Mastering semiotics means not surrendering to the evidence, being able to reverse the point of view, deconstructing and reconstructing the mechanisms on which much of what we live and think, desire or undergo - and thus everything to which, precisely, we give meaning and value - is based. This First Lesson in Semiotics outlines the assumptions of the science of languages and signification, its multiple disciplinary ancestry, and its progressive compacting toward a strong hypothesis of theory and critical analysis of different human and social cultures.