Abstract
The third session was devoted to an outline of C.S. Peirce's philosophical semiotics, one of the original aspects of pragmatism as conceived by the Milford logician, who sometimes defined pragmatism as "the manipulation of signs to consider questions". We have outlined the major features of this vast semiotic program, emphasizing its logical and ontological roots: logical, in that, read through the spectrum of Kant, but also Boole and the medievals (Ockham and Duns Scotus), a redefinition of logic and the links between logic and grammar takes place, as well as the elaboration of an original model of analysis of the mental; ontological, in that semiotics unfolds according to a realist model, by deduction from semiotic categories, by application to the categories of thought, and according to a fundamentally triadic scheme, to the mental. We then presented the main consequences of semiotic realism (the three semiotic trichotomies: index, icon, symbol), as well as their respective links and weight in the sign-relation, before outlining the "Peircian triangle": sign, object and interpreter. Finally, we recalled the originality of this semiotic pragmatism, which attempts to articulate itself with a semiotics of the vague, and underlines both the reality of the vague (in the epistemic and semantic sense, but also in the metaphysical sense) and the vagueness of reality (inseparable, therefore, from a certain metaphysical approach to problems).
