Dynamics of epistemic modality and anaphora

This paper is concerned with some aspects of the semantics of modal verbs in English, in particular the phenomenon of modal subordination and the constraints on interpretation of successive modal sentences in a discourse. I propose a solution in the framework of dynamic semantics. The information state is taken to be a set of possibilities which are classiied according to the modal options extracted from the text. Modal operators are analysed as having a quasi-anaphoric relationship whereby sets of possibilities are picked out and passed on to subsequent sentences in the discourse. The system presented here is model-theoretic and depends on some reasonable assumptions about internal consistency of models. In order to reproduce the results in an imple-mentable representational framework such as DRT it will be necessary to build in an account of knowledge-based reasoning, and I discuss this problem brieey in the nal section.