Theories of truth aim to identify what all truths have in common. They seek to clarify the role and concept of truth and discern its essential features. Different theories disagree about what those features are, whether they depend on the domain of analysis, and whether truth has a substantive definition.
Substantive
Correspondence
Correspondence theories emphasize that true beliefs and true statements correspond to the actual state of affairs.Encyclopedia of Philosophy, Vol.2, "Correspondence Theory of Truth", auth.: Arthur N. Prior, p. 223 (Macmillan, 1969). Prior uses Bertrand Russell's wording in defining correspondence theory. According to Prior, Russell was substantially responsible for helping to make correspondence theory widely known under this name. 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.Encyclopedia of Philosophy, Vol.2, "Correspondence Theory of Truth", auth.: Arthur N. Prior, pp. 223–224 (Macmillan, 1969). 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" according to 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.Encyclopedia of Philosophy, Vol. 2, "Correspondence Theory of Truth", auth.: Arthur N. Prior, Macmillan, 1969, p. 224."Correspondence Theory of Truth", in Stanford Encyclopedia of Philosophy .Thomas Aquinas, Summa Theologiae, I. Q.16, A.2 arg. 2. Aquinas also restated the theory as: "A judgment is said to be true when it conforms to the external reality"."Correspondence Theory of Truth", in Stanford Encyclopedia of Philosophy (citing De Veritate Q.1, A.1–3 and Summa Theologiae, I. Q.16).
Correspondence theory centres 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.See, e.g., Bradley, F.H., "On Truth and Copying", in Blackburn, et al. (eds., 1999),Truth, 31–45. Many modern theorists have stated that this ideal cannot be achieved without analysing additional factors.Encyclopedia of Philosophy, Vol.2, "Correspondence Theory of Truth", auth: Arthur N. Prior, pp. 223 ff. Macmillan, 1969. See especially, section on "Moore's Correspondence Theory", 225–226, "Russell's Correspondence Theory", 226–227, "Remsey and Later Wittgenstein", 228–229, "Tarski's Semantic Theory", 230–231. 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 on.Encyclopedia of Philosophy, Vol.2, "Correspondence Theory of Truth", auth: Arthur N. Prior, pp. 223 ff. Macmillan, 1969. See the section on "Tarski's Semantic Theory", 230–231.
Coherence
For coherence theories in general, truth requires a proper fit of elements within a whole system. Very often, 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.Immanuel Kant, for instance, assembled a controversial but quite coherent system in the early 19th century, whose validity and usefulness continues to be debated even today. Similarly, the systems of Leibniz and Spinoza are characteristic systems that are internally coherent but controversial in terms of their utility and validity. A central tenet of coherence theories is the idea that truth is primarily a property of whole systems of propositions, and can be ascribed to an individual proposition only in virtue of its relationship to that system as a 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.Encyclopedia of Philosophy, Vol.2, "Coherence Theory of Truth", auth: Alan R. White, pp. 130–131 (Macmillan, 1969) 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.Encyclopedia of Philosophy, Vol.2, "Coherence Theory of Truth", auth: Alan R. White, pp. 131–133, see esp., section on "Epistemological assumptions" (Macmillan, 1969)
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.Encyclopedia of Philosophy, Vol.2, "Coherence Theory of Truth", auth: Alan R. White, p. 130 They have found a resurgence also among several proponents of logical positivism, notably Otto Neurath and Carl Hempel.
Pragmatic
Three 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 all hold that truth is verified and confirmed by the results of putting one's concepts into practice.Encyclopedia of Philosophy, Vol. 5, "Pragmatic Theory of Truth", 427 (Macmillan, 1969).
Peirce defines it: "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."Peirce, C.S. (1901), "Truth and Falsity and Error" (in part), pp. 716–720 in James Mark Baldwin, ed., Dictionary of Philosophy and Psychology, v. 2. Peirce's section is entitled "Logical", beginning on p. 718, column 1, and ending on p. 720 with the initials "(C.S.P.)", see Google Books Eprint. Reprinted, Collected Papers v. 5, pp. 565–573. 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.
James' 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."James, William, The Meaning of Truth, A Sequel to 'Pragmatism', (1909). 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").
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.Encyclopedia of Philosophy, Vol.2, "Dewey, John", by Richard J. Bernstein, p. 383 (Macmillan, 1969)
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.Sahakian, W.S. & Sahakian, M.L., Ideas of the Great Philosophers, New York: Barnes & Noble, 1966, Philosopher of science Richard Feynman also subscribed to it: "We never are definitely right, we can only be sure we are wrong." 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." 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."
Constructivist
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 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".
Consensus
Consensus theory holds that truth is whatever is agreed upon, or in some versions, might come to be agreed upon, by some specified group. Such a group might include all human beings, or a subset thereof consisting of more than one person.