Some Issues about the Portuguese Modals dever and poder

Abstract. This paper is about some Portuguese modals, mainly poder 'may/can' and dever 'must/should'. After a short description of these modals, I concentrate on their relation to negation. The main objective is to establish a scale for them, based on the three-layered scalar square proposed by van der Auwera (1996). It is shown that the verb poder expresses in many cases a two-sided possibility, and that dever is not a necessity operator in any of its interpretations.