Reality

Reality is the sum or aggregate of all that is real or existent within the universe, as opposed to that
which is only imaginary, nonexistent or nonactual. The term is also used to refer to the ontological
status of things, indicating their existence.[1] In physical terms, reality is the totality of a system, known
and unknown.[2]

Philosophical questions about the nature of reality or existence or being are considered under the rubric
of ontology, which is a major branch of metaphysics in the Western philosophical tradition. Ontological
questions also feature in diverse branches of philosophy, including the philosophy of science, of religion,
of mathematics, and philosophical logic. These include questions about whether only physical objects
are real (i.e., physicalism), whether reality is fundamentally immaterial (e.g. idealism), whether
hypothetical unobservable entities posited by scientific theories exist, whether a god or gods exist,
whether numbers and other abstract objects exist, and whether possible worlds exist. Epistemology is
concerned with what can be known or inferred as likely and how, whereby in the modern world
emphasis is put on reason, empirical evidence and science as sources and methods to determine or
investigate reality.

World views

World views and theories

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.

A worldview or a world-view or Weltanschauung is the fundamental cognitive orientation of an

individual or society encompassing the whole of the individual's or society's knowledge, culture, and
point of view.[3] A worldview can include natural philosophy; fundamental, existential, and normative
postulates; or themes, values, emotions, and ethics.[4]
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. 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 – 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 culturally and 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.

Related concepts

A priori and a posteriori

A priori ('from the earlier') and a posteriori ('from the later') are Latin phrases used in philosophy to
distinguish types of knowledge, justification, or argument by their reliance on experience. A priori
knowledge is independent from any experience. Examples include mathematics,[5] tautologies and
deduction from pure reason.[6] A posteriori knowledge depends on empirical evidence. Examples
include most fields of science and aspects of personal knowledge.

Potentiality and actuality

In philosophy, potentiality and actuality[7] are a pair of closely connected principles which Aristotle used
to analyze motion, causality, ethics, and physiology in his Physics, Metaphysics, Nicomachean Ethics,
and De Anima.[8]

The concept of potentiality, in this context, generally refers to any "possibility" that a thing can be said to
have. Aristotle did not consider all possibilities the same, and emphasized the importance of those that
become real of their own accord when conditions are right and nothing stops them.[9]

Actuality, in contrast to potentiality, is the motion, change or activity that represents an exercise or
fulfillment of a possibility, when a possibility becomes real in the fullest sense.[10] Both these concepts
therefore reflect Aristotle's belief that events in nature are not all natural in a true sense. As he saw it,
many things happen accidentally, and therefore not according to the natural purposes of things.

Belief
A belief is a subjective attitude that a proposition is true or a state of affairs is the case. A subjective
attitude is a mental state of having some stance, take, or opinion about something.[11] In epistemology,
philosophers use the term "belief" to refer to attitudes about the world which can be either true or false.
[12] To believe something is to take it to be true; for instance, to believe that snow is white is comparable

to accepting the truth of the proposition "snow is white". However, holding a belief does not require
active introspection. For example, few individuals carefully consider whether or not the sun will rise
tomorrow, simply assuming that it will. Moreover, beliefs need not be occurrent (e.g. a person actively
thinking "snow is white"), but can instead be dispositional (e.g. a person who if asked about the color of
snow would assert "snow is white").[12]

There are various ways that contemporary philosophers have tried to describe beliefs, including as
representations of ways that the world could be (Jerry Fodor), as dispositions to act as if certain things
are true (Roderick Chisholm), as interpretive schemes for making sense of someone's actions (Daniel
Dennett and Donald Davidson), or as mental states that fill a particular function (Hilary Putnam).[12]
Some have also attempted to offer significant revisions to our notion of belief, including eliminativists
about belief who argue that there is no phenomenon in the natural world which corresponds to our folk
psychological concept of belief (Paul Churchland) and formal epistemologists who aim to replace our
bivalent notion of belief ("either we have a belief or we don't have a belief") with the more permissive,
probabilistic notion of credence ("there is an entire spectrum of degrees of belief, not a simple
dichotomy between belief and non-belief").[12][13]

Beliefs are the subject of various important philosophical debates. Notable examples include: "What is
the rational way to revise one's beliefs when presented with various sorts of evidence?", "Is the content
of our beliefs entirely determined by our mental states, or do the relevant facts have any bearing on our
beliefs (e.g. if I believe that I'm holding a glass of water, is the non-mental fact that water is H2O part of
the content of that belief)?", "How fine-grained or coarse-grained are our beliefs?", and "Must it be
possible for a belief to be expressible in language, or are there non-linguistic beliefs?"[12]

Belief studies
There is research investigating specific beliefs, types of beliefs and
patterns of beliefs. For example, a study estimated contemporary
prevalence and associations with belief in witchcraft around the
world, which (in its data) varied between 9% and 90% between
nations and is still a widespread element in worldviews globally. It
also shows associations such as with lower "innovative activity",
higher levels of anxiety, lower life expectancy, and higher religiosity.
[15][14] Other research is investigating beliefs in misinformation and
their resistance to correction, including with respect to
misinformation countermeasures. It describes cognitive, social and
affective processes that leave people vulnerable to the formation of
false beliefs.[16] A study introduced the concept of false social reality Socio-demographic correlates of
which refers to widespread perceptions of public opinion that are witchcraft beliefs[14]
shown to be false, such as underestimated general public support in
the U.S. for climate change mitigation policies.[17][18] Studies also
suggested some uses of psychedelics can shift beliefs in some humans in certain ways, such as increasing
attribution of consciousness to various entities (including plants and inanimate objects) and towards
panpsychism and fatalism.[19][20]

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
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 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 movements, on up to the vague notion of a common cultural world view, or
Weltanschauung.

Realism
The view that there is a reality independent of any beliefs, perceptions, etc., is called 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 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, 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
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 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 events. 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.

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 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. Nihilism represents an
extremely negative view of being, the absolute a positive one.

Explanations for the existence of something rather than nothing

"Why is there anything at all?" or "why is there something rather than nothing?" is a question about the
reason for basic existence which has been raised or commented on by a range of philosophers and
physicists, including Gottfried Wilhelm Leibniz,[21] Ludwig Wittgenstein,[22] and Martin Heidegger,[23]
who called it "the fundamental question of metaphysics".[24][25][26]

Perception
The question of direct or "naïve" realism, as opposed to indirect or "representational" realism, arises in
the philosophy of perception and of mind out of the debate over the nature of conscious experience;[27]
[28] the 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,[29] the philosophical position that our conscious experience is not of the real
world itself but of an internal representation, a miniature virtual-reality replica of the world.

Timothy Leary coined the influential term 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 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 and fictionalism.

Some approaches are selectively realistic about some mathematical objects but not others. Finitism
rejects infinite quantities. Ultra-finitism accepts finite quantities up to a certain amount. 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".[30][31]
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
mathematical monism in that it denies that anything exists except mathematical objects.

Properties
The problem of universals is an ancient problem in metaphysics about whether universals exist.
Universals are general or abstract qualities, characteristics, properties, kinds or relations, such as being
male/female, solid/liquid/gas or a certain colour,[32] 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 – 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.[33] 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

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

Kant, in the Critique of Pure Reason, described time as an a priori notion that, together with other a
priori notions such as space, allows us to comprehend sense experience. Kant denies that either space or
time are 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 measurements are used
to quantify how far apart objects are, and temporal measurements are used to quantitatively compare
the interval between (or duration of) 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 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 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
The term "possible world" goes back to Leibniz's theory of possible worlds, used to analyse necessity,
possibility, and similar 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 infinite 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 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

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" 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 Leibniz's Monadology, Descartes's Dualism, Spinoza's Monism. Hegel's Absolute idealism
and 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?"[34]

Phenomenology
On a much broader and more subjective level, private experiences, curiosity, inquiry, and the selectivity
involved in personal interpretation of events shapes reality as seen by one and only one person[35] and
hence is called 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 spiritual occurs on this level of reality.[36]

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 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" 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".[37]

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).[38]

Skeptical hypotheses
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 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
filters[39]
▪ 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 ancient philosophy A brain in a vat that believes it is walking

and religion

Jain philosophy
Jain philosophy postulates that seven tattva (truths or fundamental principles) constitute reality.[40]
These seven tattva are:[41]

1. Jīva – The soul which is characterized by consciousness.

2. Ajīva – The non-soul.
3. Asrava – Influx of karma.
4. Bandha – The bondage of karma.
5. Samvara – Obstruction of the inflow of karmic matter into the soul.
6. Nirjara – Shedding of karmas.
7. 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 not directly observable discussed by scientific theories. Generally, those who
are scientific realists state that one can make reliable claims about these entities (viz., that they have the
same 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

Realism in the sense used by physicists does not equate to realism in metaphysics.[42] 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 dispositional (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.[43] 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 electrodynamics;
but quantum mechanics has shown that quantum entanglement is possible. This was rejected by
Einstein, who proposed the EPR paradox, but it was subsequently quantified by Bell's inequalities.[44] If
Bell's inequalities are violated, either local realism or counterfactual definiteness must be incorrect; but
some physicists dispute that experiments have demonstrated Bell's violations, on the grounds that the
sub-class of inhomogeneous Bell inequalities has not been tested or due to experimental limitations in
the tests. Different interpretations of quantum mechanics violate different parts of local realism and/or
counterfactual definiteness.

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

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 superpositions, which
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 it was the observer that produced 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.[45]

Heisenberg and Bohr always described quantum mechanics in logical positivist terms. Bohr also took an
active interest in the philosophical implications of quantum theories such as his complementarity, for
example.[46] He believed quantum theory offers a complete description of nature, albeit one that is
simply ill-suited for everyday experiences – which are better described by classical mechanics and
probability. Bohr never specified a demarcation line above which objects cease to be quantum and
become classical. He believed that it was not a question of physics, but one of philosophy.

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.[47] 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.[48]
Multiverse
The multiverse is the hypothetical set of multiple possible universes (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 laws and constants that describe them. The term was coined
in 1895 by the American philosopher and psychologist William James.[49] 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 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.

In several theories, there is a series of, in some cases infinite, self-sustaining cycles – typically a series of
Big Crunches (or Big Bounces). However, the respective universes do not exist at once but are forming
or following in a logical order or sequence, with key natural constituents potentially varying between
universes (see § Anthropic principle).

Anthropic principle
The anthropic principle, also known as the "observation selection effect",[50] is the hypothesis, first
proposed in 1957 by Robert Dicke, that the range of possible observations that could be made about the
universe is limited by the fact that observations could happen only in a universe capable of developing
intelligent life.[51] As Steven Weinberg puts it: "Where else could we be, except on a planet that can
sustain life?"[52] Proponents of the anthropic principle argue that it explains why the universe has the
age and the fundamental physical constants necessary to accommodate conscious life, since if either had
been different, no one would have been around to make observations. Anthropic reasoning is often used
to deal with the idea that the universe seems to be finely tuned for the existence of life.[53]

Personal and collective reality

Each individual has a different view of reality, with different memories and personal history, knowledge,
personality traits and experience.[54] This system, mostly referring to the human brain, affects cognition
and behavior and into this complex new knowledge, memories,[55] information, thoughts and
experiences are continuously integrated.[56] The connectome – 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.[57][58][59] Sensemaking is the process by which people give
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.[60] Collective memory is an important component
of the social construction of reality[61] and communication and communication-related systems, such as
media systems, may also be major components ().

Philosophy of perception raises questions based on the evolutionary history of humans' perceptual
apparatuses, particularly or especially individuals' 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".[62]

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.[63] 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 White matter tracts within a human
are hard to unify. This is one of the unsolved problems in physics. brain, as visualized by MRI
tractography
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[64]
claims to have introduced the term into the technical literature in an article in Nature in 1986.[65] 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 interactions and of all particles of nature:
general relativity for gravitation, and the standard model of elementary particle physics – which
includes quantum mechanics – 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
Media – such as news media, social media, websites including Wikipedia,[66] and fiction[67] – shape
individuals' and society's perception of reality (including as part of belief and attitude formation)[67] and
are partly used intentionally as means to 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.
[68] A major component of this shaping and representation of perceived reality is agenda, selection and

prioritization – not only (or primarily) the quality, tone and types of content – which influences, for
instance, the public agenda.[69][70] Disproportional news attention for low-probability incidents – such
as high-consequence accidents – can distort audiences' risk perceptions with harmful consequences.[71]
Various biases such as false balance, public attention dependence reactions like sensationalism and
domination by "current events",[72] as well as various interest-driven uses of media such as marketing
can also have major impacts on the perception of reality. Time-use studies found that e.g. in 2018 the
average U.S. American "spent around eleven hours every day looking at screens".[73]
Filter bubbles and echo chambers
A filter bubble or ideological frame is a state of intellectual isolation[74] that can result from personalized
searches, recommendation systems, and algorithmic curation. The search results are based on
information about the user, such as their location, past click-behavior, and search history.[75]
Consequently, users become separated from information that disagrees with their viewpoints, effectively
isolating them in their own cultural or ideological bubbles, resulting in a limited and customized view of
the world.[76] The choices made by these algorithms are only sometimes transparent.[77] Prime
examples include Google Personalized Search results and Facebook's personalized news-stream.
A filter bubble has been described as exacerbating a phenomenon that called splinternet or
cyberbalkanization,[78] which happens when the internet becomes divided into sub-groups of like-
minded people who become insulated within their own online community and fail to get exposure to
different views. This concern dates back to the early days of the publicly accessible internet, with the
term "cyberbalkanization" being coined in 1996.[79][80][81] Other terms have been used to describe this
phenomenon, including "ideological frames"[82] and "the figurative sphere surrounding you as you
search the internet."[83]

Virtual reality and cyberspace

Virtual reality (VR) is a computer-simulated environment that can simulate physical presence in places
in the real world, as well as in imaginary worlds.

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 Reality-virtuality continuum
possible variations and compositions of
real and 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.[84]

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 MMORPGs such as
World of Warcraft are examples of artificial environments or virtual worlds (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 life or consensus reality,
in contrast to an environment seen as fiction or fantasy, such as virtual reality, lifelike experience,
dreams, novels, or movies. Online, the acronym "IRL" stands for "in real life", with the meaning "not on
the Internet".[85] Sociologists 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".[86] The abbreviation "RL" stands for "real life". For example, one can speak of "meeting in RL"
someone whom one has met in a 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".
See also
▪ Alternate history
▪ Counterfactual history
▪ Derealization
▪ Consciousness
▪ Extended modal realism
▪ Modal realism
▪ Hyperreality

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5. Some associationist philosophers have contended that mathematics comes from experience and is
not a form of any a priori knowledge (Macleod 2016)
6. Galen Strawson has stated that an a priori argument is one in which "you can see that it is true just
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7. dynamis–energeia, translated into Latin as potentia–actualitas (earlier also possibilitas–efficacia).
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References
▪ Berger, Peter L.; Luckmann, Thomas (1966). The Social Construction of Reality: A Treatise in the
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▪ Durrant, Michael (1993). Aristotle's De Anima in Focus (https://books.google.com/books?id=3RcOA
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Further reading
▪ George Musser, "Virtual Reality: How close can physics bring us to a truly fundamental
understanding of the world?", Scientific American, vol. 321, no. 3 (September 2019), pp. 30–35.
▪ "Physics is ... the bedrock of the broader search for truth.... Yet [physicists] sometimes seem to
be struck by a collective impostor syndrome.... Truth can be elusive even in the best-established
theories. Quantum mechanics is as well tested a theory as can be, yet its interpretation remains
inscrutable. [p. 30.] The deeper physicists dive into reality, the more reality seems to evaporate."
[p. 34.]

External links
▪ Miller, Alexander. "Realism" (https://plato.stanford.edu/entries/realism/). In Zalta, Edward N. (ed.).
Stanford Encyclopedia of Philosophy.
▪ C.D. Broad on Reality (http://www.ditext.com/broad/reality.html)
▪ Phenomenology Online: Materials discussing and exemplifying phenomenological research (http://p
henomenologyonline.com/)
▪ The Matrix as Metaphysics by David Chalmers (http://consc.net/papers/matrix.html)