  Conversational implicatures are usually described as being licensed by the
disobeying or flouting of some principle by the speaker in cooperative
dialogue. However, such work has failed to distinguish cases of the speaker
flouting such a principle from cases where the speaker is either deceptive or
holds a mistaken belief. In this paper, we demonstrate how the three different
cases can be distinguished in terms of the beliefs ascribed to the speaker of
the utterance. We argue that in the act of distinguishing the speaker's
intention and ascribing such beliefs, the intended inference can be made by the
hearer. This theory is implemented in ViewGen, a pre-existing belief modelling
system used in a medical counselling domain.
