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In "analytic philosophy, **anti-realism** is an "epistemological position first articulated by British philosopher "Michael Dummett. The term was coined as an argument against a form of "realism Dummett saw as 'colorless reductionism'.^{[1]}

In anti-realism, the truth of a statement rests on its demonstrability through internal logic mechanisms, such as Frege's "context principle and Heyting's "intuitionistic logic, in direct opposition to the realist notion that the truth of a statement rests on its correspondence to an external, independent reality.^{[2]} In anti-realism, this external reality is hypothetical and is not assumed.^{[3]}^{[4]}

Because it encompasses statements containing abstract ideal objects (i.e. mathematical objects), anti-realism may apply to a wide range of philosophic topics, from "material objects to the theoretical entities of "science, "mathematical statement, "mental states, events and processes, the "past and the "future.^{[5]}

The term "anti-realism" was introduced by "Michael Dummett in his paper *Realism* in order to re-examine a number of classical philosophical disputes, involving such doctrines as "nominalism, conceptual realism, "idealism and "phenomenalism. The novelty of Dummett's approach consisted in portraying these disputes as analogous to the dispute between "intuitionism and "Platonism in the "philosophy of mathematics.

According to intuitionists (anti-realists with respect to mathematical objects), the "truth of a mathematical statement consists in our ability to prove it. According to Platonic realists, the truth of a statement is proven in its correspondence to "objective reality. Thus, intuitionists are ready to accept a statement of the form "P or Q" as true "only if we can prove P or if we can prove Q. In particular, we cannot in general claim that "P or not P" is true (the "law of Excluded Middle), since in some cases "we may not be able to prove the statement "P" nor prove the statement "not P". Similarly, intuitionists object to the "existence property for classical logic, where one can prove , without being able to produce any term of which holds.

Dummett argues that this notion of truth lies at the bottom of various classical forms of **anti-realism**, and uses it to re-interpret "phenomenalism, claiming that it need not take the form of "reductionism.

Dummett's writings on anti-realism draw heavily on the later writings of "Wittgenstein, concerning meaning and rule following, and can be seen as an attempt to integrate central ideas from the *"Philosophical Investigations* into the constructive tradition of "analytic philosophy deriving from "Frege.

Idealists maintain a "skepticism about the physical world, arguing either: 1) that nothing exists outside the mind, or 2) that we would have no access to a mind-independent reality, even if it exists. The latter case often takes the form of a denial of the idea that we can have 'unconceptualised' experiences (see "Myth of the Given). Conversely, most realists (specifically, "indirect realists) hold that perceptions or "sense data are caused by mind-independent objects. But this introduces the possibility of another kind of skepticism: since our understanding of "causality is that the same effect can be produced by multiple causes, there is a "lack of determinacy about what one is really perceiving, as in the "brain in a vat scenario.

On a more abstract level, "model theoretic arguments hold that a given set of "symbols in a "theory can be mapped onto any number of sets of real-world objects—each set being a "model" of the theory—provided the relationship between the objects is the same. (Compare with "symbol grounding.)

In "philosophy of science, anti-realism applies chiefly to claims about the non-reality of "unobservable" "entities such as "electrons or "genes, which are not detectable with human senses.^{[6]}^{[7]} One prominent position in the philosophy of science is "instrumentalism, which is a non-realist position which takes a purely agnostic view towards the existence of unobservable entities, in which the unobservable entity X serves as an instrument to aid in the success of theory Y does not require proof for the existence or non-existence of X.

Some scientific anti-realists, however, deny that unobservables exist, even as non-truth conditioned instruments.

In the "philosophy of mathematics, realism is the claim that mathematical entities such as 'number' have an observer-independent existence. "Empiricism, which associates numbers with concrete physical objects, and "Platonism, in which numbers are abstract, non-physical entities, are the preeminent forms of mathematical realism.

The ""epistemic argument" against Platonism has been made by "Paul Benacerraf and "Hartry Field. Platonism posits that mathematical objects are *"abstract* entities. By general agreement, abstract entities cannot interact "causally with physical entities ("the truth-values of our mathematical assertions depend on facts involving platonic entities that reside in a realm outside of space-time"^{[8]}) Whilst our knowledge of physical objects is based on our ability to "perceive them, and therefore to causally interact with them, there is no parallel account of how mathematicians come to have knowledge of abstract objects.^{[9]}^{[10]}^{[11]}

Field developed his views into "fictionalism. Benacerraf also developed the philosophy of "mathematical structuralism, according to which there are no mathematical objects. Nonetheless, some versions of structuralism are compatible with some versions of realism.

Anti-realist arguments hinge on the idea that a satisfactory, "naturalistic account of thought processes can be given for mathematical reasoning. One line of defense is to maintain that this is false, so that mathematical reasoning uses some special "intuition that involves contact with the Platonic realm, as in the argument given by "Sir Roger Penrose.^{[12]}

Another line of defense is to maintain that abstract objects are relevant to mathematical reasoning in a way that is non causal, and not analogous to perception. This argument is developed by "Jerrold Katz in his book *"Realistic Rationalism*.

A more radical defense is to deny the separation of physical world and the platonic world, i.e. the "mathematical universe hypothesis. In that case, a mathematician's knowledge of mathematics is one mathematical object making contact with another.

**^**Realism(1963) p.145**^**"Realism(1963) p.146**^**"Truth(1959) p.24 (postscript)**^**"Blackburn, Simon ([2005] 2008). "realism/anti-realism,"*"The Oxford Dictionary of Philosophy*, 2nd ed. revised, pp. 308-09. Oxford.**^**Realism(1963) pp.147-148**^**Hacking, Ian (1999).*The Social Construction Of What?*. Harvard University Press. p. 84.**^**Okasha, Samir (2002).*Philosophy of Science: A Very Short Introduction*. Oxford University Press.**^**Field, Hartry, 1989,*Realism, Mathematics, and Modality*, Oxford: Blackwell, p. 68**^**"Since abstract objects are outside the nexus of causes and effects, and thus perceptually inaccessible, they cannot be known through their effects on us" — Katz, J.*Realistic Rationalism*, p. 15**^**Philosophy Now: "Mathematical Knowledge: A dilemma"**^**Stanford Encyclopedia of Philosophy**^**Review of "The Emperor's New Mind

- Michael Dummett (1978).
*Truth and Other Enigmas*. Harvard University Press.- Michael Dummett (1963),
*Truth*. reprinted, pp. 1–24. - Michael Dummett (1963),
*Realism*. reprinted, pp. 145–165. - Michael Dummett (1967),
*Platonism*. reprinted, pp. 202–214.

- Michael Dummett (1963),
- Christine Baron, Manfred Engel (eds.) (2010).
*Realism/Anti-Realism in 20th-Century Literature. Rodopi: 2010. "ISBN "978-90-420-3115-9* - Lee Braver (2007).
*A Thing of This World: a History of Continental Anti-Realism,*Northwestern University Press: 2007. - Ian Hacking (1999).
*The Social Construction of What?*. Harvard University Press: 2001. - Samir Okasha (2002).
*Philosophy of Science: A Very Short Introduction*. Oxford University Press. - 金子 洋之 (2006).
*ダメットにたどりつくまで*. 勁草書房. (Japanese)

- "Scientific Realism and Antirealism".
*"Internet Encyclopedia of Philosophy*. - Semantic challenges to realism in the Stanford Encyclopedia of Philosophy