truth the quality of those propositions that accord with reality, specifying what is in fact the case. Whereas the aim of a science is to discover which of the propositions in its domain are true i.e., which propositions possess the property of truth – the central philosophical concern with truth is to discover the nature of that property. Thus the philosophical question is not What is true? but rather, What is truth? – What is one saying about a proposition in saying that it is true? The importance of this question stems from the variety and depth of the principles in which the concept of truth is deployed. We are tempted to think, e.g., that truth is the proper aim and natural result of scientific inquiry, that true beliefs are useful, that the meaning of a sentence is given by the conditions that would render it true, and that valid reasoning preserves truth. Therefore insofar as we wish to understand, assess, and refine these epistemological, ethical, semantic, and logical views, some account of the nature of truth would seem to be required. Such a thing, however, has been notoriously elusive.
The belief that snow is white owes its truth to a certain feature of the external world: the fact that snow is white. Similarly, the belief that dogs bark is true because of the fact that dogs bark. Such trivial observations lead to what is perhaps the most natural and widely held account of truth, the correspondence theory, according to which a belief (statement, sentence, proposition, etc.) is true provided there exists a fact corresponding to it. This Aristotelian thesis is unexceptionable in itself. However, if it is to provide a complete theory of truth – and if it is to be more than merely a picturesque way of asserting all instances of ‘the belief that p is true if and only if p’ – then it must be supplemented with accounts of what facts are, and what it is for a belief to correspond to a fact; and these are the problems on which the correspondence theory of truth has foundered.
A popular alternative to the correspondence theory has been to identify truth with verifiability. This idea can take on various forms. One version involves the further assumption that verification is holistic – i.e., that a belief is verified when it is part of an entire system of beliefs that is consistent and ‘harmonious.’ This is known as the coherence theory of truth and was developed by Bradley and Brand Blanchard. Another version, due to Dummett and Putnam, involves the assumption that there is, for each proposition, some specific procedure for finding out whether one should believe it or not. On this account, to say that a proposition is true is to say that it would be verified by the appropriate procedure. In mathematics this amounts to the identification of truth with provability and is sometimes referred to as intuitionistic truth. Such theories aim to avoid obscure metaphysical notions and explain the close relation between knowability and truth. They appear, however, to overstate the intimacy of that link: for we can easily imagine a statement that, though true, is beyond our power to establish as true. A third major account of truth is James’s pragmatic theory. As we have just seen, the verificationist selects a prominent property of truth and considers it to be the essence of truth. Similarly the pragmatist focuses on another important characteristic – namely, that true beliefs are a good basis for action – and takes this to be the very nature of truth. True assumptions are said to be, by definition, those that provoke actions with desirable results. Again we have an account with a single attractive explanatory feature. But again the central objection is that the relationship it postulates between truth and its alleged analysans – in this case, utility – is implausibly close. Granted, true beliefs tend to foster success. But often actions based on true beliefs lead to disaster, while false assumptions, by pure chance, produce wonderful results. One of the few fairly uncontroversial facts about truth is that the proposition that snow is white is true if and only if snow is white, the proposition that lying is wrong is true if and only if lying is wrong, and so on. Traditional theories of truth acknowledge this fact but regard it as insufficient and, as we have seen, inflate it with some further principle of the form ‘X is true if and only if X has property P’ (such as corresponding to reality, verifiability, or being suitable as a basis for action), which is supposed to specify what truth is. A collection of radical alternatives to the traditional theories results from denying the need for any such further specification. For example, one might suppose (with Ramsey, Ayer, and Strawson) that the basic theory of truth contains nothing more than equivalences of the form, ‘The proposition that p is true if and only if p’ (excluding instantiation by sentences such as ‘This proposition is not true’ that generate contradiction). This so-called deflationary theory is best presented (following Quine) in conjunction with an account of the raison d’être of our notion of truth: namely, that its function is not to describe propositions, as one might naively infer from its syntactic form, but rather to enable us to construct a certain type of generalization. For example, ‘What Einstein said is true’ is intuitively equivalent to the infinite conjunction ‘If Einstein said that nothing goes faster than light, then nothing goes faster than light; and if Einstein said that nuclear weapons should never be built, then nuclear weapons should never be built; . . . and so on.’ But without a truth predicate we could not capture this statement. The deflationist argues, moreover, that all legitimate uses of the truth predicate – including those in science, logic, semantics, and metaphysics – are simply displays of this generalizing function, and that the equivalence schema is just what is needed to explain that function.
Within the deflationary camp there are various competing proposals. According to Frege’s socalled redundancy theory, corresponding instances of ‘It is true that p’ and ‘p’ have exactly the same meaning, whereas the minimalist theory assumes merely that such propositions are necessarily equivalent. Other deflationists are skeptical about the existence of propositions and therefore take sentences to be the basic vehicles of truth. Thus the disquotation theory supposes that truth is captured by the disquotation principle, ‘p’ is true if and only if p’. More ambitiously, Tarski does not regard the disquotation principle, also known as Tarski’s (T) schema, as an adequate theory in itself, but as a specification of what any adequate definition must imply. His own account shows how to give an explicit definition of truth for all the sentences of certain formal languages in terms of the referents of their primitive names and predicates. This is known as the semantic theory of truth.
See also EPISTEMOLOGY , METAPHYSICAL REALISM , SEMANTIC HOLISM , SET -THEORETIC PARADOXE. P.Hor.