What is Ontology?

Ontology is the philosophical study of being. More broadly, it studies concepts that directly relate to Being, in particular becoming, existencereality, as well as the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology often deals with questions concerning what entities exist or may be said to exist and how such entities may be grouped, related within a hierarchy, and subdivided according to similarities and differences.


The compound word ontology (‘study of being‘) combines

onto- (Greek: ὄνongen. ὄντοςontos, ‘being’ or ‘that which is’) and
-logia (-λογία, ‘logical discourse’).

While the etymology is Greek, the oldest extant record of the word itself, the New Latin form ontologia, appeared in 1606 in the work Ogdoas Scholastica by Jacob Lorhard (Lorhardus) and in 1613 in the Lexicon philosophicum by Rudolf Göckel (Goclenius).

The first occurrence in English of ontology as recorded by the OED (Oxford English Dictionary, online edition, 2008) came in a work by Gideon Harvey (1636/7–1702): Archelogia philosophica nova; or, New principles of Philosophy. Containing Philosophy in general, Metaphysicks or Ontology, Dynamilogy or a Discourse of Power, Religio Philosophi or Natural Theology, Physicks or Natural philosophy, London, Thomson, 1663. The word was first used in its Latin form by philosophers based on the Latin roots, which themselves are based on the Greek.

Leibniz is the only one of the great philosophers of the 17th century to have used the term ontology.

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Brain and Mind


Some philosophers, notably in the traditions of the Platonic school, contend that all nouns (including abstract nouns) refer to existent entities. Other philosophers contend that nouns do not always name entities, but that some provide a kind of shorthand for reference to a collection either of objects or of events. In this latter view, mind, instead of referring to an entity, refers to a collection of mental events experienced by a personsociety refers to a collection of persons with some shared characteristics, and geometry refers to a collection of specific kinds of intellectual activities. Between these poles of realism and nominalism stand a variety of other positions.

Some fundamental questions

Principal questions of ontology include:

  • “What can be said to exist?”
  • “What is a thing?”
  • “Into what categories, if any, can we sort existing things?”
  • “What are the meanings of being?”
  • “What are the various modes of being of entities?”
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Questions Questions Questions

Various philosophers have provided different answers to these questions. One common approach involves dividing the extant subjects and predicates into groups called categories. Such lists of categories differ widely from one another, and it is through the co-ordination of different categorical schemes that ontology relates to such fields as library science and artificial intelligence. Such an understanding of ontological categories, however, is merely taxonomic, classificatory. Aristotle’s categories are the ways in which a being may be addressed simply as a being, such as:

  • what it is (its ‘whatness’, quiddity, haecceity or essence)
  • how it is (its ‘howness’ or qualitativeness)
  • how much it is (quantitativeness)
  • where it is (its relatedness to other beings)

Further examples of ontological questions include:

  • What is existence, i.e. what does it mean for a being to be?
  • Is existence a property?
  • Is existence a genus or general class that is simply divided up by specific differences?
  • Which entities, if any, are fundamental?
  • Are all entities objects?
  • How do the properties of an object relate to the object itself?
  • Do physical properties actually exist?
  • What features are the essential, as opposed to merely accidental attributes of a given object?
  • How many levels of existence or ontological levels are there? And what constitutes a “level”?
  • What is a physical object?
  • Can one give an account of what it means to say that a physical object exists?
  • Can one give an account of what it means to say that a non-physical entity exists?
  • What constitutes the identity of an object?
  • When does an object go out of existence, as opposed to merely changing?
  • Do beings exist other than in the modes of objectivity and subjectivity, i.e. is the subject/object split of modern philosophy inevitable?


Essential ontological dichotomies include:

  • universals and particulars
  • substance and accident
  • abstract and concrete objects
  • essence and existence
  • determinism and indeterminism
  • monism and dualism
  • idealism and materialism


Philosophers can classify ontologies in various ways, using criteria such as the degree of abstraction and field of application:

  1. Upper ontology: concepts supporting development of an ontology, meta-ontology
  2. Domain ontology: concepts relevant to a particular topic, domain of discourse, or area of interest, for example, to information technology or to computer languages, or to particular branches of science
  3. Interface ontology: concepts relevant to the juncture of two disciplines
  4. Process ontology: inputs, outputs, constraints, sequencing information, involved in business or engineering processes


Hindu philosophy

Ontology features in the Samkhya school of Hindu philosophy from the first millennium BCE. Samkhya philosophy regards the universe as consisting of two independent realities: puruṣa (pure, contentless consciousness) and prakṛti (matter). The substance dualism between puruṣa and prakṛti is similar but not identical to the substance dualism between mind and body that, following the works of Descartes, 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), 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). These two schools stand in contrast to Advaita Vedanta, which is committed to a strict form of monism by holding that the apparent plurality of things is an illusion (Maya) hiding the true oneness of reality at its most fundamental level (Brahman).

Parmenides and monism

Parmenides was among the first to propose an ontological characterization of the fundamental nature of reality.

Parmenides was among the first to propose an ontological characterization of the fundamental nature of reality.

In the Greek philosophical tradition, Parmenides (fl. late sixth or early fifth century BCE) was among the first to propose an ontological characterization of the fundamental nature of existence. In the prologue or proem to his poem On Nature he describes two views of existence; initially that nothing comes from nothing, and therefore existence is eternal. 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. Everything that may be apprehended is but one part of a single entity. This idea somewhat anticipates the modern concept of an ultimate grand unification theory that finally describes all of existence in terms of one inter-related sub-atomic reality which applies to everything. Most of western philosophy (especially the philosophy of Baruch Spinoza) — including the fundamental concepts of falsifiability — has emerged from this view.

Ontological pluralism

Main article: Ontological Argument

The opposite of Parmenides’ Eleatic monism is the pluralistic conception of being. In the 5th century BC, Anaxagoras and Leucippus replaced the reality of Being (unique and unchanging) with that of Becoming and therefore by a more fundamental and elementary ontic plurality. This thesis originated in the Hellenic world, 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, the atoms and their intrinsic movement in it.

The materialist atomism proposed by Leucippus was indeterminist, but Democritus (c. 460 – c. 370 BC) subsequently developed it in a deterministic way. Later (4th century BC) Epicurus took the original atomism again as indeterministic. He saw reality as composed of an infinity of indivisible, unchangeable corpuscles or atoms (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 names it clinamen) and that is determined by the chance. These ideas foreshadowed the understanding of traditional physics until the advent of 20th-century theories on the nature of atoms.




Plato (lived 420s BCE to 348/347 BCE) developed the distinction between true reality and illusion, in arguing that what is real are eternal and unchanging Forms 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, copula, or identity); and argues, against Parmenides, that Forms must exist not only of Being, but also of Negation and of non-Being (or Difference).




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:

  1. according to the various categories or ways of addressing a being as such
  2. according to its truth or falsity (e.g. fake gold, counterfeit money)
  3. whether it exists in and of itself or simply ‘comes along’ by accident
  4. according to its potency, movement (energy) or finished presence (Metaphysics Book Theta).




According to Avicenna (c. 980 – 1037), and in an interpretation of Greek Aristotelian and Platonist ontological doctrines in medieval metaphysics, being is either necessary, contingent qua possible, or impossible. Necessary being is that which cannot but be, since its non-being entails 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 is impossible for it not to be. As for the impossible, it necessarily does not exist, and the affirmation of its being is a contradiction.


Fundamental to Thomas Aquinas‘s ontology is his distinction between essence and 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.


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 asserts that every finite substance is either a thinking substance or an extended substance. This position doesn’t 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.


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 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 and Cartesian conception of categorizing them as substances. Modes compose 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.


Christian 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 science, knowable a priori and based on two fundamental principles: the principle of non-contradiction (“it cannot happen that the same thing is and is not”) and the principle of sufficient reason (“nothing exists without a sufficient reason for why it exists rather than does not exist”). Beings are defined by their determinations or predicates, which can’t involve a contradiction. Determinates come in 3 types: essentialiaattributes, 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.


Arthur Schopenhauer was a proponent of metaphysical voluntarism: he regards will as the underlying and ultimate reality. Reality as a whole consists only of one will, which is equated with the Kantian thing-in-itself. Like the Kantian thing-in-itself, the will exists outside space and time. But, unlike the Kantian thing-in-itself, the will has an experiential component to it: it comes in the form of striving, desiring, feeling, etc. The manifold of things we encounter in our everyday experiences, like trees or cars, are mere appearances that lack existence independent of the observer. Schopenhauer describes them as objectivations of the will. These objectivations happen in different “steps”, which correspond to the platonic forms. All objectivations are grounded in the will. This grounding is governed by the principium individuationis, which enables a manifold of individual things spread out in space and time to be grounded in the one will.


Edmund Husserl sees ontology as a science of essences. Sciences of essences are contrasted with factual sciences: the former are knowable a priori 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 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.


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 can be used to make this implicit understanding explicit, but it has to be accompanied by 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 early Greek thought that was covered up by later philosophers.


Nicolai Hartmann is a 20th-century philosopher within the 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 (inanimatebiologicalpsychological and spiritual) that form a hierarchy.


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 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 or 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.


The notion of ontological commitment plays a central role in Willard Van Orman Quine‘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 quantifiers, whose meaning corresponds to expressions like “there exists…” or “for some…”. They are used to 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, 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’ Globalism, Nationalism, Tribalism 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;’
  • ‘Mars, the god, does not exist;’ and
  • ‘Eliza Doolittle, in George Bernard Shaw’s 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 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 ‘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, with je pense donc je suis or cogito ergo sum or “I think, therefore I am”, argued that “the self” is something that we can know exists with 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.

Certainty about the existence of “the self” and “the other”, however, came under increasing criticism in the 20th century. Sociological theorists, most notably George Herbert Mead and Erving Goffman, saw the Cartesian Other as a “Generalized Other”, the imaginary audience that individuals use when thinking about the self. According to Mead, “we do not assume there is a self to begin with. Self is not presupposed as a stuff out of which the world arises. Rather, the self arises in the world”. The Cartesian Other was also used by Sigmund Freud, who saw the superego as an abstract regulatory force, and Émile Durkheim who viewed this as a psychologically manifested entity which represented God in society at large.

Body and environment, questioning the meaning of being

Schools of subjectivism, objectivism and relativism existed at various times in the 20th century, and the postmodernists and body philosophers tried to reframe all these questions in terms of bodies taking some specific 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 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”, 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. 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: 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. 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 partially a topic in the philosophy of language, and is not entirely about ontology itself. This viewpoint has been expressed by Eli Hirsch.

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 A.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 atoms 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 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 mechanical wave function refer?’.

Ontological argument

Main article:Ontological Argument

In the 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 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 formal argument 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 universe of discourse.

Prominent ontologists

  • Anselm of Canterbury
  • Thomas Aquinas
  • Aristotle
  • Avicenna
  • David Malet Armstrong
  • Alain Badiou
  • Gustav Bergmann
  • Roy Bhaskar
  • Bernard Bolzano
  • Franz Brentano
  • Martin Buber
  • Mario Bunge
  • Rudolf Carnap
  • Ernst Cassirer
  • Gilles Deleuze
  • Daniel Dennett
  • Jacques Derrida
  • René Descartes
  • Fyodor Dostoevsky
  • Maurizio Ferraris
  • Michel Foucault
  • Richard Foreman
  • Hans-Georg Gadamer
  • Merleau-Ponty
  • Al-Ghazali
  • Étienne Gilson
  • Nicolai Hartmann
  • Georg Wilhelm Friedrich Hegel
  • Martin Heidegger
  • Heraclitus of Ephesus
  • Jaakko Hintikka
  • Edmund Husserl
  • Roman Ingarden
  • Immanuel Kant
  • Leszek Kołakowski
  • Julia Kristeva
  • Susanne Langer
  • Louis Lavelle
  • Gottfried Leibniz
  • Douglas Lenat
  • Stanisław Leśniewski
  • Leucippus
  • David Kellogg Lewis
  • Emmanuel Levinas
  • John Locke
  • E.J. Lowe
  • György Lukács
  • Madhvacharya
  • Alexius Meinong
  • Nagarjuna
  • Friedrich Nietzsche
  • Keiji Nishitani
  • Parmenides
  • Charles Sanders Peirce
  • Plato
  • Plotinus
  • Karl Popper
  • Proclus Lycaeus
  • W.V.O. Quine
  • Ramanujacharya
  • Bertrand Russell
  • Gilbert Ryle
  • Mulla Sadra
  • Jean-Paul Sartre
  • Jonathan Schaffer
  • Arthur Schopenhauer
  • Duns Scotus
  • John Searle
  • Adi Shankaracharya
  • Theodore Sider
  • Peter Simons
  • Barry Smith
  • Baruch Spinoza
  • Shahab al-Din Suhrawardi
  • Peter van Inwagen
  • Achille Varzi
  • Gianni Vattimo
  • Swami Vivekananda
  • Alfred North Whitehead
  • William of Ockham
  • Ludwig Wittgenstein
  • Edward N. Zalta
  • Dean Zimmerman
  • Slavoj Žižek

Adapted from Wikipedia, the free encyclopedia

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