Starting from the formalist/intuitionist debate about ideality of negation in the first third of the XXth century, I will investigate the
functional approaches of negation as a unary logical connective, leading to the contemporary interactional approaches of negation as a protological binary relation between processus. In these times where logical pluralism has become logical plethorism, I will conclude about the foundational rôle of this conception of negation for logic.