the fields of
computer science Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, ...
, information science, and
knowledge representation Knowledge representation (KR) aims to model information in a structured manner to formally represent it as knowledge in knowledge-based systems whereas knowledge representation and reasoning (KRR, KR&R, or KR²) also aims to understand, reason, and ...
, applied ontology is interested in the development of formal frameworks to encode and store information about a limited domain of entities in a structured way. A related application in
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...
is
Gene Ontology The Gene Ontology (GO) is a major bioinformatics initiative to unify the representation of gene and gene product attributes across all species. More specifically, the project aims to: 1) maintain and develop its controlled vocabulary of gene and ...
, which is a comprehensive framework for the standardized representation of gene-related information across species and databases.
Formal ontology In philosophy, the term formal ontology is used to refer to an ontology defined by axioms in a formal language with the goal to provide an unbiased (Problem domain, domain- and application-independent) view on Reality#Western philosophy, realit ...
is the study of objects in general while focusing on their abstract structures and features. It divides objects into different categories based on the forms they exemplify. Formal ontologists often rely on the tools of
formal logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
to express their findings in an abstract and general manner. Formal ontology contrasts with material ontology, which distinguishes between different areas of objects and examines the features characteristic of a specific area. Examples are ideal spatial beings in the area of geometry and living beings in the area of biology. Descriptive ontology aims to articulate the conceptual scheme underlying how people ordinarily think about the world. Prescriptive ontology departs from common conceptions of the structure of reality and seeks to formulate a new and better conceptualization. Another contrast is between analytic and speculative ontology. Analytic ontology examines the types and categories of being to determine what kinds of things could exist and what features they would have. Speculative ontology aims to determine which entities actually exist, for example, whether there are numbers or whether time is an illusion. Metaontology studies the underlying concepts, assumptions, and methods of ontology. Unlike other forms of ontology, it does not ask "what exists" but "what does it mean for something to exist" and "how can people determine what exists". It is closely related to
fundamental ontology In ''Being and Time'', the philosopher Martin Heidegger makes the distinction between ontical and ontological, or between ''beings'' and ''being'' as such. He labeled this the "ontological difference." It is from this distinction that he develops t ...
, an approach developed by philosopher
Martin Heidegger Martin Heidegger (; 26 September 1889 – 26 May 1976) was a German philosopher known for contributions to Phenomenology (philosophy), phenomenology, hermeneutics, and existentialism. His work covers a range of topics including metaphysics, art ...
that seeks to uncover the meaning of being.


Schools of thought


Realism and anti-realism

The term ''realism'' is used for various theories that affirm that some kind of phenomenon is real or has mind-independent existence. Ontological realism is the view that there are
objective Objective may refer to: * Objectivity, the quality of being confirmed independently of a mind. * Objective (optics), an element in a camera or microscope * ''The Objective'', a 2008 science fiction horror film * Objective pronoun, a personal pron ...
facts about what exists and what the nature and categories of being are. Ontological realists do not make claims about what those facts are, for example, whether elementary particles exist. They merely state that there are mind-independent facts that determine which ontological theories are true. This idea is denied by ontological anti-realists, also called ontological deflationists, who say that there are no substantive facts one way or the other. According to philosopher
Rudolf Carnap Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle and an advocate of logical positivism. ...
, for example, ontological statements are relative to language and depend on the ontological framework of the speaker. This means that there are no framework-independent ontological facts since different frameworks provide different views while there is no objectively right or wrong framework. In a more narrow sense, realism refers to the existence of certain types of entities. Realists about universals say that universals have mind-independent existence. According to Platonic realists, universals exist not only independent of the mind but also independent of particular objects that exemplify them. This means that the universal ''red'' could exist by itself even if there were no red objects in the world. Aristotelian realism, also called
moderate realism Moderate realism (also called immanent realism) is a position in the debate on the metaphysics of universals which holds that there is no realm in which universals exist (in opposition to Platonic realism, which asserts the existence of abstrac ...
, rejects this idea and says that universals only exist as long as there are objects that exemplify them.
Conceptualism In metaphysics, conceptualism is a theory that explains universality of particulars as conceptualized frameworks situated within the thinking mind. Intermediate between nominalism and realism, the conceptualist view approaches the metaphysical ...
, by contrast, is a form of anti-realism, stating that universals only exist in the mind as concepts that people use to understand and categorize the world.
Nominalists In metaphysics, nominalism is the view that universals and abstract objects do not actually exist other than being merely names or labels. There are two main versions of nominalism. One denies the existence of universals—that which can be inst ...
defend a strong form of anti-realism by saying that universals have no existence. This means that the world is entirely composed of particular objects.
Mathematical realism Philosophy of mathematics is the branch of philosophy that deals with the nature of mathematics and its relationship to other areas of philosophy, particularly epistemology and metaphysics. Central questions posed include whether or not mathem ...
, a closely related view in the
philosophy of mathematics Philosophy of mathematics is the branch of philosophy that deals with the nature of mathematics and its relationship to other areas of philosophy, particularly epistemology and metaphysics. Central questions posed include whether or not mathem ...
, says that mathematical facts exist independently of human language, thought, and practices and are discovered rather than invented. According to mathematical Platonism, this is the case because of the existence of
mathematical objects A mathematical object is an abstract concept arising in mathematics. Typically, a mathematical object can be a value that can be assigned to a symbol, and therefore can be involved in formulas. Commonly encountered mathematical objects include n ...
, like numbers and sets. Mathematical Platonists say that mathematical objects are as real as physical objects, like atoms and stars, even though they are not accessible to
empirical observation Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how the ...
. Influential forms of mathematical anti-realism include conventionalism, which says that mathematical theories are trivially true simply by how mathematical terms are defined, and game formalism, which understands mathematics not as a theory of reality but as a game governed by rules of string manipulation.
Modal realism Modal realism is the view propounded by the philosopher David Lewis that all possible worlds are real in the same way as is the actual world: they are "of a kind with this world of ours." It states that possible worlds exist, possible worlds are ...
is the theory that in addition to the actual world, there are countless
possible world A possible world is a complete and consistent way the world is or could have been. Possible worlds are widely used as a formal device in logic, philosophy, and linguistics in order to provide a semantics for intensional and modal logic. Their met ...
s as real and concrete as the actual world. The primary difference is that the actual world is inhabited by us while other possible worlds are inhabited by our counterparts. Modal anti-realists reject this view and argue that possible worlds do not have concrete reality but exist in a different sense, for example, as abstract or fictional objects. Scientific realists say that the scientific description of the world is an accurate representation of reality. It is of particular relevance in regard to things that cannot be directly observed by humans but are assumed to exist by scientific theories, like electrons, forces, and laws of nature.
Scientific anti-realism In analytic philosophy, anti-realism is the position that the truth of a statement rests on its demonstrability through internal logic mechanisms, such as the context principle or intuitionistic logic, in direct opposition to the realist notion t ...
says that scientific theories are not descriptions of reality but
instruments Instrument may refer to: Science and technology * Flight instruments, the devices used to measure the speed, altitude, and pertinent flight angles of various kinds of aircraft * Laboratory equipment, the measuring tools used in a scientific lab ...
to predict observations and the outcomes of experiments.
Moral realists A moral (from Latin ''morālis'') is a message that is conveyed or a lesson to be learned from a story or event. The moral may be left to the hearer, reader, or viewer to determine for themselves, or may be explicitly encapsulated in a maxim. ...
claim that there exist mind-independent moral facts. According to them, there are objective principles that determine which behavior is morally right. Moral anti-realists either claim that moral principles are subjective and differ between persons and cultures, a position known as
moral relativism Moral relativism or ethical relativism (often reformulated as relativist ethics or relativist morality) is used to describe several Philosophy, philosophical positions concerned with the differences in Morality, moral judgments across different p ...
, or outright deny the existence of moral facts, a view referred to as
moral nihilism Moral nihilism (also called ethical nihilism) is the metaethical view that nothing is morally right or morally wrong and that morality does not exist. Moral nihilism is distinct from moral relativism, which allows for actions to be wrong rel ...
.


By number of categories

Monocategorical theories say that there is only one fundamental category, meaning that every single entity belongs to the same universal class. For example, some forms of nominalism state that only concrete particulars exist while some forms of
bundle theory Bundle or Bundling may refer to: * Bundling (packaging), the process of using straps to bundle up items Biology * Bundle of His, a collection of heart muscle cells specialized for electrical conduction * Bundle of Kent, an extra conduction pa ...
state that only properties exist. Polycategorical theories, by contrast, hold that there is more than one basic category, meaning that entities are divided into two or more fundamental classes. They take the form of systems of categories, which list the highest genera of being to provide a comprehensive inventory of everything. The closely related discussion between
monism Monism attributes oneness or singleness () to a concept, such as to existence. Various kinds of monism can be distinguished: * Priority monism states that all existing things go back to a source that is distinct from them; e.g., in Neoplatonis ...
and
dualism Dualism most commonly refers to: * Mind–body dualism, a philosophical view which holds that mental phenomena are, at least in certain respects, not physical phenomena, or that the mind and the body are distinct and separable from one another * P ...
is about the most fundamental types that make up reality. According to monism, there is only one kind of thing or substance on the most basic level.
Materialism Materialism is a form of monism, philosophical monism according to which matter is the fundamental Substance theory, substance in nature, and all things, including mind, mental states and consciousness, are results of material interactions. Acco ...
is an influential monist view; it says that everything is material. This means that mental phenomena, such as beliefs, emotions, and consciousness, either do not exist or exist as aspects of matter, like brain states.
Idealists Idealism in philosophy, also known as philosophical realism or metaphysical idealism, is the set of metaphysical perspectives asserting that, most fundamentally, reality is equivalent to mind, spirit, or consciousness; that reality is enti ...
take the converse perspective, arguing that everything is mental. They may understand physical phenomena, like rocks, trees, and planets, as ideas or perceptions of conscious minds.
Neutral monism Neutral monism is an umbrella term for a class of metaphysical theories in the philosophy of mind, concerning the relation of mind to matter. These theories take the fundamental nature of reality to be neither mental nor physical; in other words i ...
occupies a middle ground by saying that both mind and matter are derivative phenomena. Dualists state that mind and matter exist as independent principles, either as distinct substances or different types of properties. In a slightly different sense, monism contrasts with
pluralism Pluralism in general denotes a diversity of views or stands, rather than a single approach or method. Pluralism or pluralist may refer more specifically to: Politics and law * Pluralism (political philosophy), the acknowledgement of a diversi ...
as a view not about the number of basic types but the number of entities. In this sense, monism is the controversial position that only a single all-encompassing entity exists in all of reality. Pluralism is more commonly accepted and says that several distinct entities exist.


By fundamental categories

The historically influential substance-attribute ontology is a polycategorical theory. It says that reality is at its most fundamental level made up of unanalyzable substances that are characterized by universals, such as the properties an individual substance has or relations that exist between substances. The closely related to substratum theory says that each concrete object is made up of properties and a substratum. The difference is that the substratum is not characterized by properties: it is a featureless or ''bare particular'' that merely supports the properties. Various alternative ontological theories have been proposed that deny the role of substances as the foundational building blocks of reality. Stuff ontologies say that the world is not populated by distinct entities but by continuous stuff that fills space. This stuff may take various forms and is often conceived as infinitely divisible. According to
process ontology In philosophy, a process ontology refers to a universal model of the structure of the world as an ordered wholeness. Such ontologies are fundamental ontologies, in contrast to the so-called applied ontologies. Fundamental ontologies do not claim ...
, processes or events are the fundamental entities. This view usually emphasizes that nothing in reality is static, meaning that being is dynamic and characterized by constant change. Bundle theories state that there are no regular objects but only bundles of co-present properties. For example, a lemon may be understood as a bundle that includes the properties yellow, sour, and round. According to traditional bundle theory, the bundled properties are universals, meaning that the same property may belong to several different bundles. According to
trope Trope or tropes may refer to: Arts and entertainment * Trope (cinema), a cinematic convention for conveying a concept * Trope (literature), a figure of speech or common literary device * Trope (music), any of a variety of different things in medi ...
bundle theory, properties are particular entities that belong to a single bundle. Some ontologies focus not on distinct objects but on interrelatedness. According to relationalism, all of reality is relational at its most fundamental level.
Ontic structural realism In the philosophy of science, structuralism (also known as scientific structuralism or as the structuralistic theory-concept) asserts that all aspects of reality are best understood in terms of empirical scientific constructs of entities and thei ...
agrees with this basic idea and focuses on how these relations form complex structures. Some structural realists state that there is nothing but relations, meaning that individual objects do not exist. Others say that individual objects exist but depend on the structures in which they participate. Fact ontologies present a different approach by focusing on how entities belonging to different categories come together to constitute the world. Facts, also known as states of affairs, are complex entities; for example, the fact that ''the Earth is a planet'' consists of the particular object ''the Earth'' and the property ''being a planet''. Fact ontologies state that facts are the fundamental constituents of reality, meaning that objects, properties, and relations cannot exist on their own and only form part of reality to the extent that they participate in facts. In the
history of philosophy The history of philosophy is the systematic study of the development of philosophical thought. It focuses on philosophy as rational inquiry based on argumentation, but some theorists also include myth, religious traditions, and proverbial lor ...
, various ontological theories based on several fundamental categories have been proposed. One of the first theories of categories was suggested by
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
, whose system includes ten categories: substance,
quantity Quantity or amount is a property that can exist as a multitude or magnitude, which illustrate discontinuity and continuity. Quantities can be compared in terms of "more", "less", or "equal", or by assigning a numerical value multiple of a u ...
,
quality Quality may refer to: Concepts *Quality (business), the ''non-inferiority'' or ''superiority'' of something *Quality (philosophy), an attribute or a property *Quality (physics), in response theory *Energy quality, used in various science discipli ...
, relation, place, date, posture, state, action, and passion. An early influential system of categories in Indian philosophy, first proposed in the
Vaisheshika Vaisheshika (IAST: Vaiśeṣika; ; ) is one of the six schools of Hindu philosophy from ancient India. In its early stages, Vaiśeṣika was an independent philosophy with its own metaphysics, epistemology, logic, ethics, and soteriology. Over t ...
school, distinguishes between six categories:
substance Substance may refer to: * Matter, anything that has mass and takes up space Chemistry * Chemical substance, a material with a definite chemical composition * Drug, a chemical agent affecting an organism Arts, entertainment, and media Music * ' ...
, quality, motion, universal, individuator, and inherence.
Immanuel Kant Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German Philosophy, philosopher and one of the central Age of Enlightenment, Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works ...
's
transcendental idealism Transcendental idealism is a philosophical system founded by German philosopher Immanuel Kant in the 18th century. Kant's epistemological program is found throughout his '' Critique of Pure Reason'' (1781). By ''transcendental'' (a term that des ...
includes a system of twelve categories, which Kant saw as pure concepts of understanding. They are subdivided into four classes: quantity, quality, relation, and modality. In more recent philosophy, theories of categories were developed by C. S. Peirce,
Edmund Husserl Edmund Gustav Albrecht Husserl (; 8 April 1859 – 27 April 1938) was an Austrian-German philosopher and mathematician who established the school of Phenomenology (philosophy), phenomenology. In his early work, he elaborated critiques of histori ...
,
Samuel Alexander Samuel Alexander (6 January 1859 – 13 September 1938) was an Australian-born British philosopher. He was the first Jewish fellow of an Oxbridge college. He is now best known as an advocate of emergentism in biology. Early life He was b ...
,
Roderick Chisholm Roderick Milton Chisholm ( ; November 27, 1916 – January 19, 1999) was an American philosopher known for his work on epistemology, metaphysics, free will, value theory, deontology, deontic logic and the philosophy of perception. Richard and ...
, and E. J. Lowe.


Others

The dispute between constituent and relational ontologies concerns the internal structure of concrete particular objects. Constituent ontologies say that objects have an internal structure with properties as their component parts. Bundle theories are an example of this position: they state that objects are bundles of properties. This view is rejected by relational ontologies, which say that objects have no internal structure, meaning that properties do not inhere in them but are externally related to them. According to one analogy, objects are like pin-cushions and properties are pins that can be stuck to objects and removed again without becoming a real part of objects. Relational ontologies are common in certain forms of nominalism that reject the existence of universal properties. Hierarchical ontologies state that the world is organized into levels. Entities on all levels are real but low-level entities are more fundamental than high-level entities. This means that they can exist without high-level entities while high-level entities cannot exist without low-level entities. One hierarchical ontology says that elementary particles are more fundamental than the macroscopic objects they compose, like chairs and tables. Other hierarchical theories assert that substances are more fundamental than their properties and that nature is more fundamental than culture. Flat ontologies, by contrast, deny that any entity has a privileged status, meaning that all entities exist on the same level. For them, the main question is only whether something exists rather than identifying the level at which it exists. The ontological theories of
endurantism Endurantism or endurance theory is a philosophical theory of persistence and identity. According to the endurantist view, material objects are persisting three-dimensional individuals wholly present at every moment of their existence, which goes ...
and
perdurantism Perdurantism or perdurance theory is a philosophical theory of persistence and identity.Temporal parts
aim to explain how material objects persist through time. Endurantism is the view that material objects are three-dimensional entities that travel through time while being fully present in each moment. They remain the same even when they gain or lose properties as they change. Perdurantism is the view that material objects are four-dimensional entities that extend not just through space but also through time. This means that they are composed of temporal parts and, at any moment, only one part of them is present but not the others. According to perdurantists, change means that an earlier part exhibits different qualities than a later part. When a tree loses its leaves, for instance, there is an earlier temporal part with leaves and a later temporal part without leaves. Differential ontology is a
poststructuralist Post-structuralism is a philosophical movement that questions the objectivity or stability of the various interpretive structures that are posited by structuralism and considers them to be constituted by broader systems of Power (social and poli ...
approach interested in the relation between the concepts of identity and
difference Difference commonly refers to: * Difference (philosophy), the set of properties by which items are distinguished * Difference (mathematics), the result of a subtraction Difference, The Difference, Differences or Differently may also refer to: Mu ...
. It says that traditional ontology sees identity as the more basic term by first characterizing things in terms of their essential features and then elaborating differences based on this conception. Differential ontologists, by contrast, privilege difference and say that the identity of a thing is a secondary determination that depends on how this thing differs from other things.
Object-oriented ontology In metaphysics, object-oriented ontology (OOO) is a 21st-century Heidegger-influenced school of thought that rejects the privileging of human existence over the existence of nonhuman objects. This is in contrast to post-Kantian philosophy's tenden ...
belongs to the school of speculative realism and examines the nature and role of objects. It sees objects as the fundamental building blocks of reality. As a flat ontology, it denies that some entities have a more fundamental form of existence than others. It uses this idea to argue that objects exist independently of human thought and perception.


Methods

Methods of ontology are ways of conducting ontological inquiry and deciding between competing theories. There is no single standard method; the diverse approaches are studied by metaontology.
Conceptual analysis Philosophical analysis is any of various techniques, typically used by philosophers in the analytic tradition, in order to "break down" (i.e. analyze) philosophical issues. Arguably the most prominent of these techniques is the analysis of conce ...
is a method to understand ontological concepts and clarify their meaning. It proceeds by analyzing their component parts and the
necessary and sufficient conditions In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...
under which a concept applies to an entity. This information can help ontologists decide whether a certain type of entity, such as numbers, exists.
Eidetic variation Bend Studio (formerly Blank, Berlyn & Co., Inc. and Eidetic, Inc.) is an American video game developer based in Bend, Oregon. Founded in 1992, the studio is best known for developing ''Bubsy 3D'', the ''Syphon Filter'' series, and ''Days Gone'' ...
is a related method in phenomenological ontology that aims to identify the essential features of different types of objects. Phenomenologists start by imagining an example of the investigated type. They proceed by varying the imagined features to determine which ones cannot be changed, meaning they are essential. The transcendental method begins with a simple observation that a certain entity exists. In the following step, it studies the ontological repercussions of this observation by examining how it is possible or which conditions are required for this entity to exist. Another approach is based on
intuition Intuition is the ability to acquire knowledge without recourse to conscious reasoning or needing an explanation. Different fields use the word "intuition" in very different ways, including but not limited to: direct access to unconscious knowledg ...
s in the form of non-inferential impressions about the correctness of general principles. These principles can be used as the foundation on which an ontological system is built and expanded using
deductive reasoning Deductive reasoning is the process of drawing valid inferences. An inference is valid if its conclusion follows logically from its premises, meaning that it is impossible for the premises to be true and the conclusion to be false. For example, t ...
. A further intuition-based method relies on
thought experiment A thought experiment is an imaginary scenario that is meant to elucidate or test an argument or theory. It is often an experiment that would be hard, impossible, or unethical to actually perform. It can also be an abstract hypothetical that is ...
s to evoke new intuitions. This happens by imagining a situation relevant to an ontological issue and then employing
counterfactual thinking Counterfactual thinking is a concept in psychology that involves the human tendency to create possible alternatives to life events that have already occurred; something that is contrary to what actually happened. Counterfactual thinking is, as it ...
to assess the consequences of this situation. For example, some ontologists examine the relation between mind and matter by imagining creatures identical to humans but without consciousness. Naturalistic methods rely on the insights of the natural sciences to determine what exists. According to an influential approach by
Willard Van Orman Quine Willard Van Orman Quine ( ; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth century" ...
, ontology can be conducted by analyzing the ontological commitments of scientific theories. This method is based on the idea that scientific theories provide the most reliable description of reality and that their power can be harnessed by investigating the ontological assumptions underlying them. Principles of theory choice offer guidelines for assessing the advantages and disadvantages of ontological theories rather than guiding their construction. The principle of Ockham's Razor says that simple theories are preferable. A theory can be simple in different respects, for example, by using very few basic types or by describing the world with a small number of fundamental entities. Ontologists are also interested in the explanatory power of theories and give preference to theories that can explain many observations. A further factor is how close a theory is to
common sense Common sense () is "knowledge, judgement, and taste which is more or less universal and which is held more or less without reflection or argument". As such, it is often considered to represent the basic level of sound practical judgement or know ...
. Some ontologists use this principle as an argument against theories that are very different from how ordinary people think about the issue. In applied ontology, ontological engineering is the process of creating and refining conceptual models of specific domains. Developing a new ontology from scratch involves various preparatory steps, such as delineating the scope of the domain one intends to model and specifying the purpose and use cases of the ontology. Once the foundational concepts within the area have been identified, ontology engineers proceed by defining them and characterizing the relations between them. This is usually done in a
formal language In logic, mathematics, computer science, and linguistics, a formal language is a set of strings whose symbols are taken from a set called "alphabet". The alphabet of a formal language consists of symbols that concatenate into strings (also c ...
to ensure precision and, in some cases, automatic
computability Computability is the ability to solve a problem by an effective procedure. It is a key topic of the field of computability theory within mathematical logic and the theory of computation within computer science. The computability of a problem is c ...
. In the following review phase, the validity of the ontology is assessed using test data. Various more specific instructions for how to carry out the different steps have been suggested. They include the
Cyc Cyc (pronounced ) is a long-term artificial intelligence (AI) project that aims to assemble a comprehensive ontology and knowledge base that spans the basic concepts and rules about how the world works. Hoping to capture common sense knowledge ...
method, Grüninger and Fox's methodology, and so-called METHONTOLOGY. In some cases, it is feasible to adapt a pre-existing ontology to fit a specific domain and purpose rather than creating a new one from scratch.


Related fields

Ontology overlaps with many disciplines, including
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
, the study of correct reasoning. Ontologists often employ logical systems to express their insights, specifically in the field of formal ontology. Of particular interest to them is the
existential quantifier Existentialism is a family of philosophy, philosophical views and inquiry that explore the human individual's struggle to lead an Authenticity (philosophy), authentic life despite the apparent Absurdity#The Absurd, absurdity or incomprehensibili ...
(\exists), which is used to express what exists. In
first-order logic First-order logic, also called predicate logic, predicate calculus, or quantificational logic, is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science. First-order logic uses quantified variables over ...
, for example, the formula \exists x \text(x) states that dogs exist. Some philosophers study ontology by examining the structure of thought and language, saying that they reflect the structure of being. Doubts about the accuracy of
natural language A natural language or ordinary language is a language that occurs naturally in a human community by a process of use, repetition, and change. It can take different forms, typically either a spoken language or a sign language. Natural languages ...
have led some ontologists to seek a new
formal language In logic, mathematics, computer science, and linguistics, a formal language is a set of strings whose symbols are taken from a set called "alphabet". The alphabet of a formal language consists of symbols that concatenate into strings (also c ...
, termed ''ontologese'', for a better representation of the fundamental structure of reality. Ontologies are often used in information science to provide a conceptual scheme or inventory of a specific domain, making it possible to classify objects and formally represent information about them. This is of specific interest to computer science, which builds
database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...
s to store this information and defines computational processes to automatically transform and use it. For instance, to encode and store information about clients and employees in a database, an organization may use an ontology with categories such as person, company, address, and name. In some cases, it is necessary to exchange information belonging to different domains or to integrate databases using distinct ontologies. This can be achieved with the help of upper ontologies, which are not limited to one specific domain. They use general categories that apply to most or all domains, like
Suggested Upper Merged Ontology The Suggested Upper Merged Ontology (SUMO) is an upper ontology intended as a foundation ontology for a variety of computer information processing systems. SUMO defines a hierarchy of ''classes'' and related rules and relationships. These are exp ...
and
Basic Formal Ontology Basic Formal Ontology (BFO) is a Upper ontology, top-level ontology developed by Barry Smith (academic), Barry Smith and his associates for the purposes of promoting interoperability among domain ontologies built in its terms through a process of ...
. Similar applications of ontology are found in various fields seeking to manage extensive information within a structured framework.
Protein Ontology The Protein Information Resource (PIR), located at Georgetown University Medical Center, is an integrated public bioinformatics resource to support genomic and proteomic research, and scientific studies. It contains protein sequences databases His ...
is a formal framework for the standardized representation of
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
-related entities and their relationships.
Gene Ontology The Gene Ontology (GO) is a major bioinformatics initiative to unify the representation of gene and gene product attributes across all species. More specifically, the project aims to: 1) maintain and develop its controlled vocabulary of gene and ...
and
Sequence Ontology The Sequence Ontology (SO) is an ontology Ontology is the philosophical study of existence, being. It is traditionally understood as the subdiscipline of metaphysics focused on the most general features of reality. As one of the most fundamen ...
serve a similar purpose in the field of
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinians, Augustinian ...
. Environment Ontology is a knowledge representation focused on
ecosystems An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
and environmental processes.
Friend of a Friend In sociology, a friend of a friend is a human contact that exists because of a mutual friend. Person C is a friend of a friend of person A when there is a person B that is a friend of both A and C. Thus the human relation "friend of a friend" is ...
provides a conceptual framework to represent relations between people and their interests and activities. The topic of ontology has received increased attention in
anthropology Anthropology is the scientific study of humanity, concerned with human behavior, human biology, cultures, society, societies, and linguistics, in both the present and past, including archaic humans. Social anthropology studies patterns of behav ...
since the 1990s, sometimes termed the " ontological turn". This type of inquiry is focused on how people from different cultures experience and understand the nature of being. Specific interest has been given to the ontological outlook of
Indigenous people There is no generally accepted definition of Indigenous peoples, although in the 21st century the focus has been on self-identification, cultural difference from other groups in a state, a special relationship with their traditional territ ...
and how it differs from a Western perspective. As an example of this contrast, it has been argued that various indigenous communities ascribe
intentionality Intentionality is the mental ability to refer to or represent something. Sometimes regarded as the ''mark of the mental'', it is found in mental states like perceptions, beliefs or desires. For example, the perception of a tree has intentionality ...
to non-human entities, like plants, forests, or rivers. This outlook is known as
animism Animism (from meaning 'breath, spirit, life') is the belief that objects, places, and creatures all possess a distinct spiritual essence. Animism perceives all things—animals, plants, rocks, rivers, weather systems, human handiwork, and in ...
and is also found in Native American ontologies, which emphasize the interconnectedness of all living entities and the importance of balance and harmony with nature. Ontology is closely related to
theology Theology is the study of religious belief from a Religion, religious perspective, with a focus on the nature of divinity. It is taught as an Discipline (academia), academic discipline, typically in universities and seminaries. It occupies itse ...
and its interest in the
existence of God The existence of God is a subject of debate in the philosophy of religion and theology. A wide variety of arguments for and against the existence of God (with the same or similar arguments also generally being used when talking about the exis ...
as an ultimate entity. The
ontological argument In the philosophy of religion, an ontological argument is a deductive philosophical argument, made from an ontological basis, that is advanced in support of the existence of God. Such arguments tend to refer to the state of being or existing. ...
, first proposed by
Anselm of Canterbury Anselm of Canterbury OSB (; 1033/4–1109), also known as (, ) after his birthplace and () after his monastery, was an Italian Benedictine monk, abbot, philosopher, and theologian of the Catholic Church, who served as Archbishop of Canterb ...
, attempts to prove the existence of the divine. It defines
God In monotheistic belief systems, God is usually viewed as the supreme being, creator, and principal object of faith. In polytheistic belief systems, a god is "a spirit or being believed to have created, or for controlling some part of the un ...
as the greatest conceivable being. From this definition it concludes that God must exist since God would not be the greatest conceivable being if God lacked existence. Another overlap in the two disciplines is found in ontological theories that use God or an ultimate being as the foundational principle of reality. Heidegger criticized this approach, terming it ''
ontotheology Ontotheology () is the ontology of God and/or the theology of being. While the term was first used by Immanuel Kant, it has only come into broader philosophical parlance with the significance it took for Martin Heidegger's Late Heidegger, later thou ...
''.


History

The roots of ontology in
ancient philosophy This page lists some links to ancient philosophy, namely philosophical thought extending as far as early post-classical history (). Overview Genuine philosophical thought, depending upon original individual insights, arose in many cultures ro ...
are speculations about the nature of being and the source of the universe. Discussions of the essence of reality are found in the
Upanishads The Upanishads (; , , ) are late Vedic and post-Vedic Sanskrit texts that "document the transition from the archaic ritualism of the Veda into new religious ideas and institutions" and the emergence of the central religious concepts of Hind ...
, ancient Indian scriptures dating from as early as 700 BCE. They say that the universe has a divine foundation and discuss in what sense
ultimate reality Ultimate reality is "the supreme, final, and fundamental power in all reality". It refers to the most fundamental fact about reality, especially when it is seen as also being the most valuable fact. This may overlap with the concept of the Absolut ...
is one or many.
Samkhya Samkhya or Sankhya (; ) is a dualistic orthodox school of Hindu philosophy. It views reality as composed of two independent principles, '' Puruṣa'' ('consciousness' or spirit) and '' Prakṛti'' (nature or matter, including the human mind a ...
, the first orthodox school of Indian philosophy, formulated an
atheist Atheism, in the broadest sense, is an absence of belief in the existence of deities. Less broadly, atheism is a rejection of the belief that any deities exist. In an even narrower sense, atheism is specifically the position that there no ...
dualist ontology based on the Upanishads, identifying pure consciousness and
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic pa ...
as its two foundational principles. The later
Vaisheshika Vaisheshika (IAST: Vaiśeṣika; ; ) is one of the six schools of Hindu philosophy from ancient India. In its early stages, Vaiśeṣika was an independent philosophy with its own metaphysics, epistemology, logic, ethics, and soteriology. Over t ...
school proposed a comprehensive system of categories. In
ancient China The history of China spans several millennia across a wide geographical area. Each region now considered part of the Chinese world has experienced periods of unity, fracture, prosperity, and strife. Chinese civilization first emerged in the Y ...
,
Laozi Laozi (), also romanized as Lao Tzu #Name, among other ways, was a semi-legendary Chinese philosophy, Chinese philosopher and author of the ''Tao Te Ching'' (''Laozi''), one of the foundational texts of Taoism alongside the ''Zhuangzi (book) ...
's (6th century BCE)
Taoism Taoism or Daoism (, ) is a diverse philosophical and religious tradition indigenous to China, emphasizing harmony with the Tao ( zh, p=dào, w=tao4). With a range of meaning in Chinese philosophy, translations of Tao include 'way', 'road', ' ...
examines the underlying order of the universe, known as
Tao The Tao or Dao is the natural way of the universe, primarily as conceived in East Asian philosophy and religion. This seeing of life cannot be grasped as a concept. Rather, it is seen through actual living experience of one's everyday being. T ...
, and how this order is shaped by the interaction of two basic forces,
yin and yang Originating in Chinese philosophy, yin and yang (, ), also yinyang or yin-yang, is the concept of opposite cosmic principles or forces that interact, interconnect, and perpetuate each other. Yin and yang can be thought of as complementary an ...
. The philosophical movement of
Xuanxue Xuanxue (), sometimes called Neo-Daoism (Neo-Taoism), is a metaphysical Post-classical history, post-classical Chinese philosophy from the Six Dynasties (222-589), bringing together Taoist and Confucianism, Confucian beliefs through revision and di ...
emerged in the 3rd century CE and explored the relation between being and non-being. Starting in the 6th century BCE,
Presocratic philosophers Pre-Socratic philosophy, also known as early Greek philosophy, is ancient Greek philosophy before Socrates. Pre-Socratic philosophers were mostly interested in cosmology, the beginning and the substance of the universe, but the inquiries of the ...
in
ancient Greece Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically r ...
aimed to provide rational explanations of the universe. They suggested that a first principle, such as water or fire, is the primal source of all things.
Parmenides Parmenides of Elea (; ; fl. late sixth or early fifth century BC) was a Pre-Socratic philosophy, pre-Socratic ancient Greece, Greek philosopher from Velia, Elea in Magna Graecia (Southern Italy). Parmenides was born in the Greek colony of Veli ...
(c. 515–450 BCE) is sometimes considered the founder of ontology because of his explicit discussion of the concepts of being and non-being. Inspired by Presocratic philosophy,
Plato Plato ( ; Greek language, Greek: , ; born  BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
(427–347 BCE) developed his
theory of forms The Theory of Forms or Theory of Ideas, also known as Platonic idealism or Platonic realism, is a philosophical theory credited to the Classical Greek philosopher Plato. A major concept in metaphysics, the theory suggests that the physical w ...
. It distinguishes between unchangeable perfect forms and matter, which has a lower degree of existence and imitates the forms.
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
(384–322 BCE) suggested an elaborate system of categories that introduced the concept of substance as the primary kind of being. The school of
Neoplatonism Neoplatonism is a version of Platonic philosophy that emerged in the 3rd century AD against the background of Hellenistic philosophy and religion. The term does not encapsulate a set of ideas as much as a series of thinkers. Among the common id ...
arose in the 3rd century CE and proposed an ineffable source of everything, called ''the One'', which is more basic than being itself. The
problem of universals The problem of universals is an ancient question from metaphysics that has inspired a range of philosophical topics and disputes: "Should the properties an object has in common with other objects, such as color and shape, be considered to exist ...
was an influential topic in medieval ontology.
Boethius Anicius Manlius Severinus Boethius, commonly known simply as Boethius (; Latin: ''Boetius''; 480–524 AD), was a Roman Roman Senate, senator, Roman consul, consul, ''magister officiorum'', polymath, historian, and philosopher of the Early Middl ...
(477–524 CE) suggested that universals can exist not only in matter but also in the mind. This view inspired
Peter Abelard Peter Abelard (12 February 1079 – 21 April 1142) was a medieval French scholastic philosopher, leading logician, theologian, teacher, musician, composer, and poet. This source has a detailed description of his philosophical work. In philos ...
(1079–1142 CE), who proposed that universals exist only in the mind.
Thomas Aquinas Thomas Aquinas ( ; ; – 7 March 1274) was an Italian Dominican Order, Dominican friar and Catholic priest, priest, the foremost Scholasticism, Scholastic thinker, as well as one of the most influential philosophers and theologians in the W ...
(1224–1274 CE) developed and refined fundamental ontological distinctions, such as the contrast between existence and
essence Essence () has various meanings and uses for different thinkers and in different contexts. It is used in philosophy and theology as a designation for the property (philosophy), property or set of properties or attributes that make an entity the ...
, between substance and accidents, and between matter and form. He also discussed the
transcendentals The transcendentals (, from transcendere "to exceed") are "properties of being", nowadays commonly considered to be truth, unity (oneness), beauty, and goodness. The conceptual idea arose from medieval scholasticism, namely Aquinas but originated ...
, which are the most general properties or modes of being.
John Duns Scotus John Duns Scotus ( ; , "Duns the Scot";  – 8 November 1308) was a Scottish Catholic priest and Franciscan friar, university professor, philosopher and theologian. He is considered one of the four most important Christian philosopher-t ...
(1266–1308) argued that all entities, including God, exist in the same way and that each entity has a unique essence, called
haecceity Haecceity (; from the Latin , 'thisness') is a term from medieval scholastic philosophy, first coined by followers of Duns Scotus to denote a concept that he seems to have originated: the irreducible determination of a thing that makes it ''this ...
.
William of Ockham William of Ockham or Occam ( ; ; 9/10 April 1347) was an English Franciscan friar, scholastic philosopher, apologist, and theologian, who was born in Ockham, a small village in Surrey. He is considered to be one of the major figures of medie ...
(c. 1287–1347 CE) proposed that one can decide between competing ontological theories by assessing which one uses the smallest number of elements, a principle known as Ockham's razor. In Arabic-Persian philosophy,
Avicenna Ibn Sina ( – 22 June 1037), commonly known in the West as Avicenna ( ), was a preeminent philosopher and physician of the Muslim world, flourishing during the Islamic Golden Age, serving in the courts of various Iranian peoples, Iranian ...
(980–1037 CE) combined ontology with
theology Theology is the study of religious belief from a Religion, religious perspective, with a focus on the nature of divinity. It is taught as an Discipline (academia), academic discipline, typically in universities and seminaries. It occupies itse ...
. He identified God as a necessary being that is the source of everything else, which only has contingent existence. In 8th-century
Indian philosophy Indian philosophy consists of philosophical traditions of the Indian subcontinent. The philosophies are often called darśana meaning, "to see" or "looking at." Ānvīkṣikī means “critical inquiry” or “investigation." Unlike darśan ...
, the school of Advaita Vedanta emerged. It says that only a single all-encompassing entity exists, stating that the impression of a plurality of distinct entities is an
illusion An illusion is a distortion of the senses, which can reveal how the mind normally organizes and interprets sensory stimulation. Although illusions distort the human perception of reality, they are generally shared by most people. Illusions may ...
. Starting in the 13th century CE, the
Navya-Nyāya The Navya-Nyāya (sanskrit: नव्य-न्याय) or Neo-Logical '' darśana'' (view, system, or school) of Indian logic and Indian philosophy was founded in the 13th century CE by the philosopher Gangeśa Upādhyāya of Mithila and co ...
school built on Vaisheshika ontology with a particular focus on the problem of non-existence and negation. 9th-century China saw the emergence of
Neo-Confucianism Neo-Confucianism (, often shortened to ''lǐxué'' 理學, literally "School of Principle") is a moral, ethical, and metaphysical Chinese philosophy influenced by Confucianism, which originated with Han Yu (768–824) and Li Ao (772–841) i ...
, which developed the idea that a rational principle, known as '' li'', is the ground of being and order of the cosmos.
René Descartes René Descartes ( , ; ; 31 March 1596 – 11 February 1650) was a French philosopher, scientist, and mathematician, widely considered a seminal figure in the emergence of modern philosophy and Modern science, science. Mathematics was paramou ...
(1596–1650) formulated a dualist ontology at the beginning of the modern period. It distinguishes between mind and matter as distinct substances that causally interact. Rejecting Descartes's dualism,
Baruch Spinoza Baruch (de) Spinoza (24 November 163221 February 1677), also known under his Latinized pen name Benedictus de Spinoza, was a philosopher of Portuguese-Jewish origin, who was born in the Dutch Republic. A forerunner of the Age of Enlightenmen ...
(1632–1677) proposed a monist ontology according to which there is only a single entity that is identical to God and nature.
Gottfried Wilhelm Leibniz Gottfried Wilhelm Leibniz (or Leibnitz; – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat who is credited, alongside Sir Isaac Newton, with the creation of calculus in addition to ...
(1646–1716), by contrast, said that the universe is made up of many simple substances, which are synchronized but do not interact with one another.
John Locke John Locke (; 29 August 1632 (Old Style and New Style dates, O.S.) – 28 October 1704 (Old Style and New Style dates, O.S.)) was an English philosopher and physician, widely regarded as one of the most influential of the Enlightenment thi ...
(1632–1704) proposed his substratum theory, which says that each object has a featureless substratum that supports the object's properties. Christian Wolff (1679–1754) was influential in establishing ontology as a distinct discipline, delimiting its scope from other forms of metaphysical inquiry.
George Berkeley George Berkeley ( ; 12 March 168514 January 1753), known as Bishop Berkeley (Bishop of Cloyne of the Anglican Church of Ireland), was an Anglo-Irish philosopher, writer, and clergyman who is regarded as the founder of "immaterialism", a philos ...
(1685–1753) developed an idealist ontology according to which material objects are ideas perceived by minds.
Immanuel Kant Immanuel Kant (born Emanuel Kant; 22 April 1724 – 12 February 1804) was a German Philosophy, philosopher and one of the central Age of Enlightenment, Enlightenment thinkers. Born in Königsberg, Kant's comprehensive and systematic works ...
(1724–1804) rejected the idea that humans can have direct knowledge of independently existing things and their nature, limiting knowledge to the field of appearances. For Kant, ontology does not study external things but provides a system of pure concepts of understanding. Influenced by Kant's philosophy,
Georg Wilhelm Friedrich Hegel Georg Wilhelm Friedrich Hegel (27 August 1770 – 14 November 1831) was a 19th-century German idealist. His influence extends across a wide range of topics from metaphysical issues in epistemology and ontology, to political philosophy and t ...
(1770–1831) linked ontology and
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the study of deductively valid inferences or logical truths. It examines how conclusions follow from premises based on the structure o ...
. He said that being and thought are identical and examined their foundational structures.
Arthur Schopenhauer Arthur Schopenhauer ( ; ; 22 February 1788 – 21 September 1860) was a German philosopher. He is known for his 1818 work ''The World as Will and Representation'' (expanded in 1844), which characterizes the Phenomenon, phenomenal world as ...
(1788–1860) rejected Hegel's philosophy and proposed that the world is an expression of a blind and irrational will. Francis Herbert Bradley (1846–1924) saw absolute spirit as the ultimate and all-encompassing reality while denying that there are any external relations. In Indian philosophy,
Swami Vivekananda Swami Vivekananda () (12 January 1863 – 4 July 1902), born Narendranath Datta, was an Indian Hindus, Hindu monk, philosopher, author, religious teacher, and the chief disciple of the Indian mystic Ramakrishna. Vivekananda was a major figu ...
(1863–1902) expanded on Advaita Vedanta, emphasizing the unity of all existence.
Sri Aurobindo Sri Aurobindo (born Aurobindo Ghose; 15 August 1872 – 5 December 1950) was an Indian Modern yoga gurus, yogi, maharishi, and Indian nationalist. He also edited the newspaper Bande Mataram (publication), ''Bande Mataram''. Aurobindo st ...
(1872–1950) sought to understand the world as an evolutionary manifestation of a divine consciousness. At the beginning of the 20th century,
Edmund Husserl Edmund Gustav Albrecht Husserl (; 8 April 1859 – 27 April 1938) was an Austrian-German philosopher and mathematician who established the school of Phenomenology (philosophy), phenomenology. In his early work, he elaborated critiques of histori ...
(1859–1938) developed
phenomenology Phenomenology may refer to: Art * Phenomenology (architecture), based on the experience of building materials and their sensory properties Philosophy * Phenomenology (Peirce), a branch of philosophy according to Charles Sanders Peirce (1839 ...
and employed its method, the description of
experience Experience refers to Consciousness, conscious events in general, more specifically to perceptions, or to the practical knowledge and familiarity that is produced by these processes. Understood as a conscious event in the widest sense, experience i ...
, to address ontological problems. This idea inspired his student
Martin Heidegger Martin Heidegger (; 26 September 1889 – 26 May 1976) was a German philosopher known for contributions to Phenomenology (philosophy), phenomenology, hermeneutics, and existentialism. His work covers a range of topics including metaphysics, art ...
(1889–1976) to clarify the meaning of being by exploring the mode of human existence.
Jean-Paul Sartre Jean-Paul Charles Aymard Sartre (, ; ; 21 June 1905 – 15 April 1980) was a French philosopher, playwright, novelist, screenwriter, political activist, biographer, and literary criticism, literary critic, considered a leading figure in 20th ...
responded to Heidegger's philosophy by examining the relation between being and
nothingness Nothing, no-thing, or no thing is the complete absence of ''anything'', as the opposite of ''something'' and an antithesis of everything. The concept of nothing has been a matter of philosophical debate since at least the 5th century BCE. Earl ...
from the perspective of human existence, freedom, and consciousness. Based on the phenomenological method,
Nicolai Hartmann Paul Nicolai Hartmann (; 20 February 1882 – 9 October 1950) was a German philosopher. He is regarded as a key representative of critical realism and as one of the most important twentieth-century metaphysicians. Biography Hartmann was born a ...
(1882–1950) developed a complex hierarchical ontology that divides reality into four levels: inanimate, biological, psychological, and spiritual.
Alexius Meinong Alexius Meinong von Handschuchsheim (; 17 July 1853 – 27 November 1920) was an Austrian philosopher, a realist known for his unique ontology and theory of objects. He also made contributions to philosophy of mind and theory of value. Lif ...
(1853–1920) articulated a controversial ontological theory that includes nonexistent objects as part of being. Arguing against this theory,
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell, (18 May 1872 – 2 February 1970) was a British philosopher, logician, mathematician, and public intellectual. He had influence on mathematics, logic, set theory, and various areas of analytic ...
(1872–1970) formulated a fact ontology known as
logical atomism Logical atomism is a philosophical view that originated in the early 20th century with the development of analytic philosophy. It holds that the world consists of ultimate logical "facts" (or "atoms") that cannot be broken down any further, each ...
. This idea was further refined by the early
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. From 1929 to 1947, Witt ...
(1889–1951) and inspired D. M. Armstrong's (1926–2014) ontology.
Alfred North Whitehead Alfred North Whitehead (15 February 1861 – 30 December 1947) was an English mathematician and philosopher. He created the philosophical school known as process philosophy, which has been applied in a wide variety of disciplines, inclu ...
(1861–1947), by contrast, developed a process ontology.
Rudolf Carnap Rudolf Carnap (; ; 18 May 1891 – 14 September 1970) was a German-language philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle and an advocate of logical positivism. ...
(1891–1970) questioned the objectivity of ontological theories by claiming that what exists depends on one's linguistic framework. He had a strong influence on
Willard Van Orman Quine Willard Van Orman Quine ( ; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth century" ...
(1908–2000), who analyzed the ontological commitments of scientific theories to solve ontological problems. Quine's student David Lewis (1941–2001) formulated the position of modal realism, which says that possible worlds are as real and concrete as the actual world. Since the end of the 20th century, interest in applied ontology has risen in computer and information science with the development of conceptual frameworks for specific domains.


See also

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References


Notes


Citations


Sources

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External links

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