Truth

The correspondence theory of truth holds that a belief or proposition is true when it corresponds to the way the world is. The theory originated with Plato (c. 428–348 or 347 B.C.E.) and held the stage in Western theories of truth through the eighteenth century. At Theaetetus 188c–189b, Plato considered what is sometimes called the "existence" theory of truth: true opinion is thinking what is, while false opinion is thinking what is not (pp. 893–895). Plato dismissed this view of false opinion on the ground that to think what is not is to think nothing, and this is no more possible than to see nothing. At Sophist 240d–241a and 260c–263d, Plato proposed an alternative theory of truth designed to circumvent this difficulty: a thought resembles a sentence in consisting of a noun and a verb, and one's thought can be about something even though it is false because the noun refers to an object while the verb misdescribes this object (pp. 984, 1007–1011). This is a correspondence theory in the sense that truth requires that the truth bearer concatenate a noun and verb just as the object to which the noun refers has the property expressed by the verb.

At De Interpretatione 16a10–19, Aristotle (384–322 B.C.E.) endorsed Plato's Sophist point against the existence theory when he proposed that truth and falsity require names and verbs in combination or separation (p. 25). His definition of truth at Metaphysics 7, 1011b26ff is committed to complex truth bearers: "To say of what is that it is not, or of what is not that it is, is false, while to say of what is that it is, and of what is not that it is not, is true …" (pp. 1597–1598).

The Stoics also offered a correspondence theory: "They [the Stoics] say that a true proposition [ axioma ] is that which is and is contradictory to something" (Sextus Empiricus, p. 203). However, the Stoics parted with Aristotle in defending the principle of bivalence, that there are only two truth values, true and false. St. Thomas Aquinas (c. 1224–1274) said that "truth is primarily in intellect; and secondarily in things, by virtue of a relation to intellect as to their origin" (p. 63).

Philosophers of the seventeenth and eighteenth centuries also accepted the correspondence definition of truth, but they differed from their ancient and medieval predecessors in emphasizing that the definition has no utility as a criterion of truth, that is, as a means to judge whether given propositions are true. René Descartes (1596–1650) conceded that "the word truth, in the strict sense, denotes the conformity of thought with its object" (p. 65). But he denied that this definition is useful for clarifying or explaining the concept: "it seems a notion so transcendentally clear that nobody can be ignorant of it" (p. 65); a definition can only cause confusion. He offered clear and distinct perception as a criterion of truth.

Baruch Spinoza (1632–1677) expressly applied true to ideas in Ethics: "A true idea must agree with its object" (p. 410). The axiom is used to show that reason regards things as necessary.

John Locke (1632–1704) endorsed the Platonic-Aristotelian view that true applies strictly to truth bearers of subject-predicate form—to propositions, in particular. He did not, however, formulate a correspondence definition of true proposition. Instead, he offered an account of the conditions in which truth is ascribed to ideas. Though ideas do not have a subject-predicate form and are thus not strictly true, one nevertheless ascribes truth to them in a manner that derives from one's "tacit supposition of their conformity to" their object (p. 514). When I ascribe truth to an idea belonging to another individual, I say that the idea is true when I suppose it conforms to my idea; and when I ascribe truth to my own idea, I suppose it is "conformable to some real existence" (Locke, p. 515). David Hume (1711–1776) loosely follows Locke in his account of the kinds of truth in the Treatise: "Truth is of two kinds, consisting either in the discovery of the proportions of ideas, consider'd as such, or in the conformity of our ideas of objects to their real existence" (p. 448). The second kind of truth, concerning matters of fact, echoes Locke's account of the ascription of truth to my own ideas and defines truth for matters of fact as conformity to the real existence of objects. Note that Hume endorses a correspondence theory only for matters of fact, not for matters of reason (or the discovery of proportions of ideas).

In the Critique of Pure Reason, Immanuel Kant (1724–1804) defined truth as correspondence: "The nominal definition of truth, namely that it is the agreement of cognition with its object, is here granted and presupposed; but one demands to know what is the general and certain criterion of the truth of any cognition" (p. 197). However, Kant denied that there is a universal material criterion of truth and observed that a universal formal criterion of truth, being nothing but logic, is sufficient only for consistency, not truth. Georg Wilhelm Friedrich Hegel (1770–1831) too accepted a correspondence definition of truth in his Science of Logic: "Objective truth is no doubt the Idea itself as the reality that corresponds to the Notion" (p. 784). But he did not see this as helping us with subjective truth.