In Pertinence et pratique (1975), Luis Prieto presented the basic tenets of his semiotic theory. Although Prieto’s views were further developed during the twenty one years between the publication of that book and his death, the main ideas presented there remained a solid base for his semiotic project. Undoubtedly, one of the main contributions of his work was the idea of pertinence, borrowed from Trubetzkoy’s phonology and developed by Prieto as a conceptual tool for analyzing semiosis as a “way of knowing”. Years later, Prieto provided the basis for linking his idea of pertinence with a theory of the “syntax of cognitive constructions” (Prieto 1988). The result of this effort can be interpreted as a theory of knowledge that departs from a semiotic realism point of view in which semiosis is described as being at the interplay between mind independent reality (material reality) and mind dependent reality (constructed via semiotic structures). The crux of the matter being that all knowledge, and thus every possibility for semiosis to occur, begins in the aesthesis of a portion of material reality. Following Prieto, the aesthesis of material reality is governed by a semiotic structure which establishes criteria of pertinence according to which some features of the material reality (e.g. a real thing) become pertinent for the subject. Since knowledge is founded upon aesthesis, Prieto concludes that pertinent features must have material features (in the sense of intrinsic qualities) as correlates. On the other hand, the pertinence principle of Prieto is always dependent upon practice: if a feature borne by an object is pertinent, it is only because such feature enables the object to be used in a given practice; i.e. practice establishes the point of view from which pertinence is established. Prieto’s model seems, at first view, highly compatible with Uexküll’s notion of umwelt, especially through the notion of funktionskreis. However, the articulation between these two approaches would provide another reading of Uexküll in which the primacy of “subjective reality” is diminished in favor of a more “realist” approach. On the other hand, to bridge the gap between these two thinkers amounts to re-think Prieto’s theory, which was originally thought as mainly anthroposemiosic, as a general theory of semiotics that could take into account the contemporary approaches of our discipline (e.g. zoo and biosemiotics). Such an articulation is seemingly absent from current discussions in our field, despite the growing interest in Uexküll, and at the same time, it also provides a way of building a general theory of semiosis from a structural point of view instead of a Peircean one. Note: If possible, I would like to share the session with other Prieto related scholars. I have proposed a thematic session on the semiotics of Luis Prieto, but I am unsure of its status. Thank you very much in any case.