An Explorer upon Untrodden Ground: Peirce on Abduction

Charles Sanders Peirce (1839-1914), the founder of American pragmatism, spent a good deal of his intellectual energy and time trying to categorise kinds of reasoning, examine their properties and their mutual relations. During this intellectual adventure, he was constantly breaking new ground. One of his major achievements was that he clearly delineated a space for non-deductive, that is ampliative, reasoning. In particular, he took it to be the case that there are three basic, irreducible and indispensable forms of reasoning. Deduction and Induction are the two of them. The third is what he came to call abduction, and whose study animated most of Peirce’s intellectual life. In his fifth lecture on Pragmatism, in 1903, Peirce claimed that “abduction consists in studying facts and devising a theory to explain them” (5.145). And in the sixth lecture, he noted that “abduction is the process of forming an explanatory hypothesis” (5.171). He took abduction to be the only kind of reasoning by means of which new ideas can be introduced (cf. 5.171). In fact, he also thought that abduction is the mode of reasoning by means of which new ideas have actually been introduced: “All the ideas of science come to it by the way of Abduction” (5.145). “Abduction”, he added, “consists in studying facts and devising a theory to explain them. Its only justification is that if we are ever to understand things at all, it must be in that way (5.145).