Charles S(anders) (1839–1914), American philosopher, scientist, and mathematician, the founder of the philosophical movement called pragmatism. Peirce was born in Cambridge, Massachusetts, the second son of Benjamin Peirce, who was professor of mathematics and astronomy at Harvard and one of America’s leading mathematicians. Charles Peirce studied at Harvard University and in 1863 received a degree in chemistry. In 1861 he began work with the U.S. Coast and Geodetic Survey, and remained in this service for thirty years. Simultaneously with his professional career as a scientist, Peirce worked in logic and philosophy. He lectured on philosophy and logic at various universities and institutes, but was never able to obtain a permanent academic position as a teacher of philosophy. In 1887 he retired to Milford, Pennsylvania, and devoted the rest of his life to philosophical work. He earned a meager income from occasional lectures and by writing articles for periodicals and dictionaries. He spent his last years in extreme poverty and ill health. Pragmatism. Peirce formulated the basic principles of pragmatism in two articles, ‘The Fixation of Belief’ and ‘How to Make Our Ideas Clear’ (1877–78). The title of the latter paper refers to Descartes’s doctrine of clear and distinct ideas. According to Peirce, the criteria of clarity and distinctness must be supplemented by a third condition of meaningfulness, which states that the meaning of a proposition or an ‘intellectual conception’ lies in its ‘practical consequences.’ In his paper ‘Pragmatism’ (1905) he formulated the ‘Principle of Pragmatism’ or the ‘Pragmatic Maxim’ as follows: In order to ascertain the meaning of an intellectual conception we should consider what practical consequences might conceivably result by necessity from the truth of that conception; and the sum of these consequences will constitute the entire meaning of the conception. By ‘practical consequences’ Peirce means conditional propositions of the form ‘if p, then q’, where the antecedent describes some action or experimental condition, and the consequent describes an observable phenomenon or a ‘sensible effect.’ According to the Pragmatic Maxim, the meaning of a proposition (or of an ‘intellectual conception’) can be expressed as a conjunction of such ‘practical conditionals.’
The Pragmatic Maxim might be criticized on the ground that many meaningful sentences (e.g., theoretical hypotheses) do not entail any ‘practical consequences’ in themselves, but only in conjunction with other hypotheses. Peirce anticipated this objection by observing that ‘the maxim of pragmatism is that a conception can have no logical effect or import differing from that of a second conception except so far as, taken in connection with other conceptions and intentions, it might conceivably modify our practical conduct differently from that of the second conception’ (‘Pragmatism and Abduction,’ 1903).
Theory of inquiry and philosophy of science. Peirce adopted Bain’s definition of belief as ‘that which a man is prepared to act upon.’ Belief guides action, and as a content of belief a proposition can be regarded as a maxim of conduct. According to Peirce, belief is a satisfactory and desirable state, whereas the opposite of belief, the state of doubt, is an unsatisfactory state. The starting point of inquiry is usually some surprising phenomenon that is inconsistent with one’s previously accepted beliefs, and that therefore creates a state of doubt. The purpose of inquiry is the replacement of this state by that of belief: ‘the sole aim of inquiry is the settlement of opinion.’ A successful inquiry leads to stable opinion, a state of belief that need not later be given up. Peirce regarded the ultimate stability of opinion as a criterion of truth and reality: ‘the rea. . . is that which, sooner or later, information and reasoning would finally result in, and which is therefore independent of the vagaries of you and me.’ He accepted, however, an objectivist conception of truth and reality: the defining characteristic of reality is its independence of the opinions of individual persons.
In ‘The Fixation of Belief’ Peirce argued that the scientific method, a method in which we let our beliefs be determined by external reality, ‘by something upon which our thinking has no effect,’ is the best way of settling opinion. Much of his philosophical work was devoted to the analysis of the various forms of inference and argument employed in science. He studied the concept of probability and probabilistic reasoning in science, criticized the subjectivist view of probability, and adopted an objectivist conception, according to which probability can be defined as a relative frequency in the long run. Peirce distinguished between three main types of inference, which correspond to three stages of inquiry: (i) abduction, a tentative acceptance of an explanatory hypothesis which, if true, would make the phenomenon under investigation intelligible; (ii) deduction, the derivation of testable consequences from the explanatory hypothesis; and (iii) induction, the evaluation of the hypothesis in the light of these consequences. He called this method of inquiry the inductive method; in the contemporary philosophy of science it is usually called the hypothetico-deductive method. According to Peirce, the scientific method can be viewed as an application of the pragmatic maxim: the testable consequences derived from an explanatory hypothesis constitute its concrete ‘meaning’ in the sense of the Pragmatic Maxim. Thus the Maxim determines the admissibility of a hypothesis as a possible (meaningful) explanation. According to Pierce, inquiry is always dependent on beliefs that are not subject to doubt at the time of the inquiry, but such beliefs might be questioned on some other occasion. Our knowledge does not rest on indubitable ‘first premises,’ but all beliefs are dependent on other beliefs. According to Peirce’s doctrine of fallibilism, the conclusions of science are always tentative. The rationality of the scientific method does not depend on the certainty of its conclusions, but on its self-corrective character: by continued application of the method science can detect and correct its own mistakes, and thus eventually lead to the discovery of truth. Logic, the theory of signs, and the philosophy of language. In ‘The Logic of Relatives,’ published in 1883 in a collection of papers by himself and his students at the Johns Hopkins University (Studies in Logic by Members of the Johns Hopkins University), Peirce formalized relational statements by using subscript indices for individuals (individual variables), and construed the quantifiers ‘some’ and ‘every’ as variable binding operators; thus Peirce can be regarded (together with the German logician Frege) as one of the founders of quantification theory (predicate logic). In his paper ‘On the Algebra of Logic – A Contribution to the Philosophy of Notation’ (1885) he interpreted propositional logic as a calculus of truth-values, and defined (logically) necessary truth (in propositional logic) as truth for all truth-value assignments to sentential letters. He studied the logic of modalities and in the 1890s he invented a system of logical graphs (called ‘existential graphs’), based on a diagrammatic representation of propositions, in which he anticipated some basic ideas of the possible worlds semantics of modal logic. Peirce’s letters and notebooks contain significant logical and philosophical insights. For example, he examined three-valued truth tables (‘Triadic Logic’), and discovered (in 1886) the possibility of representing the truth-functional connectives of propositional logic by electrical switching circuits.
Peirce regarded logic as a part of a more general area of inquiry, the theory of signs, which he also called semeiotic (nowadays usually spelled ‘semiotic(s)’). According to Peirce, sign relations are triadic, involving the sign itself, its object (or what the sign stands for), and an interpretant which determines how the sign represents the object; the interpretant can be regarded as the meaning of the sign. The interpretant of a sign is another sign which in turn has its own interpretant (or interpretants); such a sequence of interpretants ends in an ‘ultimate logical interpretant,’ which is ‘a change of habit of conduct.’
On the basis of the triadic character of the sign relation Peirce distinguished three divisions of signs. These divisions were based on (i) the character of the sign itself, (ii) the relation between the sign and its object, and (iii) the way in which the interpretant represents the object. These divisions reflect Peirce’s system of three fundamental ontological categories, which he termed Quality or Firstness, Relation or Secondness, and Representation or Thirdness. Thus, according to the first division, a sign can be (a) a qualisign, a mere quality or appearance (a First); (b) a sinsign or token, an individual object, or event (a Second); or (c) a legisign or a general type (a Third). Secondly, signs can be divided into icons, indices, and symbols on the basis of their relations to their objects: an icon refers to an object on the basis of its similarity to the object (in some respect); an index stands in a dynamic or causal relation to its object; whereas a symbol functions as a sign of an object by virtue of a rule or habit of interpretation. Peirce’s third division divides signs into rhemes (predicative signs), propositional signs (propositions), and arguments. Some of the concepts and distinctions introduced by Peirce, e.g., the distinction between ‘types’ and ‘tokens’ and the division of signs into ‘icons,’ ‘indices,’ and ‘symbols,’ have become part of the standard conceptual repertoire of philosophy and semiotics. In his philosophy of language Peirce made a distinction between a proposition and an assertion, and studied the logical character of assertive speech acts. Metaphysics. In spite of his critical attitude toward traditional metaphysics, Peirce believed that metaphysical questions can be discussed in a meaningful way. According to Peirce, metaphysics studies the most general traits of reality, and ‘kinds of phenomena with which every man’s experience is so saturated that he usually pays no particular attention to them.’ The basic categories