Indexical Information

The concept of the index sign was introduced by American philosopher Charles Sanders Peirce, whose 1867 paper "On a New List of Categories," presented to the American Academy of Arts and Sciences, laid out his tripartite division of signs into icon, index, and symbol. For Peirce, an index was uniquely defined by a real, causal connection to its object. His semiotic theory was later adopted by linguistics, anthropology, and philosophy of language throughout the twentieth century.