Ontology Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! == History == === Ancient Greek === [[File:Parmenides.jpg|thumb|upright|[[Parmenides]] was among the first to propose an ontological characterization of the fundamental nature of reality.]] In the [[Ancient Greek philosophy|Greek philosophical tradition]], [[Parmenides]] was among the first to propose an ontological characterization of the fundamental nature of existence. In the prologue (or [[Parmenides#Introduction|''proem'']]) to ''On Nature'', he describes two views of [[existence]]. Initially, nothing comes from nothing, thus [[existence]] is [[Monism|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 may neither 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 [[Eleatics|Eleatic]] [[monism]] of [[Parmenides]] is the [[Pluralism (philosophy)|pluralistic]] conception of [[being]]. In the 5th century BCE, [[Anaxagoras]] and [[Leucippus]] replaced<ref>{{Cite book |last=Graham |first=Daniel W. |url=https://press.princeton.edu/books/hardcover/9780691125404/explaining-the-cosmos |title=Explaining the Cosmos |date=2006-08-06 |publisher=Princeton University Press |isbn=978-0-691-12540-4 |language=en}}</ref> the reality of ''being'' (unique and unchanging) with that of [[Becoming (philosophy)|''becoming'']], 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 [[Atom (order theory)|atomistic]] theory,<ref>{{cite web |url= http://plato.stanford.edu/entries/atomism-ancient/ | title= Ancient Atomism (Stanford Encyclopedia of Philosophy) | publisher= Plato.stanford.edu | access-date= 2010-02-21}}</ref> which dealt with reality as based on the [[vacuum]], the atoms and their intrinsic movement in it.<ref>Lloyd, G. E. R. (2006). Leucippus and Democritus. In D. M. Borchert (Ed.), ''Encyclopedia of philosophy'' (2nd ed., Vol. 5, pp. 297–303). Macmillan Reference USA.</ref> The materialist ''[[atomism]]'' proposed by Leucippus was [[indeterminism|indeterminist]], but [[Democritus]] ({{c.}} 460 – {{c.}} 370 BCE) subsequently developed it in a [[deterministic]] way. Later (4th century BCE), [[Epicurus]] took the original ''atomism'' again as indeterministic. He saw reality as composed of an infinity of indivisible, unchangeable corpuscles, or [[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.<ref>Aristotle, ''Metaphysics'', I, 4, p. 985.</ref> 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 [[Randomness|chance]]. These ideas foreshadowed the understanding of traditional [[physics]] until the advent of 20th-century theories on the nature of atoms.<ref> {{cite book |url=https://books.google.com/books?id=j5YEviKRlyIC |title=Contributions to Social Ontology |publisher=Routledge |year=2007 |isbn=978-1136016066 |editor1-last=Lawson |editor1-first=Clive |series=Routledge Studies in Critical Realism |location=London |publication-date=2013 |access-date=3 March 2019 |editor2-last=Latsis |editor2-first=John Spiro |editor3-last=Martins |editor3-first=Nuno}} </ref>{{page needed|date=March 2019}} [[Plato]] developed the distinction between true reality and illusion, in arguing that what is real are eternal and unchanging [[Theory of Forms|forms]] or ideas (a precursor to [[universal (metaphysics)|''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 [[Sophist (dialogue)|''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 (linguistics)|copula]], or [[identity (philosophy)|identity]]); and argues, against [[Parmenides]], that forms must exist not only of ''being'', but also of [[negation]] and of non-being (or ''difference'').{{citation needed |date= September 2017}} In his [[Categories (Aristotle)|''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:<ref>{{Cite encyclopedia |last=Studtmann |first=Paul |date=2007-09-07 |title=Aristotle's Categories |encyclopedia=Stanford Encyclopedia of Philosophy |url=https://stanford.library.sydney.edu.au/entries/aristotle-categories/#FouFolDiv}}</ref> # 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 (Aristotle)|''Metaphysics'' Book Theta]]). ===Hindu philosophy=== Ontology features in the [[Samkhya]] school of [[Hindu philosophy]] from the first millennium BCE.<ref>Larson, G.J., R.S. Bhattacharya, and K. Potter, eds. 2014. "Samkhya." pp. 3–11 in ''The Encyclopedia of Indian Philosophies'' 4. [[Princeton University Press]]. {{ISBN|978-0691604411}}.</ref> Samkhya philosophy regards the universe as consisting of two independent realities: [[puruṣa|''puruṣa'']] (pure, contentless consciousness) and [[prakṛti|''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.<ref name="Schweizer"/>{{rp|845}} 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|''buddhi'']]), and the ego ([[Ahamkara|''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.<ref>{{cite web |last=Ruzsa |first=Ferenc |title=Sankhya |url=https://iep.utm.edu/sankhya/ |website=Internet Encyclopedia of Philosophy |access-date=11 December 2020}}</ref><ref name="Schweizer">{{cite journal |last=Schweizer |first=Paul |title=Mind/Consciousness Dualism in Sankhya–Yoga Philosophy |journal=Philosophy and Phenomenological Research |date=1993 |volume=53 |issue=4 |pages=845–859 |doi=10.2307/2108256 |jstor=2108256 |url=https://philpapers.org/rec/SCHMDI}}</ref> The [[Yoga (philosophy)|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]]).<ref>[[Mikel Burley]] (2012), ''Classical Samkhya and Yoga – An Indian Metaphysics of Experience'', Routledge, {{ISBN|978-0415648875}}, pp. 39–41.</ref><ref name="lpfl">Lloyd Pflueger, ''Person Purity and Power in Yogasutra, in Theory and Practice of Yoga'' (Editor: Knut Jacobsen), Motilal Banarsidass, {{ISBN|978-8120832329}}, pp. 38–39.</ref><ref>Kovoor T. Behanan (2002), ''Yoga: Its Scientific Basis'', Dover, {{ISBN|978-0486417929}}, pp. 56–58.</ref><ref>{{cite web |last=Bryant |first=Edwin |title=Yoga Sutras of Patanjali |url=https://iep.utm.edu/yoga/ |website=Internet Encyclopedia of Philosophy |access-date=11 December 2020}}</ref> These two schools stand in contrast to [[Advaita Vedanta]], which adheres to non-duality by revealing that the apparent plurality of things is an illusion ([[Maya (Hinduism)|Maya]]) hiding the true oneness of reality at its most fundamental level ([[Brahman]]).<ref>{{cite web |last=Menon |first=Sangeetha |title=Vedanta, Advaita |url=https://iep.utm.edu/adv-veda/ |website=Internet Encyclopedia of Philosophy |access-date=11 December 2020}}</ref><ref>{{cite web |last=Ranganathan |first=Shyam |title=Hindu Philosophy |url=https://iep.utm.edu/hindu-ph/ |website=Internet Encyclopedia of Philosophy |access-date=11 December 2020}}</ref> === 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]], and [[William of Ockham]].<ref>{{cite web |last1=Gracia |first1=Jorge |last2=Newton |first2=Lloyd |title=Medieval Theories of the Categories |url=https://plato.stanford.edu/entries/medieval-categories/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=1 January 2021 |date=2016}}</ref><ref>{{cite web |last=Brower |first=Jeffrey |title=Medieval Theories of Relations |url=https://plato.stanford.edu/entries/relations-medieval/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=1 January 2021 |date=2018}}</ref><ref name="Dahlstrom"/> According to [[Avicenna]]'s 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 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.<ref> [[Nader El-Bizri]], '[[Ibn Sina]] and [[Essentialism]], Review of [[Metaphysics]], Vol. 54 (2001), pp. 753–778. </ref> Fundamental to [[Thomas Aquinas]]'s ontology is his distinction between [[essence]] and [[existence]]: all entities are conceived as composites of essence and existence.<ref name="Kerr">{{cite web |last=Kerr |first=Gaven |title=Aquinas: Metaphysics |url=https://iep.utm.edu/aq-meta/ |website=Internet Encyclopedia of Philosophy |access-date=18 December 2020}}</ref><ref>{{cite web |last=Brown |first=Christopher M. |title=Thomas Aquinas |url=https://iep.utm.edu/aquinas/ |website=Internet Encyclopedia of Philosophy |access-date=18 December 2020}}</ref><ref>{{cite web |last=Magee |first=Joseph |title=Ontology |url=https://aquinasonline.com/ontology/ |website=Thomistic Philosophy Page |access-date=18 December 2020 |language=en |date=9 February 2020}}</ref> The essence of a thing is what this thing is like, it signifies the definition of this thing.<ref>{{cite web |last=Magee |first=Joseph |title=Essence and Existence |url=https://aquinasonline.com/essence-and-existence/ |website=Thomistic Philosophy Page |access-date=18 December 2020 |language=en |date=4 February 2020}}</ref> 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.<ref>{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Aquinas, Thomas}}</ref> This distinction shows itself, for example, in our ability to understand the essence of something without knowing about its existence.<ref>{{cite book |last=Borchert |first=Donald |title=Macmillan Encyclopedia of Philosophy, 2nd Edition |date=2006 |publisher=Macmillan |url=https://philpapers.org/rec/MONMEO-3 |chapter=Thomas Aquinas, St.}}</ref> 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''.<ref name="Kerr"/> 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.<ref name="Kerr"/><ref>{{cite web |last1=McInerny |first1=Ralph |last2=O'Callaghan |first2=John |title=Saint Thomas Aquinas |url=https://plato.stanford.edu/entries/aquinas/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=18 December 2020 |date=2018}}</ref> 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.<ref name="Kerr"/> === Modern === Ontology is increasingly seen as a separate domain of philosophy in the modern period.<ref name="Dahlstrom"/><ref>{{cite book |last=Jaroszyski |first=Piotr |title=Metaphysics or Ontology? |date=2018 |publisher=Brill |url=https://philpapers.org/rec/JARMOO |chapter=Summary of Part 2}}</ref> 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]], who insisted that many claims arrived at this way are to be dismissed since they go beyond any possible experience that could justify them.<ref name="Borchert"/><ref name="Sandkühler">{{cite book |last=Sandkühler |first=Hans Jörg |title=Enzyklopädie Philosophie |date=2010 |publisher=Meiner |url=https://meiner.de/enzyklopadie-philosophie.html |chapter=Ontologie: 2 Zur Begriffs- und Problemgeschichte |access-date=2020-12-16 |archive-date=2021-03-11 |archive-url=https://web.archive.org/web/20210311040207/https://meiner.de/enzyklopadie-philosophie.html |url-status=dead }}</ref> [[René Descartes]]' ontological distinction between mind and body has been one of the most influential parts of his philosophy.<ref name="Sandkühler"/><ref name="Skirry">{{cite web |last=Skirry |first=Justin |title=Descartes, Rene: Mind-Body Distinction |url=https://iep.utm.edu/descmind/ |website=Internet Encyclopedia of Philosophy |access-date=19 December 2020}}</ref> 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''.<ref name="Smith">{{cite web |last=Smith |first=Kurt |title=Descartes' Theory of Ideas |url=https://plato.stanford.edu/entries/descartes-ideas/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |date=2018}}</ref> Modes come with a lower degree of reality since they depend for their existence on a substance.<ref>{{cite journal |last=Nelson |first=Alan |title=Introduction: Descartes's Ontology |journal=Topoi |date=1997 |volume=16 |issue=2 |pages=103–109 |doi=10.1023/A:1005877628327 |s2cid=170986842 |url=https://philpapers.org/rec/NELIDO-3}}</ref> Substances, on the other hand, can exist on their own.<ref name="Smith"/> Descartes' [[substance dualism]] asserts that every finite substance is either a thinking substance or an extended substance.<ref>{{cite journal |last=Rodriguez-Pereyra |first=Gonzalo |title=Descartes's Substance Dualism and His Independence Conception of Substance |journal=Journal of the History of Philosophy |date=2008 |volume=46 |issue=1 |pages=69–89 |doi=10.1353/hph.2008.1827 |s2cid=201736234 |url=https://philpapers.org/rec/RODDSD}}</ref><ref>{{cite web |last=Robinson |first=Howard |title=Dualism |url=https://plato.stanford.edu/entries/dualism/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |date=2020}}</ref> 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.<ref name="Skirry"/><ref>{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Descartes, René}}</ref> A longstanding problem for substance dualism since its inception has been to explain how minds and bodies can [[Problem of mental causation|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.<ref name="Skirry"/> [[Baruch Spinoza]] is well known for his ''substance monism:'' the thesis that only one substance exists.<ref name="Sandkühler"/><ref name="Dutton">{{cite web |last=Dutton |first=Blake D. |title=Spinoza, Benedict De |url=https://iep.utm.edu/spinoza/ |website=Internet Encyclopedia of Philosophy |access-date=21 December 2020}}</ref> He refers to this substance as "God or Nature", emphasizing both his [[pantheism]] and his [[Naturalism (philosophy)|naturalism]].<ref>{{cite web |last=Mander |first=William |title=Pantheism |url=https://plato.stanford.edu/entries/pantheism/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=21 December 2020 |date=2020}}</ref> This substance has an infinite amount of attributes, which he defines as "what the intellect perceives of substance as constituting its essence".<ref>{{cite web |last=Shein |first=Noa |title=Spinoza's Theory of Attributes |url=https://plato.stanford.edu/entries/spinoza-attributes/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=21 December 2020 |date=2018}}</ref> 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.<ref>{{cite book |last=Viljanen |first=Valtteri |title=The Cambridge Companion to Spinoza's Ethics |date=2009 |publisher=Cambridge University Press |url=https://philpapers.org/rec/VILSO |chapter=Spinoza's Ontology|pages=56–78 }}</ref> Spinoza sees everyday-things like rocks, cats or ourselves as mere modes and thereby opposes the traditional [[Aristotle|Aristotelian]] and [[Descartes|Cartesian]] conception of categorizing them as substances.<ref name="Waller">{{cite web |last=Waller |first=Jason |title=Spinoza, Benedict de: Metaphysics |url=https://iep.utm.edu/spinoz-m/ |website=Internet Encyclopedia of Philosophy |access-date=21 December 2020}}</ref> Modes compose [[deterministic]] systems in which the different modes are linked to each other as cause and effect.<ref name="Dutton"/> Each deterministic system corresponds to one attribute: one for extended things, one for thinking things, and so forth. Causal relations only happen within a system while the different systems run in parallel without causally interacting with each other.<ref name="Waller"/> Spinoza calls the system of modes ''Natura naturata'' ("nature natured"), and opposes it to ''Natura naturans'' ("nature naturing"), the attributes responsible for the modes.<ref>{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Spinoza, Benedict de (1632–77)}}</ref> 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.<ref name="Dutton"/> [[Christian Wolff (philosopher)|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.<ref name="Craig">{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Wolff, Christian}}</ref><ref name="Hettche">{{cite web |last1=Hettche |first1=Matt |last2=Dyck |first2=Corey |title=Christian Wolff |url=https://plato.stanford.edu/entries/wolff-christian/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=16 December 2020 |date=2019}}</ref><ref>{{cite book |last=Wolff |first=Christian |title=Preliminary Discourse on Philosophy in General |date=1963 |publisher=Indianapolis: Bobbs-Merrill |pages=45–46 |url=https://philpapers.org/rec/WOLPDO-2}}</ref> According to Wolff, it is a [[deductive]] science, knowable [[a priori|''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").<ref name="Sandkühler"/><ref name="Craig"/> ''Beings'' are defined by their ''determinations'' or ''predicates'', which cannot involve a contradiction. Determinates come in three types: ''essentialia'', ''attributes'', and ''modes''.<ref name="Craig"/> ''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.<ref name="Hettche"/> Ontology is interested in being at large, not just in actual being. But all beings, whether actually existing or not, have a sufficient reason.<ref name="Borchert">{{cite book |last=Borchert |first=Donald |title=Macmillan Encyclopedia of Philosophy, 2nd Edition |date=2006 |publisher=Macmillan |url=https://philpapers.org/rec/MONMEO-3 |chapter=Ontology, History of}}</ref> 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.<ref name="Hettche"/> [[Arthur Schopenhauer]] was a proponent of [[Voluntarism (philosophy)#Metaphysical voluntarism|metaphysical voluntarism]]:<ref>{{cite web |title=Voluntarism |url=https://www.britannica.com/topic/voluntarism-philosophy |website=Encyclopedia Britannica |access-date=21 November 2020 |language=en}}</ref> he regards will as the underlying and ultimate reality.<ref>{{cite book |last1=Ortegat |first1=P. |last2=Walker |first2=L. J. |title=New Catholic Encyclopedia Volume 14 |page=582 |url=https://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/voluntarism |chapter=Voluntarism}}</ref> 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, and so forth.<ref>{{cite web |last=Wicks |first=Robert |title=Arthur Schopenhauer |url=https://plato.stanford.edu/entries/schopenhauer/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=21 November 2020 |date=2019}}</ref><ref>{{cite book |last=Young |first=Julian |title=Schopenhauer |date=2005 |publisher=Routledge |url=https://philpapers.org/rec/YOUS |chapter=3. Metaphysics: The World as Will}}</ref> 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]].<ref>{{cite book |last=Frauenstädt |first=Julius |title=Schopenhauer-Lexikon. Ein Philosophisches Wörterbuch, Nach Arthur Schopenhauers Sämmtlichen Schriften Und Handschriftlichem Nachlass |date=1871 |publisher=F. A. Brockhaus |url=http://www.schopenhauers-kosmos.de/Objektivation |chapter=Objektivation}}</ref> All objectivations are grounded in the will. This grounding is governed by the [[principium individuationis|''principium individuationis'']], which enables a manifold of individual things spread out in space and time to be grounded in the one will.<ref name="Kastrup">{{cite book |last=Kastrup |first=Bernardo |title=Decoding Schopenhauer's Metaphysics: The Key to Understanding How It Solves the Hard Problem of Consciousness and the Paradoxes of Quantum Mechanics |publisher=John Hunt Publishing |isbn=978-1789044270 |url=https://books.google.com/books?id=-jDtDwAAQBAJ |language=en |chapter=10. Individuality and dissociation|year= 2020 }}</ref> === 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.<ref name="Dahlstrom"/><ref name="Sandkühler"/> [[Edmund Husserl]] sees ontology as a ''science of essences''.<ref name="Dahlstrom"/> ''Sciences of essences'' are contrasted with ''factual sciences'': the former are knowable [[a priori|''a priori'']] and provide the foundation for the later, which are knowable [[a posteriori|''a posteriori'']].<ref name="Sandkühler"/><ref name="Gander"/> Ontology as a science of essences is not interested in ''actual facts'', but in the essences themselves, whether they ''have instances or not''.<ref>{{cite book |last=Føllesdal |first=Dagfinn |title=A Companion to Phenomenology and Existentialism |date=2006 |publisher=John Wiley & Sons, Ltd |isbn=978-0470996508 |pages=105–114 |url=https://onlinelibrary.wiley.com/doi/10.1002/9780470996508.ch8 |language=en |chapter=Husserl's Reductions and the Role They Play in His Phenomenology|doi=10.1002/9780470996508.ch8 }}</ref> Husserl distinguishes between ''formal ontology'', which investigates the essence of ''objectivity in general'',<ref>{{cite book |last=Drummond |first=John J. |title=Historical Dictionary of Husserl's Philosophy |date=2009 |publisher=Scarecrow Press |url=https://philpapers.org/rec/DRUHDO |chapter=Formal ontology}}</ref> and ''regional ontologies'', which study ''regional essences'' that are shared by all entities belonging to the region.<ref name="Dahlstrom">{{cite book |last=Dahlstrom |first=D. O. |title=New Catholic Encyclopedia |date=2004 |publisher=Gale |url=https://www.encyclopedia.com/philosophy-and-religion/philosophy/philosophy-terms-and-concepts/ontology |chapter=Ontology}}</ref> Regions correspond to the highest [[genera]] of [[Abstract and concrete|concrete entities]]: material nature, personal consciousness, and interpersonal spirit.<ref>{{cite journal |last=Poli |first=Roberto |title=Husserl's Conception of Formal Ontology |journal=History and Philosophy of Logic |date=1993 |volume=14 |pages=1–14|doi=10.1080/01445349308837207 }}</ref><ref>{{cite book |last1=Moran |first1=Dermot |last2=Cohen |first2=Joseph |title=The Husserl Dictionary |date=2012 |publisher=Continuum |url=https://philpapers.org/rec/MORTHD |chapter=Regional ontology}}</ref> Husserl's method for studying ontology and sciences of essence in general is called [[eidetic variation]].<ref name="Gander">{{cite book |last=Gander |first=Hans-Helmuth |title=Husserl Lexikon |publisher=Wissenschaftliche Buchgesellschaft |url=https://philpapers.org/rec/GANHL |chapter=Ontologie|year=2009 }}</ref> It involves imagining an object of the kind under investigation and varying its features.<ref>{{cite book |last=Drummond |first=John J. |title=Historical Dictionary of Husserl's Philosophy |date=2009 |publisher=Scarecrow Press |url=https://philpapers.org/rec/DRUHDO |chapter=Eidetic variation}}</ref> 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.<ref>{{cite web |last=Spear |first=Andrew D. |title=Husserl, Edmund: Intentionality and Intentional Content |url=https://iep.utm.edu/huss-int/ |website=Internet Encyclopedia of Philosophy |access-date=22 December 2020}}</ref> Central to [[Martin Heidegger]]'s philosophy is the notion of ''ontological difference'': the difference between ''being'' as such and specific entities.<ref name="Wheeler">{{cite web |last=Wheeler |first=Michael |title=Martin Heidegger |url=https://plato.stanford.edu/entries/heidegger/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |date=2020}}</ref><ref>{{cite book |last=Schalow |first=Frank |title=Historical Dictionary of Heidegger's Philosophy |date=2010 |publisher=Scarecrow Press |url=https://philpapers.org/rec/SCHHDO-2 |chapter=Ontological difference}}</ref> 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".<ref name="Dahlstrom"/><ref name="Wheeler"/><ref name="Korab-Karpowicz">{{cite web |last=Korab-Karpowicz |first=W. J. |title=Heidegger, Martin |url=https://iep.utm.edu/heidegge/ |website=Internet Encyclopedia of Philosophy}}</ref> 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]].<ref>{{cite book |last=Inwood |first=Michael |title=A Heidegger Dictionary |date=1999 |publisher=Wiley-Blackwell |url=https://philpapers.org/rec/INWAHD-3 |chapter=Ontology and fundamental ontology}}</ref><ref>{{cite journal |last=Inwagen |first=Peter Van |title=Meta-Ontology |journal=Erkenntnis |date=1998 |volume=48 |issue=2–3 |pages=233–250 |doi=10.1023/A:1005323618026 |s2cid=267942448 |url=https://philpapers.org/rec/VANM-3}}</ref> One method to achieve this is by studying the human being, or [[Dasein]], in Heidegger's terminology.<ref name="Sandkühler"/> 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''.<ref name="Wheeler"/> 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''.<ref>{{cite book |last=Inwood |first=Michael |title=A Heidegger Dictionary |date=1999 |publisher=Wiley-Blackwell |url=https://philpapers.org/rec/INWAHD-3 |chapter=History of being}}</ref> 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.<ref name="Korab-Karpowicz"/> [[Nicolai Hartmann]] 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.<ref>{{cite book |last=Hartmann |first=Nicolai |title=Zur Grundlegung der Ontologie |date=1935 |publisher=W. De Gruyter |url=https://philpapers.org/rec/HARZGD-4 |chapter=1. Kapitel. Die ontologische Grundfrage}}</ref><ref>{{cite book |author=Aristotle |last2=Reeve |first2=C. D. C. |title=Metaphysics |publisher=Hackett Publishing |isbn=978-1624664410 |url=https://books.google.com/books?id=prGgCwAAQBAJ |language=en |chapter=Book Epsilon|year=2016 }}</ref><ref>{{cite book |last=Spiegelberg |first=Herbert |title=The Phenomenological Movement a Historical Introduction |date=1963 |publisher=M. Nijhoff |pages=309–310 |edition=3rd |url=https://philpapers.org/rec/SPITPM-6}}</ref> 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''.<ref>{{cite book |last=Hartmann |first=Nicolai |title=Zur Grundlegung der Ontologie |date=1935 |publisher=W. De Gruyter |url=https://philpapers.org/rec/HARZGD-4 |chapter=12. Kapitel. Die Trennung von Dasein und Sosein}}</ref> ''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.<ref name="Cicovacki">{{cite book |last=Cicovacki |first=Predrag |title=The Analysis of Wonder: An Introduction to the Philosophy of Nicolai Hartmann |date=2014 |publisher=Bloomsbury Publishing US |isbn=978-1623569747 |url=https://books.google.com/books?id=IXnHAgAAQBAJ |language=en |chapter=I.3 Modifications of Being}}</ref> Among the ideal entities are mathematical objects and values.<ref>{{cite book |last=Mohanty |first=J. N. |title=Phenomenology. Between Essentialism and Transcendental Philosophy |date=1997 |publisher=Northwestern University Press |chapter=Chapter 3: Nicolai Hartmann's Phenomenological Ontology}}</ref> 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 [[Integrative level|levels]] (''inanimate'', ''biological'', ''psychological'', and ''spiritual'') that form a hierarchy.<ref name="Poli"/><ref name="Hartmann"/> [[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.<ref name="Hofweber"/><ref name="Dahlstrom"/> 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.<ref name="Leitgeb"/> The problem Carnap saw with traditional ontologists is that they try to make framework-independent or ''external'' statements about what ''really'' is the case.<ref name="Sandkühler"/><ref>{{cite web |last1=Leitgeb |first1=Hannes |last2=Carus |first2=André |title=Rudolf Carnap > H. Tolerance, Metaphysics, and Meta-Ontology (Stanford Encyclopedia of Philosophy |url=https://plato.stanford.edu/entries/carnap/tolerance-metaphysics.html |website=The Stanford Encyclopedia of Philosophy}}</ref> Such statements are at best ''pragmatic considerations'' about which framework to choose, and at worst outright ''meaningless'', according to Carnap.<ref>{{cite web |last=Murzi |first=Mauro |title=Carnap, Rudolf |url=https://iep.utm.edu/carnap/ |website=Internet Encyclopedia of Philosophy |access-date=23 December 2020}}</ref> For example, there is no matter of fact as to whether [[Realism (philosophical)|realism]] or [[idealism]] is true: their truth depends on the adopted framework.<ref>{{cite book |last1=Blatti |first1=Stephan |last2=Lapointe |first2=Sandra |title=Ontology After Carnap |publisher=Oxford University Press UK |url=https://philpapers.org/rec/SANOAC-5 |chapter=Introduction|year=2016 }}</ref> The job of philosophers is not to discover which things exist by themselves but is a kind of "conceptual engineering" to create interesting frameworks and to explore the consequences of adopting them.<ref name="Hofweber"/><ref name="Leitgeb">{{cite web |last1=Leitgeb |first1=Hannes |last2=Carus |first2=André |title=Rudolf Carnap |url=https://plato.stanford.edu/entries/carnap/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=23 December 2020 |date=2020}}</ref> Since there is no framework-independent notion of truth, the choice of framework is guided by practical considerations like expedience or fruitfulness .<ref>{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Carnap, Rudolf}}</ref> The notion of [[ontological commitment]] plays a central role in [[Willard Van Orman Quine]]'s contributions to ontology.<ref>{{cite book |last=Craig |first=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Ontological commitment}}</ref><ref>{{cite web |title=Ontology |url=https://www.britannica.com/topic/ontology-metaphysics |website=Encyclopedia Britannica |access-date=13 December 2020 |language=en}}</ref> A theory is ontologically committed to an entity if that entity must exist in order for the theory to be true.<ref name="Bricker">{{cite web |last=Bricker |first=Phillip |title=Ontological Commitment |url=https://plato.stanford.edu/entries/ontological-commitment/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=13 December 2020 |date=2016}}</ref> 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.<ref>{{cite book |last1=Magnus |first1=P. D. |last2=Ichikawa |first2=Jonathan Jenkins |title=Forall X |date=2020 |publisher=Creative Commons: Attribution-ShareAlike 3.0 |url=https://philpapers.org/rec/MAGFXU |chapter=V. First-order logic|edition=UBC }}</ref> The ontological commitments of the theory then correspond to the variables bound by existential quantifiers.<ref>{{cite book |last=Schaffer |first=Jonathan |title=Metametaphysics: New Essays on the Foundations of Ontology |publisher=Oxford University Press |pages=347–383 |url=https://philpapers.org/rec/SCHOWG |chapter=On What Grounds What|year=2009 }}</ref> This approach is summed up by Quine's famous dictum that "[t]o be is to be the value of a variable".<ref name="Quine">{{cite journal |last=Quine |first=Willard Van Orman |title=On What There Is |journal=Review of Metaphysics |date=1948 |volume=2 |issue=5 |pages=21–38 |url=https://philpapers.org/rec/QUIOWT-7}}</ref> 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.<ref name="Bricker"/> Various followers of Quine's method chose to apply it to different fields, for example to "everyday conceptions expressed in natural language".<ref>{{cite book |last=Inwagen |first=Peter van |title=Oxford Studies in Metaphysics, Volume 1 |date=2004 |publisher=Clarendon Press |pages=107–138 |url=https://philpapers.org/rec/VANATO-2 |chapter=A Theory of Properties}}</ref><ref>{{cite book |last=Kapelner |first=Zsolt-kristof |title=Reconciling Quinean and neo-Aristotelian Metaontology |date=2015 |url=http://www.etd.ceu.hu/2015/kapelner_zsolt-kristof.pdf |chapter=3. Quinean Metaontology}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. 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