A pragmatic theory of truth is a theory of truth within the philosophies of pragmatism and pragmaticism. Pragmatic theories of truth were first posited by Charles Sanders Peirce, William James, and John Dewey. The common features of these theories are a reliance on the pragmatic maxim as a means of clarifying the meanings of difficult concepts such as truth; and an emphasis on the fact that belief, certainty, knowledge, or truth is the result of an inquiry.
Background
Pragmatic theories of truth developed from the earlier ideas of ancient philosophy, the Scholastics. Pragmatic ideas about truth are often confused with the quite distinct notions of "logic and inquiry", "judging what is true", and "truth predicates".
Logic and inquiry
In one classical formulation, truth is defined as the good of logic, where logic is a normative science, that is, an inquiry into a good or a value that seeks knowledge of it and the means to achieve it. In this view, truth cannot be discussed to much effect outside the context of inquiry, knowledge, and logic, all very broadly considered.
Most inquiries into the character of truth begin with a notion of an informative, meaningful, or significant element, the truth of whose information, meaning, or significance may be put into question and needs to be evaluated. Depending on the context, this element might be called an artefact, expression, image, impression, lyric, mark, performance, picture, sentence, sign, string, symbol, text, thought, token, utterance, word, work, and so on. Whatever the case, one has the task of judging whether the bearers of information, meaning, or significance are indeed truth-bearers. This judgment is typically expressed in the form of a specific truth predicate, whose positive application to a sign, or so on, asserts that the sign is true.
Truth predicates
Theories of truth may be described according to several dimensions of description that affect the character of the predicate "true". The truth predicates that are used in different theories may be classified by the number of things that have to be mentioned in order to assess the truth of a sign, counting the sign itself as the first thing.
In formal logic, this number is called the arity of the predicate. The kinds of truth predicates may then be subdivided according to any number of more specific characters that various theorists recognize as important.
A monadic truth predicate is one that applies to its main subject — typically a concrete representation or its abstract content — independently of reference to anything else. In this case one can say that a truthbearer is true in and of itself. A dyadic truth predicate is one that applies to its main subject only in reference to something else, a second subject. Most commonly, the auxiliary subject is either an object, an interpreter, or a language to which the representation bears some relation. A triadic truth predicate is one that applies to its main subject only in reference to a second and a third subject. For example, in a pragmatic theory of truth, one has to specify both the object of the sign, and either its interpreter or another sign called the interpretant before one can say that the sign is true of its object to its interpreting agent or sign.
Several qualifications must be kept in mind with respect to any such radically simple scheme of classification, as real practice seldom presents any pure types, and there are settings in which it is useful to speak of a theory of truth that is "almost" k-adic, or that "would be" k-adic if certain details can be abstracted away and neglected in a particular context of discussion. That said, given the generic division of truth predicates according to their arity, further species can be differentiated within each genus according to a number of more refined features.
The truth predicate of interest in a typical correspondence theory of truth tells of a relation between representations and objective states of affairs, and is therefore expressed, for the most part, by a dyadic predicate. In general terms, one says that a representation is true of an objective situation, more briefly, that a sign is true of an object. The nature of the correspondence may vary from theory to theory in this family. The correspondence can be fairly arbitrary or it can take on the character of an analogy, an icon, or a morphism, whereby a representation is rendered true of its object by the existence of corresponding elements and a similar structure.
Peirce
Very little in Peirce's thought can be understood in its proper light without understanding that he thinks all thoughts are signs, and thus, according to his theory of thought, no thought is understandable outside the context of a sign relation. Sign relations taken collectively are the subject matter of a theory of signs. So Peirce's semiotic, his theory of sign relations, is key to understanding his entire philosophy of pragmatic thinking and thought.
In his contribution to the article "Truth and Falsity and Error" for Baldwin's Dictionary of Philosophy and Psychology (1901),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. Peirce defines truth in the following way:
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 1901, see Collected Papers (CP) 5.565).
This statement emphasizes 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 occasionally 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 follows long tradition in relegating to a lower status than real definitions.
That truth is the correspondence of a representation with its object is, as Kant says, merely the nominal definition of it. Truth belongs exclusively to propositions. A proposition has a subject (or set of subjects) and a predicate. The subject is a sign; the predicate is a sign; and the proposition is a sign that the predicate is a sign of that of which the subject is a sign. If it be so, it is true. But what does this correspondence or reference of the sign, to its object, consist in? (Peirce 1906, CP 5.553).
Here Peirce makes a statement that is decisive for understanding the relationship between his pragmatic definition of truth and any theory of truth that leaves it solely and simply a matter of representations corresponding with their objects. Peirce, like Kant before him, recognizes Aristotle's distinction between a nominal definition, a definition in name only, and a real definition, one that states the function of the concept, the reason for conceiving it, and so indicates the essence, the underlying substance of its object. This tells us the sense in which Peirce entertained a correspondence theory of truth, namely, a purely nominal sense. To get beneath the superficiality of the nominal definition it is necessary to analyze the notion of correspondence in greater depth.
In preparing for this task, Peirce makes use of an allegorical story, omitted here, the moral of which is that there is no use seeking a conception of truth that we cannot conceive ourselves being able to capture in a humanly conceivable concept. So we might as well proceed on the assumption that we have a real hope of comprehending the answer, of being able to "handle the truth" when the time comes. Bearing that in mind, the problem of defining truth reduces to the following form:
Now thought is of the nature of a sign. In that case, then, if we can find out the right method of thinking and can follow it out — the right method of transforming signs — then truth can be nothing more nor less than the last result to which the following out of this method would ultimately carry us. In that case, that to which the representation should conform, is itself something in the nature of a representation, or sign — something noumenal, intelligible, conceivable, and utterly unlike a thing-in-itself. (Peirce 1906, CP 5.553).
Peirce's theory of truth depends on two other, intimately related subject matters, his theory of sign relations and his theory of inquiry. Inquiry is a special case of semiosis, a process that transforms signs into signs while maintaining a specific relationship to an object, which object may be located outside the trajectory of signs or else be found at the end of it. Inquiry includes all forms of belief revision and logical inference, including scientific method, what Peirce here means by "the right method of transforming signs". A sign-to-sign transaction relating to an object is a transaction that involves three parties, or a relation that involves three roles. This is called a ternary or triadic relation in logic. Consequently, pragmatic theories of truth are largely expressed in terms of triadic truth predicates.
The statement above tells us one more thing: Peirce, having started out in accord with Kant, is here giving notice that he is parting ways with the Kantian idea that the ultimate object of a representation is an unknowable thing-in-itself. Peirce would say that the object is knowable, in fact, it is known in the form of its representation, however imperfectly or partially.
Reality and truth are coordinate concepts in pragmatic thinking, each being defined in relation to the other, and both together as they participate in the time evolution of inquiry. Inquiry is not a disembodied process, nor the occupation of a singular individual, but the common life of an unbounded community.
The real, then, is that which, sooner or later, information and reasoning would finally result in, and which is therefore independent of the vagaries of me and you. Thus, the very origin of the conception of reality shows that this conception essentially involves the notion of a COMMUNITY, without definite limits, and capable of a definite increase of knowledge. (Peirce 1868, CP 5.311).
Different minds may set out with the most antagonistic views, but the progress of investigation carries them by a force outside of themselves to one and the same conclusion. This activity of thought by which we are carried, not where we wish, but to a foreordained goal, is like the operation of destiny. No modification of the point of view taken, no selection of other facts for study, no natural bent of mind even, can enable a man to escape the predestinate opinion. This great law is embodied in the conception of truth and reality. The opinion which is fated to be ultimately agreed to by all who investigate, is what we mean by the truth, and the object represented in this opinion is the real. That is the way I would explain reality. (Peirce 1878, CP 5.407).
James