Theory of truth (1935)

Semantic concept formalized by the Polish-American mathematician and logician Alfred Tarski (1902-1983), although other thinkers had previously discussed the idea.

Truth theory concerns the truth-values of sentence structures in various formal logical languages. Tarski suggested a table by which these values could be determined (although he was less sure about whether the same rules could be applied to natural languages).

Also see: correspondence theory of truth

A Tarski, ‘The Concept of Truth in Formalized Languages’, Logic, Semantics and Metamathe-matics (1956)

Truth is the property of being in accord with fact or reality.[1] In everyday language, truth is typically ascribed to things that aim to represent reality or otherwise correspond to it, such as beliefs, propositions, and declarative sentences.[2]

Truth is usually held to be the opposite of falsehood. The concept of truth is discussed and debated in various contexts, including philosophy, art, theology, and science. Most human activities depend upon the concept, where its nature as a concept is assumed rather than being a subject of discussion; these include most of the sciences, law, journalism, and everyday life. Some philosophers view the concept of truth as basic, and unable to be explained in any terms that are more easily understood than the concept of truth itself.[2] Most commonly, truth is viewed as the correspondence of language or thought to a mind-independent world. This is called the correspondence theory of truth.

Various theories and views of truth continue to be debated among scholars, philosophers, and theologians.[2][3] There are many different questions about the nature of truth which are still the subject of contemporary debates, such as: How do we define truth? Is it even possible to give an informative definition of truth? What things are truthbearers and are therefore capable of being true or false? Are truth and falsehood bivalent, or are there other truth values? What are the criteria of truth that allow us to identify it and to distinguish it from falsehood? What role does truth play in constituting knowledge? And is truth always absolute, or can it be relative to one’s perspective?

Definition and etymology

An angel carrying the banner of “Truth”, Roslin, Midlothian

The English word truth is derived from Old English tríewþ, tréowþ, trýwþ, Middle English trewþe, cognate to Old High German triuwida, Old Norse tryggð. Like troth, it is a -th nominalisation of the adjective true (Old English tréowe).

The English word true is from Old English (West Saxon) (ge)tríewe, tréowe, cognate to Old Saxon (gi)trûui, Old High German (ga)triuwu (Modern German treu “faithful”), Old Norse tryggr, Gothic triggws,[4] all from a Proto-Germanic *trewwj- “having good faith”, perhaps ultimately from PIE *dru- “tree”, on the notion of “steadfast as an oak” (e.g., Sanskrit dā́ru “(piece of) wood”).[5] Old Norse trú, “faith, word of honour; religious faith, belief”[6] (archaic English troth “loyalty, honesty, good faith”, compare Ásatrú).

Thus, ‘truth’ involves both the quality of “faithfulness, fidelity, loyalty, sincerity, veracity”,[7] and that of “agreement with fact or reality”, in Anglo-Saxon expressed by sōþ (Modern English sooth).

All Germanic languages besides English have introduced a terminological distinction between truth “fidelity” and truth “factuality”. To express “factuality”, North Germanic opted for nouns derived from sanna “to assert, affirm”, while continental West Germanic (German and Dutch) opted for continuations of wâra “faith, trust, pact” (cognate to Slavic věra “(religious) faith”, but influenced by Latin verus). Romance languages use terms following the Latin veritas, while the Greek aletheia, Russian pravda, South Slavic istina and Sanskrit sat (related to English sooth and North Germanic sanna) have separate etymological origins.

In some modern contexts, the word “truth” is used to refer to fidelity to an original or standard. It can also be used in the context of being “true to oneself” in the sense of acting with authenticity.[1]

Major theories

The question of what is a proper basis for deciding how words, symbols, ideas and beliefs may properly be considered true, whether by a single person or an entire society, is dealt with by the five most prevalent substantive theories of truth listed below. Each presents perspectives that are widely shared by published scholars.[8][9][10]

Theories other than the most prevalent substantive theories are also discussed. More recently developed “deflationary” or “minimalist” theories of truth have emerged as possible alternatives to the most prevalent substantive theories. Minimalist reasoning centres around the notion that the application of a term like true to a statement does not assert anything significant about it, for instance, anything about its nature. Minimalist reasoning realises truth as a label utilised in general discourse to express agreement, to stress claims, or to form general assumptions.[8][11][12]

According to a survey of professional philosophers and others on their philosophical views which was carried out in November 2009 (taken by 3226 respondents, including 1803 philosophy faculty members and/or PhDs and 829 philosophy graduate students) 45% of respondents accept or lean towards correspondence theories, 21% accept or lean towards deflationary theories and 14% epistemic theories.[13]



Correspondence theories emphasize that true beliefs and true statements correspond to the actual state of affairs.[14] This type of theory stresses a relationship between thoughts or statements on one hand, and things or objects on the other. It is a traditional model tracing its origins to ancient Greek philosophers such as Socrates, Plato, and Aristotle.[15] This class of theories holds that the truth or the falsity of a representation is determined in principle entirely by how it relates to “things” by whether it accurately describes those “things”. A classic example of correspondence theory is the statement by the thirteenth century philosopher and theologian Thomas Aquinas: “Veritas est adaequatio rei et intellectus” (“Truth is the adequation of things and intellect”), which Aquinas attributed to the ninth century Neoplatonist Isaac Israeli.[16][17][18] Aquinas also restated the theory as: “A judgment is said to be true when it conforms to the external reality”.[19]

Correspondence theory centres heavily around the assumption that truth is a matter of accurately copying what is known as “objective reality” and then representing it in thoughts, words and other symbols.[20] Many modern theorists have stated that this ideal cannot be achieved without analysing additional factors.[8][21] For example, language plays a role in that all languages have words to represent concepts that are virtually undefined in other languages. The German word Zeitgeist is one such example: one who speaks or understands the language may “know” what it means, but any translation of the word apparently fails to accurately capture its full meaning (this is a problem with many abstract words, especially those derived in agglutinative languages). Thus, some words add an additional parameter to the construction of an accurate truth predicate. Among the philosophers who grappled with this problem is Alfred Tarski, whose semantic theory is summarized further below in this article.[22]

Proponents of several of the theories below have gone further to assert that there are yet other issues necessary to the analysis, such as interpersonal power struggles, community interactions, personal biases and other factors involved in deciding what is seen as truth.


Walter Seymour Allward’s Veritas (Truth) outside Supreme Court of Canada, Ottawa, Ontario Canada

For coherence theories in general, truth requires a proper fit of elements within a whole system. Very often, though, coherence is taken to imply something more than simple logical consistency; often there is a demand that the propositions in a coherent system lend mutual inferential support to each other. So, for example, the completeness and comprehensiveness of the underlying set of concepts is a critical factor in judging the validity and usefulness of a coherent system.[23] A pervasive tenet of coherence theories is the idea that truth is primarily a property of whole systems of propositions, and can be ascribed to individual propositions only according to their coherence with the whole. Among the assortment of perspectives commonly regarded as coherence theory, theorists differ on the question of whether coherence entails many possible true systems of thought or only a single absolute system.

Some variants of coherence theory are claimed to describe the essential and intrinsic properties of formal systems in logic and mathematics.[24] However, formal reasoners are content to contemplate axiomatically independent and sometimes mutually contradictory systems side by side, for example, the various alternative geometries. On the whole, coherence theories have been rejected for lacking justification in their application to other areas of truth, especially with respect to assertions about the natural world, empirical data in general, assertions about practical matters of psychology and society, especially when used without support from the other major theories of truth.[25]

Coherence theories distinguish the thought of rationalist philosophers, particularly of Baruch Spinoza, Gottfried Wilhelm Leibniz, and Georg Wilhelm Friedrich Hegel, along with the British philosopher F. H. Bradley.[26] They have found a resurgence also among several proponents of logical positivism, notably Otto Neurath and Carl Hempel.


The three most influential forms of the pragmatic theory of truth were introduced around the turn of the 20th century by Charles Sanders Peirce, William James, and John Dewey. Although there are wide differences in viewpoint among these and other proponents of pragmatic theory, they hold in common that truth is verified and confirmed by the results of putting one’s concepts into practice.[27]

Peirce defines truth as follows: “Truth is that concordance of an abstract statement with the ideal limit towards which endless investigation would tend to bring scientific belief, which concordance the abstract statement may possess by virtue of the confession of its inaccuracy and one-sidedness, and this confession is an essential ingredient of truth.”[28] This statement stresses Peirce’s view that ideas of approximation, incompleteness, and partiality, what he describes elsewhere as fallibilism and “reference to the future”, are essential to a proper conception of truth. Although Peirce uses words like concordance and correspondence to describe one aspect of the pragmatic sign relation, he is also quite explicit in saying that definitions of truth based on mere correspondence are no more than nominal definitions, which he accords a lower status than real definitions.

William James’s version of pragmatic theory, while complex, is often summarized by his statement that “the ‘true’ is only the expedient in our way of thinking, just as the ‘right’ is only the expedient in our way of behaving.”[29] By this, James meant that truth is a quality, the value of which is confirmed by its effectiveness when applying concepts to practice (thus, “pragmatic”).

John Dewey, less broadly than James but more broadly than Peirce, held that inquiry, whether scientific, technical, sociological, philosophical or cultural, is self-corrective over time if openly submitted for testing by a community of inquirers in order to clarify, justify, refine and/or refute proposed truths.[30]

Though not widely known, a new variation of the pragmatic theory was defined and wielded successfully from the 20th century forward. Defined and named by William Ernest Hocking, this variation is known as “negative pragmatism”. Essentially, what works may or may not be true, but what fails cannot be true because the truth always works.[31] Richard Feynman also ascribed to it: “We never are definitely right, we can only be sure we are wrong.”[32] This approach incorporates many of the ideas from Peirce, James, and Dewey. For Peirce, the idea of “… endless investigation would tend to bring about scientific belief …” fits negative pragmatism in that a negative pragmatist would never stop testing. As Feynman noted, an idea or theory “… could never be proved right, because tomorrow’s experiment might succeed in proving wrong what you thought was right.”[32] Similarly, James and Dewey’s ideas also ascribe truth to repeated testing which is “self-corrective” over time.

Pragmatism and negative pragmatism are also closely aligned with the coherence theory of truth in that any testing should not be isolated but rather incorporate knowledge from all human endeavors and experience. The universe is a whole and integrated system, and testing should acknowledge and account for its diversity. As Feynman said, “… if it disagrees with experiment, it is wrong.”[33]


Social constructivism holds that truth is constructed by social processes, is historically and culturally specific, and that it is in part shaped through the power struggles within a community. Constructivism views all of our knowledge as “constructed,” because it does not reflect any external “transcendent” realities (as a pure correspondence theory might hold). Rather, perceptions of truth are viewed as contingent on convention, human perception, and social experience. It is believed by constructivists that representations of physical and biological reality, including race, sexuality, and gender, are socially constructed.

Giambattista Vico was among the first to claim that history and culture were man-made. Vico’s epistemological orientation gathers the most diverse rays and unfolds in one axiom—verum ipsum factum—”truth itself is constructed”. Hegel and Marx were among the other early proponents of the premise that truth is, or can be, socially constructed. Marx, like many critical theorists who followed, did not reject the existence of objective truth but rather distinguished between true knowledge and knowledge that has been distorted through power or ideology. For Marx, scientific and true knowledge is “in accordance with the dialectical understanding of history” and ideological knowledge is “an epiphenomenal expression of the relation of material forces in a given economic arrangement”.

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