Charles Sanders Peirce (1839-1914) was an American philosopher, mathematician, logician, and astronomer who was born in Cambridge, Massachusetts. His father, Benjamin Peirce, was a noted mathematician and astronomer at Harvard University. Peirce attended Harvard, where he met William James (1842-1910), who became a lifelong friend. After receiving a degree in chemistry, Peirce worked as a physicist and astronomer for the United States Coast and Geodetic Survey (1861-1891). He was also a lecturer in the philosophy of science at Harvard ((1867-72), and a lecturer in logic at Johns Hopkins University (1879-84). With James, he was a founder of the philosophy of pragmatism. He was a founder of modern semiotics, and he also made significant contributions to mathematical logic. Some aspects of his theory of semiotics are discussed in his letters to Lady Victoria Welby (1837-1912), an English philosopher whose theory of meaning he became interested in, and with whom he maintained a correspondence. He died in Milford, Pennsylvania in 1914. His best-known writings include the essays "The Fixation of Belief" (1877) and "How to Make our Ideas Clear (1878), which were originally published in Popular Science Monthly. His other works are included in the Collected Papers of Charles Peirce (8 volumes).
Peirce’s theory of signs is a theory of language and reasoning, which holds that all modes of thinking depend on the use of signs. According to Peirce, every thought is a sign, and every act of reasoning consists of the interpretation of signs. Signs function as mediators between the external world of objects and the internal world of ideas. Signs may be mental representations of objects, and objects may be known by means of perception of their signs. "Semiosis" is the process by which representations of objects function as signs. It is a process of cooperation between signs, their objects, and their "interpretants" (mental representations). "Semiotic" (the science of signs) is the study of semiosis, and it is an inquiry into the conditions that are necessary in order for representations of objects to function as signs.
Logic is described by Peirce as the science of the laws of signs, and it may be divided into three areas of study: (1) "critical logic" (the study of the relations of signs to their objects), (2) "speculative grammar" (the study of the meaning of signs), and (3) "speculative rhetoric" or "methodeutic" (the study of the relation of signs to their interpretants). Logic as semiotic is the theory of the conditions that determine the truth of signs, and it is a normative science, insofar as it is a theory of the kind of reasoning that should be employed in order to discover truth.
According to Peirce, every science is defined by the range of problems with which it is concerned, and thus every science may be described as (1) a science of discovery, (2) a theoretical science, or (3) a practical science. The sciences of discovery include mathematics, philosophy, the physical sciences, the psychological sciences, and the social sciences. The theoretical sciences include the sciences of discovery and the sciences that arrange the results of discovery or that produce the philosophy of science. The practical sciences include all the other sciences that are devoted to practical purposes (such as the vocational, industrial, and technological sciences).
Philosophy may be divided into three areas of study: (1) phenomenology (the study of phenomena as objects of perception), (2) normative science (the study of the proper relations of phenomena), and (3) metaphysics (the study of the nature of ultimate reality). Normative science may be divided into aesthetics (the science of ideals), ethics (the science of right and wrong conduct), and logic (the science of the laws of thought).1
While phenomenology is the study of phenomena in their "firstness," normative science is the study of phenomena in their "secondness," and metaphysics is the study of phenomena in their "thirdness" (CP 5.122-124).2 Firstness, secondness, and thirdness are the three "categories" or "modes of being" that give meaning to all phenomena and all objects of thought. All phenomena may be regarded as manifestations of one or more of these three categories of being.
"Meaning" is defined by Peirce as a triadic relation between a sign, an object, and an interpretant. This triadic relation is not reducible to a set of dyadic relations between a sign and an object or between an object and an interpretant (CP 1.345). Meaning is never reducible to firstness or secondness, and it can only be a "genuine" thirdness. A general meaning can always be found in genuine triadic relations, but it can never be found in "degenerate" triadic relations that have lost their thirdness.
Firstness is the mode of being of that which is without reference to any subject or object. Secondness is the mode of being of that which is itself in referring to a second subject, regardless of any third subject. Thirdness is the mode of being of that which is itself in bringing a second and third subject into relation with each other (CP 8.328)3 Thirdness brings firstness and secondness into relation with each other, and it mediates between them. Thirdness is the mode of being of signs, insofar as signs mediate between their objects and their interpretants.
Firstness may be manifested by quality, feeling, freedom, and multiplicity. Secondness may be manifested by action, reaction, causality, reality, actuality, and factuality. Thirdness may be manifested by representation, thought, continuity, order, unity, and generality.
Firstness does not have any secondness or thirdness, but secondness and thirdness each have their own firstness (CP 1.530). Firstness is the mode of being a quality but not a relation. Secondness may define dyadic relations, but thirdness may define triadic, tetradic, pentadic, and other plural relations. Firstness is the mode of being a possibility, but secondness is the mode of being a fact, and thirdness is the mode of being a sign or representation.
While secondness and thirdness may be either "genuine" or "degenerate," firstness is not susceptible to "degeneracy."4 Genuine secondness is a firstness to be second, but degenerate secondness is a secondness to firstness (CP 1. 528). Genuine thirdness is a thirdness that brings firstness and secondness into relation with each other as modes of thought. Genuine thirdness determines the nature of both firstness and secondness, so that firstness is a mode of thought as possibility, secondness is a mode of thought as actuality, and thirdness is s mode of thought as law or representation. Degenerate thirdness, on the other hand, may be a thirdness that regards secondness as a fact, rather than as a mode of thought or representation. This is the first "degree" or "grade" of degenerate thirdness. Degenerate thirdness may also be a thirdness that does not include a true secondness, but that regards firstness as representing itself to itself. This is the second "degree" or "grade" of degenerate thirdness (CP 5.70-71).
"Genuine" thirdness is a triadic relation in which an object is referred to by a sign and by an interpretant. A sign (or "representamen") is anything that denotes an object, and an object is anything that can be thought. An interpretant is the mental effect of a sign, and it is also the "signification" or "interpretation" of the sign (CP 8.184).5 The interpretant itself is a sign that may have a triadic relation with the sign that it signifies and with its own interpretant. Thus, the triadic relation between a sign, an object, and an interpretant may be repeated indefinitely (CP 2.303).6
The object of a sign, says Peirce, may be either an "immediate object" (an object as represented by a sign) or a "dynamical object" (an object as the actual cause of a sign). Similarly, the interpretant of a sign may be an "immediate interpretant" (an interpretant as represented by a sign), a "dynamical interpretant" (the interpretant that is actually produced by a sign), or a "final interpretant" (the interpretant that would be produced if the sign were properly understood).7
The "ground" of a sign is the idea or principle that determines how the sign represents its object (CP 2.228). The triadic relation between the ground, the object, and the interpretant of a sign may have its own signification, which may produce another triadic relation between the relation itself, its signfication, and the interpretation of that signification.
Within this categorial scheme, a sign may be classified as a "qualisign," a "sinsign," or a "legisign," according to its relation with its immediate object. A qualisign may be determined by its immediate object, because of internal properties of its own. A sinsign may be determined by its immediate object, because of an actual relation with that object. A legisign may be determined by its immediate object, because it is interpreted to be a sign of that object.
A qualisign is a quality that acts as a sign, a sinsign (or "token") is an actually existing thing or event that acts as a sign, and a legisign is a law that acts as a sign.8 This is the first "trichotomy of signs." A qualisign corresponds to the category of firstness, a sinsign corresponds to the category of secondness, and a legisign corresponds to the category of thirdness.
Likewise, a sign may be classified as an "icon," an "index," or a "symbol," according to its relation with its dynamical object. An icon (such as a picture, image, model, or diagram) is a sign that demonstrates the qualities of its dynamical object. An index or "seme" (such as a clock, thermometer, fuel gauge, or medical symptom) is a sign that demonstrates the influence of its dynamical object. A symbol (such as a trophy, medal, receipt, diploma, monument, word, phrase, or sentence) is a sign thst is interpreted to be a reference to its dynamical object. This is the second "trichotomy of signs." An icon corresponnds to the category of firstness, an index corresponds to the category of secondness, and a symbol corresponds to the category of thirdness.
Likewise, a sign may be classified as a "rheme," a "dicisign," or an "argument," according to its relation with its interpretant. A rheme is interpreted as a sign of qualitative possibility, a dicisign (or "dicent sign") is interpreted as a sign of actual existence, and an argument is interpreted as a sign of a law (or of a necessary truth).9 This is the third "trichotomy of signs." A rheme corresponds to the category of firstness, a dicisign corresponds to the category of secondness, and an argument correponds to the category of thirdness.
A sign may refer to more than one object or group of objects (CP 2.230).10 It may also be an element of another sign, or it may itself be composed of other signs. It may refer to a simple or complex object, and it may have a simple or complex meaning. Its meaning may also depend on its relations with other signs.
Some signs may act through other signs. For example, symbols and legisigns may act through sinsigns. Sinsigns may be "replicas" (individual examples) of symbols and legisigns.
Ten classes of signs, according to Peirce, are produced by triads of simple signs. Each of the ten classes of signs corresponds to a distinct triadic relation between the categories of firstness, secondness, and thirdness. Thus, the classification table shows that: (1) "qualisigns" correspond to the relation of firstness-firstness-firstness, (2) "iconic sinsigns" correpond to the relation of firstness-firstness-secondness, (3) "rhematic indexical sinsigns" correspond to the relation of firstness-secondness-secondness, (4) "dicent sinsigns" correspond to the relation of secondness-secondness-secondness, (5) "iconic legisigns" correspond to the relation of firstness-firstness-thirdness, (6) "rhematic indexical legisigns" correspond to the relation of firstness-secondness-thirdness, " (7) "dicent indexical legisigns" correspond to the relation of secondness-secondness-thirdness, (8) "rhematic symbols" correspond to the relation of firstness-thirdness-thirdness, (9) "dicent symbols" correspond to the relation of secondness-thirdness-thirdness, and (10) "arguments" correspond to the relation of thirdness-thirdness-thirdness.
To designate a qualisign as a rhematic iconic qualisign is redundant, says Peirce, because a qualisign can only be rhematic and iconic. Similarly, to designate an iconic sinsign as a rhematic iconic sinsign is redundant, because an iconic sinsign can only be rhematic. To designate a dicent symbol as a dicent symbol legisign is redundant, because every symbol is a legisign.
A qualisign (such as hardness, softness, warmth, coldness) is any quality that acts as a sign. An iconic sinsign (such as a photograph or a diagram) is a representation or likeness of an actually existing thing or event. A rhematic indexical sinsign (such as a cry in the street) is a sign that directs attention to the object by which it is caused. A dicent sinsign (such as a bullet hole in a wall, a scratch mark on the floor, or the motion of a weathervane) is a sign that demonstrates the influence of its object. An iconic legisign (such as a map or a diagram) is any general law or set of principles that itself demonstrates the qualities of the object to which it refers. A rhematic indexical legisign (such as a knock on the door or the ringing of a telephone) is any general law that requires each manifestation of itself to demonstrate the influence of the object to which it refers, thus attracting attention to that object. A dicent indexical legisign (such as the manner in which a person behaves or the manner in which a person communicates with others) is any general law that requires each manifestion of itself to demonstrate the influence of the object to which it refers, thus providing specific information about that object. A rhematic symbol (such as a badge, an emblem, a uniform, or a flag) is a sign that may be interpreted to refer to a general concept. A dicent symbol (such as a narrative or a description) is a sign that may be interpreted to refer to an actually existing object. An argument (such as a syllogism) is a sign of a general law or conclusion that leads to the truth.11
If every thought is a sign, then every thought may be an icon, index, or symbol. Icons and indices may be constituents of symbols. Symbols may be laws or general "types" (legisigns), and they may be general terms that are used to produce concepts. Symbols may be conventional signs that are used as signs for other signs.
1Charles Sanders Peirce, Collected Papers of Charles Sanders Peirce, Volume I, paragraph 191, 1903 (Cambridge: Harvard University Press, 1960), p. 79.
2Ibid., Volume 5, paragraphs 122-124, 1903, p. 78.
3Ibid., Volume 8, paragraph 328, 1904, p. 220.
4Ibid., Volume 5, paragraph 68, 1903, p. 47.
5Ibid., Volume 8, paragraph 184, p. 139.
6Ibid., Volume 2, paragraph 303, 1903, p. 169.
7Ibid., Volume 8, paragraph 343, 1908, p. 232.
8Ibid., Volume 2, paragraphs 244-6, 1903, p. 142.
9Ibid., Volume 2, paragraphs 250-2, 1903, p. 144.
10Ibid., Volume 2, paragraph 230, 1910, p. 136.
11Ibid., Volume 2, paragraphs 254-263, 1903, pp.147-9.
Peirce, Charles Sanders. Collected Papers of Charles Sanders Peirce. Volumes I and II. Cambridge: Harvard University Press, 1960.
Peirce, Charles Sanders. Collected Papers of Charles Sanders Peirce. Volumes V and VI. Cambridge: Harvard University Press, 1960.
Peirce, Charles Sanders. Collected Papers of Charles Sanders Peirce. Volume VIII. Cambridge: Harvard University, Press, 1958.