Icons, Interrogations, and Graphs: On Peirce’s Integrated Notion of Abduction

Peirce’s semiotic characterization of abductive reasoning in the 1903 Syllabus and in its drafts is related to the interrogative mood of the conclusion of abductive reasoning, both in the light of the Syllabus and in that of Peirce’s post-1903 analysis of abduction and speculative grammar. The relevant pages of the Syllabus also present two non-standard logical graphs that are new. We surmise their intended meaning and explain connections to the interrogative construal of abductive reasoning. These three aspects of abduction—its semiotic, speech-act theoretical, and graphical dimensions—are all epitomized on one single page of the Syllabus and its alternative drafts.