The author traces a path moving alternately between two bodies of work and two forms of thought devoted to the concept of sign : Peirce and Saussure. Searching for overlaps and disparities, the perspective adopted avoids oppositions borne from confrontation as much as it does simplistic similarities. The aim of the article is thus to take stock of the conditions that have made possible the emergence of a science of signs, whether semiological or semeiotic. To this end, a limited number of theoretical themes are examined : The question of conventionality; the sign’s relation to its wordly object or “designated thing”; the conceptual space and the development of theoretical diagrams or tables; the central question of temporality. The essay concludes with Roland Barthes’s appropriation of Saussure’s project for semiology as a general science of signs. Throughout the essay the author underlines the need to maintain a certain degree of generality, seeking less to grasp abstract concepts than the imaginary of theory, a certain sensibility to things, signs and words.