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Ontology is the branch of
philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, language. Such questio ...

philosophy
that studies concepts such as
existence Existence is the ability of an entity to interact with physical reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociolog ...

existence
,
being In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, la ...

being
, becoming, and
reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociology), a concept in sociology * The Imaginary (psychoanalysis), a concept by ...

reality
. It includes the questions of how entities are grouped into basic categories and which of these entities exist on the most fundamental level. Ontology is sometimes referred to as the ''science of being'' and belongs to the major branch of philosophy known as
metaphysics Metaphysics is the branch of philosophy that studies the first principles of being, identity and change, space and time, causality, necessity and possibility. It includes questions about the nature of consciousness and the relationship between ...

metaphysics
. Ontologists often try to determine what the ''categories'' or ''highest kinds'' are and how they form a ''system of categories'' that provides an encompassing classification of all entities. Commonly proposed categories include substances,
properties Property (''latin: Res Privata'') in the abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article, it is one or more components (rather than attributes), whether phys ...
,
relations 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 *Public ...
,
states of affairsIn philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, langua ...
and
events 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 event ...
. These categories are characterized by fundamental ontological concepts, like ''particularity'' and ''universality'', ''abstractness'' and ''concreteness'', or ''possibility'' and ''necessity''. Of special interest is the concept of ''ontological dependence'', which determines whether the entities of a category exist on the ''most fundamental level''. Disagreements within ontology are often about whether entities belonging to a certain category exist and, if so, how they are related to other entities. When used as a
countable noun In linguistics Linguistics is the science, scientific study of language. It encompasses the analysis of every aspect of language, as well as the methods for studying and modeling them. The traditional areas of linguistic analysis include ...
, the terms "ontology" and "ontologies" refer not to the ''science of being'' but to theories within the ''science of being''. Ontological theories can be divided into various types according to their theoretical commitments. ''Monocategorical ontologies'' hold that there is only one basic category, which is rejected by ''polycategorical ontologies''. ''Hierarchical ontologies'' assert that some entities exist on a more fundamental level and that other entities depend on them. ''Flat ontologies'', on the other hand, deny such a privileged status to any entity.


Etymology

The
compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive structu ...
word ''ontology'' ('study of being') combines : ''
onto In , a surjective function (also known as surjection, or onto function) is a that maps an element to every element ; that is, for every , there is an such that . In other words, every element of the function's is the of one element of its ...
-'' (
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
: ; ) and : ''
-logia ''-logy'' is a suffix in the English language, used with words originally adapted from Ancient Greek ending in (''-logia''). The earliest English examples were anglicizations of the French ''wiktionary:-logie, -logie'', which was in turn inherit ...
'' (). While the
etymology Etymology ()The New Oxford Dictionary of English ''The'' () is a grammatical article Article often refers to: * Article (grammar) An article is any member of a class of dedicated words that are used with noun phrases to mark the identi ...
is Greek, the oldest extant records of the word itself is a
New Latin New Latin (also called Neo-Latin or modern Latin) is the revival of Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, know ...
form , which appeared : in 1606 in the ''
Ogdoas Scholastica 300px, ''Ogdoas Scholastica,...'' (1606). Jacob Lorhard ( la, Jacobus Lorhardus; 1561 – 19 May 1609) was a German philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφ ...
'' by
Jacob Lorhard 300px, ''Ogdoas Scholastica,...'' (1606). Jacob Lorhard ( la, Jacobus Lorhardus; 1561 – 19 May 1609) was a German philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφ ...
(''Lorhardus''), and : in 1613 in the ''Lexicon philosophicum'' by Rudolf Göckel (''Goclenius''). The first occurrence in English of ''ontology'', as recorded by the ''
Oxford English Dictionary The ''Oxford English Dictionary'' (''OED'') is the principal historical dictionary A historical dictionary or dictionary on historical principles is a dictionary which deals not only with the latterday meanings of words but also the historica ...
'', came in 1664 through ''Archelogia philosophica nova...'' by Gideon Harvey The word was first used, in its Latin form, by philosophers, and based on the Latin roots (and in turn on the Greek ones).


Overview

Ontology is closely associated with Aristotle's question of 'being ''qua'' being': the question of what all entities in the widest sense have in common. The ''Eleatic principle'' is one answer to this question: it states that being is inextricably tied to causation, that "Power is the mark of Being". One problem with this answer is that it excludes abstract objects. Another explicit but little accepted answer can be found in Berkeley's slogan that "to be is to be perceived". Intimately related but not identical to the question of 'being ''qua'' being' is the problem of
categories Category, plural categories, may refer to: Philosophy and general uses *Categorization Categorization is the human ability and activity of recognizing shared features or similarities between the elements of the experience of the world (such ...
. Categories are usually seen as the highest kinds or genera. A system of categories provides a classification of entities that is exclusive and exhaustive: every entity belongs to exactly one category. Various such classifications have been proposed, they often include categories for substances,
properties Property (''latin: Res Privata'') in the abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article, it is one or more components (rather than attributes), whether phys ...
,
relations 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 *Public ...
,
states of affairsIn philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, langua ...
or
events 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 event ...
. At the core of the differentiation between categories are various fundamental ontological concepts and distinctions, for example, the concepts of ''particularity and universality'', of ''abstractness and concreteness'', of ''ontological dependence'', of ''identity'' and of ''modality''. These concepts are sometimes treated as categories themselves, are used to explain the difference between categories or play other central roles for characterizing different ontological theories. Within ontology, there is a lack of general consensus concerning how the different categories are to be defined. Different ontologists often disagree on whether a certain category has any members at all or whether a given category is fundamental.


Particulars and universals

Particular In metaphysics Metaphysics is the branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of ...

Particular
s or individuals are usually contrasted with
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 example ...
. Universals concern features that can be exemplified by various different particulars. For example, a tomato and a strawberry are two particulars that exemplify the universal redness. Universals can be present at various distinct locations in space at the same time while particulars are restricted to one location at a time. Furthermore, universals can be fully present at different times, which is why they are sometimes referred to as ''repeatables'' in contrast to non-repeatable particulars. The so-called
problem of universals The problem of universals is an ancient question from metaphysics Metaphysics is the branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epi ...
is the problem to explain how different things can agree in their features, e.g. how a tomato and a strawberry can both be red. Realists about universals believe that there are universals. They can solve the ''problem of universals'' by explaining the commonality through a universal shared by both entities. Realists are divided among themselves as to whether universals can exist independently of being exemplified by something ("ante res") or not ("in rebus"). Nominalists, on the other hand, deny that there are universals. They have to resort to other notions to explain how a feature can be common to several entities, for example, by positing either fundamental resemblance-relations between the entities (resemblance nominalism) or a shared membership to a common natural class (class nominalism).


Abstract and concrete

Many philosophers agree that there is an exclusive and exhaustive distinction between ''concrete objects'' and ''abstract objects''. Some philosophers consider this to be the most general division of being. Examples of concrete objects include plants, human beings and planets while things like numbers, sets and propositions are abstract objects. But despite the general agreement concerning the paradigm cases, there is less consensus as to what the characteristic marks of concreteness and abstractness are. Popular suggestions include defining the distinction in terms of the difference between (1) existence inside or outside space-time, (2) having causes and effects or not and (3) having contingent or necessary existence.


Ontological dependence

An entity ''ontologically depends'' on another entity if the first entity cannot exist without the second entity. Ontologically independent entities, on the other hand, can exist all by themselves. For example, the surface of an apple cannot exist without the apple and so depends on it ontologically. Entities often characterized as ontologically dependent include properties, which depend on their bearers, and boundaries, which depend on the entity they demarcate from its surroundings. As these examples suggest, ontological dependence is to be distinguished from causal dependence, in which an effect depends for its existence on a cause. It is often important to draw a distinction between two types of ontological dependence: rigid and generic. Rigid dependence concerns the dependence on one specific entity, as the surface of an apple depends on its specific apple. Generic dependence, on the other hand, involves a weaker form of dependence, on merely a certain type of entity. For example, electricity generically depends on there being charged particles, but it does not depend on any specific charged particle. Dependence-relations are relevant to ontology since it is often held that ontologically dependent entities have a less robust form of being. This way a ''hierarchy'' is introduced into the world that brings with it the distinction between more and less fundamental entities.


Identity

Identity Identity may refer to: Social sciences * Identity (social science), personhood or group affiliation in psychology and sociology Group expression and affiliation * Cultural identity, a person's self-affiliation (or categorization by others ...
is a basic ontological concept that is often expressed by the word "same". It is important to distinguish between ''qualitative identity'' and ''numerical identity''. For example, consider two children with identical bicycles engaged in a race while their mother is watching. The two children have the ''same'' bicycle in one sense (''qualitative identity'') and the ''same'' mother in another sense (''numerical identity''). Two qualitatively identical things are often said to be indiscernible. The two senses of ''sameness'' are linked by two principles: the principle of ''indiscernibility of identicals'' and the principle of ''
identity of indiscernibles The identity of indiscernibles is an ontology, ontological principle that states that there cannot be separate object (philosophy), objects or wikt:entity, entities that have all their property (philosophy), properties in common. That is, entities ' ...
''. The principle of ''indiscernibility of identicals'' is uncontroversial and states that if two entities are numerically identical with each other then they exactly resemble each other. The principle of ''identity of indiscernibles'', on the other hand, is more controversial in making the converse claim that if two entities exactly resemble each other then they must be numerically identical. This entails that "no two distinct things exactly resemble each other". A well-known counterexample comes from
Max Black Max Black (24 February 1909 – 27 August 1988) was a British-American philosopher, who was a leading figure in analytic philosophy Analytic philosophy is a branch and tradition of philosophy Philosophy (from , ) is the study of gener ...
, who describes a symmetrical universe consisting of only two spheres with the same features. Black argues that the two spheres are indiscernible but not identical, thereby constituting a violation of the principle of ''identity of indiscernibles''. The problem of ''identity over time'' concerns the question of ''persistence'': whether or in what sense two objects at different times can be ''numerically identical''. This is usually referred to as ''diachronic identity'' in contrast to ''synchronic identity''. The statement that " e table in the next room is identical with the one you purchased last year" asserts diachronic identity between the table now and the table then. A famous example of a denial of diachronic identity comes from
Heraclitus Heraclitus of Ephesus (; grc-gre, Ἡράκλειτος ; , ) was an Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), ...

Heraclitus
, who argues that it is impossible to step into the same river twice because of the changes that occurred in-between. The traditional position on the problem of ''persistence'' is
endurantism Endurantism or endurance theory is a philosophical theory of persistence and Identity (philosophy), identity. According to the endurantist view, material objects are persisting three-dimensional individuals wholly present at every moment of their ...
, the thesis that diachronic identity in a strict sense is possible. One problem with this position is that it seems to violate the principle of ''indiscernibility of identicals'': the object may have undergone changes in the meantime resulting in it being discernible from itself.
PerdurantismPerdurantism or perdurance theory is a philosophical theory of persistence and identity.Temporal parts< ...
or
four-dimensionalism In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, lan ...
is an alternative approach holding that ''diachronic identity'' is possible only in a loose sense: while the two objects differ from each other strictly speaking, they are both temporal parts that belong to the same temporally extended whole. ''Perdurantism'' avoids many philosophical problems plaguing ''endurantism'', but ''endurantism'' seems to be more in touch with how we ordinarily conceive ''diachronic identity''.


Modality

Modality Modality may refer to: Humanities * Modality (theology), the organization and structure of the church, as distinct from sodality or parachurch organizations * Modality (music), in music, the subject concerning certain diatonic scales * Modalities ...
concerns the concepts of possibility, actuality and necessity. In contemporary discourse, these concepts are often defined in terms of
possible worlds A possible world is a complete and consistent way the world is or could have been. They are widely used as a formal device in logic Logic is an interdisciplinary field which studies truth and reasoning. Informal logic seeks to characterize ...
. A possible world is a complete way how things could have been. The actual world is one possible world among others: things could have been different than they actually are. A proposition is possibly true if there is at least one possible world in which it is true; it is necessarily true if it is true in all possible worlds. '' Actualists'' and ''possibilists'' disagree on the ''ontological status'' of possible worlds. Actualists hold that reality is at its core actual and that possible worlds should be understood in terms of actual entities, for example, as fictions or as sets of sentences. Possibilists, on the other hand, assign to possible worlds the same ''fundamental ontological status'' as to the actual world. This is a form of
modal realism Modal realism is the view propounded by David Kellogg 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 is based on the following tenets: possible worlds exist; pos ...
, holding that reality has ''irreducibly modal features''. Another important issue in this field concerns the distinction between ''contingent'' and ''necessary beings''. Contingent beings are beings whose existence is possible but not necessary. Necessary beings, on the other hand, could not have failed to exist. It has been suggested that this distinction is the highest division of being.


Substances

The category of ''substances'' has played a central role in many ontological theories throughout the history of philosophy. "Substance" is a technical term within philosophy not to be confused with the more common usage in the sense of chemical substances like gold or sulfur. Various definitions have been given but among the most common features ascribed to substances in the philosophical sense is that they are ''particulars'' that are ''ontologically independent'': they are able to exist all by themselves. Being ontologically independent, substances can play the role of ''fundamental entities'' in the ''ontological hierarchy''. If 'ontological independence' is defined as including ''causal independence'' then only self-caused entities, like Spinoza's God, can be substances. With a specifically ontological definition of 'independence', many everyday objects like books or cats may qualify as substances. Another defining feature often attributed to substances is their ability to ''undergo changes''. Changes involve something existing ''before'', ''during'' and ''after'' the change. They can be described in terms of a persisting substance gaining or losing properties, or of ''matter'' changing its ''form''. From this perspective, the ripening of a tomato may be described as a change in which the tomato loses its greenness and gains its redness. It is sometimes held that a substance can have a property in two ways: '' essentially'' and ''accidentally''. A substance can survive a change of ''accidental properties'' but it cannot lose its ''essential properties'', which constitute its nature.


Properties and relations

The category of ''properties'' consists of entities that can be exemplified by other entities, e.g. by substances. Properties characterize their bearers, they express what their bearer is like. For example, the red color and the round shape of an apple are properties of this apple. Various ways have been suggested concerning how to conceive properties themselves and their relation to substances. The traditionally dominant view is that properties are universals that inhere in their bearers. As universals, they can be shared by different substances. Nominalists, on the other hand, deny that universals exist. Some nominalists try to account for properties in terms of resemblance relations or class membership. Another alternative for nominalists is to conceptualize properties as simple particulars, so-called
tropes Trope or tropes may refer to: Arts, entertainment, and media * Trope (cinema) In cinema Cinema may refer to: Film * Cinematography Cinematography (from ancient Greek Ancient Greek includes the forms of the Greek language used in ...
. This position entails that both the apple and its redness are particulars. Different apples may still exactly resemble each other concerning their color, but they do not share the same particular property on this view: the two color-tropes are ''numerically distinct''. Another important question for any theory of properties is how to conceive the relation between a bearer and its properties. Substratum theorists hold that there is some kind of substance, ''substratum'' or '' bare particular'' that acts as bearer.
Bundle theory Bundle theory, originated by the 18th century Scottish philosopher David Hume David Hume (; born David Home; 7 May 1711 NS (26 April 1711 OS) – 25 August 1776) Cranston, Maurice, and Thomas Edmund Jessop. 2020 999999 or triple nine most ...
is an alternative view that does away with a substratum altogether: objects are taken to be just a bundle of properties. They are held together not by a substratum but by the so-called ''compresence-relation'' responsible for the bundling. Both substratum theory and bundle theory can be combined with conceptualizing properties as universals or as particulars. An important distinction among properties is between ''categorical'' and ''dispositional'' properties. Categorical properties concern what something is like, e.g. what qualities it has. Dispositional properties, on the other hand, involve what powers something has, what it is able to do, even if it is not actually doing it. For example, the shape of a sugar cube is a categorical property while its tendency to dissolve in water is a dispositional property. For many properties there is a lack of consensus as to how they should be classified, for example, whether colors are categorical or dispositional properties. Categoricalism is the thesis that on a fundamental level there are only categorical properties, that dispositional properties are either non-existent or dependent on categorical properties. Dispositionalism is the opposite theory, giving ontological primacy to dispositional properties. Between these two extremes, there are dualists who allow both categorical and dispositional properties in their ontology. ''Relations'' are ways in which things, the relata, stand to each other. Relations are in many ways similar to properties in that both characterize the things they apply to. Properties are sometimes treated as a special case of relations involving only one relatum. Central for ontology is the distinction between ''internal'' and ''external'' relations. A relation is ''internal'' if it is fully determined by the features of its relata. For example, an apple and a tomato stand in the ''internal relation'' of similarity to each other because they are both red. Some philosophers have inferred from this that internal relations do not have a proper ontological status since they can be reduced to intrinsic properties. ''External'' relations, on the other hand, are not fixed by the features of their relata. For example, a book stands in an ''external'' relation to a table by lying on top of it. But this is not determined by the book's or the table's features like their color, their shape, etc.


States of affairs and events

States of affairsIn philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, langua ...
are complex entities, in contrast to substances and properties, which are usually conceived as simple. Complex entities are built up from or constituted by other entities. Atomic states of affairs are constituted by one particular and one property exemplified by this particular. For example, the state of affairs that Socrates is wise is constituted by the particular "Socrates" and the property "wise". Relational states of affairs involve several particulars and a relation connecting them. States of affairs that ''obtain'' are also referred to as
facts A fact is something that is truth, true. The usual test for a statement of fact is verifiability—that is whether it can be demonstrated to correspond to experience. Standard reference works are often used to check facts. Science, Scientific ...
. It is controversial which ontological status should be ascribed to states of affairs that do not obtain. States of affairs have been prominent in 20th-century ontology as various theories were proposed to describe the world as composed of states of affairs. It is often held that states of affairs play the role of
truthmaker Truthmaker theory is "the branch of metaphysics that explores the relationships between what is Truth, true and what Existence, exists". The basic intuition behind truthmaker theory is that truth depends on being. For example, a perceptual experienc ...
s: judgments or assertions are true because the corresponding state of affairs obtains.
Events 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 event ...
take place in time, they are sometimes thought of as involving a change in the form of acquiring or losing a property, like the lawn's becoming dry. But on a liberal view, the retaining of a property without any change may also count as an event, e.g. the lawn's staying wet. Some philosophers see events as universals that can repeat at different times, but the more dominant view is that events are particulars and therefore non-repeatable. Some events are complex in that they are composed of a sequence of events, often referred to as a process. But even simple events can be conceived as complex entities involving an object, a time and the property exemplified by the object at this time. So-called
process philosophy Process philosophy, also ontology of becoming, or processism, defines processes in the ordinary everyday real world as its only basic or elementary existents. It treats other real existents (examples: enduring physical objects, thoughts) as abstra ...
or
process ontology In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, lang ...
ascribes ontological primacy to changes and processes as opposed to the emphasis on static being in the traditionally dominant substance metaphysics.


Reality of things

The word 'real' is derived from the Latin word ''res'', which is often translated as 'thing'. The word 'thing' is often used in ontological discourse as if it had a presupposed meaning, not needing an explicit philosophical definition because it belongs to ordinary language. Nevertheless, what is a thing and what is real or substantial are concerns of ontology. Different views are held about this. Plato proposed that underlying, and constituting the real basis of, the concretely experienced world are '
forms Form is the shape, visual appearance, or :wikt:configuration, configuration of an object. In a wider sense, the form is the way something happens. Form also refers to: *Form (document), a document (printed or electronic) with spaces in which to w ...
' or 'ideas', which today are generally regarded as high abstractions. In earlier days, philosophers used the term '
realism Realism, Realistic, or Realists may refer to: In the arts *Realism (arts), the general attempt to depict subjects truthfully in different forms of the arts Arts movements related to realism include: *Classical Realism *Literary realism, a movem ...
' to refer to Plato's belief that his 'forms' are 'real'; nowadays, the term 'realism' often has an almost opposite meaning, so that Plato's belief is sometimes called '
idealism In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, lan ...

idealism
'. Philosophers debate whether entities such as tables and chairs, lions and tigers, philosophical doctrines, numbers, truth, and beauty, are to be regarded as 'things', or as something or nothing 'real'.


Types of ontologies

Ontological theories can be divided into various types according to their theoretical commitments. Particular ontological theories or types of theories are often referred to as "ontologies" ( singular or plural). This usage contrasts with the meaning of "ontology" ( only singular) as a branch of philosophy: the ''science of being'' in general.


Flat vs polycategorical vs hierarchical

One way to divide ontologies is by the number of basic categories they use. ''Monocategorical'' or ''one category ontologies'' hold that there is only one basic category while ''polycategorical ontologies'' imply that there are several distinct basic categories. Another way to divide ontologies is through the notion of ontological hierarchy. Hierarchical ontologies assert that some entities exist on a more fundamental level and that other entities depend on them. Flat ontologies, on the other hand, deny such a privileged status to any entities. Jonathan Schaffer provides an overview of these positions by distinguishing between ''flat'' ontologies (non-hierarchical), ''sorted'' ontologies (polycategorical non-hierarchical) and ''ordered'' ontologies (polycategorical hierarchical). ''Flat'' ontologies are only interested in the difference between existence and non-existence. They are ''flat'' because each flat ontology can be represented by a simple set containing all the entities to which this ontology is committed. An influential exposition of this approach comes from
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 philosophy, analytic tradition, recognized as "one of the most influential philosophers of the ...
which is why it has been referred to as the Quinean approach to meta-ontology. This outlook does not deny that the existing entities can be further subdivided and may stand in various relations to each other. These issues are questions for the more specific sciences, but they do not belong to ontology in the Quinean sense. ''Polycategorical'' ontologies are concerned with the categories of being. Each polycategorical ontology posits a number of categories. These categories are exclusive and exhaustive: every existing entity belongs to exactly one category. A recent example of a polycategorical ontology is E.J. Lowe's four-category-ontology. The four categories are object, kind, mode and attribute. The fourfold structure is based on two distinctions. The first distinction is between substantial entities (objects and kinds) and non-substantial entities (modes and attributes). The second distinction is between particular entities (objects and modes) and universal entities (kinds and attributes). Reality is built up through the interplay of entities belonging to different categories: particular entities instantiate universal entities, and non-substantial entities characterize substantial entities. ''Hierarchical'' ontologies are interested in the degree of fundamentality of the entities they posit. Their main goal is to figure out which entities are fundamental and how the non-fundamental entities depend on them. The concept of fundamentality is usually defined in terms of metaphysical grounding. Fundamental entities are different from non-fundamental entities because they are not grounded in other entities. For example, it is sometimes held that elementary particles are more fundamental than the macroscopic objects (like chairs and tables) they compose. This is a claim about the grounding-relation between microscopic and macroscopic objects. Schaffer's priority monism is a recent form of a hierarchical ontology. He holds that on the most fundamental level there exists only one thing: the world as a whole. This thesis does not deny our common-sense intuition that the distinct objects we encounter in our everyday affairs like cars or other people exist. It only denies that these objects have the most fundamental form of existence. An example of a ''hierarchical'' ontology in
continental philosophy Continental philosophy is a set of 19th- and 20th-century philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, existence, knowledge Knowledge is a familiarity, awarenes ...
comes from
Nicolai Hartmann Paul Nicolai Hartmann (; 20 February 1882 – 9 October 1950) was a Baltic German The Baltic Germans (german: Deutsch-Balten or , later ; and остзейцы ''ostzeitsy'' 'Balters' in Russian) are ethnic German inhabitants of the eastern ...
. He asserts that reality is made up of four levels: the inanimate, the biological, the psychological and the spiritual. These levels form a hierarchy in the sense that the higher levels depend on the lower levels while the lower levels are indifferent to the higher levels.


Thing ontologies vs fact ontologies

''Thing ontologies'' and ''fact ontologies'' are one-category-ontologies: they both hold that all fundamental entities belong to the same category. They disagree on whether this category is the category of things or of facts. A slogan for fact ontologies comes from
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

Ludwig Wittgenstein
: "The world is the totality of facts, not of things". One difficulty in characterizing this dispute is to elucidate what things and facts are, and how they differ from each other. Things are commonly contrasted with the properties and relations they instantiate. Facts, on the other hand, are often characterized as having these things and the properties/relations as their constituents. This is reflected in a rough linguistic characterization of this difference where the subjects and objects of an assertion refer to things while the assertion as a whole refers to a fact. Reism is one form of thing ontology.
Franz Brentano Franz Clemens Honoratus Hermann Josef Brentano (; ; 16 January 1838 – 17 March 1917) was an influential German philosopher, psychologist, and Catholic priest whose work strongly influenced not only students Edmund Husserl, Sigmund Freud Si ...
developed a version of reism in his later philosophy. He held that only concrete particular things exist. Things can exist in two forms: either as spatio-temporal bodies or as temporal souls. Brentano was aware of the fact that many common-sense expressions seem to refer to entities that do not have a place in his ontology, like properties or intentional objects. This is why he developed a method to paraphrase these expressions in order to avoid these ontological commitments. D. M. Armstrong is a well-known defender of fact ontology. He and his followers refer to facts as states of affairs. States of affairs are the basic building blocks of his ontology: they have particulars and universals as their constituents but they are primary in relation to particulars and universals. States of affairs have ontologically independent existence while " propertied particulars and uninstantiated universals are false abstractions".


Constituent ontologies vs blob theories

''Constituent ontologies'' and ''blob theories'', sometimes referred to as ''relational ontologies'', are concerned with the internal structure of objects. Constituent ontologies hold that objects have an internal structure made up of constituents. This is denied by blob theories: they contend that objects are structureless "blobs". Bundle theories are examples of constituent ontologies. Bundle theorists assert that an object is nothing but the properties it "has". On this account, a regular apple could be characterized as a bundle of redness, roundness, sweetness, etc. Defenders of bundle theory disagree on the nature of the bundled properties. Some affirm that these properties are universals while others contend that they are particulars, so-called "tropes". Class
nominalism In metaphysics Metaphysics is the branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of ...
, on the other hand, is a form of blob theory. Class nominalists hold that properties are classes of things. To instantiate a property is merely to be a member of the corresponding class. So properties are not constituents of the objects that have them.


Information science

In
information science Information science (also known as information studies) is an academic field which is primarily concerned with analysis, collection, classification Classification is a process related to categorization Categorization is the human ability a ...
ontologies are classified in various ways, using criteria such as the degree of abstraction and field of application: # ''
Upper ontology In information science, an upper ontology (also known as a top-level ontology, upper model, or foundation ontology) is an Ontology (computer science), ontology (in the sense used in information science) which consists of very general terms (such a ...
'': concepts supporting development of an ontology, meta-ontology. # '' Domain ontology'': concepts relevant to a particular topic,
domain of discourse In the formal sciences Formal science is a branch of science studying formal language disciplines concerned with formal systems, such as logic Logic is an interdisciplinary field which studies truth and reasoning Reason is the capacity ...
, or area of interest, for example, to information technology or to computer languages, or to particular branches of science. # ''Interface ontology'': concepts relevant to the juncture of two disciplines. # ''
Process ontology In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, lang ...
'': inputs, outputs, constraints, sequencing information, involved in business or engineering processes.


History


Hindu philosophy

Ontology features in the
Samkhya ''Samkhya'' ( sa, साङ्ख्य, IAST The International Alphabet of Sanskrit Transliteration (IAST) is a transliteration scheme that allows the lossless romanisation of Brahmic family, Indic scripts as employed by Sanskrit and re ...
school of
Hindu philosophy Hindu philosophy encompasses the philosophies, world views and teachings of Hinduism Hinduism () is an Indian religion Indian religions, sometimes also termed Dharmic religions or Indic religions, are the religions that origina ...
from the first millennium BCE. Samkhya philosophy regards the universe as consisting of two independent realities: puruṣa (pure, contentless consciousness) and
prakṛti Prakriti or Prakruti (from Sanskrit language Sanskrit (; attributively , ; nominally , , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ...
(matter). The
substance dualism Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and takes up space * Substance th ...
between puruṣa and prakṛti is similar but not identical to the substance dualism between mind and body that, following the works of , has been central to many disputes in the Western philosophical tradition. Samkhya sees the mind as being the subtle part of prakṛti. It is made up of three faculties: the sense mind (manas), the intellect (
buddhi :''In Hindu mythology Hindu mythology are myths found in Hindu texts such as the Vedic FIle:Atharva-Veda samhita page 471 illustration.png, upright=1.2, The Vedas are ancient Sanskrit texts of Hinduism. Above: A page from the ''Atharv ...

buddhi
), and the ego ( ahaṁkāra). These faculties perform various functions but are by themselves unable to produce consciousness, which belongs to a distinct ontological category and for which puruṣa alone is responsible. The Yoga school agrees with Samkhya philosophy on the fundamental dualism between puruṣa and prakṛti but it differs from Samkhya's atheistic position by incorporating the concept of a "personal, yet essentially inactive, deity" or "personal god" (
Ishvara ''Ishvara'' (Sanskrit Sanskrit (; attributively , ; , , ) is a of that belongs to the branch of the . It arose in South Asia after its predecessor languages had there from the northwest in the late . Sanskrit is the of , the langua ...
).Lloyd Pflueger, Person Purity and Power in Yogasutra, in Theory and Practice of Yoga (Editor: Knut Jacobsen), Motilal Banarsidass, , pages 38-39 These two schools stand in contrast to
Advaita Vedanta ''Advaita Vedānta'' (; sa, अद्वैत वेदान्त, IAST The International Alphabet of Sanskrit Transliteration (IAST) is a transliteration scheme that allows the lossless romanisation Romanization or romanisation, ...
, which is committed to a strict form of
monism Monism attributes oneness or singleness (Greek: μόνος) to a concept e.g., 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., ...
by holding that the apparent plurality of things is an illusion (
Maya Maya may refer to: Civilizations * Maya peoples The Maya peoples () are an ethnolinguistic group of indigenous peoples Indigenous peoples, also referred to as First people, Aboriginal people, Native people, or autochthonous people, are cu ...
) hiding the true oneness of reality at its most fundamental level (
Brahman ''Brahman'' ( sa, ब्रह्मन् , hi, ब्रह्म) connotes the highest Universal Principle, the Ultimate Reality Ultimate reality is "something that is the supreme, final, and fundamental power in all reality". This heav ...

Brahman
).


Ancient Greek

In the Greek philosophical tradition,
Parmenides Parmenides of Elea (; grc-gre, Παρμενίδης ὁ Ἐλεάτης; ) was a pre-Socratic Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Parmenides
was among the first to propose an ontological characterization of the fundamental nature of existence. In the prologue (or ''proem'') to ''On Nature'', he describes two views of
existence Existence is the ability of an entity to interact with physical reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociolog ...

existence
. Initially, nothing comes from nothing, thus
existence Existence is the ability of an entity to interact with physical reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociolog ...

existence
is
eternal Eternal(s) or The Eternal may refer to: * Eternity, an infinite amount of time, or a timeless state * Immortality or eternal life * God, the supreme being, creator deity, and principal object of faith in monotheism Comics, film and television * ...
. This posits that existence is what may be conceived of by thought, created, or possessed. Hence, there may be neither void nor vacuum; and true reality neither may come into being nor vanish from existence. Rather, the entirety of creation is eternal, uniform, and immutable, though not infinite (Parmenides characterized its shape as that of a perfect sphere). Parmenides thus posits that change, as perceived in everyday experience, is illusory. Opposite to the
Eleatic The Eleatics were a Pre-Socratic philosophy, pre-Socratic school of philosophy founded by Parmenides in the early fifth century BC in the ancient town of Velia, Elea. Other members of the school included Zeno of Elea and Melissus of Samos. Xen ...
monism Monism attributes oneness or singleness (Greek: μόνος) to a concept e.g., 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., ...
of
Parmenides Parmenides of Elea (; grc-gre, Παρμενίδης ὁ Ἐλεάτης; ) was a pre-Socratic Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Parmenides
is the pluralistic conception of
being In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, la ...

being
. In the 5th century BC,
Anaxagoras Anaxagoras (; grc-gre, Ἀναξαγόρας, ''Anaxagoras'', "lord of the assembly";  BC) was a Pre-Socratic Pre-Socratic philosophy is ancient Greek philosophy Ancient Greek philosophy arose in the 6th century BC, at a time when the i ...

Anaxagoras
and
Leucippus Leucippus (; el, Λεύκιππος, ''Leúkippos''; fl. 5th century BCE) is reported in some ancient sources to have been a philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλό ...
replaced the reality of ''being'' (unique and unchanging) with that of ''becoming'', therefore by a more fundamental and elementary ''
onticIn philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, existence, knowledge Knowledge is a familiarity, awareness, or understanding of someone or something, such as fact ...
'' plurality. This thesis originated in the
Hellenic world Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization  A civilization (or civilisation) is a complex society A complex society is a concept that is shared by a range of disciplines including anthropology, archaeology, history ...
, stated in two different ways by Anaxagoras and by Leucippus. The first theory dealt with "seeds" (which Aristotle referred to as "''homeomeries''") of the various substances. The second was the atomistic theory, which dealt with reality as based on the
vacuum A vacuum is a space Space is the boundless three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Gr ...

vacuum
, the atoms and their intrinsic movement in it. The materialist ''
atomism Atomism (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximate ...
'' proposed by Leucippus was indeterminist, but
Democritus Democritus (; el, Δημόκριτος, ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Democritus
( 460 – 370 BC) subsequently developed it in a
deterministic Determinism is the philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about existence Existence is the ability of an entity to interact with physical or mental reality Reality is the ...
way. Later (4th century BC),
Epicurus Epicurus, ''Epíkouros'', "ally, comrade" (341–270 BC) was an ancient Greek philosopher and sage who founded Epicureanism Epicureanism is a system of founded around 307 BC based upon the teachings of the . Epicureanism was originally ...

Epicurus
took the original ''atomism'' again as indeterministic. He saw reality as composed of an infinity of indivisible, unchangeable corpuscles or
atom An atom is the smallest unit of ordinary 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 ato ...

atom
s (from the Greek ''atomon'', lit. 'uncuttable'), but he gives weight to characterize atoms whereas for Leucippus they are characterized by a "figure", an "order" and a "position" in the cosmos. Atoms are, besides, creating the whole with the intrinsic movement in the ''vacuum'', producing the diverse flux of being. Their movement is influenced by the ''parenklisis'' (
Lucretius Titus Lucretius Carus ( , ; 99 – c. 55 BC) was a Roman Roman or Romans most often refers to: *, the capital city of Italy *, Roman civilization from 8th century BC to 5th century AD *, the people of ancient Rome *', shortened to ''Rom ...
names it ''
clinamen Clinamen (; plural ''clinamina'', derived from ''clīnāre'', to incline) is the Latin language, Latin name Lucretius gave to the unpredictable swerve of ancient atom, atoms, in order to defend the atomism, atomistic doctrine of Epicurus. In modern ...
'') and that is determined by chance. These ideas foreshadowed the understanding of until the advent of 20th-century theories on the nature of atoms.


Plato

Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was an Classical Athens, Athenian philosopher during the Classical Greece, Classical period in Ancient Greece, founder of the Platonist school of thought and the Platoni ...

Plato
developed the distinction between true reality and illusion, in arguing that what is real are eternal and unchanging
forms Form is the shape, visual appearance, or :wikt:configuration, configuration of an object. In a wider sense, the form is the way something happens. Form also refers to: *Form (document), a document (printed or electronic) with spaces in which to w ...
or ideas (a precursor to ''universals''), of which things experienced in sensation are at best merely copies, and real only in so far as they copy ("partake of") such forms. In general, Plato presumes that all nouns (e.g., "beauty") refer to real entities, whether sensible bodies or insensible forms. Hence, in ''The Sophist'', Plato argues that ''being'' is a ''form'' in which all existent things participate and which they have in common (though it is unclear whether "Being" is intended in the sense of
existence Existence is the ability of an entity to interact with physical reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociolog ...

existence
, copula, or
identity Identity may refer to: Social sciences * Identity (social science), personhood or group affiliation in psychology and sociology Group expression and affiliation * Cultural identity, a person's self-affiliation (or categorization by others ...
); and argues, against
Parmenides Parmenides of Elea (; grc-gre, Παρμενίδης ὁ Ἐλεάτης; ) was a pre-Socratic Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Parmenides
, that forms must exist not only of ''being'', but also of
Negation In logic Logic is an interdisciplinary field which studies truth and reasoning Reason is the capacity of consciously making sense of things, applying logic Logic (from Ancient Greek, Greek: grc, wikt:λογική, λογική, ...

Negation
and of non-being (or ''Difference'').


Aristotle

In his ''Categories'', Aristotle (384–322 BCE) identifies ten possible kinds of things that may be the subject or the predicate of a proposition. For Aristotle there are four different ontological dimensions: # according to the various categories or ways of addressing a being as such # according to its truth or falsity (e.g. fake gold, counterfeit money) # whether it exists in and of itself or simply 'comes along' by accident # according to its potency, movement (energy) or finished presence ( ''Metaphysics'' Book Theta).


Medieval

''Medieval ontology'' was strongly influenced by Aristotle's teachings. The thinkers of this period often relied on Aristotelian categories like ''substance'', ''act and potency'' or ''matter and form'' to formulate their own theories. Important ontologists in this epoch include Avicenna, Thomas Aquinas,
Duns Scotus John Duns ( – 8 November 1308), commonly called Duns Scotus ( ; ; "Duns the Scot"), was a Scottish Catholic priest and Franciscan friar The Franciscans are a group of related Mendicant orders, mendicant Christianity, Christian Ca ...

Duns Scotus
and
William of Ockham William of Ockham (; also Occam, from la, Gulielmus Occamus; 1287 – 10 April 1347) was an English Franciscan friar The Franciscans are a group of related Mendicant orders, mendicant Christianity, Christian Catholic religious order, relig ...

William of Ockham
.


Avicenna ''aka'' Ibn Sina

According to Avicenna (also known as
Ibn Sina Ibn Sina ( fa, ابن سینا), also known as Abu Ali Sina (), Pur Sina (), and often known in the West as Avicenna (;  – June 1037), was a Persian Persian may refer to: * People and things from Iran, historically called ''Persia' ...
) ( 980 – 1037), and in an interpretation of Greek Aristotelian and Platonist ontological doctrines in medieval
metaphysics Metaphysics is the branch of philosophy that studies the first principles of being, identity and change, space and time, causality, necessity and possibility. It includes questions about the nature of consciousness and the relationship between ...

metaphysics
, being is either necessary, contingent ''qua'' possible, or impossible. Necessary being is that which cannot but be, since its non-being would entail a contradiction. Contingent ''qua'' possible being is neither necessary nor impossible for it to be or not to be. It is ontologically neutral, and is brought from potential existing into actual existence by way of a cause that is external to its essence. Its being is borrowed – unlike the necessary existent, which is self-subsisting and impossible not to be. As for the impossible, it necessarily does not exist, and the affirmation of its being would involve a contradiction.


Aquinas

Fundamental to
Thomas Aquinas Thomas Aquinas (; it, Tommaso d'Aquino, lit=Thomas of Aquino, Italy, Aquino; 1225 – 7 March 1274) was an Italian Dominican Order, Dominican friar, Philosophy, philosopher, Catholic priest, and Doctor of the Church. An immensely influential ...

Thomas Aquinas
's ontology is his distinction between
essence Essence ( la, essentia) is a polysemic Polysemy ( or ; from grc-gre, πολύ-, , "many" and , , "sign") is the capacity for a word or phrase to have multiple meanings, usually related by contiguity of meaning within a semantic field. Polyse ...
and
existence Existence is the ability of an entity to interact with physical reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociolog ...

existence
: all entities are conceived as composites of essence and existence. The essence of a thing is what this thing is like, it signifies the definition of this thing. God has a special status since He is the only entity whose essence is identical to its existence. But for all other, finite entities there is a ''real distinction'' between essence and existence. This distinction shows itself, for example, in our ability to understand the essence of something without knowing about its existence. Aquinas conceives of existence as an ''act of being'' that actualizes the potency given by the essence. Different things have different essences, which impose different limits on the corresponding ''act of being''. The paradigm examples of essence-existence-composites are material substances like cats or trees. Aquinas incorporates Aristotle's distinction between matter and form by holding that the essence of ''material'' things, as opposed to the essence of ''immaterial'' things like angels, is the composition of their matter and form. So, for example, the essence of a marble statue would be the composition of the marble (its matter) and the shape it has (its form). Form is universal since substances made of different matter can have the same form. The forms of a substance may be divided into substantial and accidental forms. A substance can survive a change of an accidental form but ceases to exist upon a change of a substantial form.


Modern

Ontology is increasingly seen as a separate domain of philosophy in the ''modern period''. Many ontological theories of this period were rationalistic in the sense that they saw ontology largely as a deductive discipline that starts from a small set of first principles or axioms, a position best exemplified by Baruch Spinoza and Christian Wolff. This rationalism in metaphysics and ontology was strongly opposed by
Immanuel Kant Immanuel Kant (, , ; 22 April 1724 – 12 February 1804) was a German philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about r ...

Immanuel Kant
, who insisted that many claims arrived at this way are to be dismissed since they go beyond any possible experience that could justify them.


Descartes

René Descartes René Descartes ( or ; ; Latinized Latinisation or Latinization can refer to: * Latinisation of names, the practice of rendering a non-Latin name in a Latin style * Latinisation in the Soviet Union, the campaign in the USSR during the 1920s ...

René Descartes
' ontological distinction between mind and body has been one of the most influential parts of his philosophy. On his view, minds are thinking things while bodies are extended things. ''Thought'' and ''extension'' are two ''attributes'' that each come in various ''modes'' of being. Modes of ''thinking'' include judgments, doubts, volitions, sensations and emotions while the shapes of material things are modes of ''extension''. Modes come with a lower degree of reality since they depend for their existence on a substance. Substances, on the other hand, can exist on their own. Descartes'
substance dualism Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and takes up space * Substance th ...
asserts that every finite substance is either a thinking substance or an extended substance. This position does not entail that minds and bodies ''actually are'' separated from each other, which would defy the intuition that we both have a body and a mind. Instead, it implies that minds and bodies ''can'', at least in principle, be separated, since they are distinct substances and therefore are capable of independent existence. A longstanding problem for substance dualism since its inception has been to explain how minds and bodies can causally interact with each other, as they apparently do, when a volition causes an arm to move or when light falling on the retina causes a visual impression.


Spinoza

Baruch Spinoza Baruch (de) Spinoza (; ; ; born Baruch Espinosa; later as an author and a correspondent Benedictus de Spinoza, anglicized to Benedict de Spinoza; 24 November 1632 – 21 February 1677) was a Dutch philosopher of Spanish and Portuguese Jews, Por ...

Baruch Spinoza
is well-known for his ''substance monism:'' the thesis that only one substance exists. He refers to this substance as "God or Nature", emphasizing both his
pantheism Pantheism is the belief that reality Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary Imaginary may refer to: * Imaginary (sociology), a concept in sociology * The ...

pantheism
and his naturalism. This substance has an infinite amount of attributes, which he defines as "what the intellect perceives of substance as constituting its essence". Of these attributes, only two are accessible to the human mind: thought and extension. ''Modes'' are properties of a substance that follow from its attributes and therefore have only a dependent form of existence. Spinoza sees everyday-things like rocks, cats or ourselves as mere modes and thereby opposes the traditional
Aristotelian Aristotelian may refer to: * Aristotle (384–322 BCE), Greek philosopher * Aristotelianism, the philosophical tradition begun by Aristotle * Aristotelian ethics * Aristotelian logic, term logic * Aristotelian physics, the natural sciences * Aristot ...

Aristotelian
and conception of categorizing them as substances. Modes compose
deterministic Determinism is the philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about existence Existence is the ability of an entity to interact with physical or mental reality Reality is the ...

deterministic
systems in which the different modes are linked to each other as cause and effect. Each deterministic system corresponds to one attribute: one for extended things, one for thinking things, etc. Causal relations only happen within a system while the different systems run in parallel without causally interacting with each other. Spinoza calls the system of modes ''Natura naturata'' ("nature natured") and opposes it to ''Natura naturans'' ("nature naturing"), the attributes responsible for the modes. Everything in Spinoza's system is necessary: there are no contingent entities. This is so since the attributes are themselves necessary and since the system of modes follows from them.


Wolff

defines ontology as the science of being in general. He sees it as a part of metaphysics besides cosmology, psychology and natural theology. According to Wolff, it is a
deductive Deductive reasoning, also deductive logic, is the process of reasoning Reason is the capacity of consciously applying logic Logic is an interdisciplinary field which studies truth and reasoning Reason is the capacity of consciously making ...
science, knowable
a priori ''A priori'' and ''a posteriori'' ('from the earlier' and 'from the later', respectively) are Latin phrases used in philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaph ...
and based on two fundamental principles: the
principle of non-contradiction In logic Logic (from Ancient Greek, Greek: grc, wikt:λογική, λογική, label=none, lit=possessed of reason, intellectual, dialectical, argumentative, translit=logikḗ)Also related to (''logos''), "word, thought, idea, argument, ...
("it cannot happen that the same thing is and is not") and the
principle of sufficient reason The principle of sufficient reason states that everything must have a reason Reason is the capacity of consciously applying logic Logic is an interdisciplinary field which studies truth and reasoning Reason is the capacity of consciously ...
("nothing exists without a sufficient reason for why it exists rather than does not exist"). ''Beings'' are defined by their ''determinations'' or ''predicates'', which cannot involve a contradiction. Determinates come in 3 types: ''essentialia'', ''attributes'', and ''modes''. ''Essentialia'' define the nature of a being and are therefore necessary properties of this being. ''Attributes'' are determinations that follow from essentialia and are equally necessary, in contrast to ''modes'', which are merely contingent. Wolff conceives ''existence'' as just one determination among others, which a being may lack. Ontology is interested in being at large, not just in actual being. But all beings, whether actually existing or not, have a sufficient reason. The sufficient reason for things without actual existence consists in all the determinations that make up the essential nature of this thing. Wolff refers to this as a "reason of being" and contrasts it with a "reason of becoming", which explains why some things have actual existence.


Schopenhauer

Arthur Schopenhauer Arthur Schopenhauer (; ; 22 February 1788 – 21 September 1860) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citize ...
was a proponent of
metaphysical voluntarism Voluntarism is "any metaphysical or psychological system that assigns to the Will (philosophy), will (Latin: ''voluntas'') a more predominant role than that attributed to the intellect",


20th century

Dominant approaches to ontology in the ''20th century'' were phenomenology, linguistic analysis and naturalism. ''Phenomenological ontology'', as exemplified by Edmund Husserl and Martin Heidegger, relies for its method on the description of experience. ''Linguistic analysis'' assigns to language a central role for ontology, as seen, for example, in Rudolf Carnap's thesis that the truth value of existence-claims depends on the linguistic framework in which they are made. ''Naturalism'' gives a prominent position to the natural sciences for the purpose of finding and evaluating ontological claims. This position is exemplified by Quine's method of ontology, which involves analyzing the ontological commitments of scientific theories.


Husserl

Edmund Husserl sees ontology as a ''science of essences''. ''Sciences of essences'' are contrasted with ''factual sciences'': the former are knowable
a priori ''A priori'' and ''a posteriori'' ('from the earlier' and 'from the later', respectively) are Latin phrases used in philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaph ...
and provide the foundation for the later, which are knowable a posteriori. Ontology as a science of essences is not interested in ''actual facts'', but in the essences themselves, whether they ''have instances or not''. Husserl distinguishes between ''formal ontology'', which investigates the essence of ''objectivity in general'', and ''regional ontologies'', which study ''regional essences'' that are shared by all entities belonging to the region. Regions correspond to the highest genera of Abstract and concrete, concrete entities: material nature, personal consciousness and interpersonal spirit. Husserl's method for studying ontology and sciences of essence in general is called eidetic variation. It involves imagining an object of the kind under investigation and varying its features. The changed feature is ''inessential'' to this kind if the object can survive its change, otherwise it belongs to the ''kind's essence''. For example, a triangle remains a triangle if one of its sides is extended but it ceases to be a triangle if a fourth side is added. Regional ontology involves applying this method to the essences corresponding to the highest genera.


Heidegger

Central to Martin Heidegger's philosophy is the notion of ''ontological difference'': the difference between ''being'' as such and specific entities. He accuses the philosophical tradition of being ''forgetful'' of this distinction, which has led to the mistake of understanding ''being'' as such as a kind of ultimate entity, for example as "idea, energeia, substance, monad or will to power". Heidegger tries to rectify this mistake in his own "fundamental ontology" by focusing on the ''meaning of being'' instead, a project which is akin to contemporary meta-ontology. One method to achieve this is by studying the human being, or Dasein, in Heidegger's terminology. The reason for this is that we already have a ''pre-ontological understanding'' of ''being'' that shapes how we experience the world. Phenomenology (philosophy), Phenomenology can be used to make this implicit understanding explicit, but it has to be accompanied by Hermeneutics#Heidegger (1889–1976), hermeneutics in order to avoid the distortions due to the ''forgetfulness of being''. In his later philosophy, Heidegger attempted to reconstruct the "history of being" in order to show how the different epochs in the history of philosophy were dominated by different conceptions of ''being''. His goal is to retrieve the ''original experience of being'' present in the Pre-Socratic philosophy, early Greek thought that was covered up by later philosophers.


Hartmann

Nicolai Hartmann Paul Nicolai Hartmann (; 20 February 1882 – 9 October 1950) was a Baltic German The Baltic Germans (german: Deutsch-Balten or , later ; and остзейцы ''ostzeitsy'' 'Balters' in Russian) are ethnic German inhabitants of the eastern ...
is a 20th-century philosopher within the Continental philosophy, continental tradition of philosophy. He interprets ontology as Aristotle's science of being qua being: the science of the most general characteristics of entities, usually referred to as categories, and the relations between them. According to Hartmann, the most general categories are ''moments of being'' (existence and essence), ''modes of being'' (reality and ideality) and ''modalities of being'' (possibility, actuality and necessity). Every entity has both ''existence'' and ''essence''. ''Reality'' and ''ideality'', by contrast, are two disjunctive categories: every entity is either real or ideal. Ideal entities are universal, returnable and always existing while real entities are individual, unique and destructible. Among the ideal entities are mathematical objects and values. The ''modalities of being'' are divided into the absolute modalities (actuality and non-actuality) and the relative modalities (possibility, impossibility and necessity). The relative modalities are ''relative'' in the sense that they depend on the absolute modalities: something is possible, impossible or necessary because something else is actual. Hartmann asserts that reality is made up of four levels (''inanimate'', ''biological'', ''psychological'' and ''spiritual'') that form a hierarchy.


Carnap

Rudolf Carnap proposed that the truth value of ontological statements about the existence of entities depends on the linguistic framework in which these statements are made: they are Internal-external distinction, internal to the framework. As such, they are often trivial in that it just depends on the rules and definitions within this framework. For example, it follows analytically from the rules and definitions within the mathematical framework that numbers exist. The problem Carnap saw with traditional ontologists is that they try to make framework-independent or ''external'' statements about what ''really'' is the case. Such statements are at best ''pragmatic considerations'' about which framework to choose and at worst outright ''meaningless'', according to Carnap. For example, there is no matter of fact as to whether Realism (philosophical), realism or
idealism In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, lan ...

idealism
is true, their truth depends on the adopted framework. The job of philosophers is not to discover which things exist by themselves but "conceptual engineering": to create interesting frameworks and to explore the consequences of adopting them. The choice of framework is guided by practical considerations like expedience or fruitfulness since there is no framework-independent notion of truth.


Quine

The notion of ontological commitment plays a central role in
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 philosophy, analytic tradition, recognized as "one of the most influential philosophers of the ...
's contributions to ontology. A theory is ontologically committed to an entity if that entity must exist in order for the theory to be true. Quine proposed that the best way to determine this is by translating the theory in question into first-order predicate logic. Of special interest in this translation are the logical constants known as existential quantification, existential quantifiers, whose meaning corresponds to expressions like "there exists..." or "for some...". They are used to First-order logic#Free and bound variables, bind the variables in the expression following the quantifier. The ontological commitments of the theory then correspond to the variables bound by existential quantifiers. This approach is summed up by Quine's famous dictum that "[t]o be is to be the value of a variable". This method by itself is not sufficient for ontology since it depends on a theory in order to result in ontological commitments. Quine proposed that we should base our ontology on our best scientific theory. Various followers of Quine's method chose to apply it to different fields, for example to "everyday conceptions expressed in natural language".


Other ontological topics


Ontological formations

The concept of ''ontological formations'' refers to formations of social relations understood as dominant ways of living. Temporal, spatial, corporeal, Epistemology, epistemological, and performative relations are taken to be central to understanding a dominant formation. That is, a particular ontological formation is based on how ontological categories of time, space, embodiment, knowing and performing are lived—objectively and subjectively. Different ontological formations include the ''customary'' (including the tribal), the ''traditional'', the ''modern'', and the ''postmodern''. The concept was first introduced by Paul James (academic), Paul James in 2006, together with a series of writers including Damian Grenfell and Manfred Steger. In the ''engaged theory'' approach, ontological formations are seen as layered and intersecting rather than singular formations. They are 'formations of being'. This approach avoids the usual problems of a Great Divide being posited between the modern and the pre-modern. From a philosophical distinction concerning different formations of being, the concept then provides a way of translating into practical understandings concerning how humans might design cities and communities that live creatively across different ontological formations, for example cities that are not completely dominated by modern valences of spatial configuration. Here the work of Tony Fry is important.


Ontology of fictional characters

According to Edward N. Zalta, the ontology of fiction analyses such sentences as: * 'Nero worshipped (the god) Mars (mythology), Mars;' * 'Mars (mythology), Mars, the god, does not exist;' and * 'Eliza Doolittle, in George Bernard Shaw's Pygmalion (play), ''Pygmalion'', is a flower girl.' According to Amie L. Thomasson, fictional discourse can be of four sorts: * Uttered ''within'' works of fiction; * Philosophical exercises such as 'Captain Marvel (DC Comics), Captain Marvel does not exist'; * Treating fictional characters as if they were 'real', such as 'Superman can leap tall buildings;' and * Discourse ''about'' works of fiction, such as 'Pygmalion (play), Professor Higgins was created by George Bernard Shaw'. Jeremy Bentham distinguished three kinds of entities: * the ''real'': those that can be perceived, or can be inferred from perception. * the ''fictitious'': abstractions that referred to perceptible things. * the ''fabulous'': those that can be found only in the imagination, where the word 'exist' applies to such only in the sense that they do not really exist. Francis Herbert Bradley thought that real things exist respectively at particular times and places. He recognised several kinds of entity: *the genuinely historical; * the fictional; * the real; * the merely imagined; * the existent; and * the non-existent. Alexius Meinong would put fictional entities into the category which he called ''subsistence''. This category contains objects that neither exist spatially or non-spatially. However, they do have properties. The properties are given to these objects in the way they are said to be described. For example, we can talk about the tall unicorn even though the tall unicorn does not exist. We can say the unicorn is in fact tall because this follows from the properties in which the object is characterized.


Ontological and epistemological certainty

René Descartes René Descartes ( or ; ; Latinized Latinisation or Latinization can refer to: * Latinisation of names, the practice of rendering a non-Latin name in a Latin style * Latinisation in the Soviet Union, the campaign in the USSR during the 1920s ...

René Descartes
, with ''cogito, ergo sum'' (''je pense donc je suis,'' "I think, therefore I am"), argued that a person's thinking agency, his ''res cogitans'', as distinct from his material body, his ''res extensa'', is something that we can know exists with epistemology, epistemological certainty. Descartes argued further that this knowledge could lead to a proof of the certainty of the existence of God, using the ontological argument that had been formulated first by Anselm of Canterbury.


Body and environment, questioning the meaning of being

Schools of metaphysical subjectivism, subjectivism, metaphysical objectivism, objectivism and relativism existed at various times in the 20th century, and the postmodernism, postmodernists and embodied philosophy, body philosophers tried to reframe all these questions in terms of bodies taking some specific philosophy of action, action in an environment. This relied to a great degree on insights derived from scientific research into animals taking instinctive action in natural and artificial settings—as studied by biology, ecology, and cognitive science. The processes by which bodies related to environments became of great concern, and the idea of
being In philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about Metaphysics, existence, reason, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Philosophy of language, la ...

being
itself became difficult to really define. What did people mean when they said "A is B", "A must be B", "A was B"...? Some linguists advocated dropping the verb "to be" from the English language, leaving "E-Prime, E Prime", supposedly less prone to bad abstractions. Others, mostly philosophers, tried to dig into the word and its usage. Martin Heidegger distinguished ''human being'' as ''existence'' from the being of things in the world. Heidegger proposes that our way of being human and the way the world is for us are cast historically through a fundamental ontological questioning. These fundamental ontological categories provide the basis for communication in an age: a horizon of unspoken and seemingly unquestionable background meanings, such as human beings understood unquestioningly as subjects and other entities understood unquestioningly as objects. Because these basic ontological meanings both generate and are regenerated in everyday interactions, the locus of our way of being in a historical epoch is the communicative event of language in use.Hyde, R. Bruce. "Listening Authentically: A Heideggerian Perspective on Interpersonal Communication". In ''Interpretive Approaches to Interpersonal Communication'', edited by Kathryn Carter and Mick Presnell. State University of New York Press, 1994. For Heidegger, however, communication in the ''first'' place is not among human beings, but language itself shapes up in response to questioning (the inexhaustible meaning of) being. Even the focus of traditional ontology on the 'whatness' or ''quidditas'' of beings in their substantial, standing presence can be shifted to pose the question of the 'whoness' of human being itself.


Ontology and language

Some philosophers suggest that the question of "What is?" is (at least in part) an issue of ''usage'' rather than a question about facts. This perspective is conveyed by an analogy made by Donald Davidson (philosopher), Donald Davidson: Suppose a person refers to a 'cup' as a 'chair' and makes some comments pertinent to a cup, but uses the word 'chair' consistently throughout instead of 'cup'. One might readily catch on that this person simply calls a 'cup' a 'chair' and the oddity is explained. Davidson refers to a 'ketch' and a 'yawl' (p. 18). Analogously, if we find people asserting 'there are' such-and-such, and we do not ourselves think that 'such-and-such' exist, we might conclude that these people are not nuts (Davidson calls this assumption 'charity'), they simply use 'there are' differently than we do. The question of ''What is?'' is at least partly a topic in the philosophy of language, and is not entirely about ontology itself. This viewpoint has been expressed by Eli Hirsch.Hirsch, Eli. 2011.
Physical-object ontology, verbal disputes and common sense
" Pp. 144–77 in ''Quantifier Variance and Realism: Essays in Metaontology''. New York: Oxford University Press. . First published as
Physical-Object Ontology, Verbal Disputes, and Common Sense
"
Hirsch, Eli. 2011.
Quantifier variance and realism
" Pp. 68–95 in ''Quantifier Variance and Realism: Essays in Metaontology''. New York: Oxford University Press. . First published as
Quantifier variance and realism
"
Hirsch interprets Hilary Putnam as asserting that different concepts of "the existence of something" can be correct. This position does not contradict the view that some things do exist, but points out that different 'languages' will have different rules about assigning this property. How to determine the 'fitness' of a 'language' to the world then becomes a subject for investigation. Common to all Indo-European copula languages is the double use of the verb "to be" in both stating that entity X exists ("X is.") as well as stating that X has a property ("X is P"). It is sometimes argued that a third use is also distinct, stating that X is a member of a class ("X is a C"). In other language families these roles may have completely different verbs and are less likely to be confused with one another. For example they might say something like "the car has redness" rather than "the car is red." Hence any discussion of "being" in Indo-European language philosophy may need to make distinctions between these senses.


Ontology and human geography

In human geography there are two types of ontology: small "o" which accounts for the practical orientation, describing functions of being a part of the group, thought to oversimplify and ignore key activities. The other "o", or big "O", systematically, logically, and rationally describes the essential characteristics and universal traits. This concept relates closely to Plato's view that the human mind can only perceive a bigger world if they continue to live within the confines of their "caves". However, in spite of the differences, ontology relies on the symbolic agreements among members. That said, ontology is crucial for the axiomatic language frameworks.


Reality and actuality

According to Alfred North Whitehead, Alfred N. Whitehead, for ontology, it is useful to distinguish the terms 'reality' and 'actuality'. In this view, an 'actual entity' has a philosophical status of fundamental ontological priority, while a 'real entity' is one which may be actual, or may derive its reality from its logical relation to some actual entity or entities. For example, an occasion in the life of Socrates is an actual entity. But Socrates' being a man does not make 'man' an actual entity, because it refers indeterminately to many actual entities, such as several occasions in the life of Socrates, and also to several occasions in the lives of Alcibiades, and of others. But the notion of man is real; it derives its reality from its reference to those many actual occasions, each of which is an actual entity. An actual occasion is a concrete entity, while terms such as 'man' are abstractions from many concrete relevant entities. According to Whitehead, an actual entity must earn its philosophical status of fundamental ontological priority by satisfying several philosophical criteria, as follows: * There is no going behind an actual entity, to find something more fundamental in fact or in efficacy. This criterion is to be regarded as expressing an axiom, or postulated distinguished doctrine. * An actual entity must be completely determinate in the sense that there may be no confusion about its identity that would allow it to be confounded with another actual entity. In this sense an actual entity is completely concrete, with no potential to be something other than itself. It is what it is. It is a source of potentiality for the creation of other actual entities, of which it may be said to be a part cause. Likewise it is the concretion or realization of potentialities of other actual entities which are its partial causes. * Causation between actual entities is essential to their actuality. Consequently, for Whitehead, each actual entity has its distinct and definite extension in physical Minkowski space, and so is uniquely identifiable. A description in Minkowski space supports descriptions in time and space for particular observers. * It is part of the aim of the philosophy of such an ontology as Whitehead's that the actual entities should be all alike, ''qua'' actual entities; they should all satisfy a single definite set of well stated ontological criteria of actuality. Whitehead proposed that his notion of an occasion of experience satisfies the criteria for its status as the philosophically preferred definition of an actual entity. From a purely logical point of view, each occasion of experience has in full measure the characters of both objective and subjective reality. Subjectivity and objectivity refer to different aspects of an occasion of experience, and in no way do they exclude each other. Examples of other philosophical proposals or candidates as actual entities, in this view, are Aristotle's 'substances', Leibniz' monads, and Descartes' ''res verae'', and the more modern 'states of affairs'. Aristotle's substances, such as Socrates, have behind them as more fundamental the 'primary substances', and in this sense do not satisfy Whitehead's criteria. Whitehead is not happy with Leibniz' monads as actual entities because they are "windowless" and do not cause each other. 'States of affairs' are often not closely defined, often without specific mention of extension in physical Minkowski space; they are therefore not necessarily processes of becoming, but may be as their name suggests, simply static states in some sense. States of affairs are contingent on particulars, and therefore have something behind them. One summary of the Whiteheadian actual entity is that it is a process of becoming. Another summary, referring to its causal linkage to other actual entities, is that it is "all window", in contrast with Leibniz' windowless monads. This view allows philosophical entities other than actual entities to really exist, but not as fundamentally and primarily factual or causally efficacious; they have existence as abstractions, with reality only derived from their reference to actual entities. A Whiteheadian actual entity has a unique and completely definite place and time. Whiteheadian abstractions are not so tightly defined in time and place, and in the extreme, some are timeless and placeless, or 'eternal' entities. All abstractions have logical or conceptual rather than efficacious existence; their lack of definite time does not make them unreal if they refer to actual entities. Whitehead calls this 'the ontological principle'.


Microcosmic ontology

There is an established and long philosophical history of the concept of atoms as microscopic physical objects. They are far too small to be visible to the naked eye. It was as recent as the nineteenth century that precise estimates of the sizes of putative physical
atom An atom is the smallest unit of ordinary 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 ato ...

atom
s began to become plausible. Almost direct empirical observation of atomic effects was due to the theoretical investigation of Brownian motion by Albert Einstein in the very early twentieth century. But even then, the real existence of atoms was debated by some. Such debate might be labeled 'microcosmic ontology'. Here the word 'microcosm' is used to indicate a physical world of small entities, such as for example atoms. Subatomic particles are usually considered to be much smaller than atoms. Their real or actual existence may be very difficult to demonstrate empirically. A distinction is sometimes drawn between actual and virtual particle, virtual subatomic particles. Reasonably, one may ask, in what sense, if any, do virtual particles exist as physical entities? For atomic and subatomic particles, difficult questions arise, such as do they possess a precise position, or a precise momentum? A question that continues to be controversial is "to what kind of physical thing, if any, does the Quantum mechanics, quantum mechanical wave function refer?"Isham, C. J. 1995. ''Lectures on Quantum Theory: Mathematical and Structural Foundations.'' London: Imperial College Press. . pp. 63–7.


Ontological argument

In the Christian philosophy, Western Christian tradition, in his 1078 work ''Proslogion'', Anselm of Canterbury proposed what is known as 'the ontological argument' for the existence of God. Anselm defined God as "that than which nothing greater can be thought", and argued that this being must exist in the mind, even in the mind of the person who denies the existence of God. He suggested that, if the greatest possible being exists in the mind, it must also exist in reality. If it only exists in the mind, then an even greater being must be possible—one which exists both in the mind and in reality. Therefore, this greatest possible being must exist in reality. Seventeenth century French philosopher
René Descartes René Descartes ( or ; ; Latinized Latinisation or Latinization can refer to: * Latinisation of names, the practice of rendering a non-Latin name in a Latin style * Latinisation in the Soviet Union, the campaign in the USSR during the 1920s ...

René Descartes
deployed a similar argument. Descartes published several variations of his argument, each of which centred on the idea that God's existence is immediately inferable from a "clear and distinct" idea of a supremely perfect being. In the early eighteenth century, Gottfried Leibniz augmented Descartes' ideas in an attempt to prove that a "supremely perfect" being is a coherent concept. Norman Malcolm revived the ontological argument in 1960 when he located a second, stronger ontological argument in Anselm's work; Alvin Plantinga challenged this argument and proposed an alternative, based on modal logic. Attempts have also been made to validate Anselm's proof using an automated theorem prover. More recently, Kurt Gödel proposed a Mathematical logic, formal argument Gödel's ontological proof, for God's existence. Other arguments for God's existence have been advanced, including those made by Islamic philosophers Mulla Sadra and Allama Tabatabai.


Hintikka's locution for existence

Jaakko Hintikka puts the view that a useful explication of the notion of existence is in the words "one can find," implicitly in some world or Domain of discourse, universe of discourse.Jaakko Hintikka, Hintikka, Jaakko. 1998. ''Paradigms for Language Theory and Other Essays''. Dordrecht: Springer Science+Business Media. . p. 3.


Prominent ontologists

* Anselm of Canterbury *
Thomas Aquinas Thomas Aquinas (; it, Tommaso d'Aquino, lit=Thomas of Aquino, Italy, Aquino; 1225 – 7 March 1274) was an Italian Dominican Order, Dominican friar, Philosophy, philosopher, Catholic priest, and Doctor of the Church. An immensely influential ...

Thomas Aquinas
* Aristotle * Avicenna * David Malet Armstrong * Alain Badiou * Gustav Bergmann * Roy Bhaskar * Bernard Bolzano *
Franz Brentano Franz Clemens Honoratus Hermann Josef Brentano (; ; 16 January 1838 – 17 March 1917) was an influential German philosopher, psychologist, and Catholic priest whose work strongly influenced not only students Edmund Husserl, Sigmund Freud Si ...
* Martin Buber * Mario Bunge * Rudolf Carnap * Ernst Cassirer * Gilles Deleuze * Daniel Dennett * Jacques Derrida *
René Descartes René Descartes ( or ; ; Latinized Latinisation or Latinization can refer to: * Latinisation of names, the practice of rendering a non-Latin name in a Latin style * Latinisation in the Soviet Union, the campaign in the USSR during the 1920s ...

René Descartes
* Fyodor Dostoevsky * Maurizio Ferraris * Michel Foucault * Richard Foreman * Hans-Georg Gadamer * Merleau-Ponty * Al-Ghazali * Étienne Gilson *
Nicolai Hartmann Paul Nicolai Hartmann (; 20 February 1882 – 9 October 1950) was a Baltic German The Baltic Germans (german: Deutsch-Balten or , later ; and остзейцы ''ostzeitsy'' 'Balters' in Russian) are ethnic German inhabitants of the eastern ...
* Georg Wilhelm Friedrich Hegel * Martin Heidegger * Heraclitus of Ephesus * Jaakko Hintikka * Edmund Husserl * Roman Ingarden *
Immanuel Kant Immanuel Kant (, , ; 22 April 1724 – 12 February 1804) was a German philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about r ...

Immanuel Kant
* Leszek Kołakowski * Julia Kristeva * Susanne Langer * Louis Lavelle * Gottfried Leibniz * Douglas Lenat * Stanisław Leśniewski *
Leucippus Leucippus (; el, Λεύκιππος, ''Leúkippos''; fl. 5th century BCE) is reported in some ancient sources to have been a philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλό ...
* David Kellogg Lewis * Emmanuel Levinas * John Locke * E. J. Lowe (philosopher), E.J. Lowe * György Lukács * Madhvacharya * Alexius Meinong * Nagarjuna * Friedrich Nietzsche * Keiji Nishitani *
Parmenides Parmenides of Elea (; grc-gre, Παρμενίδης ὁ Ἐλεάτης; ) was a pre-Socratic Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Parmenides
* Charles Sanders Peirce *
Plato Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was an Classical Athens, Athenian philosopher during the Classical Greece, Classical period in Ancient Greece, founder of the Platonist school of thought and the Platoni ...

Plato
* Plotinus * Karl Popper * Proclus Lycaeus * W.V.O. Quine * Ramanujacharya * Bertrand Russell * Gilbert Ryle * Mulla Sadra * Jean-Paul Sartre * Jonathan Schaffer *
Arthur Schopenhauer Arthur Schopenhauer (; ; 22 February 1788 – 21 September 1860) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citize ...
*
Duns Scotus John Duns ( – 8 November 1308), commonly called Duns Scotus ( ; ; "Duns the Scot"), was a Scottish Catholic priest and Franciscan friar The Franciscans are a group of related Mendicant orders, mendicant Christianity, Christian Ca ...

Duns Scotus
* John Searle * Adi Shankaracharya * Theodore Sider * Peter Simons (academic), Peter Simons * Barry Smith (academic and ontologist), Barry Smith *
Baruch Spinoza Baruch (de) Spinoza (; ; ; born Baruch Espinosa; later as an author and a correspondent Benedictus de Spinoza, anglicized to Benedict de Spinoza; 24 November 1632 – 21 February 1677) was a Dutch philosopher of Spanish and Portuguese Jews, Por ...

Baruch Spinoza
* Shahab al-Din Suhrawardi * Peter van Inwagen * Achille Varzi (philosopher), Achille Varzi * Gianni Vattimo * Swami Vivekananda * Alfred North Whitehead *
William of Ockham William of Ockham (; also Occam, from la, Gulielmus Occamus; 1287 – 10 April 1347) was an English Franciscan friar The Franciscans are a group of related Mendicant orders, mendicant Christianity, Christian Catholic religious order, relig ...

William of Ockham
*
Ludwig Wittgenstein Ludwig Josef Johann Wittgenstein ( ; ; 26 April 1889 – 29 April 1951) was an Austrian Austrian may refer to: * Austrians, someone from Austria or of Austrian descent ** Someone who is considered an Austrian citizen, see Austrian nationali ...

Ludwig Wittgenstein
* Edward N. Zalta * Dean Zimmerman * Slavoj Žižek


See also

* * * * * * * * * * * * * * * * * * * * * * * * * * *


Notes


References

; Citations


External links

* * {{Authority control Ontology, Meaning (philosophy of language)