 How to proceed? From the fact that no terminating action was mentioned, we want to conclude that no terminating event occurred. To do so, we have to strengthen the assumptions of the theory in a way that only those events are assumed to occur which have been explicitly stated in the discourse. The discourse model should be minimal, linking discourse understanding intimately to closed world reasoning. It is important to note that this strategy forces reasoning to be non-monotonic: adding further premises to a theory can make inferences invalid that were valid before (see the entry on  non-monotonic logic). 