Philosophical realism

Philosophical realism

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Contemporary philosophical realism is the belief that our reality
Reality
In philosophy, reality is the state of things as they actually exist, rather than as they may appear or might be imagined. In a wider definition, reality includes everything that is and has been, whether or not it is observable or comprehensible...

, or some aspect of it, is ontologically
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

 independent of our conceptual schemes, linguistic practices, beliefs, etc.
Realism may be spoken of with respect to other minds, the past
Past
Most generally, the past is a term used to indicate the totality of events which occurred before a given point in time. The past is contrasted with and defined by the present and the future. The concept of the past is derived from the linear fashion in which human observers experience time, and is...

, the future
Future
The future is the indefinite time period after the present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the nature of the reality and the unavoidability of the future, everything that currently exists and will exist is temporary and will come...

, universals
Universal (metaphysics)
In metaphysics, a universal is what particular things have in common, namely characteristics or qualities. In other words, universals are repeatable or recurrent entities that can be instantiated or exemplified by many particular things. For example, suppose there are two chairs in a room, each of...

, mathematical entities
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

 (such as natural numbers), moral categories
Morality
Morality is the differentiation among intentions, decisions, and actions between those that are good and bad . A moral code is a system of morality and a moral is any one practice or teaching within a moral code...

, the material world
Material world
Material world may refer to:* Nature.* Material World, a Canadian television sitcom in the 1980s.* Material World, a BBC Radio 4 science programme.* Material World: A Global Family Portrait, a 1994 photo essay by Peter Menzel....

, or even thought
Thought
"Thought" generally refers to any mental or intellectual activity involving an individual's subjective consciousness. It can refer either to the act of thinking or the resulting ideas or arrangements of ideas. Similar concepts include cognition, sentience, consciousness, and imagination...

.
Realism can also be promoted in an unqualified sense, in which case it asserts the mind-independent existence of a visible world, as opposed to idealism
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

, skepticism
Skepticism
Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere...

 and solipsism
Solipsism
Solipsism is the philosophical idea that only one's own mind is sure to exist. The term comes from Latin solus and ipse . Solipsism as an epistemological position holds that knowledge of anything outside one's own mind is unsure. The external world and other minds cannot be known, and might not...

.
Philosophers who profess realism state that truth
Truth
Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

 consists in the mind's correspondence
Correspondence theory of truth
The correspondence theory of truth states that the truth or falsity of a statement is determined only by how it relates to the world, and whether it accurately describes that world...

 to reality.

Realists tend to believe that whatever we believe now is only an approximation of reality and that every new observation brings us closer to understanding reality. In its Kantian sense, realism is contrasted with idealism
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

. In a contemporary sense, realism is contrasted with anti-realism
Anti-realism
In analytic philosophy, the term anti-realism is used to describe any position involving either the denial of an objective reality of entities of a certain type or the denial that verification-transcendent statements about a type of entity are either true or false...

, primarily in the philosophy of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

.

History


The oldest use of the term "realism" appears in medieval
Medieval philosophy
Medieval philosophy is the philosophy in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Western Roman Empire in the fifth century AD to the Renaissance in the sixteenth century...

 scholastic
Scholasticism
Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...

 interpretations and adaptations of Greek philosophy
Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...

. Here, however, it is a Platonic realism
Platonic realism
Platonic realism is a philosophical term usually used to refer to the idea of realism regarding the existence of universals or abstract objects after the Greek philosopher Plato , a student of Socrates. As universals were considered by Plato to be ideal forms, this stance is confusingly also called...

 developed out of debates over the problem of universals
Problem of universals
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, that can be predicated of individuals or...

. Universals
Universal (metaphysics)
In metaphysics, a universal is what particular things have in common, namely characteristics or qualities. In other words, universals are repeatable or recurrent entities that can be instantiated or exemplified by many particular things. For example, suppose there are two chairs in a room, each of...

 are terms or properties that can be applied to many things, such as "red", "beauty", "five", or "dog". Realism in this context, contrasted with conceptualism
Conceptualism
Conceptualism is a philosophical theory that explains universality of particulars as conceptualized frameworks situated within the thinking mind. Intermediate between Nominalism and Realism, the conceptualist view approaches the metaphysical concept of universals from a perspective that denies...

 and nominalism
Nominalism
Nominalism is a metaphysical view in philosophy according to which general or abstract terms and predicates exist, while universals or abstract objects, which are sometimes thought to correspond to these terms, do not exist. Thus, there are at least two main versions of nominalism...

, holds that such universals really exist, independently and somehow prior to the world. Moderate Realism holds that they exist, but only insofar as they are instantiated in specific things; they do not exist separately from the specific thing. Conceptualism holds that they exist, but only in the mind, while nominalism holds that universals do not "exist" at all but are no more than words (flatus voci) that describe specific objects.

Platonic realism


Platonic realism
Platonic realism
Platonic realism is a philosophical term usually used to refer to the idea of realism regarding the existence of universals or abstract objects after the Greek philosopher Plato , a student of Socrates. As universals were considered by Plato to be ideal forms, this stance is confusingly also called...

 is a philosophical
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 term usually used to refer to the idea of realism regarding the existence of universals or abstract object
Abstract object
An abstract object is an object which does not exist at any particular time or place, but rather exists as a type of thing . In philosophy, an important distinction is whether an object is considered abstract or concrete. Abstract objects are sometimes called abstracta An abstract object is an...

s after the Greek
Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...

 philosopher Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 (c. 427
427 BC
Year 427 BC was a year of the pre-Julian Roman calendar. At the time, it was known as the Year of the Consulship of Ahala and Mugillanus...

–c. 347 BC
347 BC
Year 347 BC was a year of the pre-Julian Roman calendar. At the time it was known as the Year of the Consulship of Venno and Torquatus...

), a student of Socrates
Socrates
Socrates was a classical Greek Athenian philosopher. Credited as one of the founders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary ...

. As universals were considered by Plato to be ideal forms
Theory of Forms
Plato's theory of Forms or theory of Ideas asserts that non-material abstract forms , and not the material world of change known to us through sensation, possess the highest and most fundamental kind of reality. When used in this sense, the word form is often capitalized...

, this stance is confusingly also called Platonic idealism
Platonic idealism
Platonic idealism usually refers to Plato's theory of forms or doctrine of ideas,Some commentators hold Plato argued that truth is an abstraction...

. This should not be confused with Idealism, as presented by philosophers such as George Berkeley
George Berkeley
George Berkeley , also known as Bishop Berkeley , was an Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism"...

: as Platonic abstraction
Abstraction
Abstraction is a process by which higher concepts are derived from the usage and classification of literal concepts, first principles, or other methods....

s are not spacial, temporal, or mental they are not compatible with the later Idealism's emphasis on mental existence. Plato's Forms include numbers and geometrical figures, making them a theory of mathematical realism; they also include the Form of the Good, making them in addition a theory of ethical realism.

The Scottish School of Common Sense Realism


Scottish Common Sense Realism is a school of philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 that sought to defend naive realism against philosophical paradox and scepticism, arguing that matters of common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...

 are within the reach of common understanding and that common-sense beliefs even govern the lives and thoughts of those who hold non-commonsensical beliefs. It originated in the ideas of the most prominent members of the Scottish School of Common Sense, Thomas Reid
Thomas Reid
The Reverend Thomas Reid FRSE , was a religiously trained Scottish philosopher, and a contemporary of David Hume, was the founder of the Scottish School of Common Sense, and played an integral role in the Scottish Enlightenment...

, Adam Ferguson
Adam Ferguson
Adam Ferguson FRSE, also known as Ferguson of Raith was a Scottish philosopher, social scientist and historian of the Scottish Enlightenment...

 and Dugald Stewart
Dugald Stewart
Dugald Stewart was a Scottish Enlightenment philosopher and mathematician. His father, Matthew Stewart , was professor of mathematics in the University of Edinburgh .-Life and works:...

, during the 18th century Scottish Enlightenment
Scottish Enlightenment
The Scottish Enlightenment was the period in 18th century Scotland characterised by an outpouring of intellectual and scientific accomplishments. By 1750, Scots were among the most literate citizens of Europe, with an estimated 75% level of literacy...

 and flourished in the late 18th and early 19th centuries in Scotland and America.

Its roots can be found in responses to such philosophers as John Locke
John Locke
John Locke FRS , widely known as the Father of Liberalism, was an English philosopher and physician regarded as one of the most influential of Enlightenment thinkers. Considered one of the first of the British empiricists, following the tradition of Francis Bacon, he is equally important to social...

, George Berkeley
George Berkeley
George Berkeley , also known as Bishop Berkeley , was an Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism"...

 and David Hume
David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...

. The approach was a response to the "ideal system" that began with Descartes' concept of the limitations of sense experience and led Locke and Hume to a skepticism that called religion and the evidence of the senses equally into question. The common sense realists found skepticism to be absurd and so contrary to common experience that it had to be rejected. They taught that ordinary experiences provide intuitively certain assurance of the existence of the self, of real objects that could be seen and felt and of certain "first principles" upon which sound morality and religious beliefs could be established. Its basic principle was enunciated by its founder and greatest figure, Thomas Reid:
"If there are certain principles, as I think there are, which the constitution of our nature leads us to believe, and which we are under a necessity to take for granted in the common concerns of life, without being able to give a reason for them--these are what we call the principles of common sense; and what is manifestly contrary to them, is what we call absurd.".


Common sense realists tend to oppose indirect realism and representationalism, which they see as leading to skepticism.

Naive realism


Naïve realism
Naïve realism
Naïve realism, also known as direct realism or common sense realism, is a philosophy of mind rooted in a common sense theory of perception that claims that the senses provide us with direct awareness of the external world...

, also known as direct realism is a philosophy of mind
Philosophy of mind
Philosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness and their relationship to the physical body, particularly the brain. The mind-body problem, i.e...

 rooted in a common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...

 theory
Theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...

 of perception
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

 that claims that the senses provide us with direct awareness
Awareness
Awareness is the state or ability to perceive, to feel, or to be conscious of events, objects or sensory patterns. In this level of consciousness, sense data can be confirmed by an observer without necessarily implying understanding. More broadly, it is the state or quality of being aware of...

 of the external world. In contrast, some forms of idealism
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

 assert that no world exists apart from mind-dependent ideas and some forms of skepticism
Skepticism
Skepticism has many definitions, but generally refers to any questioning attitude towards knowledge, facts, or opinions/beliefs stated as facts, or doubt regarding claims that are taken for granted elsewhere...

 say we cannot trust our senses. The realist view is that object
Object (philosophy)
An object in philosophy is a technical term often used in contrast to the term subject. Consciousness is a state of cognition that includes the subject, which can never be doubted as only it can be the one who doubts, and some object or objects that may or may not have real existence without...

s are composed of matter
Matter
Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...

, occupy space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...

 and have properties, such as size, shape, texture, smell, taste and colour, that are usually perceived
Perception
Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs...

 correctly. We perceive them as they really are. Objects obey the laws of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and retain all their properties whether or not there is anyone to observe them.

Scientific realism


Scientific realism
Scientific realism
Scientific realism is, at the most general level, the view that the world described by science is the real world, as it is, independent of what we might take it to be...

 is, at the most general level, the view that the world described by science is the real world, as it is, independent of what we might take it to be. Within philosophy of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

, 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 unobservable entities
Unobservables
An unobservable is an entity whose existence, nature, properties, qualities or relations are not directly observable by man. In philosophy of science typical examples of "unobservables" are atomic particles, the force of gravity, causation and beliefs or desires . However, some philosophers An...

 apparently talked about by scientific theories
Theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...

. Generally, those who are scientific realists assert that one can make reliable claims about unobservables (viz., that they have the same ontological
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

 status) as observables. Analytical philosophers generally have a commitment to scientific realism, in the sense of regarding the scientific method as a reliable guide to the nature of reality. The main alternative to scientific
realism is instrumentalism
Instrumentalism
In the philosophy of science, instrumentalism is the view that a scientific theory is a useful instrument in understanding the world. A concept or theory should be evaluated by how effectively it explains and predicts phenomena, as opposed to how accurately it describes objective...

.

In practice


Both these disputes are often carried out relative to some specific area: one might, for example, be a realist about physical matter but an anti-realist about ethics. The high necessity of specifying the area in which the claim is made has been increasingly acknowledged in recent years.

Increasingly these last disputes, too, are rejected as misleading, and some philosophers prefer to call the kind of realism espoused there "metaphysical realism," and eschew the whole debate in favour of simple "naturalism
Naturalism (philosophy)
Naturalism commonly refers to the philosophical viewpoint that the natural universe and its natural laws and forces operate in the universe, and that nothing exists beyond the natural universe or, if it does, it does not affect the natural universe that we know...

" or "natural realism", which is not so much a theory as the position that these debates are ill-conceived if not incoherent, and that there is no more to deciding what is really real than simply taking our words at face value.

Some realist philosophers prefer deflationary
Deflationary theory of truth
A deflationary theory of truth is one of a family of theories which all have in common the claim that assertions that predicate truth of a statement do not attribute a property called truth to such a statement.-Redundancy theory:...

 theories of truth to more traditional correspondence accounts.

Realism in logic and mathematics


Mathematical realism, like realism in general, holds that mathematical entities exist independently of the human mind
Mind
The concept of mind is understood in many different ways by many different traditions, ranging from panpsychism and animism to traditional and organized religious views, as well as secular and materialist philosophies. Most agree that minds are constituted by conscious experience and intelligent...

. Thus humans do not invent mathematics, but rather discover it, and any other intelligent beings in the universe would presumably do the same. In this point of view, there is really one sort of mathematics that can be discovered: Triangle
Triangle
A triangle is one of the basic shapes of geometry: a polygon with three corners or vertices and three sides or edges which are line segments. A triangle with vertices A, B, and C is denoted ....

s, for example, are real entities, not the creations of the human mind.

Many working mathematicians have been mathematical realists; they see themselves as discoverers of naturally occurring objects. Examples include Paul Erdős
Paul Erdos
Paul Erdős was a Hungarian mathematician. Erdős published more papers than any other mathematician in history, working with hundreds of collaborators. He worked on problems in combinatorics, graph theory, number theory, classical analysis, approximation theory, set theory, and probability theory...

 and Kurt Gödel
Kurt Gödel
Kurt Friedrich Gödel was an Austrian logician, mathematician and philosopher. Later in his life he emigrated to the United States to escape the effects of World War II. One of the most significant logicians of all time, Gödel made an immense impact upon scientific and philosophical thinking in the...

. Gödel believed in an objective mathematical reality that could be perceived in a manner analogous to sense perception. Certain principles (e.g., for any two objects, there is a collection of objects consisting of precisely those two objects) could be directly seen to be true, but some conjectures, like the continuum hypothesis
Continuum hypothesis
In mathematics, the continuum hypothesis is a hypothesis, advanced by Georg Cantor in 1874, about the possible sizes of infinite sets. It states:Establishing the truth or falsehood of the continuum hypothesis is the first of Hilbert's 23 problems presented in the year 1900...

, might prove undecidable just on the basis of such principles. Gödel suggested that quasi-empirical methodology could be used to provide sufficient evidence to be able to reasonably assume such a conjecture.

Within realism, there are distinctions depending on what sort of existence one takes mathematical entities to have, and how we know about them.

Alternatives to mathematical realism include formalism
Formalism (mathematics)
In foundations of mathematics, philosophy of mathematics, and philosophy of logic, formalism is a theory that holds that statements of mathematics and logic can be thought of as statements about the consequences of certain string manipulation rules....

 and fictionalism.

Moral Realism


Moral realism
Moral realism
Moral realism is the meta-ethical view which claims that:# Ethical sentences express propositions.# Some such propositions are true.# Those propositions are made true by objective features of the world, independent of subjective opinion....

 is the meta-ethical
Meta-ethics
In philosophy, meta-ethics is the branch of ethics that seeks to understand the nature of ethical properties, statements, attitudes, and judgments. Meta-ethics is one of the three branches of ethics generally recognized by philosophers, the others being normative ethics and applied ethics. Ethical...

 view which claims that:
  1. Ethical sentence
    Sentence (linguistics)
    In the field of linguistics, a sentence is an expression in natural language, and often defined to indicate a grammatical unit consisting of one or more words that generally bear minimal syntactic relation to the words that precede or follow it...

    s express proposition
    Proposition
    In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...

    s.
  2. Some such propositions are true.
  3. Those propositions are made true by objective features of the world, independent of subjective opinion.


This makes moral realism a non-nihilist
Moral nihilism
Moral nihilism is the meta-ethical view that nothing is moral or immoral. For example, a moral nihilist would say that killing someone, for whatever reason, is neither inherently right nor inherently wrong...

 form of cognitivism
Cognitivism (ethics)
Cognitivism is the meta-ethical view that ethical sentences express propositions and can therefore be true or false , which noncognitivists deny...

. Moral realism stands in opposition to all forms of moral anti-realism
Anti-realism
In analytic philosophy, the term anti-realism is used to describe any position involving either the denial of an objective reality of entities of a certain type or the denial that verification-transcendent statements about a type of entity are either true or false...

, including ethical subjectivism
Ethical subjectivism
Ethical subjectivism is the meta-ethical view which claims that:# Ethical sentences express propositions.# Some such propositions are true.# Those propositions are about the attitudes of people.This makes ethical subjectivism a form of cognitivism...

 (which denies that moral propositions refer to objective facts), error theory (which denies that any moral propositions are true), and non-cognitivism
Non-cognitivism
Non-cognitivism is the meta-ethical view that ethical sentences do not express propositions and thus cannot be true or false...

 (which denies that moral sentences express propositions at all). Within moral realism, the two main subdivisions are ethical naturalism
Ethical naturalism
Ethical naturalism is the meta-ethical view which claims that:# Ethical sentences express propositions.# Some such propositions are true....

 and ethical non-naturalism
Ethical non-naturalism
Ethical non-naturalism is the meta-ethical view which claims that:# Ethical sentences express propositions.# Some such propositions are true.# Those propositions are made true by objective features of the world, independent of human opinion....

.

Time and space



A traditional realist position in ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

 is that time and space have existence apart from the human mind. Idealists
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

 deny or doubt the existence of objects independent of the mind. Some anti-realists
Anti-realism
In analytic philosophy, the term anti-realism is used to describe any position involving either the denial of an objective reality of entities of a certain type or the denial that verification-transcendent statements about a type of entity are either true or false...

 whose ontological position is that objects outside the mind do exist, nevertheless doubt the independent existence of time and space.

As well as differing about the reality of time as a whole, metaphysical theories of time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 can differ in their ascriptions of reality to the past
Past
Most generally, the past is a term used to indicate the totality of events which occurred before a given point in time. The past is contrasted with and defined by the present and the future. The concept of the past is derived from the linear fashion in which human observers experience time, and is...

, present
Present
Present is a time that is neither past nor future.Present may also refer to:- Time and timing :* Present tense, the grammatical tense of a verb* Before Present, radiocarbon dates relative to AD 1950* Presenting, a medical term* Presenteeism...

 and future
Future
The future is the indefinite time period after the present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the nature of the reality and the unavoidability of the future, everything that currently exists and will exist is temporary and will come...

 separately.
  • Presentism
    Presentism (philosophy of time)
    Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. This seems evident because, if the present is extended, it must have separate parts - but these must be simultaneous if they are truly part of the present...

     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
    Theory of relativity
    The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....

    .
  • The growing block universe
    Growing block universe
    According to the Growing Block Universe or The Growing Block View theory of time, the past and present exist and the future does not exist. The present is an objective property, to be compared with a moving spotlight. By the passage of time more of the world comes into being, therefore the block...

     theory holds that past and present are real, but the future is not.

Modal realism


Modal realism
Modal realism
Modal realism is the view, notably propounded by David Kellogg Lewis, that all possible worlds are as real as the actual world. It is based on the following tenets: possible worlds exist; possible worlds are not different in kind from the actual world; possible worlds are irreducible entities; the...

 is the view, notably propounded by David Kellogg Lewis
David Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...

, that all possible worlds
Possible Worlds
Possible Worlds may refer to:* Possible worlds, a concept in philosophy* Possible Worlds , by John Mighton** Possible Worlds , by Robert Lepage, based on the Mighton play* Possible Worlds , by Peter Porter...

 are as real as the actual world. It is based on the following tenets: possible worlds exist
Existence
In common usage, existence is the world we are aware of through our senses, and that persists independently without them. In academic philosophy the word has a more specialized meaning, being contrasted with essence, which specifies different forms of existence as well as different identity...

; possible worlds are not different in kind from the actual world; possible worlds are irreducible
Reduction (philosophy)
In philosophy, reduction is the process by which one object, property, concept, theory, etc., is shown to be explicable in terms of another, lower level, entity...

 entities
Entity
An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...

; the term actual in actual world is indexical
Indexicality
In linguistics and in philosophy of language, an indexical behavior or utterance points to some state of affairs. For example, I refers to whoever is speaking; now refers to the time at which that word is uttered; and here refers to the place of utterance...

, i.e. any subject can declare their world to be the actual one, much as they
label the place they are "here" and the time they are "now".

See also

  • Analytic philosophy
    Analytic philosophy
    Analytic philosophy is a generic term for a style of philosophy that came to dominate English-speaking countries in the 20th century...

  • Critical realism
    Critical realism
    In the philosophy of perception, critical realism is the theory that some of our sense-data can and do accurately represent external objects, properties, and events, while other of our sense-data do not accurately represent any external objects, properties, and events...

  • Epistemological realism
    Epistemological realism
    Epistemological realism is a philosophical position, a subcategory of objectivism, holding that what you know about an object exists independently of your mind. It opposes epistemological idealism....

  • Legal realism
    Legal realism
    Legal realism is a school of legal philosophy that is generally associated with the culmination of the early-twentieth century attack on the orthodox claims of late-nineteenth-century classical legal thought in the United States...

  • Moderate realism
    Moderate realism
    Moderate realism is a position in the debate on the metaphysics of universals which holds that there is no realm in which universals exist , nor do they really exist within the individuals as universals, but rather universals really exist within the particulars as individualised, and multiplied...

  • Objectivism
    Objectivism (Ayn Rand)
    Objectivism is a philosophy created by the Russian-American philosopher and novelist Ayn Rand . Objectivism holds that reality exists independent of consciousness, that human beings have direct contact with reality through sense perception, that one can attain objective knowledge from perception...

  • Philosophy of social science
    Philosophy of social science
    The philosophy of social science is the study of the logic and method of the social sciences, such as sociology, anthropology and political science...

  • Principle of bivalence
    Principle of bivalence
    In logic, the semantic principle of bivalence states that every declarative sentence expressing a proposition has exactly one truth value, either true or false...

  • Problem of future contingents
  • Truth-value link realism

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