A diagrammatic approach to Peirce’s classifications of signs 1 Priscila Farias Graduate Program in Design (SENAC-SP & UFPE) priscila.lfarias@sp.senac.br João Queiroz Graduate Studies Program on History, Philosophy, and Science Teaching (UFBA/UEFS) Dept. of Computer Engineering and Industrial Automation (DCA/FEEC/UNICAMP) queirozj@semiotics.pro.br © This paper is not for reproduction without permission of the author(s). ABSTRACT Starting from an analysis of two diagrams for 10 classes of signs designed by Peirce in 1903 and 1908 (CP 2.264 and 8.376), this paper sets forth the basis for a diagrammatic understanding of all kinds of classifications based on his triadic model of a sign. Our main argument is that it is possible to observe a common pattern in the arrangement of Peirce’s diagrams of 3-trichotomic classes, and that this pattern should be extended for the design of diagrams for any n-trichotomic classification of signs. Once this is done, it is possible to diagrammatically compare the conflicting claims done by Peircean scholars re- garding the divisions of signs into 28, and specially into 66 classes. We believe that the most important aspect of this research is the proposal of a consolidated tool for the analysis of any kind of sign structure within the context of Peirce’s classifications of signs. Keywords: Peircean semiotics, classifications of signs, diagrammatic reasoning. 1. PEIRCE’S DIAGRAMS FOR 10 CLASSES OF SIGNS In a draft of a letter to Lady Welby composed by the end of December 1908 (dated 24-28 December, L463:132-146, CP 8.342-76, EP2:483-491; we will be referring to this diagram 1. An earlier version of this paper was presented at the 7th International Congress of the International Asso- ciation for Semiotic Studies, in Dresden, 1999. Some of the results presented here have been published in Semiotica 2003, 147 (1/4); 2004, 151 (1/4).