. One of the most powerful accounts of the necessary connection between law and morality grounded on the openness of communication is provided by Robert Alexy, who builds a discourse theory of law on the basis of Habermas’ theory of general practical discourse. In this article I argue that the thesis based on the openness of legal discourse is problematic in that it does not provide a convincing account of the differentiation of legal discourse from other practical discourses. I offer (...) an understanding of the institutionalisation of legal discourse as the tacit commitment of the participants to their shared normative experience and in particular in: 1) the possibility of containing normative force in space, 2) the possibility of transforming word into deed, 3) the possibility of grasping and controlling time and 4) the possibility of transforming deed into word. That commitment of participants in legal discourse is revealed as a set of fundamental assumptions embedded in all legal utterances, which provide the necessary bedrock that makes communication possible. It also provides a basis for the institution of legal discourse, to the effect that their problematisation signifies a departure from the latter. (shrink)