Since the very beginnings of the discipline, semioticians have attempted to reconcile two traditions of thought, one originating in linguistics with Saussure, the other in the philosophical and logicist thought of Peirce. The "semiotic triangle" of Signifier - Signified - Referent (Sa - Sé - Réf) proposed by Umberto Eco (1973) is a theoretical bricolage (by its author's own admission), based on an earlier schema by Odgen and Richards (1923), but conceived using Peircian triadism and updated in the Saussurean lexicon. This triadic conception has become a vulgate, even a doxa, throughout the Humanities field. It is both a general model of how signs work and a general model of the process of meaning.Rather than engage in a deconstructive critique, this paper seeks to account for the efficiency of this schema, and for the real effort at synthesis that it reveals between the two traditions of semiotic thought. Starting with Peirce, we will recognize that the three sign regimes are involved: indexicality between Sa and Ref; iconicity between Sé and Ref; symbolicity between Sa and Sé. Continuing with Saussure, it will be shown that the notion of arbitrary sign refers to the regime of degenerate indexicality, in that it stands in unified opposition to three other notions of sign: natural (genuine index), motivated (icon) and deliberate (symbol).