View source for Reality

{{Short description|Sum or aggregate of all that is real or existent}}
{{Distinguish|Real property{{!}}Realty}}
{{Other uses}}
{{pp-vandalism|small=yes}}
{{needs sources|date=April 2025}}
[[File:Hubble ultra deep field high rez edit1.jpg|thumb| [[Hubble Ultra-Deep Field]] image of distant galaxies illustrates the challenge of defining "reality": the light from these stars was emitted billions of years ago and many of these stars have moved, merged, or evolved since then]]
'''Reality''' is the sum or aggregate of [[everything]] in [[existence]]; everything that is not [[imagination|imaginary]]. Different [[Culture|cultures]] and [[Academic discipline|academic disciplines]] conceptualize it in various ways.

Philosophical questions about the nature of reality, existence, or being are considered under the [[rubric]] of [[ontology]], a major branch of [[metaphysics]] in the Western intellectual tradition. Ontological questions also feature in diverse branches of [[philosophy]], including the [[philosophy of science]], [[philosophy of religion|religion]], [[philosophy of mathematics|mathematics]], and [[philosophical logic|logic]]. These include questions about whether only physical objects are real (e.g., [[physicalism]]), whether reality is fundamentally immaterial (e.g., [[idealism]]), whether hypothetical unobservable entities posited by scientific theories exist (e.g., [[scientific realism]]), whether [[God]] exists, whether numbers and other [[abstract objects]] exist, and whether [[possible world]]s exist.

==Etymology and meaning==
The word ''reality'' is a borrowing from the [[Middle French]] ''realité'' and the [[Latin#Renaissance_and_Neo-Latin|post-Classical Latin]] ''realitas''. According to the ''[[Oxford English Dictionary]]'', it first appeared in English in 1513. The first definition given is "Real existence; what is real rather than imagined or desired; the aggregate of real things or existences; that which underlies and is the truth of appearances or phenomena". (A second sense, now obsolete, refers to [[real property]].)<ref>{{cite book |last1=OED staff |title=Oxford English Dictionary |publisher=Oxford University Press |url=https://www.oed.com/dictionary/reality_n?tab=meaning_and_use#26850773 |access-date=4 April 2025 |chapter=Reality (noun)}}</ref>

== Western philosophy ==
Philosophy addresses two different aspects of the topic of reality: the nature of reality itself, and the relationship between the [[mind]] (as well as [[language]] and culture) and reality.

On the one hand, [[ontology]] is the study of being, and the central topic of the field is couched, variously, in terms of being, existence, "what is", and reality. The task in ontology is to describe the most general [[category of being|categories of reality]] and how they are interrelated. If a philosopher wanted to proffer a positive definition of the concept "reality", it would be done under this heading. As explained above, some philosophers draw a distinction between reality and existence. In fact, many analytic philosophers today tend to avoid the term "real" and "reality" in discussing ontological issues. But for those who would treat "is real" the same way they treat "exists", one of the leading questions of [[analytic philosophy]] has been whether existence (or reality) is a property of objects. It has been widely held by analytic philosophers that it is ''not'' a property at all, though this view has lost some ground in recent decades.

On the other hand, particularly in discussions of [[Objectivity (philosophy)|objectivity]] that have feet in both [[metaphysics]] and epistemology, philosophical discussions of "reality" often concern the ways in which reality is, or is not, in some way ''dependent upon'' (or, to use fashionable [[jargon]], "constructed" out of) mental and cultural factors such as perceptions, beliefs, and other mental states, as well as cultural artifacts, such as religions and [[political movement]]s, on up to the vague notion of a common cultural [[world view]], or {{lang|de|[[Weltanschauung]]}}.

=== Realism ===
The view that there is a reality independent of any beliefs, perceptions, etc., is called [[Philosophical realism|realism]]. More specifically, philosophers are given to speaking about "realism ''about''" this and that, such as realism about universals or realism about the external world. Generally, where one can identify any class of object, the existence or essential characteristics of which is said not to depend on perceptions, beliefs, language, or any other human artifact, one can speak of "realism ''about''" that object.

A [[correspondence theory]] of knowledge about what exists claims that "true" knowledge of reality represents accurate correspondence of statements about and images of reality with the actual reality that the statements or images are attempting to represent. For example, the [[scientific method]] can [[Empiricism|verify]] that a statement is true based on the observable evidence that a thing exists. Many humans can point to the [[Rocky Mountains]] and say that this [[mountain range]] exists, and continues to exist even if no one is observing it or making statements about it.

===Anti-realism===
One can also speak of ''anti''-realism about the same objects. ''Anti-realism'' is the latest in a long series of terms for views opposed to realism. Perhaps the first was [[idealism (philosophy)|idealism]], so called because reality was said to be in the mind, or a product of our ''ideas''. [[Berkeleyan idealism]] is the view, propounded by the Irish [[empiricism|empiricist]] [[George Berkeley]], that the objects of perception are actually ideas in the mind. In this view, one might be tempted to say that reality is a "mental construct"; this is not quite accurate, however, since, in Berkeley's view, perceptual ideas are created and coordinated by God. By the 20th century, views similar to Berkeley's were called [[phenomenalism]]. Phenomenalism differs from Berkeleyan idealism primarily in that Berkeley believed that minds, or souls, are not merely ideas nor made up of ideas, whereas varieties of phenomenalism, such as that advocated by [[Bertrand Russell|Russell]], tended to go farther to say that the mind itself is merely a collection of perceptions, memories, etc., and that there is no mind or soul over and above such [[mental event]]s. Finally, anti-realism became a fashionable term for ''any'' view which held that the existence of some object depends upon the mind or cultural artifacts. The view that the so-called external world is really merely a social, or cultural, artifact, called [[social constructionism]], is one variety of anti-realism. [[Cultural relativism]] is the view that [[social issues]] such as morality are not absolute, but at least partially [[cultural artifact]]. Potentially the most extreme form of anti-realism is [[solipsism]] — the belief that oneself is the only thing in existence.

=== Being ===
The nature of [[being]] is a perennial topic in metaphysics. For instance, [[Parmenides]] taught that reality was a single unchanging Being, whereas [[Heraclitus]] wrote that all things flow. The 20th-century philosopher [[Heidegger]] thought previous philosophers have lost sight of the question of Being (qua Being) in favour of the questions of beings (existing things), so he believed that a return to the Parmenidean approach was needed. An [[ontological catalogue]] is an attempt to list the fundamental constituents of reality. The question of whether or not [[existence]] is a [[wikt:predicate|predicate]] has been discussed since the Early Modern period, not least in relation to the [[ontological argument for the existence of God]]. Existence, ''that'' something is, has been contrasted with ''[[essence]]'', the question of ''what'' something is.
Since existence without essence seems blank, it associated with [[nothingness]] by philosophers such as Hegel. Existential [[nihilism]] represents an extremely negative view of being, the [[absolute (philosophy)|absolute]] a positive one.

=== Perception ===
The question of [[direct realism|direct or "naïve" realism]], as opposed to [[indirect realism|indirect or "representational" realism]], arises in the [[philosophy of perception]] and [[philosophy of mind|of mind]] out of the debate over the nature of [[Consciousness|conscious]] [[Qualia|experience]];<ref name=lehar>Lehar, Steve. (2000). [http://cns-alumni.bu.edu/~slehar/webstuff/consc1/consc1.html The Function of Conscious Experience: An Analogical Paradigm of Perception and Behavior] {{Webarchive|url=https://web.archive.org/web/20151021061139/http://cns-alumni.bu.edu/~slehar/webstuff/consc1/consc1.html |date=2015-10-21 }}, ''Consciousness and Cognition''.</ref><ref name=ce>Lehar, Steve. (2000). [http://sharp.bu.edu/~slehar/epist/naive-philos.html Naïve Realism in Contemporary Philosophy] {{webarchive|url=https://web.archive.org/web/20120811172229/http://sharp.bu.edu/~slehar/epist/naive-philos.html |date=2012-08-11 }}, ''The Function of Conscious Experience''.</ref> the [[Epistemology|epistemological]] question of whether the world we see around us is the real world itself or merely an internal perceptual copy of that world generated by [[neural]] processes in our brain. [[Naïve realism]] is known as ''direct'' realism when developed to counter ''indirect'' or representative realism, also known as [[epistemological dualism]],<ref>Lehar, Steve. [http://sharp.bu.edu/~slehar/Representationalism.html Representationalism] {{webarchive|url=https://web.archive.org/web/20120905185905/http://sharp.bu.edu/~slehar/Representationalism.html |date=2012-09-05 }}</ref> the philosophical position that our conscious experience is not of the real world itself but of an internal representation, a miniature [[Virtual reality|virtual-reality]] replica of the world.

[[Timothy Leary]] coined the influential term [[Reality tunnel|Reality Tunnel]], by which he means a kind of [[representative realism]]. The theory states that, with a subconscious set of mental filters formed from their beliefs and experiences, every individual interprets the same world differently, hence "Truth is in the eye of the beholder". His ideas influenced the work of his friend [[Robert Anton Wilson]].

=== Abstract objects and mathematics ===
The status of [[Abstraction (mathematics)|abstract]] entities, particularly numbers, is a topic of discussion in mathematics.

In the philosophy of mathematics, the best known form of realism about numbers is [[Platonic realism]], which grants them abstract, immaterial existence. Other forms of realism identify mathematics with the concrete physical universe.

Anti-realist stances include [[formalism (mathematics)|formalism]] and [[mathematical fictionalism|fictionalism]].

Some approaches are selectively realistic about some mathematical objects but not others. [[Finitism]] rejects [[Infinity|infinite]] quantities. [[Ultra-finitism]] accepts finite quantities up to a certain amount. [[Constructivism (mathematics)|Constructivism]] and [[intuitionism]] are realistic about objects that can be explicitly constructed, but reject the use of the [[principle of the excluded middle]] to prove existence by [[reductio ad absurdum]].

The traditional debate has focused on whether an abstract (immaterial, intelligible) realm of numbers has existed ''in addition to'' the physical (sensible, concrete) world. A recent development is the [[mathematical universe hypothesis]], the theory that ''only'' a mathematical world exists, with the finite, physical world being an illusion within it.

An extreme form of realism about mathematics is the [[mathematical multiverse hypothesis]] advanced by [[Max Tegmark]]. Tegmark's sole postulate is: ''All structures that exist mathematically also exist physically''. That is, in the sense that "in those [worlds] complex enough to contain self-aware substructures [they] will subjectively perceive themselves as existing in a physically 'real' world".<ref name="Tegmark2008">{{cite journal|last=Tegmark |first=Max |date=February 2008 |title=The Mathematical Universe |journal=Foundations of Physics |volume=38 |issue=2 |pages=101–150 |doi=10.1007/s10701-007-9186-9 |arxiv=0704.0646|bibcode = 2008FoPh...38..101T |s2cid=9890455 }}</ref><ref>Tegmark (1998), p. 1.</ref> The hypothesis suggests that worlds corresponding to different sets of initial conditions, physical constants, or altogether different equations should be considered real. The theory can be considered a form of [[Platonism]] in that it posits the existence of mathematical entities, but can also be considered a [[philosophy of mathematics|mathematical monism]] in that it denies that anything exists except mathematical objects.

=== Properties ===
{{Main|Problem of universals}}

The problem of universals is an ancient problem in metaphysics about whether [[Universal (metaphysics)|universals]] exist. Universals are general or abstract qualities, characteristics, [[property (philosophy)|properties]], kinds or [[relation (philosophy)|relations]], such as being male/female, solid/liquid/gas or a certain colour,<ref>Loux, Michael J. (2001). "The Problem of Universals" in ''Metaphysics: Contemporary Readings'', Michael J. Loux (ed.), N.Y.: Routledge, pp.&nbsp;3–13, [4]</ref> that can be predicated of individuals or particulars or that individuals or particulars can be regarded as sharing or participating in. For example, Scott, Pat, and Chris have in common the universal quality of ''being human'' or ''humanity''.

The realist school claims that universals are real&nbsp;– they exist and are distinct from the particulars that instantiate them. There are various forms of realism. Two major forms are [[Platonic realism]] and [[Aristotelian realism]].<ref>[[H. H. Price|Price, H. H.]] (1953). "Universals and Resemblance", Ch. 1 of ''Thinking and Experience'', Hutchinson's University Library, among others, sometimes uses such Latin terms.</ref> ''Platonic realism'' is the view that universals are real entities and they exist independent of particulars. ''Aristotelian realism'', on the other hand, is the view that universals are real entities, but their existence is dependent on the particulars that exemplify them.

[[Nominalism]] and [[conceptualism]] are the main forms of anti-realism about universals.

=== Time and space ===
{{Main|Philosophy of space and time}}

A traditional realist position in ontology is that time and space have existence apart from the human mind. [[Idealism|Idealists]] deny or doubt the existence of objects independent of the mind. Some [[anti-realism|anti-realists]] whose ontological position is that objects outside the mind do exist, nevertheless doubt the independent existence of time and space.

[[Immanuel Kant|Kant]], in the ''[[Critique of Pure Reason]]'', described time as an ''[[A priori and a posteriori|a priori]]'' notion that, together with other ''a priori'' notions such as [[space]], allows us to comprehend [[empirical evidence|sense experience]]. Kant denies that either space or time are [[Substance theory|substance]], entities in themselves, or learned by experience; he holds rather that both are elements of a systematic framework we use to structure our experience. Spatial [[measurement]]s are used to [[quantity|quantify]] how far apart [[Physical body|objects]] are, and temporal measurements are used to quantitatively compare the interval between (or duration of) [[Spacetime#Basic concepts|events]]. Although space and time are held to be ''transcendentally ideal'' in this sense, they are also ''empirically real'', i.e. not mere illusions.

Idealist writers such as [[J. M. E. McTaggart]] in ''[[The Unreality of Time]]'' have argued that time is an illusion.

As well as differing about the reality of time as a whole, metaphysical theories of time can differ in their ascriptions of reality to the [[past]], present and [[future]] separately.
* [[Presentism (philosophy of time)|Presentism]] holds that the past and future are unreal, and only an ever-changing present is real.
* The [[block universe]] theory, also known as Eternalism, holds that past, present and future are all real, but the passage of time is an illusion. It is often said to have a scientific basis in [[Theory of relativity|relativity]].
* The [[growing block universe]] theory holds that past and present are real, but the future is not.

Time, and the related concepts of process and [[evolution]] are central to the [[system-building metaphysics]] of [[A. N. Whitehead]] and [[Charles Hartshorne]].

=== Possible worlds ===
{{Main|Possible world}}
The term "possible world" goes back to [[Gottfried Wilhelm Leibniz|Leibniz's]] theory of possible worlds, used to analyse necessity, [[Logical possibility|possibility]], and similar [[modal logic|modal notions]]. [[Modal realism]] is the view, notably propounded by [[David Kellogg Lewis]], that all [[possible worlds]] are as real as the actual world. In short: the actual world is regarded as merely one among an [[infinity|infinite]] [[set theory|set]] of [[logically possible]] worlds, some "nearer" to the actual world and some more remote. Other theorists may use the Possible World framework to express and explore problems without committing to it ontologically. Possible world theory is related to [[alethic modal logic]]: a proposition is ''necessary'' if it is true in all possible worlds, and ''possible'' if it is true in at least one. The [[many worlds interpretation]] of quantum mechanics is a similar idea in science.

=== Theories of everything (TOE) and philosophy ===
{{Main|Theory of everything (philosophy)}}

The philosophical implications of a physical TOE are frequently debated. For example, if philosophical [[physicalism]] is true, a physical TOE will coincide with a philosophical theory of everything.

The [[System-building metaphysics|"system building"]] style of metaphysics attempts to answer ''all'' the important questions in a coherent way, providing a complete picture of the world. [[Plato]] and [[Aristotle]] could be said to be early examples of comprehensive systems. In the early modern period (17th and 18th centuries), the system-building ''scope'' of philosophy is often linked to the rationalist ''method'' of philosophy, that is the technique of deducing the nature of the world by pure ''a priori'' reason. Examples from the early modern period include the [[Gottfried Leibniz|Leibniz]]'s [[Monadology]], [[René Descartes|Descartes]]'s [[Mind-body dualism|Dualism]], [[Baruch Spinoza|Spinoza]]'s [[Monism]]. [[Georg Wilhelm Friedrich Hegel|Hegel]]'s [[Absolute idealism]] and [[Alfred North Whitehead|Whitehead]]'s [[Process philosophy]] were later systems.

Other philosophers do not believe its techniques can aim so high. Some scientists think a more mathematical approach than philosophy is needed for a TOE, for instance [[Stephen Hawking]] wrote in ''[[A Brief History of Time]]'' that even if we had a TOE, it would necessarily be a set of equations. He wrote, "What is it that breathes fire into the equations and makes a universe for them to describe?"<ref>as quoted in [Artigas, ''The Mind of the Universe'', p.123]</ref> 

=== Phenomenology ===
On a much broader and more subjective level,{{Specify|date=August 2011}} private experiences, curiosity, inquiry, and the selectivity involved in personal interpretation of events shapes reality as seen by one and only one person<ref>"Present-time consciousness",
Francisco J. Varela,
''Journal of Consciousness Studies'' 6 (2-3):111-140 (1999)</ref> and hence is called [[Phenomenology (philosophy)|phenomenological]]. While this
form of reality might be common to others as well, it could at times also be so unique to oneself as to never be experienced or agreed upon by anyone else. Much of the kind of experience deemed [[Spirituality|spiritual]] occurs on this level of reality.<ref>
For the concept of "levels of reality", compare: {{cite book |url=https://books.google.com/books?id=TD90EAAAQBAJ |title=Levels of Reality in Science and Philosophy: Re-examining the Multi-level Structure of Reality |date=8 June 2022 |publisher=Springer Nature |isbn=9783030994259 |editor-last1=Ioannidis |editor-first1=Stavros |series=Jerusalem Studies in Philosophy and History of Science |publication-place=Cham, Zug |access-date=31 May 2024 |editor-last2=Vishne |editor-first2=Gal |editor-last3=Hemmo |editor-first3=Meir |editor-last4=Shenker |editor-first4=Orly |editor-link4=Orly Shenker}} 
</ref>

Phenomenology is a [[philosophical method]] developed in the early years of the twentieth century by [[Edmund Husserl]] (1859–1938) and a circle of followers at the universities of [[Göttingen]] and [[Munich]] in Germany. Subsequently, phenomenological themes were taken up by philosophers in France, the United States, and elsewhere, often in contexts far removed from Husserl's work.

The word ''phenomenology'' comes from the [[Greek language|Greek]] ''phainómenon'', meaning "that which appears", and ''lógos'', meaning "study". In Husserl's conception, phenomenology is primarily concerned with making the structures of consciousness, and the [[phenomena]] which appear in acts of consciousness, objects of systematic reflection and analysis. Such reflection was to take place from a highly modified "[[First-person narrative|first person]]" viewpoint, studying phenomena not as they appear to "my" consciousness, but to any consciousness whatsoever. Husserl believed that phenomenology could thus provide a firm basis for all human [[knowledge]], including [[scientific knowledge]], and could establish philosophy as a "rigorous science".<ref>{{cite book |author=Kockelmans |first=Joseph |author-link=Joseph Kockelmans |title=Edmund Husserl's phenomenology |publisher=[[Purdue University]] Press |year=2001 |isbn=1-55753-050-5 |edition=2 |pages=311–314}}</ref>

Husserl's conception of phenomenology has been criticised and developed by his student and assistant [[Martin Heidegger]] (1889–1976), by [[existentialists]] like [[Maurice Merleau-Ponty]] (1908–1961) and [[Jean-Paul Sartre]] (1905–1980), and by other philosophers, such as [[Paul Ricoeur]] (1913–2005), [[Emmanuel Levinas]] (1906–1995), and [[Dietrich von Hildebrand]] (1889–1977).<ref>{{cite book |author=Crowell |first=Steven Galt |title=Husserl, Heidegger, and the space of meaning: paths toward transcendental phenomenology |publisher=[[Northwestern University]] Press |year=2001 |isbn=0-8101-1805-X |page=160}}
</ref>

=== Skeptical hypotheses ===
[[File:braininvat.jpg|thumb|upright=1.3|A [[brain in a vat]] that believes it is walking]]
Skeptical hypotheses in philosophy suggest that reality could be very different from what we think it is; or at least that we cannot prove it is not. Examples include:
* The "[[Brain in a vat]]" hypothesis is cast in scientific terms. It supposes that one might be a disembodied brain kept alive in a vat, and fed false sensory signals. This hypothesis is related to the Matrix hypothesis below.
* The "[[Dream argument]]" of Descartes and [[Zhuang Zhou|Zhuangzi]] supposes reality to be indistinguishable from a dream.
* Descartes' [[Evil demon]] is a being "as clever and deceitful as he is powerful, who has directed his entire effort to misleading me."
* The [[five minute hypothesis]] (or [[omphalos hypothesis]] or [[Last Thursdayism]]) suggests that the world was created recently together with records and traces indicating a greater age.
* Diminished reality refers to artificially diminished reality, not due to limitations of sensory systems but via artificial [[Filter (signal processing)|filters]].<ref>{{cite journal |last1=Mori |first1=Shohei |last2=Ikeda |first2=Sei |last3=Saito |first3=Hideo |title=A survey of diminished reality: Techniques for visually concealing, eliminating, and seeing through real objects |journal=IPSJ Transactions on Computer Vision and Applications |date=28 June 2017 |volume=9 |issue=1 |pages=17 |doi=10.1186/s41074-017-0028-1 |s2cid=21053932 |issn=1882-6695|doi-access=free }}</ref>
* [[The Matrix (franchise)|The Matrix]] hypothesis or [[Simulated reality hypothesis]] suggest that we might be inside a [[computer simulation]] or [[virtual reality]]. Related hypotheses may also involve simulations with signals that allow the inhabitant species in virtual or simulated reality to perceive the external reality.

== Non-western philosophy ==
=== Hindu philosophy ===
{{Main|Vedanta}}
[[Hindu philosophy]], particularly the [[Vedic tradition]], includes a number of subtly different and nuanced perspectives about the nature of reality and [[Brahman|unified consciousness]]<ref>{{cite book |title=Shankara's Crest Jewel of Discrimination |isbn=9780874810387}}</ref>
They are as follows (order irrelevant):
# [[Advaita]] – non-dualism
# [[Tattvavada]] ([[Dvaita]]) – dualism
# [[Dvaitadvaita]] – dualistic non-dualism
# [[Bhedabheda]] – difference and non-difference
# [[Vishishtadvaita]] – qualified non-dualism
# [[Suddhadvaita]] – pure non-dualism
# [[Achintya-Bheda-Abheda]] – inconceivable difference and non-difference
# [[Dvaitadvaita Vedanta]] - natural identity-in-difference
# [[Akshar Purushottam Darshan]] - multiple eternal realities

=== Jain philosophy ===
{{Main|Tattva (Jainism)}}
[[Jain philosophy]] postulates that seven '''tattva''' (truths or fundamental principles) constitute reality.<ref>{{cite book |first=S. A. |last=Jain |title=Reality |date=1992 |publisher=Jwalamalini Trust |url=https://books.google.com/books?id=uRIaAAAAMAAJ|page=6}}</ref> These seven ''tattva'' are:<ref>{{cite book |first=S. A. |last=Jain |title=Reality |date=1992 |publisher=Jwalamalini Trust |url=https://books.google.com/books?id=uRIaAAAAMAAJ|page=7}}</ref>
# ''[[Jiva|Jīva]]'' – The [[Soul (Jainism)|soul]] which is characterized by consciousness.
# ''[[Ajiva|Ajīva]]'' – The non-soul.
# ''[[Asrava]]'' – Influx of [[Karma in Jainism|karma]].
# ''[[Bandha (Jainism)|Bandha]]'' – The bondage of karma.
# ''[[Samvara]]'' – Obstruction of the inflow of karmic matter into the soul.
# ''[[Nirjara]]'' – Shedding of karmas.
# ''[[Moksha (Jainism)|Moksha]]'' – Liberation or Salvation, i.e. the complete annihilation of all karmic matter (bound with any particular soul).

== Physical sciences ==

=== Scientific realism ===
[[Scientific realism]] is, at the most general level, the view that the world (the universe) described by science (perhaps ideal science) is the real world, as it is, independent of what we might take it to be. Within [[philosophy of science]], it is often framed as an answer to the question "how is the success of science to be explained?" The debate over what the success of science involves centers primarily on the status of entities that are [[unobservable|not directly observable]] discussed by [[scientific theory|scientific theories]]. Generally, those who are scientific realists state that one can make reliable claims about these entities (viz., that they have the same [[Ontology|ontological]] status) as directly observable entities, as opposed to [[instrumentalism]]. The most used and studied scientific theories today state more or less the truth.

=== Realism and locality in physics ===
{{main | Principle of locality}}
''Realism'' in the sense used by physicists does not equate to [[Philosophical realism|realism]] in metaphysics.<ref>{{cite journal|title=Against 'Realism'|first=Travis|last=Norsen|date=26 February 2007|journal=Foundations of Physics|volume=37|issue=3|pages=311–340|doi=10.1007/s10701-007-9104-1|arxiv=quant-ph/0607057|bibcode=2007FoPh...37..311N|s2cid=15072850}}</ref> The latter is the claim that the world is mind-independent: that even if the results of a measurement do not pre-exist the act of measurement, that does not require that they are the creation of the observer. Furthermore, a mind-independent property does not have to be the value of some physical variable such as position or [[momentum]]. A property can be ''[[disposition]]al'' (or potential), i.e. it can be a tendency: in the way that glass objects tend to break, or are disposed to break, even if they do not ''actually'' break. Likewise, the mind-independent properties of quantum systems could consist of a tendency to respond to particular measurements with particular values with ascertainable probability. Such an ontology would be metaphysically realistic, without being realistic in the physicist's sense of "local realism" (which would require that a single value be produced with certainty).

A closely related term is [[counterfactual definiteness]] (CFD), used to refer to the claim that one can meaningfully speak of the definiteness of results of measurements that have not been performed (i.e. the ability to assume the existence of objects, and properties of objects, even when they have not been measured).

[[Local realism]] is a significant feature of classical mechanics, of [[general relativity]], and of classical [[electrodynamics]]; but not [[quantum mechanics]]. In a work now called the [[EPR paradox]], Einstein relied on local realism to suggest that [[hidden variable theory| hidden variables]] were missing in quantum mechanics. However, [[John S. Bell]] subsequently showed that the predictions of quantum mechanics are inconsistent with hidden variables, a result known as [[Bell's theorem]]. The predictions of quantum mechanics have been verified: Bell's inequalities are violated. This means either particles have no definite positions independent of observation (no realism) ''or'' distant measurements can affect each other (no locality) or both. Different [[interpretation of quantum mechanics|interpretations of quantum mechanics]] violate different parts of local realism.<ref>{{cite book| last1=Nielsen |first1=Michael A. |last2=Chuang |first2=Isaac L. |year=2000 |title=Quantum Computation and Quantum Information |publisher=[[Cambridge University Press]] |pages=112–113| isbn=978-0-521-63503-5}}</ref>{{rp|117}}

The transition from "possible" to "actual" is a major topic of [[quantum physics]], with related theories including [[quantum darwinism]].

==== Role of "observation" in quantum mechanics ====
{{See also|Quantum decoherence}}
The [[quantum mind]]–body problem refers to the philosophical discussions of the [[mind–body problem]] in the context of quantum mechanics. Since quantum mechanics involves [[quantum superposition]]s, which [[Measurement in quantum mechanics|are not perceived by observers]], some [[interpretations of quantum mechanics]] place conscious observers in a special position.

The founders of quantum mechanics debated the role of the observer, and of them, [[Wolfgang Pauli]] and [[Werner Heisenberg]] believed that quantum mechanics expressed the observers knowledge and when an experiment was completed the additional knowledge should be incorporated in the wave function, an effect that came to be called state reduction or [[wave function collapse|collapse]]. This point of view, which was never fully endorsed by [[Niels Bohr]], was denounced as mystical and anti-scientific by [[Albert Einstein]]. Pauli accepted the term, and described quantum mechanics as ''lucid mysticism''.<ref>{{cite journal |author=Marin |first=Juan Miguel |year=2009 |title='Mysticism' in quantum mechanics: the forgotten controversy |journal=European Journal of Physics |volume=30 |issue=4 |pages=807–822 |bibcode=2009EJPh...30..807M |doi=10.1088/0143-0807/30/4/014 |s2cid=122757714}} [http://www.iop.org/EJ/article/0143-0807/30/4/014/ejp9_4_014.pdf?request-id=9350419a-e5ea-42e2-b5f3-7878a09dfe42 link], summarized here [http://www.physorg.com/news163670588.html%7care/]. {{webarchive|url=https://web.archive.org/web/20110606092933/http://www.physorg.com/news163670588.html%7Care/|date=2011-06-06}}.</ref>

Heisenberg and Bohr always described quantum mechanics in [[logical positivism|logical positivist]] terms. Bohr also took an active interest in the philosophical implications of quantum theories such as his [[Complementarity (physics)|complementarity]], for example.<ref>{{cite journal |author=Honner |first=John |year=2005 |title=Niels Bohr and the Mysticism of Nature |journal=Zygon: Journal of Religion & Science |volume=17-3 |pages=243–253}}</ref> He believed quantum theory offers a complete description of nature, albeit one that is simply ill-suited for everyday experiences&nbsp;– which are better described by classical mechanics and probability. Bohr famously avoided any characterization of "reality".<ref>Symposium On The Foundations Of Modern Physics 1987 - The Copenhagen Interpretation 60 Years After The Como Lecture. (1988). Singapore: World Scientific Publishing Company.</ref>{{rp|163}}

[[Eugene Wigner]] reformulated the "[[Schrödinger's cat]]" [[thought experiment]] as "[[Wigner's friend]]" and proposed that the consciousness of an observer is the demarcation line which precipitates collapse of the wave function, independent of any realist interpretation. Commonly known as "[[consciousness causes collapse]]", this controversial [[interpretation of quantum mechanics]] states that [[observation]] by a [[conscious]] observer is what makes the wave function collapse. However, this is a minority view among quantum philosophers, considering it a misunderstanding.<ref>{{cite journal |last1=Schlosshauer |first1=M. |last2=Koer |first2=J. |last3=Zeilinger |first3=A. |year=2013 |title=A Snapshot of Foundational Attitudes Toward Quantum Mechanics |journal=Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics |volume=44 |issue=3 |pages=222–230 |arxiv=1301.1069 |bibcode=2013SHPMP..44..222S |doi=10.1016/j.shpsb.2013.04.004 |s2cid=55537196}}</ref> There are other possible solutions to the "[[Wigner's friend]]" thought experiment, which do not require consciousness to be different from other physical processes. Moreover, Wigner shifted to those interpretations in his later years.<ref name="Esfeld">Michael Esfeld, (1999), [http://www.unil.ch/webdav/site/philo/shared/DocsPerso/EsfeldMichael/1999/SHPMP99.pdf Essay Review: Wigner's View of Physical Reality] {{Webarchive|url=https://web.archive.org/web/20140201151438/http://www.unil.ch/webdav/site/philo/shared/DocsPerso/EsfeldMichael/1999/SHPMP99.pdf |date=2014-02-01 }}, published in Studies in History and Philosophy of Modern Physics, 30B, pp. 145–154, Elsevier Science Limited.</ref>

=== Multiverse ===
The [[multiverse]] is the [[hypothetical]] set of multiple possible [[universe]]s (including the historical universe we consistently experience) that together comprise everything that exists: the entirety of [[space]], time, [[matter]], and energy as well as the [[physical law]]s and [[physical constant|constants]] that describe them. The term was coined in 1895 by the American philosopher and psychologist [[William James]].<ref>James, William, ''The Will to Believe'', 1895; and earlier in 1895, as cited in [[OED]]'s new 2003 entry for "multiverse": "1895 W. JAMES in Internat. Jrnl. Ethics 6 10 Visible nature is all plasticity and indifference, a multiverse, as one might call it, and not a universe."</ref> In the [[many-worlds interpretation]] (MWI), one of the mainstream [[interpretations of quantum mechanics]], there are an infinite number of universes and every possible quantum outcome occurs in at least one universe, albeit there is [[Many-worlds interpretation#Debate whether the other worlds are real|a debate as to how real the (other) worlds are]].

The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered. Multiverses have been hypothesized in [[cosmology]], physics, [[astronomy]], religion, philosophy, [[transpersonal psychology]] and fiction, particularly in science fiction and fantasy. In these contexts, parallel universes are also called "alternative universes", "quantum universes", "interpenetrating dimensions", "parallel dimensions", "parallel worlds", "alternative realities", "alternative timelines", and "dimensional planes", among others.

=== Cyclic theories ===
{{Excerpt|Multiverse#Cyclic theories}} 
Some cyclic theories postulate continuous [[expansion of the universe]] across cycles to ensure entropy growth, but they have been shown not be truly cyclic in time.<ref>{{Cite journal |last1=Kinney |first1=William H. |last2=Stein |first2=Nina K. |date=2022-06-01 |title=Cyclic cosmology and geodesic completeness |url=https://iopscience.iop.org/article/10.1088/1475-7516/2022/06/011 |journal=Journal of Cosmology and Astroparticle Physics |volume=2022 |issue=6 |pages=011 |doi=10.1088/1475-7516/2022/06/011 |issn=1475-7516|arxiv=2110.15380 |bibcode=2022JCAP...06..011K }}</ref><ref>{{cite news |last1=Cain |first1=Fraser |title=Even a Cyclical Universe Needed to Come From Somewhere |url=https://www.universetoday.com/articles/even-a-cyclical-universe-needed-to-come-from-somewhere |access-date=11 June 2025 |work=Universe Today |publisher=Self-published |date=August 11, 2022}}</ref><ref>{{cite news |last1=Hsu |first1=Charlotte |title=Do 'bouncing universes' have a beginning? |url=https://www.buffalo.edu/news/releases/2022/08/005.html |access-date=11 June 2025 |work=UB News Center |publisher=University of Buffalo |date=August 4, 2022}}</ref> In any case these types of scientific hypotheses do not fundamentally alter concepts of the ultimate origin of reality such as the [[cosmological argument]].<ref>{{cite book |author1=Reichenbach, Bruce |editor1=Zalta, Edward N. |editor2= Uri Nodelman |title=The Stanford Encyclopedia of Philosophy |date=Apr 16, 2024 |publisher=Metaphysics Research Lab, Stanford University |edition=Summer 2024 |chapter-url=https://plato.stanford.edu/archives/sum2024/entries/cosmological-argument/ |chapter = Cosmological Argument | access-date=11 June 2025}}</ref> A [[theist]] can argue for perpetual divine creation or for an [[unmoved mover]] responsible for the first universe in the sequence.<ref>{{cite book |author1=Halvorson, Hans |author2=Kragh, Helge |editor=Zalta, Edward N. |title=The Stanford Encyclopedia of Philosophy |date=Nov 16, 2021 |publisher=Metaphysics Research Lab, Stanford University |edition=Winter 2021 |chapter-url=https://plato.stanford.edu/archives/win2021/entries/cosmology-theology |chapter = Cosmology and Theology | access-date=11 June 2025}}</ref>

===Anthropic principle===
{{Excerpt|Anthropic principle|only=paragraph|files=0}}

===Personal and collective reality===
[[File:White Matter Connections Obtained with MRI Tractography.png|thumb|[[Nerve tract|White matter tracts]] within a human brain, as visualized by [[MRI]] [[tractography]]]]
Each individual has a different [[Point of view (philosophy)|view of reality]], with different memories and personal history, knowledge, personality traits and experience.<ref>{{cite journal |last1=Savin-Baden |first1=Maggi |last2=Burden |first2=David |title=Digital Immortality and Virtual Humans |journal=Postdigital Science and Education |date=1 April 2019 |volume=1 |issue=1 |pages=87–103 |doi=10.1007/s42438-018-0007-6 |s2cid=149797460 |language=en |issn=2524-4868|doi-access=free }}</ref> This system, mostly referring to the [[human brain]], affects [[cognition]] and behavior and into this complex new [[knowledge integration|knowledge]], memories,<ref>{{cite journal |last1=van Kesteren |first1=Marlieke T. R. |last2=Rignanese |first2=Paul |last3=Gianferrara |first3=Pierre G. |last4=Krabbendam |first4=Lydia |last5=Meeter |first5=Martijn |title=Congruency and reactivation aid memory integration through reinstatement of prior knowledge |journal=Scientific Reports |date=16 March 2020 |volume=10 |issue=1 |pages=4776 |doi=10.1038/s41598-020-61737-1 |pmid=32179822 |pmc=7075880 |bibcode=2020NatSR..10.4776V |language=en |issn=2045-2322}}</ref> information, [[thought]]s and experiences are continuously integrated.<ref>{{cite news |title=Understanding reality through algorithms |url=https://news.mit.edu/2022/understanding-reality-through-algorithms-fernanda-de-la-torre-0925 |access-date=6 November 2022 |work=MIT News {{!}} Massachusetts Institute of Technology |language=en |archive-date=6 November 2022 |archive-url=https://web.archive.org/web/20221106174033/https://news.mit.edu/2022/understanding-reality-through-algorithms-fernanda-de-la-torre-0925 |url-status=live }}</ref>{{additional citation needed|date=November 2022}} The [[connectome]] – [[Neuron#Connectivity|neural networks/wirings]] in brains – is thought to be a key factor in [[human variability]] in terms of cognition or the way we perceive the world (as a context) and related features or processes.<ref>{{cite web |last1=Popova |first1=Maria |title=The Connectome: A New Way To Think About What Makes You You |url=https://www.theatlantic.com/health/archive/2012/03/the-connectome-a-new-way-to-think-about-what-makes-you-you/255023/ |website=The Atlantic |access-date=6 November 2022 |date=28 March 2012 |archive-date=31 March 2012 |archive-url=https://web.archive.org/web/20120331173723/https://www.theatlantic.com/health/archive/2012/03/the-connectome-a-new-way-to-think-about-what-makes-you-you/255023/ |url-status=live }}</ref><ref>{{cite book |last1=Seung |first1=Sebastian |title=Connectome: How the Brain's Wiring Makes Us Who We Are |year=2012 |publisher=HMH |isbn=978-0547508177 |url=https://books.google.com/books?id=GXwEuoYl3wQC |language=en}}</ref><ref>{{cite news |title=Quest for the connectome: scientists investigate ways of mapping the brain |url=https://www.theguardian.com/science/2012/may/07/quest-connectome-mapping-brain |access-date=6 November 2022 |work=The Guardian |date=7 May 2012 |language=en |archive-date=6 November 2022 |archive-url=https://web.archive.org/web/20221106174032/https://www.theguardian.com/science/2012/may/07/quest-connectome-mapping-brain |url-status=live }}</ref> [[Sensemaking]] is the process by which people give [[Semantics|meaning]] to their experiences and make sense of the world they live in. [[Personal identity]] is relating to questions like how a unique individual is persisting through time.

Sensemaking and determination of reality also occurs collectively, which is investigated in [[social epistemology]] and related approaches. From the [[collective intelligence]] perspective, the intelligence of the individual human (and potentially AI entities) is substantially limited and advanced intelligence emerges when multiple entities collaborate over time.<ref>{{cite journal |last1=Peeters |first1=Marieke M. M. |last2=van Diggelen |first2=Jurriaan |last3=van den Bosch |first3=Karel |last4=Bronkhorst |first4=Adelbert |last5=Neerincx |first5=Mark A. |last6=Schraagen |first6=Jan Maarten |last7=Raaijmakers |first7=Stephan |title=Hybrid collective intelligence in a human–AI society |journal=AI & Society |date=1 March 2021 |volume=36 |issue=1 |pages=217–238 |doi=10.1007/s00146-020-01005-y |s2cid=220050285 |language=en |issn=1435-5655 |url=https://ris.utwente.nl/ws/files/205948801/Peeters_2020_Hybrid_collective_intelligence_in_a.pdf |archive-date=3 September 2023 |access-date=3 September 2023 |archive-url=https://web.archive.org/web/20230903132808/https://ris.utwente.nl/ws/files/205948801/Peeters_2020_Hybrid_collective_intelligence_in_a.pdf |url-status=dead }}</ref>{{additional citation needed|date=November 2022}} [[Collective memory]] is an important component of the social construction of reality<ref>{{cite journal |last1=Luckmann |first1=Thomas |title=On Social Interaction and the Communicative Construction of Personal Identity, Knowledge and Reality |journal=Organization Studies |date=February 2008 |volume=29 |issue=2 |pages=277–290 |doi=10.1177/0170840607087260 |s2cid=145106025 |language=en |issn=0170-8406}}</ref> and communication and communication-related systems, such as media systems, may also be major components {{see below|[[#Technology]]}}.

Philosophy of perception raises questions based on the evolutionary history of humans' perceptual apparatuses, particularly or especially individuals' [[human senses|physiological senses]], described as "[w]e don't see reality—we only see what was useful to see in the past", partly suggesting that "[o]ur species has been so successful not in spite of our inability to see reality but because of it".<ref>{{cite journal |last1=Draaisma |first1=Douwe |title=Perception: Our useful inability to see reality |journal=Nature |date=April 2017 |volume=544 |issue=7650 |pages=296 |language=en |doi=10.1038/544296a|bibcode=2017Natur.544..296D |s2cid=4400770 |doi-access=free }}</ref>

=== Scientific theories of everything ===
A [[theory of everything]] (TOE) is a putative [[theory]] of [[theoretical physics]] that fully explains and links together all known physical phenomena, and predicts the outcome of ''any'' experiment that could be carried out ''in principle''. The theory of everything is also called the '''final theory'''.<ref>Weinberg (1993)</ref> Many candidate theories of everything have been proposed by theoretical physicists during the twentieth century, but none have been confirmed experimentally. The primary problem in producing a TOE is that [[general relativity]] and quantum mechanics are hard to unify. This is one of the [[unsolved problems in physics]].

Initially, the term "theory of everything" was used with an ironic connotation to refer to various overgeneralized theories. For example, a great-grandfather of [[Ijon Tichy]], a character from a cycle of [[Stanisław Lem]]'s science fiction stories of the 1960s, was known to work on the "General Theory of Everything". Physicist [[John Ellis (physicist, born 1946)|John Ellis]]<ref>{{cite journal
 | first = John | last = Ellis
 | year = 2002
 | journal = [[Nature (journal)|Nature]]
 | title = Physics gets physical (correspondence)
 | volume = 415 | page =957
 | doi =10.1038/415957b
|bibcode = 2002Natur.415..957E
 | issue=6875
 | pmid=11875539| doi-access = free
 }}</ref> claims to have introduced the term into the technical literature in an article in ''[[Nature (magazine)|Nature]]'' in 1986.<ref>{{Cite journal
 | first = John | last = Ellis
 | year = 1986
 | journal = Nature
 | title = The Superstring: Theory of Everything, or of Nothing?
 | volume = 323 | pages = 595–598
 | doi = 10.1038/323595a0
|bibcode = 1986Natur.323..595E
 | issue=6089| s2cid = 4344940
 }}</ref> Over time, the term stuck in popularizations of [[quantum physics]] to describe a theory that would unify or explain through a single model the theories of all [[fundamental interaction]]s and of all particles of nature: general relativity for gravitation, and the [[Standard Model|standard model]] of elementary particle physics&nbsp;– which includes quantum mechanics&nbsp;– for electromagnetism, the two nuclear interactions, and the known elementary particles.

Current candidates for a theory of everything include [[string theory]], [[M theory]], and [[loop quantum gravity]].

== Technology ==
=== Media ===
{{See also|#Personal and collective reality|#Belief studies}}
Media – such as [[news media]], [[social media]], websites including [[Wikipedia]],<ref>{{cite book |last1=McDowell |first1=Zachary J. |last2=Vetter |first2=Matthew A. |title=Wikipedia and the Representation of Reality |date=2022 |url=https://library.oapen.org/handle/20.500.12657/50520 |publisher=Taylor & Francis |doi=10.4324/9781003094081 |hdl=20.500.12657/50520 |isbn=978-1003094081 |s2cid=238657838 |language=English |archive-date=2023-03-07 |access-date=2023-09-03 |archive-url=https://web.archive.org/web/20230307211432/https://library.oapen.org/handle/20.500.12657/50520 |url-status=live }}</ref> and [[fiction]]<ref name="1999-02377-025">{{cite book |last1=Prentice |first1=D. |last2=Gerrig |first2=R. |chapter=Exploring the boundary between fiction and reality |date=1999 |editor1=S. Chaiken |editor2=Y. Trope |title=Dual-process theories in social psychology |pages=529–546 |publisher=The Guilford Press. |url=https://psycnet.apa.org/record/1999-02377-025 |language=en |archive-date=2022-11-06 |access-date=2023-09-03 |archive-url=https://web.archive.org/web/20221106174032/https://psycnet.apa.org/record/1999-02377-025 |url-status=live }}</ref> – shape individuals' and society's perception of reality (including as part of belief and attitude formation)<ref name="1999-02377-025"/> and are partly used intentionally as means to [[Learning|learn]] about reality. Various technologies have changed society's relationship with reality such as the advent of radio and TV technologies.

Research investigates interrelations and effects, for example aspects in the social construction of reality.<ref>{{cite journal |last1=Gamson |first1=William A. |last2=Croteau |first2=David |last3=Hoynes |first3=William |last4=Sasson |first4=Theodore |title=Media Images and the Social Construction of Reality |journal=Annual Review of Sociology |date=1992 |volume=18 |pages=373–393 |doi=10.1146/annurev.so.18.080192.002105 |jstor=2083459 |url=https://www.jstor.org/stable/2083459 |issn=0360-0572 |archive-date=2022-11-06 |access-date=2023-09-03 |archive-url=https://web.archive.org/web/20221106175534/https://www.jstor.org/stable/2083459 |url-status=live |url-access=subscription }}</ref> A major component of this shaping and representation of perceived reality is [[Agenda-setting theory|agenda, selection and prioritization]] – not only (or primarily) the quality, tone and types of content – which influences, for instance, the public agenda.<ref>{{cite journal |last1=McCombs |first1=Maxwell E. |last2=Shaw |first2=Donald L. |title=The Agenda-Setting Function of Mass Media |journal=Public Opinion Quarterly |date=1972 |volume=36 |issue=2 |pages=176 |doi=10.1086/267990}}</ref><ref>{{cite book |last1=McCombs |first1=Maxwell |last2=Reynolds |first2=Amy |title=Media Effects |url=https://www.taylorfrancis.com/chapters/edit/10.4324/9780203877111-7/news-shapes-civic-agenda-maxwell-mccombs-amy-reynolds |chapter=How the news shapes our civic agenda and News Influence on Our Pictures of the World |year=2009 |pages=17–32 |publisher=Routledge |doi=10.4324/9780203877111-7 |isbn=978-0203877111 |archive-date=2022-11-06 |access-date=2023-09-03 |archive-url=https://web.archive.org/web/20221106174638/https://www.taylorfrancis.com/chapters/edit/10.4324/9780203877111-7/news-shapes-civic-agenda-maxwell-mccombs-amy-reynolds |url-status=live }}</ref> Disproportional news attention for low-probability incidents – such as high-consequence accidents – can distort audiences' [[risk perception]]s with harmful consequences.<ref>{{cite journal |last1=van der Meer |first1=Toni G. L. A. |last2=Kroon |first2=Anne C. |last3=Vliegenthart |first3=Rens |date=20 July 2022 |title=Do News Media Kill? How a Biased News Reality can Overshadow Real Societal Risks, The Case of Aviation and Road Traffic Accidents |journal=Social Forces |volume=101 |issue=1 |pages=506–530 |doi=10.1093/sf/soab114 |doi-access=free}}</ref> Various biases such as [[false balance]], public attention dependence reactions like [[sensationalism]] and domination by "current events",<ref>{{cite news |title=How the news took over reality |url=https://www.theguardian.com/news/2019/may/03/how-the-news-took-over-reality |access-date=6 November 2022 |work=The Guardian |date=3 May 2019 |language=en |archive-date=6 November 2022 |archive-url=https://web.archive.org/web/20221106174032/https://www.theguardian.com/news/2019/may/03/how-the-news-took-over-reality |url-status=live }}</ref> as well as various interest-driven uses of media such as marketing can also have major impacts on the perception of reality. [[Time-use research|Time-use studies]] found that e.g. in 2018 the average U.S. American "spent around eleven hours every day looking at screens".<ref>{{cite news |last1=Gorvett |first1=Zaria |title=How the news changes the way we think and behave |url=https://www.bbc.com/future/article/20200512-how-the-news-changes-the-way-we-think-and-behave |access-date=6 November 2022 |work=BBC |language=en |archive-date=6 November 2022 |archive-url=https://web.archive.org/web/20221106174032/https://www.bbc.com/future/article/20200512-how-the-news-changes-the-way-we-think-and-behave |url-status=live }}</ref>

=== Virtual reality and cyberspace ===
Virtual reality (VR) is a [[Computer simulation|computer-simulated]] environment that can simulate physical presence in places in the real world, as well as in imaginary worlds.

[[File:Virtuality continuum 2-en.svg|thumb|upright=1.6|Reality-virtuality continuum]]The [[virtuality continuum]] is a continuous scale ranging between the completely virtual, a virtuality, and the completely real: reality. The reality–virtuality continuum therefore encompasses all possible variations and compositions of real and [[Virtuality|virtual]] objects. It has been described as a concept in [[new media]] and [[computer science]], but in fact it could be considered a matter of [[anthropology]]. The concept was first introduced by Paul Milgram.<ref>{{cite conference |last1=Milgram |first1=Paul |last2=Takemura |first2=H. |last3=Utsumi |first3=A. |last4=Kishino |first4=F. |year=1994 |title=Augmented Reality: A class of displays on the reality-virtuality continuum |url=http://vered.rose.utoronto.ca/publication/1994/Milgram_Takemura_SPIE1994.pdf |conference=Telemanipulator and Telepresence Technologies |pages=2351–2434 |archive-url=https://web.archive.org/web/20061004044435/https://vered.rose.utoronto.ca/publication/1994/Milgram_Takemura_SPIE1994.pdf |archive-date=2006-10-04 |access-date=2007-03-15 |book-title=Proceedings of Telemanipulator and Telepresence Technologies |url-status=dead}}</ref>

The area between the two extremes, where both the real and the virtual are mixed, is the so-called [[mixed reality]]. This in turn is said to consist of both [[augmented reality]], where the virtual augments the real, and [[augmented virtuality]], where the real augments the virtual.
[[Cyberspace]], the world's computer systems considered as an interconnected whole, can be thought of as a virtual reality; for instance, it is portrayed as such in the [[cyberpunk]] fiction of [[William Gibson]] and others. ''[[Second Life]]'' and [[MMORPG]]s such as ''[[World of Warcraft]]'' are examples of artificial environments or [[virtual world]]s (falling some way short of full virtual reality) in cyberspace.

=== "RL" in internet culture ===
On the Internet, "[[real life]]" refers to life in the real world. It generally references [[Conditio humana|life]] or [[consensus reality]], in contrast to an environment seen as fiction or fantasy, such as virtual reality, lifelike experience, [[dream]]s, novels, or movies. Online, the [[acronym]] "IRL" stands for "in real life", with the meaning "not on the Internet".<ref>{{Cite web|url=https://www.acronymfinder.com/IRL.html|title=IRL – Definition by AcronymFinder|website=www.acronymfinder.com|access-date=2021-05-14|archive-date=2011-06-28|archive-url=https://web.archive.org/web/20110628214309/https://www.acronymfinder.com/IRL.html|url-status=live}}</ref> [[Sociologist]]s engaged in the study of the Internet have determined that someday, a distinction between online and real-life worlds may seem "quaint", noting that certain types of online activity, such as sexual intrigues, have already made a full transition to complete legitimacy and "reality".<ref name="Slater">{{cite book |author=Slater |first=Don |title=Handbook of New Media: Social Shaping and Consequences of ICTs |publisher=Sage Publications Incorporated |year=2002 |isbn=0-7619-6510-6 |editor-last=Livingstone |editor-first=Sonia |editor-link=Sonia Livingstone |pages=533–543 |chapter=Social Relationships and Identity On-line and Off-line |editor2-last=Lievrouw |editor2-first=Leah}}</ref> The [[abbreviation]] "RL" stands for "real life". For example, one can speak of "meeting in RL" someone whom one has met in a [[online chat|chat]] or on an [[Internet forum]]. It may also be used to express an inability to use the Internet for a time due to "RL problems". A related abbreviation is "AFK", which stands for "away from keyboard" <ref>{{cite web |title=Dictionary entry for 'afk'|url=https://dictionary.cambridge.org/us/dictionary/english/afk |website=Cambridge Dictionary |publisher=Cambridge University Press |access-date=11 June 2025}}</ref>, signifying that one is (at least temporarily) choosing to disengage themselves from the virtual world so as to focus preferentially on the real one. 

== World views ==
{{Further|World view}}

A common colloquial usage would have ''reality'' mean "perceptions, beliefs, and attitudes toward reality", as in "My reality is not your reality." This is often used just as a [[colloquialism]] indicating that the parties to a conversation agree, or should agree, not to quibble over deeply different conceptions of what is real. For example, in a religious discussion between friends, one might say (attempting humor), "You might disagree, but in my reality, everyone goes to heaven."

Reality can be defined in a way that links it to worldviews or parts of them (conceptual frameworks): Reality is the totality of all things, structures (actual and conceptual), events (past and present) and phenomena, whether observable or not. It is what a world view (whether it be based on individual or shared human experience) ultimately attempts to describe or map.

{{Excerpt|Worldview|hat=no|files=0}}
Certain ideas from physics, philosophy, sociology, [[literary criticism]], and other fields shape various theories of reality. One such theory is that there simply and literally ''is'' no reality beyond the perceptions or beliefs we each have about reality.<ref>{{Cite book| edition = Spring 2023| publisher = Metaphysics Research Lab, Stanford University| editor1-last = Zalta | editor1-first = Edward N.  | editor2-last = Nodelman | editor2-first = Uri | last1 = Guyer| first1 = Paul| last2 = Horstmann| first2 = Rolf-Peter| title = The Stanford Encyclopedia of Philosophy| chapter = Idealism| access-date = 2025-05-14| date = 2023| chapter-url = https://plato.stanford.edu/archives/spr2023/entries/idealism/}}</ref> Such attitudes are summarized in popular statements, such as "Perception is reality" or "Life is how you perceive reality" or "reality is what you can get away with" ([[Robert Anton Wilson]]), and they indicate [[anti-realism]]&nbsp;– that is, the view that there is no objective reality, whether acknowledged explicitly or not.

Many of the concepts of science and philosophy are often defined [[culture|culturally]] and [[sociology|socially]]. This idea was elaborated by [[Thomas Kuhn]] in his book ''[[The Structure of Scientific Revolutions]]'' (1962). ''[[The Social Construction of Reality]]'', a book about the [[sociology of knowledge]] written by [[Peter L. Berger]] and [[Thomas Luckmann]], was published in 1966. It explained how knowledge is acquired and used for the comprehension of reality. Out of all the realities, the reality of everyday life is the most important one since our consciousness requires us to be completely aware and attentive to the experience of everyday life.

== See also ==
{{cols|colwidth=26em}}
* [[Alternate history]]
* [[Consciousness]]
* [[Extended modal realism]]
* [[Fact]]
* [[Hyperreality]]
* [[Modal realism]]
* [[Potentiality and actuality]]
{{colend}}

== References ==
{{Reflist}}

== External links ==
{{Sister project links|Reality}}
* {{cite SEP |url-id=realism |title=Realism |last=Miller |first=Alexander}}
* [http://www.ditext.com/broad/reality.html C.D. Broad on Reality]
* [http://phenomenologyonline.com/ Phenomenology Online: Materials discussing and exemplifying phenomenological research]
* [http://consc.net/papers/matrix.html The Matrix as Metaphysics by David Chalmers]

{{Philosophy topics}}
{{metaphysics}}
{{World view}}
{{Spirituality-related topics}}
{{Authority control}}

[[Category:Reality| ]]
[[Category:Concepts in metaphysics]]
[[Category:Concepts in epistemology]]
[[Category:Concepts in logic]]
[[Category:Concepts in metaphilosophy]]
[[Category:Concepts in the philosophy of language]]
[[Category:Concepts in the philosophy of science]]
[[Category:Ontology]]
[[Category:Philosophy of mathematics]]
[[Category:Philosophy of religion]]
[[Category:Philosophy of technology]]
[[Category:Concepts in the philosophy of mind]]
[[Category:Concepts in social philosophy]]
[[Category:Realism]]
[[Category:Quantum measurement]]