Editing Identity (philosophy)

{{Short description|Relation each thing bears to itself alone}}
{{Other uses of |Identity}}
{{Use dmy dates|date=May 2020}}
In [[metaphysics]], '''identity''' (from {{Langx|la|links=no|[[wiktionary:identitas|identitas]]}}, "'''sameness'''") is the [[Relations (philosophy)|relation]] each thing bears only to itself.<ref>''Stanford Encyclopedia of Philosophy'': [http://plato.stanford.edu/entries/identity/ "Identity"], First published Wed 15 Dec 2004; substantive revision Sun 1 Oct 2006.</ref><ref>{{cite book |last1=Audi |first1=Robert |title=The Cambridge Dictionary of Philosophy |publisher=Cambridge University Press |url=https://philpapers.org/rec/AUDTCD-2 |chapter=identity|year=1999 }}</ref> The notion of identity gives rise to [[List of unsolved problems in philosophy|many philosophical problems]], including the [[identity of indiscernibles]] (if ''x'' and ''y'' share all their properties, are they one and the same thing?), and questions about change and [[personal identity]] over time (what has to be the case for a person ''x'' at one time and a person ''y'' at a later time to be one and the same person?). 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'').<ref name="Sandkühler2">{{cite book |last1=Sandkühler |first1=Hans Jörg |title=Enzyklopädie Philosophie |date=2010 |publisher=Meiner |url=https://meiner.de/enzyklopadie-philosophie.html |chapter=Ontologie: 4 Aktuelle Debatten und Gesamtentwürfe |language=German |access-date=14 January 2021 |archive-date=11 March 2021 |archive-url=https://web.archive.org/web/20210311040207/https://meiner.de/enzyklopadie-philosophie.html |url-status=dead }}</ref> This article is mainly concerned with ''numerical identity'', which is the stricter notion.

The philosophical concept of identity is distinct from the better-known notion of identity in use in [[psychology]] and the [[social science]]s. The philosophical concept concerns a [[relation (logic)|''relation'']], specifically, a relation that ''x'' and ''y'' stand in [[if and only if|if, and only if]] they are one and the same thing, or ''identical to'' each other (i.e. if, and only if ''x'' = ''y'').  The [[identity (social science)|sociological notion of identity]], by contrast, has to do with a person's self-conception, social presentation, and more generally, the aspects of a person that make them unique, or qualitatively different from others (e.g. [[cultural identity]], [[gender identity]], [[national identity]], [[online identity]], and processes of [[identity formation]]). Lately, identity has been conceptualized considering humans’ position within the ecological web of life; this combination of sociocultural and ecological identification is known as ecocultural identity.<ref>{{cite book |last1=Milstein |first1=T. |last2=Castro-Sotomayor |first2=J. |editor-first1=Tema |editor-first2=José |editor-last1=Milstein |editor-last2=Castro-Sotomayor |title=Routledge Handbook of Ecocultural Identity |publisher=Routledge |location=London |doi=10.4324/9781351068840 |date=1 May 2020|isbn=9781351068840 |s2cid=229580440 |url=https://eprints.utas.edu.au/35626/1/Empathetic%20Ecocultural%20Positionality%20and%20the%20Forest%20Other%20in%20Tasmanian%20Forestry%20Conflicts.docx }}</ref>

==Metaphysics of identity==<!-- This section is linked from [[Don Quixote]] -->
{{more citations needed section|date=July 2012}}
Metaphysicians and philosophers of language and mind ask other questions:
* What does it mean for an object to be the same as itself?
* If x and y are identical (are the same thing), must they always be identical? Are they ''necessarily'' identical?
* What does it mean for an object to be the same, if it changes over time? (Is apple<SUB>''t''</SUB> the same as apple<SUB>''t''+1</SUB>?)
* If an object's parts are entirely replaced over time, as in the [[Ship of Theseus]] example, in what way is it the same?
The [[law of identity]] originates from [[classical antiquity]]. The modern formulation of identity is that of [[Gottfried Leibniz]], who held that ''x'' is the same as ''y'' [[if and only if]] every [[Predicate (logic)|predicate]] true of ''x'' is true of ''y'' as well.

Leibniz's ideas have taken root in the [[philosophy of mathematics]], where they have influenced the development of the [[predicate calculus]] as [[Identity of indiscernibles|Leibniz's law]]. Mathematicians sometimes distinguish identity from [[equality (mathematics)|equality]]. More mundanely, an ''identity'' in [[mathematics]] may be an ''[[equation]]'' that holds true for all values of a [[Variable (mathematics)|variable]]. [[Hegel]] argued that things are inherently self-contradictory<ref>{{Cite journal|last=Siemens|first=Reynold L.|date=1988|title=Hegel and the Law of Identity|url=https://www.jstor.org/stable/20128696|journal=The Review of Metaphysics|volume=42|issue=1|pages=103–127|jstor=20128696|issn=0034-6632}}</ref><ref>{{Cite journal|last=Bole|first=Thomas J.|date=1987|title=Contradiction in Hegel's "Science of Logic"|url=https://www.jstor.org/stable/20128487|journal=The Review of Metaphysics|volume=40|issue=3|pages=515–534|jstor=20128487|issn=0034-6632}}</ref> and that the notion of something being self-identical only made sense if it were not also not-identical or different from itself and did not also imply the latter. In [[Hegel]]'s words, "Identity is the identity of identity and non-identity." More recent metaphysicians have discussed [[trans-world identity]]—the notion that there can be the same object in different possible worlds. An alternative to trans-world identity is the counterpart relation in [[counterpart theory]]. It is a similarity relation that rejects trans-world individuals and instead defends an object's counterpart{{mdash}}the most similar object.

Some philosophers have denied that there is such a relation as identity. Thus [[Wittgenstein|Ludwig Wittgenstein]] writes (''[[Tractatus Logico-Philosophicus|Tractatus]]'' 5.5301): "That identity is not a relation between objects is obvious." At 5.5303 he elaborates: "Roughly speaking: to say of two things that they are identical is nonsense, and to say of one thing that it is identical with itself is to say nothing." [[Bertrand Russell]] had earlier voiced a worry that seems to be motivating Wittgenstein's point (''[[The Principles of Mathematics]]'' §64): "[I]dentity, an objector may urge, cannot be anything at all: two terms plainly are not identical, and one term cannot be, for what is it identical with?" Even before Russell, [[Frege|Gottlob Frege]], at the beginning of "[[On Sense and Reference]]," expressed a worry with regard to identity as a relation: "Equality gives rise to challenging questions which are not altogether easy to answer. Is it a relation?" More recently, [[C. J. F. Williams]]<ref>C.J.F. Williams, ''What is identity?'', Oxford University Press 1989. {{page missing|date=September 2022}}</ref> has suggested that identity should be viewed as a second-order relation, rather than a relation between objects, and [[Kai Wehmeier]]<ref>Kai F. Wehmeier, "How to live without identity—and why," ''Australasian Journal of Philosophy'' 90:4, 2012, pp. 761–777.</ref> has argued that appealing to a binary relation that every object bears to itself, and to no others, is both logically unnecessary and metaphysically suspect.

==Identity statements==
Kind-terms, or [[sortal]]s<ref>Theodore Sider. [http://tedsider.org/papers/recent_work_on_identity.pdf "Recent work on identity over time"]. ''Philosophical Books'' '''41''' (2000): 81–89.</ref> give a criterion of identity and non-identity among items of their kind.

== See also ==
* [[Counterpart theory]]
* [[Difference (philosophy)]]
* [[Similarity (philosophy)#Exact similarity and identity|Exact similarity and identity]]
* [[Four-dimensionalism]]/[[perdurantism]]
* [[Open individualism]]
* [[Teletransportation paradox]]
* [[Type–token distinction]]
* [[Vertiginous question]]

==Notes==
{{Reflist}}

==References==
* {{aut|Gallois, A.}} 1998: ''Occasions of identity''. Oxford: Oxford University Press. {{ISBN|0-19-823744-8}} [https://books.google.com/books?id=pTJDEliMcb4C Google books]
* {{aut|Parfit, D.}} 1984: ''Reasons and persons''. Oxford: Oxford University Press. {{ISBN|0-19-824908-X}} [https://books.google.com/books?id=SlgY93k936UC Google books]
* {{aut|Robinson, D.}} 1985: Can amoebae divide without multiplying? ''Australasian journal of philosophy'', '''63'''(3): 299–319. {{doi|10.1080/00048408512341901}}
* {{aut|Sidelle, A.}} 2000: [Review of {{aut|Gallois}} (1998)]. ''Philosophical review'', '''109'''(3): 469–471. [https://www.jstor.org/stable/2693711 JSTOR]
* {{aut|Sider, T.}} 2001: [Review of {{aut|Gallois}} (1998)]. ''British journal for the philosophy science'', '''52'''(2): 401–405. {{doi|10.1093/bjps/52.2.401}}

==External links==
*Stanford Encyclopedia of Philosophy: [http://plato.stanford.edu/entries/identity/ Identity], First published Wed 15 Dec 2004; substantive revision Sun 1 Oct 2006.
*Stanford Encyclopedia of Philosophy: [http://plato.stanford.edu/entries/identity-time/ Identity over time]. First published Fri 18 March 2005.
*Stanford Encyclopedia of Philosophy: [http://plato.stanford.edu/entries/identity-personal/ Personal identity]. First published Tue 20 Aug 2002; substantive revision Tue 20 Feb 2007.
*Stanford Encyclopedia of Philosophy: [http://plato.stanford.edu/entries/identity-relative/ Relative identity]. First published Mon 22 April 2002.
*[[Fernando Andacht]], Mariela Michel, ''[http://tap.sagepub.com/content/15/1/51.abstract A Semiotic Reflection on Selfinterpretation and Identity]''.

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[[Category:Identity (philosophy)| ]]
[[Category:Concepts in logic]]
[[Category:Metaphysical properties]]