What thing die I, when I am? (sic), says Fernando Pessoa, committing a correct Grammatical mistake, in spite (or exactly because) of dominating the resources of his Language. How to understand Pessoa s grammar errancies, since they make perfect sense in his work? And, if they make sense, what Grammar these errancies follow or create that is not the traditional one? It interests us to understanding how does work in the specific field of Pessoanean language the delicate economy between tradition and anti-tradition - how does occur the relation between the necessary forces of use and abuse of Language, emphasizing Pessoa s aptitude to overcome the aporias inherent to the dualistic thought. Our Hypothesis is that Pessoa s Language points to a Grammar that, in several senses, cultivates the sign of Union: a) between error and grammatical norm or, in wider sense, between tradition and anti-tradition; b) among different sciences or fields of knowledge, melted by the great synthesis that the heteronyms embody, and being communicable through a Logics kindred to the Semiotics proposed by the thinker Charles Sanders Peirce; c) among the diverse Pessoanean poetic- perspectives chasing the same fever of Beyond.