Within a general theory of communicative contexts and their influence on the structures, production and comprehension of discourse, this article focuses on the crucial, but often ignored, role of the knowledge of speakers about the knowledge of the recipients, earlier studied as ‘common ground’. For communicative contexts to influence the structures of discourse, it is assumed that participants must have a mental model of that situation, including this specific knowledge controlling all epistemic aspects of discourse. Such knowledge must be inferred from previous (parts of) discourse, prior discourse and communication or an ongoing analysis of the communicative situation. A detailed analysis of a speech of former Prime Minister of the UK, David Cameron, on refugees shows that the general epistemic conditions of appropriate assertions in such speeches require a much more sophisticated theoretical and analytical approach than in classical pragmatics.